J/ApJ/684/654 Low-mass members of Chamaeleon I (Luhman+, 2008)
New low-mass stars and brown dwarfs with disks in the Chamaeleon I star-forming
region.
Luhman K.L., Muench A.A.
<Astrophys. J., 684, 654-662 (2008)>
=2008ApJ...684..654L 2008ApJ...684..654L
ADC_Keywords: Photometry, infrared ; YSOs ; Spectroscopy ; Equivalent widths
Keywords: accretion, accretion disks - planetary systems: protoplanetary disks -
stars: formation - stars: low-mass, brown dwarfs -
stars: pre-main sequence
Abstract:
We have used images obtained with the Infrared Array Camera and the
Multiband Imaging Photometer on board the Spitzer Space Telescope to
search for low-mass stars and brown dwarfs with circumstellar disks in
the Chamaeleon I star-forming region. Through optical spectroscopy of
sources with red colors in these data, we have identified seven new
disk-bearing members of the cluster. Three of these objects are
probably brown dwarfs, according to their spectral types (M8, M8.5,
M8-L0). Three of the other new members may have edge-on disks, based
on the shapes of their infrared spectral energy distributions. One of
the possible edge-on systems has a steeply rising slope from 4.5 to
24um, indicating that it could be a Class I source
(star+disk+envelope) rather than a Class II source (star+disk). If so,
then it would be one of the least massive known Class I protostars
(M5.75, M∼0.1M☉).
Description:
To search for new disk-bearing members of Chamaeleon I, we use images
at 3.6, 4.5, 5.8, and 8.0um obtained with Spitzer's Infrared Array
Camera (IRAC) and images at 24um obtained with the Multiband Imaging
Photometer for Spitzer (MIPS). The photometric catalog produced by
Luhman et al. (2008, Cat. J/ApJ/675/1375) is used for this study.
The remaining observations of Chamaeleon I that were not examined by
Luhman et al. were obtained through the Spitzer Legacy program of L.
Allen, which has a program identification of 30574. The IRAC and MIPS
images were collected on 2007 May 15-17 and 2007 April 5.
We obtained long-slit optical spectra of 10 candidate members of
Chamaeleon I using the Low Dispersion Survey Spectrograph (LDSS-3) on
the Magellan II Telescope on the nights of 2007 December 17 and 18.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
new.dat 145 8 New members of Chamaeleon I (table 1 and 2 of paper)
table3.dat 88 73 Spitzer photometry for known members of Chamaeleon I
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See also:
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
J/ApJ/675/1375 : IRAC/MIPS photometry in Cha I (Luhman+, 2008)
J/ApJS/173/104 : Stellar population in Chamaeleon I (Luhman, 2007)
J/A+A/416/555 : Brown Dwarfs in ChaI Dark Cloud (Lopez-Marti+ 2004)
J/ApJ/593/1093 : IC 348 membership (Luhman+, 2003)
J/AJ/121/974 : JHK photometry in Cha I (Gomez+, 2001)
J/AJ/121/2673 : 3µm survey of the Chamaeleon I dark cloud (Kenyon+, 2001)
J/ApJ/525/466 : Young low-mass stars and brown dwarfs in IC 348 (Luhman+,
1999)
Byte-by-byte Description of file: new.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- --- [2M /Cha]
5- 21 A17 --- 2M/Cha Name (JHHMMSSss+DDMMSSs)
23 A1 --- f_2M/Cha [f-i] Flag on Name (1)
25- 29 A5 --- SpT MK spectral type
31 I1 --- e_SpT ? Uncertainty on SpT (2)
33 A1 --- u_Teff [~] Uncertainty flag on Teff
34- 37 I4 K Teff Effective temperature (3)
39 A1 --- u_AJ [~] Uncertainty flag on AJ
40- 43 F4.2 --- AJ J-band extinction
45 A1 --- u_Lbol [~] Uncertainty flag on Lbol
46- 51 F6.4 solLum Lbol Bolometric luminosity
53 A1 --- f_Lbol [e] Luminosity uncertain (4)
55- 68 A14 --- Mm Membership evidence (5)
70- 74 F5.2 mag Jmag ? 2MASS J-band magnitude (6)
76- 79 F4.2 mag e_Jmag ? Jmag uncertainty (6)
81- 85 F5.2 mag Hmag ? 2MASS H-band magnitude (6)
87- 90 F4.2 mag e_Hmag ? Hmag uncertainty (6)
92- 96 F5.2 mag Ksmag ? 2MASS Ks-band magnitude (6)
98-101 F4.2 mag e_Ksmag ? Ksmag uncertainty (6)
103 A1 --- l_EW [≳ ] Limit flag on EW
104-108 F5.1 0.1nm EW Equivalent widths of the Hα emission line
110-113 F4.1 0.1nm e_EW ? Uncertainty on EW
115-119 F5.2 --- alpha1 ? α(2-8um) (7)
121-125 F5.2 --- alpha2 ? α(2-24um) (7)
127-131 F5.2 --- alpha3 α(3.6-8um) (7)
133-137 F5.2 --- alpha4 ? α(3.6-24um) (7)
139-145 A7 --- SEDCl SED class (8)
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Note (1): Flags as follows:
f = [LES2004] ChaI 424
g = At 2' from RX J1108.8-7519A and RX J1108.8-7519B
h = At 4" from T39A and T39B
i = OTS 32; 18" from Hn 11
Note (2): Uncertainties are ±0.25 subclass unless noted otherwise.
These uncertainties represent the precision within the optical
classification scheme adopted in this work (Luhman 1999, Cat.
J/ApJ/525/466, <Cl* IC 348 LRL NNN> in Simbad).
Note (3): Converted from the spectral types using the temperature scale
from Luhman et al. (2003, Cat. J/ApJ/593/1093, <Cl* IC 348 LRL NNNNNA>
in Simbad). In addition to the errors in the spectral type, these
temperature estimates are subject to a systematic uncertainty in the
temperature scale (Luhman et al. 2008, Cat. J/ApJ/675/1375), which is
probably at least ±100K.
Note (4): 'e' indicates the star may have an edge-on disk.
If so, this luminosity estimate is not reliable.
Note (5): Membership in Chamaeleon is indicated as follows:
AV = AV≳1 and a position above the main sequence for the distance of
Chamaeleon,
e = strong emission lines,
NaK = NaI and KI strengths intermediate between those of dwarfs and giants,
ex = IR excess emission.
Note (6): From the 2MASS-PSC (Cat. II/146) except for 2MASS J11095493-7635101
and 2MASS J11100336-7633111 which are taken from the ISPI images of
Luhman, 2007, Cat. J/ApJS/173/104 (<[L2007b] Cha JHHMMSSss+DDMMSSs>
in Simbad).
Note (7): Spectral slopes are defined as
α=dlog(λFλ)/dlog(λ).
See section 4.3 for further details.
Note (8): We classify each object as Class I, flat-spectrum, Class II, or
Class III by applying the thresholds from Luhman et al. (2008, Cat.
J/ApJ/675/1375) to the spectral slopes, which follows the standard
classification scheme for SEDs of young stars (Lada,
1987IAUS..115....1L 1987IAUS..115....1L; Greene et al., 1994ApJ...434..614G 1994ApJ...434..614G).
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 17 A17 --- 2MASS 2MASS designation (JHHMMSSss+DDMMSSs)
19- 34 A16 --- OName Name (1)
36- 40 F5.2 mag [3.6] ? Spitzer/IRAC 3.6um band magnitude
42- 45 F4.2 mag e_[3.6] ? 3.6um magnitude uncertainty
47- 51 F5.2 mag [4.5] ? Spitzer/IRAC 4.5um band magnitude
53- 56 F4.2 mag e_[4.5] ? 4.5um magnitude uncertainty
58- 62 F5.2 mag [5.8] ? Spitzer/IRAC 5.8um band magnitude
64- 67 F4.2 mag e_[5.8] ? 5.8um magnitude uncertainty
69- 73 F5.2 mag [8.0] ? Spitzer/IRAC 8.0um band magnitude
75- 78 F4.2 mag e_[8.0] ? 8.0um magnitude uncertainty
80- 83 F4.2 mag [24] ? Spitzer/MIPS 24um band magnitude
85- 88 F4.2 mag e_[24] ? 24um magnitude uncertainty
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Note (1): (LES2004) refers to Lopez Marti et al., 2004, Cat. J/A+A/416/555;
<[LES2004] ChaI NNN> in Simbad.
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History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 09-Dec-2010