Mini-Seminar on Galaxy Evolution and Environment

by guest students of the HGSFP Extragalactic Astronomy Junior Research Group of T. Lisker at ZAH/ARI. Everyone interested is very welcome to attend! The program is as follows:

10:30h
Sami-Matias Niemi
PhD student at the University of Turku, Finland
Student Support Astronomer at the Nordic Optical Telescope
Groups of Galaxies - Bound or Not?
Groups of galaxies contain a large fraction of all galaxies in the Universe. These density enhancements in the sky and in the redshift space are important cosmological indicators of the distribution of matter in the Universe, and may provide important clues for galaxy formation. Groups of galaxies are, in general, divided into a large number of different classes, for example, loose, poor, compact and fossil groups. Despite the classifications or therefore, from the observational point of view, groups of galaxies and their member galaxies, are not extremely well defined. In this talk I discuss the most common group finding algorithm: the Friends-of-Friends, and show that significant fraction of groups generated with the FoF are gravitationally unbound.

11:00h
Suk Kim
Master student at Chungnam National University, Korea
Ultraviolet Properties of Dwarf Elliptical Galaxies in the Virgo Cluster
We present the Ultraviolet properties of a sample of early-type dwarf galaxies (dwarf ellipticals, nucleated dwarf ellipticals, and dwarf lenticulars ) in Virgo cluster. We used the GALEX GR3 data in near-ultraviolet (NUV) and far-ultraviolet (FUV) passbands combined with spectro-photometric data available at other wavelengths. Based on the UV to optical or near-infrared color-magnitude relation (CMR), we confirmed discontinuity between massive and dwarf galaxies suggesting different population as FUV source between massive and dwarf ellipticals. We found the dwarf lenticulars and peculiar dwarf ellipticals show distinct locus from that of ordinary dwarf ellipticals in CMR. This indicates the UV properties of dwarf lenticulars are different to those of ordinary dwarf ellipticals, suggesting a different formation and evolution. We also discuss a hint of environmental effects for the UV properties of dwarf elliptical galaxies.

11:30h
Ralf Kotulla
PhD student at the University of Hertfordshire, UK
Galaxies in the Redshift Desert from z=1 to z=2.5
The Redshift Desert covers the enigmatic range from z~1 to z~2.5, where the universe assembled most of its current stellar mass, but is hard to study spectrocopically, with no strong lines in the optical window.
After a short introduction I will review our approach to study galaxies in this redshift range using our innovative photometric redshift code GAZELLE in combination with our chemically consistent GALEV evolutionary synthesis models. Galaxy models with a starburst at some stage during their evolution play a crucial role in this analysis: They not only explain the short and very blue phases during the burst, but during their much longer postburst phases reach extremely red colours in the range observed for Extremely Red Objects (EROs) and Distant Red Galaxies (DRGs). I will present first results from the study of Deep Fields and outline our plans for the future.