Seventeen new very low-mass members in Taurus

S. Guieu, C. Dougados, J.-L. Monin, E. Magnier, E. L. Martín
2006 Astronomy and Astrophysics  
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,
more » ... ir 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.
doi:10.1051/0004-6361:20053493 fatcat:j5nnq55drvbn7cgnq3sr3zjlqe