IPAC Seminar: Guillermo Barro -- The progenitors of compact quiescent galaxies at z~2

The remarkably small and compact sizes of massive quiescent galaxies at z~2 has fueled multiple studies that investigate different evolutionary scenarios to explain how these galaxies formed. A missing part of the puzzle is the nature of their progenitors. Such progenitors are expected to be massive, compact, star-forming galaxies at higher redshifts. However, direct evidence for such counterparts has proven difficult to obtain using only the HST optical images, which probe the rest-frame UV at redshifts z > 2. UV morphologies can easily miss large, massive, red hosts. Such camouflaged components would, however, be easily visible in the near-IR. Using the deepest HST WFC3/F160W imaging data from the CANDELS survey, that probes the optical rest-frame bands at z>2, in combination with NIR slitless spectroscopy from 3D-HST, we are able to identify a significant population of galaxies with similar structural properties as the quiescent population but without fully suppressed star-formation. The number density of these sources account for the observed increment in the density of massive quiescent galaxies between z=2 and 3, while their estimated luminosity-weighted ages are consistent with a formation epoch of ~1 Gyr. For some of these objects we detect prominent Balmer breaks and Balmer absorption lines that supports the post-starburst hypothesis. Interestingly enough, we also find a high rate of X-ray detections among these galaxies (> 40%) indicating that the triggering of an AGN could play a fundamental role in the quenching process.