Context. Feedback from accreting supermassive black holes (SMBHs) is often identified as the main mechanism responsible for regulating star formation in active galactic nucleus (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 (SFR), 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.
ABSTRACT We present the catalog of optical and infrared counterparts of the Chandra COSMOS-Legacy Survey, a 4.6 Ms Chandra program on the 2.2 deg2 of the COSMOS field, combination of 56 new ...overlapping observations obtained in Cycle 14 with the previous C-COSMOS survey. In this Paper we report the i, K, and 3.6 m identifications of the 2273 X-ray point sources detected in the new Cycle 14 observations. We use the likelihood ratio technique to derive the association of optical/infrared (IR) counterparts for 97% of the X-ray sources. We also update the information for the 1743 sources detected in C-COSMOS, using new K and 3.6 m information not available when the C-COSMOS analysis was performed. The final catalog contains 4016 X-ray sources, 97% of which have an optical/IR counterpart and a photometric redshift, while 54% of the sources have a spectroscopic redshift. The full catalog, including spectroscopic and photometric redshifts and optical and X-ray properties described here in detail, is available online. We study several X-ray to optical (X/O) properties: with our large statistics we put better constraints on the X/O flux ratio locus, finding a shift toward faint optical magnitudes in both soft and hard X-ray band. We confirm the existence of a correlation between X/O and the the 2-10 keV luminosity for Type 2 sources. We extend to low luminosities the analysis of the correlation between the fraction of obscured AGNs and the hard band luminosity, finding a different behavior between the optically and X-ray classified obscured fraction.
ABSTRACT The COSMOS-Legacy survey is a 4.6 Ms Chandra program that has imaged 2.2 deg2 of the COSMOS field with an effective exposure of ks over the central 1.5 deg2 and of ks in the remaining area. ...The survey is the combination of 56 new observations obtained as an X-ray Visionary Project with the previous C-COSMOS survey. We describe the reduction and analysis of the new observations and the properties of 2273 point sources detected above a spurious probability of 2 × 10−5. We also present the updated properties of the C-COSMOS sources detected in the new data. The whole survey includes 4016 point sources (3814, 2920 and 2440 in the full, soft, and hard band). The limiting depths are 2.2 × 10−16, 1.5 × 10−15, and 8.9 × 10−16 in the 0.5-2, 2-10, and 0.5-10 keV bands, respectively. The observed fraction of obscured active galactic nuclei with a column density >1022 cm−2 from the hardness ratio (HR) is ∼50 %. Given the large sample we compute source number counts in the hard and soft bands, significantly reducing the uncertainties of 5%-10%. For the first time we compute number counts for obscured (HR > −0.2) and unobscured (HR < −0.2) sources and find significant differences between the two populations in the soft band. Due to the unprecedent large exposure, COSMOS-Legacy area is three times larger than surveys at similar depths and its depth is three times fainter than surveys covering similar areas. The area-flux region occupied by COSMOS-Legacy is likely to remain unsurpassed for years to come.
We present a comprehensive study of the Na I λ5890, 5895 (Na I D) resonant lines in the Sloan Digital Sky Survey (SDSS, DR7) spectroscopic sample to look for neutral gas outflows in the local ...galaxies. Individual galaxy spectra are stacked in bins of stellar mass (M⋆) and star formation rate (SFR) to investigate the dependence of galactic wind occurrence and velocity as a function of the galaxy position in the SFR-M⋆ plane. While in most cases the interstellar medium (ISM) absorption and emission lines are at the galaxy systemic velocity, in massive galaxies (M⋆ > 5 × M⊙) at the high SFR tail (SFR > 10−12 M⊙ yr−1) we find evidence of a significant blue-shifted Na I D absorption, which we interpret as evidence of neutral outflowing gas. The occurrence of the blue-shifted absorption in the stacked spectra does not depend on the contribution of the nuclear activity as it is observed at the same significance for purely star-forming (SF) galaxies, active galactic nuclei (AGN), and composite systems at fixed SFR. We confirm, instead, for all classes of objects a clear dependence on the galaxy disc inclination: the blueshift is the largest and the Na I D equivalent width the smallest for face-on galaxies, while the absorption feature is at the systemic velocity for edge-on systems. This indicates that the neutral outflow is mostly perpendicular or biconical with respect to the galactic disc. We also compare the kinematics of the neutral gas with the ionized gas phase as traced by the OIIIλ5007, Hα, NIIλ6548, and NIIλ6584 emission lines in the same galaxy spectra. Differently for the neutral gas phase, all the emission lines show evidence of perturbed kinematics only in galaxies with a significant level of nuclear activity, and they are independent of the galactic disc inclination. This would suggest that, while neutral winds originate from the galactic disc and are powered by SF feedback, ionized outflows are instead due to AGN feedback originating from the black hole accretion disc. In both the neutral and ionized gas phases, the observed wind velocities (of the order of 100−200 kms−1) suggest that the outflowing gas remains bound to the galaxy with no definitive effect on the gas reservoir.
Negative feedback from active galactic nuclei (AGN) is considered a key mechanism in shaping galaxy evolution. Fast, extended outflows are frequently detected in the AGN host galaxies at all ...redshifts and luminosities, both in ionised and molecular gas. However, these outflows are only potentially able to quench star formation, and we are still lacking decisive evidence of negative feedback in action. Here we present observations obtained with the Spectrograph for INtegral Field Observations in the Near Infrared (SINFONI) H- and K-band integral-field of two quasars at z ~ 2.4 that are characterised by fast, extended outflows detected through the Oiiiλ5007 line. The high signal-to-noise ratio of our observations allows us to identify faint narrow (FWHM< 500 km s-1) and spatially extended components in Oiiiλ5007 and Hα emission associated with star formation in the host galaxy. This star formation powered emission is spatially anti-correlated with the fast outflows. The ionised outflows therefore appear to be able to suppress star formation in the region where the outflow is expanding. However, the detection of narrow spatially extended Hα emission indicates star formation rates of at least ~50–90 M⊙ yr-1, suggesting either that AGN feedback does not affect the whole galaxy or that many feedback episodes are required before star formation is completely quenched. On the other hand, the narrow Hα emission extending along the edges of the outflow cone may also lead also to a positive feedback interpretation. Our results highlight the possible double role of galaxy-wide outflows in host galaxy evolution.
AbstractWe release the AllWISE counterparts and Gaia matches to 106 573 and 17 665 X-ray sources detected in the ROSAT 2RXS and XMMSL2 surveys with |b| > 15°. These are the brightest X-ray sources in ...the sky, but their position uncertainties and the sparse multi-wavelength coverage until now rendered the identification of their counterparts a demanding task with uncertain results. New all-sky multi-wavelength surveys of sufficient depth, like AllWISE and Gaia, and a new Bayesian statistics based algorithm, Nway, allow us, for the first time, to provide reliable counterpart associations. Nway extends previous distance and sky density based association methods and, using one or more priors (e.g. colours, magnitudes), weights the probability that sources from two or more catalogues are simultaneously associated on the basis of their observable characteristics. Here, counterparts have been determined using a Wide-field Infrared Survey Explorer (WISE) colour-magnitude prior. A reference sample of 4524 XMM/Chandra and Swift X-ray sources demonstrates a reliability of ∼94.7 per cent (2RXS) and 97.4 per cent (XMMSL2). Combining our results with Chandra-COSMOS data, we propose a new separation between stars and AGN in the X-ray/WISE flux-magnitude plane, valid over six orders of magnitude. We also release the Nway code and its user manual. Nway was extensively tested with XMM-COSMOS data. Using two different sets of priors, we find an agreement of 96 per cent and 99 per cent with published Likelihood Ratio methods. Our results were achieved faster and without any follow-up visual inspection. With the advent of deep and wide area surveys in X-rays (e.g. SRG/eROSITA, Athena/WFI) and radio (ASKAP/EMU, LOFAR, APERTIF, etc.) Nway will provide a powerful and reliable counterpart identification tool.
We study the incidence of nuclear obscuration on a complete sample of 1310 active galactic nuclei (AGN) selected on the basis of their rest-frame 2-10 keV X-ray flux from the XMM-COSMOS survey, in ...the redshift range 0.3 < z < 3.5. We classify the AGN as obscured or unobscured on the basis of either the optical spectral properties and the overall SED or the shape of the X-ray spectrum. The two classifications agree in about 70 per cent of the objects, and the remaining 30 per cent can be further subdivided into two distinct classes: at low luminosities X-ray unobscured AGN do not always show signs of broad lines or blue/UV continuum emission in their optical spectra, most likely due to galaxy dilution effects; at high-luminosities broad-line AGN may have absorbed X-ray spectra, which hints at an increased incidence of small-scale (sub-parsec) dust-free obscuration. We confirm that the fraction of obscured AGN is a decreasing function of the intrinsic X-ray luminosity, while the incidence of absorption shows significant evolution only for the most luminous AGN, which appear to be more commonly obscured at higher redshift. We find no significant difference between the mean stellar masses and star formation rates of obscured and unobscured AGN hosts. We conclude that the physical state of the medium responsible for obscuration in AGN is complex and mainly determined by the radiation environment (nuclear luminosity) in a small region enclosed within the gravitational sphere of influence of the central black hole, but is largely insensitive to the wider scale galactic conditions.
Abstract
We present ALMA observations at 107.291 GHz (band 3) and 214.532 GHz (band 6) of GMASS 0953, a star-forming galaxy at z = 2.226 hosting an obscured active galactic nucleus (AGN) that has ...been proposed as a progenitor of compact quiescent galaxies (QGs). We measure for the first time the size of the dust and molecular gas emission of GMASS 0953 that we find to be extremely compact (∼1 kpc). This result, coupled with a very high interstellar medium (ISM) density (n ∼ 105.5 cm−3), a low gas mass fraction (∼0.2), and a short gas depletion time-scale (∼150 Myr), implies that GMASS 0953 is experiencing an episode of intense star formation in its central region that will rapidly exhaust its gas reservoirs, likely aided by AGN-induced feedback, confirming its fate as a compact QG. Kinematic analysis of the CO(6–5) line shows evidence of rapidly rotating gas (Vrot = 320$^{+92}_{-53}$ km s−1), as observed also in a handful of similar sources at the same redshift. On-going quenching mechanisms could either destroy the rotation or leave it intact leading the galaxy to evolve into a rotating QG.
Abstract
Similarly to the cosmic star formation history, the black hole accretion rate density of the Universe peaked at 1 < z < 3. This cosmic epoch is hence best suited for investigating the ...effects of radiative feedback from active galactic nucleus (AGN). Observational efforts are under way to quantify the impact of the AGN feedback, if any, on their host galaxies. Here, we present a study of the molecular gas content of AGN hosts at z ∼ 1.5 using CO2−1 line emission observed with Atacama Large Millimeter/sub-mm Array (ALMA) for a sample of 10 AGNs. We compare this with a sample of galaxies without an AGN matched in redshift, stellar mass and star formation rate. We detect CO in three AGNs with L
CO ∼ 6.3–25.1 × 109 L⊙, which translates to a molecular hydrogen gas mass of 2.5–10 × 1010 M⊙ assuming conventional conversion factor of αCO ∼ 3.6. Our results indicate a >99 per cent probability of lower depletion time-scales and lower molecular gas fractions in AGN hosts with respect to the non-AGN comparison sample. We discuss the implications of these observations on the impact that AGN feedback may have on star formation efficiency of z >1 galaxies.
We present X-shooter at Very Large Telescope observations of a sample of 10 luminous, X-ray obscured quasi-stellar objects (QSOs) at z ~ 1.5 from the XMM-COSMOS survey, expected to be caught in the ...transitioning phase from starburst to active galactic nucleus (AGN)-dominated systems. The main selection criterion is X-ray detection at bright fluxes (...) coupled to red optical-to-near-infrared-to-mid-infrared colours. Thanks to its large wavelength coverage, X-shooter allowed us to determine accurate redshifts from the presence of multiple emission lines for five out of six targets for which we had only a photometric redshift estimate, with an 80 per cent success rate, significantly larger than what is observed in similar programs of spectroscopic follow-up of red QSOs. We report the detection of broad and shifted components in the OIII ...5007, 4959 complexes for six out of eight sources with these lines observable in regions free from strong atmospheric absorptions. The full width at half-maximum (FWHM) associated with the broad components are in the range FWHM ~ 900-1600 km s..., larger than the average value observed in Sloan Digital Sky Survey type 2 AGN samples at similar observed OIII luminosity, but comparable to those observed for QSO/ultraluminous infrared galaxies systems for which the presence of kpc scale outflows has been revealed through integral field unit spectroscopy. Although the total outflow energetics (inferred under reasonable assumptions) may be consistent with winds accelerated by stellar processes, we favour an AGN origin for the outflows given the high outflow velocities observed (...) and the presence of strong winds also in objects undetected in the far-infrared. (ProQuest: ... denotes formulae/symbols omitted.)
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