Spectroscopic Cosmological Surveys in the Far-IR

SPECTROSCOPIC COSMOLOGICAL SURVEYS IN THE FAR-IR L. Spinoglio 1 , M. Magliocchetti 1 , S. Tommasin 1 , A. M. Di Giorgio 1 , C. Gruppioni 2 , G. De Zotti 3 , A. Franceschini 4 , M. Vaccari 4 , K. Isaak 5 , F. Pozzi 6 and M.A. Malkan 7 arXiv:0909.5044v1 [astro-ph.CO] 28 Sep 2009 Istituto di Fisica dello Spazio interplanetario - INAF, Via Fosso del Cavaliere 100, 00133 Roma, Italy Osservatorio Astronomico di Bologna - INAF, Via Ranzani 1, 40127, Bologna, Italy Osservatorio Astronomico di Padova - INAF, Vicolo dell’Osservatorio 5, 35122 Padova, Italy Dipartimento di Astronomia - Universit´ a di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy University of Cardiff - School of Physics and Astronomy, 5 The Parade, Cardiff CF24 3YB, United Kingdom Dipartimento di Astronomia - Universit´ a di Bologna - INAF, Via Ranzani 1, 40127, Bologna, Italy Astronomy Division, University of California, Los Angeles, CA 90095-1547, USA Abstract We show the feasibility of spectroscopic cosmological surveys with the SAFARI instrument onboard of SPICA. The work is done through simulations that make use of both empirical methods, i.e. the use of observed luminosity functions and theoretical models for galaxy formation and evolution. The relations assumed between the line emis- sion to trace AGN and star formation activity have been derived from the observations of local samples of galaxies. The results converge to indicate the use of blind spec- troscopy with the SAFARI FTS at various resolutions to study galaxy evolution from the local to the distant (z∼3) Universe. Specifically, two different and independent galaxy evo- lution models predict about 7-10 sources to be spectro- scopically detected in more than one line in a 2’× 2’ SA- FARI field of view, down to the expected flux limits of SAFARI, with about 20% of sources to be detected at z>2. SPICA-SAFARI will be therefore excellent at de- tecting high-z sources and at assessing in a direct way their nature (e.g whether mainly AGN or Star Formation powered) thanks to blind spectroscopy. correlation for active galaxies in the local Universe, as the two processes appear - at least in local Seyfert galaxies (Tommasin et al , 2009) to be almost independent of each other. The Magorrian relation therefore has to find its origins at earlier epochs. The study of galaxy evolution necessarily implies in- vestigation of the full cosmic history of energy generation by stars (star formation and stellar evolution) and black holes (accretion), as well as of the energy loss processes such as the feedback from AGNs, because all these are responsible for the build up of the baryonic mass in the Universe and must ultimately be consistent and set up the observed local relation between luminosity and mass in galaxies. To understand the Magorrian relation we need to make the cosmic connections between stars in a galaxy and its massive black hole. The global accretion power, measured at X-rays (Hasinger et al , 2005) and the star formation power, measured by Hα and rest-frame UV ob- servations (Shim et al , 2009) were ∼20 times higher at z=1-1.5 than today. On a cosmic scale, the evolution of supermassive black holes (SMBHs) appears related to the evolution of the star-formation rate (SFR), strongly sug- gesting the presence of co-evolution (Marconi et al , 2004; Key words: Galaxies: evolution, active galactic nuclei, star- Merloni et al , 2004; Shankar et al , 2009). As suggested by various authors (Heckman et al , 2004; Granato et al , burst – Missions: SPICA 2004), the growth of bulges through SF may be directly linked to the growth of black holes through accretion. Quasars have been advocated as a source of negative feed- 1. Introduction back that would quench star formation, however no clear In the last years our perspective of galaxy evolution has evidence for this ”negative feedback” has yet been found, greatly changed thanks to two main findings: A) the strong while instead star formation is often, although not al- correlation observed in the local Universe between the ways, concomitant with AGN/QSO activity over rather mass of the black hole at the centre of a galaxy and the long duty cycles (100 Myr - few 100 Myr). It has also been velocity dispersion of the stellar component of the galactic realized that the optically bright phase of quasars covers bulge (the so-called Magorrian relation), and B) the evi- not more than one tenth of their host lifetime, as obser- generally constrain quasar lifetimes to the range dence that most, if not all, galaxies during their evolution vations yr. Optical studies of local galaxies show that pass through a FIR/submillimetre bright phase. most, if not A) The Magorrian relation (Magorrian et al , 1998; Ferrarese & Merrit all, , large galaxy spheroids host massive relic black-holes (Richstone et al , 1998) which, in turn, sug- 2000) implies that the processes of black hole growth - gests that a mass-accreting AGN phase is one through through mass accretion - and bulge formation - through which all galaxies pass. star formation - are intimately linked. While large ellipti- cal galaxies with old stellar bulges are known to follow the Magorrian relation, we are not able to explain this tight B) To account for the total energy generated by stars and that by black hole accretion, one first has to determine Proc. Workshop ‘The Space Infrared Telescope for Cosmology & Astrophysics: Revealing the Origins of Planets and Galaxies’ 6–8 July 2009, Oxford, United Kingdom