A Warm Molecular Hydrogen Tail due to Ram-pressure Stripping of a Cluster Galaxy
Abstract
We have discovered a remarkable warm (130-160 K) molecular hydrogen tail with a H2 mass of approximately 4 × 107 M sun extending 20 kpc from a cluster spiral galaxy, ESO 137-001, in Abell 3627. At least half of this gas is lost permanently to the intracluster medium, as the tail extends beyond the tidal radius of the galaxy. We also detect a hot (400-550 K) component in the tail that is approximately 1% of the mass. The large H2 line to IR continuum luminosity ratio in the tail indicates that star formation is not a major excitation source and that the gas is possibly shock-heated. This discovery confirms that the galaxy is currently undergoing ram-pressure stripping, as also indicated by its previously discovered X-ray and Hα tails. We estimate that the galaxy is losing its warm H2 gas at a rate of ~2-3 M sun yr-1. The true mass-loss rate is likely higher if we account for cold molecular gas and atomic gas. We predict that the galaxy will lose most of its gas in a single pass through the core and place a strong upper limit on the ram-pressure timescale of 1 Gyr. We also study the star-forming properties of the galaxy and its tail. We identify most of the previously discovered external Hα sources within the tail in our 8 μm data but not in our 3.6 μm data; IRS spectroscopy of the region containing these Hα sources also reveals aromatic features typically associated with star formation. From the positions of these H II regions, it appears that star formation is not occurring throughout the molecular hydrogen tail but only immediately downstream of the galaxy. Some of these H II regions lie outside the tidal radius of the galaxy, indicating that ram-pressure stripping can be a source of intracluster stars.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 2010
- DOI:
- 10.1088/0004-637X/717/1/147
- arXiv:
- arXiv:0912.0075
- Bibcode:
- 2010ApJ...717..147S
- Keywords:
-
- galaxies: clusters: individual: Abell 3627;
- galaxies: evolution;
- galaxies: individual: ESO 137-001;
- galaxies: ISM;
- infrared: galaxies;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- Accepted by ApJ, 22 pages, 10 figures, 5 tables