Wednesday

At the dawn of the Vera C. Rubin era, time-domain studies provide invaluable insights into the way galaxies change over time. Particularly, with the unprecedented depth of observations that LSST will bring, this behaviour may be tracked through redshift as galaxies evolve. In this early study, we use time-domain data from the Zwicky Transient Facility to measure the optical variability in apparent magnitude in ~12,000 galaxies in groups up to z=0.2. We use a BPT diagram to distinguish emission as either from an active galactic nucleus (AGN) or from star-formation. Results indicate that star-forming objects have high levels of variability, and that in these galaxies variability peaks at log(M*)~9.5. In addition to low mass, high variability favours intermediate specific star-formation rate, log(sSFR)~-10.5. We also find that variability decreases as a function of bulge-to-total ratio, with disky objects having higher variabilities than objects with larger bulges. These results paint a picture of high variability being an indicator of a low-mass AGN precluded by star-formation emission, followed by further growth of the bulge, reduced star-formation, increased AGN emission and subsequent quenching. With LSST, these results may soon be supported by deeper redshift observations, and the ability to track the variability of galaxies as they evolve from star-forming to quiescent.