From the first stars to the first quasars

Observations of the most luminous quasars at redshift z>6 reveal the existence of numerous supermassive black holes (SMBHs, > 10^9 Msun) already in place about twelve billion years ago. The growth of these first SMBHs is still a major challenge for theoretical models. If it starts from black hole (BH) remnants of Population III stars (light seeds with mass ~100 Msun), it requires super-Eddington accretion. An alternative route is to start from heavy seeds formed by the direct collapse of gas on to a ~10^5 Msun BH. In addition, the interstellar medium (ISM) of the galaxies hosting these quasars are observed to be chemically mature systems, with metallicities Z>Zsun and dust masses >10^8 Msun, similar to that of more evolved, local galaxies. The connection between the rapid growth of the SMBHs and the fast chemical evolution of the host galaxy is one of the most puzzling issues for theoretical models.
I will present the results of our cosmological, data constrained semi-analytic model in which we investigate the relative role of light and heavy seeds as BH progenitors of the first SMBHs, self-consistently following the evolution of the chemical properties (metals and dust abundance) in the host galaxies ISM.