仙女座B2星系正式胶束射线：极大基线阵列与大型阵列天文观测
摘要
presented of observations of two of the formaldehyde (H2CO) masers (A and D) in Sgr B2 using the VLBA+Y27 (resolution ~0.01") and the VLA (resolution ~9"). The VLBA observations show compact sources (<10 milliarcseconds, <80 AU) with brightness temperatures >10^8 K. The maser sources are partially resolved in the VLBA observations. The flux densities in the VLBA observations are about 1/2 those of the VLA; and, the linewidths are about 2/3 of the VLA values. The applicability of a core-halo model for the emission distribution is demonstrated. Comparison with earlier H2CO absorption observations and with ammonia (NH3) observations suggests that H2CO masers form in shocked gas. Comparison of the integrated flux densities in current VLA observations with those in previous observations indicates that (1) most of the masers have varied in the past 20 years, and (2) intensity variations are typically less than a factor of two compared to the 20-year mean. No significant linear or circular polarization is detected with either instrument.
引用
@article{arxiv.astro-ph/0609800,
title = {The Formaldehyde Masers in Sgr B2: Very Long Baseline Array and Very Large Array Observations},
author = {Ian M. Hoffman and W. M. Goss and Patrick Palmer},
journal= {arXiv preprint arXiv:astro-ph/0609800},
year = {2008}
}
备注
20 pages, 3 figures, 5 tables, accepted to ApJ