Astronomy and Astrophysics, volume 556A, 99-99 (2013/8-1)
Search for cold and hot gas in the ram pressure stripped Virgo dwarf galaxy IC 3418.
JACHYM P., KENNEY J.D.P., RUZICKA A., SUN M., COMBES F. and PALOUS J.
Abstract (from CDS):
We present IRAM 30 m sensitive upper limits on CO emission in the ram pressure stripped dwarf Virgo galaxy IC3418 and in a few positions covering HII regions in its prominent 17kpc UV/Hα gas-stripped tail. In the central few arcseconds of the galaxy, we report a possible marginal detection of about 1x106M☉ of molecular gas (assuming a Galactic CO-to-H2 conversion factor) that could correspond to a surviving nuclear gas reservoir. We estimate that there is less molecular gas in the main body of IC3418, by at least a factor of 20, than would be expected from the pre-quenching UV-based star formation rate assuming the typical gas depletion timescale of 2Gyr. Given the lack of star formation in the main body, we think the H2-deficiency is real, although some of it may also arise from a higher CO-to-H2 factor typical in low-metallicity, low-mass galaxies. The presence of HII regions in the tail of IC3418 suggests that there must be some dense gas; however, only upper limits of <1x106M☉ were found in the three observed points in the outer tail. This yields an upper limit on the molecular gas content of the whole tail <1x107M☉, which is an amount similar to the estimates from the observed star formation rate over the tail. We also present strong upper limits on the X-ray emission of the stripped gas in IC3418 from a new Chandra observation. The measured X-ray luminosity of the IC3418 tail is about 280 times lower than that of ESO 137-001, a spiral galaxy in a more distant cluster with a prominent ram pressure stripped tail. Non-detection of any diffuse X-ray emission in the IC3418 tail may be due to a low gas content in the tail associated with its advanced evolutionary state and/or due to a rather low thermal pressure of the surrounding intra-cluster medium.