galaxies

First author: Rahul Srinivasan With nearly a hundred gravitational wave detections, the origin of black hole mergers has become a key question. Here, we focus on understanding the typical galactic environment in which binary black hole mergers arise. To this end, we synthesize progenitors of binary black hole mergers as a function of the redshift of progenitor formation, present-day formation galaxy mass, and progenitor stellar metallicity for $240$ star formation and binary evolution models.

First author: Enrico Peretti The enhanced activity typical of the core of Seyfert galaxies can drive powerful winds where high-energy phenomena can occur. In spite of their high power content, the number of such non-jetted active galactic nuclei detected in gamma-ray is very limited. In this Letter, we report the detection of a gamma-ray flux from NGC 4151, a Seyfert galaxy located at about 15.8 Mpc. The source is known for hosting ultra-fast outflows (UFOs) in its innermost core through X-ray spectroscopic observations, thereby becoming the first UFO host ever detected in gamma rays.

First author: H. Domínguez Sánchez Interactions between galaxies leave distinguishable imprints in the form of tidal features which hold important clues about their mass assembly. Unfortunately, these structures are difficult to detect because they are low surface brightness features so deep observations are needed. Upcoming surveys promise several orders of magnitude increase in depth and sky coverage, for which automated methods for tidal feature detection will become mandatory. We test the ability of a convolutional neural network to reproduce human visual classifications for tidal detections.

First author: Oliver Müller Dark matter clusters on all scales, therefore it is expected that even substructure should host its own substructure. Using the Extragalactic Distance Database, we searched for dwarf galaxy satellites of dwarf galaxies, i.e. satellite-of-satellite galaxies, corresponding to these substructures-of-substructure. Going through HST data of 117 dwarf galaxies, we report the discovery of a dwarf galaxy around the ultra-diffuse M96 companion M96-DF6 at 10 Mpc. Modelling its structural parameters, we find that it is an ultra-faint dwarf galaxy which is 135 times fainter than its host.

First author: Matthew J. Hayes We develop a new method to determine the distance between a galaxy and a foreground screen of atomic hydrogen. In a partially neutral universe, and under the assumption of spherical symmetry, this equates to the radius of a ionized ‘bubble’ (Rbub) surrounding the galaxy. The method requires an observed Lya equivalent width, velocity offset from systemic, and an input Lya profile for which we adopt scaled versions of the profiles observed in low-z galaxies.

First author: Brenda L. Frye The massive galaxy cluster El Gordo ($z=0.87$) imprints multitudes of gravitationally lensed arcs onto James Webb Space Telescope (JWST) Near-Infrared Camera (NIRCam) images. Eight bands of NIRCam imaging were obtained in the Prime Extragalactic Areas for Reionization and Lensing Science (PEARLS) program (GTO #1176). PSF-matched photometry across a suite of Hubble Space Telescope (HST) and NIRCam filters gives new photometric redshifts. We confirm 54 known image multiplicities and find two new ones and construct a lens model based on the light-traces-mass method.

First author: Jun-Sung Moon Galaxy spins are believed to retain initially acquired tendency of being aligned with the intermediate principal axes of the linear tidal field, which disseminates a prospect of using them as a probe of the early universe physics. This roseate prospect, however, is contingent upon the key assumption that the observable stellar spins of the present galaxies measured at inner radii have the same alignment tendency toward the initial tidal field as their dark matter counterparts measured at virial limits.

First author: Matteo Foglieni The large scale limit of the galaxy power spectrum provides a unique window into the early Universe through a possible detection of scale dependent bias produced by Primordial Non Gaussianities. On such large scales, relativistic effects could become important and, potentially, be confused for a primordial signal. In this work we provide the first consistent estimate of such effects in the observed galaxy power spectrum, and discuss their possible degeneracy with local Primordial Non Gaussianities.

First author: Christos Panagiotou While the vast majority of Tidal Disruption Events (TDEs) has been identified by wide-field sky surveys in the optical and X-ray bands, recent studies indicate that a considerable fraction of TDEs may be dust obscured, and thus preferentially detected in the infrared (IR) wavebands. In this Letter, we present the discovery of a luminous mid-IR nuclear flare (termed WTP 14adbjsh) identified in a systematic transient search of archival images from the NEOWISE mid-IR survey.

First author: Yuta Tashima Studies of the three-dimensional (3D) structures of galactic magnetic fields are now entering a new era, with broadband, highly sensitive radio observations and new analysis methods. To reveal the magnetic field configuration from the observed value integrated along the line of sight, it is necessary to derive an appropriate model that can reproduce the observational characteristics. We aim to clarify the relationship between the radiation field and the spatial distribution of physical quantities through pseudo-observations using global 3D magnetohydrodynamics (MHD) simulation results.