J/ApJ/706/83 Embedded YSO candidates in W51 (Kang+, 2009)
Embedded young stellar object candidates in the active star-forming complex W51:
mass function and spatial distribution.
Kang M., Bieging J.H., Povich M.S., Lee Y.
<Astrophys. J., 706, 83-93 (2009)>
=2009ApJ...706...83K 2009ApJ...706...83K
ADC_Keywords: H II regions ; Photometry, infrared ; YSOs ;
Molecular clouds
Keywords: H II regions - infrared: ISM - ISM: individual (W51) -
stars: formation
Abstract:
We present 737 candidate young stellar objects (YSOs) near the W51
giant molecular cloud over an area of 1.25x1.00° selected from
Spitzer Space Telescope data. We use spectral energy distribution fits
to identify YSOs and distinguish them from main-sequence (MS) or red
giant stars, asymptotic giant branch stars, and background galaxies.
Based on extinction of each YSO, we separate a total of 437 YSOs
associated with the W51 region from the possible foreground sources.
We identify 69 highly embedded Stage 0/I candidate YSOs in our field
with masses >5M☉ (corresponding to mid- to early-B MS spectral
types), 46 of which are located in the central active star-forming
regions of W51A and W51B. From the YSOs associated with W51, we find
evidence for mass segregation showing that the most massive YSOs are
concentrated on the W51 HII region complex.
Description:
To understand the interaction of molecular clouds and YSOs in the W51
HII region complex, we mapped a 1.25x1.0° region in the J=2-1
transitions of 12CO and 13CO with the 10m Heinrich Hertz Telescope
(HHT) on Mount Graham, Arizona. The molecular line maps will be
presented in a separate paper (J. Bieging et al. 2010, Cat.
J/ApJS/191/232). In the present paper, we use Spitzer data for
identifying the YSO candidates associated with the molecular clouds.
The Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE
I; Benjamin et al. 2003PASP..115..953B 2003PASP..115..953B) survey covered the Galactic
plane with the four mid-IR bands (3.6, 4.5, 5.8, and 8.0um) of the
Infrared Array Camera (IRAC) on the Spitzer Space Telescope. MIPSGAL
(Carey et al. 2005AAS...207.6333C 2005AAS...207.6333C) is a legacy program covering the
inner Galactic plane, at 24 and 70um with the Multiband Imaging
Photometer for Spitzer (MIPS). The resolution of the 24um mosaics from
the MIPSGAL survey is 2.4"/pixel.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 79 737 Magnitudes of YSO candidates
table3.dat 88 737 Model parameters for YSO candidates
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See also:
II/293 : GLIMPSE Source Catalog (I + II + 3D) (IPAC 2008)
VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)
V/112 : Catalog of Star-Forming Regions in the Galaxy (Avedisova, 2002)
J/ApJS/191/232 : CO survey of W51 molecular cloud (Bieging+, 2010)
J/ApJ/685/1005 : Spitzer and high-mass star forming regions (Qiu+, 2008)
J/MNRAS/353/1025 : JHK photometry of 4 W51 star clusters (Nanda+, 2004)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq Running index number (<[KBP2009] NNN> in Simbad)
5- 11 A7 --- --- [SSTGLMC]
13- 29 A17 --- SSTGLMC IRAC designation (GLLL.llll+BB.bbbb)
31- 35 F5.2 mag Jmag ? 2MASS J band magnitude
37- 41 F5.2 mag Hmag ? 2MASS H band magnitude
43- 47 F5.2 mag Ksmag ? 2MASS Ks band magnitude
49- 53 F5.2 mag [3.6] ? Spitzer/IRAC 3.6 micron filter magnitude
55- 59 F5.2 mag [4.5] ? Spitzer/IRAC 4.5 micron filter magnitude
61- 65 F5.2 mag [5.8] ? Spitzer/IRAC 5.8 micron filter magnitude
67- 71 F5.2 mag [8.0] ? Spitzer/IRAC 8.0 micron filter magnitude
73- 77 F5.2 mag [24] ? Spitzer/MIPS 24 micron filter magnitude
79 A1 --- A [W/F] W=Associated with W51, or
F=foreground by AV
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq Running index number (<[KBP2009] NNN> in Simbad)
4 A1 --- f_Seq [*] *: Strange upper and lower values for this
object; take with caution (flag added by CDS)
6- 22 A17 --- SSTGLMC Source name (GLLL.llll+BB.bbbb)
24- 27 F4.1 mag b_AV Lower 68% (or 95%) probability limit in AV
29- 32 F4.1 mag AV Average V band extinction
34 A1 --- n_AV [*] Range on AV is 95% probability
36- 39 F4.1 mag B_AV Upper 68% (or 95%) probability limit in AV
41- 44 F4.1 Msun b_Mstar Lower 68% (or 95%) probability limit in Mstar
46- 49 F4.1 Msun Mstar Average central star mass
51 A1 --- n_Mstar [*] Range on Mstar is 95% probability
53- 56 F4.1 Msun B_Mstar Upper 68% (or 95%) probability limit in Mstar
58- 62 I5 Lsun b_Ltot Lower 68% (or 95%) probability limit in LTot
64- 68 I5 Lsun Ltot Average total luminosity
70 A1 --- n_Ltot [*] Range on Ltot is 95% probability
72- 76 I5 Lsun B_Ltot Upper 68% (or 95%) probability limit in LTot
78- 80 A3 --- Stg Evolutionary stage (Amb: Ambiguous source)
82- 84 A3 --- Cl1 YSO class based on IRAC data (2)
86- 88 A3 --- Cl2 YSO class based on the spectral slope α i
between 2 and 24um (2)
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Note (2): Based on spectral slope α using the flux densities detected
in all four IRAC bands. The spectral index is:
α=(dlog[λF(λ)])/dlogλ where λ is the
wavelength and F(λ) is the flux at that wavelength. We obtain
α from a linear fit to the logarithm of the fluxes for all four
IRAC bands and then classify YSOs as follows:
I = Class I sources with 0.3≤α,
F = "Flat" sources with -0.3≤α<0.3,
II = Class II sources with -1.6≤α< -0.3,
III = Class III sources with α< -1.6
(Lada 1987IAUS..115....1L 1987IAUS..115....1L; Greene et al. 1994ApJ...434..614G 1994ApJ...434..614G).
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 09-Dec-2011