J/ApJ/802/59 A search for YSO candidates in IRDC G53.2 (Kim+, 2015)
Star formation activity in the long, filamentary infrared dark cloud G53.2.
Kim H.-J., Koo B.-C., Davis C.J.
<Astrophys. J., 802, 59 (2015)>
=2015ApJ...802...59K 2015ApJ...802...59K
ADC_Keywords: Molecular clouds ; Photometry, infrared ; YSOs
Keywords: infrared: stars; ISM: clouds; stars: formation;
stars: pre-main sequence
Abstract:
We present star formation activity in the infrared dark cloud (IRDC)
G53.2, a remarkable IRDC located at Galactic coordinates
(l,b)~(53.2°,0.0°) based on the census of young stellar object
(YSO) candidates. IRDC G53.2 was previously identified as several
IRDCs in mid-IR images, but it is in fact a long (≳45pc) cloud, well
consistent with a CO cloud at v∼23km/s (or at d∼1.7kpc). We present a
point-source catalog of IRDC G53.2 that contains ∼370 sources from our
photometry of the Spitzer MIPS 24µm data and Galactic Legacy
Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) Catalog. The
classification of the identified sources based on their spectral index
and control field analysis to remove field star contamination reveals
that IRDC G53.2 is an active star-forming region with ∼300 YSO
candidates. We compare the YSO classification based on spectral index,
mid-IR colors, and the wavelength range used, which results in
consistent classification, except for flat-spectrum objects, with some
ambiguity between Class I and II. Comparison of the YSO population in
IRDC G53.2 with those of other nearby star-forming clusters indicates
that they are similar in age; on the other hand, stronger association
with mid-IR stellar sources in IRDC G53.2 compared with other IRDCs
indicates that IRDC G53.2 is at a later evolutionary stage among
IRDCs. Spatial distribution of the YSO candidates in IRDC G53.2 shows
a good correlation with 13CO column density and far-IR emission, and
earlier-class objects tend to be more clustered in the regions with
higher density.
Description:
We make a point-source catalog (PSC) of IRDC G53.2 region to search
for YSO candidates. We use two Spitzer inner Galactic plane surveys as
a major data set in this study: GLIMPSE and MIPS GALactic plane survey
(MIPSGAL; Carey et al. 2009PASP..121...76C 2009PASP..121...76C). These Spitzer legacy
programs cover the inner Galactic plane at the four IRAC bands of 3.6,
4.5, 5.8, and 8.0um (GLIMPSE) and the two MIPS bands of 24 and 70um
(MIPSGAL). Other published catalogs such as the Two Micron All Sky
Survey (2MASS) PSC (Skrutskie et al. 2006, VII/233) and MSX PSC (Egan
et al. 2003, V/114) are also used as complements.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 147 369 Point-source catalog of IRDC G53.2
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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/114 : MSX6C Infrared Point Source Catalog (Egan+ 2003)
II/316 : UKIDSS-DR6 Galactic Plane Survey (Lucas+ 2012)
J/AJ/149/64 : MIPSGAL 24µm point source catalog (Gutermuth+, 2015)
J/ApJS/193/25 : The NAN complex. II. MIPS observations (Rebull+, 2011)
J/ApJ/723/492 : Physical properties of GRS mol. clouds (Roman-Duval+, 2010)
J/A+A/505/405 : A catalogue of Spitzer dark clouds (Peretto+, 2009)
J/ApJS/184/18 : Spitzer survey of young stellar clusters (Gutermuth+, 2009)
J/ApJ/699/1092 : Giant molecular clouds (SRBY) (Heyer+, 2009)
J/ApJ/698/324 : Spitzer IRDCs (Ragan+, 2009)
J/ApJS/181/321 : Properties of Spitzer c2d dark clouds (Evans+, 2009)
J/ApJ/653/1325 : Galactic distribution of infrared dark clouds (Simon+, 2006)
J/ApJ/641/389 : Millimetric observations of IRDC cores (Rathborne+, 2006)
J/ApJ/639/227 : MSX IRDC candidate catalog (Simon+, 2006)
http://www.astro.wisc.edu/glimpse/glimpsedata.html : GLIMPSE home page
http://www.ipac.caltech.edu/2mass/releases/allsky/ : 2MASS all-sky home page
http://irsa.ipac.caltech.edu/data/SPITZER/MIPSGAL/ : MIPSGAL on NASA/IPAC IRSA
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 [1/369] Running sequence number
5- 6 I2 h RAh [19] Hour of Right Ascension (J2000)
8- 9 I2 min RAm [28/31] Minute of Right Ascension (J2000)
11- 15 F5.2 s RAs Second of Right Ascension (J2000)
17 A1 --- DE- [+] Sign of Declination (J2000)
18- 19 I2 deg DEd [17/18] Degree of Declination (J2000)
21- 22 I2 arcmin DEm Arcminute of Declination (J2000)
24- 28 F5.2 arcsec DEs Arcsecond of Declination (J2000)
30- 34 F5.2 mag Jmag [7.7/17.6]? 2MASS J band magnitude
36- 40 F5.3 mag e_Jmag [0.01/0.3]? Uncertainty in Jmag
42- 46 F5.2 mag Hmag ? 2MASS H band magnitude
48- 52 F5.3 mag e_Hmag ? Uncertainty in Hmag
54- 58 F5.2 mag Kmag [4.4/14.9]? 2MASS Ks band magnitude
60- 64 F5.3 mag e_Kmag [0.01/10]? Uncertainty in Kmag
66- 70 F5.2 mag [3.6] ? Spitzer/IRAC 3.6 micron band magnitude
72- 76 F5.3 mag e_[3.6] ? Uncertainty in [3.6]
78- 82 F5.2 mag [4.5] ? Spitzer/IRAC 4.5 micron band magnitude
84- 88 F5.3 mag e_[4.5] ? Uncertainty in [4.5]
90- 94 F5.2 mag [5.8] ? Spitzer/IRAC 5.8 micron band magnitude
96-100 F5.3 mag e_[5.8] ? Uncertainty in [5.8]
102-106 F5.2 mag [8.0] [3.4/12.3]? Spitzer/IRAC 8.0um band magnitude
108-112 F5.3 mag e_[8.0] [0.01/0.4]? Uncertainty in [8.0]
114-117 F4.2 mag [24] [0.5/8.5]? Spitzer/MIPS 24um band magnitude
119-123 F5.3 mag e_[24] [0.04/0.08]? Uncertainty in [24]
125-129 F5.2 --- alpha [-2.9/2.4]? Infrared spectral index α (1)
131-134 F4.2 --- e_alpha [0.02/0.7]? The 1σ uncertainty in alpha
136-143 A8 --- Class Classification: I, II, III, "Flat", "Phot",
or "No Class" (1)
145-147 A3 --- n_Class [ad, ] Note(s) on origin or nature of source (2)
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Note (1): Defined as α=dlog(λFλ)/dlog(λ) between
3 and 24 microns (Lada 1987IAUS..115....1L 1987IAUS..115....1L). Classes are defined as:
Class I: α ≥ 0.3 (youngest protostar)
Flat: -0.3 ≤ α ≤ 0.3
Class II: -1.6 ≤ α ≤ -0.3
Class III: -2.56 ≤ α ≤ -1.6
Phot: α ≤ -2.56 (photospheric emission only)
Note (2): Flag as follows:
a = IRAC magnitudes are from the GLIMPSEI Archive;
d = a deeply embedded protostar.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 22-Jul-2015