A high-resolution view of the filament of gas between Abell 399 and Abell 401 from the Atacama Cosmology Telescope and MUSTANG-2
Creators: name: Hincks, Adam D.
name: Radiconi, Federico
name: Romero, Charles
name: Madhavacheril, Mathew S.
name: Mroczkowski, Tony
name: Austermann, Jason E.
name: Barbavara, Eleonora
name: Battaglia, Nicholas
name: Battistelli, Elia
name: Bond, J. Richard
name: Calabrese, Erminia
name: de Bernardis, Paolo
name: Devlin, Mark J.
name: Dicker, Simon R.
name: Duff, Shannon M.
name: Duivenvoorden, Adriaan J.
name: Dunkley, Jo
name: Dünner, Rolando
name: Gallardo, Patricio A.
name: Govoni, Federica
name: Hill, J. Colin
name: Hilton, Matt
name: Hubmayr, Johannes
name: Hughes, John P.
name: Lamagna, Luca
name: Lokken, Martine
name: Masi, Silvia
name: Mason, Brian S.
name: McMahon, Jeff
name: Moodley, Kavilan
name: Murgia, Matteo
name: Naess, Sigurd
name: Page, Lyman
name: Piacentini, Francesco
name: Salatino, Maria
name: Sarazin, Craig L.
name: Schillaci, Alessandro
name: Sievers, Jonathan L.
name: Sifón, Cristóbal
name: Staggs, Suzanne
name: Ullom, Joel N.
name: Vacca, Valentina
name: Van Engelen, Alexander
name: Vissers, Michael R.
name: Wollack, Edward J.
name: Xu, Zhilei
Publisher: name: arXiv
Year: 2021
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: We report a significant detection of the hot intergalactic medium in the filamentary bridge connecting the galaxy clusters Abell 399 and Abell 401. This result is enabled by a low-noise, high-resolution map of the thermal Sunyaev-Zeldovich signal from the Atacama Cosmology Telescope (ACT) and Planck satellite. The ACT data provide the $1.65'$ resolution that allows us to clearly separate the profiles of the clusters, whose centres are separated by $37'$, from the gas associated with the filament. A model that fits for only the two clusters is ruled out compared to one that includes a bridge component at $&gt;5σ$. Using a gas temperature determined from Suzaku X-ray data, we infer a total mass of $(3.3\pm0.7)\times10^{14}\,\mathrm{M}_{\odot}$ associated with the filament, comprising about $8\%$ of the entire Abell 399-Abell 401 system. We fit two phenomenological models to the filamentary structure; the favoured model has a width transverse to the axis joining the clusters of ${\sim}1.9\,\mathrm{Mpc}$. When combined with the Suzaku data, we find a gas density of $(0.88\pm0.24)\times10^{-4}\,\mathrm{cm}^{-3}$, considerably lower than previously reported. We show that this can be fully explained by a geometry in which the axis joining Abell 399 and Abell 401 has a large component along the line of sight, such that the distance between the clusters is significantly greater than the $3.2\,\mathrm{Mpc}$ projected separation on the plane of the sky. Finally, we present initial results from higher resolution ($12.7"$ effective) imaging of the bridge with the MUSTANG-2 receiver on the Green Bank Telescope.
description: 23 pages, 10 figures, 3 tables. This is a pre-copyedited, author-produced PDF of an article accepted for publication in the Monthly Notices of the Royal Astronomical Society following peer review. The version of record is available online at: https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/stab3391/6442294