Abstract:
Using the excellent astrometry capabilities of the Very Long Baseline Array, we have measured the trigonometric parallax (and the proper motions) of a number of young stars in several nearby star-forming regions with an accuracy better than a few percents. This represents an improvement by one or two orders of magnitude over previous determinations. In particular, we have found that the distance to the core of Ophiuchus is 120 +/- 4.5 pc, and we have confirmed that the mean distance to Taurus is 140 pc. The distance to the Serpens core appears to be 415 pc, 30 to 50 % larger than the value usually assumed. Our data also allows us to obtain a rough determination of the 3D structure of the regions under study. In the case of Taurus, we have shown that the total extent of the complex along the line of sight is about 30 pc, the eastern portion being on the far side and the region around L1495 on the near side. In this talk, after presenting the results themselves, I will describe several new constraints for the formation and early evolution of stars that these data provide, focusing in particular on pre-main sequence evolutionary models. I will end my talk by mentioning long-term prospects.
Coffee and tea will be served 20 minutes prior to the seminar.