The SECCO survey: searching for very dark galaxies within Ultra Compact HVCs

tenuto da Michele Bellazzini (INAF, Osservatorio Astronomico di Bologna)

  • Data: 12 febbraio 2015 dalle 14:00 alle 15:30

  • Luogo: Aula seminari, piano -1, via Ranzani 1

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I present the first results of SECCO, a survey aimed at obtaining deep wide-field imaging of Ultra Compact High Velocity HI Clouds (UCHVCs) that have been recently discovered and proposed as the gaseous components of faint dwarf galaxies in the Local Group and its surroundings. While the absence of stars in these clouds is not sufficient to exclude that they are associated with a Dark Matter halo (i.e. they may be dwarf galaxies that were unable to form stars), the presence of a stellar counterpart would confirm the galaxian nature of these objects, as in the case of the the faint dwarf irregular Leo P . We have used the two twins LBC cameras  mounted on the Large Binocular Telescope to observe the fields of 25 UCHVC from the list provided by the ALFALFA survey. The spectroscopic follow up of one candidate identified during the survey led us to the discovery of a star-forming stellar counterpart for one of the targeted UCHVCs. This is very likely a nearly star-less star-forming dwarf galaxy, a kind of missing-link between normal dwarfs and completely dark ones that are predicted to exist in Lambda-CDM cosmology.