Thesis Topic: Extreme star formation in quasar host at the cosmic high noon

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Thesis Supervisor: Evanthia Hatziminaglou

 

 

 

Abstract

Luminous star formation and AGN episodes are fundamental to assembling galaxies at z > 1, but the nature of these episodes, and their connection to each other, remain unclear. In part, this is due to an incomplete understanding of stellar and black hole mass assembly events. Furthermore, it is still unclear if star formation events and AGN activity can directly affect one another. A direct relation is motivated by models for galaxy assembly to improve consistency between predictions and observations, most often via `quenching' of star formation by an AGN. However, observational studies of quenching remain inconclusive. 

At the same time, the role o mergers in triggering concomitant nuclear and star formation activities is also unclear. It has been established, both observationally and theoretically, that major mergers do trigger such activities, even concomitantly, at redshifts of ~2, however secular processes are also known to play an important role.

The purpose of the proposed project it to approach the issue of a possible causality between AGN activity and star formation in the AGN population and the role of mergers and secular processes as triggers of these activities from multiple angles, and can be broken down into:

1) The study of star formation on the hosts of optically bright SDSS quasars, hosts of type 2 AGN sample selected based on emission line properties, and a comparison between two type 1 and type 2 samples, matched in optical properties and redshift. Herschel-SPIRE fluxes from the Herschel point source catalogue will be used as indicators of the star formation. Already existing Spectral Energy Distribution fitting codes a well as AGN models will be used but updates are foreseen. 

2) The study of the dust properties of 28 far-infrared (FIR) bright SDSS quasars at 2<z<4 with available ALMA band 7 continuum data and comparison with results on submm galaxies (SMGs) from the ALMA archive and the literature. This part of the study will help placing the FIR-bright quasar population into the more general context of submm galaxies and their properties. 

3) The preparation of follow up proposals in the optical, near-infrared and submm with a variety of facilities (VLT, WHT, GTC, ALMA, NOEMA) in order to study the multiplicities found in the pilot study of the 28 quasars, identify the new sources found in the vicinity of the quasars and study their nature. An effort will be also made to confirm (or refute) what seem to be single point-like submm counterparts of quasars, implying secular processes at play.