A Complete Census of the Quasar Population in the Large Survey Era

University Of Arizona, Tucson AZ

Investigators

Abstract

A longstanding problem in astrophysics is to understand how galaxies form and develop throughout their lifetimes. Such understanding is necessary to uncover how our Universe evolved and to gain insight into the origin of our own Milky Way Galaxy. One important aspect of understanding galaxy formation and evolution is to study supermassive black holes (BHs) at the centers of massive galaxies. These BHs light up as quasars during the relatively brief phases when the BHs accumulate most of their mass through accretion. Over the past half-century, considerable effort has been devoted to capturing these accretion spurts through surveys at optical wavelengths. In general, these surveys have been limited to the most luminous sources, or small numbers within deep fields; however, quasar observations are undergoing an exponential leap in depth and breadth enabled by new and upcoming surveys. The Baryon Oscillation Spectroscopic Survey of the Sloan Digital Sky Survey III (SDSS-III/BOSS) final data release will include about 160,000 quasars at redshifts around 2--3, and its successor, the SDSS-IV/eBOSS, will obtain spectra of over 600,000 quasars at redshifts around 1--2. The investigators will complement the quasar samples from these cosmology surveys with their own high redshift programs to form a complete picture of the evolution of faint quasars from optical surveys. The investigators will integrate the science program into a tiered outreach program at Pima Community College, a Hispanic-Serving Institution located in Tucson. The outreach program includes (1) public lectures at the East Campus, a region not reached by The University of Arizona programs, (2) lectures to Astronomy 101 students at Pima integrating an overview of Active Galactic Nuclei into the regular curriculum, and (3) engagement of a small number of Pima students in the research program itself by teaching the basics of quasar spectroscopy and including the students in the eBOSS program to visually inspect quasar spectra. More technically, exploring this method in the regime of sparse data (an important precursor for LSST), the team will utilize Large Synoptic Survey Telescope (LSST) reductions of SDSS imaging data to identify about 400 quasars at redshifts around z = 4 through variability selection. Finally, the team will use deep CFHT imaging to reach faint quasars (i_AB = 24) at redshift around z = 5. Together, these data will probe several magnitudes below the break luminosity over a wide redshift range and will reach nearly all objects classifiable as quasars over 5 Gyr of cosmic evolution, including the crucial epoch when both star formation and quasar activity peak. Leveraging massive spectroscopic surveys as well as separate observations with large telescopes, the team will complete the census of the faint end of the quasar luminosity function to redshift around z = 5 and obtain new measurements of high-z clustering, thereby providing strong constraints for models of quasar lifetimes and feedback physics. These measurements will also provide strong constraints on the quasar ionizing background during the epoch of He II reionization. Finally, a key aspect of the project is to develop tools needed for an era when quasar surveys will be dominated by systematics rather than by statistics. The team will accomplish this by building models for quasar properties constrained by existing observations but which provide useful projections for future surveys. These models will be used to guide target selection for spectroscopic efforts, identify quasars from photometric data, and train photometric redshift estimation; furthermore, they will provide insight into intrinsic quasar properties, such as continuum and dust extinction.