Special Universe Talk: ALMA view of a massive spheroid progenitor: a compact rotating core of molecular gas in an AGN host at z=2.226

by Margherita Talia (University of Bologna, Italy)

Thursday 19 Jul 2018, 11:00 → 12:00 Europe/Berlin

Seminar room "Telescopium" (European Southern Observatory (ESO), Karl-Schwarzschild-Str. 2, 85748 Garching)

Abstract: Massive star-forming galaxies with centrally concentrated luminosity profiles at z>2 have been suggested to be the direct progenitors of compact quiescent galaxies (cQGs) at z=1.5-3. Some works have been very recently published on the properties of the ionized gas, dust continuum and X-ray emission of samples of compact star-forming galaxies. However, until now there are only a few sources that have been spatially resolved with ALMA. This kind of observations allow not only the study of the general properties of the molecular gas, like density and gas depletion time-scale, but also the measurement of its size and the study of its kinematic, that are fundamental information to understand the evolution of cQGs progenitors.  Margherita will present ALMA observations of GMASS 0953, a candidate progenitor of cQGs at z=2.226. We measure for the first time the size of the dust and molecular gas emission of GMASS 0953 that we find to be extremely compact (about 1 kpc). This result, coupled with a very high ISM density (log(n) about 5.5 cm–3), a low gas mass fraction (about 0.2) and a short gas depletion timescale (about 150 Myr) imply that GMASS 0953 is experiencing an episode of intense star-formation in its central region that will rapidly exhaust its gas reservoirs, likely aided by AGN-induced feedback. We are therefore witnessing in this galaxy the rare and short-lived phase immediately before star-formation quenching.  Kinematic analysis of the CO(6-5) line shows evidence of rapidly-rotating gas (Vrot=320 km/s), as observed also in a handful of similar sources at the same redshift. On-going quenching mechanisms could either destroy the rotation or leave it intact leading the galaxy to evolve into a rotating quiescent galaxy. 

Margherita is a Cluster guest. Local host: Paola Popesso (TUM)

! Room change, not at European Southern Observatory (ESO), Karl-Schwarzschild-Str. 2, 85748 Garching. Seminar room "Telescopium"