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 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 1996MNRAS.280.1071L);
Baud = Baud et al. (1984ApJ...278L..53B 1984ApJ...278L..53B), BYB in Simbad
C = Prusti et al. (1991MNRAS.251..303P 1991MNRAS.251..303P); [PCW91] Ced 110 IRS in Simbad
CHX = Feigelson & Kriss (1989ApJ...338..262F 1989ApJ...338..262F);
CHXR = Feigelson et al. (1993ApJ...416..623F 1993ApJ...416..623F);
GK = Gomez & Kenyon (2001AJ....121..974G 2001AJ....121..974G); [GK2001] in Simbad
KG = Kenyon & Gomez (2001AJ....121.2673K 2001AJ....121.2673K); [KG2001] in Simbad
Hn = Hartigan (1992AAS...181.8705H 1992AAS...181.8705H);
ISO = Persi et al. (2000A&A...357..219P 2000A&A...357..219P), P. Persi, priv. communication;
NIR = Oasa et al. (1999ApJ...526..336O 1999ApJ...526..336O); [OTS99] in Simbad
Sz = Schwartz (1977ApJS...35..161S 1977ApJS...35..161S);
T = Schwartz (in 1991ESOSR..11....1R 1991ESOSR..11....1R, p.93);
DENIS = Cambresy et al. 1998A&A...338..977C 1998A&A...338..977C Table 1; [CCE98] 1-# in Simbad
DENIS-P = Cambresy et al. 1998A&A...338..977C 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 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