Browsing by Subject "quasars: general"

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  • Dey, Lankeswar; Valtonen, M. J.; Gopakumar, A.; Zola, S.; Hudec, R.; Pihajoki, P.; Ciprini, S.; Matsumoto, K.; Sadakane, K.; Kidger, M.; Nilsson, K.; Mikkola, S.; Sillanpaa, A.; Takalo, L. O.; Lehto, H. J.; Berdyugin, A.; Piirola, V.; Jermak, H.; Baliyan, K. S.; Pursimo, T.; Caton, D. B.; Alicavus, F.; Baransky, A.; Blay, P.; Boumis, P.; Boyd, D.; Campas Torrent, M.; Campos, F.; Carrillo Gomez, J.; Chandra, S.; Chavushyan, V.; Dalessio, J.; Debski, B.; Drozdz, M.; Er, H.; Erdem, A.; Escartin Perez, A.; Ramazani, V. Fallah; Filippenko, A. V.; Gafton, E.; Ganesh, S.; Garcia, F.; Gazeas, K.; Godunova, V.; Gomez Pinilla, F.; Gopinathan, M.; Haislip, J. B.; Harmanen, J.; Hurst, G.; Janik, J.; Jelinek, M.; Joshi, A.; Kagitani, M.; Karjalainen, R.; Kaur, N.; Keel, W. C.; Kouprianov, V. V.; Kundera, T.; Kurowski, S.; Kvammen, A.; LaCluyze, A. P.; Lee, B. C.; Liakos, A.; Lindfors, E.; Lozano de Haro, J.; Mugrauer, M.; Naves Nogues, R.; Neely, A. W.; Nelson, R. H.; Ogloza, W.; Okano, S.; Pajdosz-Smierciak, U.; Pandey, J. C.; Perri, M.; Poyner, G.; Provencal, J.; Raj, A.; Reichart, D. E.; Reinthal, R.; Reynolds, T.; Saario, J.; Sadegi, S.; Sakanoi, T.; Salto Gonzalez, J. -L.; Sameer; Schweyer, T.; Simon, A.; Siwak, M.; Soldan Alfaro, F. C.; Sonbas, E.; Steele, I.; Stocke, J. T.; Strobl, J.; Tomov, T.; Tremosa Espasa, L.; Valdes, J. R.; Valero Perez, J.; Verrecchia, F.; Vasylenko, V.; Webb, J. R.; Yoneda, M.; Zejmo, M.; Zheng, W.; Zielinski, P. (2018)
    Results from regular monitoring of relativistic compact binaries like PSR 1913+16 are consistent with the dominant (quadrupole) order emission of gravitational waves (GWs). We show that observations associated with the binary black hole (BBH) central engine of blazar OJ 287 demand the inclusion of gravitational radiation reaction effects beyond the quadrupolar order. It turns out that even the effects of certain hereditary contributions to GW emission are required to predict impact flare timings of OJ 287. We develop an approach that incorporates this effect into the BBH model for OJ 287. This allows us to demonstrate an excellent agreement between the observed impact flare timings and those predicted from ten orbital cycles of the BBH central engine model. The deduced rate of orbital period decay is nine orders of magnitude higher than the observed rate in PSR 1913+16, demonstrating again the relativistic nature of OJ 287's central engine. Finally, we argue that precise timing of the predicted 2019 impact flare should allow a test of the celebrated black hole "no-hair theorem" at the 10% level.
  • Georgakakis, A.; Comparat, J.; Merloni, A.; Ciesla, L.; Aird, J.; Finoguenov, A. (2019)
    A semi-empirical model is presented that describes the distribution of active galactic nuclei (AGNs) on the cosmicweb. It populates dark-matter haloes in N-body simulations (MultiDark) with galaxy stellar masses using empirical relations based on abundance matching techniques, and then paints accretion events on these galaxies using state-of-the-art measurements of the AGN occupation of galaxies. The explicit assumption is that the large-scale distribution of AGN is independent of the physics of black hole fuelling. The model is shown to be consistent with current measurements of the two-point correlation function of AGN samples. It is then used to make inferences on the halo occupation of the AGN population. Mock AGNs are found in haloes with a broad distribution of masses with a mode of approximate to 10(12) h(-1) M-circle dot and a tail extending to cluster-size haloes. The clustering properties of the model AGN depend only weakly on accretion luminosity and redshift. The fraction of satellite AGN in the model increases steeply toward more massive haloes, in contrast with some recent observational results. This discrepancy, if confirmed, could point to a dependence of the halo occupation of AGN on the physics of black hole fuelling.
  • Civano, F.; Marchesi, S.; Comastri, A.; Urry, M. C.; Elvis, M.; Cappelluti, N.; Puccetti, S.; Brusa, M.; Zamorani, G.; Hasinger, G.; Aldcroft, T.; Alexander, D. M.; Allevato, V.; Brunner, H.; Capak, P.; Finoguenov, A.; Fiore, F.; Fruscione, A.; Gilli, R.; Glotfelty, K.; Griffiths, R. E.; Hao, H.; Harrison, F. A.; Jahnke, K.; Kartaltepe, J.; Karim, A.; LaMassa, S. M.; Lanzuisi, G.; Miyaji, T.; Ranalli, P.; Salvato, M.; Sargent, M.; Scoville, N. J.; Schawinski, K.; Schinnerer, E.; Silverman, J.; Smolcic, V.; Stern, D.; Toft, S.; Trakhenbrot, B.; Treister, E.; Vignali, C. (2016)
    The COSMOS-Legacy survey is a 4.6 Ms Chandra program that has imaged 2.2 deg(2) of the COSMOS field with an effective exposure of similar or equal to 160 ks over the central 1.5 deg(2) and of similar or equal to 80 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 x 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 x 10(-16), 1.5 x 10(-15), and 8.9 x 10(-16) erg cm(-2) s(-1)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 >10(22) cm(-2) from the hardness ratio (HR) is similar to 50(-16)(+17)%. 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.
  • LaMassa, Stephanie M.; Glikman, Eilat; Brusa, Marcella; Rigby, Jane R.; Ananna, Tonima Tasnim; Stern, Daniel; Lira, Paulina; Urry, C. Megan; Salvato, Mara; Alexandroff, Rachael; Allevato, Viola; Cardamone, Carolin; Civano, Francesca; Coppi, Paolo; Farrah, Duncan; Komossa, S.; Lanzuisi, Giorgio; Marchesi, Stefano; Richards, Gordon; Trakhtenbrot, Benny; Treister, Ezequiel (2017)
    We present results of a ground-based near-infrared campaign with Palomar TripleSpec, Keck NIRSPEC, and Gemini GNIRS to target two samples of reddened active galactic nucleus (AGN) candidates from the 31 deg(2) Stripe 82 X-ray survey. One sample, which is similar to 89% complete to K <16 (Vega), consists of eight confirmed AGNs, four of which were identified with our follow-up program, and is selected to have red R - K colors (> 4, Vega). The fainter sample (K > 17, Vega) represents a pilot program to follow-up four sources from a parent sample of 34 that are not detected in the single-epoch SDSS catalog and have WISE quasar colors. All 12 sources are broad-line AGNs (at least one permitted emission line has an FWHM exceeding 1300 km s(-1)) and span a redshift range 0.59 <z <2.5. Half the (R - K)-selected AGNs have features in their spectra suggestive of outflows. When comparing these sources to a matched sample of blue Type 1 AGNs, we find that the reddened AGNs are more distant (z > 0.5), and a greater percentage have high X-ray luminosities (L-X,L- full > 10(44) erg s(-1)). Such outflows and high luminosities may be consistent with the paradigm that reddened broad-line AGNs represent a transitory phase in AGN evolution as described by the major merger model for black hole growth. Results from our pilot program demonstrate proof of concept that our selection technique is successful in discovering reddened quasars at z > 1 missed by optical surveys.
  • Viitanen, A.; Allevato, V.; Finoguenov, A.; Bongiorno, A.; Cappelluti, N.; Gilli, R.; Miyaji, T.; Salvato, M. (2019)
    Aims. We study the spatial clustering of 632 (1130) XMM-COSMOS active galactic nuclei (AGNs) with known spectroscopic or photometric redshifts in the range z = [0.1-2.5] in order to measure the AGN bias and estimate the typical mass of the hosting dark matter (DM) halo as a function of AGN host galaxy properties. Methods. We created AGN subsamples in terms of stellar mass, M-*, and specific black hole accretion rate, L-X/M-*, to study how AGN environment depends on these quantities. Further, we derived the M-*-M-halo relation for our sample of XMM-COSMOS AGNs and compared it to results in literature for normal non-active galaxies. We measured the projected two-point correlation function w(p)(r(p)) using both the classic and the generalized clustering estimator, based on photometric redshifts, as probability distribution functions in addition to any available spectroscopic redshifts. We measured the large-scale (r(p) greater than or similar to 1h(-1) Mpc) linear bias b by comparing the clustering signal to that expected of the underlying DM distribution. The bias was then related to the typical mass of the hosting halo M-halo of our AGN subsamples. Since M-* and L-X/M-* are correlated, we matched the distribution in terms of one quantity and we split the distribution in the other. Results. For the full spectroscopic AGN sample, we measured a typical DM halo mass of log(M-halo/h(-1)M(circle dot)) = 12.79(-0.43)(+0.26), similar to galaxy group environments and in line with previous studies for moderate-luminosity X-ray selected AGN. We find no significant dependence on specific accretion rate L-X/M-* with log(M-halo/h(-1)M(circle dot)) = 13.06(-0.38)(+0.23) and log(M-halo/h(-1)M(circle dot)) = 12.97(-1.26)(+0.39) for low and high Lx/M, subsamples, respectively. We also find no difference in the hosting halos in terms of M, with log(M-halo/h(-1)M(circle dot)) = 12.93(-0.62)(+0.31) (low) and log(M-halo/h(-1)M(circle dot)) = 12.90(-0.62)(+0.30) (high). By comparing the M-*-M-halo relation derived for XMM-COSMOS AGN subsamples with what is expected for normal non-active galaxies by abundance matching and clustering results, we find that the typical DM halo mass of our high M-* AGN subsample is similar to that of non-active galaxies. However, AGNs in our low M-* subsample are found in more massive halos than non-active galaxies. By excluding AGNs in galaxy groups from the clustering analysis, we find evidence that the result for low M-* may be due to larger fraction of AGNs as satellites in massive halos.
  • Suh, Hyewon; Civano, Francesca; Hasinger, Guenther; Lusso, Elisabeta; Lanzuisi, Giorgio; Marchesi, Stefano; Trakhtenbrot, Benny; Allevato, Viola; Cappelluti, Nico; Capak, Peter L.; Elvis, Martin; Griffiths, Richard E.; Laigle, Clotilde; Lira, Paulina; Riguccini, Laurie; Rosario, David J.; Salvato, Mara; Schawinski, Kevin; Vignali, Cristian (2017)
    We investigate the star formation properties of a large sample of similar to 2300 X-ray-selected Type 2 Active Galactic Nuclei (AGNs) host galaxies out to z similar to 3 in the Chandra COSMOS Legacy Survey in order to understand the connection between the star formation and nuclear activity. Making use of the existing multi-wavelength photometric data available in the COSMOS field, we perform a multi-component modeling from far-infrared to near-ultraviolet using a nuclear dust torus model, a stellar population model and a starburst model of the spectral energy distributions (SEDs). Through detailed analyses of SEDs, we derive the stellar masses and the star formation rates (SFRs) of Type 2 AGN host galaxies. The stellar mass of our sample is in the range of 9 <logM(stellar)/M-circle dot <12 with uncertainties of similar to 0.19 dex. We find that Type 2 AGN host galaxies have, on average, similar SFRs compared to the normal star-forming galaxies with similar M-stellar and redshift ranges, suggesting no significant evidence for enhancement or quenching of star formation. This could be interpreted in a scenario, where the relative massive galaxies have already experienced substantial growth at higher redshift (z > 3), and grow slowly through secular fueling processes hosting moderate-luminosity AGNs.