Context. Feedback from accreting supermassive black holes is often identified as the main mechanism responsible for regulating star-formation in AGN host galaxies. However, the relationships between AGN activity, radiation, winds, and star-formation are complex and still far from being understood. Aims. We study scaling relations between AGN properties, host galaxy properties and AGN winds. We then evaluate the wind mean impact on the global star-formation history, taking into account the short AGN duty cycle with respect to that of star-formation. Methods. We first collect AGN wind observations for 94 AGN with detected massive winds at sub-pc to kpc spatial scales. We then fold AGN wind scaling relations with AGN luminosity functions, to evaluate the average AGN wind mass-loading factor as a function of cosmic time. Results. We find strong correlations between the AGN molecular and ionised wind mass outflow rates and the AGN bolometric luminosity. The power law scaling is steeper for ionised winds (slope 1.29±0.38) than for molecular winds (0.76±0.06), meaning that the two rates converge at high bolometric luminosities. The molecular gas depletion timescale and the molecular gas fraction of galaxies hosting powerful AGN driven winds are 3-10 times shorter and smaller than those of main-sequence galaxies with similar star-formation rate, stellar mass and redshift. These findings suggest that, at high AGN bolometric luminosity, the reduced molecular gas fraction may be due to the destruction of molecules by the wind, leading to a larger fraction of gas in the atomic ionised phase. The AGN wind mass-loading factor η =ṀOF /SFR is systematically higher than that of starburst driven winds. Conclusions. Our analysis shows that AGN winds are, on average, powerful enough to clean galaxies from their molecular gas only in massive systems at z < ∼ 2, i.e. a strong form of co-evolution between SMBHs and galaxies appears to break down for the least massive galaxies.

In the standard scenario for galaxy evolution young star-forming galaxies transform into red bulge-dominated spheroids, where star formation has been quenched. To explain this transformation, a strong negative feedback generated by accretion onto a central supermassive black hole is often invoked. The depletion of gas resulting from quasar-driven outflows should eventually stop star-formation across the host galaxy and lead the black hole to "suicide" by starvation. Direct observational evidence for a major quasar feedback onto the host galaxy is still missing, because outflows previously observed in quasars are generally associated with the ionized component of the gas, which only accounts for a minor fraction of the total gas content, and typically occurrs in the central regions. We used the IRAM PdB Interferometer to observe the CO(1−0) transition in Mrk 231, the closest quasar known. Thanks to the wide band we detected broad wings of the CO line, with velocities of up to 750 km s −1 and spatially resolved on the kpc scale. These broad CO wings trace a giant molecular outflow of about 700 M /year, far larger than the ongoing star-formation rate (∼200 M /year) observed in the host galaxy. This wind will totally expel the cold gas reservoir in Mrk 231 in about 10 7 yrs, therefore halting the starformation activity on the same timescale. The inferred kinetic energy in the molecular outflow is ∼1.2 × 10 44 erg/s, corresponding to a few percent of the AGN bolometric luminosity, which is very close to the fraction expected by models ascribing quasar feedback to highly supersonic shocks generated by radiatively accelerated nuclear winds. Instead, the contribution by the SNe associated with the starburst fall short by several orders of magnitude to account for the kinetic energy observed in the outflow. The direct observational evidence for quasar feedback reported here provides solid support to the scenarios ascribing the observed properties of local massive galaxies to quasar-induced large-scale winds.

Aims. The goal of this work is to measure the evolution of the Galaxy Stellar Mass Function and of the resulting Stellar Mass Density up to redshift 4, in order to study the assembly of massive galaxies in the high redshift Universe. Methods. We have used the GOODS-MUSIC catalog, containing ∼3000 Ks-selected galaxies with multi-wavelength coverage extending from the U band to the Spitzer 8 µm band, of which 27% have spectroscopic redshifts and the remaining fraction have accurate photometric redshifts. On this sample we have applied a standard fitting procedure to measure stellar masses. We compute the Galaxy Stellar Mass Function and the resulting Stellar Mass Density up to redshift 4, taking into proper account the biases and incompleteness effects. Results. Within the well known trend of global decline of the Stellar Mass Density with redshift, we show that the decline of the more massive galaxies may be described by an exponential timescale of 6 Gyr up to z 1.5, and proceeds much faster thereafter, with an exponential timescale of 0.6 Gyr. We also show that there is some evidence for a differential evolution of the Galaxy Stellar Mass Function, with low mass galaxies evolving faster than more massive ones up to z 1−1.5 and that the Galaxy Stellar Mass Function remains remarkably flat (i.e. with a slope close to the local one) up to z 1−1.3. Conclusions. The observed behaviour of the Galaxy Stellar Mass Function is consistent with a scenario where about 50% of presentday massive galaxies formed at a vigorous rate in the epoch between redshift 4 and 1.5, followed by a milder evolution until the present-day epoch.

Abstract. We present a detailed analysis of the stellar mass content of galaxies up to z = 2.5 as obtained from the K20 spectrophotometric galaxy sample. We have applied and compared two different methods to estimate the stellar mass M * from broad-band photometry: a Maximal Age approach, where we maximize the age of the stellar population to obtain the maximal mass compatible with the observed R − K color, and a Best Fit model, where the best-fitting spectrum to the complete UBVRIzJK s multicolor distribution is used. We find that the M * /L ratio decreases with redshift: in particular, the average M * /L ratio of early type galaxies decreases with z, with a scatter that is indicative of a range of star-formation time-scales and redshift of formation. More important, the typical M * /L ratio of massive early type galaxies is larger than that of less massive ones, suggesting that their stellar population formed at higher z. We show that the final K20 galaxy sample spans a range of stellar masses from M * = 10 9 M to M * = 10 12 M : massive galaxies (M * ≥ 10 11 M ) are common at 0.5 < z < 1, and are detected also up to z 2. We compute the Galaxy Stellar Mass Function at various z, of which we observe only a mild evolution (i.e. by 20-30%) up to z 1. At z > 1, the evolution in the normalization of the GSMF appears to be much faster: at z 2, about 35% of the present day stellar mass in objects with M * 10 11 M appear to have assembled. We also detect a change in the physical nature of the most massive galaxies: at z < ∼ 0.7, all galaxies with M > 10 11 M are early type, while at higher z a population of massive star-forming galaxies progressively appears. We finally analyze our results in the framework of Λ-CDM hierarchical models. First, we show that the large number of massive galaxies detected at high z does not violate any fundamental Λ-CDM constraint based on the number of massive DM halos. Then, we compare our results with the predictions of several renditions of both semianalytic as well as hydro-dynamical models. The predictions from these models range from severe underestimates to slight overestimates of the observed mass density at ≤2. We discuss how the differences among these models are due to the different implementation of the main physical processes.