The Rotating Molecular Structures and the Ionized Outflow Associated with IRAS 16547-4247
Ramiro Franco-Hernandez, James M. Moran, Luis F. Rodriguez, Guido Garay
aa r X i v : . [ a s t r o - ph . GA ] J un The Rotating Molecular Structures and the Ionized OutflowAssociated with IRAS 16547-4247
Ramiro Franco-Hern´andez , , James M. Moran , Luis F. Rodr´ıguez , and Guido Garay ABSTRACT
We present VLA 1.3 cm radio continuum and water maser observations aswell as SMA SO (226.300 GHz) and 1.3 mm dust continuum observations towardthe massive star formation region IRAS 16547-4247. We find evidence of multiplesources in the central part of the region. There is evidence of a rotating structureassociated with the most massive of these sources, traced at small scales ( ∼
50 AU)by the water masers. At large scales ( ∼ molecular emission with a barely resolved structure that can be modeled asa rotating ring or two separate objects. The velocity gradients of the masers andof the molecular emission have the same sense and may trace the same structureat different size scales. The position angles of the structures associated withthe velocity gradients are roughly perpendicular to the outflow axis observed inradio continuum and several molecular tracers. We estimate the mass of the mostmassive central source to be around 30 solar masses from the velocity gradientin the water maser emission. The main source of error in this estimate is theradius of the rotating structure. We also find water masers that are associatedwith the large scale molecular outflow of the system, as well as water masersthat are associated with other sources in the region. Our results suggest thatthe formation of this source, one of the most luminous protostars or protostellarclusters known, is taking place with the presence of ionized jets and disk-likestructures. Subject headings: stars: formation — stars: individual (IRAS 16547-4247) Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA [email protected] Centro de Radioastronom´ıa y Astrof´ısica, UNAM, Apartado Postal 3-72 (Xangari), 58089 Morelia, Mi-choac´an, M´exico. Departamento de Astronom´ıa, Universidad de Chile, Camino el Observatorio 1515, Las Condes, Santiago,Chile.
1. Introduction
Our present understanding of star formation is primarily based on observations of therelatively abundant low-mass stars. The theoretical framework for star formation (Shu etal. 1987; 1993, see also McKee & Ostriker 2007) has been successful in explaining theprocesses that occur in the formation of these low mass stars, processes that are inferredfrom multiwavelength observations (e.g., Lada 1991, Evans 1999). Key ingredients in thisscenario are the presence of a central protostar accreting from a circumstellar disk that issurrounded by an infalling envelope of dust and gas, as well as the presence of ionized jetsand molecular outflows that remove angular momentum and mechanical energy from theaccretion disk.The applicability of this paradigm to the formation of massive stars remains unproven.It is possible that massive stars are formed by processes that are radically different from thosethat produce low-mass stars, such as by the merging of lower mass protostars (Bonnell, Bate,& Zinnecker 1998). The role of the coalescence (Stahler, Palla, & Ho 2000) and accretion(Osorio, Lizano, & D’Alessio 1999, McKee & Tan 2002) processes in the assembling of amassive star is still under debate. If massive O stars are formed by accretion we expect thatdisks and jets will be present during their earliest stages of evolution. On the other hand,if they are formed through coalescence of lower-mass stars then neither disks nor jets areexpected since they would be disrupted during the merging process. For a recent review onthe competing ideas to explain massive star formation see Zinnecker & Yorke (2007).Water masers have been observed in association with massive star formation regions andeven though they have been studied for four decades (Cheung et al. 1969), their nature isstill not fully understood. There has been a lot of discussion on where in the star formationregion the physical conditions match those necessary for the excitation of the water masers.One idea is that the masers originate in a layer between the ionization and shock frontsin the expanding HII regions (e.g. Elitzur 1992). Another is that they are formed at theinterface of the molecular material with the jets and outflows emanating from the formingstars (e.g. Fuyura et al. et al. . × L ⊙ ),located at a distance of 2.9 ± et al. ∼ ′′ ) millimeter wavelengthobservations show that the IRAS source is associated with an isolated and dense molecularcore with a mass of 1 . × M ⊙ and a radius of 0.2 pc (Garay et al. 2003). Very LargeArray (VLA) and Australia Telescope Compact Array (ATCA) interferometric observationsof radio continuum at centimeter wavelengths show the presence of a thermal radio jet, 3 –located at the center of the core, and two lobes aligned and symmetrically separated fromthe jet by ∼ ′′ or ∼ ◦ (Garay et al. 2003; Rodr´ıguez et al. 2005). Inaddition, observations of H emission at 2.12 µ m reveal a chain of knots of shock-excited gasextending over 1.5 pc, and 11.9 µ m continuum observations show a compact object ( ≤ ′′ flow and the radio jetare closely aligned, suggesting that these phenomena trace the outflowing gas at differentdistances from the forming star.More recently Garay et al. (2007) observed the CO J = 3 → ◦ ) isslightly different from the position angle of the radio jet (P.A. = 167 ◦ ), suggesting that thejet axis is precessing. Additional evidence for precession has been presented by Rodr´ıguez etal. (2008). Garay et al. (2007) estimated an inclination for the outflow of i = 84 ± ◦ fromcomparison of the position-velocity diagram of the outflowing CO with the biconical modelsof Cabrit et al. (1988). The momentum and energy parameters they derived are consistentwith a massive young star driving the outflow. Also Garay et al. observed a strong signatureof large scale infall motions and derived an infall speed of ∼ − and a mass infall rateof ∼ × − M ⊙ yr − at a radius of ∼ LSR = −
34 km s − for the maser emission. Later Forster and Caswell (1989) made a brief VLA observation ofIRAS 16547-4247 for water masers. The angular resolution on their observations was enoughto separate the masers into a few groups located near the central radio continuum source.However, due to their short integration time ( ∼ . We also present new observations made with the SMA of theSO , − ,
12) transition at 226.300 GHz, as well as the 1.3 mm dust continuumemission. In section 2 we describe the observations, while in section 3 we present our results.In section 4 we discuss the data, and in section 5 we summarize our conclusions. The National Radio Astronomy Observatory is operated by Associated Universities Inc. under cooper-ative agreement with the National Science Foundation. The Submillimeter Array is a joint project between the Smithsonian Astrophysical Observatory and theAcademia Sinica Institute of Astronomy and Astrophysics and is funded by the Smithsonian Institution andthe Academia Sinica.
2. Observations
The VLA observations were taken on 2007 June 7, using the correlator in the observingmode 2AB. This allowed us to observe simultaneously the radio continuum and spectralline emission. The total bandwidth for the continuum was 25 MHz. For the spectral lineobservations we had a total of 64 channels with a resolution of 97.6 kHz or 1.3 km s − .These observations were taken in the A configuration, resulting in a beam with a FWHM of0. ′′ × ′′
07; P.A.=0.8 ◦ for ROBUST = 0 weighting (Briggs 1995). The data were calibratedusing the standard high frequency calibration procedures for the VLA as described in theAIPS Cookbook. The phase calibrator was J1717-398 which had a bootstrapped flux of 0.30 ± ′′ × ′′
97; P.A.=8 ◦ (for a weighting with ROBUST= 0), while the spectral resolution was 1.1 km s − . The calibration was performed using MIRand MIRIAD. Callisto was used for flux calibration and 3C279 for bandpass calibration. Thephase calibrator was 1745-290, with a bootstrapped flux of 3.15 Jy with a 20% accuracy.The continuum data at 1.3 mm were processed in MIRIAD using the task UVLIN in thelower sideband with 2 GHz bandwidth centered at 217.1 GHz. The continuum was thenself-calibrated in phase using CALIB in AIPS. The resulting calibration was then applied tothe SO line data.
3. Results3.1. 1.3 cm VLA observations
Since IRAS 16547-4247 is a rather southern source (-42 ◦ in declination) the VLA hadto observe through a large air mass during the whole observation run. This adversely af-fected the phase stability especially in poor weather. In the VLA observations presented byRodr´ıguez et al. (2005) the weather was not good and they used a self calibration techniqueto obtain high dynamic range maps. Although the self calibration largely improved thedynamic range, it did not improve the accuracy of the position of the source.We made a special effort to determine the source position accurately. To obtain a betterestimate for the position of the radio continuum we looked at the positions obtained fromobservations made in good weather where we could measure the position of the central brightradio continuum source. Rodr´ıguez et al. (2005) reported positions derived from ATCA 5 –obserations in 2003 February of α (2000) = 16 h m s , δ (2000) = − ◦ ′ ′′
64 at 6cm and α (2000) = 16 h m s , δ (2000) = − ◦ ′ ′′
48 at 3.6 cm. The phase calibratorused in these observations was 1616-52. From the VLA archives there is data taken on 1993January. The position measured from this epoch is α (2000) = 16 h m s , δ (2000) = − ◦ ′ ′′
88 at 3.6 cm with the phase calibrator 1626-298. We have a position from the newVLA observations from 2006 May 31 and June 8 (Rodr´ıguez et al. 2008), that, after beingconcatenated, give the position α (2000) = 16 h m s , δ (2000) = − ◦ ′ ′′
150 at 3.6cm with the phase calibrator 1626-298. Since the newest VLA data from 2006 has much moreintegration time than the snapshot from the archive we will just use the position from theformer data, and from the two ATCA positions we take the position at 3.6 cm because the 6cm data has lower angular resolution. We adopt as the final position estimate for the centralbright radio continuum source at centimeter wavelengths the average of the ATCA positionat 3.6 cm (Rodr´ıguez et al. et al. α (2000) = 16 h m s ± s , δ (2000) = − ◦ ′ ′′ ± ′′
17, wherethe errors quoted are one half the difference between the two observations used.We used self-calibration techniques to obtain a final image for the new observations at1.3 cm presented here. We asssume that the position of the peak 1.3 cm emission coincideswith our adopted position. Since the water masers were observed simultaneously with thecontinuum, their positions are also referenced to the same coordinates. It is worthwhile tonote that the relative positions between the water masers and the 1.3 cm continuum arevery accurate and independent of the absolute position adopted in the self-calibration. Theimage of the 1.3 cm continuum emission is shown in Fig. 1. The emission is dominatedby the thermal jet, for which we derive, from a Gaussian ellipsoid fit made using the taskJMFIT of AIPS, a total flux density of 10.9 ± ′′ ± ′′ × ′′ ± ′′
03 with PA of 177 ◦ ± ◦ . The position angle of the major axis isconsistent with that derived at longer wavelenghts (Garay et al. 2003, Rodr´ıguez et al. 2005,2008), indicating that at 7 mm we are tracing the ionized jet. The image shows two marginal(4- σ ) components to the south of the jet that require confirmation in deeper images.The distribution of the main features of the IRAS 16547-4247 region, including that ofthe different water maser groups is shown in Fig. 2. The parameters of the individual maserspots are listed in Table 1. It is clear that there are several groups of masers associated withdifferent radio continuum sources seen in the 3.6 cm continuum map from Rodr´ıguez et al. (2005). These groups are separated with horizontal lines in Table. 1. The strongest masers,in the group marked as g1 , are associated with the central and brightest radio continuumsource. Their radial velocities range from -25.3 km s − to -54.2 km s − . Most of the masersin the g1 group form a compact structure extending in the east-west direction (see Fig. 3).There is another clear group of masers denoted g2 in Fig. 2. This group is located to the 6 –north-west of the radio continuum peak and the maser radial velocities extend from -30.5km s − to -42.4 km s − . Most of the masers in the g2 group form a compact structure thatis shown in Fig. 4. We will discuss these two compact structures below. The SMA dust continuum map presented in Fig. 5 clearly shows that the emission at1.3 mm exhibits a morphology that looks like two partially resolved sources separated byabout 2. ′′
0. We fitted the emission to two gaussian ellipsoids with the AIPS task JMFIT.The parameters resulting from the fit (positions, flux densities, deconvolved angular sizes andposition angles) are given in Table 2. From the fit we find that, as expected from Figure 5,the eastern component is the brightest in the continuum. This component is also detected inseveral molecular lines (Franco-Hern´andez et al. in preparation). The total dust continuumflux is 1.03 Jy, split in 0.81 and 0.22 Jy for the eastern and western components, respectively.Following Chini et al. (1987), assuming a constant temperature of 300 K (appropriate fordust at 1000 AU from a 6 × L ⊙ source), optically-thin emission with a dust to gas ratioof 0.01, and a dust mass opacity of 1 cm g − at 1.3 mm, we calculate a total gas mass inthe double dust continuum source of ∼ M ⊙ , split into 4.7 and 1.3 M ⊙ for the strong andweak components, respectively.The western component is unresolved, while the deconvolved angular sizes (FWHM)obtained from the fit for the eastern component are 1. ′′ × ′′
84; P.A.= 107 ◦ . The stronger1.3 mm component can be interpreted as a flattened structure, approximately in the east-west direction with a size of ∼ ′′ ± ′′
15 fromthe main source, the centimeter source D is displaced by 1. ′′ ± ′′
03 from the main source.We conclude that there are at least three sources within 2 ′′ of the main source: the mainsource itself, the centimeter source D, and the west 1.3 mm source reported here.Finally, we note that the centimeter position adopted for the main source, α (2000) =16 h m s ± s δ (2000) = − ◦ ′ ′′ ± ′′
17, and discussed in Section 3.1, doesnot coincide within the errors with the position obtained from the 1.3 mm image (see Table2), α (2000) = 16 h m s ± s δ (2000) = − ◦ ′ ′′ ± ′′
04 and that thesepositions differ by ∼ ′′
87. We tentatively attribute this discrepancy to the use of different 7 –phase calibrators. To facilitate modelling of the region we assume that the SMA 1.3 mmpeak coincides with the VLA/ATCA 3.6 cm peak. The same offset is applied to the SMAmolecular data. observations We detected strong SO emission toward the dominant eastern dust component, but nottoward the weaker western component. Fig. 6 shows the first moment of the SO emission comes from a structure of ∼ emission. In Table 3 we listthese positions and they are plotted in Fig. 7. In this plot it can be seen that the velocitygradient is roughly perpendicular to the direction of the outflow observed in CO (Garay et al. et al. et al.
4. Discussion4.1. Water masers
In Fig. 3 we show the relative positions of the water masers in the compact structure ingroup g1 with respect to the radio continuum at 1.3 cm. It can be seen that the position ofthe peak of the radio continuum lies close to the position of the structure. From the lowerleft panel of Fig. 3 it is tempting to infer that the LSR velocity for the source is around -42km s − since this is the central velocity for this group of masers and would make them looklike a complete rotating ring with masers red and blueshifted with respect to this velocity.However, this velocity is 12 km s − blueshifted with respect to the LSR velocity measuredfrom the molecular lines. This difference is large compared with the radial dispersion velocityin young stellar clusters which is expected to be only a few km s − (e.g. ∼ − for thecenter of the Orion Nebula, Jones & Walker, 1988, as well as for Cyg OB2, Kiminki et al. g1 compact structure is at the LSR velocity of -30.6 kms − we can still interpret it as a rotating torus around the central source. However, inthis case we have emission coming from masers mainly blueshifted with respect to the LSRvelocity. The lack or weak emission from one side of the disk (blueshifted or redshifted) hasbeen observed in other sources (Val’Tts et al. − . For this fit we discard the maser at -52.9 km s − which is very noisy and seems to depart from the rest of the features. We obtain a slope of dV /dθ = -812 ±
71 km s − arcsec − and an intercept of -35 ± − . In the previousexpression V is the observed radial velocity of the maser at a measured projected angulardistance θ from the source (this distance is the component measured in the coordinatedefined by the semimajor axis of the ring). We also need to know the outer radius of thering. However, all we can obtain is a lower limit for the outer radius since we cannot tell ifthe last maser we see is coming from the edge of the ring or if there is material external tothis apparent last maser. Another uncertainty comes from the inclination of the ring withrespect to the line of sight. We will use the inclination given by Garay et al. (2007), i.e.the ring is almost perpendicular to the plane of the sky. With this in mind, we define theradius of the disk as the angular distance from the central source given by the fit to theslope for the highest radial velocity detected. For a velocity of -54.2 km s − , we obtain θ =0.024 ± M ⋆ = θ DG sin i (cid:16) d V d θ (cid:17) , (1)where θ is the ring radius, D is the distance to the source, and i is the inclination angle.Introducing the measured values we get a mass M ⋆ = 30 ± M ⊙ (cid:18) D . (cid:19) . (2)The error comes mainly from the uncertainties in the radius of the ring and the velocitygradient.We now briefly discuss the g2 compact structure of water masers. In Fig. 4 we showthe relative positions of the water masers in this structure. They distribute in an elongatedshape, approximately following the jet direction in that region. This suggests that thesemasers are tracing the outflow. However, the masers are blueshifted with respect to thesystemic velocity of the region, while the CO outflow is redshifted. There is also a strongvelocity gradient in the northernmost part of the structure, suggesting interaction withambient material. 9 – Sulfur-bearing molecules have been studied through millimeter and submillimeter ob-servations of star formation regions. They could account for a significant fraction of the totalflux coming from molecules in these regions (Schilke et al. et al. et al. is the product of reactions from molecules that have been evaporated off the dust grainssurfaces (Charnley 1997). There is evidence that the emission originates in outflows (e.g.Codella et al. et al. et al. et al. also has been observed to trace infall motions (e.g. W51; Sollins et al. transitions we obtain an independentestimate of the mass. In Fig. 7 we can see the position velocity diagram showing theposition of the emission peak in each velocity channel. This can be interpreted also as gasin a Keplerian motion in a ring around the central source. The estimate of the size of sucha ring will have the same uncertainties as described above for the water masers and we willhave again a lower limit for the mass estimate. For these data we get a velocity gradientof -8.8 ± − arcsec − , and an intercept of -31.0 ± − . The velocity of themost blueshifted detectable SO emission is -34.8 km s − . For this velocity, we obtain θ =0.43 ± M ⋆ = 22 ± M ⊙ (cid:18) D . (cid:19) , (3)where the errors are estimated in the same way that as for the water masers.Then, the Keplerian masses estimated from the water masers and from the SO , atphysical scales that differ by a factor of ∼
20, give consistent large masses for the centralstar(s). However, the SO data set has very limited angular resolution and we find that theapparent gradient seen in Fig. 7 can also be modeled as a Gaussian two-component model.From this fit, we find two components separated by 0. ′′ ± ′′
06 at a position angle of 109 ◦ ± ◦ ,and with a velocity difference of 2 . ± . − . These two components, if assumed to be ofnegligible mass and located symmetrically with respect to a central object with all the mass(that is not directly detected in our observations), imply a Keplerian mass of 1 . ± . M ⊙ ,much smaller that the mass derived from the continuous ring model. Alternatively, we canassume that the total mass of the system is distributed between the two components andin this case the Keplerian mass is 12 . ± . M ⊙ . Given the limitations of the data, it is 10 –very difficult to decide if the SO emission is coming from a continuous, ring-like structureor from two discrete molecular clumps. We have assumed that the high bolometric luminosity, L bol = 6 . × L ⊙ , associatedwith IRAS 16547-4247 comes mostly from an embedded, massive main sequence star. Thisassumption is justified since high mass objects are expected to quickly evolve to the mainsequence, even while accreting and while they are deeply embedded within the dusty core(Zinnecker & Yorke 2007).However, an alternative explanation is a lower mass object accreting at a very high rate.In this case the system would derive most of its luminosity from accretion. The accretionluminosity, L acc , is L acc = GMR ǫ ˙ M i , (4)where G is the gravitational constant, M is the mass of the star, R is the radius of the star,˙ M i is the infall rate determined from observations al large scales, and ǫ is the fraction of thislarge scale infalling gas that ends being accreted by the star. Assuming that the bolometricluminosity comes mostly from accretion, L acc ≃ L bol , and that from the observations of Garay et al. (2007) we have that ˙ M i = 1 × − M ⊙ yr − , we derive from Eqn. (4) a mass-radiusrelationship that in solar units is (cid:20) RR ⊙ (cid:21) = 5 . ǫ (cid:20) MM ⊙ (cid:21) . (5)If ǫ is larger than ∼ .
2, we obtain (
R/R ⊙ ) > ( M/M ⊙ ) and since in the main sequencewe expect ( R/R ⊙ ) ≃ ( M/M ⊙ ), one would have to conclude that the star is not in themain sequence and most probably is a lower mass object (than the mass value derived fromassuming a main sequence star) accreting at a very high rate and deriving a significantfraction of its total luminosity from accretion. It should be noted, however, that Hosokawa& Omukai (2009) have argued that massive protostars undergoing strong accretion will havestellar radii an order of magnitude larger than those occuring in the main sequence. Clearly,a better knowledge of ǫ and of the structure of protostars will help restrict these possibilitiesand better quantify the contribution of accretion to the total luminosity of forming massivestars. 11 –
5. Conclusions
Our main conclusions follow:1) We present VLA 1.3 cm radio continuum and water maser observations as well asSMA SO (226.300 GHz) and 1.3 mm dust continuum observations toward the massive starformation region IRAS 16547-4247. The 1.3 cm continuum traces the inner parts of thethermal jet in the region. The 1.3 mm dust continuum traces a double structure, withcomponent separation of ∼ ′′ , with each structure probably marking the position of a staror a stellar group.2) Water maser emission is present in several distinct parts in the region. The compactstructure in group g1 is closely associated with the thermal jet and shows an alignmentperpendicular to it. The masers in this group show a velocity gradient that, if interpretedas arising in a Keplerian ring, implies a mass of ∼ M ⊙ for the central star(s).3) The SO emission arises only from the brightest 1.3 mm dust continuum component.The line emission shows a velocity gradient that, if modeled as a Keplerian ring, gives a massof ∼ M ⊙ , consistent with the mass derived from the H O masers. However, the data canalso be fitted with a two-component model that gives smaller Keplerian masses.We thank an anonymous referee for comments that improved two sections of the paperand for the suggestion of discussing the possibility of significant accretion luminosity. R.F.H.is grateful for support from an SAO predoctoral fellowship. L.F.R. acknowledges the supportof CONACyT, M´exico and DGAPA, UNAM. G.G. acknowledges support from CONICYTprojects FONDAP No. 15010003 and BASAL PFB-06. 12 –
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This preprint was prepared with the AAS L A TEX macros v5.2.
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ARC SE C ARC SEC0.4 0.2 0.0 -0.2 -0.40.80.60.40.20.0-0.2-0.4-0.6-0.8
VLA1.3 cmg1 g2
Fig. 1.— VLA 1.3 cm continuum emission from the IRAS 16547-4247 central source. Theimage was made with ROBUST = 5 weighting. Contours are -4, -3, 3, 4, 5, 6, 8, and 10times 0.42 mJy beam − , the rms noise of the map. The half power contour of the beam(0. ′′ × ′′
09; 4 ◦ ), is shown in the bottom left corner. The peak position adopted for thissource is α (2000) = 16 h m s , δ (2000) = − ◦ ′ ′′
32. The main component ismarginally resolved and elongated along PA of 177 ◦ . The small crosses mark the positionsof the water masers in the compact structures located in groups g1 and g2 . 16 –Fig. 2.— Cartoon (not to scale) showing the different features and components of IRAS16547-4247. The stars mark the positions of water maser groups. 17 –Fig. 3.— Distribution in position and radial velocity of the compact structure of masers in g1 (Fig. 2). The upper left panel shows the positions of the masers with respect to the peakof the radio continuum at 1.3 cm. The upper right and lower panels are the position-velocitydiagrams for the same masers. The broken lines show the position of the radio continuumand the LSR velocity of the source in their respective axes. The positions have been rotated13 ◦ counterclockwise to make the ordinate parallel to the ionized jet. The errors in positionshown are ten times larger than the real values. 18 –Fig. 4.— Distribution in position and radial velocity of the compact structure of masers in g2 (Fig. 2). Panels are as in Fig. 3. A clear gradient can be seen to the north of the peak of radiocontinuum. Reference position is α ( J h m s , δ ( J − ◦ ′ ′′ ◦ counterclockwise to make the ordinate parallel to theionized jet. The errors in position shown are ten times larger than the real values. 19 – D E C L I NA T I O N ( J2000 ) RIGHT ASCENSION (J2000)16 58 17.6 17.5 17.4 17.3 17.2 17.1 17.0 16.9 16.8-42 52 020406081012
Fig. 5.— SMA 1.3 mm dust continuum emission from the IRAS 16547-4247 central source.Contours are -4, -3, 3, 4, 5, 6, 8, 10, 12, 15, 20 and 25 times 16 mJy beam − , the rms noiseof the map. The crosses mark the position of the two components obtained from the fit tothe image, whose parameters are given in Table 2. The square box marks the position finallyadopted for the peak 1.3 mm emission (see discussion in text). 20 – ARC SE C ARC SEC3 2 1 0 -1 -2 -3543210-1-2-3-4-5 -31 -30 -29
ARC SE C ARC SEC3 2 1 0 -1 -2 -3543210-1-2-3-4-5
Fig. 6.— The left panel shows the 1.3 mm dust continuum emission in color and the 3.6 cmfree-free radio continuum in contours. The color bar at the top shows the color coding forthe 230 GHz flux density in mJy beam − . Contour levels for the 3.6 cm emission are -5, 5,8, 10, 15, 20, 40, 60, 80, 100, 140, 180 times the rms noise level of 30 µ Jy beam − . The 3.6cm source at the lower left corner of the image most probably traces an independent starand is not associated with the jet (Rodr´ıguez et al. 2005). The right panel shows the firstmoment map of the 226.300 GHz SO transition in color and the radio continuum emissionat 3.6 cm with the same contours as in the left panel (Rodr´ıguez et al. 2005). The color barat the top shows the color coding for the LSR velocity of the gas in km s − . Note that thewestern component is not detected in the SO emission (right panel). The synthesized beamfor the 3.6 cm data is shown in the bottom left corner of each panel. The synthesized beamfor the 230 GHz data is 2.3 × ◦
21 –Fig. 7.— The upper left panel shows the positions of the SO (226.300 GHz) emission peaks,measured from each velocity channel and listed in Table 3. The positions are offsets withrespect to the peak of the dust continuum. The upper right and lower panels are the positionvelocity diagrams for the DEC and RA directions, respectively. 22 –Table 1. Parameters of individual water maser spotsV LSR α (J2000) ∆ α δ (J2000) ∆ δ Flux ∆Flux Continuum(km s − ) 16 h m (sec) − ◦ ′ (arcsec) (Jy) (Jy) Association a -12.1 17.46426 0.00043 16.4344 0.0018 0.37 0.01 S-1-13.4 17.46383 0.00029 16.4380 0.0013 0.50 0.01-14.7 17.46567 0.00011 16.4222 0.0005 1.79 0.01-16.0 17.46614 0.00006 16.4183 0.0002 8.69 0.03-17.4 17.46617 0.00005 16.4183 0.0002 11.94 0.04-18.7 17.46618 0.00005 16.4185 0.0003 5.17 0.02-20.0 17.46631 0.00014 16.4204 0.0006 1.05 0.01-21.3 17.46628 0.00009 16.4199 0.0004 1.87 0.01-22.6 17.46628 0.00009 16.4200 0.0004 1.62 0.01-23.9 17.46628 0.00023 16.4202 0.0011 0.60 0.01-27.9 17.36690 0.00469 10.1078 0.0066 0.04 0.03 B-30.5 17.39604 0.00215 10.1549 0.0102 0.50 0.07-31.8 17.39619 0.00083 10.1587 0.0037 1.50 0.08-33.2 17.39632 0.00050 10.1617 0.0023 1.72 0.06-34.5 17.39644 0.00090 10.1576 0.0041 0.62 0.03-37.1 17.41415 0.00095 09.8128 0.0183 0.43 0.04-38.4 17.37794 0.00123 10.0880 0.0052 0.20 0.02-39.7 17.37802 0.00008 10.0873 0.0004 2.73 0.01-41.1 17.37802 0.00004 10.0865 0.0002 5.99 0.02-42.4 17.37801 0.00004 10.0862 0.0002 4.27 0.01-43.7 17.37801 0.00022 10.0857 0.0010 0.71 0.01-18.7 17.22278 0.02314 08.4282 0.0450 0.08 0.03 Jet-20.0 17.21856 0.00050 08.4653 0.0021 0.31 0.01-21.3 17.21879 0.00030 08.4696 0.0013 0.64 0.01-27.9 17.22072 0.00064 08.4688 0.0027 1.85 0.07-29.2 17.22069 0.00015 08.4801 0.0006 9.79 0.09-30.5 17.22080 0.00010 08.4815 0.0005 12.96 0.08-37.1 17.21056 0.00969 08.2030 0.0106 1.49 0.13-29.2 17.22741 0.00068 07.9606 0.0030 2.66 0.10 Jet-30.5 17.22792 0.00003 07.9472 0.0001 36.83 0.07 23 –Table 1—ContinuedV LSR α (J2000) ∆ α δ (J2000) ∆ δ Flux ∆Flux Continuum(km s − ) 16 h m (sec) − ◦ ′ (arcsec) (Jy) (Jy) Association a -31.8 17.22794 0.00002 07.9463 0.0001 68.62 0.09-33.2 17.22800 0.00003 07.9450 0.0001 38.77 0.06-34.5 17.22906 0.00032 07.9280 0.0008 5.94 0.05-35.8 17.21846 0.01244 07.5844 0.0204 8.60 0.31-37.1 17.22580 0.00115 07.6553 0.0046 1.58 0.06-50.3 17.22169 0.00005 07.8103 0.0002 2.93 0.01-51.6 17.22173 0.00002 07.8109 0.0001 10.09 0.02-52.9 17.22173 0.00002 07.8115 0.0001 9.51 0.02-54.2 17.22169 0.00006 07.8124 0.0003 2.27 0.01-29.2 17.20965 0.00002 07.3098 0.0000 85.18 0.09 Jet-31.8 17.21571 0.00013 07.8589 0.0005 15.11 0.10-33.2 17.21588 0.00004 07.8572 0.0002 25.63 0.06-34.5 17.21453 0.00004 07.7631 0.0002 31.66 0.05-35.8 17.21287 0.00002 07.6567 0.0001 39.31 0.05-37.1 17.21284 0.00002 07.6550 0.0001 30.19 0.04-38.4 17.21275 0.00006 07.6365 0.0003 6.50 0.02-50.3 17.22121 0.00005 07.8130 0.0002 3.39 0.01 Jet-51.6 17.22114 0.00003 07.8134 0.0001 11.59 0.02-52.9 17.22113 0.00003 07.8135 0.0001 10.93 0.02-54.2 17.22112 0.00006 07.8135 0.0003 2.58 0.01-25.3 17.21011 0.00009 07.3292 0.0004 2.14 0.01 Jet ( g1 )-26.6 17.20985 0.00002 07.3261 0.0001 17.31 0.03-27.9 17.20958 0.00002 07.3286 0.0001 52.47 0.07-29.2 17.20936 0.00002 07.3309 0.0001 69.73 0.09-30.5 17.20909 0.00004 07.3316 0.0002 38.43 0.08-31.8 b b b b LSR α (J2000) ∆ α δ (J2000) ∆ δ Flux ∆Flux Continuum(km s − ) 16 h m (sec) − ◦ ′ (arcsec) (Jy) (Jy) Association a -41.1 17.21093 0.00011 07.3250 0.0005 2.38 0.02-42.4 17.21091 0.00009 07.3224 0.0004 2.27 0.01-43.7 17.21095 0.00007 07.3254 0.0003 2.39 0.01-45.0 17.21099 0.00010 07.3241 0.0004 1.48 0.01-46.3 17.21117 0.00019 07.3236 0.0008 0.813 0.01-47.6 17.21156 0.00016 07.3175 0.0006 1.08 0.01-48.9 17.21165 0.00011 07.3164 0.0005 1.56 0.01-50.3 17.21143 0.00015 07.3147 0.0006 1.49 0.01-51.6 17.21162 0.00058 07.3019 0.0021 1.07 0.03-52.9 17.21375 0.00280 07.2891 0.0081 0.989 0.05-54.2 17.21159 0.00104 07.3020 0.0041 0.294 0.01-30.5 b g2 )-31.8 17.19417 0.00070 07.0484 0.0025 6.58 0.14-33.2 17.19286 0.00041 07.0098 0.0016 4.86 0.08-34.5 17.19396 0.00074 07.0338 0.0027 2.58 0.06-35.8 17.19256 0.00073 06.9989 0.0030 1.69 0.06-37.1 17.19132 0.00029 06.9885 0.0012 2.60 0.04-38.4 17.19088 0.00007 06.9862 0.0003 3.60 0.02-39.7 17.19097 0.00005 06.9853 0.0002 4.63 0.01-41.1 17.19144 0.00006 06.9828 0.0002 4.49 0.02-42.4 17.19186 0.00008 06.9827 0.0004 2.42 0.01 a Radio continuum source (from Rodr´ıguez et al. b Spot not forming part of the compact structures discussed in the text. 25 –Table 2: Continuum components at 1.3 mm
Position a Total FluxComponent α (J2000) δ (J2000) Density (mJy) Deconvolved Angular Size b West 17.080 ± ± ± ≤ ′′ × ≤ ′′
5; + 45 ◦ ± ◦ East 17.247 ± ± ±
37 1. ′′ ± ′′ × ′′ ± ′′
33; + 107 ◦ ± ◦ a Units of right ascension are seconds with respect to 16 h m and units of declination are arcseconds withrespect to − ◦ b The values given are major axis × minor axis; position angle of major axis. For the east component we onlyobtained upper limits to the angular size.
26 –Table 3. Positions of the emission peak in each velocity channel of the SO data.V LSR α (J2000) ∆ α δ (J2000) ∆ δ (km s − ) 16 h m (sec) − ◦ ′′