An HST Survey of Protostellar Outflow Cavities: Does Feedback Clear Envelopes?
Nolan M. Habel, S. Thomas Megeath, Joseph Jon Booker, William J. Fischer, Marina Kounkel, Charles Poteet, Elise Furlan, Amelia Stutz, P. Manoj, John J. Tobin, Zsofia Nagy, Riwaj Pokhrel, Dan Watson
DDraft version February 16, 2021
Preprint typeset using L A TEX style AASTeX6 v. 1.0 AN HST
SURVEY OF PROTOSTELLAR OUTFLOW CAVITIES: DOES FEEDBACK CLEAR ENVELOPES?
Nolan M. Habel , S. Thomas Megeath , Joseph Jon Booker , William J. Fischer , Marina Kounkel , CharlesPoteet , Elise Furlan , Amelia Stutz , P. Manoj , John J. Tobin , Zsofia Nagy , Riwaj Pokhrel , DanWatson Ritter Astrophysical Research Center, Department of Physics and Astronomy, University of Toledo, 2801 W. Bancroft Street, Toledo, OH43606, USA Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA Department of Physics and Astronomy, Western Washington University, 516 High st., Bellingham, WA, 98225 NASA Exoplanet Science Institute, Caltech/IPAC, Mail Code 100-22, 1200 E. California Blvd., Pasadena, CA 91125, USA Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany Departmento de Astronomía, Facultad Ciencias Físicas y Matemáticas, Universidad de Concepción, Av. Esteban Iturra s/n Barro Univer-sitario, Casilla 160-C, Concepción, Chile Department of Astronomy and Astrophysics, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400005, India National Radio Astronomy Observatory, 520 Edgemont Rd., Charlottesville,VA 22903, USA Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, H-1121 Budapest, Konkoly Thege út 15–17, Hungary Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627, USA
ABSTRACTWe study protostellar envelope and outflow evolution using Hubble Space Telescope NICMOS orWFC3 images of 304 protostars in the Orion Molecular clouds. These near-IR images resolve struc-tures in the envelopes delineated by the scattered light of the central protostars with 80 AU resolutionand they complement the 1 . .
60 µm morphologies, we classify the protostarsinto five categories: non-detections, point sources without nebulosity, bipolar cavity sources, unipo-lar cavity sources, and irregulars. We find point sources without associated nebulosity are the mostnumerous, and show through monochromatic Monte Carlo radiative transfer modeling that this mor-phology occurs when protostars are observed at low inclinations or have low envelope densities. Wealso find that the morphology is correlated with the SED-determined evolutionary class with Class0 protostars more likely to be non-detections, Class I protostars to show cavities and flat-spectrumprotostars to be point sources. Using an edge detection algorithm to trace the projected edges of thecavities, we fit power-laws to the resulting cavity shapes, thereby measuring the cavity half-openingangles and power-law exponents. We find no evidence for the growth of outflow cavities as protostarsevolve through the Class I protostar phase, in contradiction with previous studies of smaller samples.We conclude that the decline of mass infall with time cannot be explained by the progressive clearingof envelopes by growing outflow cavities. Furthermore, the low star formation efficiency inferred formolecular cores cannot be explained by envelope clearing alone. INTRODUCTIONLow mass protostars are characterized by a rapid evo-lution, with the accretion of the stellar mass, the forma-tion of disks and potentially the initiation of planet for-mation occurring within 0 . a r X i v : . [ a s t r o - ph . GA ] F e b This evolution is accompanied by a rapid change inthe shape of the SEDs produced by the reprocessingand scattering of radiative energy in the evolving disksand envelopes (Furlan et al. 2016). Since the centralprotostar is deeply embedded in its envelope, the effec-tive temperatures and photospheric luminosities of pro-tostars typically cannot be measured directly. In mostcases, unlike pre-main sequence stars, they cannot bereliably placed on HR diagrams and compared to evolu-tionary tracks to estimate masses and ages. Instead, theevolution of protostars is largely inferred from the shapeof their SEDs. This evolution is typically measured bysorting protostars into bulk evolutionary classes basedon the percentage of luminosity radiated in the sub-millimeter, their near- to mid-infrared spectral index or T bol , the bolometeric temperature (e.g., Adams & Shu1985, Myers & Ladd 1993, Andre et al. 1993, Stutz et al.2013, Dunham et al. 2014, Furlan et al. 2016). The ob-served sequence of evolutionary classes, Class 0, Class Iand flat-spectrum, shows the peak of the SED shiftingfrom the far-infrared to the mid-infrared and the SEDflattening as the protostars evolve and the envelopes dis-sipate (e.g., Furlan et al. 2016). Class II objects canbe identified by their decreasing near- to mid-IR SEDslopes and are primarily pre-main sequence stars withdisks that have exited the protostellar phase.Due to the flattening of envelopes by rotation and theclearing of cavities in the envelopes by outflows, the lu-minosity of the protostars is not radiated isotropically,but is preferentially beamed along the rotation axis ofthe protostars. The resulting SEDs depend on the in-clination of the protostars, and the effects of inclinationon the SEDs are difficult to disentangle from those dueto evolution (Kenyon et al. 1993, Whitney et al. 2003).To circumvent this degeneracy, Whitney & Hartmann(1993) and Robitaille et al. (2007) proposed a set ofevolutionary stages which are dependent on the physicalproperties of the envelopes and not inclination; however,it is often difficult to reliably infer the stage of a proto-star from the obseved SED alone. Nevertheless, takinginto account the uncertainties due to inclination, Furlanet al. (2016) demonstrate that the observed SEDs of thedistinct evolutionary classes require the dissipation ofthe envelope, with the density of the envelope gas (asinferred by model fits to the SEDs) dropping by a fac-tor of 50 between the Class 0 and flat-spectrum phases.This shows that the envelopes decrease in density dra-matically during the Class I phase.Although SEDs are currently the primary informa-tion we have on large samples of protostars, imaging atmillimeter, submillimeter and near-infrared wavelengthscan be used to study protostellar evolution by resolvingstructures in the envelope that may change as protostarsevolve (e.g., Arce & Sargent 2006). HST near-infrared images of protostars resolve structures seen directly inlight scattered by dust grains in an envelope or in sil-houette against the scattered light, placing constraintson the envelopes and disks that are complementary tothose inferred from SEDs.
HST imaging of protostarsby Padgett et al. (1999), Allen et al. (2002), Terebeyet al. (2006) and Fischer et al. (2014) show outflow cav-ities illuminated in scattered light, edge-on disks seenin absorption and shadows cast into the envelopes byflared disks.Of particular interest is the role of feedback from out-flows in driving the evolution of protostars by clear-ing the envelope and halting infall. SED-based mea-surements cannot reliably constrain outflow cavity sizes(Furlan et al. 2016); hence, studies of the growth of out-flow cavities must rely on observations that spatiallyresolve structures in envelopes. The CO observationsof nine Class 0, I and II sources by Arce & Sargent(2006) showed a widening in outflow size with evolu-tionary class. Bolstering their sample by nine sources inthe literature, they found evidence that outflow cavitysizes increase progressively as protostars evolve. Tobinet al. (2007) and Seale & Looney (2008) used
Spitzer
IRAC images of protostar outflow cavities illuminatedin scattered light to study the growth of cavities, andthe latter authors found some evidence of outflow cavitygrowth with evolution, although with significant scatter.These studies suggest that feedback from outflowsplay a significant role in the decrease or halting of in-fall and accretion. Although accretion from the disk cancontinue after infall stops, the resulting increase in massis small compared to the stellar mass. By reducing orhalting infall, feedback can also play an important rolein the star formation efficiency inferred from the coremass function. In particular, the mass function of coresidentified in sub-mm measurements can reproduce theinitial mass function if each core forms a star with astar formation efficiency (defined by the stellar to initialcore mass) of 30–40 % (Alves et al. 2007, Könyves et al.2015). Furthermore, simulations of protostars includingfeedback can produce star formation efficiencies of 50 %or lower (Machida & Hosokawa 2013, Machida & Mat-sumoto 2012, Hansen et al. 2012, Offner & Arce 2014,Offner & Chaban 2017).There are difficulties, however, in explaining the lowstar formation efficiency with feedback alone. Singledish radio observations suggest that outflows may carrytoo little mass to clear out the envelope in 0 . HST survey of protostars to date. This survey focuses onthe sample of protostars targeted by the Herschel OrionProtostar Survey, or HOPS. The protostars were iden-tified using combined 2MASS and
Spitzer photometryfrom the
Spitzer
Orion Survey (Megeath et al. 2012,2016) and observed with Herschel and APEX to obtainwell sampled 1 . HST survey examined 304 of these sources,(enumerated in Table B1), using initially NICMOS at1.60 and 2 .
05 µm, and then after the failure of NIC-MOS, WFC3 at 1 .
60 µm. A search for binary systemsusing these data was published by Kounkel et al. (2016).The morphologies of outflow cavities carved by theoutflows can be seen by mapping the location of the cav-ity wall in scattered light. The volumes of the cavitiescarved by outflows can then be directly measured. Themechanism for creating these cavities, whether by jetprecession, wide-angled winds or jet entrainment (Raga& Cabrit 1993, Lee et al. 2001, Matzner & McKee 1999,Ybarra et al. 2006), is still debated. Independent ofthe underlying mechanism, the scattered-light cavitiesprovide a direct measurement of the cleared gas withthe 80 AU (0 . ) resolution of HST . These are usedin this work to estimate the fraction of the volumecleared, which provides an estimate of the fraction ofmass cleared.In Section 2, we discuss the observations used in thispaper. We make use of radiative transfer modeling, de-scribed in Section 3, to understand the morphologies ofthe observed cavities and to calibrate the relationshipbetween the scattered-light distributions and the cavityproperties. In Section 4, we present the morphologiesof the observed protostar and our analysis of the cavitysizes. Finally, we discuss the implications for protostel-lar evolution in Section 5. Images of the protostars inour sample are shown in Appendix A. HST
OBSERVATIONS OF THE SAMPLEThe
Hubble Space Telescope observations were assem-bled from two GO programs and a snapshot program.The bulk of the sample was observed in program GO11548. The Near Infrared Camera and Multi-ObjectSpectrometer’s (NICMOS) F205W and F160W filters were used for a total of 87 orbits in August and Septem-ber of 2008 to image 92 objects in the HOPS catalog,before the failure of the cryocooler of NICMOS. Afterthe June 2009 deployment of the Wide Field Camera 3(WFC3), 126 orbits were used between August 2009 andDecember 2010 to observe 237 HOPS objects with theF160W filter. The observation and reduction of thesedata is described in Kounkel et al. (2016). A subse-quent program using WFC3, SNAP 14181, was designedto target multiple star forming regions within 500 pc.It completed observations during 114 orbits betweenDecember 2015 and September 2017, 10 of which im-aged 13 objects in the Orion Molecular Clouds. A finalWFC3 study, program GO 14695, targeted four objectsin Orion with weak 24 µ m fluxes atypical of protostars.These observations were conducted in September 2016with four orbits. For these final two programs we usedthe standard data products produced from the calwf3 data reduction pipeline which were then combined with AstroDrizzle from the
DrizzlePac package using adrop size of 1 onto a pixel scale of 0 . .The NICMOS observations used the NIC2 camera,which has a 0 . pixel size and resolution of 0 . .Integration times were 1215 . . . . . . an-gular resolution and a pixel size of 0 . . In this workwe adopt a distance to Orion of 420 parsecs for con-sistency with Furlan et al. (2016). This is within therange of distances found in Kounkel et al. (2018) andGroßschedl et al. (2018) through APOGEE and Gaia measurements. At this distance, both NICMOS andWFC3 resolve structures down to 80 AU scales.Nine images taken with NICMOS are excluded fromthis analysis due to the lack of guide star tracking; thesecontain HOPS 46, 47, 134, 139, 149, 227, 250, 271 and276. Three WFC3 images, containing HOPS 293, 330and 336, were also excluded due to what appear to betracking failures. One additional WFC3 observation wasexcluded due to an apparent pointing error with its tar-get object, HOPS 100, only partially appearing on theedge of the frame. Three images where only one guidestar was used, those containing HOPS 10, 177, 316 and358, may suffer from a small amount of rotation duringthe exposure, although this is not apparent in the data.These are included in our program. Twenty-seven ofthe HOPS targets were imaged by both NICMOS andWFC3 due to their proximity to other protostars. Ofthese sources, only HOPS 250 showed a clear differencebetween the two observations due to the tracking failure.Some of the HOPS targets were classified as poten-tial extragalactic contamination by Furlan et al. (2016)based on the presence of PAH features in their
Spitzer
Radial Distance ρ (AU) D i s t a n ce a b o v e D i s k z ( AU ) ◦ z = A | ρ | n Figure 1 . The definition of the cavity half-opening angleused in this paper and in the
HO-CHUNK code. The circularregion is the outer radius of the envelope of the protostar inthese models, set to 8000 AU; the parabolic ( n = 2) black lineis the adopted boundary of the evacuated outflow cavity. Thecentral protostar is located at the origin. The cavity half-opening angle is defined by the angle between the dotted lineintersecting the cavity at 8000 AU above the normal to thedisk and the polar axis. IRS spectrum, lack of silicate absorption at 10 µm, orthe shape of the mid-infrared continuum (see appendixof Furlan et al. 2016). The
HST observations provide anindependent means for separating galaxies from proto-stars. Only one source, HOPS 339, is conclusively deter-mined by its morphology to be a galaxy and is omittedfrom the table in the appendix of this work (Table B1).The WFC3 image of this source is shown in Appendix E.Conversely, we add back into our sample and assign aclass to HOPS 48, 67, and 301. These have morphologiesin WFC3 imaging indicative of protostellar cavities. Thenature of the remaining potentially extragalactic sourcescould not be clarified through WFC3 imaging. In pro-gram GO 14695, two of the four targeted sources werefound not to be protostars; one was a galaxy and one anoutflow knot; neither of these has a HOPS number (seeAppendix E). In total, we imaged 304 objects in oursample. We note that 7 of these were determined to beClass II objects by their SEDs in Furlan et al. (2016).Since these sources are in the HOPS sample and mayhave residual envelopes, we keep them in the analysis.We typically use “protostars” to refer to this entire sam-ple. In addition, we serendipitously observed two ClassII sources with nebulosity in our images (Kounkel et al.2016). We describe these objects in Appendix D. MODEL GRIDIn order to quantify the shape of the observed cav-ities, we used a monochromatic Monte Carlo radiative transfer code,
HO-CHUNK.ttsscat.20090521 (based onWhitney & Hartmann 1992, 1993). With this code, wesimulated 1 .
60 µm images of a half solar mass star sur-rounded by a flared disk, with a power-law radial densityand scale height and an envelope, following the Tere-bey, Shu, and Cassen (TSC) model described in Terebeyet al. (1984), (see also Ulrich 1976, Cassen & Moosman1981). We examined six envelope densities (each corre-sponding to a different mass infall rate in Table 1), fivecavity half-opening angles (see Figure 1 for the defini-tion), five disk sizes, four disk masses, two variations ondisk flaring and ten inclinations. Table 1 shows the pa-rameters used in our model grid. All models adopt anidentical photon flux from the central star and assumefully-evacuated cavities containing no material. Thesemodel images were convolved with the
HST
WFC3IRpoint spread function for the F160W filter. In this pa-per, we are primarily interested in variations in the ob-served near-IR morphology due to changes in envelopedensity, cavity half-opening angle, and inclination.In these models, the mass infall rate is used as a pa-rameter to control the densities of the envelopes. Theinfall rate is combined with an adopted central stellarmass of 0 . (cid:12) to scale the envelope density using Eqn.3 from Kenyon et al. (1993). See Furlan et al. (2016) forfurther discussion on this scaling.The disk and envelope dust opacities are from a modelby Ormel et al. (2011) that adopts a 2:1 mixture ofice-coated silicates and bare graphite grains, where thedepth of the ice coating is 10 % of the particle radius.The particles are subjected to time-dependent coagula-tion; we choose a coagulation time of 0 . n = 2) shown in Fig-ure 1 for outflow/envelope boundary in our models. InSection 4.2, we relax this constraint and use the power-law fit z = A | ρ | n (1)where the resulting power-law index, n , may be 1 orgreater. For a given power-law, the cavity half-openingangle depends on the adopted outer radius of the en-velope; only for the case of a conical cavity ( n = 1) isthe half-opening angle independent of the adopted outerradius.Examples of models from the grid are shown in Fig- Table 1 . Parameters used in the model grid described in Section 3.
Parameter Value(s) R star : Radius of star 2 .
09 R (cid:12)
Temperature of central star 4 . × KMass of central star 0 . (cid:12) Minimum disk radius 7 .
00 R star
Disk Scale height at R star a .
018 AUMaximum envelope radius 8000 AUMinimum envelope radius 6 .
85 R star
Degree of polynomial shape of cavities 2 . ρ = 0 0 R star Density of the cavity 0 g cm − Ambient cloud density 0 g cm − Minimum radius of outflow 0 . . . .
01 and 0 .
05 M (cid:12) α disk : Radial exponent in disk density law 2 .
125 and 2 . β disk : Vertical exponent in disk density law α disk − b × − , 5 × − , 1 × − , 5 × − , 1 × − and 5 × − M (cid:12) yr − Half-opening angle of inner cavity wall 5°, 15°, 25°, 35° and 45°Angle of inclination measured from polar axis 1°, 10°, 20°, 30°, 40°, 50°, 60°, 70°, 80° and 90° a h of Whitney & Hartmann (1992, eqn 5) b See Whitney & Hartmann (1993, eqn 3) ure 2, which displays the effect of differing inclinationsand cavity half-opening angles. Several model param-eters, such as the radius and temperature of the cen-tral protostar or the presence of hot spots, are not con-strained by either the SEDs or the near-infrared images.The surface brightness found in an image depends onthe monochromatic luminosity of the protostar (whichin turn depends on the temperature, radius and presenceof hot spots), but the morphology of the image dependsprimarily on envelope density, outflow cavity shape andinclination. The rest of our model parameters are cho-sen to cover a range of physical parameters observed inthe fitting done by Furlan et al. (2016). This allows usto compare in Appendix G the values for the parametersdetermined by the fits to the SEDs and those determinedfrom the near infrared images.As shown by the models, the observed morphologiesof the cavities trace the light scattered at a discontinuityin the dust density; in this case, the discontinuity is theboundary of a cleared cavity. If the protostar is seenedge-on, both cavities carved by the bipolar outflow areapparent. For these edge-on cases, a dust disk obscuresthe scattered light creating a dust lane (Figure 2). If the system is inclined such that the extinction toward the farcavity is significantly higher than that toward the nearerone, a bowl-shaped unipolar structure is seen due to theobscuration of the more distant cavity. The envelopeitself can be directly illuminated if the density is lowenough for near-infrared photons to penetrate past thecavity walls and scatter off grains deep in the envelope.In these cases, the disk can cast shadows in the envelopewhich are also apparent for edge-on inclinations.To compare our cavities to those measured in otheranalyses that adopt different models for their shapes(e.g. this work, Furlan et al. 2016, Arce & Sargent2006), we will determine the fraction of the envelopevolume within the cavities. This is a measure of theamount of gas cleared by the outflow. The volume ofthe cavities in these models depends only on the power-law exponent n , the half-opening angle θ and the outerenvelope radius R max (Figure 1). In Figure 3, we showthe dependence of the fraction of the envelope volumecleared by the cavity on the cavity half-opening angleand the cavity exponent.An alternative metric for characterizing cavity sizesis the fraction of the envelope mass cleared by the out- Pole-On
20 30 40 50 60 70 80 Edge-On
Inclination From Pole ( ◦ ) C a v i t y H a l f - O p e n i n g A n g l e ( ◦ ) Figure 2 . A selection of models from the grid used in this work, showing variations in the observed scattered-light morphologiesfrom models with a mass infall rate of 5 × − M (cid:12) yr − . Note that the contrast between the cavity and the central point sourceis highest when observed at an inclination greater than the half-opening angle. Each model is shown with an approximately8000 by 8000 AU field of view. Cavity Half-Opening Angle ( ) V o l u m e F r a c t i o n C l e a r e d n=2n=1.5n=1 Figure 3 . The dependence of cleared cavity volume as afraction of total envelope volume on cavity exponent andhalf-opening angle. The cavities are carved in a sphericallysymmetric envelope with an outer radius of 8000 AU. flows, i.e. the fraction of mass that would be found inan initially spherical symmetric core with a ρ − . densitylaw and an outer radius of 8000 AU. We compare thevolume and mass fraction cleared in Figure 4. We findthe fraction of the mass cleared can be up to 9 % morethan the volume cleared, and that the volume cleared isa lower limit to the mass cleared. We note that this is aninstantaneous mass fraction of the current envelope, and it will differ from the total fraction of the envelope massentrained and ejected by the outflow over the history ofa protostellar collapse. Furthermore, it does not includethe mass launched and ejected from the system by diskwinds, X-winds, or accretion-driven stellar winds (e.g.Watson et al. 2016). RESULTSIn this section, we classify the protostars on the ba-sis of their 1 .
60 µm morphologies in the
HST images.We then examine how the morphologies depend on theproperties derived from the model fits to their SEDs.For protostars with detected outflow cavities, we developan algorithm to measure the shape of the outflow cav-ity, and we calibrate this approach using the radiativetransfer models in our grid.We exclude the images with the F205W filter from thisanalysis as only the 83 objects successfully observed withNICMOS have these data. Furthermore, with a smallnumber of exceptions, the morphologies are identical inthe two NICMOS bands.4.1.
Protostellar Morphologies
The
HST images resolve protostars at various stagesof evolution, different inclinations and differing amountsof envelope material. In these images, light primarily
Cavity Half-Opening Angle ( ) F r a c t i o n C l e a r e d Mass Fraction ClearedVolume Fraction Cleared
Figure 4 . A comparison between the volume fraction clearedused in this work and the mass fraction cleared for parabolic( n = 2) cavities. To obtain the mass cleared, we assumeda spherical envelope with an outer radius of 8000 AU and aradial density profile of ρ − . . The blue solid curve gives thefraction of the envelope mass evacuated by the presence of acavity, while the red curve shows the fraction of the volumesubtended by a cavity. HOPS 357 HOPS 29
Point Source UnipolarBipolar Irregular
HOPS 333 HOPS 94
Figure 5 . Our four morphological types resolved in
Hubble
WFC3 and NICMOS images as exemplified by HOPS 357,29, 333 and 94. All images are squares with 12 (5000 AU) ona side. Note that HOPS 29 shows evidence of an a jet interiorto its cavity and HOPS 333 shows a dark lane commonly seenin bipolar sources. from the photospheres of the central protostars is scat-tered by dust grains in the envelopes, delineating struc-tures present in the envelopes. In many of the images,the structures are similar to those caused by the outflowcavities in our model grid.As a first step in our analysis, we divide all proto-stars into five morphological categories (Figure 5). The presence of a bipolar nebula, such as two scattered-lightlobes separated by a dark lane or two outflow cavities,define the bipolar category. Sources with only one cav-ity visible make up the unipolar category. Unresolvedprotostars without detectable nebulosity are defined aspoint sources. Sources too deeply embedded to detectin the F160W band are considered non-detections (notshown in Figure 5). The final category comprises ir-regular protostars; these may result from backgroundcontamination (e.g., coincidence with a more extendedreflection nebula), or true inhomogeneities in the struc-ture of the protostellar envelope. For bipolar, unipolarand irregular categories, the presence of an unresolvedpoint source in the nebula is noted; these are likely to bethe central protostar or light scattering off of structureswithin 80 AU of the protostar, which is the smallestscale we can resolve in our images.In total, 141 HOPS objects exhibit extended struc-tures in scattered light. The classification of all pro-tostars are found in Table B1, and their breakdown issummarized in Table 2. Of these, thirty-one show abipolar structure indicative of an edge-on inclination,although some cases show the point source of the cen-tral protostar near or offset from the midplane of thedark lane, implying that they are not exactly edge-on.One bipolar source was serendipitously observed in thesame field as HOPS 334. This source was first identifiedas a candidate protostar by Stutz et al. (2013); basedon their values for T bol and L bol , it is determined by thecriteria in Furlan et al. (2016) to be a Class 0 protostar.In this paper, we introduce this source into the HOPScatalog as HOPS 410 (Table B1). Fifty-nine objectsshow nebulosity appearing to be a cavity on one side,with 36 of those having detected point sources near thebase of the cavity. Fifty-one remaining protostars areclassified as irregular. Images of sources with unipolar,bipolar, irregular and point-like morphology are shownin Appendix A. Two additional Class II sources withnebulosity that were serendipitously discovered in ourobservation are shown in Appendix D.Approximately half of our sample, 163 objects, haveno resolvable nebulosity in these observations. Onehundred of these are detected as one or more isolatedpoint sources; these have been analyzed to determinethe companion fractions throughout the Orion Molec-ular Clouds (Kounkel et al. 2016). We refer to theseas point sources without associated nebulosity. In thesecases, any nebulosity around the source appears to bepart of an extended nebula that is illuminated by otherstars in the region or is very faint and tenuous and does This includes objects identified as of uncertain nature or po-tential extragalactic contaminants by Furlan et al. (2016).
Table 2 . Breakdown of F160W morphologies
Point No Point TotalSource SourceNon-detections - 60+3 60+3 a Point Source b c Irregular
39 12 51
Unipolar
36 23 59
Bipolar
16 15 31
Total da One of these three sources is likely an extragalactic source andtwo are of uncertain nature (Furlan et al. 2016). b Sources without associated nebulosity c Six of these seven sources are likely extragalactic sources andone is of uncertain nature. d Includes seven likely extragalactic sources and three of uncertainnature. not delineate a clear structure around the point source.As we will discuss in Sec. 4.4, the scattered light fromcavities and envelopes illuminated by these sources arelikely too faint to detect against the PSF of the pointsource. The remainder of the sources are non-detections.Emission along jets, most likely dominated by the[FeII] line at 1 .
66 µm, is observed in thirteen protostars,with three additional tentative detections. These arethe bipolar protostars HOPS 133, 150, 186 and 216; theunipolar sources HOPS 29, (shown in Figure 5), HOPS164 and 310; the irregular protostars HOPS 98, 188, 234and 386; the point source 279 and the protostar HOPS152, which although not detected directly at 1 .
60 µm, issituated at a location that is an apparent source of jetemission. Tentative detections of jets are found towardthe point source protostars HOPS 3, 344 and 345.In Figure 6, we plot the number of protostars vs bolo-metric temperature for four morphological groups: non-detections, point sources, unipolar or bipolar sources,and protostars with irregular morphologies. The bolo-metric temperature is a measure of the evolutionarystage of the protostar, although it also has some de-pendence on inclination (Ladd et al. 1998, Furlan et al.2016). We also include the standard evolutionaryclasses, as determined with the criteria in Furlan et al.(2016). These figures demonstrate the strong depen-dence of detectability and morphology in the near-IRwith on the class of a protostar. The least evolved pro-tostars (Class 0) are predominantly not detected due tothe greater optical depths in their envelopes. In compar-ison, the most evolved sources (i.e., flat-spectrum pro-tostars and Class II pre-main sequence stars) are domi-nated by unresolved point sources due to the low densityof dust (and therefore low scattering probability) in their
10 100 1000T bol (K)05101520253035 N u m b e r Non-Detections
Class 0Class IFlatClass II 10 100 1000T bol (K)05101520253035 N u m b e r Point Sources
10 100 1000T bol (K)05101520253035 N u m b e r Unipolar/Bipolar
10 100 1000T bol (K)05101520253035 N u m b e r Irregular
Figure 6 . The histograms of bolometric temperatures of oursample for the different morphological classifications. Thecolors give the classification according to the criteria fromFurlan et al. (2016). sparsely filled or non-existent envelopes. Protostarswith unipolar and bipolar cavities show a broad rangeof T bol , but peak in the Class I phase ( T bol ∼
100 K)and contain a significant fraction of Class 0 objects. Fi-nally, the irregular protostars consist largely of Class Iand flat-spectrum sources.We show the distribution of bolometric luminositiesfor each morphological class in Figure 7. The luminos-ity distributions for the three non-irregular classes dis-play a shift in median luminosity, with point sources,unipolar/bipolar protostars and non-detections havingmedian L bol of 0 .
5, 1 . . (cid:12) , respectively. Thischange is small compared to the full range of bolomet-ric luminosities probed, from 0.05 to 480 L (cid:12) . It is likelydue to a decline in the luminosity with increasing age,as found by Fischer et al. (2017).4.2. Direct Measurements of Cavity Sizes
For protostars with unipolar or bipolar morphologies,we fit a power-law to the shape of the cavities to estimatethe amount of the envelope which was cleared by theoutflows. This analysis relies on a custom edge detectionroutine developed to locate the outer contours of thecavities in the images. The methodology is illustratedin Figure 8. It is similar to the Sobel filter described in Furlan et al. (2016) show that flat-spectrum protostars are acombination of protostars with higher density envelopes seen atlow inclinations and protostars with lower envelope densities seenat any inclination. The first possibility is less common since itrequires a limited range of inclinations. L bol (L )05101520253035 N u m b e r Non-Detections
Class 0Class IFlatClass II 10 L bol (L )05101520253035 N u m b e r Point Sources L bol (L )05101520253035 N u m b e r Unipolar/Bipolar L bol (L )05101520253035 N u m b e r Irregular
Figure 7 . The histograms of bolometric luminosities of oursample for the different morphological classifications. Thecolor scheme is identical to Figure 6.
Danielsson & Seger (1990), constrained to the dimensionperpendicular to the axis of the cavity. The image is firstrotated such that the cavity is aligned with the positive y axis in an x − y Cartesian plane; this defines our adoptedaxis for the cavity. In three bipolar cases, those of HOPS136, 280 and 333, we were able to measure the shape ofboth cavities. For each image, a 1D Gaussian smoothingkernel was chosen by eye to account for noise and appliedto every slice of constant y . The width of the smoothingkernel is between 2 and 4 pixels, approximately 0 . .We then calculate the second order finite differencealong the slice (i.e. parallel to the x -axis) using the equa-tion d Idx = I ( x + 2) − I ( x + 1) + I ( x ) , (2)where I ( x ) is the F160W intensity at pixel x . The sec-ond order finite difference, as an approximation to thesecond derivative, is zero at the inflection points of theslice. The inflection points allow us to define an “edge”of the cavity. The width of the smoothing kernel is in-creased to obtain a consistent edge, as a small smooth-ing kernel can produce a discontinuous edge. Inflectionpoints are inspected to ensure that only those tracingthe cavity (as opposed to structure within or outsidethe outflow cavity) are retained. We use this definitionof an edge as it is bounded by the peak of the inten-sity and the background. More sophisticated techniques(e.g. Canny 1986) have a limited advantage due to thepresence of unrelated structures in the line of sight thatcannot be treated as random noise. -3” 0” 3” -3”
6" 4" 2" 0" 8"
Figure 8 . An example of the edge detection technique ap-plied to find the left and right edges (in blue), as well asthe midpoint (in black scatter points) for a model with aninclination of 60° and cavity half-opening angle of 15°. Alsoshown is the analytical shape of the cavity wall with the solidblack line, and the cavity wall as observed for an edge-on in-clination in the dotted black line. At the location of the threered lines, the three plots on the right show an intensity cutalong with the location of the detected edges in blue.
To determine the half-width of the cavity, x , at a givenposition along the cavity axis, y , we measure the fullwidth of the cavity between the two walls and then di-vide by two. Thus, the central axis of the outflow is de-fined by a curve tracing the midpoint of the two walls.Note that the y position is the distance along a straight line that starts at the base of cavity and extends alongthe adopted cavity axis (Figure 8).In order to relate the detected edge to the physicalcavity in the envelope, we ran the edge detection routineon our model grid. We compared the edges measured forthe models as a function of the observed inclination tothe shape of the projected cavity wall for the same modelas observed from an edge-on inclination ; this allows usto correct for the effect of inclination of the shape ofthe outflow. The location of the projected wall is givenby the analytic equation y = A | x | n (Figure 1), where A and n are determined by the parameters of our modelthat are described in more detail below.For most models, the detected edges of the cavitiesdiffer systematically from those of the projected wall(Figure 8); this is due to the combined effects of in-clination, the penetration of the light from the centralprotostars past the cavity wall into the envelope andsystematic biases of the edge detection routine. The in-clination alone will broaden the cavity by 7–25 % for a40–60° inclination assuming a parabolic cavity.Figure 8 shows our edge fitting routine applied to amodel image of a protostar with an inclination of 60°and a cavity half-opening angle of 15°. The black solidline indicate the projected cavity wall of this model, asobserved from this inclination. The black dashed lineindicates where the cavity wall would be for the same0analytical shape, but observed at an edge-on inclination— almost negligible even for a 60° inclination. The de-tected edges (in blue) are characteristically wider thanthe known cavity wall.To quantify the difference between the observed andactual edge, we determined the ratio of the distance tothe “detected” edge in the model to that of the known,projected distance to the wall. For a given model, thisratio was found to be approximately constant as a func-tion of the distance along the outflow axis. Thus, asingle ratio can describe the difference between the ob-served and actual outflow cavity for a given source. Us-ing the grid of models described in Section 3, the ratiowas measured as a function of the cavity half-openingangle and inclination.At lower inclinations, the line of sight toward the cen-tral protostar is more likely to be directly into the cavityor to pass through less envelope material, thus signifi-cantly increasing the probability to observe the proto-star as a point source (see Section 4.4). In these cases,the cavity walls are difficult to detect against the PSF.Additionally, because there exist more possible lines ofsight toward edge-on or near edge-on orientations thanpole-on or near pole-on orientations, the probability thata protostar will be observed at a given inclination de-creases as inclination decreases, assuming that the cav-ity may face any direction randomly. For these reasons,we averaged the ratios determined from all models foreach cavity size, considering only inclination angles from90° to 50°. The ratios are displayed in Figure 9, whichshows that they are predominantly constant as a func-tion of half-opening angle except at the smallest openingangles and that they have a weak dependence on inclina-tion. The standard deviation over all parameters asidefrom cavity size and inclination are shown as the errorbars in this figure.These ratios shown in Figure 9 were applied to themeasured half-width of the cavities from the HST im-ages. Generally, we initially divided the half-width by1 .
3, which is the approximate average ratio for 50°-80°inclination cavities with a half-opening angle greaterthan 15°. For cavities of these sizes that were alsobipolar and thus presumably near 90° in inclination,we restricted our initial ratios to 1 .
1. For cavities withnarrower opening angles and unipolar and bipolar mor-phologies, we chose initial ratios of 2 . . y = A | x − x | n + y . (3) C o rr e c t i o n R a t i o Inclination9080706050
Figure 9 . Ratio of the half-width of the detected edges tothe distance expected for the cavity wall of the model at anedge-on inclination. The inclination i of the models used isgiven in the insert. The error bars give the standard devi-ation among models of differing envelope densities and diskproperties. Note that the corrections are largely constantwith cavity angle, except at the small openings. Vertical Height Above Disk (AU) R a d i a l D i s t a n c e ( A U ) Figure 10 . The detected edges of the northern cavity ofHOPS 136 and several power-law curves corresponding to arange of opening angles. Both the northwestern and north-eastern cavity edges (in blue and teal respectively) were mea-sured in this protostar. The detected half-widths of the cav-ity have been corrected by the model derived ratios shownin Figure 9. The filled regions display the uncertainty inthe location of the cavity edges due to this correction. Thehalf-widths of the northeastern and northwestern edges werefolded together and fit with the power-law curve of exponent n = 3 .
61 half-opening angle θ = 7 .
07 shown in black. Fivepower-law curves of exponent n = 3 .
61 and various openingangles are shown in comparison. to both the model grid discussed in Section 3 and ob-served images (Figure 10). Here, ( x , y ) identify thelocation of the protostar, and are fixed to the center ofour model images. In the observed data, the parameters( x , y ) are manually centered on the central protostarwhen apparent from a point source or an area of maxi-mum flux along the profile of the cavity or were placedalong the disk absorption lane in the case of some bipo-lar sources. The midpoints of the cavity, as shown inFigure 11, were used to fit a center line which in turn1 θ = 5 θ = 15 Figure 11 . An example of the edge detection techniqueapplied to find the left and right edges (in blue), for thebipolar source HOPS 136. For comparison, two paraboliccavities, with half-opening angles of 5° and 15°, are shownin solid and dotted black lines respectively. At the locationof the three red lines, the three plots on the right show anintensity cut along with the location of the detected edges inblue. allowed us to perform a final small-angle rotation cor-rection. Our two detected edges were then consideredfor fitting in three ways: both the left and right edgeswere independently fit with a power-law profile, and,after folding over the now vertical center line, both de-tected edges were simultaneously fitted. This allowed usto counter minor asymmetries in detected cavity edgesas well as outlying points biasing our fitting regime on asingle edge. The recorded parameters were those givenby the single-edge fit with an exponent n greater than1, or in cases where both edges met this criteria, theparameter from the folded fit was recorded. The expo-nent n , which is referred to as the cavity exponent, givesa measure of the collimation of the outflow cavity andmay be indicative of the physical mechanism behind theoutflow creation. For example, Shu et al. (1991) showhow a shell of molecular gas composed of the outflowand swept up material has a shape dependent on theangular distribution of the outflow.By allowing n to be an unconstrained free parameterin our fitting (with the caveat that it be greater than 1),we allow for conical cavities ( n = 1) as well as paraboliccavities ( n = 2). The amplitude A parameterizes thesize of the cavity. For the model used by the HO-CHUNK code, this relates the radius of the envelope ( R max ) andthe cavity half-opening angle θ by: A = R − n max cot n θ. (4)The value of θ is only dependent on A for conical cavities( n = 1), but for other values of n , the value of θ dependson our choice of R max , which we set to 8000 AU. Erroranalyses for functions of the fitted values are discussedin Appendix C. For three protostars with bipolar morphologies, wewere able to measure parameters for both cavities. Inall other bipolar cases, the cavity appearing brighter wasfitted. From our monochromatic model grid, we can seethat inclination is responsible for variations in brightnessbetween the two cavities. We expect the closer cavity tohave a stronger signal due to a smaller extinction alongthe line of sight, although inhomogeneous envelopes mayalso be responsible for differences in cavity brightness.An example of our fitting technique applied to theprotostar HOPS 136 can be seen in Figure 11. Fischeret al. (2014) determined that this protostar is a latestage object with a (10 ± R max = 10 000 AU envelope. The detected edges of itsnorthern cavity are compared with power-law curves asgiven by Equation 3 in Figure 10, revealing the northerncavity of this protostar is best fit by a 8 .
7° half-openingangle, in close agreement with Fischer et al. (2014).For thirty of the ninety protostars in our sample withunipolar or bipolar morphologies, we use this techniquefor measuring the cavity shape, and tabulate the valuesof n in Table B1 along with the half-opening angle. Themedian uncertainty for n , as obtained from the leastsquares fitting of Equation 3, is δn ∼ .
14. We findfrom Equation C1 that uncertainties in half-opening an-gle measurements are on average δθ < . ∼ HST images. For severalsources we see a morphology indicative of an edge-on ornearly edge-on disk but do not see evidence for a cavity(e.g. HOPS 65 and HOPS 200); these may be pre-mainsequence stars with disks. Other protostars have cavi- For the bipolar protostar HOPS 136, measurement of both thenorthern and southern cavity edges was possible. In Table B1, theaverage of both sets of parameters are reported.
10 20 30 40 50
Cavity Half-Opening Angle ( ) P o w e r - L a w E x p o n e n t Figure 12 . The exponents ( n ) and cavity half-opening an-gles ( θ ) from the fits to the detected cavity wall edges of 30measured protostars. The three bipolar sources where bothcavities were able to be fitted are connected with red lines.Typical uncertainties are δθ ∼ .
3° and δn ∼ .
14. (SeeAppendix C.) ties that are too faint to reliably trace (e.g. HOPS 220and HOPS 235), show only one edge of a cavity wall- due to either a non-uniform extinction or an irregu-larly shaped envelope (e.g. HOPS 18 and HOPS 310),or are coincident with nebulosity - making it impossi-ble to disentangle the cavity from larger scale structures(e.g. HOPS 387 and HOPS 384). Finally, some cavi-ties exhibit morphologies inconsistent with a power-lawcavity (e.g. HOPS 8 and HOPS 232). In general, thefactors that prevented automated fitting appeared inci-dental and not obviously correlated with apparent cavitysize. Future efforts will focus on expanding the range ofbrightness levels and morphologies analyzed as well asunderstanding the nature of cavities with only one ap-parent wall.Figure 12 shows the range of fitted exponents n andcavity half-opening angles measured in this work. Wefind the mean and median of the cavity exponents are 1 . . Cavity Sizes vs. SED Derived Properties
The SEDs of the protostars provide information onboth their evolutionary phase as well as their total lu-minosity (e.g. Whitney et al. 2003). Correlations be-tween the SED derived properties of protostars with thecavity sizes provide a means to probe the evolution ofcavities as well as, potentially, their dependence on thefinal mass of the protostar (Fischer et al. 2017). Fig-ure 15 shows two ways of parameterizing the cavity size,half-opening angle and volume fraction cleared, against
HOPS 50HOPS 185HOPS 81
Figure 13 . Examples of protostars with cavities with anassortment of cavity power-law exponents: HOPS 50 ( n =1 . n = 2 .
9) and HOPS 81 ( n = 6 . an assortment of evolutionary indicators derived fromthe 1 . A and n and an envelope radius of 8000 AU.We quantify the degree of correlation by finding theSpearman Rank Correlation Coefficient r , a measure ofthe monotonic correlation between two variables in ourthirty measured protostars. A correlation coefficient of3 Cavity Half-OpeningAngle ( )
Volume FractionCleared
Class 0Class 1Flat
Figure 14 . Histograms of cavity opening angles and volume fraction cleared for our sample of protostars with detected cavitiesin the
HST images. Color scheme is identical to Figure 6. p -value for ahypothesis test are given in Table 3 for each of the di-agnostic indicators and methods of parameterizing thecavity size. The hypothesis test uses a null hypothesisof no correlation; therefore, low p -values indicate evi-dence of a correlation and evolutionary trend. For thethree bipolar sources with both cavities measured, thefound parameters of the two cavities were averaged be-fore computing Spearman Coefficients and p -values.We do not find statistically significant correlation be-tween cavity size and T bol or mass infall rate, (whichshould be considered a proxy for envelope density, asdiscussed in Section 3). As shown in Figure 14, thesample of protostars is dominated by Class I sources; at1 .
60 µm, many Class 0 protostars are not detected, whileflat-spectrum sources are often point sources or have ir-regular nebulosity (see Figure 6). Hence, these resultscan be primarily interpreted as a lack of evidence for anevolution in cavity properties across the Class I phase.The wide scatter in cavity sizes does not appear to bethe result of evolution, but must depend on other envi-ronmental or intrinsic factors.A higher correlation coefficient is found between cavitysize and luminosity, with more luminous objects tendingto have larger cavities; however, the p-values show thatwe cannot rule out the null hypothesis.
Table 3 . Spearman Coefficients and p -values.Evolutionary vs Half-Opening Angle vs Volume FractionDiagnostic r p -value r p -value T bol M infall L bol The Prevalance of Point Sources
We detect cavities towards 90 (30%) of our sample,while 100 (33%) are observed as point sources with-out nebulosity. Since protostars are surrounded by en-velopes that scatter light, the substantial number ofpoint sources without detected scattered-light nebulos-ity is surprising. In this section, we examine why thepoint source morphology is common and test whetherthe number of point sources implies an observationalbias in our cavity size distribution.Protostars may be observed as point sources withoutdetected cavities in two primary cases. First, the cen-tral protostar is observed along a line of sight directlyinto the cavity. In this case the brightness of the PSFfrom the central protostar, which will not be attenuatedby the envelope, can be significantly stronger than scat-tered light from surrounding cavity walls, which mayonly contribute a diffuse scattering around the brightprotostar (Figure 2). Even if the line of sight grazes4
100 1000
Bolometric Temperature (K) H a l f - O p e n i n g A n g l e ()
100 1000
Bolometric Temperature (K) V o l u m e F r a c t i o n Mass Infall Rate (M /yr) H a l f - O p e n i n g A n g l e () Mass Infall Rate (M /yr) V o l u m e F r a c t i o n L bol (L ) H a l f - O p e n i n g A n g l e () L bol (L ) V o l u m e F r a c t i o n Figure 15 . Cavity size diagnostics, half-opening angle ( left ) and volume fraction cleared ( right ), against evolutionary in-dicators. The mass infall rates (from SED model fitting, assuming a 0 . (cid:12) stellar mass) and bolometric temperatures andluminosities are found in Furlan et al. (2016). Data from bipolar sources with both cavities fitted are connected with red lines. the cavity wall, the bright PSF can dominate over thenebulosity. Second, a low density envelope leads to amore diffuse, lower surface brightness cavity wall and abrighter point source; once again, the cavity may notbe visible against the PSF. In both of these cases, theextended nebulosity often found in the Orion clouds canalso hide the scattered light from the cavities.The first case may lead to a bias against detectinglarge cavities. For envelopes with large cavities, thecentral protostar can be directly observed over a largerrange of inclinations. Furthermore, since the walls ofthe cavity are further from the protostar, they will havesystematically lower densities than narrower cavities andthey will intercept less flux from the central star; con-sequently, the walls will be fainter and harder to detectfor large cavities (Figure 2).To determine the combinations of inclinations, cav-ity sizes and envelope densities that lead to the pointsource morphology, and to ascertain potential biases in our observed cavity size distribution, we use a MonteCarlo simulation that combines the model grid in Sec-tion 3, the envelope densities from the SED model fittingof Furlan et al. (2016) and several adopted cavity sizedistributions. The steps of the simulation are as follows.We first determined for each model in our grid whethera cavity would be detected by the WFC3 observations.To determine whether a cavity is detectable, two crite-ria were applied to each model. Non-detections of cav-ities were noted when no distinct edge that delineatesa cavity is found in the image using the technique ofSection 4.2 or when the signal in a cut taken across thecavity 2000 AU from the central protostar has a peakvalue below the typical RMS of an image. At 2000 AU,every protostar with a detected cavity shows nebulosity;if the signal from the nebulosity in the models is belowthe typical RMS values in the WFC3 images, then it isunlikely that the cavity would be detected. The typi-cal RMS was obtained from 30 × off-source patches5
20 0 20 40 60 80
Inclination - Half-Opening Angle ( ) L o g M a ss I n f a ll R a t e ( M y r ) Point Source Fraction Distibution
Figure 16 . Fraction of the model protostars observed aspoint sources in our simulation as a function of parame-ter space. Darker colors indicate a higher fraction of pointsources. In models where the inclination minus the half-opening angle is less than zero, the line of sight towardthe central protostar is directly into the cavity, not passingthrough the infalling envelope. chosen to avoid point sources or outflow cavities. Thesepatches commonly included extended, diffuse nebulositythat is common in the Orion Molecular Clouds.We then performed a Monte Carlo simulation to pre-dict the number of point sources without cavities wewould detect for different assumed cavity half-openingangle distributions. We sampled the models drawingrandomly for four parameters: infall rate (i.e. envelopedensity), inclination, inner F160W flux, and cavity half-opening angle. The distribution of infall rates for oursample of protostars (including those in the “irregular”category) were the best fit values in Furlan et al. (2016).Inclinations were drawn assuming the outflow axes wererandomly oriented. The maximum disk radius, the massof the disk and the radial exponent in the disk densitylaw were left as free parameters to be randomly drawnfrom those in Table 1. The brightness in the inner 0.2"region for each model was determined by scaling the im-age flux to correspond to 1 .
60 µm magnitudes randomlydrawn from the distribution of F160W magnitudes inthe tabulation of Kounkel et al. (2016). Finally, we sam-pled the cavity half-opening angles from several differentdistributions discussed below.We plot the fraction of models resulting in pointsources as a function of infall rate (i.e. envelope den-sity), inclination and cavity half-opening angle in Fig-ure 16. Here we subtract the cavity half-opening angleof a source from the inclination to measure the angle ofthe line of sight with respect to that of the cavity. Wherethis value is below zero, the line of sight is directly intothe cavity and does not pass through the envelope. Wefind in Figure 16 a strong preference for point sourcemorphologies in models observed at such inclinations
Number of Point Sources P r o b a b ili t y o f T o t a l N u m b e r o f P o i n t S o u r c e s Distribution of Angles:0 to 25°0 to 30°0 to 35°0 to 40°0 to 45°Arce DistributionObserved in WFC3
Figure 17 . Histograms of the number of sources detectedas point sources when simulating observations of 230 proto-stars. The top five histograms examine five even distribu-tions of opening angles over ranges indicated in the legend.The "Arce" model, in grey, assumes Arce & Sargent (2006)’sdependence between T bol and cavity half-opening angle toderive a distribution of opening angles using the bolometrictemperature distribution of our sample. A distribution ofopening angles drawn from our 30 measured protostars pro-duces the histogram in red. The horizontal line marks the 70point sources observed among the 230 protostar sub-sampleof our WFC3 observations. and opening angles. When the inclination minus half-opening angle is positive and near zero, then the line ofsight toward the central protostar intersects the lowerdensity, outer regions of the envelope. In this case theincidence of a point source morphology increases withdecreasing infall rate. Finally, if the infall rate is low,point source morphologies can be detected at every in-clination and cavity half-opening angle combination, al-though the incidence increases at lower inclinations. Asexpected, point source morphologies arise when eitherthe protostar is observed through its outflow cavity orwhen the envelope is thin. This is consistent with thepoint source morphology being dominated by protostarswith flat-spectrum SEDs (Figure 6); the flat SEDs areexpected for protostars observed at low inclinations orwith low envelope densities (Calvet et al. 1994, Furlanet al. 2016).6Each iteration of the Monte-Carlo simulation returnsthe number of point sources without detected nebulos-ity. We compare this to the number of point sourcesin our data. Before comparing, we removed from oursample those sources identified by their SEDs as possi-ble extragalactic contaminants or of an uncertain natureand those without complete SEDs (Furlan et al. 2016),except for sources where HST imaging has revealed aunipolar or bipolar morphology, confirming their proto-stellar nature. Seventeen sources observed with WFC3and classified as either non-detections or point sourcesare removed based on these criteria. Finally, we chooseonly the point sources observed with WFC3, in order toaccount for differences in sensitivity. This reduces oursample down to 230 protostars, with 70 point sources.In Figure 17, we show normalized histograms of thenumber of point sources observed for various models ofthe cavity half-opening angle distributions. In red, weshow the simulation results when the cavity sizes arerandomly drawn from the values in Table B1. The ob-served number of point sources is marked with a verticalline. Realizations of 230 protostars with this simulationattain 70 point source detections or less of at rate of1.02%. We note that our exclusion criteria, describedabove, reject 11 objects with point source morphologiesfrom our sample. These objects could not be determinedmorphologically to be extragalactic contaminants, how-ever, and were removed due to their SEDs. We note,however, that protostars may have extragalactic-likeSEDs. HOPS 48, 67 and 301 were classified by Furlanet al. (2016) as extragalactic contaminants based on po-tential emission features in their Spitzer IRS spectra. Inthe case of these three sources, however, the features ap-pear to originate in contamination from reflection nebu-lae or HII regions, and we observe cavities clearly associ-ated with all three with HST
WFC3. Thus we considerour observed number of 70 point sources to be a lowerlimit.We also compare to fiducial models assuming a uni-form distributions of cavities from 0 to 25, 30, 35, 40and 45 degrees. The distributions extending beyond 35°include enough large cavities to overpredict the numberof point sources. These results indicate that our obser-vations are not significantly biased against the detectionof large cavity openings.Finally, we examined the consequences of outflow cav-ities that grow with time. We first adopt the relation-ship between cavity half-opening angle and T bol foundby Arce & Sargent (2006). We used this relationshipand the observed distribution of bolometric tempera- For each distribution of opening angles, we performed 30 thou-sand iterations. tures of our protostars to derive the half-opening angledistribution we entitle “Arce Model.” We used a lin-ear fit between the infall rate and T bol to pick a modelin our grid on each iteration of the Monte Carlo. Thismodel overpredicts the number of point sources, as itdoes not take into account the highly evolved protostarswith low cavity half-opening angles found in our sample(e.g., Fischer et al. 2014).In summary, we find that the histogram producedfrom the observed distribution overlaps with the ob-served number of sources, although with a 1% proba-bility of predicting the predicted number of protostarsor less. If some of our excluded contaminant sourcesare in fact protostellar in nature, the observed distri-bution may provide a better match. Importantly, theresult here is that our observed cavity angle distribu-tion is largely consistent with our observed number ofpoint sources. Uniform distributions of half-opening an-gles extending to 45° overpredict the number of pointsources, and we do not find evidence that our observa-tions fail to detect larger cavities. We also find that theuniform distributions with angles <
35° better repro-duce the observed point sources than our observed dis-tribution. This suggests that we may be missing smallcavities that can be hard to detect due to higher extinc-tion from their envelopes. DISCUSSION: CONSEQUENCES FORPROTOSTELLAR EVOLUTIONThe goal of this study is to assess the impact of jetsand winds on protostellar envelopes. This is an essen-tial step toward both understanding how feedback lowersthe efficiency of star formation and determining the im-portance of feedback in halting mass infall and settingthe final masses of protostars. Feedback can lower effi-ciency and mass infall in three ways: by ejecting massthat would have otherwise been accreted, by clearing theenvelope, and by entraining gas in the envelope and sur-rounding cloud into an outflow (e.g. Watson et al. 2016,Zhang et al. 2016). This paper aims to quantify the roleof cavity clearing.One way outflows may halt infall is by the progressiveclearing of the envelope as the protostar evolves (Arceet al. 2013). This may be driven, for example, by succes-sive bursts of a wide angle wind (Zhang et al. 2019). Thesignature of this clearing would be a correlation betweencavity size and the evolution of the protostellar SEDs.We find no significant trend between cavity half-openingangle with either T bol or model inferred ˙ M , both indi-cators of envelope evolution (Section 4.3). Instead, wefind that there is a range of cavity half-opening anglesextending from 5–50° present across the observed rangeof T bol and the range of ˙ M values inferred from modelfits (Furlan et al. 2016). This implies that the evolu-7tion from dense to thin envelopes is not driven by theprogressive growth of the outflow cavities.To extend this result, we compare our cavity sizes withvolume fractions calculated from millimeter and lowerresolution IR studies in Figure 18. We use the tabu-lated outflow cavity angles and assumed conical cavityshapes to calculate the volume fractions. Our scattered-light measurements extend these by providing a rela-tively large sample at a common distance observed witha uniform spatial resolution, which eliminates possiblebiases due to distance, and by detecting a significantnumber of protostars with relatively high T bol ( >
100 K)and smaller cavities ( <
20 % of the envelope cleared).The range of volume fractions (and hence, cavity half-opening angles) tabulated in the literature are consis-tent with those measured from our data, and there isno evidence for large systematic differences between thedata sets, despite the different types of observations andmethods used to measure the cavity sizes.Arce & Sargent (2006) use millimeter line emission inthe blue and red lobes identified in CO maps to measurethe cavity angle, assuming a conical outflow geometry.Although we do not share sources (so a direct compari-son between the different methods cannot be made), wefind that both the size scales probed and the range ofobserved volume fractions are similar, indicating thatthere are not large, systematic differences between thetwo techniques. Arce & Sargent (2006) suggest a corre-lation between an age diagnostic based on T bol and thecavity size. This correlation, however, is driven signifi-cantly by the Class II objects in their sample, shown inFigure 18. For instance, the Spearman Rank Correla-tion Coefficient of T bol and volume fraction decreases intheir sample from 0.7 to 0.6 ( p = 0 . p = 0 . Spitzer
IRAC. Although this technique has a lowerangular resolution than our study and encompasses asample of objects spanning a much broader range of dis-tances, it has the advantage of being able to detect out-flow cavities from Class 0 objects which are apparent inthe
Spitzer . b – d of thatwork), an indicator that may also depend on cavity sizesince larger cavities allow more radiation to escape atthe wavelengths probed by IRAC. The second correla- tion is with the age parameter from the Robitaille et al.(2007) model grid. This age is used to set the samplingof cavity angles assuming cavity growth and thus couldhave induced a correlation. Futhermore, the correlationwith the age parameter is relatively weak, with the Pear-son product moment at a significance of α = 4 %, and noevidence for a correlation using Kendall’s Tau rank cor-relation coefficient. Sources from Seale & Looney (2008)with bolometric temperatures in the literature are plot-ted as triangles in Figure 18.Other works have found evidence for cavity growthduring the Class 0 phase, as suggested by Arce & Sar-gent (2006). Velusamy et al. (2014) measure the fullopening angle near the base of the cavity using theHiRes reduction of Spitzer
IRAC images. They finda broken power-law growth showing a clear increase inthe sizes of cavities with increasing T bol from protostarswith T bol <
100 K, but do not reproduce the growth formore evolved objects. Hsieh et al. (2017) also present asurvey of low luminosity protostars using IRAC images,in addition to
CFHT
WIRCam Ks -band observations.These authors use the same radiative transfer model-ing code described in Section 3, but they use a directleast-squares fit of their model grid to their images todetermine the cavity parameters. They find evidence fora similar growth during the Class 0 phase. Although wedo not find a similar correlation in our data, the Class0 phase is dominated by non-detection in our 1 .
60 µmimaging and the smallest cavities will be harder to de-tect (Figure 6). Thus, we do not rule out the growth ofcavities during the Class 0 phase.Furlan et al. (2016), using the SEDs and modelingdescribed in Section 4.3, find that the envelopes decreasein density by a factor of 50 as protostars transition fromthe Class 0 to the flat-spectrum phase. By the end ofthe Class I phase, it is thought that most of the stellarmass has been accreted. We should therefore expectthe processes that reduce the mass and density of theprotostellar envelope to continue through the Class Iphase after starting in the Class 0 phase.The lack of a correlation between the fraction of thevolume cleared and the evolutionary indicators, in asample preferentially probing Class I objects, impliesthat the evolution of the envelope during the Class I The Velusamy et al. (2014) power-law breaks at an age of8000 yr, as determined from T bol using the empirical relation ofLadd et al. (1998). This corresponds to a log ( T bol / K) of 2 ± . It is well recognized that the SED depends on both the incli-nation and the evolutionary stage, and the SED classes encompassa mixture of evolutionary stages. The SED classes, however, pro-vide an approximate indicator of the evolution suitable for thisanalysis and has the advantage that they are not model depen-dent. See Robitaille et al. (2007) and Furlan et al. (2016) forfurther discussion.
10 100 1000 T bol (K) V o l u m e F r a c t i o n C l e a r e d Arce & Sargent 2006Arce & Sargent 2006 (Class II)Hsieh, Lai, & Belloche 2017Velusamy, Langer, & Thompson 2014Seale & Looney 2008This Work
Figure 18 . The fraction of the volume cleared by the outflow cavity, as described in Section 3. Our observations, using theprocedure described in Section 4.2, are shown in filled red circles. Black circles are measurements of the outflow cavity anglesfound by Arce & Sargent (2006) and by the references therein. The two filled black circles indicate Class II sources in thissample. Black triangles are the measurements by Seale & Looney (2008) using a different technique on
Spitzer
IRAC images.Bolometric temperatures are from Dunham et al. (2013) or computed where possible with Spitzer photometry from Gutermuthet al. (in prep) and PACS photometry from Pokhrel et al. (in prep). Black diamonds are the opening angles measured byVelusamy et al. (2014) using the HiRes deconvolution algorithm on IRAC images. Finally, black stars are fits by Hsieh et al.(2017) of WIRCam and IRAC images to synthetic images from a model grid generated by the same Whitney et al. (2003) code. phase is not driven by growth of the outflow cavities.Although envelope clearing contributes up to a 40 % re-duction, the more than an order of magnitude drop inthe envelope density cannot be explained by this clear-ing alone. Of particular importance are the number ofprotostars with <
15 % of the envelope cleared through-out the entire range of T bol covered. One of the bestexamples is the protostar HOPS 136, which has a vol-ume cleared of 1 . .
06 M (cid:12) was much smallerthan the estimated stellar mass of 0 . . (cid:12) , showingthat most of the stellar mass has been accreted. A rel-atively low density envelope is inferred from both theSED and the detection of scattered light in the envelopein the HST images (which implies a low optical depthat 1 .
60 µm). The presence of such protostars with a lowdensity, low mass envelope, and narrow outflow cavitiesat the late stages of stellar formation are clear exampleswhere the clearing of the envelopes by outflows cannotexplain the observed low envelope densities.Our results also put limits on the ability of feedbackfrom outflows to explain the low star formation effi-ciency. Comparisons of the Core Mass Function and Ini-tial Mass Function suggest that 60–70 % of the core mass will not accrete onto stars (Alves et al. 2007, Könyveset al. 2015), and previous authors have invoked outflowsas partially responsible for this effect (e.g., Alves et al.2007). Assuming the growth of the cavities is mono-tonic in time, the volume fraction cleared provides alower limit on the mass fraction cleared by the outflows.From our
HST data, the Class I protostars have clearedat most 40 % of their volume (Figure 18). Recalling thatthe mass fraction cleared from a cavity may be as muchas 9 % higher than the volume cleared (Figure 4), themaximum fraction of mass cleared is 50 %. Most of theprotostars have cleared a much smaller mass fraction,even those toward the end of their protostellar phase;the median volume fraction cleared for the HST sampleis only 10 %. These results suggest that the feedbackvia clearing is not sufficient to explain the small starformation efficiency inferred for dense cores, and othermechanisms should be investigated.There are other possible ways outflows may reducestar formation efficiency. The gas launched by the star-disk system in a jet or wind can escape the protostar andits envelope. Using estimates of the mass loss rates of 84protostars, Watson et al. (2016) found that the medianfraction of gas launched is 0 .
09 of the gas accreted (al-though with a wide dispersion); this may decrease the9star formation efficiency by up to an additional 10 %.We find a median star formation efficiency of ∼
70 %given a 10 % median volume fraction cleared, a 9 % in-crease for mass fraction cleared, and an additional 10 %for mass directly launched and ejected by the centralprotostar. Only for the largest cavities, which clear upto ∼
40 % of their envelopes, can the efficiency be as lowas ∼
40 %.Secondly, the size of the cavity seen in scattered lightmay not measure the entire volume of the gas entrainedin the outflow. In support of this, Seale & Looney (2008)noticed a possible discrepancy between their scattered-light outflow cavity sizes and the extent of the outflowinggas traced by millimeter line data. This outflowing gasmay be slower moving, denser gas entrained into theoutflow that is located outside of the cavities.In the case of the HH46/47 outflow, Zhang et al.(2016) used ALMA data in the CO, CO, and C Olines to measure the mass in the outflow, including theslower, denser, entrained gas. They find that the gasmass in the outflow with velocities exceeding the escapevelocity is ∼ SUMMARYWe present WFC3 1 .
60 µm and NICMOS 1 .
60 µm and2 .
05 µm images of 304 protostars and pre-main sequence stars in the Orion Molecular Clouds. All of these ob-jects were studied as part of the Herschel Orion Proto-star Survey (HOPS) and are well characterized by their1 . . . . . .
5. We note that these cavity anglesare not correlated with the SED derived angles ofFurlan et al. (2016), demonstrating that fitting ra-diative transfer models to SEDs does not providereliable constraints on cavity sizes (Appendix G).• Using the well characterized SEDs of Furlan et al.(2016), we look for correlations between the ob-served cavity half-opening angle and evolutionarydiagnostics such as SED class and bolometric tem-perature. Our data show no evidence for a depen-dence of outflow half-opening angle and volumefraction cleared with any of the evolutionary in-dicators. Furthermore, several evolved protostarswith relatively small cavity sizes are identified. We0 conclude that there is no systematic growth of thecavity half-opening angle during the Class I phase.• We find that the incidence of point sources is con-sistent with both the observed cavity angle distri-bution and the distribution of envelope densitiesfrom Furlan et al. (2016). This implies that thepoint sources are protostars observed through aline of sight passing through the outflow cavity(hence seeing the protostar directly) or protostarswith lower envelope density (as are typical of flat-spectrum protostars). Furthermore, we show thatthe number of point sources is inconsistent with asignificant population of large cavities missed byour survey. Instead, our sensitivity to detectingcavities may decrease toward the smallest openingangles. As a whole, this is evidence that the cavitysize distribution we obtain is reasonably completeand representative of the true distribution.• Our findings indicate that outflow clearing is notthe primary mechanism for the dissipation of theenvelope during the Class I phase. It furthersuggests that clearing alone cannot explain the ∼ ∼ Software:
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APPENDIX A. IMAGES OF ALL PROTOSTARSThe images in this appendix show the NICMOS and WFC3 images of protostars which display bipolar or unipolarmorphologies, are point sources without associated nebulosity, or are classified as irregular.2
Figure A1 . NICMOS F160W and F205W images of sources with unipolar or bipolar nebulosity. Figure A2 . NICMOS F160W and F205W images of sources with unipolar or bipolar nebulosity, continued. Figure A3 . NICMOS F160W and F205W images of irregular sources. Figure A4 . NICMOS F160W and F205W images of irregular sources, continued. Figure A5 . NICMOS F160W and F205W images of point sources without associated nebulosity. Figure A6 . NICMOS F160W and F205W images of point sources without associated nebulosity, continued. Figure A7 . NICMOS F160W and F205W images of point sources without associated nebulosity, continued. Figure A8 . WFC3 F160W images of sources with unipolar or bipolar nebulosity. Figure A9 . WFC3 F160W images of sources with unipolar or bipolar nebulosity, continued. Figure A10 . WFC3 F160W images of sources with unipolar or bipolar nebulosity, continued. Figure A11 . WFC3 F160W images of sources with unipolar or bipolar nebulosity, continued. Figure A12 . WFC3 F160W images of irregular sources. Figure A13 . WFC3 F160W images of irregular sources, continued. Figure A14 . WFC3 F160W images of point sources without associated nebulosity. Figure A15 . WFC3 F160W images of point sources without associated nebulosity, continued. Figure A16 . WFC3 F160W images of point sources without associated nebulosity, continued. Figure A17 . WFC3 F160W images of point sources without associated nebulosity, continued. Figure A18 . WFC3 F160W images of point sources without associated nebulosity, continued. B. TABLE OF ALL
HST
SOURCES IN THIS TEXT
Table B1 .HOPS RA DEC SED T bol1 Instrument Point F160W Volume Half-Opening Power-ID ICRS Class Source Morphology Cleared Angle Law Fit(K) (%) ( ◦ ) n1 05 : 54 : 12 . . . . . . . . −
05 : 58 : 27 0 46.2 NIC n Non Detection - - -11 05 : 35 : 13 . −
05 : 57 : 58 0 48.8 NIC n Unipolar - - -12 05 : 35 : 08 . −
05 : 55 : 54 0 42.0 NIC n Unipolar - - -13 05 : 35 : 24 . −
05 : 55 : 33 flat 383.6 NIC y Irregular - - -14 05 : 36 : 19 . −
05 : 55 : 30 flat 464.0 NIC y Irregular - - -15 05 : 36 : 19 . −
05 : 55 : 25 flat 342.0 NIC y Point Source - - -16 05 : 35 : 00 . −
05 : 55 : 25 flat 361.0 NIC y Point Source - - -17 05 : 35 : 07 . −
05 : 52 : 05 I 341.3 WFC3 y Irregular - - -18 05 : 35 : 05 . −
05 : 51 : 54 I 71.8 WFC3 n Unipolar - - -20 05 : 33 : 30 . −
05 : 50 : 41 I 94.8 NIC y Unipolar - - -21 05 : 36 : 10 . −
05 : 50 : 08 ex 584.5 WFC3 y Point Source - - -24 05 : 34 : 46 . −
05 : 44 : 50 I 288.9 WFC3 y Point Source - - -26 05 : 35 : 17 . −
05 : 42 : 14 II 1124.9 WFC3 y Point Source - - -28 05 : 34 : 47 . −
05 : 41 : 55 0 46.3 WFC3 n Bipolar - - -29 05 : 34 : 49 . −
05 : 41 : 42 I 148.2 WFC3 y Unipolar 18.4 26.9 2.330 05 : 34 : 44 . −
05 : 41 : 25 I 81.2 NIC WFC3 n Non Detection - - -31 05 : 35 : 17 . −
05 : 40 : 26 flat 634.7 WFC3 y Point Source - - -32 05 : 34 : 35 . −
05 : 39 : 59 0 58.9 NIC n Unipolar 14.4 28.1 1.335 05 : 35 : 19 . −
05 : 39 : 01 I 305.2 WFC3 y Point Source - - -36 05 : 34 : 26 . −
05 : 37 : 40 flat 374.6 NIC y Point Source - - -38 05 : 35 : 04 . −
05 : 37 : 12 0 58.5 WFC3 n Non Detection - - -40 05 : 35 : 08 . −
05 : 35 : 59 0 38.1 WFC3 n Non Detection - - -41 05 : 34 : 29 . −
05 : 35 : 42 I 82.3 NIC n Non Detection - - -42 05 : 35 : 05 . −
05 : 35 : 40 I 200.9 NIC WFC3 n Bipolar - - -43 05 : 35 : 04 . −
05 : 35 : 14 I 75.0 NIC WFC3 n Non Detection - - -44 05 : 35 : 10 . −
05 : 35 : 06 0 43.8 NIC WFC3 n Unipolar - - -45 05 : 35 : 06 . −
05 : 33 : 35 flat 517.8 NIC WFC3 y Irregular - - -48
05 : 35 : 06 . −
05 : 32 : 51 flat 611.0 WFC3 y Unipolar - - -
Table B1 continued Table B1 (continued)
HOPS RA DEC SED T bol1 Instrument Point F160W Volume Half-Opening Power-ID ICRS Class Source Morphology Cleared Angle Law Fit(K) (%) ( ◦ ) n50 05 : 34 : 40 . −
05 : 31 : 44 0 51.4 WFC3 y Unipolar 15.4 28.0 1.553 05 : 33 : 57 . −
05 : 23 : 30 0 45.9 NIC n Non Detection - - -56 05 : 35 : 19 . −
05 : 15 : 32 0 48.1 NIC n Non Detection - - -57 05 : 35 : 19 . −
05 : 15 : 08 flat 421.2 NIC y Irregular - - -58 05 : 35 : 18 . −
05 : 13 : 38 flat 620.0 WFC3 y Irregular - - -59 05 : 35 : 20 . −
05 : 13 : 15 flat 528.4 WFC3 y Irregular - - -60 05 : 35 : 23 . −
05 : 12 : 03 0 54.1 WFC3 n Unipolar - - -62 05 : 35 : 24 . −
05 : 11 : 29 flat 1154.1 NIC WFC3 y Point Source - - -63 05 : 35 : 24 . −
05 : 10 : 01 flat 544.5 WFC3 n Non Detection - - -64 05 : 35 : 26 . −
05 : 09 : 54 I 29.7 WFC3 y Unipolar 0.49 4.1 3.865 05 : 35 : 21 . −
05 : 09 : 38 I 545.7 NIC y Unipolar - - -66 05 : 35 : 26 . −
05 : 09 : 24 flat 264.9 WFC3 y Unipolar 5.0 17.5 1.167 05 : 35 : 22 . −
05 : 08 : 34 I 278.7 WFC3 y Bipolar - - -68 05 : 35 : 24 . −
05 : 08 : 30 I 100.6 WFC3 n Non Detection - - -69 05 : 35 : 25 . −
05 : 08 : 23 flat 31.3 WFC3 n Non Detection - - -70 05 : 35 : 22 . −
05 : 08 : 04 flat 619.3 WFC3 y Point Source - - -71 05 : 35 : 25 . −
05 : 07 : 57 I 277.5 NIC WFC3 y Point Source - - -72 05 : 35 : 25 . −
05 : 07 : 46 ex 693.0 NIC WFC3 y Point Source - - -73 05 : 35 : 27 . −
05 : 07 : 03 0 43.0 WFC3 n Unipolar 0.53 5.3 1.474 05 : 35 : 24 . −
05 : 06 : 21 flat 516.5 WFC3 y Point Source - - -75 05 : 35 : 26 . −
05 : 06 : 10 0 67.9 WFC3 n Non Detection - - -76 05 : 35 : 25 . −
05 : 05 : 57 I 135.5 NIC WFC3 y Unipolar - - -77 05 : 35 : 31 . −
05 : 05 : 47 flat 550.3 WFC3 y Unipolar - - -78 05 : 35 : 25 . −
05 : 05 : 43 0 38.1 WFC3 n Non Detection - - -79 05 : 35 : 27 . −
05 : 05 : 36 flat 666.2 WFC3 y Point Source - - -80 05 : 35 : 25 . −
05 : 05 : 09 flat 275.3 WFC3 y Point Source - - -81 05 : 35 : 27 . −
05 : 04 : 58 0 40.1 WFC3 n Unipolar 1.7 6.9 6.782 05 : 35 : 19 . −
05 : 04 : 54 flat 116.4 WFC3 y Point Source - - -84 05 : 35 : 26 . −
05 : 03 : 55 I 90.8 WFC3 y Unipolar 28.3 35.9 1.885 05 : 35 : 28 . −
05 : 03 : 40 flat 174.2 WFC3 y Point Source - - -86 05 : 35 : 23 . −
05 : 01 : 40 I 112.7 WFC3 y Unipolar - - -87 05 : 35 : 23 . −
05 : 01 : 28 0 38.1 WFC3 n Non Detection - - -88 05 : 35 : 22 . −
05 : 01 : 14 0 42.4 WFC3 n Non Detection - - -89 05 : 35 : 19 . −
05 : 01 : 02 flat 158.3 WFC3 y Point Source - - -91 05 : 35 : 18 . −
05 : 00 : 50 0 41.7 WFC3 n Non Detection - - -92 05 : 35 : 18 . −
05 : 00 : 32 flat 186.3 WFC3 y Point Source - - -93 05 : 35 : 15 . −
05 : 00 : 08 I 107.3 NIC WFC3 n Bipolar 5.1 17.3 1.2
Table B1 continued Table B1 (continued)
HOPS RA DEC SED T bol1 Instrument Point F160W Volume Half-Opening Power-ID ICRS Class Source Morphology Cleared Angle Law Fit(K) (%) ( ◦ ) n94 05 : 35 : 16 . −
05 : 00 : 02 I 123.0 NIC WFC3 y Irregular - - -95 05 : 35 : 34 . −
04 : 59 : 52 0 41.8 NIC n Non Detection - - -96 05 : 35 : 29 . −
04 : 58 : 48 0 35.6 WFC3 n Non Detection - - -97 05 : 35 : 28 . −
04 : 57 : 38 ex 403.8 WFC3 y Point Source - - -98 05 : 35 : 19 . −
04 : 55 : 44 II 587.5 WFC3 y Irregular - - -99 05 : 34 : 29 . −
04 : 55 : 30 0 48.9 NIC n Non Detection - - -101 05 : 35 : 08 . −
04 : 54 : 09 ex 481.2 WFC3 y Point Source - - -105 05 : 35 : 32 . −
04 : 46 : 48 flat 520.3 WFC3 y Point Source - - -107 05 : 35 : 23 . −
04 : 40 : 10 flat 472.0 WFC3 y Unipolar - - -108 05 : 35 : 27 . −
05 : 10 : 00 0 38.5 WFC3 n Non Detection - - -113 05 : 39 : 58 . −
07 : 26 : 41 II 583.8 WFC3 y Point Source - - -114 05 : 40 : 01 . −
07 : 25 : 38 I 117.3 WFC3 y Point Source - - -115 05 : 39 : 56 . −
07 : 25 : 51 flat 461.3 WFC3 y Point Source - - -116 05 : 39 : 57 . −
07 : 25 : 13 flat 411.1 WFC3 y Point Source - - -117 05 : 39 : 55 . −
07 : 24 : 19 flat 277.0 WFC3 y Point Source - - -118 05 : 39 : 54 . −
07 : 24 : 14 flat 552.8 WFC3 y Irregular - - -119 05 : 39 : 50 . −
07 : 23 : 30 flat 573.8 WFC3 y Point Source - - -120 05 : 39 : 34 . −
07 : 26 : 11 flat 455.3 WFC3 y Irregular - - -121 05 : 39 : 33 . −
07 : 23 : 01 0 34.8 WFC3 y Point Source - - -123 05 : 39 : 33 . −
07 : 22 : 57 0 50.1 WFC3 n Non Detection - - -124 05 : 39 : 19 . −
07 : 26 : 11 0 44.8 NIC n Irregular - - -125 05 : 39 : 19 . −
07 : 26 : 18 flat 110.5 NIC y Irregular - - -127 05 : 39 : 00 . −
07 : 20 : 22 I 133.3 WFC3 y Unipolar - - -128 05 : 38 : 52 . −
07 : 21 : 06 flat 469.2 WFC3 y Point Source - - -129 05 : 39 : 11 . −
07 : 10 : 34 flat 191.3 WFC3 y Unipolar - - -130 05 : 39 : 02 . −
07 : 12 : 52 I 156.7 WFC3 y Point Source - - -131 05 : 39 : 07 . −
07 : 10 : 52 I 82.3 WFC3 y Point Source - - -132 05 : 39 : 05 . −
07 : 11 : 05 flat 616.3 WFC3 y Unipolar - - -133 05 : 39 : 05 . −
07 : 10 : 39 I 74.6 WFC3 n Bipolar - - -135 05 : 38 : 45 . −
07 : 10 : 55 I 130.3 NIC n Bipolar 22.1 38.4 1.0136
05 : 38 : 46 . −
07 : 05 : 37 I 161.7 NIC n Bipolar 1.8 8.7 2.5138 05 : 38 : 48 . −
07 : 02 : 43 0 42.8 WFC3 y Point Source - - -139 05 : 38 : 49 . −
07 : 01 : 17 I 84.3 WFC3 n Irregular - - -140 05 : 38 : 46 . −
07 : 01 : 53 I 137.2 WFC3 y Point Source - - -141 05 : 38 : 48 . −
07 : 00 : 49 flat 741.6 NIC WFC3 y Point Source - - -143 05 : 38 : 46 . −
07 : 00 : 48 I 242.1 NIC WFC3 n Non Detection - - -144 05 : 38 : 45 . −
07 : 01 : 01 I 99.2 NIC WFC3 n Non Detection - - -
Table B1 continued Table B1 (continued)
HOPS RA DEC SED T bol1 Instrument Point F160W Volume Half-Opening Power-ID ICRS Class Source Morphology Cleared Angle Law Fit(K) (%) ( ◦ ) n145 05 : 38 : 43 . −
07 : 01 : 13 I 133.7 NIC WFC3 y Irregular - - -146 05 : 38 : 44 . −
07 : 00 : 40 ex 519.7 WFC3 y Point Source - - -148 05 : 38 : 39 . −
06 : 59 : 30 I 262.9 NIC y Point Source - - -150 05 : 38 : 07 . −
07 : 08 : 29 flat 245.2 WFC3 y Bipolar 11.6 26.2 1.2152 05 : 37 : 58 . −
07 : 07 : 25 0 53.8 WFC3 n Non Detection - - -153 05 : 37 : 57 . −
07 : 06 : 56 0 39.4 WFC3 n Non Detection - - -154 05 : 38 : 20 . −
06 : 59 : 04 I 166.7 WFC3 y Point Source - - -156 05 : 38 : 03 . −
06 : 58 : 15 I 90.1 NIC y Point Source - - -157 05 : 37 : 56 . −
06 : 56 : 39 I 77.6 NIC n Irregular - - -158 05 : 37 : 24 . −
06 : 58 : 32 flat 591.6 NIC y Point Source - - -159 05 : 37 : 53 . −
06 : 47 : 16 flat 498.4 NIC y Point Source - - -160 05 : 37 : 51 . −
06 : 47 : 20 I 80.4 NIC y Unipolar - - -163 05 : 37 : 17 . −
06 : 36 : 18 I 432.3 WFC3 y Point Source - - -164 05 : 37 : 00 . −
06 : 37 : 10 0 50.0 WFC3 n Unipolar 1.2 7.5 1.8165 05 : 36 : 23 . −
06 : 46 : 14 I 96.1 NIC n Non Detection - - -166 05 : 36 : 25 . −
06 : 44 : 41 flat 457.1 NIC y Point Source - - -167 05 : 36 : 19 . −
06 : 46 : 00 flat 568.6 NIC y Point Source - - -168 05 : 36 : 18 . −
06 : 45 : 22 0 54.0 NIC n Irregular - - -169 05 : 36 : 36 . −
06 : 38 : 51 0 32.5 NIC n Non Detection - - -170 05 : 36 : 41 . −
06 : 34 : 00 flat 832.5 NIC y Point Source - - -171 05 : 36 : 17 . −
06 : 38 : 01 0 61.8 WFC3 n Bipolar 8.2 21.3 1.3172 05 : 36 : 19 . −
06 : 29 : 06 I 149.8 NIC y Point Source - - -173 05 : 36 : 26 . −
06 : 25 : 05 0 60.2 WFC3 n Non Detection - - -174 05 : 36 : 25 . −
06 : 24 : 58 flat 350.3 WFC3 y Irregular - - -175 05 : 36 : 24 . −
06 : 24 : 54 I 104.3 NIC WFC3 y Point Source - - -176 05 : 36 : 23 . −
06 : 24 : 51 flat 312.2 NIC WFC3 y Irregular - - -177 05 : 35 : 50 . −
06 : 34 : 53 I 84.7 NIC n Irregular - - -178 05 : 36 : 24 . −
06 : 22 : 41 I 155.1 WFC3 y Point Source - - -179 05 : 36 : 21 . −
06 : 23 : 29 flat 467.5 WFC3 y Irregular - - -181 05 : 36 : 19 . −
06 : 22 : 12 I 131.3 WFC3 n Non Detection - - -182 05 : 36 : 18 . −
06 : 22 : 10 0 51.9 WFC3 n Non Detection - - -183 05 : 36 : 17 . −
06 : 22 : 28 flat 224.5 WFC3 y Point Source - - -184 05 : 36 : 12 . −
06 : 23 : 30 II 201.3 WFC3 y Point Source - - -185 05 : 36 : 36 . −
06 : 14 : 57 I 96.9 WFC3 y Unipolar 9.1 18.2 2.7186 05 : 35 : 47 . −
06 : 26 : 14 I 72.3 WFC3 n Bipolar - - -187 05 : 35 : 50 . −
06 : 22 : 43 flat 1210.9 WFC3 y Point Source - - -188 05 : 35 : 29 . −
06 : 26 : 58 I 103.3 WFC3 y Irregular - - -
Table B1 continued Table B1 (continued)
HOPS RA DEC SED T bol1 Instrument Point F160W Volume Half-Opening Power-ID ICRS Class Source Morphology Cleared Angle Law Fit(K) (%) ( ◦ ) n189 05 : 35 : 30 . −
06 : 26 : 32 I 133.1 NIC WFC3 y Point Source - - -190 05 : 35 : 28 . −
06 : 27 : 01 I 385.3 WFC3 y Bipolar 13.3 26.2 1.5191 05 : 36 : 17 . −
06 : 11 : 10 I 196.7 NIC y Bipolar - - -192 05 : 36 : 32 . −
06 : 01 : 16 flat 202.5 WFC3 y Unipolar - - -193 05 : 36 : 30 . −
06 : 01 : 17 I 226.7 NIC WFC3 y Point Source - - -194 05 : 35 : 51 . −
06 : 10 : 01 flat 645.0 NIC y Point Source - - -197 05 : 34 : 15 . −
06 : 34 : 32 flat 506.6 NIC y Point Source - - -198 05 : 35 : 22 . −
06 : 13 : 06 0 61.4 NIC n Irregular - - -199 05 : 34 : 39 . −
06 : 25 : 14 flat 576.7 NIC y Point Source - - -200 05 : 35 : 33 . −
06 : 06 : 09 flat 244.4 NIC n Bipolar - - -203 05 : 36 : 22 . −
06 : 46 : 06 0 43.7 NIC n Non Detection - - -204 05 : 43 : 10 . −
08 : 46 : 07 I 85.4 NIC y Unipolar - - -205 05 : 43 : 02 . −
08 : 47 : 49 ex 427.8 WFC3 y Point Source - - -206 05 : 43 : 07 . −
08 : 44 : 31 0 65.1 WFC3 n Non Detection - - -207 05 : 42 : 38 . −
08 : 50 : 18 flat 446.2 WFC3 y Irregular - - -209 05 : 42 : 52 . −
08 : 41 : 41 I 554.1 WFC3 y Point Source - - -210 05 : 42 : 58 . −
08 : 38 : 05 flat 204.9 WFC3 y Point Source - - -211 05 : 42 : 58 . −
08 : 37 : 43 flat 87.9 WFC3 n Non Detection - - -213 05 : 42 : 48 . −
08 : 40 : 08 flat 534.9 WFC3 y Unipolar - - -214 05 : 42 : 47 . −
08 : 36 : 36 flat 360.8 WFC3 y Point Source - - -215 05 : 43 : 09 . −
08 : 29 : 27 I 195.5 NIC y Point Source - - -216 05 : 42 : 55 . −
08 : 32 : 48 I 117.7 WFC3 n Bipolar - - -219 05 : 41 : 29 . −
08 : 43 : 04 I 90.0 WFC3 n Bipolar 37.6 49.7 1.1220 05 : 41 : 29 . −
08 : 42 : 45 I 193.6 WFC3 y Bipolar - - -221 05 : 42 : 47 . −
08 : 17 : 06 I 172.3 WFC3 y Unipolar - - -222 05 : 41 : 26 . −
08 : 42 : 24 II 738.2 WFC3 y Point Source - - -223 05 : 42 : 48 . −
08 : 16 : 34 I 247.5 WFC3 y Irregular - - -224 05 : 41 : 32 . −
08 : 40 : 09 0 48.6 NIC n Non Detection - - -225 05 : 41 : 30 . −
08 : 40 : 17 flat 432.5 NIC y Point Source - - -226 05 : 41 : 30 . −
08 : 40 : 09 flat 350.2 NIC y Point Source - - -228 05 : 41 : 34 . −
08 : 35 : 27 I 293.0 NIC n Unipolar - - -229 05 : 42 : 47 . −
08 : 10 : 08 flat 471.6 WFC3 y Point Source - - -232 05 : 41 : 35 . −
08 : 08 : 22 I 187.9 WFC3 y Bipolar - - -233 05 : 41 : 52 . −
08 : 01 : 21 I 106.2 WFC3 y Bipolar 0.71 4.9 3.9234 05 : 41 : 49 . −
08 : 01 : 26 I 79.8 WFC3 y Irregular - - -235 05 : 41 : 25 . −
08 : 05 : 54 flat 680.1 WFC3 y Point Source - - -236 05 : 41 : 30 . −
08 : 03 : 41 flat 332.8 WFC3 y Unipolar - - -
Table B1 continued Table B1 (continued)
HOPS RA DEC SED T bol1 Instrument Point F160W Volume Half-Opening Power-ID ICRS Class Source Morphology Cleared Angle Law Fit(K) (%) ( ◦ ) n237 05 : 41 : 28 . −
08 : 03 : 25 I 177.7 NIC WFC3 y Point Source - - -238 05 : 41 : 26 . −
08 : 03 : 12 I 269.1 WFC3 y Point Source - - -239 05 : 41 : 27 . −
08 : 00 : 54 I 116.2 WFC3 y Point Source - - -240 05 : 41 : 25 . −
08 : 01 : 15 I 191.0 WFC3 y Point Source - - -241 05 : 41 : 26 . −
08 : 01 : 02 I 100.3 WFC3 n Non Detection - - -242 05 : 40 : 48 . −
08 : 11 : 08 flat 836.7 WFC3 y Point Source - - -243 05 : 41 : 01 . −
08 : 06 : 44 0 50.8 WFC3 n Non Detection - - -244 05 : 41 : 01 . −
08 : 06 : 01 I 127.3 WFC3 n Unipolar 10.5 23.4 1.4245 05 : 41 : 22 . −
07 : 58 : 55 flat 302.1 WFC3 y Point Source - - -246 05 : 40 : 47 . −
08 : 09 : 47 I 95.6 WFC3 y Irregular - - -247 05 : 41 : 26 . −
07 : 56 : 51 0 42.8 WFC3 n Irregular - - -248 05 : 41 : 22 . −
07 : 58 : 02 flat 484.3 WFC3 y Point Source - - -249 05 : 40 : 52 . −
08 : 05 : 48 flat 268.5 WFC3 y Point Source - - -250 05 : 40 : 48 . −
08 : 06 : 57 0 69.4 WFC3 y Unipolar 29.8 38.4 1.5251 05 : 40 : 54 . −
08 : 05 : 13 flat 345.7 WFC3 y Unipolar - - -252 05 : 40 : 49 . −
08 : 06 : 08 flat 329.2 WFC3 y Irregular - - -253 05 : 41 : 28 . −
07 : 53 : 50 flat 321.1 WFC3 y Unipolar - - -254 05 : 41 : 24 . −
07 : 55 : 07 I 114.7 WFC3 n Unipolar - - -255 05 : 40 : 50 . −
08 : 05 : 48 flat 572.0 WFC3 y Point Source - - -256 05 : 40 : 45 . −
08 : 06 : 42 0 72.4 WFC3 y Irregular - - -257 05 : 41 : 19 . −
07 : 55 : 46 flat 292.6 WFC3 y Irregular - - -258 05 : 41 : 24 . −
07 : 54 : 08 flat 385.7 WFC3 y Irregular - - -259 05 : 40 : 20 . −
08 : 13 : 55 flat 410.3 WFC3 y Unipolar - - -260 05 : 40 : 19 . −
08 : 14 : 16 flat 600.1 WFC3 y Irregular - - -261 05 : 41 : 18 . −
07 : 55 : 29 I 149.5 WFC3 y Irregular - - -262 05 : 41 : 23 . −
07 : 53 : 41 flat 202.4 WFC3 y Point Source - - -263 05 : 41 : 23 . −
07 : 53 : 46 I 145.1 WFC3 n Non Detection - - -265 05 : 41 : 20 . −
07 : 53 : 10 flat 635.1 WFC3 y Point Source - - -267 05 : 41 : 19 . −
07 : 50 : 41 I 186.2 NIC y Point Source - - -268 05 : 40 : 38 . −
08 : 00 : 35 I 113.9 NIC n Irregular - - -270 05 : 40 : 40 . −
07 : 54 : 39 I 96.6 WFC3 n Bipolar - - -272 05 : 40 : 20 . −
07 : 56 : 39 II 559.2 WFC3 y Point Source - - -273 05 : 40 : 20 . −
07 : 56 : 24 I 243.3 WFC3 y Unipolar 22.8 34.4 1.4274 05 : 40 : 20 . −
07 : 54 : 59 flat 546.5 WFC3 y Irregular - - -275 05 : 40 : 36 . −
07 : 49 : 06 I 146.4 WFC3 y Unipolar 22.5 35.7 1.3278 05 : 40 : 20 . −
07 : 51 : 14 I 96.3 WFC3 y Point Source - - -279 05 : 40 : 17 . −
07 : 48 : 25 flat 382.0 NIC WFC3 y Point Source - - -
Table B1 continued Table B1 (continued)
HOPS RA DEC SED T bol1 Instrument Point F160W Volume Half-Opening Power-ID ICRS Class Source Morphology Cleared Angle Law Fit(K) (%) ( ◦ ) n280
05 : 40 : 14 . −
07 : 48 : 48 I 121.2 WFC3 y Bipolar 16.0 28.4 1.5281 05 : 40 : 24 . −
07 : 43 : 08 flat 189.3 WFC3 y Irregular - - -282 05 : 40 : 26 . −
07 : 37 : 31 I 95.1 WFC3 n Irregular - - -283 05 : 40 : 44 . −
07 : 29 : 54 II 807.9 WFC3 y Point Source - - -284 05 : 38 : 51 . −
08 : 01 : 27 flat 913.9 WFC3 y Unipolar - - -286 05 : 39 : 58 . −
07 : 31 : 12 I 123.7 NIC WFC3 y Point Source - - -287 05 : 40 : 08 . −
07 : 27 : 27 I 117.8 WFC3 n Bipolar 6.3 15.4 2.7288 05 : 39 : 55 . −
07 : 30 : 27 0 48.6 WFC3 n Unipolar - - -289 05 : 39 : 56 . −
07 : 30 : 06 I 331.1 WFC3 y Bipolar - - -290 05 : 39 : 57 . −
07 : 29 : 33 0 47.3 WFC3 n Non Detection - - -291 05 : 39 : 57 . −
07 : 28 : 57 flat 340.1 WFC3 y Point Source - - -294 05 : 40 : 51 . −
02 : 26 : 48 flat 606.8 WFC3 y Point Source - - -295 05 : 41 : 28 . −
02 : 23 : 19 I 86.6 WFC3 y Bipolar - - -297 05 : 41 : 23 . −
02 : 17 : 35 I 274.9 WFC3 y Point Source - - -298 05 : 41 : 37 . −
02 : 17 : 16 I 169.3 WFC3 y Irregular - - -299 05 : 41 : 44 . −
02 : 16 : 06 I 277.0 NIC WFC3 y Point Source - - -300 05 : 41 : 24 . −
02 : 16 : 06 I 93.7 WFC3 y Unipolar 1.0 6.8 2.0301 05 : 41 : 44 . −
02 : 15 : 55 flat 518.8 WFC3 y Unipolar - - -305 05 : 41 : 45 . −
01 : 51 : 56 flat 300.7 WFC3 y Point Source - - -310 05 : 42 : 27 . −
01 : 20 : 00 0 51.8 WFC3 n Unipolar - - -311 05 : 43 : 03 . −
01 : 16 : 28 flat 383.0 NIC WFC3 y Irregular - - -312 05 : 43 : 05 . −
01 : 15 : 54 0 46.7 WFC3 n Non Detection - - -316 05 : 46 : 07 . −
00 : 13 : 22 0 55.2 NIC y Irregular - - -317 05 : 46 : 08 . −
00 : 10 : 38 0 47.5 WFC3 n Unipolar - - -321 05 : 46 : 33 . . . . . . . .
05 : 47 : 22 . . . . . Table B1 continued Table B1 (continued)
HOPS RA DEC SED T bol1 Instrument Point F160W Volume Half-Opening Power-ID ICRS Class Source Morphology Cleared Angle Law Fit(K) (%) ( ◦ ) n340 05 : 47 : 01 . . . . . . . . . −
05 : 08 : 33 - - WFC3 y Point Source - - -351 05 : 35 : 31 . −
05 : 04 : 47 ex 217.1 WFC3 n Non Detection - - -352 05 : 35 : 26 . −
05 : 04 : 02 - - WFC3 n Non Detection - - -353 05 : 54 : 13 . . . −
06 : 49 : 49 0 44.9 WFC3 n Non Detection - - -357 05 : 41 : 39 . −
01 : 52 : 07 flat 628.2 WFC3 y Point Source - - -358 05 : 46 : 07 . −
00 : 13 : 29 0 41.7 NIC n Non Detection - - -359 05 : 47 : 24 . . . . . . . . . −
05 : 10 : 30 I 137.5 WFC3 n Bipolar - - -369 05 : 35 : 26 . −
05 : 10 : 17 flat 379.2 WFC3 y Irregular - - -370 05 : 35 : 27 . −
05 : 09 : 33 I 71.5 WFC3 n Irregular - - -374 05 : 41 : 25 . −
07 : 55 : 18 0 56.9 WFC3 y Point Source - - -376 05 : 38 : 18 . −
07 : 02 : 26 flat 492.0 WFC3 y Irregular - - -377 05 : 38 : 45 . −
07 : 01 : 02 0 53.7 NIC WFC3 n Non Detection - - -380 05 : 36 : 25 . −
06 : 25 : 02 0 36.6 WFC3 n Non Detection - - -382 05 : 35 : 21 . −
05 : 37 : 57 I 204.4 WFC3 y Point Source - - -383 05 : 35 : 29 . −
04 : 59 : 51 0 45.8 WFC3 n Non Detection - - -386 05 : 46 : 08 . −
00 : 10 : 02 I 147.4 WFC3 y Irregular - - -387 05 : 46 : 07 . −
00 : 10 : 00 I 118.3 WFC3 y Bipolar - - -389 05 : 46 : 47 . . Table B1 continued Table B1 (continued)
HOPS RA DEC SED T bol1 Instrument Point F160W Volume Half-Opening Power-ID ICRS Class Source Morphology Cleared Angle Law Fit(K) (%) ( ◦ ) n392 05 : 46 : 16 . . . −
05 : 07 : 53 0 45.5 WFC3 y Unipolar - - -397 05 : 42 : 48 . −
08 : 16 : 10 0 46.1 WFC3 n Non Detection - - -399 05 : 41 : 24 . −
02 : 18 : 08 0 31.1 WFC3 n Non Detection - - -405 05 : 40 : 58 . −
08 : 05 : 36 0 35.0 WFC3 n Non Detection - - -406 05 : 47 : 43 . . . −
07 : 23 : 59 0 37.9 WFC3 n Non Detection - - -410
05 : 46 : 53 . T bol are from Stutz et al. (2013).C. ERROR ANALYSISUncertainties for functions of the fitted values de-scribed in Section 4.2 were computed without assumingany independence between the fitted parameters, partic-ularly n and A . Since θ is found as a function of thesetwo parameters, the uncertainty δθ is given by δθ ≤ (cid:12)(cid:12)(cid:12)(cid:12) ∂θ∂A (cid:12)(cid:12)(cid:12)(cid:12) δA + (cid:12)(cid:12)(cid:12)(cid:12) ∂θ∂n (cid:12)(cid:12)(cid:12)(cid:12) δn (C1)= R max ( AR max ) /n (cid:0) A (cid:12)(cid:12) ln (cid:0) R max A (cid:1)(cid:12)(cid:12) δn + n δA (cid:1) An (cid:16) R /n max + A /n R (cid:17) . (C2)We note that this uncertainty is more strongly depen-dant on uncertainties in n than on those in A .We calculate the adjusted uncertainty in the power-law coefficient A in Equation 1 by the equation: δA = 1 C n δA fit + A nC n +1 δC + AC n ln ( C ) δn, (C3)where C represents the correction factor shown in Fig-ure 9 used to account for the effects of inclination onwhere cavity edges are detected, δC is the uncertaintyfor a given correction value, δA fit is the non-adjusted uncertainty in parameter A resulting from least squaresfitting Equation 1 to the location of detected cavityedges and δn is the uncertainty in n given the samefit.By approximating conical outflow cavities of half-opening angles θ , (as computed from A and n from therelation in Equation 4), the estimated uncertainty in thefraction of the envelope volume subtended by our mea-sured outflow cavities is given as δf vol = | ∂f vol ∂θ | δθ = sin( θ ) δθ, (C4)where f vol is given by f vol = 1 − cos( θ ) . (C5)Values for these uncertainties are discussed in Sec-tion 4.2. D. EXTENDED CLASS II OBJECTSApproximately 200 pre-main sequence stars withdisks, or Class II objects, were serependipitously inour WFC3 observations; these are tabulated in Kounkelet al. (2016). We have found that two of these objectsare associated with bright, compact nebulosity similar9
HOPS 339
STS2013 038002
Figure E19 . Hubble
WFC3 images of two non-protostellarsources clarified to be extragalactic.
STS2013 92011
Figure E20 . One of the four objects with weak 24 µm fluxtargeted by
HST program 14695 is revealed in WFC3 imag-ing to be an outflow knot. Emission is likely dominated bythe [FeII] line at 1 .
66 µm . to that found around protostars (Figure E21). MGM2742 (V2475 Ori) is a binary which is associated with anebula with an irregular morphology. MGM 925 (V2674Ori) appears to be seen nearly edge-on and has a clearbipolar morphology. E. MORPHOLOGICAL IDENTIFICATION OFCONTAMINATIONWe are able to revise our identification of three objectsby their morphology, showing them to be contamination.HOPS 339, shown in Figure E19, is determined to be adisk galaxy. Furlan et al. (2016) describes its SED asmostly flat with a strong 10 µm absorption feature andnotes that by SED alone it would not be flagged as apossible extragalactic contaminant. This illustrates theimportance of high-resolution near-infrared observationsin disentangling galactic contaminants and protostellarobjects. One protostellar candidate identified in Stutzet al. (2013), STS2013 038002 (Figure E19), was tar-geted by the
HST program GO 14695. The source ap-pears to be an extended streak; we suggest that it is abackground galaxy observed through substantial extin-tion. The object STS2013 92011 (Stutz et al. 2013) wasalso targeted by GO 14965. It is is shown by WFC3imaging to be an outflow knot.
V2475 Ori (MGM 2472) V2674 Ori (MGM 925) 1000 AU 1000 AU5:35:28.22 -04:58:37.80 5:36:23.75 -06:23:11.15
Figure E21 . Hubble
WFC3 images of two Class II ob-jects appearing incidentally in WFC3 observations of HOPSsources.F.
THE EFFECT OF THE ADOPTED DUST LAWON CAVITY MORPHOLOGYIn our modeling, we used the dust opacity modelsadopted by (Furlan et al. 2016). To investigate the roleof the assumed dust law on the observed morphology, wecompared images generated with two dust opacity mod-els from Ormel et al. (2011). The opacity model usedin this paper, "icsgra3," is described in Section 3 andadopts a grain coagulation time of 0.3 Myr. We comparethis to the opacity model "icsgra2" which in contrastsadopts a time of 0.1 Myr with consequently more grainsof smaller sizes. When comparing model protostars fromour grid generated with otherwise identical parameters,we observe that those using "icsgra2" show strongly limbbrightened cavity edge profiles and bright point sources(Figure F22). In contrast, the larger grains present in"icsgra3" result in more forward scattering where the in-tensity peaks toward the center of the cavity instead ofthe edges. The "icsgra3" are more consistent with
HST observations which typically show the cavities filled withemission (Figure 5), although there are some examplesthat show enhanced edges (Figure 13). This suggeststhat the larger grains in "icsgra3" are more represen-tative of our sample (Appendix A). Although beyondthe scope of this investigation, future studies of the ob-served cavity morphologies may provide new constraintson grain properties and their variations. G. COMPARISON BETWEEN SED MODELINGAND NEAR-IR MORPHOLOGIESMost of the protostars in this paper have been charac-terized in detail by Furlan et al. (2016) using modelingin concert with the SEDs of these objects. The mod-els used by these authors differ from those discussed inSection 3, and are fit to the SED from 1 . .
60 µm emission arethat our grid uses a finer sampling of high inclinationprotostars, a sparser grid of envelope densities, and adifferent cavity opening angle exponent (2 vs 1.5).Figure G23 shows histograms of the number of pro-0
Figure F22 . Two examples of a radiative transfer mod-els created from different dust opacity models and otherwiseidentical parameters. On the left, the "icgras3" dust law usedin this paper displays more forward scattering and less limbbrightening along the cavity edge. i )051015202530 N u m b e r Non-Detections
Class 0Class IFlatClass II 0.00.20.40.60.81.0 Cos( i )051015202530 N u m b e r Point Sources i )051015202530 N u m b e r Unipolar i )051015202530 N u m b e r Bipolar
Figure G23 . These four panels contain histograms of incli-nations from the SED fitting of Furlan et al. (2016), for aselection of four scattered-light morphologies. In each his-togram, the color indicates the classification scheme used byFurlan et al. (2016) tostars vs inclinations determined by SED fitting. Fourdifferent histograms are displayed, one each for bipolar,unipolar, point sources, and non-detections. (Irregularprotostars are not shown). Since the bins are chosento have equal intervals in the cosine of the inclination, arandom distribution should result in an equal number ofsources in each bin; however, the SED-determined incli-nation for the overall sample of HOPS protostars peakat 60–70°, suggesting that the SED derived inclinationsmay have systematic biases (Furlan et al. 2016). Thedistribution of inclinations for point sources is similar inthis respect to the overall sample (see Furlan et al. 2016,Figure 29), except at the highest inclinations. Obscura-tion by the disk likely accounts for this deficiency, bothby decreasing the ability to detect a point source and bydecreasing the contrast with the surrounding nebulos-ity. The unipolar and non-detections also peak around60–70°, although they show a deficiency of low inclina-tion objects, this is expected since the outflow cavitiescannot be detected at low inclinations the lower obscu-ration at these angles makes non-detections unlikely.Finally, the bipolar protostars show a broad rangeof inclinations, even though their observed morpholo-gies require a nearly edge-on perspective. Furlan et al.(2016) showed that there are large systematic uncertain-ties in the SED derived inclinations. This figure furtherdemonstrates the limitations of using SED derived in-clinations, particularly for edge-on protostars. In a de-tailed study of the
HST morphology of the HOPS 136protostar, Fischer et al. (2014) could only find agreementbetween the SED models and the edge-on morphologyby adding a low density component of dust in the out-flow cavity to increase the scattering at shorter wave-lengths. This suggests that our models are incompleteand therefore under-predict the brightness of protostarsin the near-IR; consequently, model fits erroneously fa-vor inclined models where the near-IR emission is lessabsorbed by the disk.Our measurements of the cavity half-opening anglescan also be used to test the angles derived from SEDmodels. Furlan et al. (2016) fitted models with discretecavity half-opening angles of 5, 15, 25, 35 and 45° forcavities with a r . power-law shape. The consistencyof the best fit cavity angle compared to the mode forvarious criteria of close models are shown in Figure 46of that work; these show there are a wide range of cav-ity angles that can be fit to a given SED. This is fur-ther demonstrated in Figure G24, where we comparehalf-opening angles inferred from the best SED fits fromFurlan et al. (2016) to the cavity half-opening angles de- Note that they use the terminology “cavity opening angle”where we use “cavity half-opening angle”. Half-Opening Angle from Near-IR Morphology ( ) H a l f - O p e n i n g A n g l e f r o m S E D () Figure G24 . Half-opening angles compared between thiswork and those in Furlan et al. (2016). The blue dottedline indicates equality in the two methods.. Half-opening angles compared between thiswork and those in Furlan et al. (2016). The blue dottedline indicates equality in the two methods.