Browsing by Author "Peca, A."

Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    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?
    (2019) Gilli, R.; Mignoli, M.; Peca, A.; Nanni, R.; Prandoni, I.; Liuzzo, E.; D'Amato, Q.; Brusa, M.; Calura, F.; Caminha, G. B.; Chiaberge, M.; Comastri, A.; Cucciati, O.; Cusano, F.; Grandi, P.; Decarli, R.; Lanzuisi, G.; Mannucci, F.; Pinna, E.; Tozzi, P.; Vanzella, E.; Vignali, C.; Vito, F.; Balmaverde, B.; Citro, A.; Cappelluti, N.; Zamorani, G.; Norman, C.
    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 quasi-stellar object (QSO) SDSS J1030 +0524. Based on a 6 h VLT/MUSE and on a 4 h 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 members are distributed within 400 kpc from the FRII core. Nonetheless, the whole structure is likely much more extended, as one of the members was serendipitously found at similar to 800 kpc projected separation. The classic radio structure of the FRII itself extends for similar to 600 kpc across the sky. Most of the identified overdensity members are blue, compact galaxies that are actively forming stars at rates of similar to 8-60 M-circle dot yr(-1). For the brightest of them, a half-light radius of 2 .2 similar to 0 .8 kpc at 8000A rest-frame was determined based on adaptive optics-assisted observations with LBT/SOUL in the Ks band. We do not observe any strong galaxy morphological segregation or concentration around the FRII core. This suggests that the structure is far from being virialized and likely constitutes the progenitor of a local massive galaxy group or cluster caught in its main assembly phase. Based on a 500 ks Chandra ACIS-I observation, we found that the FRII nucleus hosts a luminous QSO (L2-10 keV = 1 .3 similar to 10(44) erg s(-1), intrinsic and rest-frame) that is obscured by Compton-thick absorption (N-H = 1.5 +/- 0 .6 x 10(24) cm(-2)). Under standard bolometric corrections, the total measured radiative power (L-rad similar to 4 x 10(45) erg s(-1)) is similar to the jet kinetic power that we estimated from radio observations at 150MHz (P-kin = 6.3 x 10(45) erg s(-1)), in agreement with what is observed in powerful jetted AGN. Our Chandra observation is the deepest so far for a distant FRII within a galaxy overdensity. It revealed significant di ffuse X-ray emission within the region that is covered by the overdensity. In particular, X-ray emission extending for similar to 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 di ffuse X-ray emission. These objects are concentrated within 200 kpc in the plane of the sky and within 450 kpc in radial separation. Three of them are even more concentrated and fall within 60 kpc in both transverse and radial distance. The probability of observing four out of the six z = 1.7 sources by chance at the edge of the di ffuse 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 di ffuse 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.
  • No Thumbnail Available
    Item
    The deep Chandra survey in the SDSS J1030+0524 field
    (2020) Nanni, R.; Gilli, R.; Vignali, C.; Mignoli, M.; Peca, A.; Marchesi, S.; Annunziatella, M.; Brusa, M.; Calura, F.; Cappelluti, N.; Chiaberge, M.; Comastri, A.; Iwasawa, K.; Lanzuisi, G.; Liuzzo, E.; Marchesini, D.; Prandoni, I.; Tozzi, P.; Vito, F.; Zamorani, G.; Norman, C.
    We present the X-ray source catalog for the similar to 479 ks Chandra exposure of the SDSS J1030+0524 field, which is centered on a region that shows the best evidence to date of an overdensity around a z > 6 quasar, and also includes a galaxy overdensity around a Compton-thick Fanaroff-Riley type II (FRII) radio galaxy at z = 1.7. Using wavdetect for initial source detection and ACIS Extract for source photometry and significance assessment, we create preliminary catalogs of sources that are detected in the full (0.5-7.0 keV), soft (0.5-2.0 keV), and hard (2-7 keV) bands, respectively. We produce X-ray simulations that mirror our Chandra observation to filter our preliminary catalogs and achieve a completeness level of > 91% and a reliability level of similar to 95% in each band. The catalogs in the three bands are then matched into a final main catalog of 256 unique sources. Among them, 244, 193, and 208 are detected in the full, soft, and hard bands, respectively. The Chandra observation covers a total area of 335 arcmin(2) and reaches flux limits over the central few square arcmins of similar to 3 x 10(-16), 6 x 10(-17), and 2 x 10(-16) erg cm(-2) s(-1) in the full, soft, and hard bands, respectively This makes J1030 field the fifth deepest extragalactic X-ray survey to date. The field is part of the Multiwavelength Survey by Yale-Chile (MUSYC), and is also covered by optical imaging data from the Large Binocular Camera (LBC) at the Large Binocular Telescope (LBT), near-infrared imaging data from the Canada France Hawaii Telescope WIRCam (CFHT/WIRCam), and Spitzer IRAC. Thanks to its dense multi-wavelength coverage, J1030 represents a legacy field for the study of large-scale structures around distant accreting supermassive black holes. Using a likelihood ratio analysis, we associate multi-band (r, z, J, and 4.5 mu m) counterparts for 252 (98.4%) of the 256 Chandra sources, with an estimated reliability of 95%. Finally, we compute the cumulative number of sources in each X-ray band, finding that they are in general agreement with the results from the Chandra Deep Fields.