Abstract
In order to understand more details about the early stage of star formation, it is necessarily to study the very Young Stellar Objects (YSOs). Very Low Luminosity Objects (VeLLOs), whose intrinsic luminosities are below 0.1 Lsun, are thought as the youngest, very low mass YSOs, or proto-brown dwarfs. Taurus is one of the closest molecular clouds, and hence identifying VeLLOs in the Taurus molecular cloud can provide us a list of source for follow-up high resolution studies. In order to find VeLLOs in Taurus, we applied the selection criteria from Dunham et al. (2008) who identify 15 VeLLO candidates in the c2d surveyed nearby molecular clouds and cores. We further included bolometric temperature and extinction value as additional criteria to make up the lack of submm/mm data for our VeLLO candidates. As a result, 11 VeLLO candidates were selected from roughly 270,000 sources in Taurus Spitzer catalogue. Furthermore, we observed 13CO (J=2-1), C18O (J=1-0), N2D+ (J=3-2), and N2H+ (J=1-0) with Arizona Radio Observatory (ARO) to confirm our VeLLO candidates. The observation results show 4 sources have N2H+ detection, but all candidates have no N2D+ detection. There are 10 sources with either 13CO (J=2-1) or C18O (J=1-0) detections. We found one source without any molecular line detection has been previously confirmed as a galaxy from X-ray detection. We compared the SED between VeLLO candidates and Class 0/I sources, and concluded that the 160μm data is crucial for distinguishing the difference between YSOs and galaxy contaminations. Therefore, we propose to include an additional criterion for VeLLO selection: “rising (or flat) of SED between 70 and 160μm, unless confused or not observed at 160μm”. With this new criterion, two possible galaxies will be excluded from our sample. The remaining eight candidates have higher probability to be true VeLLOs because of their molecular line detections. Since our results show no N2D+ detection from all candidates, these eight candidates are more likely to be very low-mass protostars than very young YSOs. Finally, according to the N2H+ results and the SED shapes, we classified our 11 infrared selected VeLLO candidates into four types: two in late Class 0 stage, two in early Class I stage, four in Class I stage, and three galaxy contaminations.