J/ApJ/714/L285 YSO candidates in M17 SWex (Povich+, 2010)
Evidence for delayed massive star formation in the M17 proto-OB association.
Povich M.S., Whitney B.A.
<Astrophys. J., 714, L285-L289 (2010)>
=2010ApJ...714L.285P 2010ApJ...714L.285P
ADC_Keywords: Molecular clouds ; YSOs ; Photometry, infrared ; Stars, masses
Keywords: circumstellar matter - ISM: clouds - stars: formation -
stars: luminosity function, mass function
Abstract:
Through analysis of archival images and photometry from the Spitzer
GLIMPSE and MIPSGAL surveys combined with Two Micron All Sky Survey
and MSX data, we have identified 488 candidate young stellar objects
(YSOs) in the giant molecular cloud M17 SWex, which extends ∼50pc
southwest from the prominent Galactic HII region M17. Our sample
includes >200 YSOs with masses >3M☉ that will become B-type
stars on the main sequence. Extrapolating over the stellar initial
mass function (IMF), we find that M17 SWex contains >1.3x104 young
stars, representing a proto-OB association. The YSO mass function is
significantly steeper than the Salpeter IMF, and early O stars are
conspicuously absent from M17 SWex. Assuming M17 SWex will form an OB
association with a Salpeter IMF, these results reveal the combined
effects of (1) more rapid circumstellar disk evolution in more massive
YSOs and (2) delayed onset of massive star formation.
Description:
Elmegreen & Lada (1976AJ.....81.1089E 1976AJ.....81.1089E) discovered an extended
molecular cloud, which we name M17 SWex, associated with the
well-known Galactic HII region M17. The size (70pcx15pc at d=2.1kpc),
mass, and fragmentary morphology of this cloud were reminiscent of the
largest Galactic OB associations.
In this Letter, we use archival GLIMPSE and MIPSGAL data to find and
characterize individual young stellar objects (YSOs) throughout the
∼1° extent of M17 SWex.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 61 488 Basic properties of candidate YSOs
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See also:
II/293 : GLIMPSE Source Catalog (I + II + 3D) (IPAC 2008)
V/114 : MSX6C Infrared Point Source Catalog (Egan+ 2003)
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
J/ApJ/696/1278 : The extended star-forming environment of M17 (Povich+, 2009)
J/ApJ/672/398 : JHK' photometry of M17 silhouette object (Ito+, 2008)
J/ApJS/169/353 : Chandra sources in M17 (Broos+, 2007)
J/ApJ/644/990 : Sub-mm clumps at 450 and 850µm in M17 (Reid+, 2006)
http://irsa.ipac.caltech.edu/data/SPITZER/MIPSGAL/ : MIPSGAL data online
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- [PW2010] Catalog number
5- 21 A17 --- SSTGLMA GLIMPSE name (GLLL.llll+BB.bbbb; Cat. II/293)
23- 25 F3.1 mag [24] ? Spitzer/MIPS 24 micron band magnitude (1)
27 I1 --- q_[24] ? Quality flag on [24], 1=ok (2)
29- 31 F3.1 [Lsun] <logLb> Mean log bolometric luminosity
33- 35 F3.1 [Lsun] e_<logLb> The 1σ error in <logLb>
37- 40 F4.1 Msun <M*> Mean stellar mass
42- 44 F3.1 Msun e_<M*> The 1σ error in <M*>
46- 49 F4.1 [Msun/yr] <logMd> ? Mean log envelope-accretion rate (3)
51- 53 F3.1 [Msun/yr] e_<logMd> ? The 1σ in <logMd>
55- 57 A3 --- Stage [0/IA ]Evolutionary stage (A=Ambiguous)
59 A1 --- MSX? [X/ ] MSX detection; X = yes
61 A1 --- eIR? [X/ ] Excess 4.5 micron emission; X = yes
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Note (1): Typical uncertainty is ∼0.1mag.
Note (2): Quality flag as follows:
0 = non-extraction;
1 = detection;
2 = lower limit;
3 = upper limit.
Note (3): If <Mdot><10-9M☉/yr, accretion has effectively ceased,
hence <logMdot> is undefined.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 26-Apr-2012