用VO工具进行的基于IPHAS的吸积极低质量天体的搜索
An IPHAS-based search for accreting very low-mass objects using VO tools
摘要：
本文的主要目的是证明吸积的极低质量恒星和褐矮星可以在银河系北部的一个Halalpha辐射巡天IPHAS中被识别出来，充分利用IPHAS数据库以及将来在南半球的扩展将有助于识别在著名恒星形成区附近和远处的极低质量吸积天体。我们已经使用虚拟天文台的工具，交叉匹配的IPHAS目录与2 MASS目录。我们定义了光度标准，以确定Halpha发射源的近红外颜色类似于已知的年轻的非常低质量的恒星和褐矮星。在1600平方度的区域内确定了4000个符合我们标准的候选人。我们提出了113个候选人的低分辨率光谱。光谱类型已被推导出的33个候选人，光谱确认的Halpha发射，可忽略不计的红化和M光谱类。我们还测量了这33个天体的H α发射，并研究了NaI的双峰（818.3 nm，819.5 nm）。我们确认，33 IPHAS候选人有很强的H α指示磁盘吸积的光谱类型。其中23颗的光谱类别为M4或更高，其中10颗的光谱类别在M5.5-M7.0之间，因此可能是非常年轻的棕矮星。此外，许多对象有弱的NaI双峰，低的表面gravity.We的指示，IPHAS提供了一个非常有价值的数据库，以确定吸积非常低质量的恒星和褐矮星，虚拟天文台工具提供了一个有效的方法来识别这些对象在大面积的天空。根据我们在113个候选天体中成功发现光谱类型在M4-M7范围内的23个阿尔法发射天体的成功率，我们估计在IPHAS的全部调查中可能有数百个这样的天体。
英文摘要：
The main goal of this paper is to prove that accreting very low-mass stars and brown dwarfs can be identified in IPHAS, a Halpha emission survey of the northern Milky Way.Full exploitation of the IPHAS database and a future extension of it in the southern hemisphere will be useful to identify very low-mass accreting objects near and far well-known star forming regions. We have used Virtual Observatory tools to cross-match the IPHAS catalogue with the 2MASS catalogue. We defined photometric criteria to identify Halpha emission sources with near-infrared colours similar to known young very low-mass stars and brown dwarfs. 4000 candidates were identified that met our criteria over an area of 1600 square degrees. We present low-resolution optical spectra of 113 candidates. Spectral types have been derived for the 33 candidates that have spectroscopically confirmed Halpha emission, negligible reddening and M spectral class. We have also measured Halpha emission and investigated the NaI doublet (818.3 nm, 819.5 nm) in these 33 objects. We confirm that 33 IPHAS candidates have strong Halpha indicative of disk accretion for their spectral type. 23 of them have spectral class M4 or later, of which 10 have classes in the range M5.5-M7.0 and thus could be very young brown dwarfs. Also many objects have weak NaI doublet, an indication of low surface gravity.We conclude that IPHAS provides a very valuable database to identify accreting very low-mass stars and brown dwarfs, and that Virtual Observatory tools provide an efficient method for identifying these objects over large areas of the sky. Based on our success rate of 23 Halpha emission objects with spectral type in the range M4-M7 out of 113 candidates with spectroscopic follow-up, we estimate that there could be hundreds of such objects in the full IPHAS survey.
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