J/ApJ/743/64 Deep infrared photometry of σ Ori cluster (Bejar+, 2011)
The substellar population of σ Orionis: a deep wide survey.
Bejar V.J.S., Zapatero Osorio M.R., Rebolo R., Caballero J.A., Barrado D.,
Martin E.L., Mundt R., Bailer-Jones C.A.L.
<Astrophys. J., 743, 64 (2011)>
=2011ApJ...743...64B 2011ApJ...743...64B
ADC_Keywords: Associations, stellar ; Photometry, infrared ; Surveys
Keywords: brown dwarfs - stars: individual (σ Orionis) - stars: low-mass -
open clusters and associations: individual (σ Orionis) -
stars: luminosity function, mass function - stars: pre-main sequence
Abstract:
We present a deep I, Z photometric survey covering a total area of
1.12deg2 of the σ Orionis cluster and reaching completeness
magnitudes of I=22 and Z=21.5mag. From I, I-Z color-magnitude diagrams
we have selected 153 candidates that fit the previously known sequence
of the cluster. They have magnitudes in the range I=16-23mag, which
corresponds to a mass interval from 0.1 down to 0.008M☉ at the
most probable age of σ Orionis (2-4Myr). Using J-band
photometry, we find that 124 of the 151 candidates within the
completeness of the optical survey (82%) follow the previously known
infrared photometric sequence of the cluster and are probably members.
We have studied the spatial distribution of the very low mass stars
and brown dwarf population of the cluster and found that there are
objects located at distances greater than 30 arcmin to the north and
west of σ Orionis that probably belong to different populations
of the Orion's Belt. For the 102 bona fide σ Orionis cluster
member candidates, we find that the radial surface density can be
represented by a decreasing exponential function
(σ=σ0e-r/r0_^) with a central density of
σ0=0.23±0.03 objects arcmin-2 and a characteristic radius
of r0=9.5±0.7 arcmin. Using near-infrared JHK-band data from Two
Micron All Sky Survey and UKIRT Deep Infrared Sky Survey and
mid-infrared data from Infrared Array Camera/Spitzer, we find that
about 5%-9% of the brown dwarf candidates in the σ Orionis
cluster have K-band excesses and 30%±7% of them show mid-infrared
excesses at wavelengths longer than 5.8um. These are probably related
to the presence of disks, most of which are "transition disks".
Description:
We obtained IZ images with the Wide Field Camera (WFC) mounted on the
Cassegrain focus of the Isaac Newton Telescope (INT) on 1998 November
12 and 13. We observed four different fields with tiny overlapping
between neighboring pointings, covering a total area of 1.12deg2.
We obtained J-band photometry with the CAIN infrared camera on the
Telescopio Carlos Sanchez (TCS) at Observatorio del Teide, on 1998
September 18, 1999 January 23, 24, February 24, August 22, 23, 24,
November 26, 27, December 28, 29, and 2000 January 27, and February
11, 12, and with the MAGIC instrument mounted on the 2.2m telescope at
the Calar Alto Observatory on 1998 December 6. We also obtained J-band
photometry for the complete area of the Bejar et al.
1999ApJ...521..671B 1999ApJ...521..671B survey on the 3.5m Calar Alto telescope in 1998
October, using the Omega-Prime instrument, which was cross-matched
with our optical photometry (See Zapatero Osorio et al.
(2000Sci...290..103Z 2000Sci...290..103Z) and Bejar et al. 2001ApJ...556..830B 2001ApJ...556..830B). For a few
objects for which the CAIN photometry has large uncertainties
(>0.2mag) or there are no available data, we have adopted the
photometry from UKIDSS DR6. We have also used available public data
from Spitzer/IRAC, belonging to the Spitzer Guaranteed Time
Observation program 37 (PI: G. Fazio).
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 165 158 Photometry and coordinates of survey candidates
table3.dat 159 158 UKIDSS and IRAC photometry
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See also:
II/319 : UKIDSS-DR9 LAS, GCS and DXS Surveys (Lawrence+ 2012)
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
J/ApJS/191/389 : Photometric monitoring in σ Ori cluster (Cody+, 2010)
J/A+A/493/931 : MAD observations of σ Ori (Bouy+, 2009)
J/A+A/478/667 : The Mayrit catalogue (Caballero, 2008)
J/A+A/488/167 : Low-mass stars in σ Ori and λ Ori (Sacco+, 2008)
J/ApJ/688/362 : Disks around brown dwarfs in sigma Ori cluster (Luhman+, 2008)
J/A+A/485/931 : Young stars and brown dwarfs in Ori OB1b (Caballero+, 2008)
J/A+A/466/917 : Brightest stars of sigma Orionis cluster (Caballero+, 2007)
J/MNRAS/356/1583 : Sigma Ori low-mass candidate members (Burningham+, 2005)
J/MNRAS/356/89 : sigma Ori low-mass stars (Kenyon+, 2005)
J/AJ/128/2316 : BVRIJHKs photometry in sigma Ori cluster (Sherry+, 2004)
J/A+A/419/249 : RJHKs photometry of sigma Ori low-mass stars (Scholz+, 2004)
J/AN/325/705 : RIJHKs of low-mass stars in sigma Ori (Bejar+, 2004)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- Field Field name (SO1 to SO4)
5- 6 A2 --- Det Detector number (D1 to D4)
8- 12 A5 --- --- [S Ori]
14- 32 A19 --- Name Position-based name (JHHMMSS.ss+DDMMSS.s)
34- 41 A8 --- OName Previous name (S Ori NN or MNNNNNNN;
<[BZR99] S Ori NN> or <Mayrit NNNNNNN> in
Simbad)
43- 44 I2 --- Ref ? Reference (1)
46- 51 F6.3 mag Imag INT/WFC Cousins I system magnitude
53- 57 F5.3 mag e_Imag Imag uncertainty
59- 63 F5.3 mag I-Z INT/WFC I-Z color index
65- 69 F5.3 mag e_I-Z I-Z uncertainty
71 A1 --- l_Jmag Limit flag on Jmag
72- 77 F6.3 mag Jmag ? CAIN J-band magnitude
79- 83 F5.3 mag e_Jmag ? Jmag uncertainty
85 A1 --- r_Jmag [abcd] Photometry source (2)
87 A1 --- l_I-J Limit flag on I-J
88- 92 F5.3 mag I-J ? I-J color index
94- 98 F5.3 mag e_I-J ? I-J uncertainty
100-105 F6.3 mag Jmag2 ? 2MASS J-band magnitude
107-111 F5.3 mag e_Jmag2 ? Jmag2 uncertainty
113-118 F6.3 mag Hmag ? 2MASS H-band magnitude
120-124 F5.3 mag e_Hmag ? Hmag uncertainty
126 A1 --- l_Ksmag Limit flag on Ksmag
127-132 F6.3 mag Ksmag ? 2MASS Ks-band magnitude
134-138 F5.3 mag e_Ksmag ? Ksmag uncertainty
140-141 I2 h RAh Hour of right ascension (J2000)
143-144 I2 min RAm Minute of right ascension (J2000)
146-150 F5.2 s RAs Second of right ascension (J2000)
152 A1 --- DE- Sign of declination (J2000)
153-154 I2 deg DEd Degree of declination (J2000)
156-157 I2 arcmin DEm Arcminute of declination (J2000)
159-162 F4.1 arcsec DEs Arcsecond of declination (J2000)
164-165 A2 --- Mm Membership code (3)
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Note (1): Reference as follows:
1 = Bejar et al. 1999 (BZOR; 1999ApJ...521..671B 1999ApJ...521..671B;
<[BZR99] S Ori NN> in Simbad);
2 = Zapatero Osorio et al. 2000Sci...290..103Z 2000Sci...290..103Z;
3 = Bejar et al. 2001 (BMZO; 2001ApJ...556..830B 2001ApJ...556..830B;
<[BMZ2001] S Ori JHHMMSS.s+DDMMSS> in Simbad);
4 = Zapatero Osorio et al. 2002A&A...384..937Z 2002A&A...384..937Z;
5 = Bejar et al. 2004, Cat. J/AN/325/705;
6 = Kenyon et al. 2005, Cat. J/MNRAS/356/89;
7 = Burningham et al. 2005, Cat. J/MNRAS/356/1583;
8 = Caballero et al. 2004A&A...424..857C 2004A&A...424..857C, 2007A&A...470..903C 2007A&A...470..903C;
9 = Caballero 2008, Cat. J/A+A/478/667;
10 = Lodieu et al. 2009A&A...505.1115L 2009A&A...505.1115L
Note (2): Photometry source flag as follows:
a = Photometry from Omega-Prime.
b = Photometry from CAIN calibrated with 2MASS.
c = Photometry from UKIDSS.
d = Photometry from MAGIC.
Note (3): Membership code as follows:
MC = Good cluster Member Candidate;
NM = Probable Non Member;
OB = Possibly belonging to the Orion Background population.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- --- [S Ori]
7- 25 A19 --- Name Position-based name (JHHMMSS.ss+DDMMSS.s)
27- 32 F6.3 mag ImagU UKIDSS I-band magnitude
34- 38 F5.3 mag e_ImagU Imag uncertainty
40- 45 F6.3 mag ZmagU ? UKIDSS Z-band magnitude
47- 51 F5.3 mag e_ZmagU ? Zmag uncertainty
53- 58 F6.3 mag YmagU ? UKIDSS Y-band magnitude
60- 64 F5.3 mag e_YmagU ? Ymag uncertainty
66- 71 F6.3 mag JmagU ? UKIDSS J-band magnitude
73- 77 F5.3 mag e_JmagU ? Jmag uncertainty
79- 84 F6.3 mag HmagU ? UKIDSS H-band magnitude
86- 90 F5.3 mag e_HmagU ? Hmag uncertainty
92- 97 F6.3 mag KmagU ? UKIDSS K-band magnitude
99-103 F5.3 mag e_KmagU ? Kmag uncertainty
105-110 F6.3 mag [3.6] ? Spitzer/IRAC 3.6um band magnitude
112-116 F5.3 mag e_[3.6] ? Uncertainty on [3.6]mag
118-123 F6.3 mag [4.5] ? Spitzer/IRAC 4.5um band magnitude
125-129 F5.3 mag e_[4.5] ? Uncertainty on [4.5]mag
131-136 F6.3 mag [5.4] ? Spitzer/IRAC 5.4um band magnitude
138-142 F5.3 mag e_[5.4] ? Uncertainty on [5.4]mag
144-149 F6.3 mag [8.0] ? Spitzer/IRAC 8.0um band magnitude
151-155 F5.3 mag e_[8.0] ? Uncertainty on [8.0]mag
157 A1 --- E(n) [YN] Near infrared excess? (Y or N)
159 A1 --- E(m) [YN] Mid-IR excess? (Y or N)
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History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 30-Apr-2013