Macon Magno

A tight correlation between nuclear millimeter and X-ray emission has recently been found in nearby ( z < 0.01) and low-Eddington ratio ( λ _Edd < 0.1) radio-quiet active galactic nuclei (AGNs), suggesting a common origin in the hot X-ray corona. We test this relation in nine more distant AGNs ( z ∼ 0.06–0.16) with higher bolometric luminosities ( log ( L bol / erg s − 1 ) = 45.3 –46.3), Eddington ratios ( λ _Edd = 0.19–0.85), and X-ray bolometric corrections ( κ = 29–194), selected from the Burst Alert Telescope (BAT) survey. We obtained observations with Swift at 2–10 keV and quasi-simultaneous observations with the Atacama Large Millimeter/submillimeter Array at 100 GHz with high angular resolution ( . ″ 14 arcsec). We find that these high-luminosity AGNs lie above the millimeter/X-ray correlation defined by lower-luminosity sources. A joint fit to both samples yields a second-degree polynomial with an intrinsic scatter of 0.32 dex. Furthermore, the millimeter emission correlates linearly with both the UV disk luminosity and L _bol , with intrinsic scatters of 0.45 and 0.35 dex, respectively. We propose that the deviation from the linear millimeter/X-ray relation arises from a two-component coronal electron population: thermal electrons that produce X-rays, but become less efficient at higher luminosities, and nonthermal electrons that produce millimeter emission and remain tied to L _bol . Additional millimeter emission from outflow-driven shocks may also contribute, though spectral energy distribution modeling and spectral index studies favor a coronal origin.

We present high-spatial-resolution (≲1 . ″ 0), multiwavelength observations of UGC 2369S, a nearby luminous infrared galaxy showing three distinct cores separated on kiloparsec scales in near-infrared (NIR) imaging with significant X-ray emission. Utilizing optical/NIR adaptive optics, radio, Chandra X-ray, as well as archival Hubble Space Telescope imaging, we perform a comprehensive study of active galactic nuclei (AGN) activity, obscuration, and host properties. As one of the clearest cases of a triple-nucleus merger at ≃3 kpc separations, UGC 2369S is the first to be studied with high-resolution observations at multiple wavelengths. We find that the northern core, having possibly the most massive black hole (BH) in the system ( M _BH ≃ 10 ⁸ M _⊙ ), is consistent with a heavily obscured AGN. However, its high dust extinction ( A _v > 5), hydrogen column density ( N _H ≳ 10 ²⁵ cm ⁻² ), and nondetection of optical coronal lines and coronal X-ray emission leave the identification inconclusive. The other two cores show no evidence for black-hole activity and instead exhibit signatures of tidal disruption. From stellar mass surface density and stellar velocity dispersion maps, we infer that the strongly varying gravitational potential in this three-body system may have cannibalized the stellar bulge of the southwestern core, leaving a metal-enriched remnant. An ongoing survey focusing on similar triple systems could help us understand how they evolve and help benchmark numerical simulations, providing insight into gravitational wave predictions and the formation of the most massive BHs.

We present neutral atomic hydrogen (H I ) imaging observations of 22 H I -rich ( M _HI ≳ 10 ^9.7 M _⊙ ), hard X-ray-selected local Seyferts to explore how cool gas is supplied to active galactic nuclei (AGN) hosts. The sample predominantly resides in group-like, gas-rich environments. About 80% (18/22) of the galaxies have H I -detected neighbors, 61% (11/18) of which clearly exhibit strong lopsidedness, one-sided gas tails, and/or gas structures connecting to nearby companion galaxies, suggesting gas exchange histories. We examine the H I size-mass relation and star formation properties of these H I -rich AGN hosts, finding no systematic deviations from known scaling relations. In most cases, our samples are the most massive systems within their respective groups, implying that our sample is more likely to acquire gas rather than lose it. Interestingly, galaxies with more extended H I disks show stronger AGN activity. Considering that extended H I is often associated with external processes, this finding suggests that environmentally accreted gas – through galaxy interactions and gas exchange with neighboring systems – may have played a role in supplying additional fuel to the AGNs in our sample. Notably, the H I extent–AGN activity correlation becomes even tighter for those AGN hosts whose neighboring galaxies are gas poor or lack H I , further supporting externally supplied gas as a fuel source.

We present serendipitous simultaneous radio and X-ray light curves of the dwarf Seyfert galaxy UGC 6728 spanning 5 yr. The X-ray light curve exhibits a flaring period, followed by a gradual rise and decline. Throughout these events, the X-ray hardness ratio and spectrum do not change significantly. The radio flux is constant, as far as can be determined from its sparse sampling, until the end of the X-ray flare, then decreases by a factor of two by the midpoint of the gradual X-ray rise before returning to baseline at the end of the X-ray decline. We interpret this behavior in light of a similar event recently reported in NGC 2992, in which there is a temporary obscuration of the radio source by a blob of plasma ejected by a magnetic reconnection in the accretion disk. The energetics of the X-ray flare are consistent with those expected from magnetic disk activity. As in NGC 2992, the X-ray spectrum does not evolve during the obscuration event. We also discuss the possibility that the observed phenomena are due to normal active galactic nuclei coronal flaring and variability, which is plausible but unlikely, given the lack of spectral variation.

We present Stokes I continuum analysis for a volume-limited sample (C band (4.4 GHz), despite expectations. We determined that coronal emission is unlikely to be a dominant emission mechanism for the sources not detected by the VLBA, and the emission measured with the VLA is likely produced beyond parsec spatial scales. We also explore potential radiation mechanisms for the circumnuclear radio emission that is produced beyond the observable parsec physical scales probed with the VLBA but within the ≤30–110 pc spatial scales observed with the VLA. From an energetics perspective, we find that all targets have extranuclear radio emission that is compatible with AGN winds, assuming a maximum of 10% of the bolometric output can supply the mechanical energy observed. We also find that the excess emission is likely too strong for star formation alone when compared to results from optical spectroscopy, but may contribute in smaller capacities.

We present serendipitous simultaneous radio and X-ray light curves of the dwarf Seyfert galaxy UGC 6728 spanning 5 years. The X-ray light curve exhibits a flaring period, followed by a gradual rise and decline. Throughout these events, the X-ray hardness ratio and spectrum do not change significantly. The radio flux is constant, as far as can be determined from its sparse sampling, until the end of the X-ray flare, then decreases by a factor of two by the midpoint of the gradual X-ray rise before returning to baseline at the end of the X-ray decline. We interpret this behavior in light of a similar event recently reported in NGC 2992, in which there is a temporary obscuration of the radio source by a blob of plasma ejected by a magnetic reconnection in the accretion disk. The energetics of the X-ray flare are consistent with those expected from magnetic disk activity. As in NGC 2992, the X-ray spectrum does not evolve during the obscuration event. We also discuss the possibility that the observed phenomena are due to normal AGN coronal flaring and variability, which is plausible but unlikely given the lack of spectral variation.

A fraction of active galactic nuclei (AGN) have double-peaked Hα, Hβ, and Mg II broad lines attributed to emission from rotating gas in the accretion disk. Using optical spectroscopy of a flux-limited sample of AGN selected via ultrahard X-rays from the BAT AGN Spectroscopic Survey (BASS), we systematically identify 71 double-peaked emitters (DPEs) among 343 broad-line AGN with redshifts 0.004 < z < 0.297 and X-ray luminosities of 40 < log L 2 − 10 KeV (erg s⁻¹) < 45.7, and provide their best-fit accretion disk parameters. We find that ∼21% of X-ray-selected broad-line AGN are DPEs, consistent with rates previously reported for z < 0.2 broad-line AGN selected for strong optical variability in the Zwicky Transient Facility. 11 of 71 DPEs (15%) exhibited a single-peaked Gaussian component to the broad line profile in addition to the double-peaked disk profile. In this sample, DPEs have intrinsically higher masses by ∼0.4 dex and lower Eddington ratios by ∼0.3 dex than other broad-line AGN, and have a preference for elliptical host galaxies, higher X-ray luminosities, and higher [O i] λ6302 to narrow Hα flux ratios than other broad-line AGN. We find that DPEs are not segregated from non-DPE broad-line AGN in the L _bol versus M _BH relation or their X-ray to radio luminosity ratios, and do not show a preference for intermediate Seyfert types over Seyfert 1s. We do not find differences in a wide range of multiwavelength properties when comparing DPEs to non-DPE broad-line AGN, including optical and mid-IR variability levels, Wide-field Infrared Survey Explorer colors, α _ox, the column density of neutral obscuring material N _H, and the rate of changing-look events. We discuss the two populations in the context of multicomponent disk-wind models of the AGN broad-line region and consider how unrecognized contributions of disk emission to the broad lines may introduce biases in “virial” supermassive black hole mass estimates, with consequences for the inferred M _BH–M _* relation.

Context. Active galactic nuclei (AGNs) host accreting supermassive black holes (SMBHs). The accretion process can lead to the formation of a hot, X-ray emitting corona close to the SMBH that can accelerate relativistic electrons. Observations in the millimeter band can probe its synchrotron emission. Aims. We intend to provide a framework to derive physical information of SMBH coronae by modelling their spectral energy distribution (SED) from radio to far-infrared frequencies. We also explore the possibilities of deriving additional information from millimeter observations, such as the SMBH mass, and studying high-redshift lensed sources. Methods. We introduce a corona emission model based on a one-zone spherical region with a hybrid thermal and non-thermal plasma. We investigated the dependence of the corona SED on different parameters such as size, opacity, and magnetic field strength. Other galactic emission components from dust, ionised gas, and diffuse relativistic electrons were also included in the SED fitting scheme. We applied our code consistently to a sample of radio-quiet AGNs with strong indications of a coronal component in the millimeter. Results. The detected millimeter emission from SMBH coronae is consistent with a non-thermal relativistic particle population with an energy density that is ≈0.5–10% of that in the thermal plasma. This requires magnetic energy densities close to equipartition with the thermal gas and corona sizes of 60–250 gravitational radii. The model can also reproduce the observed correlation between millimeter emission and SMBH mass when we accounted for the uncertainties in the corona size. Conclusions. The millimeter band offers a unique window into the physics of SMBH coronae, enabling the study of highly dust-obscured sources and high-redshift lensed quasars. Gaining a deeper understanding of the relativistic particle population in SMBH coronae can provide key insights into their potential multiwavelength and neutrino emission.

We present a detailed analysis of the most luminous and obscured active galactic nuclei (AGNs) detected in the ultra-hard X-ray band (14–195 kev) by the Swift/Burst Alert Telescope. Our sample comprises 21 X-ray luminous ( log L X / erg s − 1 > 44.6 , 2–10 keV) AGNs at z < 0.6, optically classified as Seyfert 1.9 and 2. Using NuSTAR, XMM-Newton, Suzaku, and Chandra data, we constrain AGN properties such as absorption column density N _H, photon index Γ, intrinsic L _X, covering factor, and iron Kα equivalent width. We find median line-of-sight log N H / cm − 2 = 23 . 5 − 1.2 + 0.5 and 2–10 keV rest-frame, de-absorbed log L X / erg s − 1 = 44 . 7 − 0.6 + 0.8 , at the 5th and 95th percentiles. For sources with black hole mass estimates (12/20), we find a weak correlation between Γ and Eddington ratio (λ _Edd). Of these, six (50% ± 13%) lie in the N _H-λ _Edd “forbidden region” and exhibit a combined higher prevalence of N _H variability and outflow signatures, suggesting a transitional phase where AGN feedback may be clearing the obscuring material. For the 13/21 sources with multi-epoch X-ray spectroscopy, 85 − 15 + 5 % exhibit variability in either 2–10 keV flux ( 77 − 15 + 8 % ) or line-of-sight N _H ( 3 3 − 10 + 15 % ). For the 20/21 sources with available near-UV/optical spectroscopy, we detect [Ne v]λ3426 in 17 ( 8 5 − 11 + 5 %), confirming its reliability to probe AGN emission even in heavily obscured systems. When renormalized to the same [O iii]λ5007 peak flux as z = 2−9 narrow-line AGNs identified with JWST, our sample exhibits significantly stronger [Ne v]λ3426 emission, suggesting that high-redshift obscured AGNs may be intrinsically weaker in [Ne v]λ3426 or that [Ne v]λ3426 is more challenging to detect in those environments. The sources presented in this work serve as a benchmark for high-redshift analogs, showing the potential of [Ne v]λ3426 to reveal obscured AGNs and the need for future missions to expand X-ray studies into the high-redshift Universe.