J/AJ/144/192 Spitzer survey of Orion A and B. I. YSO catalog (Megeath+, 2012)
The Spitzer Space Telescope survey of the Orion A and B molecular clouds.
I. A census of dusty young stellar objects and a study of their mid-infrared
variability.
Megeath S.T., Gutermuth R., Muzerolle J., Kryukova E., Flaherty K.,
Hora J.L., Allen L.E., Hartmann L., Myers P.C., Pipher J.L., Stauffer J.,
Young E.T., Fazio G.G.
<Astron. J., 144, 192 (2012)>
=2012AJ....144..192M 2012AJ....144..192M
ADC_Keywords: Molecular clouds ; YSOs ; Photometry, infrared ;
Stars, pre-main sequence
Keywords: infrared: stars - ISM: individual (Orion A,Orion B) -
stars: formation - stars: variables: T Tauri - Herbig Ae/Be
Abstract:
We present a survey of the Orion A and B molecular clouds undertaken
with the IRAC and MIPS instruments on board Spitzer. In total, five
distinct fields were mapped, covering 9deg2 in five mid-IR bands
spanning 3-24µm. The survey includes the Orion Nebula Cluster, the
Lynds 1641, 1630, and 1622 dark clouds, and the NGC 2023, 2024, 2068,
and 2071 nebulae. These data are merged with the Two Micron All Sky
Survey point source catalog to generate a catalog of eight-band
photometry. We identify 3479 dusty young stellar objects (YSOs) in the
Orion molecular clouds by searching for point sources with mid-IR
colors indicative of reprocessed light from dusty disks or infalling
envelopes. The YSOs are subsequently classified on the basis of their
mid-IR colors and their spatial distributions are presented. We
classify 2991 of the YSOs as pre-main-sequence stars with disks and
488 as likely protostars. Most of the sources were observed with IRAC
in two to three epochs over six months; we search for variability
between the epochs by looking for correlated variability in the 3.6
and 4.5µm bands. We find that 50% of the dusty YSOs show
variability. The variations are typically small (∼0.2mag) with the
protostars showing a higher incidence of variability and larger
variations. The observed correlations between the 3.6, 4.5, 5.8, and
8µm variability suggests that we are observing variations in the
heating of the inner disk due to changes in the accretion luminosity
or rotating accretion hot spots.
Description:
Our Young Stellar Objects (YSOs) in the Orion A and B clouds were
identified using the IRAC and MIPS instruments on board the Spitzer
Space Telescope and the 2MASS point source catalog (cat. II/246). The
IRAC observations were taken as part of Guaranteed Time Observation
(GTO) programs and are summarized below (see table 1 in the paper for
a complete summary):
----------------------------------------------------
Field Name | 1st epoch of | 2nd epoch of |PID
| observation | observation |
----------------------------------------------------
ONC |2004 Mar 9 |2004 Oct 12 |43
L1641 |2004 Feb 16-18|2004 Oct 8, 27|43
Ori A ext. |2007 Oct 21 |2008 Apr 9-10 |30641
κ Ori ext.|2009 Mar 21-22| |50070
ONC center |2004 Oct 27 | |50
NGC 2024/23 |2004 Feb 17 |2004 Oct 27 |43
NGC 2024 |2004 Oct 8 | |50
NGC 2024 ext. |2007 Mar 30 |2007 Oct 16 |30641
NGC 2068/71 |2004 Mar 7 |2004 Oct 28 |43
L1622 |2005 Oct 27 |2006 Mar 25 |43
Ori B fil. |2007 Mar 29-30|2007 Oct 16-17|30641
Reference 1 |2005 Oct 26-29| |43
Reference 2 |2007 Oct 16 | |30641
----------------------------------------------------
The MIPS observations (obtained from GTO programs) are summarized
below (see table 2 in the paper for a complete summary):
--------------------------------
Field name | Epoch of | PID
| observation |
--------------------------------
ONC |2004 Mar 20 | 58
ONC Ext. |2008 Apr 19 |30641
L1641 |2005 Apr 2 | 47
κ Ori|2008 Nov 26-27|50070
NGC 2024/23|2005 Apr 3 | 47
NGC 2068/27|2004 Mar 15 | 58
L1622 |2005 Nov 4 | 43
Ori B fil. |2008 Apr 16 |30641
--------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table4.dat 130 3479 Spitzer-identified Young Stellar Objects
(YSOs): IRAC, MIPS, and 2MASS magnitudes
--------------------------------------------------------------------------------
See also:
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
J/MNRAS/429/775 : X-ray and mid-IR study of NGC 2023 (Lopez-Garcia+, 2013)
J/ApJS/207/5 : YSOs in LDN 1641 with Hectochelle spectra (Fang+, 2013)
J/AJ/144/31 : Spitzer+2MASS phot. of protostar candidates (Kryukova+, 2012)
J/ApJ/733/50 : Mid-IR photometry of ONC (Morales-Calderon+, 2011)
J/A+A/507/1485 : Young (proto)stellar population in L1630 (Mookerjea+ 2009)
J/ApJS/184/18 : Spitzer survey of young stellar clusters (Gutermuth+, 2009)
J/AJ/137/4072 : Infrared photometry of G216-2.5 YSOs (Megeath+, 2009)
J/A+A/504/461 : YSOs in L1630N and L1641 (Fang+, 2009)
J/AJ/135/966 : Circumstellar disk evolution in NGC 2068/71 (Flaherty+, 2008)
J/ApJ/674/336 : Spitzer observations of NGC 1333 (Gutermuth+, 2008)
J/AJ/135/966 : Circumstellar disk evolution in NGC 2068/71 (Flaherty+, 2008)
J/ApJ/676/1109 : Stars velocities in the Orion Nebula Cluster (Furesz+, 2008)
J/ApJ/669/493 : Spitzer/Chandra YSOs in Serpens cloud core (Winston+, 2007)
J/ApJ/646/1215 : Low-mass stars and brown dwarfs in NGC 2024 (Levine+, 2006)
J/AJ/126/1665 : NICMOS observations of NGC 2024 (Liu+, 2003)
J/ApJ/598/375 : Chandra X-ray observations of NGC 2024 (Skinner+, 2003)
J/ApJ/581/325 : NGC 2071 water masers (Seth+, 2002)
J/A+A/372/L41 : NGC 2068/2071 protoclusters (Motte+, 2001)
J/AJ/116/1816 : JHKLMNOPQ photometry in Orion cluster (Hillenbrand+, 1998)
J/AJ/113/1733 : Orion Nebula Cluster population (Hillenbrand 1997)
Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- Seq [1/3479] Running sequence number
6- 7 I2 h RAh Hour of Right Ascension (J2000)
9- 10 I2 min RAm Minute of Right Ascension (J2000)
12- 16 F5.2 s RAs Second of Right Ascension (J2000)
18 A1 --- DE- Sign of the Declination (J2000)
19- 20 I2 deg DEd Degree of Declination (J2000)
22- 23 I2 arcmin DEm Arcminute of Declination (J2000)
25- 28 F4.1 arcsec DEs Arcsecond of Declination (J2000)
30- 34 F5.2 mag Jmag ? 2MASS J band magnitude
36- 39 F4.2 mag e_Jmag ? Uncertainty in Jmag
41- 45 F5.2 mag Hmag ? 2MASS H band magnitude
47- 50 F4.2 mag e_Hmag ? Uncertainty in Hmag
52- 56 F5.2 mag Kmag ? 2MASS Ks band magnitude
58- 61 F4.2 mag e_Kmag ? Uncertainty in Kmag
63- 67 F5.2 mag [3.6] ? Spitzer/IRAC 3.6 micron band magnitude
69- 72 F4.2 mag e_[3.6] ? Uncertainty in [3.6] (1)
74- 78 F5.2 mag [4.5] ? Spitzer/IRAC 4.5 micron band magnitude
80- 83 F4.2 mag e_[4.5] ? Uncertainty in [4.5] (1)
85- 89 F5.2 mag [5.8] ? Spitzer/IRAC 5.8 micron band magnitude
91- 94 F4.2 mag e_[5.8] ? Uncertainty in [5.8] (1)
96-100 F5.2 mag [8.0] ? Spitzer/IRAC 8.0 micron band magnitude
102-105 F4.2 mag e_[8.0] ? Uncertainty in [8.0] (1)
107-111 F5.2 mag [24] ? Spitzer/MIPS 24 micron band magnitude
113-116 F4.2 mag e_[24] ? Uncertainty in [24] (1)
118-121 F4.2 --- AKs ? Extinction in the Ks band (2)
123-127 F5.2 --- alpha ? IRAC spectral index (αIRAC) (3)
129-130 A2 --- Cl Source classification (D, P, FP or RP) (4)
--------------------------------------------------------------------------------
Note (1): The uncertainties given are the formal uncertainties from the
extraction of the photometry. In addition to these formal
uncertainties, the IRAC and MIPS instruments have absolute calibration
uncertainties of 0.05mag.
Note (2): Only provided for sources with valid JHKs or HK[3.6][4.5]
photometry.
Note (3): Extinction is not accounted for in these values. High extinction can
bias the IRAC spectral index αIRAC to higher values.
Note (4): Class as follows:
D = Pre-main-sequence star with disk (any Young Stellar Object (YSO) with an
IR-excess that was not classified as a protostar or candidate protostar);
P = Protostar (identified by the criteria in Section 2.7.3.);
FP = Faint candidate protostar (identified by the criteria in Section 2.7.3.);
RP = Red candidate protostar (24µm detection without 4.5, 5.8 or 8µm
detection), identified by the criteria in Section 2.7.3.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Sylvain Guehenneux [CDS] 20-Jan-2014