The HI content of the recently discovered field dwarf galaxy APPLES1

A. Tarchi, J. Ott, A. Pasquali, I. Ferreras, P. Castangia, S. S. Larsen

Published 2005-08-18Version 1

We present observations in a search for neutral hydrogen associated with the recently detected field dwarf galaxy APPLES1, performed with the Parkes radiotelescope. The observed radio spectrum shows no evident (> 3sigma rms) line emission indicating an upper limit for the HI content of the galaxy of ~ 10E6 solar masses and providing an upper value for the M(HI)/L(B) ratio equal to 2.4 solar masses/solar luminosities. The low value of the HI content suggested by the observations, together with the galaxy optical morphology, might indicate that APPLES1 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 APPLES1 belongs to the class of mixed dwarf irregular/spheroidal transition-type galaxies. We also conclude that the relatively low neutral gas mass in APPLES1 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.