J/ApJ/751/22 Candidates of the ρ Oph cluster (Barsony+, 2012)
A significant population of candidate new members of the ρ Ophiuchi cluster.
Barsony M., Haisch K.E., Marsh K.A., McCarthy C.
<Astrophys. J., 751, 22 (2012)>
=2012ApJ...751...22B 2012ApJ...751...22B
ADC_Keywords: Infrared sources ; Stars, pre-main sequence
Keywords: infrared: stars ; ISM: individual objects (Rho Ophiuchi) ;
stars: pre-main sequence
Abstract:
We present a general method for identifying the pre-main-sequence
population of any star-forming region, unbiased with respect to
the presence or absence of disks, in contrast to samples selected
primarily via their mid-infrared emission from Spitzer surveys. We
have applied this technique to a new, deep, wide-field, near-infrared
imaging survey of the ρ Ophiuchi cloud core to search for
candidate low-mass members. In conjunction with published Spitzer
IRAC photometry and least-squares fits of model spectra (COND, DUSTY,
NextGen, and blackbody) to the observed spectral energy distributions,
we have identified 948 candidate cloud members within our 90%
completeness limits of J=20.0, H=20.0, and Ks=18.50. This population
represents a factor of ∼3 increase in the number of known young
stellar objects in the ρ Ophiuchi cloud. A large fraction of the
candidate cluster members (81%±3%) exhibit infrared excess emission
consistent with the presence of disks, thus strengthening the
possibility of their being bona fide cloud members. Spectroscopic
follow-up will confirm the nature of individual objects, better
constrain their parameters, and allow an initial mass function to
be derived.
Description:
Observations of the ρ Ophiuchi cloud core were obtained during the
period 2008 May 23-26 with the IRIS2 NIR imager/spectrograph on the
Australian Astronomical Observatory's 4-m telescope (AAT). IRIS2
consists of a Hawaii HgCdTe 1024x1024 array that, when mounted at
the f/8 Cassegrain focus on the AAT, yields a plate scale of 0.45"/pix
with a corresponding field of view of approximately 7.7"x7.7". For all
observations, the J, Ks (1.25, 2.14um), CH4s (1.59um), and CH4l
(1.673um) filters were used. Details of our observation and data
reduction procedures for all filters are discussed in Haisch et al.
(2010ApJ...719L..90H 2010ApJ...719L..90H).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 143 948 ρ Oph low-mass candidate members
table4.dat 138 172 Photometry with recent sensitive NIR surveys
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See also:
II/289 : JKH photometry in LDN 1688 (Wilking+, 2008)
J/A+A/372/173 : ISOCAM observations of the rho Oph cloud (Bontemps+, 2001)
J/ApJ/566/993 : rho Oph (LDN 1688) cluster NICMOS imaging (Allen+, 2002)
J/ApJ/613/393 : X-ray and radio sources in ρ Oph Core A (Gagne+, 2004)
J/AJ/130/1733 : Optical spectroscopy of ρ Oph stars (Wilking+, 2005)
J/A+A/452/245 : Near-IR photometry of PMS stars in rho Oph (Natta+, 2006)
J/A+A/485/155 : HK photometry of rho Oph PMS stars (Alves de Oliveira+, 2008)
J/A+A/515/A75 : Low-mass population in ρ Oph cloud
(Alves de Oliveira+, 2010)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- ID [1/948] Index identification number
5- 6 I2 h RAh Hour of Right Ascension (J2000)
8- 9 I2 min RAm Minute of Right Ascension (J2000)
11- 15 F5.2 s RAs Second of Right Ascension (J2000)
17 A1 --- DE- Sign of the Declination (J2000)
18- 19 I2 deg DEd Degree of Declination (J2000)
21- 22 I2 arcmin DEm Arcminute of Declination (J2000)
24- 27 F4.1 arcsec DEs Arcsecond of Declination (J2000)
29- 33 F5.2 mag Jmag CIT J band magnitude (5)
35- 38 F4.2 mag e_Jmag The 1σ uncertainty in Jmag
40- 44 F5.2 mag Hmag CIT H band magnitude (5)
46- 49 F4.2 mag e_Hmag The 1σ uncertainty in Hmag
51- 55 F5.2 mag Kmag CIT Ks band magnitude (5)
57- 60 F4.2 mag e_Kmag The 1σ uncertainty in Kmag
62- 69 F8.4 mJy F3.6 ?=0.0 Spitzer/IRAC 3.6 micron band flux (1)
71- 77 F7.4 mJy e_F3.6 ?=0.0 The 1σ uncertainty in F3.6 (1)
79- 86 F8.4 mJy F4.5 ?=0.0 Spitzer/IRAC 4.5 micron band flux (1)
88- 94 F7.4 mJy e_F4.5 ?=0.0 The 1σ uncertainty in F4.5 (1)
96-103 F8.4 mJy F5.8 ?=0.0 Spitzer/IRAC 5.8 micron band flux (1)
105-111 F7.4 mJy e_F5.8 ?=0.0 The 1σ uncertainty in F5.8 (1)
113-120 F8.4 mJy F8.0 ?=0.0 Spitzer/IRAC 8.0 micron band flux (1)
122-128 F7.4 mJy e_F8.0 ?=0.0 The 1σ uncertainty in F8.0 (1)
130-133 F4.1 mag AV V band extinction (2)
135-138 I4 K Teff [730/5293] Effective temperature (3)
140 A1 --- n_Teff [BDCN] Model used for best fit (4)
142-143 A2 --- IR Excess (E) or Non-Excess (NE) source
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Note (1): "0.0000" indicates no data.
Note (2): Extinction estimates were calculated by dereddening each source in
the JHK color-color diagram as discussed in the text.
Note (3): Obtained from model fits as discussed in the text.
Note (4): Model symbol as follows (see text for details):
B = Blackbody;
D = DUSTY (1Myr isochrone of Chabrier et al. 2000ApJ...542..464C 2000ApJ...542..464C)
C = COND (1Myr isochrone of Baraffe et al. 2003A&A...402..701B 2003A&A...402..701B)
N = NextGen (Hauschildt et al. 1999ApJ...512..377H 1999ApJ...512..377H)
Note (5): All magnitudes and colors were transformed to the California
Institute of Technology (CIT) system using MKO to 2MASS and 2MASS
to CIT photometric color transformation equations and the conversion
relations of Stephens & Leggett (2004PASP..116....9S 2004PASP..116....9S; see also
http://www.astro.caltech.edu/~jmc/2mass/v3/transformations/)
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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- 2 I2 h RAh Right Ascension J2000 (hours)
4- 5 I2 min RAm Right Ascension J2000 (minutes)
7- 11 F5.2 s RAs Right Ascension J2000 (seconds)
13 A1 --- DE- Declination J2000 (sign)
14- 15 I2 deg DEd Declination J2000 (degrees)
17- 18 I2 arcmin DEm Declination J2000 (minutes)
20- 24 F5.2 arcsec DEs Declination J2000 (seconds)
27 A1 --- l_Jmag [>] J magnitude limit
28- 32 F5.2 mag Jmag J magnitude, this work
34 A1 --- n_Jmag [a] binary (3)
37 A1 --- l_Hmag [>] H magnitude limit
38- 42 F5.2 mag Hmag H magnitude, this work
44 A1 --- n_Hmag [a] binary (3)
48- 52 F5.2 mag Kmag Ks magnitude, this work
54 A1 --- n_Kmag [ab] binary or saturated (3)
58- 59 I2 --- AO ? Identification in Alves de Oliveira (1)
61- 65 F5.2 mag Jmag1 ? J magnitude, Alves de Oliveira (1)
67 A1 --- n_Jmag1 [a] binary (3)
69- 73 F5.2 mag Hmag1 ? H magnitude, Alves de Oliveira (1)
75 A1 --- n_Hmag1 [a] binary (3)
77- 81 F5.2 mag Kmag1 ? Ks magnitude, Alves de Oliveira (1)
83 A1 --- n_Kmag1 [a] binary (3)
85- 89 I5 --- M10 ? Identification in Marsh et al. 2010 (2)
90 A1 --- n_M10 [c] Individual note (3)
92- 97 F6.3 mag Jmag2 ? J magnitude, Marsh et al. 2010 (2)
101-106 F6.3 mag Hmag2 ? H magnitude, Marsh et al. 2010 (2)
110-115 F6.3 mag Kmag2 ? Ks magnitude, Marsh et al. 2010 (2)
117 A1 --- n_Kmag2 [bc] Saturation (3)
119-123 A5 --- G11 Identification in Geers et al.
2011ApJ...726...23G 2011ApJ...726...23G
125 A1 --- n_G11 [de] Individual notes (3)
127-131 F5.2 mag Jmag3 ? J magnitude, Geers et al. 2011ApJ...726...23G 2011ApJ...726...23G
133-137 F5.2 mag Kmag3 ? Ks magnitude, Geers et al. 2011ApJ...726...23G 2011ApJ...726...23G
138 A1 --- n_Kmag3 [s] if Kmag3 is saturated
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Note (1): Alves de Oliveira et al. 2010A&A...515A..75A 2010A&A...515A..75A
Note (2): Marsh et al. 2010, Cat. J/ApJ/719/550
Note (3): the remarks have the following meaning:
a = Source 21 of Table 4 of Alves de Oliveira et al. is a 4.5" binary
in our images - their coordinates fall between those of the two
components, whereas their photometry agrees with our photometry
for the fainter component. We list the coordinates and photometry
for the primary for completeness.
b = Saturated in our data.
c = This is the planetary mass object confirmed spectroscopically by
Marsh et al. (2010, Cat. J/ApJ/719/550). See the text for discussion.
d = Sources 8 and 24 as listed in Geers et al. (2011ApJ...726...23G 2011ApJ...726...23G)'s
Table 1 have identical entries for their coordinates and photometry,
with the exception of the Ks photometry, which is listed at 13.36
for Source 8 and as 12.29 for Source 24. We have used the value
listed for Source 24, as it agrees better with other determinations.
e = Source No. from Table 2 of Geers et al. with spectroscopic follow-up.
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Acknowledgements:
Mary Barsony, SETI Institute mbarsony (at) seti. org
(End) Greg Schwarz [AAS], Francois Ochsenbein [CDS] 12-Nov-2012