A warm molecular hydrogen tail due to ram-pressure stripping of a cluster galaxy

Suresh Sivanandam, Marcia J. Rieke, George H. Rieke

Research output: Contribution to journalArticlepeer-review

54 Scopus citations


We have discovered a remarkable warm (130-160 K) molecular hydrogen tail with a H2 mass of approximately 4 × 107 M ® 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 ® 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.

Original languageEnglish (US)
Pages (from-to)147-162
Number of pages16
JournalAstrophysical Journal
Issue number1
StatePublished - 2010


  • Galaxies: ISM
  • Galaxies: clusters: individual (Abell 3627)
  • Galaxies: evolution
  • Galaxies: individual (ESO 137-001)
  • Infrared: galaxies

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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