The BLAST View of the Star Forming Region in Aquila (ell=45deg,b=0deg)
Alana Rivera-Ingraham, Peter A. R. Ade, James J. Bock, Edward L. Chapin, Mark J. Devlin, Simon R. Dicker, Matthew Griffin, Joshua O. Gundersen, Mark Halpern, Peter C. Hargrave, David H. Hughes, Jeff Klein, Gaelen Marsden, Peter G. Martin, Philip Mauskopf, Calvin B. Netterfield, Luca Olmi, Guillaume Patanchon, Marie Rex, Arabindo Roy, Douglas Scott, Christopher Semisch, Matthew D. P. Truch, Carole Tucker, Gregory S. Tucker, Marco P. Viero, Donald V. Wiebe
aa r X i v : . [ a s t r o - ph . GA ] J a n Draft version October 29, 2018
Preprint typeset using L A TEX style emulateapj v. 11/10/09
THE BLAST VIEW OF THE STAR FORMING REGION IN AQUILA ( ℓ = 45 ◦ , b = 0 ◦ ) Alana Rivera-Ingraham, Peter A. R. Ade, James J. Bock,
Edward L. Chapin, Mark J. Devlin, Simon R. Dicker, Matthew Griffin, Joshua O. Gundersen, Mark Halpern, Peter C. Hargrave, David H. Hughes, Jeff Klein, Gaelen Marsden, Peter G. Martin,
Philip Mauskopf, Calvin B. Netterfield,
Luca Olmi,
Guillaume Patanchon, Marie Rex, Arabindo Roy, Douglas Scott, Christopher Semisch, Matthew D. P. Truch, Carole Tucker, Gregory S. Tucker, Marco P. Viero, Donald V. Wiebe Draft version October 29, 2018
ABSTRACTWe have carried out the first general submillimeter analysis of the field towards GRSMC 45.46+0.05,a massive star forming region in Aquila. The deconvolved 6 deg (3 ◦ × ◦ ) maps provided by BLASTin 2005 at 250, 350, and 500 µ m were used to perform a preliminary characterization of the clumppopulation previously investigated in the infrared, radio, and molecular maps. Interferometric COR-NISH data at 4.8 GHz have also been used to characterize the Ultracompact H II regions (UCH ii Rs)within the main clumps. By means of the BLAST maps we have produced an initial census of thesubmillimeter structures that will be observed by
Herschel , several of which are known Infrared DarkClouds (IRDCs). Our spectral energy distributions of the main clumps in the field, located at ∼ T ∼ ∼ M ⊙ for a dustemissivity index β = 1 .
5. The clump evolutionary stages range from evolved sources, with extendedH II regions and prominent IR stellar population, to massive young stellar objects, prior to the forma-tion of an UCH ii R. The CORNISH data have revealed the details of the stellar content and structureof the UCH ii Rs. In most cases, the ionizing stars corresponding to the brightest radio detections arecapable of accounting for the clump bolometric luminosity, in most cases powered by embedded OBstellar clusters.
Subject headings:
ISM: clouds — balloons — stars: formation — submillimeter INTRODUCTION
The study of the earliest stages of star formation is in-trinsically connected to the ability to probe the dusty re-gions within which stars are born. The short wavelengthradiation from deeply embedded young stellar objects isabsorbed by the dust and reaches the observer as re-processed far infrared (FIR) and submillimeter (submm)emission. The low optical depth at these longer wave- Department of Astronomy & Astrophysics, University ofToronto, 50 St. George Street, Toronto, ON M5S 3H4, Canada Department of Physics & Astronomy, Cardiff University, 5The Parade, Cardiff, CF24 3AA, UK Jet Propulsion Laboratory, Pasadena, CA 91109-8099, USA Observational Cosmology, MS 59-33, California Institute ofTechnology, Pasadena, CA 91125, USA Department of Physics & Astronomy, University ofBritish Columbia, 6224 Agricultural Road, Vancouver, BCV6T 1Z1,Canada Department of Physics and Astronomy, University of Penn-sylvania, 209 South 33rd Street, Philadelphia, PA 19104, USA Department of Physics, University of Miami, 1320 CampoSano Drive, Carol Gables, FL 33146, USA Instituto Nacional de Astrof´ısica ´Optica y Electr´onica(INAOE), Aptdo. Postal 51 y 72000 Puebla, Mexico Canadian Institute for Theoretical Astrophysics, Universityof Toronto, 60 St. George Street, Toronto, ON M5S 3H8, Canada Department of Physics, University of Toronto, 60 St.George Street, Toronto, ON M5S 1A7, Canada University of Puerto Rico, Rio Piedras Campus, PhysicsDept., Box 23343, UPR station, San Juan, Puerto Rico Istituto di Radioastronomia, Largo E. Fermi 5, I-50125,Firenze, Italy Laboratoire APC, 10, rue Alice Domon et L´eonie Duquet75205 Paris, France Department of Physics, Brown University, 182 Hope Street,Providence, RI 02912, USA lengths makes submm studies the best tool to investigatethe clumps and inner cores ( ∼ − . µ m. The Galac-tic (e.g., Netterfield et al. 2009) and extragalactic (e.g.,Devlin et al. 2009) data provided by the BLAST missiondemonstrate the exciting science to be continued with the Herschel Space Observatory (hereafter Herschel ; e.g.,Elia et al. 2010) and its SPIRE instrument (Griffin et al.2009; 18 ′′ at 250 µ m).In this study we present a preliminary analysis of the6 deg field of a massive star forming region in Aquila( ℓ = 45 ◦ , b = 0 ◦ ), observed by BLAST during its 2005flight. This work therefore complements the analysis ofthe other BLAST05 Galactic plane star forming regions,including Vulpecula (Chapin et al. 2008) and Cygnus X(Roy et al. in preparation).Aquila is well known for its prominent massive starformation (e.g., Rathborne et al. 2004), and is domi-nated by two main molecular complexes. These arehost to numerous Ultracompact H II regions (UCH ii Rs;e.g., Wood & Churchwell 1989; [WC89]), maser emis-sion, and outflows from young and highly embeddedOB stellar clusters. The stellar activity of the Galac-tic Ring Survey Molecular Cloud (GRSMC) 45.60+0.30 Rivera-Ingraham, A. et al.has been extensively studied in the infrared and radio(e.g., Kraemer et al. 2003; Vig et al. 2006). However, al-though submm data have also been used to complementthe detailed study of this cloud (e.g., Vig et al. 2006), theoverall population and properties of this entire region inAquila are yet to be fully characterized at submm wave-lengths.Previous BLAST studies of regions like Vulpecula(Chapin et al. 2008) and Vela (Netterfield et al. 2009)have provided robust samples of submm sources in arange of evolutionary stages. By fitting modified black-body spectral energy distributions (SEDs) to the BLASTmeasurements, and with the aid of ancillary data at in-frared (IR) wavelengths for the Vulpecula sources (in-cluding
IRAS , Spitzer
MIPS, and the
Midcourse SpaceExperiment ( MSX )), these studies constrained dust tem-peratures, masses and bolometric luminosities for theirrespective samples. Their results aimed to characterizeand investigate crucial properties of the submm popula-tion, including their star formation stage, the (core) massfunction, and core lifetimes (Vela).In this paper we provide the first general characteri-zation of the submm clump population of Aquila, whichwill serve as the initial census and preliminary analysis ofthose structures that will be observed in more detail by
Herschel during its surveys of the massive star formingregions in the Galactic Plane (Hi-GAL: The
Herschel in-frared Galactic Plane Survey; Molinari et al. 2010). Likein previous BLAST studies, we provide estimates of phys-ical parameters such as mass, dust temperature, andluminosity, although in this work this analysis is con-strained to the most prominent clumps in the field, lyingat the common distance of ∼ § ii Rs and OB clusters within these main clumpswith the aid of 4.8 GHz radio interferometry data pro-vided by the Co-Ordinated Radio ‘N’ Infrared Surveyfor High-mass star formation (CORNISH; Purcell et al.2008). In § § §
4. In § OBSERVATIONS & DATA ANALYSIS
Submillimeter Data Products and Source Detection
BLAST observed Aquila during its first science flightin June 2005, mapping a total of 6 deg (3 ◦ × ◦ ) at 250,350, and 500 µ m towards GRSMC 45.60+0.30. For thefollowing analysis we note that the three BLAST mapswere made such that the average of these maps is zero(Patanchon et al. 2008). During the reduction and map-making process, the SANEPIC (Signal and Noise Es-timation Procedure) algorithm removed low-frequencynoise (mainly sky signal). Large scale signals in the mapwere recovered, but the DC level was set to zero by ap-plication of a high-pass filter to the time-ordered data.The reduction process, as well as the subsequent proce-dures to correct the unexpected optical degradation thatoccurred during the flight (Truch et al. 2008), have beendescribed in detail in Chapin et al. (2008) and Roy et al. (2010). The effective resolution is ∼
40, 50, and 60 ′′ at250, 350 and 500 µ m, respectively. The 250 and 350 µ mmaps were later convolved in order to produce BLASTmaps with a common resolution of 60 ′′ for photometryanalysis.As can be seen in Figure 1, the final products stillsuffered from artifacts (ripples) surrounding the bright-est objects and the map edges arising from the decon-volution process. These introduce false detections whenrunning the Interactive Data Language ( idl ) routinesdesigned to detect the main submm peaks in the field,and which we therefore have to eliminate manually aftervisual inspection. For source identification we used theIDL-implemented DAOPHOT ‘ find ’ routine and a S/Ndetection limit of 3 at 250 µ m, the band with higher sig-nal to noise ratio (S/N) for a typical star-forming clump.We kept a total of 66 sources between ℓ = 44 ◦ . ◦ . µ m within 20 ′′ with a S/N >
3. We also kept six ad-ditional sources (identified with (*) in Table 1) with alower S/N at 250 and 350 µ m (combined S/N between ∼ − .
5, visually prominent, and some with counter-parts in the IRAS Point Source Catalog; PSC). Theirlower S/N can be explained by their location in the localneighborhood of (clustered) bright sources, regions withdifficult background estimation and significantly aboveaverage noise. This source catalog (Table 1) is robust to ∼
50 Jy at 350 µ m ( ∼
140 Jy at 250 µ m). For compar-ison, the cirrus noise (3 σ cirrus ) at 250, 350 and 500 µ mis estimated to be ∼
20, 10, and 5 Jy for each map, re-spectively (Roy et al. 2010). In the present work we didnot require completeness to faint flux densities, however,choosing to focus our analysis only on the most promi-nent submm peaks of our sample.
Distance Estimation
In order to investigate the velocities and distances to-wards the main clumps in the field we used the COmolecular spectra from the BU-FCRAO Galactic RingSurvey (GRS; Jackson et al. 2006). The datasets coverthe region between 18 ◦ < ℓ < ◦ . − . The spatial resolution is 46 ′′ withan angular sampling of 22 ′′ . Due to the distribution ofthe clumps throughout the field, this spectral analysisis essential in order to estimate and justify the use ofa suitable common distance to the most active regionsin Aquila. A comparison of BLAST with the molecu-lar emission is shown in Figure 2. To aid qualitativeintercomparison, BLAST contours are presented in thisand a number of later figures, from images in which anapproximate DC level has been restored (300, 160, and50 MJy sr − at 250, 350, 500 µ m, respectively).For the spectral analysis we first extracted and fit-ted the CO spectra at the position of each submmpeak. Molecular counterparts from the catalogs ofRoman-Duval et al. (2009) and Rathborne et al. (2009)were assigned to each BLAST peak if the peak was lo-cated within the spatial FWHM of the molecular clump.The velocity we obtained from the spectral fitting wasthen compared with the clump velocities in the catalog.This allowed us to distinguish the appropriate molecular IDL is a product of ITT Visual Information Solutions,http://ittvis.com/ he BLAST View of Aquila 3
Fig. 1.—
BLAST submm map in Aquila combining three wavebands at 250, 350 and 500 µ m, with color coding blue, green and red,respectively. Fig. 2.—
Greyscale: CO molecular emission at ∼ ±
10 km s − with labels marking position and names (GRSMC) of clouds in thisrange from Rathborne et al. (2009). Contours are BLAST 500 µ m surface densities. White: contours from 10 to 90% of map peak value of2153 MJy sr − in 5% steps. Black: 5% contour level (see text). counterpart to the BLAST clump in those cases wheremore than one molecular counterpart (but with differ-ent Local Standard of Rest (LSR) radial velocity) wasfound for a particular BLAST clump (e.g., Table 1). Ouranalysis and line fitting of the spectra is in good agree-ment with the significant dispersion of velocities (e.g.,Figure 3) existing in the recent cloud/clump catalogs ofRathborne et al. (2009) and Roman-Duval et al. (2009).The main activity of the field is located in the mainbroad high-velocity peak in Figure 3. The smaller peakat lower velocities could arise from clumps located ei-ther much closer or much farther away ( ∼ ∼
11 kpc;Roman-Duval et al. 2009) than the complexes forming the high-velocity peak (which cluster around the tangentpoint of ∼ I self-absorption (HISA) and continuum ab-sorption, both in data from the Very Large Array Galac-tic Plane Survey (VGPS; Stil et al. 2006). There arefour clouds in their sample within the defined BLASTmap limits ( § ∼ ± . ∼
60 km s − ): G045.49+00.04, G045.74 − − − Fig. 3.—
Histogram of CO radial velocities of 68 BLAST detec-tions with molecular clump counterpart (BLAST peak lying withinspatial FWHM of clump) in catalogs of Roman-Duval et al. (2009)and Rathborne et al. (2009). The main stellar activity has veloci-ties within the broad (high velocity) peak. the major clouds in the BLAST field, G045.14+00.14(v
LSR ≈
60 km s − ), has instead been assigned its neardistance of ∼ . ∼ ∼
60 km s − and located in this dis-tance range. Furthermore, this estimate is in goodagreement with the distances derived by Pandian et al.(2009), who also resolved the kinematic distance am-biguities using H I self-absorption with data from theVGPS. These authors calculated, by means of methanolmasers and a flat rotation curve, a range of distancesfor the clumps within G045.49+00.04 between 6 . . . − − − ∼ ◦ ∼ . ∼ ∼ Ancillary Data
To create our SEDs we used the BLAST fluxesestimated using our own Gaussian fitting routine( § IRAS
Galaxy Atlas (IGA; Cao et al. 1997:HIRES; Aumann et al. 1990) at 60 and 100 µ m and BOLOCAM (Galactic Plane Survey) data at 1.1 mm(Rosolowsky et al. 2010). IRAS flux densities were es-timated individually using our Gaussian fitting routine,while for the convolved (60 ′′ ) BOLOCAM images we usedaperture photometry (single sources: an aperture cen-tered on the BLAST source with 1 ′ .8 radius; an estimatefor the background was obtained from an annulus formedby the source aperture and another aperture with radius1.3 times larger than that of the source). The measuredBOLOCAM fluxes were found to be within the errorrange of those provided by the GATOR service , and thelatter values were therefore used to constrain the SEDs atlonger wavelengths if a counterpart to the BLAST clumpwas found within 30 ′′ (we found 39 sources in Table 1with BOLOCAM counterparts, including all those withmeasured SEDs, with the exception of A22). We notethat IRAS was found to be saturated for the brightestclumps, for which we adopted the upper limits estimatedby Kraemer et al. (2003). Most of our measured
IRAS fluxes were also found to be higher than those from the
IRAS
PSC. This effect, combined with the lower resolu-tion of
IRAS and the photometry of sometimes blendedsources, imply that these values should also be generallyconsidered upper limits in our fits.To investigate the stellar content and the morphologyof the emission at shorter wavelengths we used the In-fraRed Array Camera (IRAC) on
Spitzer . Of the fouravailable IRAC bands (3 .
6, 4 .
5, 5 .
8, and 8 µ m), we fo-cused on the longest wavelength in our morphology anal-ysis. For our study of the stellar population we used datafrom the Galactic Legacy Infrared Midplane Survey Ex-traordinaire (GLIMPSE; Benjamin et al. 2003) throughthe online gator query system. The GLIMPSE I onlinedatasets, covering about 220 deg of the Galactic Plane( ℓ = 10 ◦ − ◦ ) in all four IRAC bands, include a highlyreliable (GR) catalog and a more complete, but less reli-able one (GC). Both were used in the present work. Fig. 4.—
Spectral energy distribution of A16 (Table 1). Symbolsare BLAST and ancillary data (
IRAS ; BOLOCAM). Upper andlower curves are the 1-sigma envelope of the dust emission model(Chapin et al. 2008). http://irsa.ipac.caltech.edu/applications/Gator/ he BLAST View of Aquila 5 Photometry: Spectral Energy Distributions andParameter Estimation
Similar to other Galactic BLAST studies (e.g.,Chapin et al. 2008), our SED analysis was carried outby estimating flux densities with our own idl spatialGaussian-fitting routine, and subsequently fitting themwith a modified blackbody of the form:
Fig. 5.—
Same as Fig.4, but for A50 (Table 1). S ν = A (cid:18) νν (cid:19) β B ν ( T ) , (1)where β is the dust emissivity index, ( ν/ν ) β is the emis-sivity factor normalized at a fixed frequency ν , and B ν ( T ) is the Planck function. The amplitude A can beexpressed as: A = M c κRD , (2)where D is the distance to the source, M c is the totalclump mass, κ is the dust mass absorption coefficient,evaluated at ν = c/ µ m, and R is the gas-to-dustratio. A 2-D Gaussian is fitted to the three bands si-multaneously with the amplitudes, centroid, orientationangle, and major and minor Full Width at Half Maxi-mum (FWHM) as free parameters. The fit is carried outusing a non-linear least-squares minimization idl routine(based on mpfit : Markwardt 2009), which also allowedfor simultaneous multiple Gaussian fitting in crowded re-gions of the field. The background was estimated by fit-ting a fourth-order polynomial to the regions around theclump.Following Chapin et al. (2008), estimates and uncer-tainties for the dust temperatures, masses, and lumi-nosities were obtained through a Monte Carlo analysisperformed on our SED models, keeping the dust emis-sivities and R as fixed parameters ( β = 1 . R = 100, κ = 10 cm g − ). Examples of SEDs are shown in Fig-ure 4 and Figure 5. A flux density consistency checkbetween all convolved and deconvolved maps shows fluxconservation to better than 5%. The bolometric luminosities derived from the fits foreach evolved clump were subsequently used to estimateequivalent single zero-age-main-sequence star (ZAMS)spectral types using the tables of Panagia (1973). Thisluminosity value was used as a general measure of theenergy output of each submm detection. We note thatthe BLAST sources at a distance of ∼ T eff scale;these authors note that the theoretical and observationalscales are in good agreement for early type dwarfs andsupergiants. For our radio analysis we used the CORNISH inter-ferometry datasets, a 4.8 GHz VLA survey covering thenorthern GLIMPSE region with a resolution of ∼ ′′ .Our analysis of these data was carried out using thesame procedure and Gaussian fitting codes used for thesubmm. The 4.8 GHz fluxes from our fitting were thenused to estimate the total number of ionizing photonsper unit time for each radio source (e.g., Panagia 1973;Martins et al. 2005): Q = Z ∞ ν L ν hν dν, (3)where ν is the frequency at the Lyman edge.These values were also used in conjunction with thetables from Panagia (1973) and Martins et al. (2005) toestimate the equivalent single-star radio spectral typesfor each detection. The positions and parameters de-rived using these data have been included in Tables 2, 3,and 4. The target S/N of our sample is >
3. As with theBLAST sources, we have also kept a few radio detectionswith lower S/N. These were identified and required byour Gaussian fitting routine, and are almost exclusivelysecondary peaks neighboring the brightest sources (clus-ters: A16-C24, A28-C15), where the S/N is greatly dete-riorated ( > . − C ∼ . ∼ ∼ TABLE 1
Submm clumps in the BLAST Aquila map.Source BLAST Name a ℓ b IRAS
Name b IRDC c Cloud d Clump e D (kpc) f Assoc. g A0 J191131+102635 44 .
502 0 .
347 19091+1021A1 J191124+102845 44 .
522 0 .
387 19090+1023A2 J191432+100817 44 . − .
454 P3726 G044.34-00.21 c12 4.12 YA3 J191135+103138 44 .
585 0 . .
660 0 .
350 19094+1029A5 J191334+102308 44 . − .
129 19112+1018 G044.49-00.16 c8 7.55G044.69-00.11 c1 3.7 YA6 J191514+101158 44 . − .
577 G045.09-00.51 c4 6.0G044.74-00.56 c1,c7 − YA7 J191537+101015 44 . − .
675 G044.74-00.56 c2 − YA8 J191514+101518 44 . − .
551 G044.74-00.56 c1,c8 − YA9 J191457+102119 44 . − .
442 19125+1015 G045.09-00.51 c6 6.0A10 J191611+101914 44 . − . . − . .
070 0 .
132 19110+1045 G045.14+00.14 c1 4.53 YA13 J191538+103419 45 . − .
492 19132+1029 G045.09-00.51 c1 6.0 YA14 J191528+103636 45 . − . . − .
119 19119+1041A16 J191327+105338 45 .
123 0 .
132 19111+1048 G045.14+00.14 c1 4.53 YA17 J191641+102952 45 . − .
752 19143+1024A18 J191602+103743 45 . − .
553 G045.39-00.76 c6 7.18 YA19 J191539+104116 45 . − .
439 19132+1035 G045.09-00.51 c2 6.0 YA20 J191706+103032 45 . − . . − .
592 19142+1041 G045.74-00.26 c2 7.28 YG045.39-00.76 c3,c10 7.18 ?G045.84-00.56 c4 3.62A22 J191706+104322 45 . − .
738 G045.39-00.76 c1,c9,c11,c13 7.18 YA23 J191701+104447 45 . − .
710 G045.39-00.76 c7,c11,c13 7.18 YA24 J191620+105035 45 . − .
518 19139+1045 G045.84-00.56 c4 3.62A25* J191451+110244 45 . − .
100 19125+1057A26* J191457+110324 45 . − . . − . .
449 0 .
063 19120+1103 G045.49+00.04 c1,c5,c7,c8 7.45 YG045.14+00.14 c5 4.53 ?G045.24+00.19 c1 − A28a h J191414+110809 45 .
425 0 . .
464 0 .
046 19120+1103 i P3744 G045.49+00.04 c1,c4,c5,c7 7.45 Yc8G045.14+00.14 c2 4.53 ?A30 J191407+111222 45 .
475 0 .
133 19117+1107 G045.49+00.04 c2,c3,c5-c8 7.45 YG045.24+00.19 c1 − A30a J191409+111245 45 .
485 0 . .
493 0 .
222 G045.24+00.19 c1 − A32 J191536+110259 45 . − . . − . . − .
391 19138+1055A35 J191450+111127 45 . − .
029 G045.49+00.04 c4 7.45 YA36 J191446+111159 45 . − .
012 19124+1106 G045.49+00.04 c4 7.45 YA37 J191512+111007 45 . − .
119 G045.49+00.04 c4 7.45G045.64-00.01 c2 11.12 YA38 J191459+111541 45 . − .
030 G045.49+00.04 c4 7.45G045.64-00.01 c1,c3,c4 11.12 YA39 J191458+111639 45 . − .
018 G045.49+00.04 c4 7.45G045.64-00.01 c1,c4 11.12 YA40 J191358+112532 45 .
651 0 .
270 G045.49+00.04 c9 7.45G045.89-00.36 c4 6.72G045.64+00.29 c1,c5,c6 1.88A41 J191709+110129 45 . − .
608 G045.39-00.76 c2 7.18 YG045.94-00.56 c5 4.78 ?A42* J191553+111347 45 . − .
237 G046.19-00.56 c4 3.75G045.74-00.26 c1,c10,c11 7.28 YContinued on Next Page. . . he BLAST View of Aquila 7
TABLE 1 – ContinuedSource BLAST Name ℓ b
IRAS
Name IRDC Cloud Clump D (kpc) Assoc.c13-c15,c23,c24G045.89-00.36 c2 6.72 ?G045.84-00.56 c3 3.62A43 J191705+110509 45 . − . . − .
291 19137+1108 G046.19-00.56 c4 3.75G045.74-00.26 c1,c8,c21 7.28 YG045.89-00.36 c2 6.72G046.14-00.21 c2 1.8G045.84-00.56 c3 3.62A45 J191604+111725 45 . − .
251 G046.19-00.56 c4 3.75G045.74-00.26 c1,c12,c21 7.28 YG045.89-00.36 c2 6.72 ?G045.84-00.56 c3 3.62G046.09+00.24 c2 − A46 J191630+111606 45 . − .
355 19141+1110 G045.74-00.26 c16,c19 7.28 YG045.89-00.36 c2 6.72 ?G046.09+00.24 c2 − A47 J191618+111909 45 . − .
286 19139+1113 G046.19-00.56 c4 3.75G045.74-00.26 c1 7.28 ?G045.89-00.36 c2 6.72 YG045.84-00.56 c10 3.62G046.09+00.24 c2 − A48 J191713+111605 45 . − .
511 P3758 G045.89-00.36 c1 6.72 YA49 J191447+113705 45 .
915 0 .
181 19124+1131 G045.89-00.36 c6 6.72G045.64+00.29 c1 1.88A50 J191655+112153 45 . − .
401 19145+1116 G045.89-00.36 c1,c2 6.72 YG045.94-00.56 c2 4.78 ?A51 J191514+113632 45 .
959 0 .
078 G045.89-00.36 c6 6.72G046.14-00.21 c6 1.8A52 J191456+114614 46 .
068 0 .
218 G045.89-00.36 c6 6.72G045.64+00.29 c1 1.88G046.09+00.24 c1 − YA53 J191450+114805 46 .
084 0 .
254 19125+1142 G045.89-00.36 c6 6.72G045.64+00.29 c1 1.88G046.09+00.24 c1 − YA53a J191448+114910 46 .
096 0 . .
094 0 .
429 G046.14+00.39 c1 4.25 YG045.64+00.29 c1 1.88A55 J191423+115342 46 .
115 0 .
396 19120+1148 G046.14+00.39 c1 4.25 YG045.64+00.29 c1 1.88A56 J191617+114240 46 . − .
102 19139+1137 G045.89-00.36 c6 6.72G046.14-00.21 c1 1.8A57 J191750+113102 46 . − .
527 P3762 G046.19-00.56 c1 3.75 YA58 J191400+120052 46 .
177 0 .
535 19116+1155A59 J191402+120157 46 .
197 0 . .
212 0 . . − .
628 G046.24-00.66 c1 4.07 YA61 J191851+112750 46 . − . . − .
234 19146+1141 G046.19-00.56 c2 3.75 ?G046.34-00.21 c2,c3,c5,c7 4.12 Yc9-c11A63* J191703+115012 46 . − .
208 G046.19-00.56 c2 3.75 ?G046.34-00.21 c2,c5,c9,c12 4.12 Yc13A64* J191709+114956 46 . − .
231 G046.19-00.56 c2 3.75 ?G046.34-00.21 c2,c5,c12 4.12 YA65 J191655+115407 46 . − .
150 19146+1148 P3773 G046.19-00.56 c2 3.75 YG046.34-00.21 c2,c5,c12 4.12A66 J191715+115225 46 . − .
235 19149+1147 P3776 G046.19-00.56 c2 3.75 ?G046.34-00.21 c1,c2,c5,c6 4.12 Yc12A67* J191711+115548 46 . − .
194 P3778 G046.19-00.56 c2 3.75 ?Continued on Next Page. . .
Rivera-Ingraham, A. et al.
TABLE 1 – ContinuedSource BLAST Name ℓ b
IRAS
Name IRDC Cloud Clump D (kpc) Assoc.G046.34-00.21 c1,c5,c6,c12 4.12 YG046.79+00.04 c3 3.6A68 J191631+120108 46 . − . .
496 0 . . − .
586 19164+1145 G046.19-00.56 c3 3.75 ?G046.89-00.36 c1 8.05 YA71 J191537+121816 46 .
618 0 .
319 19132+1212 G046.59+00.34 c1 0.65 YG046.59+00.19 c2 0.8 ? a Source names include the prefix ‘BLAST’ as part of the standard BLAST nomenclature. b Closest
IRAS match within 30 ′′ in the Point Source Catalog (PSC). c Closest IRDC match within 30 ′′ in the catalog from Peretto & Fuller (2009). d GRS name of the extended clouds from Rathborne et al. (2009) which contain the molecular clumpcounterpart(s) to the BLAST source. A blank implies the absence of a clump counterpart in the catalog. e Clump(s) from Rathborne et al. (2009) containing the BLAST peak within its/their ℓ and b FWHM. f Distance from Roman-Duval et al. (2009). g Cloud association: (Y) - BLAST clump is associated with the cloud. Cloud has a molecular clump whosevelocity FWHM contains the strongest molecular peak of spectrum, measured at the peak of the submm emission.Molecular clump also has peak velocity closest to that measured for the BLAST source.(?) - Cloud membership unclear. The main molecular emission in the BLAST spectrum is within the velocityFWHM of this molecular cloud/clump, but there is still another cloud with a clump with peak velocitycloser to that of the strongest line in the BLAST spectrum. Contributions from different clouds are possible.A blank implies that the velocity of main BLAST molecular emission is not compatible with that assignedto the cloud/clump, despite the spatial agreement and apparent location of the submm peak within thespatial FWHM of clump(s) associated with that cloud. h Source designations ending in ‘a’ refer to additional Gaussians required during the fit of the main clump. i Position beyond 30 ′′ , but visually within the IRAS emission.* Detection S/N < DISCUSSION OF INDIVIDUAL SOURCES
In the following sections we apply the results ofour analysis to describe the main submm regions(G045.49+00.04, G045.74-00.26, G045.89-00.36, andG045.14+00.14), adopting the designations from Rath-borne et al (2009; Figure 2).
GRSMC G045.14+00.14
G45.12
GRSMC 45.122+0.132 (G45.12; IRAS 19111+1048;A16 in the present work), contains a cometary UCH ii R(WC89) classified as a massive young stellar object(MYSO) by Chan et al. (1996). It shows extendedsubmm emission towards the north (upper left of Figure6), observed in the MIR as a bright rimmed H II region.This structure is likely produced by the activity of theyoung massive population embedded in the innermostregions of the clump, as detected by Vig et al. (2006) us-ing the Giant Metrewave Radio Telescope (GMRT) at1200 and 610 MHz. The 19 embedded OB stars observedby these authors are located within and surrounding thepeak of our BLAST clump, mainly within the H II region.Their brightest source agrees well with our submm peak( . ′′ ), and although it remained unresolved in theirdatasets, they suspected it to be a cluster responsible forthe extended morphology in the radio. A possible clus-ter powering this region has also been suggested through[NeII] observations by Takahashi et al. (2000), and laterby Zhu et al. (2008), who detected three additional peaks(G45.12N, G45.12SE and G45.12SW) nearby the mainUCH ii R from WC89.
Fig. 6.—
Greyscale IRAC 8 µ m image of IRAS 19111+1048 (A16)and IRAS 19110+1045 (A12) with BLAST 500 µ m contours su-perimposed. Contours are from 10 to 90% of map peak value2153 MJy sr − in 10% steps. Our analysis of the 4.8 GHz CORNISH data confirmssuch suspicions, with the detection of 28 radio sources ina region ∼ . − C24; Table 3; Figure7). These objects are believed to be forming the unre-solved source observed by Vig et al. (2006, S14 in theirsample). None have a radio ZAMS spectral type laterthan B0 (with the exception of A16 − C18, which was notinitially detected by our extraction routine).We find that 22 of these radio sources lie within ∼ . − C24. This object has a bolometric lu-he BLAST View of Aquila 9
TABLE 2Coordinates of CORNISH sources in the BLAST Aquila field.
BLAST CORNISH RA Dec BLAST CORNISH RA Dec(J2000) (J2000) (J2000) (J2000)h m s ◦ ′ ′′ h m s ◦ ′ ′′
A12 A12 − C0 19 13 19.063 +10 51 26.521 A28 A28 − C0 19 14 20.710 +11 09 13.540A12 − C1* 19 13 21.617 +10 50 56.756 A28 − C1 19 14 20.714 +11 08 57.156A12 − C2 19 13 21.886 +10 50 49.704 A28 − C2 19 14 20.784 +11 09 17.737A12 − C3 19 13 22.130 +10 50 52.163 A28 − C3 19 14 20.918 +11 09 15.926A12 − C4 19 13 23.834 +10 51 42.624 A28 − C4 19 14 20.957 +11 09 01.728A12 − C5 19 13 23.954 +10 51 41.497 A28 − C5 19 14 21.002 +11 09 16.578A12 − C6 19 13 25.548 +10 51 07.567 A28 − C6 19 14 21.002 +11 09 20.246A12 − C7 19 13 25.584 +10 51 07.535 A28 − C7 19 14 21.120 +11 09 08.550A12 − C8 19 13 25.601 +10 51 09.320 A28 − C8 19 14 21.190 +11 09 07.268A12 − C9 19 13 25.697 +10 50 57.977 A28 − C9 19 14 21.226 +11 09 02.110A16 A16 − C0 19 13 24.283 +10 53 28.525 A28 − C10 19 14 21.250 +11 09 14.915A16 − C1* 19 13 24.374 +10 53 27.247 A28 − C11 19 14 21.276 +11 09 11.534A16 − C2 19 13 24.446 +10 53 25.919 A28 − C12 19 14 21.338 +11 09 22.162A16 − C3 19 13 24.994 +10 53 13.895 A28 − C13 19 14 21.362 +11 09 10.084A16 − C4 19 13 25.116 +10 54 16.153 A28 − C14 19 14 21.386 +11 09 11.242A16 − C5 19 13 25.205 +10 53 14.932 A28 − C15 19 14 21.408 +11 09 13.309A16 − C6 19 13 27.055 +10 53 19.946 A28 − C16 19 14 21.578 +11 09 04.824A16 − C7 19 13 27.218 +10 53 22.794 A28 − C17 19 14 21.617 +11 09 15.264A16 − C8 19 13 27.331 +10 53 46.489 A28 − C18 19 14 21.720 +11 08 55.424A16 − C9* 19 13 27.516 +10 53 46.558 A28 − C19 19 14 21.854 +11 08 54.413A16 − C10 19 13 27.545 +10 53 30.196 A28 − C20 19 14 21.862 +11 09 30.956A16 − C11* 19 13 27.583 +10 53 46.237 A28 − C21 19 14 21.893 +11 09 17.791A16 − C12* 19 13 27.583 +10 53 49.636 A28 − C22 19 14 22.022 +11 09 45.385A16 − C13 19 13 27.586 +10 53 27.920 A28 − C23 19 14 22.099 +11 09 45.972A16 − C14 19 13 27.602 +10 53 25.483 A28 − C24 19 14 22.272 +11 09 37.760A16 − C15 19 13 27.703 +10 53 29.249 A28 − C25 19 14 22.481 +11 09 31.090A16 − C16 19 13 27.710 +10 53 29.807 A28 − C26 19 14 22.615 +11 09 43.690A16 − C17 19 13 27.763 +10 53 38.990 A28 − C27 19 14 22.776 +11 08 57.970A16 − C18 19 13 27.773 +10 53 34.897 A29 A29 − C0 19 14 25.690 +11 09 25.330A16 − C19 19 13 27.797 +10 53 32.194 A29 − C1 19 14 26.222 +11 08 35.488A16 − C20 19 13 27.866 +10 53 30.181 A29 − C2 19 14 26.942 +11 09 14.897A16 − C21 19 13 27.888 +10 53 40.402 A29 − C3 19 14 27.079 +11 09 12.456A16 − C22 19 13 27.912 +10 53 33.659 A29 − C4 19 14 27.559 +11 09 56.617A16 − C23 19 13 27.929 +10 53 27.013 A30 A30 − C0 19 14 07.330 +11 12 41.742A16 − C24 19 13 27.965 +10 53 35.675 A30 − C1* 19 14 08.227 +11 12 22.684A16 − C25 19 13 28.008 +10 53 45.150 A30 − C2 19 14 08.232 +11 12 36.929A16 − C26 19 13 28.022 +10 53 28.806 A30 − C3 19 14 08.602 +11 12 26.327A16 − C27 19 13 28.030 +10 53 24.598 A30 − C4* 19 14 08.830 +11 12 26.586A16 − C28 19 13 28.034 +10 53 42.302 A30 − C5 19 14 09.046 +11 12 25.661A16 − C29 19 13 28.128 +10 53 31.708 A30 − C6 19 14 09.094 +11 12 22.075A16 − C30 19 13 28.212 +10 53 37.547 A30a A30a − C0 19 14 08.604 +11 13 19.175A16 − C31 19 13 28.222 +10 53 34.260 A47 A47 − C0 19 16 17.645 +11 18 59.670A16 − C32 19 13 28.226 +10 53 35.905 A47 − C1 19 16 17.746 +11 19 14.509A16 − C33 19 13 28.380 +10 53 32.298 A47 − C2 19 16 19.330 +11 19 14.992A16 − C34 19 13 29.842 +10 53 34.318 A50 A50 − C0 19 16 55.730 +11 21 48.355A16 − C35 19 13 31.090 +10 53 45.031* Detection S/N < minosity equivalent to an O6 ZAMS star, which is ingood agreement with previous results for a distance of ∼ − C24 also agrees with the UCH ii R of WC89 andTesti et al. (1999). The two 2MASS IR sources detectedby Vig et al. (2006) within their S14 source (IR4 andIR5) agree well with A16 − C24 and A16 − C26 and thetwo peaks (KJK1 and KJK2) detected by Kraemer et al.(2003). The G45.12SE peak from Zhu et al. (2008) tracesthe region of A16 − C26; G45.12SW is formed by theconglomeration of radio sources towards A16 − C13, andG45.12N is centered on the arc-shaped radio emissionaround A16 − C21. The estimated spectral types of all radio sources within ∼ ′ of the BLAST coordinates havebeen included in Table 3 for an electron temperature sim-ilar to that estimated by Vig et al. (2006, ∼ σ positional error of ourCORNISH source A16 − C24 ( ∼ . ′′ ) and that expectedfor the OH maser detection of Baart & Cohen (1985), ∼
10 milliarcsec, the separation of ∼ ′′ between thetwo may be physically significant. Indeed, our projectedseparation of ∼ . ii R, and agrees well with the dis-placement measured by Baart & Cohen (1985), of theorder of ∼ .
03 pc (with respect to the coordinates from0 Rivera-Ingraham, A. et al.
TABLE 3Spectral types and IR counterparts for the BLAST peaks A16 and A12 and the radio sources detected in the CORNISHdata within ∼ ′ of the submm peaks. Source IR+submm a IR+submm a IR b TFT1 c TFT2 c (ZAMS) (Class V) (6 cm) (3.6 cm)log Q d e e GLIMPSE f [s − ]A16 O6 − O5.5 O6 − O4 O5 O6 O6A16 − C0 46 . +0 . − . B0.5 − B0/ − A16 − C1 46 . +0 . − . B0.5 − B0/ − A16 − C2 46 . +0 . − . B0/ − A16 − C3 47 . +0 . − . B0/ − A16 − C4 46 . +0 . − . B0.5/ − A16 − C5 46 . +0 . − . B0.5 − B0/ − A16 − C6 47 . +0 . − . B0.5 − B0/ − G045.1163+00.1327A16 − C7 47 . +0 . − . B0/ − G045.1163+00.1327A16 − C8 46 . +0 . − . B0.5/ − A16 − C9 46 . +0 . − . B0.5/ − A16 − C10 47 . +0 . − . B0/ − A16 − C11 46 . +0 . − . B0.5/ − A16 − C12 46 . +0 . − . B0.5/ − A16 − C13 47 . +0 . − . B0/ − A16 − C14 47 . +0 . − . O9.5/ − A16 − C15 47 . +0 . − . B0/ − A16 − C16 47 . +0 . − . B0 − O9.5/ − A16 − C17 48 . +0 . − . O8.5 − O8/O8.5 G045.1221+00.1322A16 − C18 g . +0 . − . < O8.5/O8.5 G045.1221+00.1322A16 − C19 47 . +0 . − . O9.5/O9.5 G045.1221+00.1322A16 − C20 47 . +0 . − . O9.5/ − A16 − C21 48 . +0 . − . O9.5 − O7.5/O8 G045.1221+00.1322A16 − C22 g . +0 . − . O8.5/O9 − O8.5 G045.1221+00.1322A16 − C23 46 . +0 . − . B0.5 − B0/ − A16 − C24 49 . +0 . − . O6/O5.5 O5 O6 G045.1221+00.1322A16 − C25 47 . +0 . − . B0/ − A16 − C26 47 . +0 . − . O9.5/O9.5 B0.5 B0A16 − C27 46 . +0 . − . B0.5/ − A16 − C28 47 . +0 . − . O9.5 − O9/O9.5 − O9A16 − C29 47 . +0 . − . O9.5/ − A16 − C30 48 . +0 . − . O9.5 − O8.5/O8.5A16 − C31 47 . +0 . − . B0 − O8.5/O9A16 − C32 48 . +0 . − . O8/O8.5A16 − C33 47 . +0 . − . B0.5 − − A16 − C34 47 . +0 . − . B0/ − A16 − C35 47 . +0 . − . O9.5/ − G045.1302+00.1223A12 O6 O5 O6 O8.5 h O8 h A12 − C0 47 . +0 . − . B0/ − G045.0729+00.1484A12 − C1 46 . +0 . − . B0.5/ − A12 − C2 46 . +0 . − . B0.5/ − B0.5 B0 − O9.5 G045.0712+00.1321A12 − C3 47 . +0 . − . O9.5/ − O6.5 O9 G045.0712+00.1321A12 − C4 47 . +0 . − . B0 − O9.5/ − A12 − C5 47 . +0 . − . O9/O9A12 − C6 46 . +0 . − . B0.5/ − A12 − C7 g . +0 . − . O9.5 − O9/ < O8.5A12 − C8 47 . +0 . − . B0/ − A12 − C9 47 . +0 . − . B0/ − G045.0788+00.1191 a ZAMS and Class V spectral types from Panagia (1973) and Martins et al. (2005) for D = 7 kpc. If the luminosity is not within the range of the calibration scale, no estimate ( − ) is provided. b ZAMS spectral type derived by Kraemer et al. (2003) from the total source flux in the IR (
IRAS ) for D = 6 kpc. c ZAMS spectral type of the counterpart of the brightest CORNISH source within BLAST clumpin Testi et al. (1999) for D = 7 kpc. d Total number of ionizing photons per unit time for a distance of 7 kpc and T e ∼ e ZAMS spectral type derived by Kraemer et al. (2003) for D = 6 kpc. Values are provided only for sources lying closerthan 5 ′′ to the CORNISH source. f Closest IRAC GLIMPSE I Complete Catalog match within ∼ ′′ of the CORNISH peak. g Extra source required during Gaussian fitting. h Estimate includes total flux of C0 and C1, as both are unresolved at 6 cm (Testi et al. 1999). he BLAST View of Aquila 11Matthews et al. 1977). This distance, as pointed out byBaart & Cohen (1985), is well within the upper limit forthe radius at which OH masers are produced in a shell-like front surrounding a massive young star. This sug-gests that these may be dense fragments of the expand-ing shell. The blueshift for the maser clusters detectedby these same authors ( ∼ − ) is also similar tothat observed for the dense gas traced with ammonia byHofner et al. (1999), whose absorption peak coordinatesare also offset from our radio peak in the same direc-tion as the maser source. This supports the real physicalorigin of the observed displacement. Fig. 7.—
Greyscale CORNISH 4.8 GHz image of central cluster(S14 in Vig et al. 2006) in IRAS 19111+1048 (A16) with numberedemission peaks (Table 3). White contours are from 2.5% to 12.5%of map peak value 0.7 Jy beam − in 1% steps. Grey contours arefrom 15% to 85% in 10% steps. Fig. 8.—
Greyscale IRAC 8 µ m image of IRAS 19111+1048 (A16)with 250 µ m BLAST contours overlaid. Cross marks the positionof submm peak, and circles the positions of main CORNISH detec-tions (central cluster). Contours are from 5% to 85% of the mappeak value of 31500 MJy sr − in 10% steps. Although further investigation is required, our analy-sis of the CORNISH data and the evidence in the midinfrared (MIR) and submm suggest that A16 − C24 maybe the initial trigger and power source of G45.12. Themassive outflow detected by Hunter et al. (1997) appears to follow the overall direction of the distribution of COR-NISH sources well, which could indicate that A16 − C24has induced the formation of its lower mass companions.In addition, the distribution of CORNISH sources ap-pears to have a slightly curved, bow-shock like morphol-ogy pointing towards the submm comma-like structureextending downwards in Figure 8. This structure alsocoincides with the strongest emission in CO and CS.Considering its central position, A16 − C24 appears as asuitable candidate for the main triggering/compressingsource.
G45.07
Just like its neighbor, IRAS 19110+1045 (A12;GRSMC 45.073+0.129 [G45.07]) also shows submm, IR,and radio structure signaling the presence of massive starformation, albeit significantly less pronounced than inG45.12. Only nine possible CORNISH detections arefound within ∼ ′ of the BLAST position, with radioZAMS/class V spectral types ranging between B0.5 andO9 for an electron temperature of 8000 K (Table 3). Thelower number of stars and their later apparent radio spec-tral type is consistent with the more compact size of theresulting ionized region compared to G45.12.Two CORNISH sources, A12 − C2 and A12 − C3 (Fig-ure 9), match ( . ′′ .5) those detected by Vig et al.(2006) and the two embedded IR sources (KJK1, KJK3)from Kraemer et al. (2003). Despite the positional ac-curacy of our CORNISH measurements ( < ′′ .5 differ-ence between our two coordinates and those given byTesti et al. 1999 and WC89), we find no indication ofthe third IR source (KJK2) detected by Kraemer et al.(2003). This source is located ∼ ′′ from A12 − C3, andshould have been identifiable at the resolution limit ofthe CORNISH data.
Fig. 9.—
Greyscale CORNISH image of three central sourceslikely powering IRAS 19110+1045 (A12). Contours are from 2%to 9% of map peak value 0.7 Jy beam − in 1% steps. As with G45.12, G45.07 also contains a UCH ii R(spherical/unresolved UCH ii R; WC89) with a CO out-flow (Hunter et al. 1997) and masers. Our brightest ra-dio source lies at < ′′ .5 from the coordinates given byWC89. The masers show a more significant displace-ment ( ∼ ′′ ), and appear to extend along the over-2 Rivera-Ingraham, A. et al. Fig. 10.—
Greyscale IRAC 8 µ m image of IRAS 19110+1045(A12). Symbols and contours like Fig.8. all outflow direction. In addition to hydroxyl masers,G45.07 also shows several water maser sources (e.g.,Hofner & Churchwell 1996) and 6.7 GHz methanol emis-sion (Pandian et al. 2007), with distances ranging be-tween ∼ ′′ .5 and ∼ ′′ .5 from our brightest COR-NISH radio peak, respectively.Most water masers align well with our radio sourceA12 − C3 and the overall outflow direction. This, to-gether with the clear separation from our radio peak,again supports the scenario where they are energizedby the bipolar outflow (e.g., Hofner & Churchwell 1996;De Buizer et al. 2005). The presence of these watermasers also implies a less advanced evolutionary stagethan that of its neighbor G45.12 (in agreement with pre-vious studies: e.g., Vig et al. 2006). This is supportedby the simpler overall morphology, the lower stellar con-tent, and the much earlier spectral type inferred from theIR/submm for A12 − C3 and for the total clump with re-spect to those derived from the radio, suggesting a muchmore deeply embedded stage with significant radio opti-cal depth.While there appears to be extended MIR emission inthe GLIMPSE images, consistent with the outflow orien-tation, there is also considerable emission in an almostorthogonal direction to its main axis (western upper rightcorner in Figure 10). The peak of the 21 cm radio contin-uum is displaced towards this region. The overall mor-phology appears to be similar to the extended H II inG45.12, albeit in a smaller scale, which could be due toits younger age and/or the lower stellar content in theinnermost central region. Submm Analysis
Our analysis of the SEDs yields total system massesfor G45.12 and G45.07 of ∼ ⊙ and ∼ ⊙ , re-spectively, for a distance of 7 kpc (Table 6). This differsfrom the estimates given by Hunter et al. (1997), who ob-tained (with temperature, dust emissivity index, and op-tical depth as free parameters) masses ∼ ∼ ⊙ ( ∼
20 M ⊙ of dust, and a larger gas-to-dustratio of 250) and 13,000 M ⊙ (for a dust mass of 30 M ⊙ ,and gas to dust ratio of 450) for G45.12 and G45.07,respectively. Scaling to the same distance, we obtain M d ∼
26 and M d ∼ . ⊙ . While our dust mass esti-mate for G45.12 is in good agreement with their estimatefrom the SCUBA maps, the mass for G45.07 is in betteragreement with the mass these authors estimated fromtheir 130 µ m map (obtained with the TIFR 1-m balloonborne telescope; Ghosh et al. 1988), of ∼
13 M ⊙ .We find temperatures for G45.12 and G45.07 of ∼
40 K,and clump luminosities equivalent to an ∼ O6 ZAMSspectral type star ( ∼ O5 Class V star). This is ingood agreement with those estimated from the IR (e.g.,Kraemer et al. 2003) for the brightest sources within theclumps. This suggests that A16 − C24 and A12 − C3 arethe main sources responsible for the dust heating inG45.12 and G45.07, respectively. We note, however, thatthe significantly later spectral type derived from the ra-dio for A12 − C3 appears to suggest a much younger andhighly embedded stage than A16 − C24.
GRSMC G045.49+00.04
This cloud complex is dominated by the other two mainsubmm peaks in the BLAST region, IRAS 19120+1103(GRSMC 45.453+0.060; [G45.45]; a MYSO candidate inthe RMS Survey; e.g., Mottram et al. 2010) and IRAS19117+1107 (GRSMC 45.478+0.131; [G45.48]). Bothsources show significant extended submm emission (Fig-ure 11), and required additional Gaussians to model theemission local to the main submm peaks. At
IRAS resolution the extended emission of both sources wasnot resolved, and so our BLAST flux densities were ob-tained with aperture photometry combining A28 withA29 (AA29; Figure 12, comprising G45.47+0.05 andG45.45) and A30 with A30a (AA30).The presence of UCH ii Rs was detected by WC89 andTesti et al. (1999) at 3.6 cm. Chan et al. (1996) classifiedAA29 as a MYSO. The activity and complexity of thisregion is particularly prominent in the IRAC images, ascan be observed in Figures 11-13.
Fig. 11.—
Greyscale IRAC 8 µ m image of IRAS 19120+1103 andIRAS 19117+1107. Contours like Fig.6. G45.47+0.05 he BLAST View of Aquila 13
TABLE 4Spectral types and IR counterparts for the BLAST peaks A28, A29, A30, and A30a and the radio sources detected in theCORNISH data within ∼ ′ of the submm peaks. Source IR+submm IR+submm IR TFT1 TFT2(ZAMS) (Class V) (6 cm) (3.6 cm)log Q − ]AA29 O6.5 − O5.5 O7 − O4.5A28 O5.5 O6.5 a − O5.5 b Complex1 49 . +0 . − . O5.5/O5 G045.4509+00.0570 c A28 − C1 47 . +0 . − . B0/ − A28 − C18 46 . +0 . − . B0.5 − B0/ − A28 − C19 47 . +0 . − . B0/ − A28 − C20 47 . +0 . − . B0/ − A28 − C22 46 . +0 . − . B0.5/ − A28 − C23 47 . +0 . − . B0.5 − B0/ − A28 − C24 46 . +0 . − . B0.5/ − A28 − C25 46 . +0 . − . B0.5/ − A28 − C26 46 . +0 . − . B0.5 − B0/ − G045.4640+00.0574A28 − C27 46 . +0 . − . B0.5/ − A29 O9.5A29 − C0 47 . +0 . − . O9.5/ − G045.4661+00.0457(GR)G045.4658+00.0452 (GC)A29 − C1 46 . +0 . − . B0.5 − B0/ − G045.4551+00.0359A29 − C2 47 . +0 . − . B0/ − A29 − C3 47 . +0 . − . B0/ − A29 − C4 47 . +0 . − . B0/ − AA30 B0 − O6.5 < O6.5A30 O6.5 − O6 O6.5Complex2 48 . +0 . − . O7.5/O8 O6.5 O7A30 − C0 46 . +0 . − . B0.5 − B0/ − G045.4790+00.1365A30 − C1 47 . +0 . − . B0/ − A30 − C2 47 . +0 . − . B0/ − A30aA30a − C0 46 . +0 . − . B0.5/ − G045.4909+00.1376(GR)G045.4904+00.1367(GC)A46 B0.5 − B0A47 O8 − O7.5 O9 − O8A47 − C0 46.93 +0 . − . B0.5 − B0/ − G045.8202-00.2866A47 − C1 46.61 +0 . − . B0.5/ − G045.8232-00.2842 (GR)A47 − C2 46.73 +0 . − . B0.5 − B0/ − G045.8266-00.2892 (GR)A50 O9.5 − O8.5 < O9.5A50 − C0 46.97 +0 . − . B0.5 − B0/ − G045.9344-00.4016 a Compact source only, ∼ ′′ in size, and therefore smaller than our aperture used forphotometry. b Compact source including the extended emission. c The closest CORNISH counterpart to this source is C54 (Table 2).
A29 (G45.47+0.05) is the most prominent of all submmpeaks in this complex, and yet lacks significant emissionin the MIR (e.g., Figure 12; Figure 13). The submm peakis located in the neighborhood of 14 GR sources (fiveof which are associated with bright IR sources; Figure12). All these sources are located within ∼ ′′ of theBLAST peak. The appearance in the MIR may suggestthat the submm emission is tracing a particularly densepart of the molecular clump. This material could beconfining the expansion of the photodissociation region(PDR) as seen in IRAC, which also appears to be in avery young and embedded stage of star formation. Pillar-like structures seen in extinction and extending from A29into G45.45 (Figure 12), and the main five IR detectionsembedded within the BLAST source (as suggested by their flux increasing with increasing wavelength) supportthis scenario.The brightest CORNISH source in the neighborhoodof the submm peak, A16 − C0 (Figure 14), is a knownUCH ii R (WC89, Testi et al. 1999 center agreement < ′′ ). The flux from our radio analysis is equivalent toan O9.5 radio ZAMS star at 7 kpc, which agrees withthe spectral type we derived using the 6 cm flux fromUrquhart et al. (2009). This source is also one of themost complex of the clump, and contains H O (e.g.,Forster & Caswell 1989), OH (e.g., Forster & Caswell1989; Argon et al. 2000) and methanol (e.g., Menten1991) masers. The most prominent OH sources are lo-cated closer ( < . ′′ ) to the radio peak than the methanoland H O masers ( ∼ ′′ ), and they all lie preferentially to-4 Rivera-Ingraham, A. et al. Fig. 12.—
Greyscale IRAC 8 µ m image of IRAS 19120+1103(A28 − A29) with 250 µ m BLAST contours overlaid. Crosses markthe position of main GR sources. Contours are from 5% to 55% ofthe map peak value of 31500 MJy sr − in 10% steps. Other symbolslike Fig.8. Fig. 13.—
Greyscale IRAC 8 µ m image of most central regionsof A28 and A29 in Fig.12 with CORNISH contours. Contours arefrom 10% to 90% of map peak value of 0.07 Jy beam − in 10%steps. wards the northern (upper left direction; Figure 14) rimof the radio emission and towards the extended MIR re-gion.In the IRAC maps, the GR source(G045.4661+00.0457; G3 in Figure 14) is at thepeak of the IR emission, at the opposite corner of theMIR elongation to the CORNISH source (at ∼ ′′ ).Other GR sources are also present nearby the radiopeak. Such astrometry differences between the ra-dio and IR detections have been previously observed(De Buizer et al. 2005), which confirms this to be a truephysical separation. The MIR elongation may be tracingthe outflow morphology detected by Hunter et al. (1997)and the NH emission (e.g., Hofner et al. 1999). Mostmaser sources are indeed located between the MIR peak(G3) and the radio peak, along the elongation, with afew OH masers located between the radio source and G2(Figure 14). At the northern extreme edge of the elon-gation and closer to the main MIR peak there are more detections of methanol maser signatures (Kurtz et al.2004), as well as SiO and NH emission peaks ( ∼ ′′ from the radio peak; Hofner et al. 1999). The presenceof shocked gas along the northern MIR emission, theoutflow, and the location of the UCH ii R opposite themain MIR peak may suggest the scenario where theoutflow/jet originating at the UCH ii R interacts withits local environment, producing the observed structurein the MIR. An alternative interpretation claims thiselongation may arise from accretion (De Buizer et al.2005) or collapse (e.g., Cesaroni et al. 1992; Hofner et al.1999) onto the UCH ii R. This could explain the emissionand redshifted absorption observed in NH . Morerecent studies have not confirmed the presence of infallsignatures (e.g., Wilner et al. 1996; Klaassen & Wilson2007). Further analysis of the innermost regions isneeded to solve this controversy. Fig. 14.—
Greyscale IRAC 8 µ m image of region around the mainUCH ii R (A29 − C0; C0 in the image) within A29 (Figure 12) withCORNISH contours superimposed. Contours are from 10% to 60%of map peak value of 0.07 Jy beam − in 10% steps. Figure showsclosest IR counterparts retrieved from the GLIMPSE I completecatalog (GC), labeled as G1, G2 and G3. The maser emission (especially methanol and H O)suggests that this source is one of the youngest in thiscomplex. It has also been classified as an ExtendedGreen Object (EGO) and a likely MYSO outflow candi-date (Cyganowski et al. 2008). This supports the HCOanalysis of Wilner et al. (1996), who suggested that thissource is in the early stages of forming an OB star cluster.
G45.45
A28 is close to the most active region in the cloud asobserved in the MIR (G45.45+0.06 [G45.45]), althoughfrom its position and extended morphology the submmemission may also be tracing the compressed and ex-tended molecular gas. G45.45 (also a MYSO candidatein the RMS Survey; e.g., Mottram et al. 2010) has beenobserved to lie in the border of a larger and fainter H II region ∼ ′ in size (G45L; Paron et al. 2009). Althoughthis structure is also traced by the BLAST images, it hasnot been included in our photometry/radio analysis.The IRAC images show a complex morphology, withthe strongest emission in the MIR and 21 cm coincidentwith the main nebula-like radio structure observed in theCORNISH data (e.g., Figure 12; Figure 13). In Figure13 the MIR emission appears to follow a horseshoe shapehe BLAST View of Aquila 15around a cavity-like structure ( ∼ ∼ ′′ resolution, thedetails and morphology of the dust in this region remainunresolved in our BLAST maps.In the radio, the CORNISH data reveal a similarlycomplex substructure for G45.45 (Figure 15). There are18 radio peaks detected within and surrounding the ra-dio ‘nebula’, coincident with the brightest area in theGLIMPSE images. Within this extended radio emis-sion, called ‘The Orion nebula’s younger brother’ byFeldt et al. (1998), numerous emission peaks are notice-able. While we cannot easily distinguish or fit thesepeaks, we detect at least eight within an estimated size of0 . × . II regions(e.g., Garay et al. 1993; Testi et al. 1999). Aperture pho-tometry on the whole structure (including extended emis-sion) yields a radio flux density comparable to that of an ∼ O5.5 ZAMS spectral type ( ∼ O5 class V) star, which isin agreement with previous estimates (e.g., Garay et al.1993). Using the 6 cm flux from Urquhart et al. (2009)for a source major axis of ∼ ′′ , we obtain an estimateof ∼ O6.5. This is comparable to the results we obtainusing the flux estimates from Testi et al. (1999; Table4).
Fig. 15.—
Detailed greyscale CORNISH image of central UCH ii Rnear A28 (part of IRAS 19120+1103; Fig.12; Fig.13), with num-bered emission peaks (Table 2). Contours like Fig.13.
Regarding the stellar content, Feldt et al. (1998) de-tected up to 14 NIR sources (from a - o ) possibly associ-ated with this complex. They also detected additionalmid-infrared (MIR) sources outside the main radio neb-ula (Figure 16). The roman numbers indicate other pointsources in their NIR images outside their VLA map. Weconfirm their observations that the majority of these ob-jects lie on the sharp and distorted upper edge of theradio emission (Figure 16). This may support the sce-nario proposed by these authors where a central clusterof OB stars, deeply embedded within the radio complex,produces a front that has triggered further star forma-tion. In their analysis, they claim that IR sources l , m , n , o (Figure 16) may be the source of the UCH ii R. Al-though these objects do lie close to two bright radio peakswithin the cluster (A28 − C13, A28 − C11; Table 5), theirsource b is the closest to the brightest peak in the ra-dio (A28 − C15 in Figure 16). This CORNISH source liesat less than ∼ ′′ from both the WC89 coordinates andsource b . Fig. 16.—
More detailed greyscale CORNISH image of inner-most regions of the central UCH ii R in Fig.15 with numbered emis-sion peaks (Table 2). Letters are NIR detections from Feldt et al.(1998) falling within VLA map (Table 5). Roman numbers areother NIR detections (Feldt et al. 1998). Contours like Fig.13.
At a resolution of 0 ′′ .4, WC89 defined this sourceas a cometary UCH ii R. Indeed, two parallel extensionsappear to emerge from the central source A28 − C15.These structures form a tail-like morphology extendingtowards the right in Figure 16, within which A28 − C13,A28 − C14, and A28 − C11 are detected. In total, we findthat eight of these IR sources have CORNISH counter-parts within ∼ ′′ . Sometimes one radio peak is foundbetween several in the NIR (Table 5; Figure 16).Blum & McGregor (2008) classified the main radiostructure as a group of MYSOs with late and early Bstars surrounding the central source, probably similar tothe central cluster powering G45.12 within A16. The off-set between the NIR and radio peaks could be explainedif the radio detections are dense clumps ionized by thesurrounding massive stars (Feldt et al. 1998). Alterna-tively, we do not discard the possibility that the NIRstars may have been produced by the central and em-bedded star/cluster, whose expanding H II region couldhave triggered the formation of these sources by com-pression of the dense material traced in the submm. Thislast scenario is supported by the overall morphology inthe CORNISH images; the observed emission supportsA28 − C15, the brightest radio source, as being respon-sible for the origin of l , m , n , o , rather than the lattersources being the actual ‘ground zero’ for the triggeringmechanism (as suggested by Feldt et al. 1998). Furtherinvestigation at high resolution is required to corroboratethe triggering hypothesis and to fully distinguish betweenthe different cases. TABLE 54.8 GHz radio (CORNISH) sources with IR counterparts(Feldt et al. 1998) within 1 ′′ . IR Radiob A28 − C15d A28 − C10f A28 − C11l A28 − C11m A28 − C11n A28 − C11o A28 − C13MIR1 A28 − C10
Fig. 17.—
Greyscale CORNISH image of elongated (and bright-est) radio emission in A30 − A30a (IRAS 19117+1107; Complex 2in Table 4); with numbered emission peaks (Table 2). Contoursare from 10% to 25% of map peak value of 0.07 Jy beam − in 3%steps. The candidate counterpart to MIR1 (A28 − C10) isclearly visible in the CORNISH data, albeit relativelyweak compared to the most central sources. This weakemission is in contrast with the strong IR luminosity ofthis source. In combination with the nearby OH maser(Argon et al. 2000), this may again suggest that at leastsome structures are actual stars still embedded withintheir natal cocoons (e.g., Kraemer et al. 2003).The remaining possible radio detections within ∼ ′ and not lying within the main complex have been in-cluded in Table 4. Due to the complexity of the radiostructures around this complex, we do not discard thepresence of additional sources in this region (e.g., Figure15). G45.48
AA30 (G45.48; north of AA29 in Figure 11) also showscomplex structure in the submm and IR. Our two submmpeaks lie at opposite sides of the main emission visiblein the IRAC images. As in previous cases, they may betracing relatively cold, dense gas that is confining theexpansion of the H II region.WC89 classified this UCH ii R as irregular, but sug-gested that the elongated form could be due to an imag-ing artifact. Testi et al. (1999) identified no compactsources, only extended emission. The elongation of thissource, as well as several embedded peaks, are evidentat 4.8 GHz (Figure 17), and the structure is identified inthe MIR images as the equatorial ridge of the bipolar-likeMIR structure (Figure 18).Just like in G45.45, the MIR and main radio emis-sion appear to wrap around a cavity-shaped structure,within which no IRAC sources are visible. The BLASTemission includes this ‘cavity’, but any such structurewould be unresolved in our images. The adjacent ra-dio/IR ridge could be compatible with illumination fromthe south, although the main source powering the regioncould in fact be located more towards the north, closerto source A30 − C0 (Figure 18), the northern radio source
Fig. 18.—
Greyscale IRAC 8 µ m image of the H II region withinIRAS 19117+1107. Numbers as in Fig.17. Crosses mark the posi-tion of submm peaks A30 and A30a. detected by Garay et al. (1993), and the diffuse emissionin the IR (KJK1) of Kraemer et al. (2003). Only one GCwas found within ∼ ′′ of A30 − C0 (G045.4790+00.1365).KJK1 does appear to be coincident with an IRAC emis-sion peak, even though there is no counterpart in theGLIMPSE I catalogs. The irregular radio structures,and the lack of a significant radio counterpart for KJK1,could imply the presence of an embedded star/clusteraround this position, which also coincides with an opac-ity peak and is estimated to be much colder than thesouthern counterpart (Kraemer et al. 2003).The multi-peaked radio morphology of the elongatedradio structure (coincident with the southernmost sourcedetected by Garay et al. 1993 and the IR source KJK2from Kraemer et al. 2003) clearly indicates the presenceof embedded sources. Our Gaussian routine detects atleast four main peaks in a filamentary structure about ∼ . ∼ − ′′ southwest from A30 − C0 and A30 − C1. Thepresence of a GC/GR counterpart (G045.4725+00.1335)for this source and the lack of an equivalent CORNISHdetection again argues in favor of the young stage of thestellar population in this region.
BLAST A35 & A36
Away from the main complex, A35 and A36 (Figure19) also show some signatures of stellar activity, as sug-gested by their morphology.Although our BLAST peaks generally overlap well withthe emission observed in IRAC,
IRAS µ m shows poorhe BLAST View of Aquila 17correlation. Only at 60 µ m do we observe a reasonablematch with A36, the only one of these two sources witha PSC IRAS match within ∼ ′′ . This IR source, IRAS19124+1106, was estimated to be at a distance of 6.5 kpc,and has been suggested to be one of the impact sites ofthe jets emanating from the microquasar and superlu-minal source GRS 1915+105 (Kaiser et al. 2004). Theother impact site was identified as our BLAST sourceA19, a candidate MYSO from the Red MSX Source(RMS) Survey (Mottram et al. 2010). GRS 1915+105is believed to be a binary system consisting of an early-type K giant, accreting via a Roche lobe overflow ontoa black hole (e.g., Greiner 2001). The MIR structure ofA36, if associated with this IRAS source, does not re-semble what one would expect to see if caused by a jetoriginating at the position of GRS 1915+105. Further-more, the new distance estimate for GRS 1915+105 of11 kpc (Zdziarski et al. 2005) is now much larger thanthe kinematic distance to this IR/submm emission.Our analysis of the CORNISH images reveals that,with the exception of some weak structures near theemission peak of A36 (likely tracing the ionized regionas observed in the VGPS 21 cm maps), there are no ma-jor radio sources near these objects. This may suggestvery early or very late/isolated low mass star formingactivity.
Fig. 19.—
Greyscale IRAC 8 µ m image showing cometary shapeof A35+A36 with BLAST 500 µ m contours superimposed. Con-tours are from 8% to 12% of map peak value of 2153 MJy sr − in2% steps. Submm Analysis
Estimated BLAST parameters for the main objects inthis complex have been included in Table 6. The tem-peratures are warm, characteristic of active star formingclumps with ongoing stellar activity. The total mass ofAA29 is ∼ ⊙ for a temperature of ∼
35 K, whichcontrasts with the mass estimate of 26000 M ⊙ obtainedby Mooney et al. (1995) for a distance of 8.1 kpc and amuch lower fixed dust temperature of 20 K. Scaling tothis distance we obtain a total mass of ∼ ⊙ , and ∼ ⊙ for a fixed temperature of 20 K and free β (best fit β = 2 . ∼ O5.5 is in excellent agreement with the radiospectral type of the radio nebula within G45.45 (Com-plex 1 in Table 4), the most luminous system within theBLAST emission formed by A28 and A29 (AA29).The IR+submm spectral type of A30+A30a is in agree-ment with the IR spectral type estimate of Complex 2(the elongated radio emission; Table 4), but the COR-NISH radio spectral type of this substructure is consid-erably later.Although the radio flux estimates from Testi et al.(1999) at 3.6 cm and the uncertainties in the SED bolo-metric luminosities could be compatible with a relativelyoptically thin state for this source, the CORNISH mea-surements suggest a more embedded (and younger) stagefor AA30 than for AA29. Just like the clumps withinGRSMC G045.14+00.14, the BLAST sources in GRSMCG045.49+00.04 appear to be powered by the central OByoung stellar clusters, which could also be responsiblefor the additional star formation detected within theirparent clumps.
GRSMC G045.74 − − This complex is dominated by three main (sub)mmsources (Figure 20) within an extended and largely fila-mentary molecular region.
BLAST A50
In the submm, A50 (IRAS 19145+1116) is largelystructureless and symmetric, possibly with some weakemission surrounding the central peak. In the MIR, thisH II region reveals a clumpy structure and numerousMIR peaks clustered within the main submm emission.There are seven GC sources found at less than ∼ ′′ from our BLAST peak. Among the closest of these wefind a string of three sources, G045.9352 − − − ∼ ′′ from theGLIMPSE source G045.9344-00.4016, with a flux corre-sponding to a B0.5 − B0 ZAMS star. The IRAS clumpwas reported to satisfy the color criteria of WC89 forUCH ii Rs (e.g., Bronfman et al. 1996), and was reportedby Codella et al. (1995) to be possibly associated withwater masers. This would argue against the more evolvedstate of the system indicated by its ‘disturbed’ morphol-ogy, although from the coordinates provided by theseauthors we suspect that this maser emission could alsobe associated with a later generation of star formationwithin an older clump. The lack of a CORNISH or IRcounterpart for this maser may also be indicating thatthe structure is due to a low mass star.
BLAST A46
While relatively structureless in the submm, theGLIMPSE images of A46 (IRAS 19141+1110) show abow-shock cometary like structure, with the front ori-ented towards the south (lower right of Figure 20). Some8 Rivera-Ingraham, A. et al.
TABLE 6Masses and temperatures of the main BLAST sources at ∼ kpc. Source
T M c L bol Single-star Spectral Type(K) (10 M ⊙ ) (10 L ⊙ )A12 42 . ± . . ± . . ± . a /O5 b A16 39 . ± . . ± . . ± . − O5.5/O6 − O4A22 c . ± . . ± . . ± . < B0.5/ − A28 − A29 36 . ± . . ± . . ± . IRAS unresolved (and saturated) emissionO6.5 − O5.5/O7 − O4.5A30 − A30a 27 . ± . . ± . . ± . IRAS unresolved (and saturated) emissionB0 − O6.5/ < O6.5A35 33 . ± . . ± . . ± . ∼ O8/ ∼ O9A36 41 . ± . . ± . . ± . − A46 32 . ± . . ± . . ± . − B0/ − A47 37 . ± . . ± . . ± . − O7.5/O9 − O8A50 35 . ± . . ± . . ± . − O8.5/ < O9.5 a Spectral type from L bol for a ZAMS star (Panagia 1973). b Spectral type from L bol for a luminosity class V star (Martins et al. 2005). c No PSC counterpart within 30 ′′ . No BOLOCAM data available. Possibly associated (visually)with an IRAS source, but this source covers nearby BLAST sources as well and is therefore ignored in thefits. The rising SED in the submm and the lack of data at shorter wavelengths result in large error ranges. possibly associated sources towards the south and south-east of the main structure are also detected. Despite thepresence of numerous GC/GR sources, the bow-shockitself may be produced by a highly embedded source,closest to G045.8062-00.3518 (Figure 20).Even though A46 also has
IRAS , MSX , and IRACcounterparts, there appears to be negligible 21 cm emis-sion and no NVSS, 4.8 GHz emission, H O or OH masers,or any other tracers that may be indicative of ongoingstar formation. An exception is the methanol maseremission ∼ ′′ eastwards (lower left) from the BLASTpeak detected by Pandian et al. (2007). This is the5 − A + line of methanol at 6.7 GHz, the strongestof Class II methanol masers, seen exclusively near mas-sive stars. The authors suggest a very early stage ofevolution, in which methanol activity has just turnedon, before the onset of additional signs of star forma-tion. Class II maser sources are radiatively pumpedbut are believed to be quenched by the formation of anUCH ii R, which is consistent with the absence of 4.8 GHzCORNISH sources and the ‘young’ age of the system(e.g., Minier et al. 2005; Ellingsen et al. 2007). This sce-nario would also be in agreement with Cyganowski et al.(2008), who classified this source as a ‘possible’ MYSO.The observed IRAC structures and methanol emissionare all within the prominent BLAST submm emission,which also suggests the presence of local high densitymolecular material.
BLAST A47
A47 (IRAS 19139+1113) is a prominent MYSO (e.g.,Chan et al. 1996) showing clear signatures of active starformation. A prominent carved structure ( ∼ II region is the most extended feature of thiscloud, and is detectable in the IR, submm, mm, and21 cm images. The submm and radio peaks appear totrace a region of diffuse emission within this structure,close to three bright IRAC sources (G045.8263 − − − Fig. 20.—
Greyscale IRAC 8 µ m image of IRAS 19141+1110(A46), IRAS 19139+1113 (A47), and IRAS 19145+1116 (A50),with BLAST 500 µ m contours superimposed. Contours are from10% to 20% of map peak value of 2153 MJy sr − in 5% steps. Whitecrosses are CORNISH detections. ionized region in the molecular cloud, suggests that thecombined contribution from these objects results in thesinusoidal boundary of the overall region.We find three likely sources at 4.8 GHz within ∼ ′ of our BLAST source, all with GC counterparts within ∼ ′′ , and indicative of ongoing massive star formation.The extended morphology and the advanced state ofstellar activity within the main H II would support the‘older’ age suggested by the lack of maser emission (e.g.,van der Walt et al. 1995; Szymczak et al. 2000). Radio and Submm Analysis
From their measured fluxes, we estimate ZAMS spec-tral types for the radio peaks in these clumps of laterthan ∼ B0 stars. Our SED fits show that, overall, noneof the host clumps have an equivalent single-star ZAMSspectral type earlier than an ∼ O8 star. In the case ofA47, it is possible that additional sources are contribut-ing to the total luminosity, in addition to those traced inthe radio.The detection of 4.8 GHz emission confirms previoushe BLAST View of Aquila 19studies that classified A47 and A50 as UCH ii Rs from theWC89 color criteria (Bronfman et al. 1996). Althoughthe radio peaks are not coincident with the brightestIRAC sources, they clearly indicate that massive starsare indeed being formed in this cloud, albeit at a lowerlevel than that observed in the two main clouds describedabove. AQUILA IN PERSPECTIVE: THE STAR FORMINGACTIVITY IN THE BLAST 6 DEG MAP
The Submm Population and Structural Propertiesof the Aquila Field
This region of Aquila consists principally of threemain active complexes at ∼ − − ∼ ± . CO/CS emission.At ∼ ±
10 km s − the CO maps reveal a dis-persed and filamentary molecular structure covering thesize of the BLAST map. Two of the main complexesare located at the central ‘knots’ of an overall heart-shaped like morphology (Figure 2). From the catalog ofRathborne et al. (2009) and Roman-Duval et al. (2009)only five clouds are at a distance of ∼ ± . T ∼ −
35 K for β = 1 .
5) are associatedmainly with the three main complexes. Outside of thecentral regions the star forming activity as traced in thesubmm is less organized, although still following the over-all contours of the molecular emission. More ‘isolated’clumps with
IRAS counterparts (not all part of our final7 kpc sample) show typical star-forming clump tempera-tures of ∼
30 K and disturbed environments, with theirstellar content generally resolved, and in an apparentlyless embedded stage of evolution.Relatively cold structures in Aquila (T <
20 K for β = 1 . MSX ,and Peretto & Fuller (2009) found 79 candidates using
Spitzer data. We have checked for IRDC matches within30 ′′ of our submm peaks in the entire field and foundseven examples, all from the sample of Peretto & Fuller(2009). We note that several IRDCs, although not lo-cated within 30 ′′ of our submm peaks, are frequentlyclustered in their immediate neighborhood; these mayhave not be resolved in our data, or they may be confused by deconvolution structures. One prominent example ofthis is G045.49+00.04. Several IRDCs are observed inthe local regions surrounding the brightest IRAS sourceformed by A28 and A29, especially towards A29. Theintricate structures observed in the IRAC images, suchas the pillar-like structures coincident with this BLASTsource and the ‘cavity’, will require submm data withhigher resolution and sensitivity in order to be properlycharacterized. We find a similar situation for the submmcomplex labeled in Figure 2 as G046.34 − Herschel datafrom Hi-Gal.Although a more in depth study is required to confirmour results, the distribution and characteristics of thepopulation within the main clumps suggest that trigger-ing mechanisms (new star formation induced/initiated byexternal agents; e.g., Elmegreen 1992) are likely takingplace in the region. Our multiwavelength (MIR-radio)analysis is compatible with induced activity from theinnermost region to the farthest (parsec) extent of theparent clump.
Evolution and Massive Star Formation in Aquila
Fig. 21.—
Comparison of L bol (Table 6) and total Q for BLASTsources with analyzed CORNISH sources (Tables 3 & 4). Resultsare compared with theoretical curves for ZAMS (Panagia 1973) andClass V (Martins et al. 2005) stars. Example of expected effect ofincreasing (decreasing) the distance by 1 kpc shown by diagonalline of source A12. Within G045.14+00.14, our analysis in the IR, submm,and radio, the molecular data, and the maser and stellaractivity all support the scenario where A16 is in a moreevolved stage of evolution than its neighbor A12. Fig-ure 21 shows the measured bolometric luminosity for ourBLAST sources relative to the combined total number ofionizing photons per unit time for all CORNISH sourcespossibly associated with each submm source. The appar-ent underionizing state of A12 suggests optically thickradio emission, and therefore a highly embedded stage of0 Rivera-Ingraham, A. et al.the central sources.A28 likely contains the ‘older’ stellar activity of the ob-served clumps, while A29 and A30 appear to have char-acteristics of a relatively ‘younger’ population. The laterspectral type obtained from the CORNISH data for themain complex in A30 (the filamentary structure) relativeto its estimate from the IR would support the embeddedstage of the main star forming activity in this region.Although our total luminosity measurement (and the ra-dio estimates from Testi et al. 1999) are consistent withthe theoretical curve in Figure 21, the large error rangein luminosity for AA30 relative to the uncertainty in Q could still support this conclusion.Despite the apparent agreement of AA29 (A28+A29)with the theoretical models in Figure 21, the more com-pact radio emission of A29 and the weak MIR emission(compared to the prominent submm peak) would ar-gue that A29 is the youngest active part of the entirecloud. Paron et al. (2009) suggested that G45.45 itselfcould have been triggered by three possible O-type starsionizing the extended H II region G45L. Although notanalyzed in the present work, this is also a possibility forthe original site (‘first generation’) of the activity withinthe BLAST clump.A35 and A36 also have SED parameters consistentwith on-going stellar activity, but lack obvious 4.8 GHzdetections. Neither of these two sources show maseremission in the catalogs used in this work, and bothhave weaker CO and CS antenna temperature. Thesesources may thus be in a relatively young and still em-bedded stage, or the star forming activity may be lowand/or without significant massive star formation.Of the three main submm peaks in the complex formedby G045.74 − − ii R from the color cri-teria of WC89.A46 shows the weakest molecular and radio emis-sion, and no CORNISH counterparts or prominent sig-natures of star forming activity. However, the presenceof methanol emission and the possible association withan EGO suggest that this clump is in a very early anddeeply embedded stage of massive star formation.A47 shows not only more extended emission at allwavelengths, but it also appears to contain a few asso-ciated CORNISH sources within the main H II region.The lack of any obvious maser emission, its morphology,the high dust temperatures, and weak molecular emis-sion indicate that this clump has the most evolved stel-lar activity of the entire complex. The weak CO andCS antenna temperatures for this source could also beexplained by the more evolved stage of the system.From the results in Figure 21, both A47 and A50 ap-pear to be underionizing for their luminosity. This couldbe an indication that the total luminosity has signifi-cant contribution from several ‘cooler’ stars. However,the presence of water masers and CORNISH detectionsmay still suggest that unaccounted very optically thickradio emission, from a new embedded generation of starformation in these clumps, could also be a possibility. CONCLUSION
By means of the submillimeter maps provided byBLAST at 250, 350, and 500 µ m, together with IRACimaging, 21 cm continuum emission, 4.8 GHz CORNISHradio interferometry data, and GRS FCRAO CO/CSmolecular datacubes, we have characterized the mainclump population in the region of Aquila.Our SED fitting of the most prominent star-formingsources at a distance of ∼ T ∼
35 K and 40 K(for β = 1 . ∼ B0 stars.The 4.8 GHz interferometry maps have been used toinvestigate the UCH ii Rs within the submm clumps. TheZAMS spectral types estimated from the CORNISH dataare overall in good agreement with previous results. The‘later’ types obtained for some sources relative to their IRestimates support our BLAST and maser/outflow analy-sis, which suggest that highly embedded young OB stel-lar clusters are powering the most active clumps in theregion.On-going massive star formation is most prominentin G045.49+00.04 and G045.14+00.14 (containing ourBLAST sources A12, A16, and A28, A29, A30, respec-tively). We confirm the presence of an OB stellar clus-ter deep within IRAS 19111+1048 (A16), containing abright ∼ O6 star surrounded by numerous late O andearly B stars. This is in contrast with the scarcer maserand 4.8 GHz emission towards the complex formed byG045.74 − − II regions and a prominent IR stellar population), to theearliest stages of massive star formation detected so farin this field (A46, prior to the onset of significant maseremission and UCH ii Rs). The parameters derived fromthese SEDs are typical of active clumps and are indeedsuggestive of massive star formation, although at a lowerlevel to that observed in the previous two clouds.The enhanced datasets that will be provided by
Her-schel (Hi-GAL) and SCUBA-2 at JCMT (JCMT Galac-tic Plane Survey; Moore et al. 2005) will be crucial tofully characterize and complete the census of the clumppopulation in this field, especially the fainter and thecoldest structures. In addition, the higher resolutionof these instruments will help to probe down to corescales and to investigate the dusty structures within theclumps, which appear to be channeling the stellar activ-ity and shaping the ionized regions in the neighborhoodof the embedded OB stellar clusters.The BLAST collaboration acknowledges the support ofNASA through grants NAG5-12785, NAG5-13301, andNNGO-6GI11G, the Canadian Space Agency (CSA), theUK Particle Physics and Astronomy Research Council(PPARC), the Canada Foundation for Innovation (CFI),the Ontario Innovation Trust (OIT), and Canada’sNatural Sciences and Engineering Research Council(NSERC). We would also like to thank the Columbia Sci-entific Balloon Facility (CSBF) staff for their outstandinghe BLAST View of Aquila 21work. We also thank the referee for very useful sugges- tions and improvements to our paper, and Mubdi Rah-man for useful discussions.
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