Showing papers by "Warrick J. Couch published in 2021"

The two formation pathways of S0 galaxies

Abstract: Despite their ubiquity throughout the Universe, the formation of S0 galaxies remains uncertain. Recent observations have revealed that S0 galaxies make up a diverse population that is difficult to explain with a single formation pathway, suggesting that the picture of how these galaxies form is more complicated than originally envisioned. Here, we take advantage of the latest hydrodynamical cosmological simulations and follow up these studies with an investigation into the formation histories of S0s in IllustrisTNG. We first classify IllustrisTNG galaxies in a way that is fully consistent with the observations, and reproduce the observed photometric and environmental distributions seen for the S0 population. We then trace the formation histories of S0 galaxies back through time, identifying two main distinct pathways: those that experienced gas stripping via group infalls (37 per cent of S0s) or significant merger events (57 per cent). We find that those forming via mergers feature a transient star-forming ring, whose present-day occurrence rate matches observations. We find that these formation pathways together can reproduce the range in rotational support in observed S0s, concluding that there are two main formation pathways for S0 galaxies.

The SLUGGS survey: Combining stars, globular clusters, and planetary nebulae to understand the assembly history of early-type galaxies from their large radii kinematics

Abstract: DF, WC, KB, and AD acknowledge support from the Australian Research Council under Discovery Project 170102344. AFM has received financial support through the Postdoctoral Junior Leader Fellowship Programme from “la Caixa” Foundation(LCF/BQ/LI18/11630007). AJR was supported by National Science Foundation grant AST-1616710 and by a Research Corporation for Science Advancement Cottrell Scholar.

A photometric and kinematic analysis of UDG1137+16 (dw1137+16): Probing ultradiffuse galaxy formation in a group environment

Abstract: Some of the data presented herein were obtained at the W M Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration The Observatory was made possible by the generous financial support of the W M Keck Foundation The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community We are most fortunate to have the opportunity to conduct observations from this mountain JSG acknowledges financial support received through a Swinburne University Postgraduate Research Award throughout the creation of this work DAF thanks the ARC for financial support via DP160101608 AFM has received financial support through the Post-doctoral Junior Leader Fellowship Programme from ‘La Caixa’ Banking Foundation (LCF/BQ/LI18/11630007) JPB gratefully acknowledges support from National Science foundation grants AST-1518294 and AST-1616598 BTD acknowledges supports from a Spanish postdoctoral fellowship ‘Ayudas 1265 para la atraccion del talento investigador Modalidad 2: jovenes investigadores’ funded by Comunidad de Madrid under grant number 2016-T2/TIC-2039 and from the grant ‘High-resolution, multiband analysis of galaxy centers (HiMAGC)’ with reference number PR65/19-22417 financed by Comunidad de Madrid and Universidad Complutense de Madrid JR acknowledge financial support from the grants AYA2015-65973-C3-1-R and RTI2018-096228-B-C31 (MINECO/FEDER, UE), as well as from the State Agency for Research of the Spanish MCIU through the ‘Center of Excellence Severo Ochoa’ award to the Instituto de Astrofisica de Andalucia (SEV-2017-0709)

Using the EAGLE simulations to elucidate the origin of disc surface brightness profile breaks as a function of mass and environment

Abstract: We analyse the surface brightness profiles of disc-type galaxies in the EAGLE simulations in order to investigate the effects of galaxy mass and environment on galaxy profile types. Following observational works, we classify the simulated galaxies by their disc surface brightness profiles into single exponential (Type I), truncated (Type II) and anti-truncated (Type III) profiles. In agreement with previous observation and theoretical work, we find that Type II discs result from truncated star-forming discs that drive radial gradients in the stellar populations. In contrast, Type III profiles result from galaxy mergers, extended star-forming discs or the late formation of a steeper, inner disc. We find that the EAGLE simulations qualitatively reproduce the observed trends found between profile type frequency and galaxy mass, morphology and environment, such as the fraction of Type III galaxies increasing with galaxy mass, and the the fraction of Type II galaxies increasing with Hubble type. We investigate the lower incidence of Type II galaxies in galaxy clusters, finding, in a striking similarity to observed galaxies, that almost no S0-like galaxies in clusters have Type II profiles. Similarly, the fraction of Type II profiles for disc-dominated galaxies in clusters is significantly decreased relative to field galaxies. This difference between field and cluster galaxies is driven by star formation quenching. Following the cessation of star formation upon entering a galaxy cluster, the young stellar populations of Type II galaxies simply fade, leaving behind Type I galaxies.

Ultra-Diffuse Galaxies in the Perseus Cluster: Comparing Galaxy Properties with Globular Cluster System Richness

Abstract: It is clear that within the class of ultra-diffuse galaxies (UDGs) there is an extreme range in the richness of their associated globular cluster (GC) systems. Here, we report the structural properties of five UDGs in the Perseus cluster based on deep Subaru / Hyper Suprime-Cam imaging. Three appear GC-poor and two appear GC-rich. One of our sample, PUDG\_R24, appears to be undergoing quenching and is expected to fade into the UDG regime within the next $\sim0.5$ Gyr. We target this sample with Keck Cosmic Web Imager (KCWI) spectroscopy to investigate differences in their dark matter halos, as expected from their differing GC content. Our spectroscopy measures both recessional velocities, confirming Perseus cluster membership, and stellar velocity dispersions, to measure dynamical masses within their half-light radius. We supplement our data with that from the literature to examine trends in galaxy parameters with GC system richness. We do not find the correlation between GC numbers and UDG phase space positioning expected if GC-rich UDGs environmentally quench at high redshift. We do find GC-rich UDGs to have higher velocity dispersions than GC-poor UDGs on average, resulting in greater dynamical mass within the half-light radius. This agrees with the first order expectation that GC-rich UDGs have higher halo masses than GC-poor UDGs.

A new method to detect globular clusters with the S-PLUS survey

Abstract: In this paper, we describe a new method to select globular cluster (GC) candidates, including galaxy subtraction with unsharp masking, template fitting techniques and the inclusion of Gaia's proper motions. We report the use of the 12-band photometric system of S-PLUS to determine radial velocities and stellar populations of GCs around nearby galaxies. Specifically, we assess the effectiveness of identifying GCs around nearby and massive galaxies (D $ 200$ km/s) in a multi-band survey such as S-PLUS by using spectroscopically confirmed GCs and literature GC candidate lists around the bright central galaxy in the Fornax cluster, NGC 1399 (D = 19 Mpc), and the isolated lenticular galaxy NGC 3115 (D = 9.4 Mpc). Despite the shallow survey depth, that limits the present work to $r < 21.3$ mag, we measure reliable photometry and perform robust SED fitting for a sample of 115 GCs around NGC 1399 and 42 GCs around NGC 3115, recovering radial velocities, ages, and metallicities for the GC populations.