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J/A+A/416/555       Brown Dwarfs in ChaI Dark Cloud    (Lopez-Marti+ 2004)

The brown dwarf population in the Chamaeleon I cloud. Lopez-Marti B., Eisloeffel J., Scholz A., Mundt R. <Astron. Astrophys., 416, 555-576 (2004)> =2004A&A...416..555L
ADC_Keywords: Molecular clouds ; Stars, pre-main sequence ; Photometry, infrared Keywords: stars: low-mass, brown dwarfs ; stars: pre-main sequence ; stars: formation ; stars: luminosity function, mass function ; stars: circumstellar matter Abstract: We present the results of a multiband survey for brown dwarfs in the Chamaeleon I dark cloud with the Wide Field Imager (WFI) camera at the ESO/MPG 2.2-m telescope on La Silla (Chile) on 28-May to 03-Jun 1999. The survey has revealed a substantial population of brown dwarfs in this southern star-forming region. Candidates were selected from R, I and Hα imaging observations. We also observed in two medium-band filters, M855 and M915, for spectral type determination. The former filter covers a wavelength range containing spectral features characteristic of M-dwarfs, while the latter lies in a relatively featureless wavelength region for these late-type objects. A correlation was found between spectral type and (M855-M915) colour index for mid- to late M-type objects and early L-type dwarfs. With this method, we identify most of our object candidates as being of spectral type M5 or later. Our results show that there is no strong drop in the number of objects for the latest spectral types, hence brown dwarfs may be as abundant as low-mass stars in this region. Also, both kind of objects have a similar spatial distribution. We derive an index α=0.6±0.1 of the mass function in this region of dispersed star formation, in good agreement with the values obtained in other star forming regions and young clusters. Some of the brown dwarfs have strong Hα emission, suggesting mass accretion. For objects with published infrared photometry, we find that strong Hα emission is related to a mid-infrared excess, indicative of the existence of a circumstellar disk. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table4.dat 144 72 Candidate low-mass members of ChaI table6.dat 78 47 Infrared photometry for candidate low-mass members
See also: J/A+A/357/219 : ISOCAM observations in Cha I. (Persi+, 2000) J/AJ/121/974 : JHK photometry in Cha I (Gomez+, 2001) J/AJ/124/1001 : JHKs photometry of Cha I variables (Carpenter, 2002) Byte-by-byte Description of file: table4.dat
Bytes Format Units Label Explanations
2- 5 A4 --- --- [ChaI] 7- 9 I3 --- ChaI [400,760] Source number 10 A1 --- n_ChaI [efg] Individual notes (G1) 12- 13 I2 h RAh Right Ascension J2000 (hours) 15- 16 I2 min RAm Right Ascension J2000 (minutes) 18- 21 F4.1 s RAs Right Ascension J2000 (seconds) 24 A1 --- DE- Declination J2000 (sign) 25- 26 I2 deg DEd Declination J2000 (degrees) 28- 29 I2 arcmin DEm Declination J2000 (minutes) 31- 34 F4.1 arcsec DEs Declination J2000 (seconds) 37- 41 F5.2 mag Rmag Red magnitude (reduced with Landolt standards) 42 A1 --- u_Rmag [;:] Uncertainty flag on Rmag (1) 44- 48 F5.2 mag Imag I magnitude 49 A1 --- u_Imag [;:] Uncertainty flag on Imag 51- 55 F5.2 mag Halpha H-alpha magnitude 56 A1 --- u_Halpha [;:] Uncertainty flag on Halpha 58- 62 F5.2 mag M855 Magnitude in medium-band filter 855/20nm 63 A1 --- u_M855 [;:] Uncertainty flag on M855 65- 69 F5.2 mag M915 Magnitude in medium-band filter 915/28nm 70 A1 --- u_M915 [;:] Uncertainty flag on M915 72- 84 A13 --- SpType Spectral class (2) 87- 97 A11 --- Class Object classification 100-144 A45 --- OtherNames Other names, as a comma-separated list (3)
Note (1): the estimated photometric errors are 0.05, and increase to 0.1 mag with a semi-colon (;) 0.2 mag with a colon (:) Note (2): estimated errors of spectral types are 1 subclass in the range M6-M9 and 2 subclasses in the range M4-M6. Spectral types from the literature are indicated in parenthesis. Note (3): Some dubious cross-identifications are indicated in parenthesis (see the "History" section below). The acronyms are: B = Lawson et al. (1996MNRAS.280.1071L); Baud = Baud et al. (1984ApJ...278L..53B), BYB in Simbad C = Prusti et al. (1991MNRAS.251..303P); [PCW91] Ced 110 IRS in Simbad CHX = Feigelson & Kriss (1989ApJ...338..262F); CHXR = Feigelson et al. (1993ApJ...416..623F); GK = Gomez & Kenyon (2001AJ....121..974G); [GK2001] in Simbad KG = Kenyon & Gomez (2001AJ....121.2673K); [KG2001] in Simbad Hn = Hartigan (1992AAS...181.8705H); ISO = Persi et al. (2000A&A...357..219P), P. Persi, priv. communication; NIR = Oasa et al. (1999ApJ...526..336O); [OTS99] in Simbad Sz = Schwartz (1977ApJS...35..161S); T = Schwartz (in 1991ESOSR..11....1R, p.93); DENIS = Cambresy et al. 1998A&A...338..977C Table 1; [CCE98] 1-# in Simbad DENIS-P = Cambresy et al. 1998A&A...338..977C Table 2.
Byte-by-byte Description of file: table6.dat
Bytes Format Units Label Explanations
2- 5 A4 --- --- [ChaI] 7- 9 I3 --- ChaI [400,760] Source number 10 A1 --- n_ChaI [b] Individual notes (G1) 14- 18 F5.2 mag JDmag ? DENIS J magnitude 21- 25 F5.2 mag KDmag ? DENIS K magnitude 28- 32 F5.2 mag Jmag ? J magnitude 35- 39 F5.2 mag Hmag ? H magnitude 42- 46 F5.2 mag Kmag ? K magnitude 49- 53 F5.2 mag Lmag ? L magnitude (3.5um) 57- 61 F5.1 mJy F6.7um ? ISOCAM infrared flux at F6.7um 64- 66 F3.1 mJy e_F6.7um ? Mean error on F6.7um 69- 73 F5.1 mJy F14.3um ? ISOCAM infrared flux at 14.3um 75- 78 F4.1 mJy e_F14.3um ? Mean error on F14.3um
Global Notes: Note (G1): a : Halpha, M855 and M915 magnitudes are instrumental magnitudes b : Photometry from Gomez & Kenyon (2001AJ....121..974G) e : no H{alpha{ emission; ambiguous counterpart f : ambiguous counterpart g : The (R-I) colour of this object is slightly too blue according to our selection criteria.
History: From electronic version of the journal * 23-Sep-2004: a few identifications which are most likely in error have been surrounded by parenthesis; it concerns the stars 721 and 735.
(End) Francois Ochsenbein [CDS] 07-Aug-2004
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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