SETI bioastro: 17 new very low-mass members in Taurus. The brown dwarf deficit revisited

• Previous message: LARRY KLAES: "SETI bioastro: FW: [nh-announce] 14 September 2005 -- Natural Hazards Updates"

astro-ph/0509317 [abs, ps, pdf, other] :

Title: 17 new very low-mass members in Taurus. The brown dwarf deficit
revisited

Authors: S. Guieu (1), C Dougados (1), J.L Monin (1 and 2), E Magnier (3 and
4), E.L Martin (5 and 6) ((1) Laboratoire d'Astrophysique de Grenoble, (2)
Institut Universitaire de France, (3) Canada-France-Hawaii Telescope
Corporation, (4) University of Hawaii, Institute of Astronomy, (5) Instituto
de Astrofisica de Canarias, (5) University of Central Florida, Department of
Physics)

Comments: 20 pages, 15 figures

Recent studies of the substellar population in the Taurus cloud have
revealed a deficit of brown dwarfs (BD) compared to the Trapezium cluster
population (Briceno et al 1998; Luhman 2000; Luhman et al 2003a; Luhman
2004). However, these works have concentrated on the highest stellar density
regions of the Taurus cloud. We have performed a large scale optical survey
of this region, covering a total area of 30 deg^2, and encompassing the
densest part of the cloud as well as their surroundings, down to a mass
detection limits of 15 Jupiter Masses (MJ). In this paper, we present the
optical spectroscopic follow-up observations of 97 photometrically selected
potential new low-mass Taurus members, of which 27 are strong late-M (SpT <
M4V) candidates. These observations reveal 5 new very low mass (VLM) Taurus
members and 12 new BDs. Combining our observations with previously published
results, we derive an updated substellar to stellar ratio in Taurus of Rss
=0.23 +/- 0.05. This ratio now appears consistent with the value previously
derived in the Trapezium cluster under similar assumptions of 0.26 +/- 0.04.
We find strong indication that the relative numbers of BDs with respect to
stars is decreased by a factor 2 in the central regions of the aggregates
with respect to the more distributed population. Our findings are best
explained in the context of the embryo-ejection model where brown dwarfs
originate from dynamical interactions in small N unstable multiple systems.

http://arxiv.org/abs/astro-ph/0509317

• Previous message: LARRY KLAES: "SETI bioastro: FW: [nh-announce] 14 September 2005 -- Natural Hazards Updates"

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