J/ApJ/750/125 Spitzer imaging of Cepheus OB3b cluster (Allen+, 2012)
Spitzer imaging of the nearby rich young cluster, Cep OB3b.
Allen T.S., Gutermuth R.A., Kryukova E., Megeath S.T., Pipher J.L.,
Naylor T., Jeffries R.D., Wolk S.J., Spitzbart B., Muzerolle J.
<Astrophys. J., 750, 125 (2012)>
=2012ApJ...750..125A 2012ApJ...750..125A
ADC_Keywords: Photometry, infrared ; YSOs ; X-ray sources ; Photometry, VRI ;
Associations, stellar
Keywords: infrared: stars - stars: formation - stars: pre-main sequence
Abstract:
We map the full extent of a rich massive young cluster in the Cep OB3b
association with the Infrared Array Camera and Multi-band Imaging
Photometer System instruments aboard the Spitzer Space Telescope and
the ACIS instrument aboard the Chandra X-Ray Observatory. At 700 pc,
it is revealed to be the second nearest large (>1000 member), young
(<5 Myr) cluster known. In contrast to the nearest large cluster, the
Orion Nebula Cluster, Cep OB3b is only lightly obscured and is mostly
located in a large cavity carved out of the surrounding molecular
cloud. Our infrared and X-ray data sets, as well as visible photometry
from the literature, are used to take a census of the young stars in
Cep OB3b. We find that the young stars within the cluster are
concentrated in two sub-clusters; an eastern sub-cluster, near the
Cep B molecular clump, and a western sub-cluster, near the Cep F
molecular clump. Using our census of young stars, we examine the
fraction of young stars with infrared excesses indicative of
circumstellar disks. We create a map of the disk fraction throughout
the cluster and find that it is spatially variable. Due to these
spatial variations, the two sub-clusters exhibit substantially
different average disk fractions from each other: 32%±4% and
50%±6%. We discuss whether the discrepant disk fractions are due to
the photodestruction of disks by the high mass members of the cluster
or whether they result from differences in the ages of the
sub-clusters. We conclude that the discrepant disk fractions are most
likely due to differences in the ages.
Description:
Mid-infrared (MIR) observations were obtained with the Spitzer IRAC
and the MIPS as part of a Spitzer Cycle-2 GO survey (PID 20403) of the
entire Cepheus OB3 molecular cloud. The molecular cloud was mapped by
IRAC at two different epochs: the first on 2005 December 25 and the
second 2006 August 8. The map was further extended in two epochs (2007
August 17 and 2008 January 31) to cover the entire Cep OB3b cluster as
part of the Spitzer program PID 40147. The Spitzer/MIPS 24um images
were obtained on 2007 February 25-26 and 2007 October 27.
X-ray data were obtained with the ACIS instrument aboard the Chandra
X-ray Observatory. Two 17'x17' fields were imaged covering both
sub-clusters. Three images of the field covering part of the eastern
sub-cluster were obtained with an aim point of 22:55:47.5,+62:38:10.3
(PIDs 9920, 10809, and 10810, with roll angles of 48°, 35°,
and 72°, respectively), and three images of the field covering the
western sub-cluster were obtained with an aim point of
22:53:31.7,+62:35:33.4 (PIDs 9919, 10811, and 10812, with roll angles
of 68°, 63°, and 63°, respectively).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 150 56 Young stellar objects: class I
table2.dat 150 1014 Young stellar objects: class II
table3.dat 150 65 Young stellar objects: transition disk
table4.dat 150 1440 Young stellar objects: class III
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See also:
B/chandra : The Chandra Archive Log (CXC, 1999-2013)
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
J/MNRAS/403/545 : Young stars in Cepheus OB3b (Littlefair+, 2010)
J/ApJ/699/1454 : YSOs around Cepheus B (Getman+, 2009)
J/MNRAS/375/1220 : BVI photometry of young stars in 10 clusters (Mayne+, 2007)
J/ApJS/163/306 : Cep B star-forming region Chandra study (Getman+, 2006)
J/MNRAS/341/805 : UBVI CCD photometry of Cep OB3b (Pozzo+, 2003)
J/A+AS/114/489 : UBVRI CCD photometry of Cepheus OB3 (Jordi+, 1995)
J/A+AS/94/519 : uvby-beta Photometry of Cep OB3 (Jordi+ 1992)
Byte-by-byte Description of file: table[1234].dat
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Bytes Format Units Label Explanations
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1- 2 I2 h RAh [22] Hour of Right Ascension (J2000) (1)
4- 5 I2 min RAm [48/59] Minute of Right Ascension (J2000) (1)
7- 11 F5.2 s RAs Second of Right Ascension (J2000) (1)
13 A1 --- DE- [+] Sign of Declination (J2000) (1)
14- 15 I2 deg DEd [62/63] Degree of Declination (J2000) (1)
17- 18 I2 arcmin DEm Arcminute of Declination (J2000) (1)
20- 24 F5.2 arcsec DEs Arcsecond of Declination (J2000) (1)
26- 32 F7.2 mag Vmag [7/29]? The V band magnitude (2)
34- 38 F5.2 mag e_Vmag [0.01/10]? Uncertainty in Vmag (2)
40- 45 F6.2 mag V-I [-0.2/8]? The (V-I) color index (2)
47- 51 F5.2 mag e_V-I [0.01/7]? Uncertainty in V-I (2)
53- 57 F5.2 mag Jmag [6/18]? 2MASS J band magnitude
59- 62 F4.2 mag e_Jmag [0.02/0.3]? Uncertainty in Jmag
64- 68 F5.2 mag Hmag [5/17]? 2MASS H band magnitude
70- 73 F4.2 mag e_Hmag [0.01/0.3]? Uncertainty in Hmag
75- 79 F5.2 mag Ksmag [4/16]? 2MASS Ks band magnitude
81- 84 F4.2 mag e_Ksmag [0.01/10]? Uncertainty in Ksmag
86- 90 F5.2 mag [3.6] [5/16] Spitzer/IRAC 3.6 micron band magnitude
92- 95 F4.2 mag e_[3.6] [0.01/0.2] Uncertainty in [3.6]
97-101 F5.2 mag [4.5] [4/16] Spitzer/IRAC 4.5 micron band magnitude
103-106 F4.2 mag e_[4.5] [0.01/0.2] Uncertainty in [4.5]
108-112 F5.2 mag [5.8] [4/15]? Spitzer/IRAC 5.8 micron band magnitude
114-117 F4.2 mag e_[5.8] [0.01/2]? Uncertainty in [5.8]
119-123 F5.2 mag [8.0] [3/16]? Spitzer/IRAC 8.0 micron band magnitude
125-128 F4.2 mag e_[8.0] [0.01/6]? Uncertainty in [8.0]
130-134 F5.2 mag [24] [1/13]? Spitzer/MIPS 24 micron band magnitude
136-139 F4.2 mag e_[24] [0.01/5]? Uncertainty in [24]
141-144 F4.2 mag AKs [0.01/0.3]?=0 KS band extinction (3)
146-150 A5 --- Note Additional notes
(X-ray = detected with Chandra)
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Note (1): From the Spitzer 3.6 micron astrometry.
Note (2): From Mayne et al. (2007, Cat. J/MNRAS/375/1220;
in Simbad).
Note (3): Determined along the line of sight to the source using the method
described in phase 2 of Section 3. These values can be converted to
AV using the relation AV=9.9*AKs.
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Nomenclature note:
Young stellar objects are <[AGK2012] JHHMMSS.ss+DDMMSS.s> in Simbad.
History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 10-Dec-2013