VCV10 and Quaia samples IR-selec var. QSOs

We build a sample of nearly 2500 quasars that show statistically significant variability between the 2MASS and VHS. About 1500 of these come from the new Quaia sample based on Gaia spectra and about 1/3 of these have hardly been studied. The Quaia sample constitutes the main product of this work.

Based on ensemble variability and structure function analysis we demonstrate that the selected objects in our sample are representative of the typical quasar population and show behaviour, consistent with other quasar samples. Our analysis strengthens previous results, for example that variability decreases with the rest-frame wavelength and that it exhibits peaks for certain absolute magnitudes of the quasars. Similarly, the structure function shows an increase in variability for rest-frame time lags below ~1500d and a decrease for longer lags, just like in previous studies.

Our selection, even though it is based on two epochs only, seems to be surprisingly robust, showing up to ~11% contamination by quasars that show stable non-variable behaviour in ZTF.