Early Stage Researchers – Masters’ Papers

Non-isotropic feedback from accreting spinning black holes

Luca Sala (LMU), Elia Cenci, Pedro R Capelo, Alessandro Lupi and Massimo Dotti

Monthly Notices of the Royal Astronomical Society, Volume 500, Issue 4, February 2021, Pages 4788-4800 https://doi.org/10.1093/mnras/staa3552

ABSTRACT: Active galactic nuclei (AGNs) are massive black holes (BHs) caught in the act of accreting gas at the centre of their host galaxies. Part of the accreting mass is converted to energy and released into the surrounding medium, in a process loosely referred to as AGN feedback. Most numerical simulations include AGN feedback as a sub-grid model, wherein energy or momentum (or both) is coupled to the nearby gas. In this work, we implement a new momentum-driven model in the hydrodynamics code GIZMO, in which accretion from large scales is mediated by a sub-grid accretion disc model, and gas particles are stochastically kicked over a bi-conical region, to mimic observed kinetic winds. The feedback cone’s axis can be set parallel either to the angular momentum of the gas surrounding the BH or to the BH spin direction, which is self-consistently evolved within the accretion-disc model. Using a circumnuclear disc (CND) as a test bed, we find that (i) the conical shape of the outflow is always visible and is weakly dependent on the launching orientation and aperture, resulting in comparable mass inflows and outflows; (ii) the cone’s orientation is also similar amongst our tests, and it is not always the same as the initial value, due to the interaction with the CND playing a crucial role in shaping the outflow; and (iii) the velocity of the outflow, instead, differs and strongly depends on the interplay with the CND.

The MURALES survey. IV. Searching for nuclear outflows in 3C radio galaxies at z < 0.3 with MUSE observations

Giovanna Speranza (IAC); Balmaverde, Barbara; Capetti, Alessandro; Massaro, Francesco; Tremblay, G.; Marconi, Alessandro; Venturi, Giacomo; Chiaberge, M.; Baldi, R. D.; Baum, S.; Grandi, P.; Meyer, Eileen T.; 0’Dea, C.; Sparks, W.; Terrazas, B. A.; Torresi, E.

Astronomy & Astrophysics, Volume 653, September 2021 https://www.aanda.org/articles/aa/abs/2021/09/aa40686-21/aa40686-21.html

ABSTRACT: We analyze VLT/MUSE observations of 37 radio galaxies from the Third Cambridge catalogue (3C) with redshift < 0.3 searching for nuclear outflows of ionized gas. These observations are part of the MURALES project (a MUse RAdio Loud Emission line Snapshot survey), whose main goal is to explore the feedback process in the most powerful radio-loud AGN. We applied a nonparametric analysis to the [O III] λ5007 emission line, whose asymmetries and high-velocity wings reveal signatures of outflows. We find evidence of nuclear outflows in 21 sources, with velocities between ∼400 and 1000 km s−1, outflowing masses of ∼105 − 107M, and a kinetic energy in the range ∼1053 − 1056 erg. In addition, evidence for extended outflows is found in the 2D gas velocity maps of 13 sources of the subclasses of high-excitation (HEG) and broad-line (BLO) radio galaxies, with sizes between 0.4 and 20 kpc. We estimate a mass outflow rate in the range 0.4–30 M yr−1 and an energy deposition rate of Ėkin ∼ 1042 − 1045 erg s−1. Comparing the jet power, the nuclear luminosity of the active galactic nucleus, and the outflow kinetic energy rate, we find that outflows of HEGs and BLOs are likely radiatively powered, while jets likely only play a dominant role in galaxies with low excitation. The low loading factors we measured suggest that these outflows are driven by momentum and not by energy. Based on the gas masses, velocities, and energetics involved, we conclude that the observed ionized outflows have a limited effect on the gas content or the star formation in the host. In order to obtain a complete view of the feedback process, observations exploring the complex multiphase structure of outflows are required.

A multiwavelength-motivated X-ray model for the Circinus Galaxy

Carolina Andonie (Durham), Claudio Ricci, Stéphane Paltani, Patricia Arévalo, Ezequiel Treister, Franz Bauer, Marko Stalevski

Monthly Notices of the Royal Astronomical Society, Volume 511, Issue 4, April 2022, Pages 5768–5781  https://doi.org/10.1093/mnras/stac403

ABSTRACT: Reprocessed X-ray emission in Active Galactic Nuclei (AGN) can provide fundamental information about the circumnuclear environments of supermassive black holes. Recent mid-infrared studies have shown evidence of an extended dusty structure perpendicular to the torus plane. In this work, we build a self-consistent X-ray model for the Circinus Galaxy including the different physical components observed at different wavelengths and needed to reproduce both the morphological and spectral properties of this object in the mid-infrared. The model consists of four components: the accretion disk, the broad line region (BLR), a flared disk in the equatorial plane and a hollow cone in the polar direction. Our final model reproduces well the 3–70 keV Chandra and NuSTAR spectra of Circinus, including the complex Fe Kα zone and the spectral curvature, although several additional Gaussian lines, associated to either ionized iron or to broadened Fe Kα/Kβ lines, are needed. We find that the flared disk is Compton thick (NH,d=1.01+0.03−0.24×1025cm−2) and geometrically thick (CF=0.55+0.01−0.05), and that the hollow cone has a Compton-thin column density (NH,c=2.18+0.47−0.43×1023cm−2), which is consistent with the values inferred by mid-infrared studies. Including also the BLR, the effective line of sight column density is NH=1.47+0.03−0.24×1025cm−2. This approach to X-ray modelling, i.e. including all the different reprocessing structures, will be very important to fully exploit data from future X-ray missions.

Localizing narrow Fe Kα emission within bright AGN

Carolina Andonie (Durham), Franz E. Bauer, Rosamaria Carraro, Patricia Arévalo, David M. Alexander, William N. Brandt, Johannes Buchner, Adam He, Michael J. Koss, Claudio Ricci, Vicente Salinas, Manuel Solimano, Alessia Tortosa, and Ezequiel Treister

Astronomy & Astrophysics, Volume 664, August 2022, Article Number A46, August 2022   https://doi.org/10.1051/0004-6361/202142473

ABSTRACT: The 6.4 keV Fe Kα emission line is a ubiquitous feature in X-ray spectra of active galactic nuclei (AGN), and its properties track the interaction between the variable primary X-ray continuum and the surrounding structure from which it arises. Aims. We clarify the nature and origin of the narrow Fe Kα emission using X-ray spectral, timing, and imaging constraints, plus possible correlations to AGN and host galaxy properties, for 38 bright nearby AGN (z < 0.5) from the Burst Alert Telescope AGN Spectroscopic Survey. Methods. Modeling Chandra and XMM-Newton spectra, we computed line full-width half-maxima (FWHMs) and constructed Fe Kα line and 2–10 keV continuum light curves. The FWHM provides one estimate of the Fe Kα emitting region size, RFeKα, assuming virial motion. A second estimate comes from comparing the degree of correlation between the variability of the continuum and line-only light curves, compared to simulated light curves. Finally, we extracted Chandra radial profiles to place upper limits on RFeKα. Results. For 90% (21/24) of AGN with FWHM measurements, RFeKα is smaller than the fiducial dust sublimation radius, Rsub. From timing analysis, 37 and 18 AGN show significant continuum and Fe Kα variability, respectively. Despite a wide range of variability properties, the constraints on the Fe Kα photon reprocessor size independently confirm that RFeKα is smaller than Rsub in 83% of AGN. Finally, the imaging analysis yields loose upper limits for all but two sources; notably, the Circinus Galaxy and NGC 1068 show significant but subdominant extended Fe Kα emission out to ∼100 and ∼800 pc, respectively. Conclusions. Based on independent constraints, we conclude that the majority of the narrow Fe Kα emission in typical AGN predominantly arises from regions smaller than and presumably inside Rsub, and thus it is associated either with the outer broad line region or outer accretion disk. However, the large diversity of continuum and narrow Fe Kα variability properties are not easily accommodated by a universal scenario.

A panchromatic view of infrared quasars: excess star formation and radio emission in the most heavily obscured systems

Carolina Andonie (Durham), David M Alexander, David Rosario, Brivael Laloux, Antonis Georgakakis, Leah K Morabito, Carolin Villforth, Mathilda Avirett-Mackenzie, Gabriela Calistro Rivera, Agnese Del Moro, Sotiria Fotopoulou, Chris Harrison, Andrea Lapi, James Petley, Grayson Petter, Francesco Shankar

Monthly Notices of the Royal Astronomical Society, Volume 517, Issue 2, December 2022, Pages 2577–2598  https://doi.org/10.1093/mnras/stac2800

ABSTRACT: To understand the active galactic nuclei (AGNs) phenomenon and their impact on the evolution of galaxies, a complete AGN census is required; however, finding heavily obscured AGNs is observationally challenging. Here we use the deep and extensive multiwavelength data in the COSMOS field to select a complete sample of 578 infrared (IR) quasars (LAGN,IR>1045ergs−1LAGN,IR>1045ergs−1) at z < 3, with minimal obscuration bias, using detailed UV-to-far-IR spectral energy distribution (SED) fitting. We complement our SED constraints with X-ray and radio observations to further investigate the properties of the sample. Overall, 322 of the IR quasars are detected by Chandra and have individual X-ray spectral constraints. From a combination of X-ray stacking and L2−10kevL2−10kev – L6μmL6μm analyses, we show that the majority of the X-ray faint and undetected quasars are heavily obscured (many are likely Compton thick), highlighting the effectiveness of the mid-IR band to find obscured AGNs. We find that 355 (≍61 per cent) IR quasars are obscured (NH>1022cm−2NH>1022cm−2) and identify differences in the average properties between the obscured and unobscured quasars: (1) obscured quasars have star formation rates ≍3 times higher than unobscured systems for no significant difference in stellar mass and (2) obscured quasars have stronger radio emission than unobscured systems, with a radio-loudness parameter ≈0.2dex≈0.2dex higher. These results are inconsistent with a simple orientation model but in general agreement with either extreme host-galaxy obscuration towards the obscured quasars or a scenario where obscured quasars are an early phase in the evolution of quasars.