Browsing by Author "Carraro, R."

Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    Multiwavelength monitoring of the nucleus in PBC?J2333.9-2343: the giant radio galaxy with a blazar-like core
    (2023) Hernandez-Garcia, L.; Panessa, F.; Bruni, G.; Bassani, L.; Arevalo, P.; Patino-Alvarez, V. M.; Tramacere, A.; Lira, P.; Sanchez-Saez, P.; Bauer, F. E.; Chavushyan, V; Carraro, R.; Forster, F.; Arancibia, A. M. Munoz; Ubertini, P.
    PBC J2333.9-2343 is a giant radio galaxy at z = 0.047 with a bright central core associated to a blazar nucleus. If the nuclear blazar jet is a new phase of the jet activity, then the small orientation angle suggests a dramatic change of the jet direction. We present observations obtained between 2018 September and 2019 January (cadence larger than three days) with Effeslberg, SMARTS-1.3m, ZTF, ATLAS, Swift, and Fermi-LAT, and between 2019 April and 2019 July (daily cadence) with SMARTS-1.3 m and ATLAS. Large (>2 x) flux increases are observed on time-scales shorter than a month, which are interpreted as flaring events. The cross correlation between the SMARTS-1.3 m monitoring in the NIR and optical shows that these data do not show significant time lag within the measured errors. A comparison of the optical variability properties between non-blazars and blazars AGN shows that PBC J2333.9-2343 has properties more comparable to the latter. The SED of the nucleus shows two peaks, that were fitted with a one-zone leptonic model. Our data and modelling show that the high energy peak is dominated by External Compton from the dusty torus with mild contribution from Inverse Compton from the jet. The derived jet angle of 3 deg is also typical of a blazar. Therefore, we confirm the presence of a blazar-like core in the centre of this giant radio galaxy, likely a Flat Spectrum Radio Quasar with peculiar properties.
  • No Thumbnail Available
    Item
    The Evolving AGN Duty Cycle in Galaxies Since z ∼ 3 as Encoded in the X-Ray Luminosity Function
    (2020) Delvecchio, I.; Daddi, E.; Aird, J.; Mullaney, J. R.; Bernhard, E.; Grimmett, L. P.; Carraro, R.; Cimatti, A.; Zamorani, G.; Caplar, N.; Vito, F.; Elbaz, D.; Rodighiero, G.
    We present a new modeling of the X-ray luminosity function (XLF) of active galactic nuclei (AGNs) out to z similar to 3, dissecting the contributions of main-sequence (MS) and starburst (SB) galaxies. For each galaxy population, we convolved the observed galaxy stellar mass (M-*) function with a grid of M-*- independent Eddington ratio (lambda(EDD)) distributions, normalized via empirical black hole accretion rate (BHAR) to star formation rate (SFR) relations. Our simple approach yields an excellent agreement with the observed XLF since z similar to 3. We find that the redshift evolution of the observed XLF can only be reproduced through an intrinsic flattening of the lambda(EDD) distribution and with a positive shift of the break lambda*, consistent with an antihierarchical behavior. The AGN accretion history is predominantly made by massive (10(10) < M-* < 10(11) M-circle dot) MS galaxies, while SB-driven BH accretion, possibly associated with galaxy mergers, becomes dominant only in bright quasars, at log(L-X/erg s(-1)) > 44.36 + 1.28 x (1 + z). We infer that the probability of finding highly accreting (lambda(EDD) > 10%) AGNs significantly increases with redshift, from 0.4% (3.0%) at z = 0.5%-6.5% (15.3%) at z = 3 for MS (SB) galaxies, implying a longer AGN duty cycle in the early universe. Our results strongly favor a M-*-dependent ratio between BHAR and SFR, as BHAR/SFR proportional to M-*(0.73[+0.22,-0.29]), supporting a nonlinear BH buildup relative to the host. Finally, this framework opens potential questions on super-Eddington BH accretion and different lambda(EDD) prescriptions for understanding the cosmic BH mass assembly.