Galaxy formation and evolution

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On the relationship between the cosmic web and the alignment of galaxies and AGN jets

Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) (2025)

Authors:

S Lyla Jung, IH Whittam, MJ Jarvis, CL Hale, MN Tudorache, T Yasin

Abstract:

Abstract The impact of active galactic nuclei (AGN) on the evolution of galaxies explains the steep decrease in the number density of the most massive galaxies in the Universe. However, the fueling of the AGN and the efficiency of this feedback largely depend on their environment. We use data from the Low Frequency Array (LOFAR) Two-metre Sky Survey Data Release 2 (LoTSS DR2), the Dark Energy Spectroscopic Instrument (DESI) Legacy Imaging Surveys, and the Sloan Digital Sky Survey (SDSS) DR12 to make the first study of the orientations of radio jets and their optical counterpart in relation to the cosmic web environment. We find that close to filaments ($\lesssim 11 \, \rm Mpc$), galaxies tend to have their optical major axes aligned with the nearest filaments. On the other hand, radio jets, which are generally aligned perpendicularly to the optical major axis of the host galaxy, show more randomised orientations with respect to host galaxies within $\lesssim 8 \, \rm Mpc$ of filaments. These results support the scenario that massive galaxies in cosmic filaments grow by numerous mergers directed along the orientation of the filaments while experiencing chaotic accretion of gas onto the central black hole. The AGN-driven jets consequently have a strong impact preferentially along the minor axes of dark matter halos within filaments. We discuss the implications of these results for large-scale radio jet alignments, intrinsic alignments between galaxies, and the azimuthal anisotropy of the distribution of circumgalactic medium and anisotropic quenching.
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Cosmic ray transport and acceleration with magnetic mirroring

Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) (2025) staf562

Authors:

AR Bell, JH Matthews, AM Taylor, G Giacinti
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REBELS-IFU: dust attenuation curves of 12 massive galaxies at z ≃ 7

Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) 539:1 (2025) 109-126

Authors:

R Fisher, RAA Bowler, M Stefanon, LE Rowland, HSB Algera, M Aravena, R Bouwens, P Dayal, A Ferrara, Y Fudamoto, C Gulis, JA Hodge, H Inami, K Ormerod, A Pallottini, SG Phillips, NS Sartorio, S Schouws, R Smit, L Sommovigo, DP Stark, PP van der Werf
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A MeerKAT survey of nearby dwarf novae: I. New detections

Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) (2025) staf556

Authors:

J Kersten, E Körding, PA Woudt, PJ Groot, DRA Williams, I Heywood, DL Coppejans, C Knigge, JCA Miller-Jones, GR Sivakoff, R Fender
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Prompt gravitational-wave mergers aided by gas in Active Galactic Nuclei: The hydrodynamics of binary-single black hole scatterings

Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) (2025)

Authors:

Connar Rowan, Henry Whitehead, Gaia Fabj, Pankaj Saini, Bence Kocsis, Martin Pessah, Johan Samsing

Abstract:

Abstract Black hole binary systems embedded in AGN discs have been proposed as a source of the observed gravitational waves (GWs) from LIGO-Virgo-KAGRA. Studies have indicated binary-single encounters could be common place within this population, yet we lack a comprehensive understanding of how the ambient gas affects the dynamics of these three-body encounters. We present the first hydrodynamical simulations of black hole binary-single encounters in an AGN disc. We find gas is a non-negligible component of binary-single interactions, leading to unique dynamics, including the formation of quasi-stable hierarchical triples. The gas efficiently and reliably dissipates the energy of the three-body system, hardening the triple provided it remains bound after the initial encounter. The hardening timescale is shorter for higher ambient gas densities. Formed triples can be hardened reliably by 2 − 3 orders of magnitude relative to the initial binary semi-major axis within less than a few AGN orbits, limited only by our resolution. The gas hardening of the triple enhances the probability for a merger by a minimum factor of 3.5 − 8 depending on our assumptions. In several cases, two of the black holes can execute periapses of less than 10 Schwarzschild radii, where the dynamics were fully resolved for previous close approaches. Our results suggest that current timescale estimates (without gas drag) for binary-single induced mergers are an upper bound. The shrinkage of the triple by gas has the prospect of increasing the chance for unique GW phenomena such as residual eccentricity, dephasing from a third object and double GW mergers.
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