J/ApJS/184/18 Spitzer survey of young stellar clusters (Gutermuth+, 2009)
A Spitzer survey of young stellar clusters within one kiloparsec of the Sun:
cluster core extraction and basic structural analysis.
Gutermuth R.A., Megeath S.T., Myers P.C., Allen L.E., Pipher J.L.,
Fazio G.G.
<Astrophys. J. Suppl. Ser., 184, 18-83 (2009)>
=2009ApJS..184...18G 2009ApJS..184...18G
ADC_Keywords: YSOs ; Photometry, infrared ; Associations, stellar ; Surveys
Mission_Name: Spitzer
Keywords: infrared: stars - stars: formation - stars: pre-main sequence
Abstract:
We present a uniform mid-infrared imaging and photometric survey of 36
young, nearby, star-forming clusters and groups using Spitzer IRAC and
MIPS. We have confidently identified and classified 2548 young stellar
objects (YSOs) using recently established mid-infrared color-based
methods. We have devised and applied a new algorithm for the isolation
of local surface density enhancements from point source distributions,
enabling us to extract the overdense cores of the observed
star-forming regions for further analysis. We have compiled several
basic structural measurements of these cluster cores from the data,
such as mean surface densities of sources, cluster core radii, and
aspect ratios, in order to characterize the ranges for these
quantities. We find that a typical cluster core is 0.39pc in radius,
has 26 members with infrared excess in a ratio of Class II to Class I
sources of 3.7, is embedded in a AKs=0.8mag cloud clump, and has a
surface density of 60pc-2. We examine the nearest neighbor
distances among the YSOs in several ways, demonstrating similarity in
the spacings between Class II and Class I sources but large member
clusters appear more dense than smaller clusters. We demonstrate that
near-uniform source spacings in cluster cores are common, suggesting
that simple Jeans fragmentation of parsec-scale cloud clumps may be
the dominant process governing star formation in nearby clusters and
groups. Finally, we compare our results to other similar surveys in
the literature and discuss potential biases in the data to guide
further interpretation.
Description:
The target sample of the Spitzer survey was primarily selected from
the literature compilation of embedded clusters within 1kpc by Porras
et al. (2003, Cat. J/AJ/126/1916). The final sample includes all of
the embedded clusters in the Lada & Lada (2003ARA&A..41...57L 2003ARA&A..41...57L)
tabulation within 1kpc, with the exception of Orion and NGC 2264.
Table 2 contains the detailed information on the Spitzer data used for
each region.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 42 82 Spitzer young cluster survey observations table
table4.dat 146 2548 Spitzer-identified YSOs: IRAC, MIPS, and 2MASS
magnitudes
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See also:
J/AJ/111/1964 : JHK photometry of NGC1333 (Lada+, 1996)
J/AJ/121/974 : JHK photometry in Cha I (Gomez+, 2001)
J/ApJ/575/354 : Young stellar objects in the NGC 1333 (Getman+, 2002)
J/AJ/126/1916 : JHK photometry of young clusters near the Sun (Porras+, 2003)
J/other/ChA+A/28.308 : JHK' photometry in GGD 12-15 region (Fang+, 2004)
J/AJ/131/1574 : Infrared photometry of IC348 members (Lada+, 2006)
J/ApJ/649/862 : IR phot. of IC 348 pre-main-sequence stars (Cieza+, 2006)
J/ApJ/663/1149 : Spitzer survey of Serpens YSO population (Harvey+, 2007)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 15 A15 --- Cluster Cluster name
17- 24 I8 --- AOR Astronomical Observation Request
identification number
26- 35 A10 "YYYY/MM/DD" Date Observation date
37- 42 A6 --- SSCBCD SSC BCD calibration pipeline version used to
reduce each region
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 15 A15 --- Cluster Cluster name
17- 19 I3 --- Seq Running index number within cluster
21- 22 I2 h RAh Hour of Right Ascension (J2000)
24- 25 I2 min RAm Minute of Right Ascension (J2000)
27- 31 F5.2 s RAs Second of Right Ascension (J2000)
33 A1 --- DE- Sign of the Declination (J2000)
34- 35 I2 deg DEd Degree of Declination (J2000)
37- 38 I2 arcmin DEm Arcminute of Declination (J2000)
40- 43 F4.1 arcsec DEs Arcsecond of Declination (J2000)
45- 49 F5.2 mag Jmag ? 2MASS J band magnitude
51- 54 F4.2 mag e_Jmag ? Uncertainty in Jmag
56- 60 F5.2 mag Hmag ? 2MASS H band magnitude
62- 65 F4.2 mag e_Hmag ? Uncertainty in Hmag
67- 71 F5.2 mag Ksmag ? 2MASS KS band magnitude
73- 76 F4.2 mag e_Ksmag ? Uncertainty in Ksmag
78- 82 F5.2 mag 3.6mag ? Spitzer/IRAC 3.6um band magnitude
84- 87 F4.2 mag e_3.6mag ? Uncertainty in 3.6mag
89- 93 F5.2 mag 4.5mag ? Spitzer/IRAC 4.5um band magnitude
95- 98 F4.2 mag e_4.5mag ? Uncertainty in 4.5mag
100-104 F5.2 mag 5.8mag ? Spitzer/IRAC 5.8um band magnitude
106-109 F4.2 mag e_5.8mag ? Uncertainty in 5.8mag
111-115 F5.2 mag 8.0mag ? Spitzer/IRAC 8.0um band magnitude
117-120 F4.2 mag e_8.0mag ? Uncertainty in 8.0mag
122-126 F5.2 mag 24mag ? Spitzer/MIPS 24um band magnitude
128-131 F4.2 mag e_24mag ? Uncertainty in 24mag
133-136 F4.2 mag AKs ? The KS band extinction (1)
138-142 F5.2 --- alpha ? Mid-infrared spectral energy index (2)
144-146 A3 --- Cl Source classification (3)
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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 alpha 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.
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Nomenclature notes:
In table 4, YSOs are <[GMM2009] {Cluster} NNN>; except for
<[GMM2009] LkHA 101 NNN>.
History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 05-Feb-2010