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
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:
FileName Lrecl Records Explanations
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
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
Bytes Format Units Label Explanations
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 alpha(3.6-8um) (7) 133-137 F5.2 --- alpha4 ? α(3.6-24um) (7) 139-145 A7 --- SEDCl SED class (8)
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; Greene et al., 1994ApJ...434..614G).
Byte-by-byte Description of file: table3.dat
Bytes Format Units Label Explanations
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  ? Spitzer/MIPS 24um band magnitude 85- 88 F4.2 mag e_ ? 24um magnitude uncertainty
Note (1): (LES2004) refers to Lopez Marti et al., 2004, Cat. J/A+A/416/555; <[LES2004] ChaI NNN> in Simbad.
History: From electronic version of the journal
(End) Emmanuelle Perret [CDS] 09-Dec-2010
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