Massive black holes and their role in galaxy evolution


Images of the host galaxy of a quasar at redshift z=6.234, seen with the Hubble Space Telescope (top panel), which reveals the young stellar component; and with the Atacama Large Millimeter/sub-millimeter Array, which traces the gas (second panel) and the dust in which stars are formed (third panel). The last panel combines the information from all the previous panels, thus revealing the synergy of the different phases of gas and star formation. Credits: Adapted from Decarli et al. (2019).

Quasars are massive black holes experiencing a phase of fast accretion. They reside in the center of galaxies and they are fueled by large gaseous reservoirs, which heats up due to friction and falls into the singularity. The released energy makes quasars the most luminous, non-transient sources in the Universe.

Quasars are ideal laboratories to study the Universe. On one side, because they are so bright, they can be identified and characterized at the farthest distances, thus acting as signposts of the large-scale structure and of the first mass overdensities in the young Universe. Moreover, they can be exploited as background sources to study the imprint, in absorption, due to the otherwise-invisible gas between the quasars and us. On the other hand, the study of the quasars themselves provides us with new and precious insights on how the first massive black holes formed, on the black hole demography along different cosmic times, on how they accrete material from the host galax, and how the enormous energy release affects the evolution of the galaxies where they reside.

OAS is actively engaged in all of these lines of research. OAS staff is involved in the search for new quasars at the furthest distances, and in their characterization; in the study of their environment and of the large-scale structures where they reside; in the painstaking reconstruction of the process of the history of (re)ionization of the infant Universe; in the study of black holes from cosmic dawn to the cosmic noon, the epoch of peak activity in the Universe, when half of nowadays stars formed; and finally, in the characterization of the interstellar medium of host galaxies, of the mechanisms by which it intercepts the energy released by the quasar, and of the repercussions of the black hole activity on galaxy evolution.

Involved staff: Andrea Comastri, Roberto Decarli, Roberto Gilli, Carlotta Gruppioni, Giorgio Lanzuisi, Federica Loiacono (PhD), Marco Mignoli, Riccardo Nanni (PhD), Alessandro Peca (PhD), Antonio Pensabene (PhD), Eros Vanzella