Early Stage Researchers – 1st Authorship

Six more papers have been submitted and are awaiting publication.

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A post-merger enhancement only in star-forming Type 2 Seyfert galaxies: the deep learning view

M S Avirett-Mackenzie (UBATH), C Villforth, M Huertas-Company, S Wuyts, D M Alexander, S Bonoli, A Lapi, I E Lopez, C Ramos Almeida, F Shankar

Monthly Notices of the Royal Astronomical Society, Volume 528, Issue 4, March 2024, Pages 6915–693, https://doi.org/10.1093/mnras/stae183

ABSTRACT: Supermassive black holes require a reservoir of cold gas at the centre of their host galaxy in order to accrete and shine as active galactic nuclei (AGN). Major mergers have the ability to drive gas rapidly inwards, but observations trying to link mergers with AGN have found mixed results due to the difficulty of consistently identifying galaxy mergers in surveys. This study applies deep learning to this problem, using convolutional neural networks trained to identify simulated post-merger galaxies from survey-realistic imaging. This provides a fast and repeatable alternative to human visual inspection. Using this tool, we examine a sample of ∼8500 Seyfert 2 galaxies (L[O III] ∼ 1038.5−42 erg s−1) at z < 0.3 in the Sloan Digital Sky Survey and find a merger fraction of 2.19+0.21 −0.17 per cent compared with inactive control galaxies, in which we find a merger fraction of 2.96+0.26 −0.20 per cent, indicating an overall lack of mergers among AGN hosts compared with controls. However, matching the controls to the AGN hosts in stellar mass and star formation rate reveals that AGN hosts in the star-forming blue cloud exhibit a ∼2 × merger enhancement over controls, while those in the quiescent red sequence have significantly lower relative merger fractions, leading to the observed overall deficit due to the differing M∗–SFR distributions. We conclude that while mergers are not the dominant trigger of all low-luminosity, obscured AGN activity in the nearby Universe, they are more important to AGN fuelling in galaxies with higher cold gas mass fractions as traced through star formation.

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Probing the roles of orientation and multi-scale gas distributions in shaping the obscuration of Active Galactic Nuclei through cosmic time

Alba V Alonso-Tetilla (SOTON), Francesco Shankar, Fabio Fontanot, Nicola Menci, Milena Valentini, Johannes Buchner, Brivael Laloux, Andrea Lapi, Annagrazia Puglisi, David M Alexander, Viola Allevato, Carolina Andonie, Silvia Bonoli, Michaela Hirschmann, Iván E López, Sandra I Raimundo, Cristina Ramos Almeida

Monthly Notices of the Royal Astronomical Society, Volume 527, Issue 4, February 2024, Pages 10878–10896, https://doi.org/10.1093/mnras/stad3265

Abstract: The origin of obscuration in active galactic nuclei (AGNs) is still an open debate. In particular, it is unclear what drives the relative contributions to the line-of-sight column densities from galaxy-scale and torus-linked obscuration. The latter source is expected to play a significant role in Unification Models, while the former is thought to be relevant in both Unification and Evolutionary models. In this work, we make use of a combination of cosmological semi-analytic models and semi-empirical prescriptions for the properties of galaxies and AGN, to study AGN obscuration. We consider a detailed object-by-object modelling of AGN evolution, including different AGN light curves (LCs), gas density profiles, and also AGN feedback-induced gas cavities. Irrespective of our assumptions on specific AGN LC or galaxy gas fractions, we find that, on the strict assumption of an exponential profile for the gas component, galaxy-scale obscuration alone can hardly reproduce the fraction of log (NH/cm−2) ≥ 24 sources at least at z 3. This requires an additional torus component with a thickness that decreases with luminosity to match the data. The torus should be present in all evolutionary stages of a visible AGN to be effective, although galaxy-scale gas obscuration may be sufficient to reproduce the obscured fraction with 22 < log (NH/cm−2) < 24 (Compton-thin, CTN) if we assume extremely compact gas disc components. The claimed drop of CTN fractions with increasing luminosity does not appear to be a consequence of AGN feedback, but rather of gas reservoirs becoming more compact with decreasing stellar mass.

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Multi-phase characterization of AGN winds in 5 local type-2 quasars

G. Speranza (IAC), C. Ramos Almeida, J. A. Acosta-Pulido, A. Audibert, L. R. Holden, C. N. Tadhunter, A. Lapi, O. González-Martín, M. Brusa, I. E. López, B. Musiimenta, and F. Shankar

Astronomy and Astrophysics, Volume 681, January 2024, Article 63 https://doi.org/10.1051/0004-6361/202347715

ABSTRACT: We present MEGARA integral field unit (IFU) observations of five local type-2 quasars (QSO2s, z ∼ 0.1) from the Quasar Feedback (QSOFEED) sample. These active galactic nuclei (AGN) have bolometric luminosities of 1045.5−46 erg s−1 and stellar masses of ∼1011 M. The LR-V grating of MEGARA allows us to explore the kinematics of the ionized gas through the [O III]λ5007 Å emission line. The nuclear spectra of the five QSO2s, extracted in a circular aperture of ∼1.2” (∼2.2 kpc) in diameter, matching the resolution of these seeing-limited observations, show signatures of high velocity winds in the form of broad (full width at half maximum, 1300 ≤ FWHM ≤ 2240 km s−1) and blueshifted components. We found that four out of the five QSO2s present outflows that we canresolve with our seeing-limited data, and they have radii ranging from 3.1 to 12.6 kpc. In the case of the two QSO2s with extended radio emission, we found that it is well aligned with the outflows, suggesting that low-power jets might be compressing and accelerating the ionized gas in these radio-quiet QSO2s. In the four QSO2s with spatially resolved outflows, we measured ionized mass outflow rates of 3.3–6.5 M yr−1 when we used [S II]-based densities, and of 0.7–1.6 M yr−1 when trans-auroral line-based densities were considered instead. We compared them with the corresponding molecular mass outflow rates (8–16 M yr−1), derived from CO(2–1) ALMA observations at 0.200 resolution. The cold molecular outflows carry more mass than their ionized counterparts. However, both phases show lower outflow mass rates than those expected from observational scaling relations where uniform assumptions on the outflow properties were adopted. This might be indicating that the AGN luminosity is not the only driver of massive outflows and/or that these relations need to be rescaled using accurate outflow properties (i.e., electron density and radius). We did not find a significant impact of the outflows on the global star formation rates when considering the energy budget of the molecular and ionized outflows together. However, spatially resolved measurements of recent star formation in these targets are needed in order to evaluate this fairly, considering the dynamical timescales of the outflows, of 3–20 Myr for the ionized gas and 1–10 Myr for the molecular gas.

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A new discovery space opened by eROSITA: Ionised AGN outflows from X-ray selected samples

B. Musiimenta (UNIBO), M. Brusa, T. Liu, M. Salvato, J. Buchner, Z. Igo, S. G. H. Waddell, Y. Toba, R. Arcodia, J. Comparat, D. Alexander, F. Shankar, A. Lapi, C. Ramos Almeida, A. Georgakakis, A. Merloni, T. Urrutia, J. Li, Y. Terashima, Y. Shen, Q. Wu, T. Dwelly, K. Nandra and J. Wolf

Astronomy and Astrophysics, Volume 679, November 2023, Article 84 https://doi.org/10.1051/0004-6361/202245555

ABSTRACT: Context. In the context of an evolutionary model, the outflow phase of an active galactic nucleus (AGN) occurs at the peak of its activity, once the central supermassive black hole (SMBH) is massive enough to generate sufficient power to counterbalance the potential well of the host galaxy. This outflow feedback phase plays a vital role in galaxy evolution. Aims. Our aim in this paper is to apply various selection methods to isolate powerful AGNs in the feedback phase, trace and characterise outflows in these AGNs, and explore the link between AGN luminosity and outflow properties. Methods. We applied a combination of methods to the Spectrum Roentgen Gamma (SRG) eROSITA Final Equatorial Depth survey (eFEDS) catalogue and isolated ∼1400 candidates at z > 0.5 out of ∼11 750 AGNs (∼12%). Furthermore, we narrowed down our selection to 427 sources that have 0.5 < z < 1. We tested the robustness of our selection on the small subsample of 50 sources with available good quality SDSS spectra at 0.5 < z < 1 and, for which we fitted the [OIII] emission line complex and searched for the presence of ionised gas outflow signatures. Results. Out of the 50 good quality SDSS spectra, we identified 23 quasars (∼45%) with evidence of ionised outflows based on the presence of significant broad and/or shifted components in [OIII]λ5007 Å. They are on average more luminous (log Lbol ∼ 45.2 erg s−1) and more obscured (NH ∼ 1022 cm−2) than the parent sample of ∼427 candidates, although this may be ascribed to selection effects affecting the good quality SDSS spectra sample. By adding 118 quasars at 0.5 < z < 3.5 with evidence of outflows reported in the literature, we find a weak correlation between the maximum outflow velocity and the AGN bolometric luminosity. On the contrary, we recovered strong correlations between the mass outflow rate and outflow kinetic power with the AGN bolometric luminosity. Conclusions. About 30% of our sample have kinetic coupling efficiencies, E˙/Lbol > 1%, suggesting that the outflows could have a significant effect on their host galaxies. We find that the majority of the outflows have momentum flux ratios lower than 20 which rules out an energy-conserving nature. Our present work points to the unequivocal existence of a rather short AGN outflow phase, paving the way towards a new avenue to dissect AGN outflows in large samples within eROSITA and beyond.

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A thermal–kinetic subgrid model for supernova feedback in simulations of galaxy formation

Evgenii Chaikin (ULEI), Joop Schaye, Matthieu Schaller, Alejandro Benítez-Llambay, Folkert S J Nobels, Sylvia Ploeckinger

Monthly Notices of the Royal Astronomical Society, Volume 523, Issue 3, August 2023, Pages 3709–3731 https://doi.org/10.1093/mnras/stad1626

ABSTRACT: We present a subgrid model for supernova feedback designed for cosmological simulations of galaxy formation that may include a cold interstellar medium (ISM). The model uses thermal and kinetic channels of energy injection, which are built upon the stochastic kinetic and thermal models for stellar feedback used in the OWLS and EAGLE simulations, respectively. In the thermal channel, the energy is distributed statistically isotropically and injected stochastically in large amounts per event, which minimizes spurious radiative energy losses. In the kinetic channel, we inject the energy in small portions by kicking gas particles in pairs in opposite directions. The implementation of kinetic feedback is designed to conserve energy, linear and angular momentum, and is statistically isotropic. To test the model, we run simulations of isolated Milky Way-mass and dwarf galaxies, in which the gas is allowed to cool down to 10 K. Using the thermal and kinetic channels together, we obtain smooth star formation histories and powerful galactic winds with realistic mass loading factors. Furthermore, the model produces spatially resolved star formation rates (SFRs) and velocity dispersions that are in agreement with observations. We vary the numerical resolution by several orders of magnitude and find excellent convergence of the global SFRs and wind mass loading. We show that large thermal energy injections generate a hot phase of the ISM and modulate the star formation by ejecting gas from the disc, while the low-energy kicks increase the turbulent velocity dispersion in the neutral ISM, which in turn helps suppress star formation.

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The miniJPAS survey: AGN & host galaxy co-evolution of X-ray selected sources

E. López (UNIBO), M. Brusa, S. Bonoli, F. Shankar, N. Acharya, B.Laloux, K. Dolag, A. Georgakakis, A. Lapi, C. Ramos Almeida, M. Salvato, J. Chaves-Montero, P. Coelho, L. A. Díaz-García, J. A. Fernández-Ontiveros, A. Hernán-Caballero, R. M. González Delgado, I. Marquez, M. Pović, R. Soria, C. Queiroz, P. T. Rahna, R. Abramo, J. Alcaniz, N. Benitez, S. Carneiro, J. Cenarro, D. Cristóbal-Hornillos, R. Dupke, A. Ederoclite, C. López-Sanjuan, A. Marín-Franch, C. Mendes de Oliveira, M. Moles, L. Sodré Jr, K. Taylor, J. Varela, H. V. Ramió

Astronomy and Astrophysics, Volume 672, April 2023, Article137 https://doi.org/10.1051/0004-6361/202245168

ABSTRACT: Studies indicate strong evidence of a scaling relation in the local Universe between the supermassive black hole mass (M_BH) and the stellar mass of their host galaxies (M_*). They even show similar histories across cosmic times of their differential terms: star formation rate (SFR) and black hole accretion rate (BHAR). However, a clear picture of this coevolution is far from being understood.

We select an X-ray sample of active galactic nuclei (AGN) up to z = 2.5 in the miniJPAS footprint. Their X-ray to infrared spectral energy distributions (SEDs) have been modeled with the CIGALE code, constraining the emission to 68 bands, from which 54 are the narrow filters from the miniJPAS survey. For a final sample of 308 galaxies, we derive their physical properties, like their M_*, SFR, star formation history, and the luminosity produced by the accretion process of the central BH (L_AGN). For a subsample of 113 sources, we also fit their optical spectra to obtain the gas velocity dispersion from the broad emission lines and estimate the M_BH. We calculate the BHAR in physical units depending on two radiative efficiency regimes. We find that the Eddington ratios and its popular proxy (L_X/M_*) have, on average, 0.6 dex of difference, and a KS-test indicates that they come from different distributions. Our sources exhibit a considerable scatter on the M_BH–M_* scaling relation, and this can explain the difference between the Eddington ratios and its proxy.

We also model three evolution scenarios for each source to recover the integral properties at z = 0. Using the SFR and BHAR, we show a notable diminution in the scattering between M_BH–M_*. For the last scenario, we consider the SFH and a simple energy budget for the AGN accretion, and we retrieve a relation similar to the calibrations known for the local Universe.

Our study covers ∼1 deg² in the sky and is sensitive to biases in luminosity. Nevertheless, we show that, for bright sources, the link between the differential values (SFR and BHAR) and their decoupling based on an energy limit is the key that leads to the local M_BH–M_* scaling relation. In the future, we plan to extend this methodology to thousand degrees of the sky using JPAS with an X-ray selection from eROSITA, to obtain an unbiased distribution of BHAR and Eddington ratios.

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Cosmic evolution of the incidence of active galactic nuclei in massive clusters: simulations versus observations

Iván Muñoz Rodríguez (NOA), Antonis Georgakakis, Francesco Shankar, Viola Allevato, Silvia Bonoli, Marcella Brusa, Andrea Lapi and Akke Viitanen

Monthly Notices of the Royal Astronomical Society, Volume 518, Issue 1, January 2023, Pages 1041–1056 https://doi.org/10.1093/mnras/stac3114

ABSTRACT: This paper explores the role of small-scale environment (<1 Mpc) in modulating accretion events on to supermassive black holes by studying the incidence of active galactic nuclei (AGNs) in massive clusters of galaxies. A flexible, data-driven semi-empirical model is developed based on a minimal set of parameters and under the zero-order assumption that the incidence of AGNs in galaxies is independent of environment. This is used to predict how the fraction of X-ray selected AGN among galaxies in massive dark matter haloes (≳ 3 × 10¹⁴ M_⊙) evolves with redshift and reveal tensions with observations. At high redshift, z ∼ 1.2, the model underpredicts AGN fractions, particularly at high X-ray luminosities, L_X (2-10 keV) ≳ 10⁴⁴ erg s^−1.. At low redshift, z ∼ 0.2, the model estimates fractions of moderate luminosity AGN (L_X(2-10 keV) ≳ 10⁴³ erg s⁻¹) that are a factor of 2-3 higher than the observations. These findings reject the zero-order assumption on which the semi-empirical model hinges and point to a strong and redshift-dependent influence of the small-scale environment on the growth of black holes. Cluster of galaxies appear to promote AGN activity relative to the model expectation at z ∼ 1.2 and suppress it close to the present day. These trends could be explained by the increasing gas content of galaxies towards higher redshift combined with an efficient triggering of AGNs at earlier times in galaxies that fall on to clusters

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The demographics of obscured AGN from X-ray spectroscopy guided by multiwavelength information 

Brivael Laloux (NOA), Antonis Georgakakis, Carolina Andonie, David M Alexander, Angel Ruiz, David J Rosario, James Aird, Johannes Buchner, Francisco J Carrera, Andrea Lapi, Cristina Ramos Almeida, Mara Salvato, Francesco Shankar

Monthly Notices of the Royal Astronomical Society, Volume 518, Issue 2, January 2023, Pages 2546–2566, https://doi.org/10.1093/mnras/stac3255

ABSTRACT: A complete census of Active Galactic Nuclei (AGN) is a prerequisite for understanding the growth of supermassive black holes across cosmic time. A significant challenge toward this goal is the whereabouts of heavily obscured AGN that remain uncertain. This paper sets new constraints on the demographics of this population by developing a methodology that combines X-ray spectral information with priors derived from multiwavelength observations. We select X-ray AGN in the Chandra COSMOS Legacy survey and fit their 2.2-500µm spectral energy distributions with galaxy and AGN templates to determine the mid-infrared (6µm) luminosity of the AGN component. Empirical correlations between X-ray and 6µm luminosities are then adopted to infer the intrinsic accretion luminosity at X-rays for individual AGN. This is used as prior information in our Bayesian X-ray spectral analysis to estimate physical properties, such as line-of-sight obscuration. Our approach breaks the degeneracies between accretion luminosity and obscuration that affect X-ray spectral analysis, particularly for the most heavily obscured (Compton-Thick) AGN with low photon counts X-ray spectra. The X-ray spectral results are then combined with the selection function of the Chandra COSMOS Legacy survey to derive the AGN space density and a Compton-Thick fraction of 21.0^+16.1_-9.9% at redshifts 𝑧<05. At higher redshift, our analysis suggests upper limits to the Compton-Thick AGN fraction of ≤40%. These estimates are at the low end of the range of values determined in the literature and underline the importance of multiwavelength approaches for tackling the challenge of heavily obscured AGN demographics.

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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.

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Testing the key role of the stellar mass-halo mass relation in galaxy merger rates and morphologies via DECODE, a novel Discrete statistical sEmi-empiriCal mODEl

Hao Fu (SOTON), Francesco Shankar, Mohammadreza Ayromlou, Max Dickson, Ioanna Koutsouridou, Yetli Rosas-Guevara, Christopher Marsden, Kristina Brocklebank, Mariangela Bernardi, Nikolaos Shiamtanis, Joseph Williams, Lorenzo Zanisi, Viola Allevato, Lumen Boco, Silvia Bonoli, Andrea Cattaneo, Paola Dimauro, Fangzhou Jiang, Andrea Lapi, Nicola Menci, Stefani Petropoulou and Carolin Villforth

Monthly Notices of the Royal Astronomical Society, Volume 516, Issue 3, November 2022, Pages 3206–3233  https://doi.org/10.1093/mnras/stac2205

ABSTRACT: The relative roles of mergers and star formation in regulating galaxy growth are still a matter of intense debate. We here present our DECODE, a new Discrete statistical sEmi-empiriCal mODEl specifically designed to predict rapidly and efficiently, in a full cosmological context, galaxy assembly, and merger histories for any given input stellar mass–halo mass (SMHM) relation. DECODE generates object-by-object dark matter merger trees (hence discrete) from accurate subhalo mass and infall redshift probability functions (hence statistical) for all subhaloes, including those residing within other subhaloes, with virtually no resolution limits on mass or volume. Merger trees are then converted into galaxy assembly histories via an input, redshift- dependent SMHM relation, which is highly sensitive to the significant systematics in the galaxy stellar mass function and on its evolution with cosmic time. DECODE can accurately reproduce the predicted mean galaxy merger rates and assembly histories of hydrodynamic simulations and semi-analytical models, when adopting in input their SMHM relations. In this work, we use DECODE to prove that only SMHM relations implied by stellar mass functions characterized by large abundances of massive galaxies and significant redshift evolution, at least at M⋆ ≳ 10¹¹ M_⊙, can simultaneously reproduce the local abundances of satellite galaxies, the galaxy (major merger) pairs since 𝑧 ∼ 3, and the growth of Brightest Cluster Galaxies. The same models can also reproduce the local fraction of elliptical galaxies, on the assumption that these are strictly formed by major mergers, but not the full bulge-to-disc ratio distributions, which require additional processes.

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Warm molecular and ionized gas kinematics in the type-2 quasar J0945+1737

G. Speranza (IAC), C. Ramos Almeida, J. A. Acosta-Pulido, R. A. Riffel, C. Tadhunter, J. C. S. Pierce, A. Rodríguez-Ardila, M. Coloma Puga, M. Brusa, B. Musiimenta, D. M. Alexander, A. Lapi, F. Shankar, C. Villforth

Astronomy and Astrophysics Volume 665, Article No A55, September 2022. https://doi.org/10.1051/0004-6361/202243585

ABSTRACT: We analyse Near-Infrared Integral Field Spectrograph (NIFS) observations of the type-2 quasar (QSO2) SDSS J094521.33+173753.2 to investigate its warm molecular and ionized gas kinematics. This QSO2 has a bolometric luminosity of 10^45.7 erg s⁻¹ and a redshift of z = 0.128. The K-band spectra provided by NIFS cover a range of 1.99–2.40 µm where low ionization (Paα and Brδ), high ionization ([S XI]λ1.920 µm and [Si VI]λ1.963 µm), and warm molecular lines (from H₂1-0S(5) to 1-0S(1)) are detected, allowing us to study the multi-phase gas kinematics. Our analysis reveals gas in ordinary rotation in all the emission lines detected and also outflowing gas in the case of the low and high ionization emission lines. In the case of the nuclear spectrum, which corresponds to a circular aperture of 0.3” (686 pc) in diameter, the warm molecular lines can be characterized using a single Gaussian component of full width at half maximum (FWHM) = 350−400 km s⁻¹, while Paα, Brδ, and [Si VI] are best fitted with two blue-shifted Gaussian components of FWHM ∼ 800 and 1700 km s⁻¹, in addition to a narrow component of ∼300 km s⁻¹. We interpret the blue-shifted broad components as outflowing gas, which reaches the highest velocities, of up to −840 km s⁻¹, in the south-east direction (PA ∼ 125°), extending up to a distance of ∼3.4 kpc from the nucleus. The ionized outflow has a maximum mass outflow rate of Ṁ_out,max = 42–51 M yr⁻¹, and its kinetic power represents 0.1% of the quasar bolometric luminosity. Very Large Array (VLA) data of J0945 show extended radio emission (PA ∼ 100°) that is aligned with the clumpy emission traced by the narrow component of the ionized lines up to scales of several kiloparsecs, and with the innermost part of the outflow (central ∼0.4” = 915 pc). Beyond that radius, at the edge of the radio jet, the high velocity gas shows a different PA of ∼125°. This might be an indication that the line-emitting gas is being compressed and accelerated by the shocks generated by the radio jet.

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The Black Hole Mass Function across Cosmic Time. II. Heavy Seeds and (Super)Massive Black Holes

Alex Sicilia (SISSA), Andrea Lapi, Lumen Boco, Francesco Shankar, David M Alexander, Viola Allevato, Carolin Villforth, Marcella Massardi, Mario Spera, Alessandro Bressan, Luigi Danese

The Astrophysical Journal, Volume 934, Issue 1, July 2022, https://doi.org/10.3847/1538-4357/ac7873

The importance of the way in which supernova energy is distributed around young stellar populations in simulations of galaxies

Evgenii Chaikin (ULEI); Joop Schaye; Matthieu Schaller; Yannick M Bahé; Folkert S J Nobels; Sylvia Ploeckinger

Monthly Notices of the Royal Astronomical Society, Volume 514, Issue 1, July 2022, Pages 249–264, https://doi.org/10.1093/mnras/stac1132

ABSTRACT: Supernova (SN) feedback plays a crucial role in simulations of galaxy formation. Because blast waves from individual SNe occur on scales that remain unresolved in modern cosmological simulations, SN feedback must be implemented as a subgrid model. Differences in the manner in which SN energy is coupled to the local interstellar medium and in which excessive radiative losses are prevented have resulted in a zoo of models used by different groups. However, the importance of the selection of resolution elements around young stellar particles for SN feedback has largely been overlooked. In this work, we examine various selection methods using the smoothed particle hydrodynamics code SWIFT. We run a suite of isolated disc galaxy simulations of a Milky Way-mass galaxy and small cosmological volumes, all with the thermal stochastic SN feedback model used in the EAGLE simulations. We complement the original mass-weighted neighbour selection with a novel algorithm guaranteeing that the SN energy distribution is as close to isotropic as possible. Additionally, we consider algorithms where the energy is injected into the closest, least dense, or most dense neighbour. We show that different neighbour-selection strategies cause significant variations in star formation rates, gas densities, wind mass-loading factors, and galaxy morphology. The isotropic method results in more efficient feedback than the conventional mass-weighted selection. We conclude that the manner in which the feedback energy is distributed among the resolution elements surrounding a feedback event is as important as changing the amount of energy by factors of a few.

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Simulations of ⁶⁰FE entrained in ejecta from a near-Earth supernova: effects of observer motion

Evgenii Chaikin (ULEI), Alexander A Kaurov, Brian D Fields and Camila A Correa

Monthly Notices of the Royal Astronomical Society, Volume 512, Issue 1, May 2022, Pages 712–727, https://doi.org/10.1093/mnras/stac327

ABSTRACT: Recent studies have shown that live (not decayed) radioactive ⁶⁰Fe is present in deep-ocean samples, Antarctic snow, lunar regolith, and cosmic rays. ⁶⁰Fe represents supernova (SN) ejecta deposited in the Solar system around 3Myr3Myr ago, and recently an earlier pulse ≈7 Myr≈7 Myr ago has been found. These data point to one or multiple near-Earth SN explosions that presumably participated in the formation of the Local Bubble. We explore this theory using 3D high-resolution smooth-particle hydrodynamical simulations of isolated SNe with ejecta tracers in a uniform interstellar medium (ISM). The simulation allows us to trace the SN ejecta in gas form and those eject in dust grains that are entrained with the gas. We consider two cases of diffused ejecta: when the ejecta are well-mixed in the shock and when they are not. In the latter case, we find that these ejecta remain far behind the forward shock, limiting the distance to which entrained ejecta can be delivered to ≈100 pc in an ISM with nH=0.1cm−3nH=0.1cm−3 mean hydrogen density. We show that the intensity and the duration of ⁶⁰Fe accretion depend on the ISM density and the trajectory of the Solar system. Furthermore, we show the possibility of reproducing the two observed peaks in ⁶⁰Fe concentration with this model by assuming two linear trajectories for the Solar system with 30-km s⁻¹ velocity. The fact that we can reproduce the two observed peaks further supports the theory that the ⁶⁰Fe signal was originated from near-Earth SNe.

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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 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 disc, the broad-line region (BLR), a flared disc 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 with either ionized iron or broadened Fe Kα/Kβ lines, are needed. We find that the flared disc is Compton-thick (NH,d = 1.01+0.03 −0.24 × 1025 cm−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 × 1023 cm−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 × 1025 cm−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.

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The Black Hole Mass Function Across Cosmic Times I. Stellar Black Holes and Light Seed Distribution

Alex Sicilia (SISSA), Andrea Lapi, Lumen Boco, Mario Spera, Ugo N. Di Carlo, Michela Mapelli, Francesco Shankar, David M. Alexander, Alessandro Bressan, and Luigi Danese

The Astrophysical Journal, Volume 924, Number 2 DOI 10.3847/1538-4357/ac34fb

arXiv:2110.1607v1 (astro-ph.GA), 29 October 2021, https://arxiv.org/abs/2110.15607#

ABSTRACT: This is the first paper in a series aimed at modeling the black hole (BH) mass function, from the stellar to the intermediate to the (super)massive regime. In the present work, we focus on stellar BHs and provide an ab initio computation of their mass function across cosmic times; we mainly consider the standard, and likely dominant, production channel of stellar-mass BHs constituted by isolated single/binary star evolution. Specifically, we exploit the state-of-the-art stellar and binary evolutionary code SEVN, and couple its outputs with redshift-dependent galaxy statistics and empirical scaling relations involving galaxy metallicity, star formation rate and stellar mass. The resulting relic mass function dN dVd m log • as a function of the BH mass m• features a rather flat shape up to m• ≈ 50 Me and then a log-normal decline for larger masses, while its overall normalization at a given mass increases with decreasing redshift. We highlight the contribution to the local mass function from isolated stars evolving into BHs and from binary stellar systems ending up in single or binary BHs. We also include the distortion on the mass function induced by binary BH mergers, finding that it has a minor effect at the high-mass end. We estimate a local stellar BH relic mass density of ρ• ≈ 5 × 107 Me Mpc−3, which exceeds by more than two orders of magnitude that in supermassive BHs; this translates into an energy density parameter Ω• ≈ 4 × 10−4, implying that the total mass in stellar BHs amounts to 1% of the local baryonic matter. We show how our mass function for merging BH binaries compares with the recent estimates from gravitational wave observations by LIGO/Virgo, and discuss the possible implications for dynamical formation of BH binaries in dense environments like star clusters. We address the impact of adopting different binary stellar evolution codes (SEVN and COSMIC) on the mass function, and find the main differences to occur at the high-mass end, in connection with the numerical treatment of stellar binary evolution effects. We highlight that our results can provide a firm theoretical basis for a physically motivated light seed distribution at high redshift, to be implemented in semi-analytic and numerical models of BH formation and evolution. Finally, we stress that the present work can constitute a starting point to investigate the origin of heavy seeds and the growth of (super)massive BHs in high-redshift star-forming galaxies, that we will pursue in forthcoming papers.

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

G. Speranza (IAC), B. Balmaverde, A. Capetti, F. Massaro, G. Tremblay, A. Marconi, G. Venturi, M. Chiaberge, R. D. Baldi, S. Baum, P. Grandi, E. T. Meyer, C. O’Dea, W. Sparks, B. A. Terrazas and E. Torresi

Astronomy & Astrophysics, Volume 653, Article Number A150, September 2021, https://doi.org/10.1051/0004-6361/202140686

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 − 10⁷ M_⊙, 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 Ė_kin ∼ 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.

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Non-isotropic feedback from accreting spinning black holes

Luca Sala (LMU), Elia Cenci, Pedro R Capelo, Alessandro Lupi, 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.

https://doi.org/10.1051/0004-6361/202140686