Master thesis defense by Jiazhe Li

A Quasar Sample based on Astrometric Data from Gaia Data Release 3

Abstract

The Smaller NOT Astrometric Quasar Survey (SNAQS) aims to construct a 100% complete sample of quasars with mG < 19 within a 245-square-degree region around the North Galactic Pole.

It serves as a pilot survey for the more extensive Purely Astrometric Quasar Survey (PAQS) planned for the southern sky. Building upon the purely astrometric selection methods introduced by Heintz et al. (2015)—which established that approximately 80% of stationary sources near the galactic poles are quasars—we analyzed a new set of spectra from SNAQS.

In this work, we determined the actual fraction of quasars among these stationary sources and identified missing populations by comparing our results with existing spectroscopic surveys. Based on these findings, we project the expected yields for PAQS. Finally, we leveraged recent Gaia Data Release 3 to propose a more efficient and accurate methodology for selecting astrometrically stationary objects as quasar candidates.

Censor

Frank Grundahl