An Infrared View of the Coevolution of Massive Blackholes and Galaxies

Abstract

Massive blackhole (MBH) growth is now recognized as a critical ingredient of galaxy formation and evolution. To investigate the interplay between MBH growth and galaxy evolution, we have used the capabilities of the Spitzer Space Telescope to study active galactic nuclei (AGN) and luminous infrared galaxies. We have tested the unification model for radio-loud AGN by finding that radio quasars and some FRII radio galaxies follow a correlation between low-frequency radio and the 70 um emission, two presumably isotropic indicators of nuclear radiation. We have found that mid-IR obscuration (characterized by the strength of the silicate feature) correlates with the X-ray obscuration (characterized by the HI column density), such that low HI columns correspond to silicate emission while high columns correspond to silicate absorption, for various types of AGN. We have demonstrated that in situ electron acceleration is required for both jet and lobe emission in M87. We have measured aromatic features in local AGN, demonstrated the diverse nature (star formation vs. AGN) of the far-IR emission mechanism, and constructed the star formation luminosity functions of the AGN hosts. These luminosity functions are flatter than that of field galaxies, implying that the interplay between star formation and nuclear activity enhances both processes. For luminous infrared galaxies (LIRGs), we have characterized galaxy morphologies of a complete sample of LIRGs at z~1 and found that LIRGs at z~1 are as asymmetric as local ones, implying similar conditions within galaxies lead to a LIRG level of star formation.