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Which galaxies host bars and disks? A study of the Coma Cluster ; (2)First results of Herschel and the HerMES extragalactic survey

Resumen

(1) In this talk I will present a recent study of the bar fraction in the Coma Cluster galaxies based on a sample of 190 galaxies selected from the Sloan Digital Sky Survey Data Release 6 and observed with the Hubble Space Telescope (HST) Advanced Camera for Survey (ACS). The unprecedented resolution of the HST-ACS images allows us to explore the presence of bars, detected by visual classification, throughout a luminosity range of 9 mag (-23 < Mr < -14), permitting us to study the poor known region of dwarf galaxies. We find that bars are hosted by galaxies in a tight range of both luminosities (-22 < Mr < -17) and masses (10⁹ < M/M? < 10¹¹). This result holds when compared with a sample of bright/massive field galaxies. In addition, we find that the bar fraction does not vary significantly when going from the center to the cluster outskirts, implying that cluster environment plays a second-order role in bar formation/evolution. The shape of the bar fraction distribution with respect to both luminosity and mass is well matched by the luminosity distribution of disk galaxies in Coma, indicating that bars are good tracers of cold stellar disks. We discuss the implications of our results for the formation and evolution scenarios of bars and disks.

(2) The Herschel Space Observatory was launched on 14 May 2009. After a short commissioning and performance verification period, the science demonstration observations started in September 2009. Herschel is carrying out now routine science observations. The three instruments (SPIRE, PACS and HIFI) are working extremely well. The first results of the many Herschel Key Projects were presented at the ESLAB 2010 conference in ESTEC on May 4-7 2010 and will be published in a special issue of Astronomy and Astrophysics. In this talk I will introduce the observing capabilities of Herschel and will review some of the first results in extragalactic astronomy and in particular those of the Herschel Multi-tiered Extragalactic Survey (HerMES).