Searching for T dwarfs in the ρ Oph dark cloud L 1688

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題名:	Searching for T dwarfs in the ρ Oph dark cloud L 1688
作者:	陳文屏;Chiang, Poshih;Chen, Wen-Ping;Albert, Loïc;Liu, Michael;Magnier, Eugene A.
貢獻者:	理學院天文研究所
關鍵詞:	Atmospheres;Clouds;Color;Colour;Criteria;Lists;Methane;Searching;Star formation
日期:	2015-01-01
上傳時間:	2026-04-21 14:30:53 (UTC+8)
出版者:	Oxford University Press
摘要:	摘要： We present a list of T dwarf candidates in the dark cloud L 1688 in the ρ Oph star-forming region. These candidates are selected with infrared colours sensitive to T dwarf characteristics of methane absorptions and of cool atmospheres. The 1.6-μm methane feature is diagnosed by on–off imaging using an H-band and an intermediate-band methane filter, calibrated to a set of known brown dwarfs of M, L, and T types in the field. Another methane feature at 3.3 μm is traced with the Spitzer/Infrared Array Camera (IRAC) [3.6] − [4.5] colour. For cool atmospheres, the H − [4.5] and K − [4.5] colours are utilized. With an additional criterion of mid-infrared brightness to eliminate extragalactic interlopers, a total of 28 T dwarf candidates have been identified. A comprehensive assessment was conducted to estimate the level of contamination of our sample by young stellar variability, by extragalactic sources sharing the same colour behaviour, or by foreground T dwarfs. Though extragalactic sources may contribute up to about half of the false positives, our candidates show close spatial association with the dark cloud, rather than randomly distributed as a background population would have been. Furthermore, even though our candidates are not selected a priori by a colour–magnitude relation, they mostly follow the 1 Myr isochrones, ascertaining their youth. Our selection methodology provides guidance to search for T dwarfs in other star-forming regions. Our candidate list, when comparing with those in the literature, which often rely on a single criterion on cool temperature or methane, is more conservative but should be more secure for follow-up spectroscopic confirmation of a T dwarf sample at the early evolutionary stage. 其他題名： Mon. Not. R. Astron. Soc 出版者： Oxford University Press 出版日期： 2015-03-21 出處： Monthly notices of the Royal Astronomical Society, 2015-03, Vol.448 (1), p.522-540 資源來源： Alma/SFX Local Collection 版權： 2015 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society 2015 識別號： ISSN: 0035-8711 識別號： ISSN: 1365-8711 識別號： ISSN: 1365-2966 識別號： EISSN: 1365-2966 識別號： DOI: 10.1093/mnras/stu2701
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