Volume 582, October 2015
|Number of page(s)||8|
|Published online||25 September 2015|
Ram pressure stripping in the Virgo Cluster
1 Observatoire de Paris, LERMA, CNRS UMR 8112, 61 Av. de l’Observatoire, 75014 Paris, France
2 Collège de France, 11 place Marcelin Berthelot, 75005 Paris, France
3 Department of Astrophysics, Astronomy & Mechanics, Faculty of Physics, University of Athens, 15784 Panepistimiopolis Zografos, Greece
4 Univ. Bordeaux, Laboratoire d’Astrophysique de Bordeaux, CNRS UMR 5804, 33270 Floirac, France
Received: 18 May 2015
Accepted: 9 July 2015
Gas can be violently stripped from their galaxy disks in rich clusters, and be dispersed over 100 kpc-scale tails or plumes. Young stars have been observed in these tails, suggesting they are formed in situ. This will contribute to the intracluster light, in addition to tidal stripping of old stars. We want to quantify the efficiency of intracluster star formation. We present CO(1–0) and CO(2–1) observations, made with the IRAM-30 m telescope, towards the ram-pressure stripped tail northeast of NGC 4388 in Virgo. We selected HII regions found all along the tails, together with dust patches, as observing targets. We detect molecular gas in 4 positions along the tail, with masses between 7 × 105 to 2 × 106M⊙. Given the large distance from the NGC 4388 galaxy, the molecular clouds must have formed in situ, from the HI gas plume. We compute the relation between surface densities of star formation and molecular gas in these regions, and find that the star formation has very low efficiency. The corresponding depletion time of the molecular gas can be up to 500 Gyr and more. Since this value exceeds a by far Hubble time, this gas will not be converted into stars, and will stay in a gaseous phase to join the intracluster medium.
Key words: galaxies: evolution / galaxies: clusters: individual: Virgo / galaxies: clusters: intracluster medium / galaxies: ISM / galaxies: interactions
© ESO, 2015
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