J/ApJ/752/127 IR observations of AFGL 490 (Masiunas+, 2012)
A structural analysis of star-forming region AFGL 490.
Masiunas L.C., Gutermuth R.A., Pipher J.L., Megeath S.T., Myers P.C.,
Allen L.E., Kirk H.M., Fazio G.G.
<Astrophys. J., 752, 127 (2012)>
=2012ApJ...752..127M 2012ApJ...752..127M
ADC_Keywords: Photometry, infrared ; YSOs ; Associations, stellar
Keywords: infrared: stars; stars: formation; stars: pre-main sequence
Abstract:
We present Spitzer IRAC and MIPS observations of the star-forming
region containing intermediate-mass young stellar object (YSO)
AFGL 490. We supplement these data with near-IR Two Micron All Sky
Survey photometry and with deep Simultaneous Quad Infrared Imaging
Device observations off the central high-extinction region. We have
more than doubled the known membership of this region to 57 Class I
and 303 Class II YSOs via the combined 1-24µm photometric catalog
derived from these data. We construct and analyze the minimum spanning
tree of their projected positions, isolating one locally overdense
cluster core containing 219 YSOs (60.8% of the region's members). We
find this cluster core to be larger yet less dense than similarly
analyzed clusters. Although the structure of this cluster core appears
irregular, we demonstrate that the parsec-scale surface densities of
both YSOs and gas are correlated with a power-law slope of 2.8, as
found for other similarly analyzed nearby molecular clouds. We also
explore the mass segregation implications of AFGL 490's offset from
the center of its core, finding that it has no apparent preferential
central position relative to the low-mass members.
Description:
AFGL 490 was initially observed using Spitzer Space Telescope's IRAC
instrument at 3.6, 4.5, 5.8, and 8.0um on 2004 October 8
(AOR ID 3654656, centered on right ascension 03:27:38.60 and
declination +58:46:57.7, J2000) as part of the Guaranteed Time
Observation PID 6, "Structure and Incidence of Young Embedded
Clusters." These data were analyzed and presented by Gutermuth et al.
(2009, Cat. J/ApJS/184/18). The IRAC view of the region was expanded
to 0.51deg2 as part of the GTO "Clusters Near Clusters" program
(PID 40147).
Initial 24um MIPS images for PID 6 were obtained on 2004 September 24
(AOR ID 3663104, centered on right ascension 03:28:31.6 and
declination +58:25:37, J2000.0). The field of view was expanded on
2007 October 23 (AOR ID 21894144) as part of PID 40147. MIPS data
cover 0.38deg2.
Near-infrared imaging in J, H, and KS bands was obtained using the
Simultaneous Quad Infrared Imaging Device (SQIID) on Kitt Peak
National Observatory's 2.1m telescope on 2003 November 8. The final
mosaics have a mean integration time per position of 240s, and cover
0.05deg2, with an FWHM of 2.6, 2.5, and 2.6 pixels for J, H, and KS
bands, respectively.
The final merged source catalog includes data in J, H, and KS bands
from 2MASS and SQIID; 3.6, 4.5, 5.8, and 8.0um from IRAC; and 24um
from MIPS.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 150 363 Spitzer-identified YSOs in AFGL490 region:
IRAC, MIPS, and near-IR magnitudes
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See also:
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
J/ApJ/727/64 : Young stellar groups & their most massive stars (Kirk+, 2011)
J/ApJS/184/18 : Spitzer survey of young stellar clusters (Gutermuth+, 2009)
J/ApJS/181/321 : Properties of Spitzer c2d dark clouds (Evans+, 2009)
J/BaltA/17/1 : IR photometry in GL490 star-forming region (Straizys+ 2008)
J/AJ/126/1916 : JHK photometry of young clusters near the Sun (Porras+, 2003)
J/ApJS/94/615 : Molecular outflow sources (Hodapp, 1994)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Reg [AFGL490] Region name (AFGL490)
9- 11 I3 --- Seq YSO index number;
<[GMM2009] AFGL490 NNN> in Simbad
13- 14 I2 h RAh [3] Hour of Right Ascension (J2000)
16- 17 I2 min RAm [25/30] Minute of Right Ascension (J2000)
19- 23 F5.2 s RAs Second of Right Ascension (J2000)
25 A1 --- DE- [+] Sign of the Declination (J2000)
26- 27 I2 deg DEd [58/59] Degree of Declination (J2000)
29- 30 I2 arcmin DEm Arcminute of Declination (J2000)
32- 35 F4.1 arcsec DEs Arcsecond of Declination (J2000)
37- 41 F5.2 mag Jmag [11.2/19.3]? 2MASS or SQIID J band magnitude
43- 46 F4.2 mag e_Jmag [0.01/0.2]? Uncertainty in Jmag
48- 52 F5.2 mag Hmag [10.6/18.8]? 2MASS or SQIID H band magnitude
54- 57 F4.2 mag e_Hmag ? Uncertainty in Hmag
59- 63 F5.2 mag Kmag [9.4/17.2]? 2MASS or SQIID Ks band magnitude
65- 68 F4.2 mag e_Kmag ? Uncertainty in Kmag
70- 74 F5.2 mag [3.6] [7.3/17] Spitzer/IRAC 3.6 micron band magnitude
76- 79 F4.2 mag e_[3.6] [0.01/0.2] Uncertainty in [3.6]
81- 85 F5.2 mag [4.5] [6.4/15.4] Spitzer/IRAC 4.5µm band magnitude
87- 90 F4.2 mag e_[4.5] Uncertainty in [4.5]
92- 96 F5.2 mag [5.8] [5.9/14.8]? Spitzer/IRAC 5.8µm band magnitude
98-101 F4.2 mag e_[5.8] ? Uncertainty in [5.8]
103-107 F5.2 mag [8.0] [5/13.9]? Spitzer/IRAC 8.0µm band magnitude
109-112 F4.2 mag e_[8.0] ? Uncertainty in [8.0]
114-117 F4.2 mag [24] [0.3/9.8]? Spitzer/MIPS 24µm band magnitude
119-122 F4.2 mag e_[24] [0.01/0.2]? Uncertainty in [24]
124-127 F4.2 mag AK [0/4.2]? The Ks band extinction (1)
129-133 F5.2 --- alpha [-2.6/4.1]? Spectral index α
of IRAC bands (2)
135-137 A3 --- G09 [ *I] Gutermuth et al. 2009,
Cat. J/ApJS/184/18, classification (3)
139-148 A10 --- Class Classification from this work (same
classification as G09 + "Field star") (3)
150 A1 --- f_Class [d] d: rejected as member in this work
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Note (1): Only provided for sources with valid JHKs or HK[3.6][4.5]
photometry.
Note (2): Extinction is not accounted for in these values. High extinction
can bias αIRAC to higher values.
Note (3): Class as follows:
I = protostar with an infalling envelope;
I* = deeply embedded source;
II = pre-main sequence star with an optically thick disk;
II* = transition disk candidate.
Field star = non-member star
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 05-Feb-2014