arXiv subjects

Q. D'Amato

Publications and source records attributed to Q. D'Amato.

39 records · Page 3Linked to original sources

arXiv2019

Discovery of a galaxy overdensity around a powerful, heavily obscured FRII radio galaxy at z=1.7: star formation promoted by large-scale AGN feedback?

We report the discovery of a galaxy overdensity around a Compton-thick Fanaroff-Riley type II (FRII) radio galaxy at z=1.7 in the deep multiband survey around the z=6.3 QSO SDSS J1030+0524. Based on a 6hr VLT/MUSE and on a 4hr LBT/LUCI observation, we identify at least eight galaxy members in this structure with spectroscopic redshift z=1.687-1.699, including the FRII galaxy at z=1.699. Most of the identified overdensity members are blue, compact galaxies that are actively forming stars at rates of $\sim$8-60 $M_{\odot}$ yr$^{-1}$. Based on a 500ks Chandra ACIS-I observation we found that the FRII nucleus hosts a luminous QSO ($L_{2-10keV}=1.3\times10^{44}$ erg s$^{-1}$, intrinsic and rest-frame) that is obscured by Compton-thick absorption ($N_H=1.5\pm0.6\times 10^{24}$ cm$^{-2}$). Our Chandra observation, the deepest so far for a distant FRII within a galaxy overdensity, revealed significant diffuse X-ray emission within the region covered by the overdensity. In particular, X-ray emission extending for $\sim$240 kpc is found around the Eastern lobe of the FRII. Four out of the six MUSE star forming galaxies in the overdensity are distributed in an arc-like shape at the edge of this diffuse X-ray emission. The probability of observing by chance four out of the six $z=1.7$ sources at the edge of the diffuse emission is negligible. In addition, these four galaxies have the highest specific star formation rates of the MUSE galaxies in the overdensity and lie above the main sequence of field galaxies of equal stellar mass at z=1.7. We propose that the diffuse X-rays originate from an expanding bubble of gas that is shock-heated by the FRII jet, and that star formation is promoted by the compression of the cold interstellar medium of the galaxies around the bubble, which may be remarkable evidence of positive AGN feedback on cosmological scales. [shortened version]

astro-ph.GA↗

arXiv2018

The molecular gas content in obscured AGN at z > 1

The standard AGN-galaxy co-evolutionary scenario predicts a phase of deeply buried supermassive black hole growth coexisting with a starburst (SB) before feedback phenomena deplete the cold molecular gas reservoir of the galaxy and an optically luminous QSO is revealed ('SB-QSO evolutionary sequence'). The aim of this work is to measure the cold gas reservoir of three highly obscured QSOs to test if their gas fraction is similar to that of sub-millimeter galaxies (SMGs), as expected by some models, and place these measurements in the context of the SB-QSO framework. We target CO(1-0) transition in BzK4892, a Compton Thick (CT) QSO at z=2.6, CO(1-0) in BzK8608 and CO(2-1) in CDF153, two highly obscured QSOs at z=2.5 and z=1.5, respectively. For all these targets, we place 3$σ$ upper limits on the CO, with $L'_{CO} < (1.5÷2.8)\times 10^{10}$ K km/s pc$^2$. We also compare the molecular gas conditions of our targets with those of other systems at z>1, considering normal star forming galaxies and SMGs, unobscured and obscured AGN from the literature. For the AGN samples, we provide an updated and (almost) complete collection of targets with CO follow-up. BzK4892 displays a high star formation efficiency (SFE$=L_{IR}/L'_{CO}>410$ L$_{\odot}$/(K km s$^{-1}$ pc$^2$)) and a gas fraction $f_{gas}<0.1$. Less stringent constraints are derived for the other two targets ($f_{gas}<0.5$ and SFE$>10$). From the comparison with literature data, we found that a) obscured AGN at z>1 are associated with higher SFE and lower $f_{gas}$ with respect to star forming galaxies; b) mildly and highly obscured active galaxies have comparable gas fractions; c) the SFE of CT and obscured AGN are similar to those of unobscured AGN. Within the SB-QSO framework, these findings could be consistent with a scenario where feedback can impact the host galaxy already from the early phases of the SB-QSO sequence.

astro-ph.GA↗

arXiv2015

Application of the MST clustering to the high energy gamma-ray sky. I - New possible detection of high-energy gamma-ray emission associated with BL Lac objects

In this paper we show an application of the Minimum Spanning Tree (MST) clustering method to the high-energy gamma-ray sky observed at energies higher than 10 GeV in 6.3 years by the Fermi-Large Area Telescope. We report the detection of 19 new high-energy gamma-ray clusters with good selection parameters whose centroid coordinates were found matching the positions of known BL Lac objects in the 5th Edition of the Roma-BZCAT catalogue. A brief summary of the properties of these sources is presented.

astro-ph.HE↗