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1. IFU observations of the inner 200 pc of NGC 4546: gas rotation, non-circular motions, and ionized outflows

   https://doi.org/10.1093/mnras/stac3041  

   Heckler, Kelly F. ; Ricci, Tiago V. ; Riffel, Rogemar A. ( October 2022 , Monthly Notices of the Royal Astronomical Society)

   We present a detailed analysis of the ionized gas distribution and kinematics in the inner ∼ 200 pc of NGC 4546, host of a low-luminosity active galactic nucleus (LLAGN). Using GMOS−IFU observations, with a spectral coverage of 4736–6806 Å  and an angular resolution of 0.7 arcsec, we confirm that the nuclear emission is consistent with photoionization by an AGN, while the gas in the circumnuclear region may be ionized by hot low-mass evolved stars. The gas kinematics in the central region of NGC 4546 presents three components: (i) a disc with major axis oriented along a position angle of 43° ± 3°, counter rotating relative to the stellar disc; (ii) non-circular motions, evidenced by residual velocities of up to 60 km s−1, likely associated with a previous capture of a dwarf satellite by NGC 4546; and (iii) nuclear outflows in ionized gas, identified as a broad component (σ ∼ 320 km s−1) in the line profiles, with a mass outflow rate of $\dot{M}_{\rm out} = 0.3 \pm 0.1$ M⊙ yr−1 and a total mass of Mout = (9.2 ± 0.8) × 103 M⊙ in ionized gas, corresponding to less than 3 per cent of the total mass of ionized gas in the inner 200 pc of NGC 4546. The kinetic efficiency of themore »outflow is roughly 0.1 per cent, which is smaller than the outflow coupling efficiencies predicted by theoretical studies to AGN feedback become efficient in suppressing star formation in the host galaxy.

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2. The multiphase gas structure and kinematics in the circumnuclear region of NGC 5728

   https://doi.org/10.1093/mnras/stz2802  

   Shimizu, T. Taro ; Davies, R. I. ; Lutz, D. ; Burtscher, L. ; Lin, M. ; Baron, D. ; Davies, R. L. ; Genzel, R. ; Hicks, E. K. S. ; Koss, M. ; et al ( October 2019 , Monthly Notices of the Royal Astronomical Society)

   We report on our combined analysis of HST, VLT/MUSE, VLT/SINFONI, and ALMA observations of the local Seyfert 2 galaxy, NGC 5728 to investigate in detail the feeding and feedback of the active galactic nucleus (AGN). The data sets simultaneously probe the morphology, excitation, and kinematics of the stars, ionized gas, and molecular gas over a large range of spatial scales (10 pc to 10 kpc). NGC 5728 contains a large stellar bar that is driving gas along prominent dust lanes to the inner 1 kpc where the gas settles into a circumnuclear ring. The ring is strongly star forming and contains a substantial population of young stars as indicated by the lowered stellar velocity dispersion and gas excitation consistent with H ii regions. We model the kinematics of the ring using the velocity field of the CO (2–1) emission and stars and find it is consistent with a rotating disc. The outer regions of the disc, where the dust lanes meet the ring, show signatures of inflow at a rate of 1 M$\odot$ yr−1. Inside the ring, we observe three molecular gas components corresponding to the circular rotation of the outer ring, a warped disc, and the nuclear stellar bar. The AGN is driving an ionized gasmore »outflow that reaches a radius of 250 pc with a mass outflow rate of 0.08 M$\odot$ yr−1 consistent with its luminosity and scaling relations from previous studies. While we observe distinct holes in CO emission which could be signs of molecular gas removal, we find that largely the AGN is not disrupting the structure of the circumnuclear region.

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3. The Rapid X-Ray and UV Evolution of ASASSN-14ko

   https://doi.org/10.3847/1538-4357/ac480c  

   Payne, Anna V. ; Shappee, Benjamin J. ; Hinkle, Jason T. ; Holoien, Thomas W. -S. ; Auchettl, Katie ; Kochanek, Christopher S. ; Stanek, K. Z. ; Thompson, Todd A. ; Tucker, Michael A. ; Armstrong, James D. ; et al ( February 2022 , The Astrophysical Journal)

   ASASSN-14ko is a recently discovered periodically flaring transient at the center of the active galactic nucleus (AGN) ESO 253−G003 with a slowly decreasing period. Here, we show that the flares originate from the northern, brighter nucleus in this dual-AGN, post-merger system. The light curves for the two flares that occurred in 2020 May and September are nearly identical over all wavelengths. For both events, Swift observations showed that the UV and optical wavelengths brightened in unison. The effective temperature of the UV/optical emission rises and falls with the increase and subsequent decline in the luminosity. The X-ray flux, by contrast, first rapidly drops over ∼2.6 days, rises for ∼5.8 days, drops again over ∼4.3 days, and then recovers. The X-ray spectral evolution of the two flares differ, however. During the 2020 May peak the spectrum softened with increases in the X-ray luminosity, while we observed the reverse for the 2020 September peak. We found a small change in the period derivative, which seems to indicate that the system does not have a static period derivative and there is some stochasticity in its evolution.
4. Gas inflows in the polar ring of NGC 4111: the birth of an AGN

   https://doi.org/10.1093/mnras/stac634  

   Hauschild Roier, Gabriel R. ; Storchi-Bergmann, Thaisa ; McDermid, Richard M. ; Walsh, Jonelle L. ; Tan, Joanne ; Cohn, Jonathan ; Krajnovic, Davor ; Greene, Jenny ; Valluri, Monica ; Gültekin, Kayhan ; et al ( March 2022 , Monthly Notices of the Royal Astronomical Society)

   We have used Hubble Space Telescope (HST) images, SAURON Integral Field Spectroscopy (IFS), and adaptative optics assisted Gemini NIFS near-infrared K-band IFS to map the stellar and gas distribution, excitation and kinematics of the inner few kpc of the nearby edge-on S0 galaxy NGC 4111. The HST images map its ≈450 pc diameter dusty polar ring, with an estimated gas mass ≥107 M⊙. The NIFS data cube maps the inner 110 pc radius at ≈7 pc spatial resolution, revealing a ≈220 pc diameter polar ring in hot (2267 ± 166 K) molecular H2 1–0 S(1) gas embedded in the polar ring. The stellar velocity field shows disc-dominated kinematics along the galaxy plane both in the SAURON large scale and in the NIFS nuclear-scale data. The large-scale [O iii] λ5007 Å velocity field shows a superposition of two disc kinematics: one similar to that of the stars and another along the polar ring, showing non-circular motions that seem to connect with the velocity field of the nuclear H2 ring, whose kinematics indicate accelerated inflow to the nucleus. The estimated mass inflow rate is enough not only to feed an active galactic nucleus (AGN) but also to trigger circumnuclear star formation in the near future. We propose a scenario in which gasmore »from the polar ring, which probably originated from the capture of a dwarf galaxy, is moving inwards and triggering an AGN, as supported by the local X-ray emission, which seems to be the source of the H2 1–0 S(1) excitation. The fact that we see neither near-UV nor Br γ emission suggests that the nascent AGN is still deeply buried under the optically thick dust of the polar ring.

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5. The Cosmic Ultraviolet Baryon Survey (CUBS) – I. Overview and the diverse environments of Lyman limit systems at z < 1

   https://doi.org/10.1093/mnras/staa1773  

   Chen, Hsiao-Wen ; Zahedy, Fakhri S ; Boettcher, Erin ; Cooper, Thomas M ; Johnson, Sean D ; Rudie, Gwen C ; Chen, Mandy C ; Walth, Gregory L ; Cantalupo, Sebastiano ; Cooksey, Kathy L ; et al ( September 2020 , Monthly Notices of the Royal Astronomical Society)

   ABSTRACT We present initial results from the Cosmic Ultraviolet Baryon Survey (CUBS). CUBS is designed to map diffuse baryonic structures at redshift z ≲ 1 using absorption-line spectroscopy of 15 UV-bright QSOs with matching deep galaxy survey data. CUBS QSOs are selected based on their NUV brightness to avoid biases against the presence of intervening Lyman limit systems (LLSs) at zabs < 1. We report five new LLSs of $\log \, N({\mathrm{ H} \,{\small I}})/{{\rm cm^{-2}}}\gtrsim 17.2$ over a total redshift survey path-length of $\Delta \, z_{\mathrm{ LL}}=9.3$, and a number density of $n(z)=0.43_{-0.18}^{+0.26}$. Considering all absorbers with $\log \, N({{\mathrm{ H} \,{\small I}}})/{{\rm cm^{-2}}}\gt 16.5$ leads to $n(z)=1.08_{-0.25}^{+0.31}$ at zabs < 1. All LLSs exhibit a multicomponent structure and associated metal transitions from multiple ionization states such as C ii, C iii, Mg ii, Si ii, Si iii, and O vi absorption. Differential chemical enrichment levels as well as ionization states are directly observed across individual components in three LLSs. We present deep galaxy survey data obtained using the VLT-MUSE integral field spectrograph and the Magellan Telescopes, reaching sensitivities necessary for detecting galaxies fainter than $0.1\, L_*$ at d ≲ 300 physical kpc (pkpc) in all five fields. A diverse range of galaxy properties ismore »seen around these LLSs, from a low-mass dwarf galaxy pair, a co-rotating gaseous halo/disc, a star-forming galaxy, a massive quiescent galaxy, to a galaxy group. The closest galaxies have projected distances ranging from d = 15 to 72 pkpc and intrinsic luminosities from ${\approx} 0.01\, L_*$ to ${\approx} 3\, L_*$. Our study shows that LLSs originate in a variety of galaxy environments and trace gaseous structures with a broad range of metallicities.« less