Starbursting to Quenching: the role of X-ray emission

in Active Galactic Nuclei feedback processes

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The work described in this thesis was undertaken between October 2013 and October 2016 under the supervision of Dr. Marcella Brusa, at the Department of Physics and Astronomy, Alma Mater Studiorum - Università di Bologna.

The research has been funded by the FP7/CIG grant, "eEASY": `SMBH evolution through cosmic time: from current surveys to eROSITA and Euclid AGN Synergies' (No 321913)

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ABSTRACT

One of the most debated topics of modern extragalactic astrophysics is the co-evolution between the supermassive black holes (SMBHs) sitting in the nuclei of the galaxies and their hosts. Ac- cording to the most popular models of Active Galactic Nuclei (AGN) and galaxies co-evolution, starburst galaxies, unobscured quasars and inactive (and quenched) galaxies represent the dif- ferent phases of an evolutionary sequence reproducing the most massive galaxies observed in the Universe. In this context, gas flows in the form of energetic outflows are postulated to play a pivotal role in this process, given that they regulate both accretion and ejection of material onto and from the SMBH and can propagate momentum and energy over a wide spatial scale, acting on the fuel from which new stars form and stopping the host galaxy growth.

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In order to validate this binding nature between the central SMBH and the host galaxy, we investigate the kinematic and physical properties of ionized and atomic gas components of the interstellar medium of well selected AGN-galaxy systems, obtained from ultraviolet, optical, near-infrared spectroscopic analysis, to unveil the presence of outflows. In particular, we propose and test different selection criteria to isolate sources at z ~ 2 in the predicted feedback phase, starting from multiwavelength information collected in the COSMOS field. As a complementary approach, we also collect a large sample of X-ray selected AGNs at z < 0.8 from the SDSS database to unveil the incidence of outflows and prove the crucial role of X-ray observations for the investigation of the feedback phase.

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The dynamical conditions of the ionised outflows for the high-z samples, for which slit- resolved spectroscopy and/or integral Field spectroscopic (IFS) data are available, are studied in detail through the combination of multicomponent and non-parametric line fitting algorithms. We report the unambiguous presence of fast, massive outflows in 4 obscured QSOs, extending up to 10 kpc in the host galaxy and with profound effects on the host galaxy.

 

We carefully discuss the uncertainties related to the assumption of the plasma conditions in the estimate of the outflows properties and we report, for the first time, the plasma electron density and temperature in a mid-size sample of AGNs.

 

Finally, we combine the ionised/neutral gas kinematic and physical conditions with SMBH accretion and host galaxy properties, recovered from multiwavelength spectral energy distribution analysis and X-ray spectroscopic investigation, to infer the general conditions regulating the feedback processes. We also discuss our results in the context of recent observational and theoretical clues.

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Portion of the work presented in this thesis appeared in the following papers: 

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– Perna M., Lanzuisi G., Brusa M., et al., 2017, A&A, 574A, 82P 

   An X-ray/SDSS sample (I): Multi-phase outflow incidence and dependence on AGN luminosity

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– Perna M.,  Lanzuisi G. et al., 2017, A&A, 606, 96

   An X-ray/SDSS sample (II): outflowing gas plasma properties

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– Perna M.,  Brusa M. et al., 2015, A&A, 574, 82

   Galaxy wide outflows in z ~ 1.5 luminous obscured QSOs revealed through NIR slit-resolved spectroscopy

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– Perna M.,  Brusa M. et al., 2015, A&A, 583, A77

   SINFONI spectra of heavily obscured AGNs in COSMOS: evidence of outflows in a MIR/O target at z ~ 2.5

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– Brusa M., Perna M., et al., 2016, A&A, 588A, 58 

   A fast ionised wind in a star-forming quasar system at z ~ 1.5 resolved through adaptive optics assisted near-infrared data

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– Brusa M., Bongiorno A., Cresci G., Perna M., et al., 2015, MNRAS, 446, 2394

   X-shooter reveals powerful outflows in z ~ 1.5 X-ray selected obscured QSOs 

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– Cresci G., Mainieri V., Brusa M., Marconi A., Perna M., et al., 2015, ApJ, 799, 81

   Blowin' in the wind: both 'negative' and 'positive' feedback in an obscured high-z QSO

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– Brusa M., Feruglio C., Cresci G., Mainieri V., Sargent M.T., Perna M., et al., 2015, A&A, 578, 11

   Evidence for feedback in action from the molecular gas content in the z ~ 1.6 outflowing QSO XID2028

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