J/ApJ/794/124 Young star forming region NGC 2264 Spitzer sources (Rapson+, 2014)
A Spitzer view of the giant molecular cloud Mon OB1 EAST/NGC 2264.
Rapson V.A., Pipher J.L., Gutermuth R.A., Megeath S.T., Allen T.S.,
Myers P.C., Allen L.E.
<Astrophys. J., 794, 124 (2014)>
=2014ApJ...794..124R 2014ApJ...794..124R (SIMBAD/NED BibCode)
ADC_Keywords: Molecular clouds ; YSOs ; Photometry, infrared ; Infrared sources
Keywords: infrared: stars - ISM: clouds - stars: formation
Abstract:
We present Spitzer 3.6, 4.5, 5.8, 8.0, and 24 µm images of the Mon
OB1 East giant molecular cloud, which contains the young star forming
region NGC 2264, as well as more extended star formation. With Spitzer
data and Two Micron All Sky Survey photometry, we identify and
classify young stellar objects (YSOs) with dusty circumstellar disks
and/or envelopes in Mon OB1 East by their infrared-excess emission and
study their distribution with respect to cloud material. We find a
correlation between the local surface density of YSOs and column
density of molecular gas as traced by dust extinction that is roughly
described as a power law in these quantities. NGC 2264 follows a
power-law index of ∼2.7, exhibiting a large YSO surface density for a
given gas column density. Outside of NGC 2264 where the surface
density of YSOs is lower, the power law is shallower and the region
exhibits a larger gas column density for a YSO surface density,
suggesting the star formation is more recent. In order to measure the
fraction of cloud members with circumstellar disks/envelopes, we
estimate the number of diskless pre-main-sequence stars by statistical
removal of background star detections. We find that the disk fraction
of the NGC 2264 region is 45%, while the surrounding, more distributed
regions show a disk fraction of 19%. This may be explained by the
presence of an older, more dispersed population of stars. In total,
the Spitzer observations provide evidence for heterogenous, non-coeval
star formation throughout the Mon OB1 cloud.
Description:
We utilize 3.6-8.0 um images of Mon OB1 East obtained with the
Spitzer Space Telescope Infrared Array Camera (IRAC; Fazio et al.
2004ApJS..154...10F 2004ApJS..154...10F), 24 um images obtained with the Multi-Band
Imaging Photometer (MIPS; Rieke et al. 2004ApJS..154...25R 2004ApJS..154...25R), along
with 1-2.5 um NIR data from the Two Micron All Sky Survey (2MASS;
Skrutskie et al. 2006AJ....131.1163S 2006AJ....131.1163S, Cat. VII/233) to classify YSOs.
These YSOs in Mon OB1 East are classified as either protostars or
stars with circumstellar disks by their infrared excess emission above
photospheric emission. Spitzer data were gathered as part of two
Guaranteed Time Observation programs and one additional program with
the goal of studying clustered and distributed star formation
throughout Mon OB1 East and comparing the results with those of other
molecular clouds. Mon OB1 East was observed by Spitzer in 2004, 2007,
and 2008 as part of the Guaranteed Time Observation programs 37 (IRAC
data; PI: G. Fazio) and 58 (MIPS data; PI: G. Rieke), as well as
program 40006 (IRAC+MIPS data; PI: G. Fazio).
Objects:
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RA (ICRS) DE Designation(s)
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06 35 +10.1 Mon OB1 = NAME Mon I
06 40 58 +09 53.7 NGC 2264 = NAME Christmas Tree Cluster
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 102 10454 Catalog of sources detected with Spitzer Space
Telescope IRAC and MIPS instruments which are
classified as potential YSOs/field stars
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See also:
J/ApJ/642/972 : IR photometry of a star-forming core in NGC 2264 (Young+, 2006)
J/AJ/135/441 : VRIHα photometry in NGC 2264 (Sung+, 2008)
J/AJ/138/1116 : A Spitzer view of NGC 2264 (Sung+, 2009)
J/ApJ/741/35 : NIR photometry and polarization in NGC 2264 (Kwon+, 2011)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- ID Source identifier (NNNNN)
7- 8 I2 h RAh Hour of Right Ascension (J2000)
10- 11 I2 min RAm Minute of Right Ascension (J2000)
13- 17 F5.2 s RAs Second of Right Ascension (J2000)
19- 20 I2 deg DEd Degree of Declination (J2000)
22- 23 I2 arcmin DEm Arcminute of Declination (J2000)
25- 29 F5.2 arcsec DEs Arcsecond of Declination (J2000)
31- 35 F5.2 mag 3.6mag ? Spitzer/IRAC 3.6 micron band magnitude
37- 41 F5.3 mag e_3.6mag ? Uncertainty in 3.6mag
43- 47 F5.2 mag 4.5mag ? Spitzer/IRAC 4.5 micron band magnitude
49- 53 F5.3 mag e_4.5mag ? Uncertainty in 4.5mag
55- 59 F5.2 mag 5.8mag ? Spitzer/IRAC 5.8 micron band magnitude
61- 65 F5.3 mag e_5.8mag ? Uncertainty in 5.8mag
67- 71 F5.2 mag 8mag ? Spitzer/IRAC 8 micron band magnitude
73- 77 F5.3 mag e_8mag ? Uncertainty in 8mag
79- 83 F5.2 mag 24mag ? Spitzer/MIPS 24 micron band magnitude
85- 89 F5.3 mag e_24mag ? Uncertainty in 24mag
91- 95 A5 --- Class Source classification (1)
97-102 A6 --- OClass Other source classification (2)
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Note (1): Classification as follows:
0/I = Class 0/I;
II = Class II;
TD = Transition disk;
III/F = Class III/field star;
AGN = Active galactic nuclei;
PAH = Polycyclic aromatic hydrocarbon emitting source;
SHOCK = Shocked emission gas source.
Note (2): Classification as follows:
No value = Source not identified in Sung et al. (2008, J/AJ/135/441;
2009, J/AJ/138/1116);
none = Spitzer detected source identified in Sung et al.
(2008, J/AJ/135/441; 2009, J/AJ/138/1116) but not part of the
cluster;
H = Hα emission star;
h = Hα emission candidate;
X = X-ray emission star;
x = X-ray emission candidate;
+ = Hα emission star with X-ray emission, i.e. "+"="H"+"X";
- = Hα emission candidate with X-ray emission, i.e. "-"="X"+"h";
E = strong Hα emission star from spectroscopy (EWHa≥10Å
in Dahm & Simon (2005, Cat. J/AJ/129/829) or Hα index ≥2.5
in Reipurth et al. (2004, Cat. J/AJ/127/1117));
e = weak Hα emission star from spectroscopy (EWHa<10Å in
Dahm & Simon (2005, Cat. J/AJ/129/829) or Hα index ≤2 in
Reipurth et al. (2004, Cat. J/AJ/127/1117));
M = X-ray emission star with membership class "e", i.e. "M"="e"+"X";
P = X-ray emission star with membership class "E", i.e. "P"="E"+"X";
m = X-ray candidate with membership class "e", i.e. "m"="e"+"x";
p = X-ray candidate with membership class "E", i.e. "p"="E"+"x".
Other classifications explained in Sung et al. (2008, J/AJ/135/441;
2009, J/AJ/138/1116).
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History:
From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 15-May-2017