Substellar objects in nearby young clusters (SONYC). VIII. Substellar population in Lupus 3
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SONYC - Substellar Objects in Nearby Young Clusters - is a survey program to investigate the frequency and properties of substellar objects in nearby star-forming regions. We present a new imaging and spectroscopic survey conducted in the young (∼1 Myr), nearby (∼200 pc) star-forming region Lupus 3. Deep optical and near-infrared images were obtained with MOSAIC-II and NEWFIRM at the CTIO 4 m telescope, covering ∼1.4 deg2 on the sky. The i-band completeness limit of 20.3 mag is equivalent to 0.009-0.02 M☉, for AV ≤ 5. Photometry and 11-12 yr baseline proper motions were used to select candidate low-mass members of Lupus 3. We performed a spectroscopic follow-up of 123 candidates, using VIMOS at the Very Large Telescope, and we identify 7 probable members, among which 4 have spectral type later than M6.0 and Teff ≤ 3000 K, i.e., are probably substellar in nature. Two of the new probable members of Lupus 3 appear underluminous for their spectral class and exhibit emission line spectrum with strong Hα or forbidden lines associated with active accretion. We derive a relation between the spectral type and effective temperature: Teff = (4120 ± 175)-(172 ± 26) × SpT, where SpT refers to the M spectral subtype between 1 and 9. Combining our results with the previous works on Lupus 3, we show that the spectral type distribution is consistent with that in other star-forming regions, as well as the derived star-to-brown dwarf ratio of 2.0-3.3. We compile a census of all spectroscopically confirmed low-mass members with spectral type M0 or later.
Mužić , K , Scholz , A , Geers , V C , Jayawardhana , R & Martí , B L 2014 , ' Substellar objects in nearby young clusters (SONYC). VIII. Substellar population in Lupus 3 ' Astrophysical Journal , vol 785 , no. 2 , 159 . DOI: 10.1088/0004-637X/785/2/159
© 2014. The American Astronomical Society. All rights reserved.
DescriptionThis work was co-funded under the Marie Curie Actions of the European Commission (FP7KCOFUND). A.S. acknowledges financial support through the grant 10/RFP/AST2780 from the Science Foundation Ireland. B.L.M. was supported by the Spanish Plan Nacional de Astronomía y Astrofísica through project AYA 2011-30147-C03-03. Support for this work also came from grants to R.J. from the Natural Sciences and Engineering Research Council of Canada.
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