Marco Chiaberge, Space Telescope Science Institute
Colloquium
Wednesday, April 23, 2014 · 3:30 - 5 PM
TITLE: Radio Galaxies near and far: what can learn from these spectacular active galactic nuclei?
ABSTRACT: Radio galaxies are a spectacular class of Active Galactic Nuclei (AGN). They are powered by accretion of matter onto the most massive black holes and they are hosted by the largest galaxies in the Universe. I will focus on results from our studies of radio galaxies at all distances, from the closest objects to high redshifts, when the Universe was less than a quarter of the age it is now. I will show how low-redshift radio galaxies observed with HST and other instruments allowed us a better understanding of the innermost regions of AGNs and of their black holes. While we still don’t know the details of the physics of the jet launch, we learned that the nuclei of lower power objects are fundamentally different from all other AGNs. In recent years, we focused on the cosmological evolution of these sources. I will show the first results of the analysis of a new sample of high redshift (1<z<2) low-luminosity radio galaxies that present significant differences with respect to their analogues in the local Universe. That is an epoch at which mergers are still producing significant effects on the formation of these large galaxies. Low power radio galaxies are also very efficient beacons for clusters of galaxies at high redshifts, which has important bearings on cosmology. I will also present highlights form our most recent HST survey of high-power radio galaxies at z>1, which will allow a detailed comparison of the properties of the environment of these sources over more than four decades in radio power.
ABSTRACT: Radio galaxies are a spectacular class of Active Galactic Nuclei (AGN). They are powered by accretion of matter onto the most massive black holes and they are hosted by the largest galaxies in the Universe. I will focus on results from our studies of radio galaxies at all distances, from the closest objects to high redshifts, when the Universe was less than a quarter of the age it is now. I will show how low-redshift radio galaxies observed with HST and other instruments allowed us a better understanding of the innermost regions of AGNs and of their black holes. While we still don’t know the details of the physics of the jet launch, we learned that the nuclei of lower power objects are fundamentally different from all other AGNs. In recent years, we focused on the cosmological evolution of these sources. I will show the first results of the analysis of a new sample of high redshift (1<z<2) low-luminosity radio galaxies that present significant differences with respect to their analogues in the local Universe. That is an epoch at which mergers are still producing significant effects on the formation of these large galaxies. Low power radio galaxies are also very efficient beacons for clusters of galaxies at high redshifts, which has important bearings on cosmology. I will also present highlights form our most recent HST survey of high-power radio galaxies at z>1, which will allow a detailed comparison of the properties of the environment of these sources over more than four decades in radio power.
