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The origin of the supermassive black hole masses MSMBH discovered at the highest redshifts is still actively debated. Moreover the statistically significant relation of MSMBH with bulge luminosities LV, extended on several magnitude orders, confirms a common physical process linking small (≤ 1pc) to large (kpcs) size scales. The Spectral Energy Distributions (SEDs) of two z=3.8 radio galaxies 4C41.17 and TN J2007-1316, best-fitted by evolved early type galaxy and starburst scenarios also imply masses of stellar remnants. Computed with the evolutionary code Pegase.3, the cumulated stellar black hole mass MsBH reach up to several 109M⊙, similar to MSMBH at same z. We propose the SMBH growth is due to the migration of the stellar dense residues (sBH) towards the galaxy core by dynamical friction. Discussed in terms of time-scales, this process which is linking AGN and star formation, also fully justifies the famous relation MSMBH-LV.
The HeRGÉ (Herschel Radio Galaxy Evolution) project consists of a sample of 70 radio galaxies in the range 1 < z < 5.2. They benefit from continuous coverage from 3 to 870μm with Spitzer, Herschel and sub-mm ground-based instruments (SCUBA, LABOCA). As a calorimeter, IR is an excellent proxy to estimate the contribution of both AGN and starburst, making of radio galaxies perfect candidates to provide new insights into the relationship between AGN and their host galaxies. The IR SED fitting with empirical templates reveals that radio galaxies are luminous and that their black holes and their host galaxies are not growing simultaneously. Extending the SED to optical/near-IR on a subsample of 12 radio galaxies spanning 1 < z < 4 reveal the necessity of three components to reproduce the observations. Making use of the evolutionary code PEGASE.3 and an AGN torus model, we are able to estimate parameters from the AGN torus, the evolved stellar population and the starburst (SB). They reveal that radio galaxies are massive, evolved, forming the bulk of their mass at very high redshift in a short timescale, but experience episodic, strong SB events, often associated with an AGN activity.
Distant radio galaxies, hosted by massive ellipticals, follow the galaxy evolution process on an extremely large (0 ≥ z ≥7) time-scale ≥ 1012Gyrs, up to primeval galaxies. The new evolutionary code Pégase.3 predicts on similar time-scales, the coupled stellar and dust emissions of various galaxy types: starbursts and Hubble sequence types. All z=0 templates are fitted on local observations at ages ≃13 Gyrs (except irregulars at 9 Gyrs). The multi-λ spectral energy distributions (SEDs) of two z=3.8 radiogalaxies, including the most recent Herschel data from the HeRGÉ consortium, are interpreted in the observer's frame by Rocca-Volmerange et al. (2012) with Pégase.3. The apparent SEDs are fitted at best with the sum of a young starburst and an older early-type population, an AGN simple model is taken into account. These results favor massive gas-rich mergers at work in evolved galaxies at z≃4. Massive starbursts would be at the origin of galaxy evolution initiated at the earliest epochs (zfor≥10). The possible relation with super massive black holes is still debated.
Recent improvements of spectrophotometric evolutionary models are described. New stellar libraries in the near-infrared (JHK) allow extension of the synthetic spectral Atlas of galaxies down to 10μm. From analyses in the far-UV and visible, observed colors and counts of faint galaxies are fitted by modelling a standard luminosity evolution and a low value of ωo(≃ 0.1) while, in a ωo=1 Universe, models only fit data with a standard luminosity evolution and a number density evolution ≃ (1 + z)1.8: such a modelling is simulating a merging process. Another solution would be a tidally triggered star formation rate in a model in which galaxies form by hierarchical clustering of a dominant dark matter component. From evolution of M/L ratio, these models allow to link observed luminosity functions with mass distributions predicted from galaxy formation models and then to significantly connect evolution to formation models. Nevertheless these two models are not sufficient to fit some observational data such as the Hubble diagrams and faint galaxy counts in the near-infrared, the bright galaxy counts in visible and the Extragalactic Background Light. So new evolution scenarios are needed implying other constraints for cosmological parameters.
Among the observations of heavy s-process elements at the surface of very metal poor stars (population II stars), Peterson 1976 and Spite and Spite 1977 recently showed that the ratio of the abundances of these elements against that of Fe increases with increasing [Fe/H].
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