J/ApJ/813/25 YSO candidates in W49 observed with Spitzer (Saral+, 2015)
Young stellar objects in the massive star-forming region W49.
Saral G., Hora J.L., Willis S.E., Koenig X.P., Gutermuth R.A., Saygac A.T.
<Astrophys. J., 813, 25 (2015)>
=2015ApJ...813...25S 2015ApJ...813...25S (SIMBAD/NED BibCode)
ADC_Keywords: YSOs ; Photometry, infrared ; Stars, ages
Keywords: infrared: stars; stars: early-type; stars: formation;
stars: pre-main sequence
Abstract:
We present the initial results of our investigation of the
star-forming complex W49, one of the youngest and most luminous
massive star-forming regions in our Galaxy. We used Spitzer/Infrared
Array Camera (IRAC) data to investigate massive star formation with
the primary objective of locating a representative set of protostars
and the clusters of young stars that are forming around them. We
present our source catalog with the mosaics from the IRAC data. In
this study we used a combination of IRAC, MIPS, Two Micron All Sky
Survey, and UKIRT Deep Infrared Sky Survey (UKIDSS) data to identify
and classify the young stellar objects (YSOs). We identified 232 Class
0/I YSOs, 907 Class II YSOs, and 74 transition disk candidate objects
using color-color and color-magnitude diagrams. In addition, to
understand the evolution of star formation in W49, we analyzed the
distribution of YSOs in the region to identify clusters using a
minimal spanning tree method. The fraction of YSOs that belong to
clusters with ≥7 members is found to be 52% for a cutoff distance of
96", and the ratio of Class II/I objects is 2.1. We compared the W49
region to the G305 and G333 star-forming regions and concluded that
W49 has the richest population, with seven subclusters of YSOs.
Description:
We assembled the mid-infrared Spitzer/IRAC observations of the W49
region obtained with the Spitzer IRAC instrument at 3.6, 4.5, 5.8, and
8.0um spanning 2003 Oct 02 to 2012 Dec 01. The data are from several
projects, including the following project IDs: 631 (PI: G. Fazio), 63
(J. Houck), 187 (GLIMPSE; E. Churchwell), and 80074 (Deep GLIMPSE; B.
Whitney).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table4.dat 187 332442 Source list
table6.dat 93 20 WISE YSO source list
table10.dat 83 16 Physical parameters of massive YSO candidates
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See also:
II/328 : AllWISE Data Release (Cutri+ 2013)
II/316 : UKIDSS-DR6 Galactic Plane Survey (Lucas+ 2012)
II/293 : GLIMPSE Source Catalog (I + II + 3D) (IPAC 2008)
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
J/AJ/150/95 : Masses and ages of YSOs in Per OB2 (Azimlu+, 2015)
J/AJ/149/64 : MIPSGAL 24µm point source catalog (Gutermuth+, 2015)
J/A+A/568/L13 : K-band spectrum of the very massive star W49nr1 (Wu+, 2014)
J/ApJS/212/2 : Molecular clouds in the 4th Galactic quadrant (Garcia+, 2014)
J/MNRAS/437/1791 : RMS survey: molecular observations (Urquhart+, 2014)
J/ApJS/209/29 : MYStIX: Mid-IR observations and catalogs (Kuhn+, 2013)
J/ApJ/778/96 : Spitzer and NEWFIRM observations of NGC 6334 (Willis+, 2013)
J/ApJ/773/135 : Disk-bearing stars in Cygnus OB2 (Guarcello+, 2013)
J/ApJ/720/679 : Optical spectroscopy in Cygnus X region (Beerer+, 2010)
J/AJ/138/1380 : Dust clumps in the Galactic Plane (Matthews+, 2009)
J/ApJS/184/18 : Spitzer survey of young stellar clusters (Gutermuth+, 2009)
J/ApJ/688/1142 : Star formation in W5: Spitzer observations (Koenig+, 2008)
J/AJ/136/2413 : Galactic midplane Spitzer red sources (Robitaille+, 2008)
J/A+A/482/585 : JHK photometry of stars in Sh 2-212 (Deharveng+, 2008)
J/ApJ/674/336 : Spitzer observations of NGC 1333 (Gutermuth+, 2008)
J/ApJS/155/577 : H2O masers in W49 North and Sagittarius B2 (McGrath+, 2004)
J/ApJ/393/149 : W49N H2O maser outflow: distance and kinematics (Winn+, 1992)
Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 --- --- [SSTOERC]
9- 25 A17 --- SSTOERC IAU Designation (GLLL.llll+BB.bbbb) (1)
27- 36 F10.6 deg RAdeg [286.7/288.5] Right Ascension (J2000)
38- 45 F8.6 deg DEdeg [8.2/10] Declination in decimal degrees (J2000)
47- 54 F8.3 mag Jmag [4.8/26.2]?=-100 2MASS or UKIDSS J magnitude
56- 63 F8.3 mag Hmag [3.5/21.6]?=-100 2MASS or UKIDSS H magnitude
65- 72 F8.3 mag Ksmag [3.2/23.4]?=-100 2MASS or UKIDSS Ks magnitude
74- 81 F8.3 mag [3.6] [-62.1/22.8]?=-100 Spitzer/IRAC 3.6 micron
band magnitude
83- 90 F8.3 mag [4.5] [2.3/18.8]?=-100 Spitzer/IRAC 4.5 micron
band magnitude
92- 99 F8.3 mag [5.8] [-42.3/17.8]?=-100 Spitzer/IRAC 5.8 micron
band magnitude
101-108 F8.3 mag [8.0] [1.7/17]?=-100 Spitzer/IRAC 8.0 micron
band magnitude
110-116 F7.2 mag [24] [0.3/10.3]?=-100 Spitzer/MIPS 24 micron
band magnitude
118-123 F6.3 mag e_Jmag [0.01/4]?=10 Uncertainty in Jmag
125-130 F6.3 mag e_Hmag [0.01/3]?=10 Uncertainty in Hmag
132-137 F6.3 mag e_Ksmag [0.01/9.2]?=10 Uncertainty in Ksmag
139-144 F6.3 mag e_[3.6] [0/8.5]?=10 Uncertainty in [3.6]
146-151 F6.3 mag e_[4.5] [0.002/8.7]?=10 Uncertainty in [4.5]
153-158 F6.3 mag e_[5.8] [0.001/9]?=10 Uncertainty in [5.8]
160-165 F6.3 mag e_[8.0] [0.001/8.9]?=10 Uncertainty in [8.0]
167-171 F5.2 mag e_[24] [0.02/0.4]?=10 Uncertainty in [24]
173-176 I4 --- Type Object Type (2)
178-178 I1 --- Phase Object Phase (3)
180-181 A2 --- f_Type Flag on Object Type for YSO candidates (4)
183-187 F5.2 --- alpha [-5.8/7.6]? SED slope α, from Ksmag to [24]
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Note (1): SSTOERC = Spitzer Space Telescope, Origin and Evolution of Rich
Clusters
Note (2): Object Types as follows:
0 = deeply embedded (46 sources)
1 = Class I (250 sources)
2 = Class II (2839 sources)
3 = transition disks (149 sources)
99 = Class III and photospheres (247142 sources)
9 = shocked gas emission (11 sources)
29 = AGNs (4 sources)
19 = PAH galaxies (53 sources)
20 = PAH dominated sources (639 sources)
12 = AGBs (212 sources)
-100 = unclassified (81097 sources).
Note (3): Object Characterization Phase as follows:
1 = Phase I; Gutermuth et al. (2009, J/ApJS/184/18)
2 = Phase II; Gutermuth et al. (2009, J/ApJS/184/18)
0 = Phase III; Gutermuth et al. (2009, J/ApJS/184/18)
3 = AGBs, faint YSO/background contamination phase; this article, Section 2.4
Note (4): Flag on Object Type for YSO candidates:
? = YSO candidates near a bright IRAC source within 35 arcsec
uc = Faint YSOs which can be background/foreground contamination
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
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1- 11 F11.7 deg RAdeg Right Ascension in decimal degrees from
WISE (J2000) (II/328)
13- 21 F9.7 deg DEdeg Declination in decimal degrees from
WISE (J2000) (II/328)
23- 27 F5.2 mag W1mag [9.1/14.1] WISE/W1 magnitude (3.35um) (II/328)
29- 32 F4.2 mag e_W1mag [0.02/0.3] Mean error on W1mag (II/328)
34- 38 F5.2 mag W2mag WISE/W2 magnitude (4.6um) (II/328)
40- 43 F4.2 mag e_W2mag Mean error on W2 magnitude (4.6um) (II/328)
45- 48 F4.2 mag W3mag WISE/W3 magnitude (11.6um) (II/328)
50- 53 F4.2 mag e_W3mag Mean error on W3 magnitude (11.6um) (II/328)
55- 58 F4.2 mag W4mag [1.7/6.2] WISE/W4 magnitude (22.1um) (II/328)
60- 63 F4.2 mag e_W4mag [0.02/0.08] Mean error on W4mag (II/328)
65 I1 --- Cl-W [1/2] WISE Class (1)
67- 73 A7 --- --- [SSTOERC]
75- 91 A17 --- SSTOERC Matched SSTOERC Spitzer Source Name; Table 4
93 I1 --- Cl-I [1/2] IRAC Class (1)
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Note (1): IRAC/WISE Class as follows:
0 = deeply embedded
1 = Class I
2 = Class II (candidate sources)
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Byte-by-byte Description of file: table10.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Seq Massive YSO sequential running number
4- 10 A7 --- --- [SSTOERC]
12- 28 A17 --- SSTOERC SSTOERC Spitzer Source Name as in table 4
30- 39 F10.6 deg RAdeg Right Ascension in decimal degrees (J2000)
41- 48 F8.6 deg DEdeg Declination in decimal degrees (J2000)
50- 54 F5.2 Msun Mass [7.3/19] Stellar Mass derived from SED Fit (1)
56- 59 F4.2 Msun e_Mass [0/4.4] Uncertainty in Mass
61- 65 F5.2 10+3Lsun Lum [0.7/34.4] Stellar Luminosity derived
from SED Fit (1)
67- 71 F5.2 10+3Lsun e_Lum [0/23.7] Uncertainty in Lum
73- 76 F4.2 10+6yr Age [0.02/3] Stellar Age derived from SED Fit (1)
78- 81 F4.2 10+6yr e_Age [0/1] Uncertainty in Age
83 I1 --- Cl [1/3] Massive YSO Class (2)
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Note (1): SED Fit following Azimlu et al. (2015, J/AJ/150/95)
Note (2): IRAC Class as follows:
1 = Class I
2 = Class II
3 = transition disk
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 10-Feb-2016