Spitzer and near-infrared observations of a new bi-polar protostellar outflow in the Rosette Molecular Cloud
Jason E. Ybarra, Elizabeth A. Lada, Zoltan Balog, Scott W Fleming, Randy L. Phelps
aa r X i v : . [ a s t r o - ph . S R ] M a r Accepted for publication in the Astrophysical Journal
Preprint typeset using L A TEX style emulateapj v. 11/10/09
SPITZER AND NEAR-INFRARED OBSERVATIONS OF A NEW BI-POLAR PROTOSTELLAR OUTFLOW INTHE ROSETTE MOLECULAR CLOUD
Jason E. Ybarra and Elizabeth A. Lada Department of Astronomy, University of Florida, Gainesville, FL 32605
Zoltan Balog
Max-Planck-Institut f¨ur Astronomie, Heidelberg, Germany
Scott W. Fleming Department of Astronomy, University of Florida, Gainesville, FL 32605
Randy L. Phelps National Science Foundation, Office of Integrative Activities, Arlington, VA 22230
Accepted for publication in the Astrophysical Journal
ABSTRACTWe present and discuss
Spitzer and near-infrared H observations of a new bi-polar protostellaroutflow in the Rosette Molecular Cloud. The outflow is seen in all four IRAC bands and partiallyas diffuse emission in the MIPS 24 µ m band. An embedded MIPS 24 µ m source bisects the outflowand appears to be the driving source. This source is coincident with a dark patch seen in absorptionin the 8 µ m IRAC image. Spitzer
IRAC color analysis of the shocked emission was performed fromwhich thermal and column density maps of the outflow were constructed. Narrow-band near-infrared(NIR) images of the flow reveal H emission features coincident with the high temperature regions ofthe outflow. This outflow has now been given the designation MHO 1321 due to the detection of NIRH features. We use these data and maps to probe the physical conditions and structure of the flow. Subject headings:
ISM: jets and outflows — ISM: individual objects (MHO 1321) — methods: dataanalysis INTRODUCTION
Outflows and jets from young stellar objects (YSOs)accompany the early stages of star formation. Outflowscan manifest themselves as jets and knots of shockedmaterial visible at optical and near-infrared wavelengthsand also molecular emission observable at longer wave-lengths. The outflowing material plays a role in removingthe excess angular momentum from the YSOs allowingthem to evolve into stars. Outflows are able to tracethe history of mass loss and accretion of their drivingsources. Studying the structure and properties of theseflows may provide clues to understanding the connec-tion between jets and the associated wide angle molec-ular flows (Reipurth & Bally 2001). Additionally, thisoutflowing material interacts with its surroundings andmay affect its environment, possibly regulating furtherstar formation and cluster evolution. The energy andmomentum inputted by outflows may disrupt the sur-rounding ambient gas, contribute to the turbulence inthe cloud, and affect chemical processes (Bally 2007). [email protected]fl.edu Visiting astronomer, Cerro Tololo Inter-American Observa-tory, National Optical Astronomy Observatory, which are oper-ated by the Association of Universities for Research in Astron-omy, under contract with the National Science Foundation. This material is based on work supported by the NationalScience Foundation. Any opinion, findings, and conclusion orrecommendations expressed in this material are those of the au-thor and do not necessarily reflect the views of the NationalScience Foundation
Ybarra & Lada (2009) developed a technique to studythe thermal structure of shocked H gas using color anal-ysis of observations from the Spitzer
InfraRed ArrayCamera (IRAC). Given the vast amount of
Spitzer dataavailable, this technique can be used to survey large re-gions and simultaneously find and analyze shocked emis-sion. The IRAC color analysis enables the constructionof temperature maps of the shocked gas which may inturn be used to probe the interaction of outflow withits surroundings. These maps may also be used to com-pare the properties of outflow with those of simulationsallowing a better understanding of the physics involvedand estimating the energy and momentum inputted byoutflows into their environment.The Rosette Molecular Cloud (RMC) is a star form-ing region located at a distance of 1.6 kpc. Near-infrared imaging studies have revealed nine embed-ded clusters across the cloud (Phelps & Lada 1997;Rom´an-Z´u˜niga et al. 2008). Outflow activity in thecloud has been revealed through the [S II ] narrowbandimaging survey of Ybarra & Phelps (2004) and the COsurvey of Dent et al. (2009). In an analysis of the
Spitzer
IRAC images of the Rosette Molecular Cloud, we havediscovered a structure with the morphology of a bipo-lar outflow that is visible in the images from all fourIRAC bands. This structure can be seen in the imagespublished by Poulton et al. (2008) although it is not dis-cussed in their paper.In this study we analyze the outflow using near infrared Ybarra et al.(NIR) narrowband imaging of the flow to confirm thepresence of shocked gas inferred from analysis of the theIRAC images. We improve the IRAC color analysis ofYbarra & Lada (2009) and use it to create temperatureand column density maps of the outflow. Using both theNIR and IRAC data, we probe the physical conditionsand structure of the outflow. OBSERVATIONS AND DATA REDUCTION
Spitzer IRAC and MIPS data reduction
We used MIPS 24 µ m and IRAC 3.6-8.0 µ m datafrom program 3391 (PI: Bonnel) available in the Spitzer archive. The IRAC frames were processed using theSpitzer Science Center (SSC) IRAC Pipeline v14.0,and mosaics were created from the basic calibrateddata (BCD) frames using a custom IDL program (seeGutermuth et al. (2008) for details). The MIPS frameswere processed using the MIPS Data Analysis Tool(Gordon et al. 2005).
Near-Infrared H observations and data reduction Near-Infrared, narrow-band observations of the out-flow were obtained with the Infrared Side Port-Imager(ISPI) on the Blanco 4 meter telescope at the CerroTololo Inter-American Observatory (CTIO). ISPI em-ploys a 2048 × × ∼ ′′ pixel − . The outflow was imaged using the H − µ m filter ( λ c = 2.0336 µ m, ∆ λ/λ = . − µ m filter ( λ c = 2.1262 µ m, ∆ λ/λ = . cont filter centered at 2.1462 µ m. The telescope wasdithered with a 20 point dither pattern with a integra-tion time of 60s at each dither position. The images weretaken on the nights of 2008 December 17 and 2008 De-cember 19 with total integration time of 40 minutes ineach filter.The raw images were flat fielded, corrected for bad pix-els, and linearized using the task osiris from the CTIOInfrared Reduction package. For each image, a sky framewas created by median combining the dithered imagesclosest in time to the image. The IRAF tasks msctpeak and mscimage , which are part of the IRAF Mosaic DataReduction Package, mscred , were used to correct the im-ages for geometric distortions. The high order polyno-mial distortion terms were calculated with msctpeak us-ing the 2MASS Point Source Catalog as the referencecatalog and the distortion correction was applied with mscimage . The corrected images were aligned and thencombined to form the final science images. RESULTS AND ANALYSIS
Figure 1 shows the outflow in all four IRAC bands.The outflow appears as patchy regions of diffuse emissionwith an overall structure that is elongated and collimatedin the E-W direction. Figure 2 shows the narrowbandnear-infrared emission images of the outflow. The NIRH knots coincide with the diffuse emission seen in theIRAC images. The NIR H images confirm the presenceof shocked gas and the interpretation that this structureis an outflow. The eastern end appears to truncate ata bow shock. Slightly west of the bow shock, the H images reveal a small scale chaotic structure followed by amore linear chain of knots.The western end of the outflow Table 1
Positions and flux estimates for the NIR H knots of MHO 1321Knot R.A. (J2000) Dec (J2000) H ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± Note . — Flux is in units of 10 − W m − . Aperture radiusused is 7 pixels. Flux uncertainty includes calibration uncertainty appears slightly deflected northward followed by a brightknot (g) and then a complex structure of smaller knots.The NIR images were flux calibrated to the 2MASS Ksband by determining the magnitude difference betweenthe 2MASS Ks band catalog values and the ISPI imagemagnitudes for stars in common. The zero point flux ineach NIR image after calibration is then the filter band-width multiplied by the 2MASS Ks-band zero point fluxdensity. This results in a relation between the countssec − in each filter image and the flux in W cm − . Thenarrow band continuum K c images were scaled and sub-sequently subtracted from the H line images. Figures 2cand 2d show the continuum subtracted H µ m and H µ m line images. The qualityof the subtraction is good although there are some sub-traction residuals from the brightest stars present in thesubtracted images due to differences in wavelength andPSF combined with changing atmospheric conditions.Based on the observation, this outflow has been giventhe designation MHO 1321 in the Catalogue of Molec-ular Hydrogen Emission-Line Objects (MHOs) in Out-flows from Young Stars (Davis et al. 2009). The fluxesof the individual H knots comprising this outflow weredetermined using a circular aperture on the continuumsubtracted images. Table 1 lists the NIR fluxes of the H emission knots. The flux uncertainty is composed of therms background, poisson noise, and uncertainty from theflux calibration. IRAC color space of shocked gas
In order to study the structure of the shocked gas,we applied the IRAC color analysis method developedby Ybarra & Lada (2009). We improved the coloranalysis method by including the effects of CO ν =1–0 band emission in the total emission of the shocked MHO catalogue is hosted by the Joint Astronomy Centre,Hawaii. pitzer and near-infrared observations of a new bi-polar outflow in the RMC 3
Figure 1.
Spitzer IRAC images of the outflow. The origin is set at ( α , δ )(J2000) = (06 h m . s
0, +03 ◦ ′ ′′ ) Figure 2.
Near-infrared images of the outflow: a) H µ m line, b) K cont , c) continuum subtracted H µ m,d) continuum subtracted H µ m. The horizontal scale is in arcminutes and the vertical scale is in arcseconds. The origin isset at ( α , δ )(J2000) = (06 h m . s
0, +03 ◦ ′ ′′ ) gas. The distribution of the population of pure rota-tional levels of CO due to collisional excitation withH , H, and He was calculated using the rate coef-ficients of Draine & Roberge (1984). We employedthe method of Gonz´alez-Alfonso et al. (2002) to cal-culate the relative rotational population for the CO ν =1 vibrational level. The Einstein A-values for theCO ν =1–0 rovibrational transitions were obtained us-ing the oscillator strengths of Hure & Roueff (1993).In our calculations, we set n H = n (H) + 2 n (H ), n (He) /n H = 0 . n (CO) /n H = 7 × − . Thefraction of atomic to molecular hydrogen was estimatedby considering the rate of collisional dissociation byH atoms, R d = 1 . × − exp( −
52 000 /T ) cm s − (Le Bourlot et al. 2002) and the rate of formation ongrains, R f = 3 . × − T − . cm s − , derived from Hollenbach & McKee (1979) with the cooling rates forH and H O (Le Bourlot et al. 1999, 2002).Figure 3 shows the location of shocked gas in IRAC[3.6]–[4.5] versus [4.5]–[5.8] color space for maximumshock temperature of T max = 6 × K for gas temper-atures T = 1500 − n H = 10 − cm − . The square brackets refer to IRAC magnitudes.The post-shock fraction of atomic hydrogen was found tobe n (H) /n H ∼ − × − which is consistent with sim-ulations of non-dissociative C-shocks (Wilgenbus et al.2000). In the simulations by Wilgenbus et al. (2000) itwas found that the atomic fraction is relatively constantover a wide range of maximum temperatures. Thereforewe will assume our color space to be representative ofnon-dissociative C-shocks in general. The location of theshocked emission in IRAC color space depends on the Ybarra et al. Figure 3.
IRAC color-color plot indicating the region occupiedby shocked gas composed of H and CO for T max = 6 × K gas density, fraction of atomic hydrogen, and the kinetictemperature of the gas. The [4.5]–[5.8] color is stronglydependent on temperature, while the [3.6]–[4.5] color hasa strong dependence on the atomic hydrogen density.At high densities, the dependence on density decreasesas the H gas moves toward local thermal equilibrium(LTE). The slope of the reddening vector is similar tothe approximate slope of the constant temperature lines.Thus temperature maps of high extinction regions re-main accurate even if the extinction cannot be accountedfor. However, unless extinction can be corrected for, ac-curate density information may not be attainable.We fit an analytic form to the relationship betweencolor and temperature for the non-dissociative case, T = 4 . − . . − [4 . − . . − [5 . . . − [4 . + 0 . . − [5 . where T = T / in the color space defined by 2 . > [3 . − [4 . > − . . − [5 . .
5, and − . < [4 . − [5 . < .
0. The difference between the analytic fit andthe calculated temperature-color relation over the de-fined range is less than 10%. Additionally, one can usethe flux in the 3.6 µ m image to estimate the columndensity of the shocked H . Using our calculations we fitthe following analytic form to the relationship betweencolumn density, IRAC 3.6 µ m flux density, and temper-ature, log( N H /F . ) = 23 . − . T + 0 . T − . T − . n + 0 . n T where N H is the column density of shocked H in cm − , F . is the IRAC 3.6 µ m band flux density in units ofMJy sr − , and n = n H / for 1 . < T < . < n < T max = 1 × K. Our calculations show signif-icant dissociation of H with increasing density. Figure4 shows the IRAC color space for dissociatively shockedgas. As the molecular hydrogen gets dissociated, emis-sion from the CO ν =1–0 band begins to dominate the4.5 µ m IRAC channel.The relationships between temperature, density andcolor are different for the case of the non-dissociativeshock and the case of the dissociative shock. There is Figure 4.
IRAC color-color plot indicating the region occupiedby dissociatively shocked gas composed of H and CO some degeneracy at the low density and low dissociationregion of color space for the dissociative shock and atthe high density non-dissociative shock region. Thesetwo models meet in a region of color space defined byH gas in LTE. Although there is degeneracy, we expectthe distribution in color space for the dissociative shockto primarily lie at [4.5]–[5.8] <
0. Thus we define thedomain of the dissociative shocked gas in color space tobe [4.5]–[5.8] < > .
5, whereas we definethe color domain of non-dissociate gas to lie primarilyat [4.5]–[5.8] >
0. By analyzing the color distribution ofan outflow, it may be possible to distinguish betweenthe cases. A pixel density distribution, produced frombinning the colors of each pixel in the the outflow, canreveal the nature of the outflow by showing where mostof the pixels lie in color space.It should be noted that the IRAC color analysis as-sumes dust and PAH emission is negligible. In orderto prevent dust emission from affecting the color anal-ysis, the 8 µ m IRAC color is not used as there is evi-dence in some shocks of continuum dust emission withinthat wavelength range covered by the 8 µ m channel (eg.Smith et al. 2006). Additionally, PAHs are very likelydestroyed in shocks. In a recent study, Micelotta et al.(2010) show that strong shocks can destroy PAHs orseverely denature them. IRAC color analysis of MHO 1321
The IRAC 8 µ m image of the outflow region revealspatches of absorption against the diffuse background(Figure 1). Of particular interest is a dark patch seenin absorption that bisects the outflow. We created anextinction map from the 8 µ m data using a small scalemedian filter assuming a uniform background. We ap-plied this extinction map to the images of the outflowregion using the mid-infrared reddening law (KP, v5.0)of Chapman et al. (2009). However, this is not able toaccount for the total extinction in the line of sight towardthe outflow. Nonetheless, the temperature-color relationis insensitive to extinction for non-dissociative shocks.We estimate the background using a ring median filterand subsequently remove this background from the IRAC3.6 µ m, 4.5 µ m, and 5.8 µ m images. A ring median filteris a median filter from which only the pixels within anannulus are used in calculating the median (Secker 1995).The scale of this filter needs to be larger than the scaleof the shocked emission otherwise the background will beoverestimated, yet small enough to account for the largepitzer and near-infrared observations of a new bi-polar outflow in the RMC 5 Figure 5.
Contours indicate the pixel density in IRAC color spaceof the outflow knots. The distribution of pixels and the lack ofpixels in the CO dominated region indicate non-dissociative shocks. scale background fluctuations. The images were shiftedand registered with each other and then IRAC colors ateach pixel location were determined. Figure 5 shows thepixel density in IRAC color space for the knots of theoutflow. Due to the lack of pixels whose colors are inor near the CO dominated region and our criteria abovefor non-dissociative shocks, we conclude that this shockis mostly non-dissociative and we can therefore estimatethe thermal structure based on color analysis. We com-pared the colors to those of non-dissociative shocked gaswith the cutoff [4.5]–[5.8] ≤ knots are spatiallycoincident with the high temperature regions of the flow.However, knots a and v do not have a correspondingIRAC derived temperature. The NIR images reveal starsin the line of sight for these knots which add to theemission and prevents IRAC color analysis from deriv-ing temperatures. Seven of the knots have estimatedtemperatures greater or equal to 3 × K. By combin-ing the NIR infrared and temperature data it is pos-sible to estimate the extinction towards the brightestknots. For this we used the extinction cross-sections ofWeingartner & Draine (2001). The median extinction tothe knots is A v = 27. The knots j and k in the vicin-ity of the dark clump have higher extinction comparedto the rest of the knots. We use the median extinctionvalue to de-redden the 3.6 µ m flux and use it create acolumn density map with our column density tempera-ture relation. Figure 7 show the column density mapof shocked H in the flow. We find that there is also acorrespondence between the NIR H knots and regionsof higher column density. Using the established distanceto the RMC of 1.6 kpc and the column density map wecalculate the total mass of the shocked H (T > . × g ( ∼ × − M ⊙ ). Outflow Source
The source of the outflow is not seen in the NIR nor inthe IRAC images. However, inspection of the MIPS 24 µ m image reveals a source (( α , δ )(J2000) = (06 h m . s ◦ ′ ′′ )) bisecting the outflow (Figure 8). Moreover,this source is spatially coincident with a dark patch seenin the 8 µ m image. This patch is elongated nearly per-pendicular to the outflow and the northwest part of it has Table 2
IRAC color analysis of H knotsKnot T (10 K) N H2 (10 cm − )b 2.5 ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± Note . — The estimated temperature is the column density av-eraged temperature determined from pixel colors within each aper-ture. The temperature uncertainty is the column density weightedstandard deviation of the temperatures corresponding to the indi-vidual pixels. the morphology of an outflow cavity. The dark patch isseen in the contours that indicate mass surface densitiesobtained through extinction mapping of the 8 µ m imag-ing data by the method of Butler & Tan (2009). Thecontour levels correspond to mass surface densities of Σ= (2.5, 4.0, 5.0, 6.0) × − g cm − . This small cloudmay be a remnant of the core from which the protostarformed. The morphology of the northern end of the cloudappears as a bi-polar outflow cavity with an opening an-gle θ ∼ ◦ − ◦ . H µ m image that bisect theMIPS source and a coincident with the cavity of the darkcloud. This source is also detected in the MIPS 70 µ mand MIPS 160 µ m imaging data. However, we are unableto estimate the flux in the MIPS 70 µ m band image dueto incomplete coverage and possible contamination fromthe adjacent knot (j) which may have emission from dustand the 63 µ m [O I ] line (Reipurth & Bally 2001). Sim-ilarly, the MIPS 160 µ m band image may include emis-sion from the knot in addition to the source. This sourceis not detected at shorter wavelengths and thus can beclassified as a Class 0 protostar. We propose this newlydiscovered protostar to be the source of the outflow. Ad-ditionally, using the column density map, we find thatthe mass of the shocked H to the east (1 . × g) ofthis source is almost equal to the mass west of the source(1 . × g) .Faint extended 24 µ m emission is also detected at thelocations of the brightest H knots (g & j). This mayarise from fine-structure [Fe II ] lines within the MIPS24 µ m band (Velusamy et al. 2007). This is consistentwith our IRAC color analysis of these knots that revealthem to be high temperature regions ( T ≥ . × K).This consistency between the IRAC color analysis andthe MIP 24 µ m emission validates our usage of the colorspace for non-dissociative shocks. Ybarra et al. Figure 6.
Thermal map of the outflow based on color analysis of the IRAC data. The contour levels indicate T = 1500 K, 2500 K, 3000K, 4000 K. The origin is set at ( α , δ )(J2000) = (06 h m . s
0, +03 ◦ ′ ′′ ) Figure 7.
Column density map for H of the outflow based on color analysis of the IRAC data. The contour levels indicate N H =2 × cm − , 5 × cm − , 1 × cm − , 2 × cm − . The origin is set at ( α , δ )(J2000) = (06 h m . s
0, +03 ◦ ′ ′′ ) Figure 8.
MIPS 24 µ m image of the outflow sources. The greencontours show the dark cloud that bisect the outflow and indi-cate the Σ values (2.5, 4.0, 5.0, and 6.0) × − g cm − obtainedthrough extinction mapping using the IRAC 8 µ m imaging data(Butler & Tan 2009). The blue contours are H − × − W m − sr − . The H contours reveal the location of theoutflow. The scale of the image axes is in arcseconds. The originis set at ( α , δ )(J2000) = (06 h m . s
0, +03 ◦ ′ ′′ ) DISCUSSION
Structure of the outflow
The long axis of the flow extends to 3.3 ′ . With a dis-tance of 1.6 kpc to the RMC, the flow would have aprojected total length of 1.5 pc. The east lobe extends2.3 ′ from the MIPS source to the bow shock, while thewest lobe extends only 1 ′ . Assuming a projected outflowvelocity of 100 km s − , using the east lobe we estimatethe age of the outflow to be 10 years. This age is consis- tent with the typical age of a Class 0 source and thus thisoutflow may provide an accretion record of the protostar(Reipurth & Bally 2001). We can estimate the mass fluxof the outflow as ˙ M ∼ M (H ) v t l t where v t is the pro-jected outflow velcocity and l t is the projected outflowlength. Assuming the typical value of v t = 100 km s − and using the values for the H mass and length of theeast lobe, we estimate a mass flux of ˙ M ∼ − M ⊙ yr − . This value is consistent with those obtained from otheroutflows using spectroscopic data (Podio et al. 2006).The NIR H data reveals the higher temperature re-gions of the outflow seen in the IRAC images. The IRACimages also show the cooler regions of the flow as theIRAC bands contain pure rotational H lines in additionto ν = 1–0 and ν = 2–1 ro-vibrational lines.The flow is spatially coincident with two lobes of highvelocity CO gas observed by Dent et al. (2009). Simi-lar to many HH flows which extend further than theirCO counterpart, we find the eastern half to extend be-yond the the eastern CO lobe. The east end of the H flow ends in a large bow shock, while the west end re-veals a complex structure resembling either a broken upbow shock or multiple smaller bow shocks. Although theoutflow is linear on large scales, the IRAC and H datareveal a region in the eastern lobe before the bow shockwith a more chaotic structure. This deviation from alinear progression of knots may be due to a possible in-teraction with another outflow. The CO observationsof Dent et al. (2009) reveal another flow in the NE-SWdirection originating from the embedded cluster PL07(Phelps & Lada 1997) that points toward this region. Acollision between the two flows may explain the morphol-ogy and high temperature of knot r. The distribution ofknots may also be due to variations in in jet directionover time and thus an indication of jet precession. Deflection of the Outflow pitzer and near-infrared observations of a new bi-polar outflow in the RMC 7The western end of the outflow appears slightly bentnorthward. The outflow is deflected by an angle θ d = 20 ◦ where it appears to graze the densest region within thedark patch. The deflection angle remains small and ap-pears to decrease slightly beyond the interaction region.This is consistent with the simulations by Baek et al.(2009) of outflows colliding with dense cloud cores wherethe impact parameter is large. The deflection of the out-flow may explain why the western end of the flow isshorter than the eastern end as the outflow velocity isexpected to decrease after the collision (Raga & Canto1995). This is consistent with the IRAC color analysisthat reveals high temperature shocked gas (knot j) to theeast of the collision.If the outflow is composed of episodic ejection of ma-terial, there may be collision between clumps of mate-rial moving through the flow due to the velocity change(Raga & Cant´o 2003). As these successive clumps collidethey may give rise to the high temperature and high col-umn density region (g) found slightly west of the deflec-tion. This interaction may also explain why the westernlobe lacks the bow shock structure seen in the easternend. CONCLUSIONS
We present the discovery of a new bi-polar outflowin the Rosette Molecular Cloud and use NIR narrow-band and Spitzer imaging data to study the flow. Weshow that IRAC color analysis can be used to interpretthe interaction of an outflow with its surrounding envi-ronment. Using our calculations of the IRAC space ofnon-dissociative shocked gas we fit analytic forms to thecolor-temperature and column density-temperature rela-tionships. We verify that IRAC color analysis can revealregions of shocked gas and find that the NIR H knotscorrespond to regions of high temperature and or col-umn density determined through color analysis. We finddiffuse MIPS 24 µ m emission, most likely from [Fe II ]lines, to be coincident with regions of high temperaturethus confirming the validity of using the non-dissociativeshock IRAC color space The NIR line ratios combinedwith the temperature estimates allow for the determina-tion of extinction along the line of sight which is used tocreate a column density map of the shocked H gas. Wededuce that the asymmetry in the outflow is due to inter-actions with the dense material to the west of the outflowsource causing deflection and possibly deceleration of theoutflowing material.We thank Mike Butler for running his extinction map-ping code on the IRAC data and providing the masssurface density data shown in Figure 8. We thank theCTIO Blanco-4m observatory support scientists and staff including Nicole van der Bliek, Hernan Tirado, and Al-berto Alvarez. We thank our referee, John Bally, for hisuseful comments and suggestions. This work is based inpart on archival data obtained with the Spitzer SpaceTelescope, which is operated by the Jet Propulsion Lab-oratory, California Institute of Technology under a con-tract with NASA. Support for this work was providedby an award issued by JPL/Caltech and also a NASALTSA Grant NNG05GD66G. JY acknowledges supportby a Florida Space Grant Fellowship from NASA throughthe Florida Space Grant Consortium. Facilities: