Issue |
A&A
Volume 416, Number 2, March III 2004
|
|
---|---|---|
Page(s) | 555 - 576 | |
Section | Galactic structure, stellar clusters, and populations | |
DOI | https://doi.org/10.1051/0004-6361:20031720 | |
Published online | 27 February 2004 |
The brown dwarf population in the Chamaeleon I cloud *
1
Observatori Astronòmic de la Universitat de València, Edifici d'Instituts d'Investigació, Polígon La Coma, 46980 Paterna, Spain
2
Thüringer Landessternwarte, Sternwarte 5, 07778 Tautenburg, Germany e-mail: jochen@tls-tautenburg.de; scholz@tls-tautenburg.de
3
Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany e-mail: mundt@mpia-hd.mpg.de
Corresponding author: B. López Martí, belen.lopez-marti@uv.es
Received:
16
April
2003
Accepted:
19
November
2003
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). 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, M 855
and M 915, 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 (M 855–M 915) 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 M 5 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 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.
Key words: stars: low-mass, brown dwarfs / stars: pre-main sequence / stars: formation / stars: luminosity function, mass function / stars: circumstellar matter
© ESO, 2004
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