Astronomy & Astrophysics

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Issue		A&A Volume 437, Number 1, July I 2005
Page(s)		L19 - L22
Section		Letters
DOI		10.1051/0004-6361:200500127

A&A 437, L19-L22 (2005)
DOI: 10.1051/0004-6361:200500127

Letter

A large H I cloud near the centre of the Virgo cluster

T. Oosterloo¹ and J. van Gorkom^{2, 3}

¹ Netherlands Foundation for Research in Astronomy, Postbus 2, 7990 AA, Dwingeloo, The Netherlands
e-mail: oosterloo@astron.nl
² Department of Astronomy, Columbia University, 550 West 120th Street, New York, NY 10027, USA
³ Kapteyn Astronomical Institute, University of Groningen, Postbus 800, 9700 AV Groningen, The Netherlands

(Received 22 April 2005 / Accepted 18 May 2005)

Abstract
We report the discovery of a large $\ion$ cloud in the central regions of the Virgo cluster. It is $110\times 25$ kpc in size and contains $3.4\times 10^8~M_\odot$ of $\ion$ . The morphology and kinematics of this cloud strongly suggest that it consists of $\ion$ removed from the galaxy NGC 4388 by ram-pressure stripping. It is more likely the result of an interaction of the ISM of NGC 4388 with the hot halo of the M 86 group and not with the ICM centred on M 87. The large extent of the plume suggests that gas stripped from cluster galaxies can remain neutral for at least 10⁸ yr. Locally, the column density is well above 10²⁰ cm^-2, suggesting that the intra-cluster $\ion{H}{ii}$ regions known to exist in Virgo may have formed from gas stripped from cluster galaxies. The existence of the $\ion$ plume suggests that stripping of infalling spirals contributes to the enrichment of the ICM. The $\ion$ object in the Virgo cluster recently reported by Minchin et al. (2005, ApJ, 622, L21) may have a similar origin and may therefore not be a "dark galaxy".

Key words: intergalactic medium -- galaxies: interaction -- galaxies: clusters: individual: Virgo cluster -- galaxies: individual: NGC 4388

SIMBAD Objects in preparation

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