EDP Sciences
Free access
Volume 444, Number 1, December II 2005
Page(s) 133 - 136
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20053634

A&A 444, 133-136 (2005)
DOI: 10.1051/0004-6361:20053634

The H I content of the recently discovered field dwarf galaxy APPLES 1

A. Tarchi1, 2, J. Ott3, A. Pasquali4, I. Ferreras5, P. Castangia2, 6 and S. S. Larsen7

1  INAF - Istituto di Radioastronomia, via Gobetti 101, 40129 Bologna, Italy
    e-mail: a.tarchi@ira.cnr.it
2  INAF - Osservatorio Astronomico di Cagliari, Poggio dei Pini, Strada 54, 09012 Capoterra (CA), Italy
3  CSIRO Australia Telescope National Facility, Cnr Vimiera & Pembroke Roads, Marsfield NSW 2122, Australia
4  Institute of Astronomy, ETH, Hönggerberg, HPF, 8093 Zürich, Switzerland
5  Department of Physics and Astronomy, University College London, Gower St., London WC1E 6BT, UK
6  Università di Cagliari, Dipartimento di Fisica, Cittadella Universitaria, 09042 Monserrato (CA), Italy
7  European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching, Germany

(Received 14 June 2005 / Accepted 12 August 2005 )

We present observations in a search for neutral hydrogen associated with the recently detected field dwarf galaxy APPLES 1 , performed with the Parkes radiotelescope. The observed radio spectrum shows no evident (>3$\sigma$ rms) line emission indicating an upper limit for the H I content of the galaxy of ~ $10^{6}\:\hbox{$M_{\odot}$ }$ and providing an upper value for the $M_{\rm HI}$/$L_{\rm B}$ ratio equal to 2.4 /. The low value of the H I content suggested by the observations, together with the galaxy optical morphology, might indicate that APPLES 1 is a dwarf spheroidal. This indication is in contrast with the evidence of recent star formation, which is typical for dwarf irregular galaxies. This may suggest that APPLES 1 belongs to the class of mixed dwarf irregular/spheroidal transition-type galaxies. We also conclude that the relatively low neutral gas mass in APPLES 1 can be explained by an extended and inefficient star formation process, without the need for a dramatic event such as enhanced star formation or a past encounter with a massive galaxy or galaxy group.

Key words: galaxies: individual: APPLES 1 -- galaxies: dwarf -- radio lines: ISM -- radio lines: galaxies

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© ESO 2005