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1. The radio galaxy population in the simba simulations

   https://doi.org/10.1093/mnras/stab654  

   Thomas, Nicole ; Davé, Romeel ; Jarvis, Matt J ; Anglés-Alcázar, Daniel ( March 2021 , Monthly Notices of the Royal Astronomical Society)

   ABSTRACT We examine the 1.4 GHz radio luminosities of galaxies arising from star formation and active galactic nuclei (AGNs) within the state-of-the-art cosmological hydrodynamic simulation Simba. Simba grows black holes via gravitational torque limited accretion from cold gas and Bondi accretion from hot gas, and employs AGN feedback including jets at low Eddington ratios. We define a population of radio loud AGNs (RLAGNs) based on the presence of ongoing jet feedback. Within RLAGN, we define high and low excitation radio galaxies (HERGs and LERGs) based on their dominant mode of black hole accretion: torque limited accretion representing feeding from a cold disc, or Bondi representing advection-dominated accretion from a hot medium. Simba predicts good agreement with the observed radio luminosity function (RLF) and its evolution, overall as well as separately for HERGs and LERGs. Quiescent galaxies with AGN-dominated radio flux dominate the RLF at $\gtrsim 10^{22-23}$ W Hz−1, while star formation dominates at lower radio powers. Overall, RLAGNs have higher black hole accretion rates and lower star formation rates than non-RLAGN at a given stellar mass or velocity dispersion, but have similar black hole masses. Simba predicts an LERG number density of 8.53 Mpc−3, ∼10× higher than for HERGs, broadly as observed. While LERGs dominate amongmore »most massive galaxies with the largest black holes and HERGs dominate at high specific star formation rates, they otherwise largely populate similar-sized dark matter haloes and have similar host galaxy properties. Simba thus predicts that deeper radio surveys will reveal an increasing overlap between the host galaxy demographics of HERGs and LERGs.« less
2. Intermediate-mass black holes and the Fundamental Plane of black hole accretion

   https://doi.org/10.1093/mnras/stac2608  

   Gültekin, Kayhan ; Nyland, Kristina ; Gray, Nichole ; Fehmer, Greg ; Huang, Tianchi ; Sparkman, Matthew ; Reines, Amy E. ; Greene, Jenny E. ; Cackett, Edward M. ; Baldassare, Vivienne ( September 2022 , Monthly Notices of the Royal Astronomical Society)

   We present new 5 GHz Very Large Array observations of a sample of eight active intermediate-mass black holes with masses 104.9 M⊙ < M < 106.1 M⊙ found in galaxies with stellar masses M* < 3 × 109 M⊙. We detected five of the eight sources at high significance. Of the detections, four were consistent with a point source, and one (SDSS J095418.15+471725.1, with black hole mass M < 105 M⊙) clearly shows extended emission that has a jet morphology. Combining our new radio data with the black hole masses and literature X-ray measurements, we put the sources on the Fundamental Plane of black hole accretion. We find that the extent to which the sources agree with the Fundamental Plane depends on their star-forming/composite/active galactic nucleus (AGN) classification based on optical narrow emission-line ratios. The single star-forming source is inconsistent with the Fundamental Plane. The three composite sources are consistent, and three of the four AGN sources are inconsistent with the Fundamental Plane. We argue that this inconsistency is genuine and not a result of misattributing star formation to black hole activity. Instead, we identify the sources in our sample that have AGN-like optical emission-line ratios as not following the Fundamental Plane and thus cautionmore »the use of the Fundamental Plane to estimate masses without additional constraints, such as radio spectral index, radiative efficiency, or the Eddington fraction.

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3. Jets from SANE super-Eddington accretion discs: morphology, spectra, and their potential as targets for ngEHT

   https://doi.org/10.1093/mnras/stac3716  

   Curd, Brandon ; Emami, Razieh ; Anantua, Richard ; Palumbo, Daniel ; Doeleman, Sheperd ; Narayan, Ramesh ( December 2022 , Monthly Notices of the Royal Astronomical Society)

   We present general relativistic radiation magnetohydrodynamics (GRRMHD) simulations of super-Eddington accretion flows around supermassive black holes (SMBHs), which may apply to tidal disruption events (TDEs). We perform long duration ($t\ge 81,200\, GM/c^3$) simulations that achieve mass accretion rates ≳11 times the Eddington rate and produce thermal synchrotron spectra and images of their jets. Gas flowing beyond the funnel wall expands conically and drives a strong shock at the jet head while variable mass ejection and recollimation, along the jet axis, results in internal shocks and dissipation. Assuming the ion temperature (Ti) and electron temperature (Te) in the plasma are identical, the radio/submillimetre spectra peak at >100 GHz and the luminosity increases with BH spin, exceeding $\sim 10^{41} \, \rm {erg\, s^{-1}}$ in the brightest models. The emission is extremely sensitive to Ti/Te as some models show an order-of-magnitude decrease in the peak frequency and up to four orders-of-magnitude decline in their radio/submillimetre luminosity as Ti/Te approaches 20. Assuming a maximum VLBI baseline distance of 10 Gλ, 230 GHz images of Ti/Te = 1 models shows that the jet head may be bright enough for its motion to be captured with the EHT (ngEHT) at D ≲ 110 (180) Mpc at the 5σ significance level.more »Resolving emission from internal shocks requires D ≲ 45 Mpc for both the EHT or ngEHT.

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4. BAT AGN Spectroscopic Survey – XIII. The nature of the most luminous obscured AGN in the low-redshift universe

   https://doi.org/10.1093/mnras/stz2309  

   Bär, Rudolf E ; Trakhtenbrot, Benny ; Oh, Kyuseok ; Koss, Michael J ; Wong, O Ivy ; Ricci, Claudio ; Schawinski, Kevin ; Weigel, Anna K ; Sartori, Lia F ; Ichikawa, Kohei ; et al ( November 2019 , Monthly Notices of the Royal Astronomical Society)

   ABSTRACT We present a multiwavelength analysis of 28 of the most luminous low-redshift narrow-line, ultra-hard X-ray-selected active galactic nuclei (AGN) drawn from the 70-month Swift/BAT all-sky survey, with bolometric luminosities of $\log (L_{\rm bol} /{\rm erg\, s}^{-1}) \gtrsim 45.25$. The broad goal of our study is to determine whether these objects have any distinctive properties, potentially setting them aside from lower luminosity obscured AGN in the local Universe. Our analysis relies on the first data release of the BAT AGN Spectroscopic Survey (BASS/DR1) and on dedicated observations with the VLT, Palomar, and Keck observatories. We find that the vast majority of our sources agree with commonly used AGN selection criteria which are based on emission line ratios and on mid-infrared colours. Our AGN are pre-dominantly hosted in massive galaxies (9.8 ≲ log (M*/M⊙) ≲ 11.7); based on visual inspection of archival optical images, they appear to be mostly ellipticals. Otherwise, they do not have distinctive properties. Their radio luminosities, determined from publicly available survey data, show a large spread of almost four orders of magnitude – much broader than what is found for lower X-ray luminosity obscured AGN in BASS. Moreover, our sample shows no preferred combination of black hole massesmore »(MBH) and/or Eddington ratio (λEdd), covering 7.5 ≲ log (MBH/M⊙) ≲ 10.3 and 0.01 ≲ λEdd ≲ 1. Based on the distribution of our sources in the λEdd−NH plane, we conclude that our sample is consistent with a scenario where the amount of obscuring material along the line of sight is determined by radiation pressure exerted by the AGN on the dusty circumnuclear gas.« less
5. Characterizing Compact 15–33 GHz Radio Continuum Sources in Local U/LIRGs

   https://doi.org/10.3847/1538-4357/ac923b  

   Song, Y. ; Linden, S. T. ; Evans, A. S. ; Barcos-Muñoz, L. ; Murphy, E. J. ; Momjian, E. ; Díaz-Santos, T. ; Larson, K. L. ; Privon, G. C. ; Huang, X. ; et al ( November 2022 , The Astrophysical Journal)

   We present the analysis of ∼100 pc scale compact radio continuum sources detected in 63 local (ultra)luminous infrared galaxies (U/LIRGs;L_IR≥ 10¹¹L_⊙), using FWHM ≲ 0.″1–0.″2 resolution 15 and 33 GHz observations with the Karl G. Jansky Very Large Array. We identify a total of 133 compact radio sources with effective radii of 8–170 pc, which are classified into four main categories—“AGN” (active galactic nuclei), “AGN/SBnuc” (AGN-starburst composite nucleus), “SBnuc” (starburst nucleus), and “SF” (star-forming clumps)—based on ancillary data sets and the literature. We find that “AGN” and “AGN/SBnuc” more frequently occur in late-stage mergers and have up to 3 dex higher 33 GHz luminosities and surface densities compared with “SBnuc” and “SF,” which may be attributed to extreme nuclear starburst and/or AGN activity in the former. Star formation rates (SFRs) and surface densities (Σ_SFR) are measured for “SF” and “SBnuc” using both the total 33 GHz continuum emission (SFR ∼ 0.14–13M_⊙yr⁻¹, Σ_SFR∼ 13–1600M_⊙yr⁻¹kpc⁻²) and the thermal free–free emission from Hiiregions (median SFR_th∼ 0.4M_⊙yr⁻¹,${\mathrm{\Sigma }}_{{\mathrm{SFR}}_{\mathrm{th}}}\sim 44M_{\odot }$yr⁻¹kpc⁻²). These values are 1–2 dex higher than those measured for similar-sized clumps in nearby normal (non-U/LIRGs). The latter also have a much flatter median 15–33 GHz spectral index (∼−0.08) compared withmore »“SBnuc” and “SF” (∼−0.46), which may reflect higher nonthermal contribution from supernovae and/or interstellar medium densities in local U/LIRGs that directly result from and/or lead to their extreme star-forming activities on 100 pc scales.

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