J/ApJ/770/1 YSO candidates in G38.9-0.4 region (Alexander+, 2013)
The interstellar bubbles of G38.9-0.4 and the impact of stellar feedback on
star formation.
Alexander M.J., Kobulnicky H.A., Kerton C.R., Arvidsson K.
<Astrophys. J., 770, 1 (2013)>
=2013ApJ...770....1A 2013ApJ...770....1A
ADC_Keywords: Photometry, infrared ; YSOs ; H II regions
Keywords: H II regions; ISM: bubbles; stars: formation; stars: pre-main sequence
stars: protostars
Abstract:
We present a study of the star formation (SF) region G38.9-0.4 using
publicly available multiwavelength Galactic plane surveys from ground-
and space-based observatories. This region is composed of four bright
mid-IR bubbles and numerous infrared dark clouds. Two bubbles, N 74
and N 75, each host a star cluster anchored by a single O9.5V star. We
identified 162 young stellar objects (YSOs) and classify 54 as stage I,
7 as stage II, 6 as stage III, and 32 as ambiguous. We do not detect
the classical signposts of triggered SF, i.e., star-forming pillars or
YSOs embedded within bubble rims. We conclude that feedback-triggered
SF has not occurred in G38.9-0.4. The YSOs are preferentially
coincident with infrared dark clouds. This leads to a strong
correlation between areal YSO mass surface density and gas mass
surface density with a power law slope near 1.3, which closely matches
the Schmidt-Kennicutt Law. The correlation is similar inside and
outside the bubbles and may mean that the SF efficiency is neither
enhanced nor suppressed in regions potentially influenced by stellar
feedback. This suggests that gas density, regardless of how it is
collected, is a more important driver of SF than stellar feedback.
Larger studies should be able to quantify the fraction of all SF that
is feedback-triggered by determining the fraction SF,
feedback-compressed gas surrounding H II regions relative to that
already present in molecular clouds.
Description:
We started with the point source catalogs (PSCs) from the Spitzer
Space Telescope GLIMPSE I survey (Benjamin et al. 2003PASP..115..953B 2003PASP..115..953B).
GLIMPSE I covered the Galactic plane (10<l<65°, |b|<1°) with
1.2" pixel resolution in four bands, 3.6, 4.5, 5.8, and 8.0um. We
supplemented the 2MASS near-IR photometry with PSCs from the latest
data release (DR7) of UKIDSS. UKIDSS has a finer angular resolution
(0.8" FWHM, 0.2" pixels at K) compared to 2MASS (1" FWHM, 2" pixels).
In addition, we performed aperture photometry on 24um mosaic images
(1.2" pixels) from the Spitzer MIPSGAL survey (Carey et al.
2009PASP..121...76C 2009PASP..121...76C).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 102 162 List of candidate YSOs
table3.dat 73 162 List of candidate YSO parameters
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See also:
II/319 : UKIDSS-DR9 LAS, GCS and DXS Surveys (Lawrence+ 2012)
II/293 : GLIMPSE Source Catalog (I + II + 3D) (IPAC 2008)
VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)
J/MNRAS/424/2442 : Catalog of bubbles from Milky Way Project (Simpson+, 2012)
J/ApJ/755/20 : YSOs population of Sh2-294 with Spitzer/IRAC (Samal+, 2012)
J/ApJ/715/310 : Early stages of star formation in IRDCs (Rathborne+, 2010)
J/ApJ/712/797 : YSOs in Vul OB1 association (Billot+, 2010)
J/ApJS/184/18 : Spitzer survey of young stellar clusters (Gutermuth+, 2009)
J/AJ/136/2413 : Galactic midplane Spitzer red sources (Robitaille+, 2008)
J/AJ/136/18 : LMC SAGE. New candidate YSOs (Whitney+, 2008)
J/A+A/487/253 : The RMS survey: 13CO observations of YSOs (Urquhart+ 2008)
J/ApJ/649/759 : Bubbles in the galactic disk (Churchwell+, 2006)
J/ApJ/635/560 : New star clusters in the GLIMPSE survey (Mercer+ 2005)
J/A+A/291/943 : Protostellar cores (Ossenkopf+, 1994)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1 A1 --- --- [Y]
2- 4 I3 --- Seq [1/162] YSO running sequence number
6- 12 A7 --- --- [SSTGLMC]
13- 29 A17 --- SSTGLMC Identifier from the GLIMPSE survey
(GLLL.llll+BB.bbbb)
31- 38 F8.5 deg GLON [38.77/39.1] Galactic longitude
40- 47 F8.5 deg GLAT [-0.7/-0.2] Galactic latitude
49- 54 F6.3 mag Jmag ? J band magnitude, from 2MASS or UKIDSS (1)
56- 61 F6.3 mag Hmag ? H band magnitude, from 2MASS or UKIDSS (1)
63- 68 F6.3 mag Kmag ? Ks band magnitude, from 2MASS or UKIDSS (1)
70- 75 F6.3 mag [3.6] Spitzer/IRAC 3.6 micron band magnitude
77- 82 F6.3 mag [4.5] Spitzer/IRAC 4.5um band magnitude
84- 89 F6.3 mag [5.8] ? Spitzer/IRAC 5.8 micron band magnitude
91- 96 F6.3 mag [8.0] ? Spitzer/IRAC 8.0 micron band magnitude
98-102 F5.3 mag [24] Spitzer/MIPS 24um band magnitude
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Note (1): If the magnitude is brighter than Jmag<13.75, Hmag<13.25,
Kmag<12.5, then the data is from 2MASS and if it is fainter the
data is from UKIDSS (see Section 3.1).
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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 A1 --- --- [Y]
2- 4 I3 --- Seq [1/162] YSO running sequence number
6- 13 A8 --- Bands [013] Bands used in the fits (2)
15- 18 I4 --- Fits Number of acceptable fits
20- 23 F4.2 --- chi2 [0/8] The χ2 of the best fit model
25- 27 F3.1 Msun M*B [0.1/9.2] Best fit stellar mass
29- 31 F3.1 Msun M*A [0.6/8.8] Average fit stellar mass
33- 37 F5.2 [Msun] logMdB [-7.7/-0.5] Best fit log disk mass
39- 43 F5.2 [Msun] logMdA [-7.7/-0.9] Average fit log disk mass
45- 49 F5.2 [Msun/yr] logAcB [-8.3/-2.6]?=0 Best fit log accretion rate
51- 55 F5.2 [Msun/yr] logAcA [-9.8/-3.3]?=0 Average fit log accretion rate
57- 59 A3 --- StgB Best fit integer stage (I, II or III)
61- 63 A3 --- StgA Average fit integer stage (I, II or III)
65- 68 F4.2 --- Fstg [1/3] Average fractional stage
70- 73 F4.2 --- e_Fstg [0/0.7] Dispersion in Fstg
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Note (2): For each magnitude J H K 3.6 4.5 5.8 8.0 and 24, the flag is:
0 = band not used in the fit;
1 = band was used in the fit;
3 = band was used as an upper limit, not a true detection.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 07-Jan-2015