X-Ray Sources and Star Formation Activity in the Sagittarius B2 Cloud Observed with Chandra
Abstract
We report the X-ray population study in the giant molecular cloud Sagittarius B2 (Sgr B2). More than a dozen X-ray cloud members (and candidates) are discovered with Chandra. Two bright X-ray sources are located near Sgr B2 Main, the most copious complex of the ultracompact H II sources. The X-ray spectra are fitted with a thin thermal plasma model of 5-10 keV temperature. The intrinsic luminosity, after correcting the absorption of ~5×1023Hcm-2, is ~1033 ergs s-1. Although these two X-ray sources are attributable to young stellar objects (YSOs) in the same H II complex, they are in sharp contrast; the one at the center of the H II complex exhibits strong K-shell transition lines of iron, while the other near the east has only weak lines. The other H II complexes, Sgr B2 North and South, also show hard and highly absorbed X-ray emissions due possibly to the star formation activity. The composite X-ray spectrum of the other cloud member X-ray sources is fitted with a thin thermal plasma of ~10 keV temperature with hydrogen column density (NH) of 1.3×1023Hcm-2 and individual X-ray luminosity of a few times 1031-1032 ergs s-1. These are likely to be a single YSO or cluster of YSOs, but neither radio nor infrared counterpart is found. An alternative scenario of isolated white dwarfs powered by Bondi-Hoyle accretion from the dense cloud gas is also discussed. The X-ray spectra exhibit an additional 6.4 keV line of neutral or low-ionization irons, which indicates that the environment gas is concentrated near the sources.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 2002
- DOI:
- 10.1086/340499
- arXiv:
- arXiv:astro-ph/0203035
- Bibcode:
- 2002ApJ...573..275T
- Keywords:
-
- Galaxy: Center;
- ISM: Clouds;
- ISM: Individual: Name: Sagittarius B2;
- Stars: Formation;
- X-Rays: Individual: Constellation Name: Sagittarius B2;
- X-Rays: Stars;
- Astrophysics
- E-Print:
- 14 pages with 6 figures. Accepted in ApJ