A GALEX based search for the sparse young stellar population in the Taurus-Aurigae star forming region

Abstract

In this work, we identify 63 bona fide new candidates to T Tauri stars (TTSs) in the Taurus-Auriga region using as baseline its ultraviolet excess. The initial data set has been defined from the GALEX all sky survey (AIS). The GALEX satellite obtained images in the near ultraviolet (NUV) and far ultraviolet (FUV) bands where the TTSs show a prominent excess, compared with main sequence or giants stars. GALEX AIS surveyed the Taurus-Auriga molecular complex, as well as, a fraction of the California Nebula and the Perseus complex; bright sources and the dark clouds themselves are avoided. The properties of the TTSs in the ultraviolet (GALEX), optical (UCAC4) and infrared (2MASS) have been defined using as qualification sample the TTSs observed with the International Ultraviolet Explorer. The candidates have been identified by means of a mixed ultraviolet-optical-infrared excess set of colors; it is found that the color-color diagram FUV-NUV versus J-K is ideally suited for this purpose. From an initial sample of 163,313 bona-fide NUV sources, a final list with 63 new candidates to TTSs in the region has been produced. The search procedure has been validated by its ability to detect all known TTSs in the area surveyed: 31 TTSs. Also, it is shown that the weak-lined TTSs are located in a well defined stripe in the FUV-NUV versus J-K diagram. Moreover, we provide in this work a list of TTSs photometric standards for future GALEX-based studies of the young stellar population in star forming regions.