BANYAN. VII. A new population of young substellar candidate members of nearby moving groups from the Bass survey
- Institut de Recherche sur les Exoplanètes (iREx), Université de Montréal, Département de Physique, C.P. 6128 Succ. Centre-ville, Montréal, QC H3C 3J7 (Canada)
- Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, DC 20015 (United States)
- Department of Astrophysics, American Museum of Natural History, Central Park West at 79th Street, NY 10024 (United States)
- Center for Astrophysics and Space Sciences, University of California, San Diego, 9500 Gilman Dr., Mail Code 0424, La Jolla, CA 92093 (United States)
We present the results of a near-infrared (NIR) spectroscopic follow-up survey of 182 M4–L7 low-mass stars and brown dwarfs (BDs) from the BANYAN All-Sky Survey (BASS) for candidate members of nearby, young moving groups (YMGs). We confirm signs of low gravity for 42 new BD discoveries with estimated masses between 8 and 75 M{sub Jup} and identify previously unrecognized signs of low gravity for 24 known BDs. We refine the fraction of low-gravity dwarfs in the high-probability BASS sample to ∼82%. We use this unique sample of 66 young BDs, supplemented with 22 young BDs from the literature, to construct new empirical NIR absolute magnitude and color sequences for low-gravity BDs. We show that low-resolution NIR spectroscopy alone cannot differentiate between the ages of YMGs younger than ∼120 Myr, and that the BT-Settl atmosphere models do not reproduce well the dust clouds in field or low-gravity L-type dwarfs. We obtain a spectroscopic confirmation of low gravity for 2MASS J14252798–3650229, which is a new ∼27 M{sub Jup}, L4 γ bona fide member of AB Doradus. We identify a total of 19 new low-gravity candidate members of YMGs with estimated masses below 13 M{sub Jup}, 7 of which have kinematically estimated distances within 40 pc. These objects will be valuable benchmarks for a detailed atmospheric characterization of planetary-mass objects with the next generation of instruments. We find 16 strong candidate members of the Tucana–Horologium association with estimated masses between 12.5 and 14 M{sub Jup}, a regime where our study was particularly sensitive. This would indicate that for this association there is at least one isolated object in this mass range for every 17.5{sub −5.0}{sup +6.6} main-sequence stellar member, a number significantly higher than expected based on standard log-normal initial mass function, however, in the absence of radial velocity and parallax measurements for all of them, it is likely that this over-density is caused by a number of young interlopers from other associations.
- OSTI ID:
- 22872427
- Journal Information:
- Astrophysical Journal, Supplement Series, Vol. 219, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0067-0049
- Country of Publication:
- United States
- Language:
- English
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