S E M I N A R IDepartament d'Astronomia i Astrofísica
Universitat de València
Stellar tidal streams in nearby galaxies: mapping the minor merger rate in the local Universe with small telescopes
Dr David Martinez-Delgado
Max-Planck Institut für Astronomie, Heidelberg, Alemanya
Saló de Graus de Matemàtiques
Divendres 27 abril 2012
Within the hierarchical framework for galaxy formation, minor merging and tidal interactions are expected to shape large galaxies to this day. As part of a pilot survey, we have carried out ultra-deep, wide-field imaging of some isolated spiral galaxies similar to the Milky Way in the local universe with data taken at small (0.1 to 0.5-meter diameter), robotic telescopes that provide exquisite surface brightness sensitivity. Our observational effort has led to the discovery of previously undetected giant stellar structures in the halos of these galaxies, likely associated with debris from tidally disrupted satellites. Our collection of galaxies presents an assortment of tidal phenomena exhibiting strikingly diverse morphological characteristics. The comparison with available stellar halo simulations set in a Lambda-Cold Dark Matter cosmology suggests that this extraordinary variety of morphological specimens detected in our survey could represent one of the first comprehensive pieces of evidence to support that the hierarchical formation scenarios predicted for the formation of galaxies similar to our Galaxy. I also present the discovery of a tidal stream around a nearby dwarf irregular galaxy with our small telescopes. Follow-up observations with Subaru telescope show this stream completely resolved into stars, providing observational evidence of a minuscule merger in a LMC-type system in the local universe. This result suggests that dwarf accretion could play an important role in the star formation history and evolution of nearby dwarf galaxies.