Physical Sciences and Mathematics Commons^™

Delving Deep: A Population Of Extremely Dusty Dwarfs Observed By Jwst, L. Bisigello, G. Gandolfi, A. Grazian, G. Rodighiero, L. Costantin, A. R. Cooray, A. Feltre, C. Gruppioni, N. P. Hathi, Benne W. Holwerda, A. M. Koekemoer, R. A. Lucas, J. A. Newman, P. G. Pérez-González, L. Y. A. Yung, A. De La Vega, P. Arrabal Haro, M. B. Bagley, M. Dickinson, S. L. Finkelstein, J. S. Kartaltepe, C. Papovich, N. Pirzkal, S. Wilkins

Faculty Scholarship

Aims. We take advantage of the NIRCam photometric observations available as part of the Cosmic Evolution Early Release Science survey (CEERS) to identify and analyse very red sources in an effort to discover very dusty star forming galaxies. Methods. We select red galaxies as objects with a S / N > 3 at 4.4 μm and a S / N < 2 in all JWST and HST filters at λ ≤ 2 μm, which corresponds to [ F 200 W ]−[ F 444 W ]> 1.2 considering CEERS depths. This selection is ideal to identify very dusty ( A V > 1 mag) galaxies with stellar masses between 10 6 and 10 10 M ⊙ at z < 5, more massive dusty galaxies at z = 5 − 18 and galaxies at z > 18 due to the Lyman absorption, independently of their dust …

The Loneliest Galaxies In The Universe: A Gama And Galaxy Zoo Study On Void Galaxy Morphology, Lori E. Porter, Benne Holwerda, Sandor Kruk, Maritza Lara-López, Kevin A. Pimbblet, Christopher P A Henry, Sarah Casura, Lee S. Kelvin

Faculty Scholarship

The large-scale structure of the Universe is comprised of galaxy filaments, tendrils, and voids. The majority of the Universe’s volume is taken up by these voids, which exist as underdense, but not empty, regions. The galaxies found inside these voids are expected to be some of the most isolated objects in the Universe. This study, using the Galaxy and Mass Assembly (GAMA) and Galaxy Zoo surveys, aims to investigate basic physical properties and morphology of void galaxies versus field (filament and tendril) galaxies. We use void galaxies with stellar masses (⁠M∗" role="presentation" style="box-sizing: border-box; margin: 0px; padding: 0px; border: 0px; …

Gama/Devils: Cosmic Star Formation And Agn Activity Over 12.5 Billion Years, Jordan C J D’Silva, Simon P. Driver, Claudia D P Lagos, Aaron S G Robotham, Sabine Bellstedt, Luke J M Davies, Jessica E. Thorne, Joss Bland-Hawthorn, Matias Bravo, Benne Holwerda, Steven Phillipps, Nick Seymour, Malgorzata Siudek, Rogier A. Windhorst

Faculty Scholarship

We use the Galaxy and Mass Assembly (GAMA) and the Deep Extragalactic Visible Legacy Survey (DEVILS) observational data sets to calculate the cosmic star formation rate (SFR) and active galactic nuclei (AGN) bolometric luminosity history (CSFH/CAGNH) over the last 12.5 billion years. SFRs and AGN bolometric luminosities were derived using the spectral energy distribution fitting code ProSpect, which includes an AGN prescription to self consistently model the contribution from both AGN and stellar emission to the observed rest-frame ultra-violet to far-infrared photometry. We find that both the CSFH and CAGNH evolve similarly, rising in the early Universe up to a …

Galaxy And Mass Assembly (Gama): Comparing Visually And Spectroscopically Identified Galaxy Merger Samples, Alice Desmons, Sarah Brough, Cristina Martínez-Lombilla, Roberto De Propris, Benne Holwerda, Ángel R. López-Sánchez

Faculty Scholarship

We conduct a comparison of the merging galaxy populations detected by a sample of visual identification of tidal features around galaxies as well as spectroscopically detected close pairs of galaxies to determine whether our method of selecting merging galaxies biases our understanding of galaxy interactions. Our volume-limited parent sample consists of 852 galaxies from the Galaxy And Mass Assembly (GAMA) survey in the redshift range 0.04 ≤ z ≤ 0.20 and stellar mass range 9.50 ≤ log 10(M⋆/M⊙)≤ 11.0" role="presentation" style="box-sizing: border-box; margin: 0px; padding: 0px; border: 0px; font-variant: inherit; font-stretch: inherit; line-height: normal; font-family: inherit; font-optical-sizing: inherit; font-kerning: inherit; …

Red Riding On Hood: Exploring How Galaxy Colour Depends On Environment, Pankaj C. Bhambhani, Ivan K. Baldry, Sarah Brough, Alexander D. Hill, M A. Lara-Lopez, J Loveday, Benne Holwerda

Faculty Scholarship

Galaxy populations are known to exhibit a strong colour bimodality, corresponding to blue star-forming and red quiescent subpopulations. The relative abundance of the two populations has been found to vary with stellar mass and environment. In this paper, we explore the effect of environment considering different types of measurements. We choose a sample of 49 911 galaxies with 0.05 < z < 0.18 from the Galaxy And Mass Assembly survey. We study the dependence of the fraction of red galaxies on different measures of the local environment as well as the large-scale `geometric’ environment defined by density gradients in the surrounding cosmic web. We find that the red galaxy fraction varies with the environment at fixed stellar mass. The red fraction depends more strongly on local environmental measures than on large-scale geometric environment measures. By comparing the different environmental densities, we show that no density measurement fully explains the observed environmental red fraction variation, suggesting the different measures of environmental density contain different information. We test whether the local environmental measures, when combined together, can explain all the observed environmental red fraction variation. The geometric environment has a small residual effect, and this effect is larger for voids than any other type of geometric environment. This could provide a test of the physics applied to cosmological-scale galaxy evolution simulations as it combines large-scale effects with local environmental impact.

Wallaby Pilot Survey: H I Gas Kinematics Of Galaxy Pairs In Cluster Environment, Shin-Jeong Kim, Se-Heon Oh, Jing Wang, Lister Staveley-Smith, Bärbel S. Koribalski, Minsu Kim, Hye-Jin Park, Shinna Kim, Kristine Spekkens, Juan P. Madrid

Physics and Astronomy Faculty Publications and Presentations

We examine the H I gas kinematics of galaxy pairs in two clusters and a group using Australian Square Kilometre Array Pathfinder (ASKAP) WALLABY pilot survey observations. We compare the H I properties of galaxy pair candidates in the Hydra I and Norma clusters, and the NGC 4636 group, with those of non-paired control galaxies selected in the same fields. We perform H I profile decomposition of the sample galaxies using a tool, BAYGAUD, which allows us to deblend a line-of-sight velocity profile with an optimal number of Gaussian components. We construct H I superprofiles of the sample galaxies via …

Modelling Strong Lenses From Wide-Field Ground-Based Observations In Kids And Gama, Shawn Knabel, Benne Holwerda, J Nightingale, T Treu, M Bilicki, S Brough, S Driver, L Finnerty, L Haberzettl, S Hegde, A M. Hopkins, K Kuijken, J Liske, A K. Pimblett, R C. Steele, A H. Wright

Faculty Scholarship

Despite the success of galaxy-scale strong gravitational lens studies with Hubble-quality imaging, a number of well-studied strong lenses remains small. As a result, robust comparisons of the lens models to theoretical predictions are difficult. This motivates our application of automated Bayesian lens modelling methods to observations from public data releases of overlapping large ground-based imaging and spectroscopic surveys: Kilo-Degree Survey (KiDS) and Galaxy and Mass Assembly (GAMA), respectively. We use the open-source lens modelling software PYAUTOLENS to perform our analysis. We demonstrate the feasibility of strong lens modelling with large-survey data at lower resolution as a complementary avenue to studies …

Hsc-Clauds Survey: The Star Formation Rate Functions Since Z  ∼  2 And Comparison With Hydrodynamical Simulations, V. Picouet, S. Arnouts, E. Le Floc'h, T. Mountard, K. Kraljic, O. Illbert, M. Sawicki, G. Desprez, C. Laigle, D. Schiminovich, S. De La Torre, S. Gwyn, H. J. Mccracken, Y. Dobois, R. Davé, S. Toft, J. R. Weaver, M. Shuntov, O. B. Kauffmann

Astronomy Department Faculty Publication Series

Context. Star formation rate functions (SFRFs) give an instantaneous view of the distribution of star formation rates (SFRs) in galaxies at different epochs. They are a complementary and more stringent test for models than the galaxy stellar mass function, which gives an integrated view of the past star formation activity. However, the exploration of SFRFs has been limited thus far due to difficulties in assessing the SFR from observed quantities and probing the SFRF over a wide range of SFRs.

Aims. We overcome these limitations thanks to an original method that predicts the infrared luminosity from the rest-frame UV/optical color …

Galaxy And Mass Assembly (Gama): Extended Intragroup Light In A Group At Z = 0.2 From Deep Hyper Suprime-Cam Images, Cristina Martínez-Lombilla, Sarah Brough, Mireia Montes, Roberto Baena-Gallé, Mohammad Akhlaghi, Raúl Infante-Sainz, Simon P. Driver, Benne W. Holwerda, Kevin A. Pimbblet, Aaron S G Robotham

Faculty Scholarship

We present a pilot study to assess the potential of Hyper Suprime-Cam Public Data Release 2 (HSC-PDR2) images for the analysis of extended faint structures within groups of galaxies. We examine the intragroup light (IGL) of the group 400138 (M_dyn = 1.3 ± 0.5 × 1013 M_⊙, z ∼ 0.2) from the Galaxy And Mass Assembly (GAMA) survey using Hyper Suprime-Cam Subaru Strategic Program Public Data Release 2 (HSC-SSP PDR2) images in g, r, and i bands. We present the most extended IGL measurement to date, reaching down to μglim=30.76" role="presentation" style="box-sizing: border-box; margin: 0px; …

Wallaby Pilot Survey: Hi Gas Kinematics Of Galaxy Pairs In Cluster Environment, Shin-Jeong Kim, Minsu Kim, Hye-Jin Park, Shinna Kim, Bigiel Frank, Helga Denes, Bi-Qing For, Peter Kamphuis, Se-Heon Oh, Benne Holwerda, Kristen Mcquinn, Juan Madrid, Ahmed Elagali, Gerhardt R. Meurer, Kristine Spekkens, Lister Staveley-Smith, Barbara Catinella, Nathan Deg, Karen Lee-Waddell, Jing Wang, Lourdes Verdes-Montenegro, Ivy Wong, Jonghwan Rhee

Faculty Scholarship

We examine the H I gas kinematics of galaxy pairs in two clusters and a group using Australian Square Kilometre Array Pathfinder (ASKAP) WALLABY pilot survey observations. We compare the H I properties of galaxy pair candidates in the Hydra I and Norma clusters, and the NGC 4636 group, with those of non-paired control galaxies selected in the same fields. We perform H I profile decomposition of the sample galaxies using a tool, BAYGAUD which allows us to de-blend a line-of-sight velocity profile with an optimal number of Gaussian components. We construct H I super-profiles of the sample galaxies via …

Devils: Cosmic Evolution Of Sed-Derived Metallicities And Their Connection To Star Formation Histories, Jessica E. Thorne, Aaron S G Robotham, Sabine Bellstedt, Luke J M Davies, Robin H W Cook, Luca Cortese, Benne Holwerda, Steven Phillipps, Malgorzata Siudek

Faculty Scholarship

Gas-phase metallicities of galaxies are typically measured through auroral or nebular emission lines, but metallicity also leaves an imprint on the overall spectral energy distribution (SED) of a galaxy and can be estimated through SED fitting. We use the PROSPECT SED fitting code with a flexible parametric star formation history and an evolving metallicity history to self-consistently measure metallicities, stellar mass, and other galaxy properties for 90 000 galaxies from the Deep Extragalactic VIsible Legacy Survey (DEVILS) and Galaxy and Mass Assembly (GAMA) survey. We use these to trace the evolution of the mass–metallicity relation (MZR) and show that the …

Galaxy And Mass Assembly: Galaxy Morphology In The Green Valley, Prominent Rings, And Looser Spiral Arms, Dominic Smith, Lutz Haberzettl, L E. Porter, Ren Porter-Temple, Christopher P A Henry, Benne Holwerda, Á R. López-Sánchez, Steven Phillipps, Alister W. Graham, Sarah Brough, Kevin A. Pimbblet, Jochen Liske, Lee S. Kelvin, Clayton D. Robertson, Wade Roemer, Michael Walmsley, David O’Ryan, Tobias Géron

Faculty Scholarship

Galaxies broadly fall into two categories: star-forming (blue) galaxies and quiescent (red) galaxies. In between, one finds the less populated “green valley". Some of these galaxies are suspected to be in the process of ceasing their star-formation through a gradual exhaustion of gas supply or already dead and are experiencing a rejuvenation of star-formation through fuel injection. We use the Galaxy And Mass Assembly database and the Galaxy Zoo citizen science morphological estimates to compare the morphology of galaxies in the green valley against those in the red sequence and blue cloud. Our goal is to examine the structural differences …

Deep Investigation Of Neutral Gas Origins (Dingo): Hi Stacking Experiments With Early Science Data, Jonghwan Rhee, Richard Dodson, Kristóf Rozgonyi, Sarah Brough, Benne Holwerda, Simon Driver, Attila Popping, Sambit Roychowdhury, Sabine Bellstedt, Michael J. I. Brown, Lister Staveley-Smith, Ivan Baldry, Angel Lopez-Sanchez, Martin Meyer, Elizabeth Mahony, Aaron Robotham, Andrew Hopkins, Karen Lee-Waddell

Faculty Scholarship

We present early science results from Deep Investigation of Neutral Gas Origins (DINGO), an H I survey using the Australian Square Kilometre Array Pathfinder (ASKAP). Using ASKAP subarrays available during its commissioning phase, DINGO early science data were taken over ∼60 deg2 of the Galaxy And Mass Assembly (GAMA) 23 h region with 35.5 h integration time. We make direct detections of six known and one new sources at z < 0.01. Using H I spectral stacking, we investigate the H I gas content of galaxies at 0.04 < z < 0.09 for different galaxy colours. The results show that galaxy morphology based on optical colour is strongly linked to H I gas properties. To examine environmental impacts on the H I gas content of galaxies, three subsamples are made based on the GAMA group catalogue. The average H I mass of group central galaxies is larger than those of satellite and isolated galaxies, but with a lower H I gas fraction. We derive a variety of H I scaling relations for physical properties of our sample, including stellar mass, stellar mass surface density, NUV − r colour, specific star formation rate, and halo mass. We find that the derived H I scaling relations are comparable to other published results, with consistent trends also observed to ∼0.5 dex lower limits in stellar mass and stellar surface density. The cosmic H I densities derived from our data are consistent with other published values at similar redshifts. DINGO early science highlights the power of H I spectral stacking techniques with ASKAP

Bending Waves Excited By Irregular Gas Inflow Along Warps, Tigran Khachaturyants, Leandro Beraldo E Silva, Victor P. Debattista, Kathryne J. Daniel

Physics Faculty Research and Scholarship

Gaia has revealed clear evidence of bending waves in the vertical kinematics of stars in the solar neighbourhood. We study bending waves in two simulations, one warped, with the warp due to misaligned gas inflow, and the other unwarped. We find slow, retrograde bending waves in both models, with the ones in the warped model having larger amplitudes. We also find fast, prograde bending waves. Prograde bending waves in the unwarped model are very weak, in agreement with the expectation that these waves should decay on short, approximately crossing, time-scales, due to strong winding. However, prograde bending waves are much …

Wallaby Pre-Pilot Survey: Two Dark Clouds In The Vicinity Of Ngc 1395, O. I. Wong, A. R. H. Stevens, B. Q. For, Tobias Westmeier, M. Dixon, S. -H. Oh, G. I. G. Jozsa, T. N. Reynolds, K. Lee-Waddell, Juan P. Madrid

Physics and Astronomy Faculty Publications and Presentations

We present the Australian Square Kilometre Array Pathfinder (ASKAP) WALLABY pre-pilot observations of two ‘dark’ HI sources (with HI masses of a few times 108 M⊙ and no known stellar counterpart) that reside within 363 kpc of NGC 1395, the most massive early-type galaxy in the Eridanus group of galaxies. We investigate whether these ‘dark’ HI sources have resulted from past tidal interactions or whether they are an extreme class of low surface brightness galaxies. Our results suggest that both scenarios are possible, and not mutually exclusive. The two ‘dark’ HI sources are compact, reside in relative isolation and are …

Galaxy And Mass Assembly: Group And Field Galaxy Morphologies In The Star-Formation Rate - Stellar Mass Plane, W. J. Pearson, L. Wang, S. Brough, Benne Holwerda, A. M. Hopkins, J. Loveday

Faculty Scholarship

Aims. We study the environment in which a galaxy lies (i.e. field or group) and its connection with the morphology of the galaxy. This is done by examining the distribution of parametric and non-parametric statistics across the star-formation rate (SFR) - stellar mass (M?) plane and studying how these distributions change with the environment in the local universe (z < 0.15). Methods. We determine the concentration (C), Gini, M20, asymmetry, Gini-M20 bulge statistic (GMB), 50% light radius (r50), total Sérsic index, and bulge Sérsic index (nBulge) for galaxies from the Galaxy and Mass Assembly (GAMA) survey using optical images from the Kilo Degree Survey. We determine the galaxy environment using the GAMA group catalogue and split the galaxies into field or group galaxies. The group galaxies are further divided by the group halo mass (Mh) - 11 ≤ log(Mh /M*) < 12, 12 ≤ log(Mh /M*) < 13, and 13 ≤ log(Mh /M*) < 14 - and into central and satellite galaxies. The galaxies in each of these samples are then placed onto the SFR-M? plane, and each parameter is used as a third dimension. We fit the resulting distributions for each parameter in each sample using two two-dimensional Gaussian distributions: one for star-forming galaxies and one for quiescent galaxies. The coefficients of these Gaussian fits are then compared between environments. Results. Using C and r50, we find that galaxies typically become larger as the group mass increases. This change is greater for larger galaxies. There is no indication that galaxies are typically more or less clumpy as the environment changes. Using GMB and nBulge , we see that the star-forming galaxies do not become more bulge or disk dominated as the group mass changes. Asymmetry does not appear to be greatly influenced by environment.

Galaxy And Mass Assembly: Luminosity And Stellar Mass Functions In Gama Groups, J. A. Vazquez-Mata, J. Loveday, S. D. Riggs, I. K. Baldry, L. J.M. Davies, A. S.G. Robotham, Benne W. Holwerda, M. J.I. Brown, M. E. Cluver, L. Wang, M. Alpaslan, J. Bland-Hawthorn, S. Brough, S. P. Driver, A. M. Hopkins, E. N. Taylor, A. H. Wright

Faculty Scholarship

How do galaxy properties (such as stellar mass, luminosity, star formation rate, and morphology) and their evolution depend on the mass of their host dark matter halo? Using the Galaxy and Mass Assembly group catalogue, we address this question by exploring the dependence on host halo mass of the luminosity function (LF) and stellar mass function (SMF) for grouped galaxies subdivided by colour, morphology, and central/satellite. We find that spheroidal galaxies in particular dominate the bright and massive ends of the LF and SMF, respectively. More massive haloes host more massive and more luminous central galaxies. The satellites LF and …

Galaxy And Mass Assembly (Gama): Defining Passive Galaxy Samples And Searching For The Uv Upturn, S. Phillipps, S. S. Ali, M. N. Bremer, R. De Propris, A. E. Sansom, M. E. Cluver, M. Alpaslan, S. Brough, M. J.I. Brown, L. J.M. Davies, S. P. Driver, M. W. Grootes, Benne W. Holwerda, A. M. Hopkins, P. A. James, K. Pimbblet, A. S.G. Robotham, E. N. Taylor, L. Wang

Faculty Scholarship

We use data from the GAMA and GALEX surveys to demonstrate that the UV upturn, an unexpected excess of ultraviolet flux from a hot stellar component, seen in the spectra of many early-type galaxies, arises from processes internal to individual galaxies with no measurable influence from the galaxies' larger environment. We first define a clean sample of passive galaxies without a significant contribution to their UV flux from low-level star formation. We confirm that galaxies with the optical colours of red sequence galaxies often have signs of residual star formation, which, without other information, would prevent a convincing demonstration of …

Galaxy And Mass Assembly (Gama): Properties And Evolution Of Red Spiral Galaxies, Smriti Mahajan, Kriti Kamal Gupta, Rahul Rana, M. J.I. Brown, S. Phillipps, Joss Bland-Hawthorn, M. N. Bremer, S. Brough, Benne W. Holwerda, A. M. Hopkins, J. Loveday, Kevin Pimbblet, Lingyu Wang

Faculty Scholarship

We use multiwavelength data from the Galaxy And Mass Assembly (GAMA) survey to explore the cause of red optical colours in nearby (0.002 < z < 0.06) spiral galaxies. We show that the colours of red spiral galaxies are a direct consequence of some environment-related mechanism(s) that has removed dust and gas, leading to a lower star formation rate. We conclude that this process acts on long time-scales (several Gyr) due to a lack of morphological transformation associated with the transition in optical colour. The specific star formation rate (sSFR) and dust-to-stellar mass ratio of red spiral galaxies is found to be statistically lower than blue spiral galaxies. On the other hand, red spirals are on average 0.9 dex more massive, and reside in environments 2.6 times denser than their blue counterparts. We find no evidence of excessive nuclear activity, or higher inclination angles to support these as the major causes for the red optical colours seen in ≳47 per cent of all spirals in our sample. Furthermore, for a small subsample of our spiral galaxies that are detected in H I, we find that the SFR of gas-rich red spiral galaxies is lower by ∼1 dex than their blue counterparts.

Effect Of Galaxy Mergers On Star-Formation Rates, W. J. Pearson, L. Wang, M. Alpaslan, I. Baldry, M. Bilicki, M. J.I. Brown, M. W. Grootes, Benne W. Holwerda, T. D. Kitching, S. Kruk, F. F.S. Van Der Tak

Faculty Scholarship

Context. Galaxy mergers and interactions are an integral part of our basic understanding of how galaxies grow and evolve over time. However, the effect that galaxy mergers have on star-formation rates (SFRs) is contested, with observations of galaxy mergers showing reduced, enhanced, and highly enhanced star formation. Aims. We aim to determine the effect of galaxy mergers on the SFR of galaxies using statistically large samples of galaxies, totalling over 200 000, which is over a large redshift range from 0.0 to 4.0. Methods. We trained and used convolutional neural networks to create binary merger identifications (merger or non-merger) in …

Default Parallels: The Science Potential Of Jwst Parallel Observations During Tso Primary Observations, Benne W. Holwerda, Jonathan Fraine, Nelly Mouawad, Joanna S. Bridge

Faculty Scholarship

The James Webb Space Telescope (JWST) will observe several stars for long cumulative durations while pursuing exoplanets as primary science targets for both Guaranteed Time Observations (GTO) and very likely General Observer (GO) programs. Here we argue in favor of an automatic default parallel program to observe, e.g., using the F200W/F277W filters or grism of NIRCAM/NIRISS in order to find high redshift (z (Formula Presented) 10) galaxies, cool red/brown dwarf substellar objects, solar system objects, and observations of serendipitous planetary transits. We argue here the need for automated exploratory astrophysical observations with unused JWST instruments during these long-duration exoplanet observations. …

The Super Eight Galaxies: Properties Of A Sample Of Very Bright Galaxies At 7 < Z < 8, Joanna S. Bridge, Benne W. Holwerda, Mauro Stefanon, Rychard J. Bouwens, Pascal A. Oesch, Michele Trenti, Stephanie R. Bernard, Larry D. Bradley, Garth D. Illingworth, Samir Kusmic, Dan Magee, Takahiro Morishita, Guido W. Roberts-Borsani, Renske Smit, Rebecca L. Steele

Faculty Scholarship

We present the Super Eight galaxies - a set of very luminous, high-redshift (7.1 < z < 8.0) galaxy candidates found in the Brightest of Reionizing Galaxies (BoRG) Survey fields. The original sample includes eight galaxies that are Y-band dropout objects with H-band magnitudes of m H < 25.5. Four of these objects were originally reported in Calvi et al. Combining new Hubble Space Telescope (HST) WFC3/F814W imaging and Spitzer IRAC data with archival imaging from BoRG and other surveys, we explore the properties of these galaxies. Photometric redshift fitting places six of these galaxies in the redshift range of 7.1 < z < 8.0, resulting in three new high-redshift galaxies and confirming three of the four high-redshift galaxy candidates from Calvi et al. We calculate the half-light radii of the Super Eight galaxies using the HST F160W filter and find that the Super Eight sizes are in line with the typical evolution of size with redshift. The Super Eights have a mean mass of log (M ∗/M o) ∼10, which is typical for sources in this luminosity range. Finally, we place our sample on the UV z ∼ 8 luminosity function and find that the Super Eight number density is consistent with other surveys in this magnitude and redshift range.

Virgo’S Intracluster Globular Clusters As Seen By The Advanced Camera For Surveys, Benjamin F. Williams, Robin Ciardullo, Ted Von Hippel, Et Al.

Ted von Hippel

We report the discovery of four candidate intracluster globular clusters (IGCs) in a single deepHST ACS field of the Virgo Cluster. We show that each cluster is roughly spherical, has a magnitude near the peak of the Virgo globular cluster luminosity function, has a radial profile that is best fitted by a King model, and is surrounded by an excess of point sources that have the colors and magnitudes of cluster red giant stars. Despite the fact that two of our IGC candidates have integrated colors redder than the mean of the M87 globular cluster system, we propose that …

The Metallicity Distribution Of Intracluster Stars In Virgo, Benjamin F. Willaims, Ted Von Hippel, Et Al.

Ted von Hippel

We have used the Hubble Space Telescope's Advanced Camera for Surveys (ACS) to detect and measure ~5300 stars in a single intracluster field in the Virgo Cluster. By performing F606W and F814W photometry on these stars, we have determined their metallicity distribution function and constrained the types of stars present in this portion of Virgo's intracluster space. Based on the small number of stars detected that were brighter than the red giant branch (RGB) tip, we suggest that in this region, Virgo's intracluster stars are mostly old (10 Gyr). Through analysis of the RGB stars themselves, we determine that …

Formation Of Ultra-Diffuse Galaxies In The Field And In Galaxy Groups, Fangzhou Jiang, Avishai Dekel, Jonathan Freundlich, Aaron Romanowsky, Aaron Dutton, Andrea Macciò, Arianna Di Cintio

Faculty Publications

We study ultra-diffuse galaxies (UDGs) in zoom in cosmological simulations, seeking the origin of UDGs in the field versus galaxy groups. We find that while field UDGs arise from dwarfs in a characteristic mass range by multiple episodes of supernova feedback (Di Cintio et al.), group UDGs may also form by tidal puffing up and they become quiescent by ram-pressure stripping. The field and group UDGs share similar properties, independent of distance from the group centre. Their dark-matter haloes have ordinary spin parameters and centrally dominant dark-matter cores. Their stellar components tend to have a prolate shape with a Sérsic …

New Constraints On Early-Type Galaxy Assembly From Spectroscopic Metallicities Of Globular Clusters In M87, Alexa Villaume, Aaron Romanowsky, Jean Brodie, Jay Strader

Faculty Publications

The observed characteristics of globular cluster (GC) systems, such as metallicity distributions, are commonly used to place constraints on galaxy formation models. However, obtaining reliable metallicity values is particularly difficult because of our limited means to obtain high quality spectroscopy of extragalactic GCs. Often, "color–metallicity relations" are invoked to convert easier-to-obtain photometric measurements into metallicities, but there is no consensus on what form these relations should take. In this paper we make use of multiple photometric data sets and iron metallicity values derived from applying full-spectrum stellar population synthesis models to deep Keck/LRIS spectra of 177 GCs centrally located around …

Spatially Resolved Stellar Populations And Kinematics With Kcwi: Probing The Assembly History Of The Massive Early-Type Galaxy Ngc 1407, Anna Ferré-Mateu, Duncan Forbes, Richard Mcdermid, Aaron Romanowsky, Jean Brodie

Faculty Publications

Using the newly commissioned Keck Cosmic Web Imager (KCWI) instrument on the Keck II telescope, we analyze the stellar kinematics and stellar populations of the well-studied massive early-type galaxy (ETG) NGC 1407. We obtained high signal-to-noise integral field spectra for a central and an outer (around one effective radius toward the southeast direction) pointing with integration times of just 600 s and 2400 s, respectively. We confirm the presence of a kinematically distinct core also revealed by VLT/MUSE data of the central regions. While NGC 1407 was previously found to have stellar populations characteristic of massive ETGs (with radially constant …

Extreme Chemical Abundance Ratio Suggesting An Exotic Origin For An Ultradiffuse Galaxy, Ignacio Martín-Navarro, Aaron Romanowsky, Jean Brodie, Anna Ferr´E-Mateu, Adebusola Alabi, Duncan Forbes, Margarita Sharina, Alexa Villaume, Viraj Pandya, David Martinez-Delgado

Faculty Publications

Ultradiffuse galaxies (UDGs) are a population of extended galaxies but with relatively low luminosities. The origin of these objects remains unclear, largely due to the observational challenges of the low surface brightness Universe. We present here a detailed stellar population analysis of a relatively isolated UDG, DGSAT I, based on spectroscopic data from the Keck Cosmic Web Imager integral field unit. The star formation history of DGSAT I seems to be extended, with a mean luminosity-weighted age of ∼3 Gyr, in agreement with previous photometric studies. However, we find a very high [Mg/Fe] abundance ratio, which is extreme even in …

A Second Galaxy Missing Dark Matter In The Ngc 1052, Pieter Van Dokkum, Shany Danieli, Roberto Abraham, Charlie Conroy, Aaron Romanowsky

Faculty Publications

The ultra-diffuse galaxy NGC1052-DF2 has a very low velocity dispersion, indicating that it has little or no dark matter. Here we report the discovery of a second galaxy in this class, residing in the same group. NGC1052-DF4 closely resembles NGC1052-DF2 in terms of its size, surface brightness, and morphology; has a similar distance of Dsbf =  19.9 2.8 Mpc; and also has a population of luminous globular clusters extending out to 7 kpc from the center of the galaxy. Accurate radial velocities of the diffuse galaxy light and seven of the globular clusters were obtained with the Low Resolution …

A Second Galaxy Missing Dark Matter In The Ngc 1052 Group, Pieter Van Dokkum, Shany Danieli, Roberto Abraham, Charlie Conroy, Aaron Romanowsky

Faculty Publications

The ultra-diffuse galaxy NGC1052-DF2 has a very low velocity dispersion, indicating that it has little or no dark matter. Here we report the discovery of a second galaxy in this class, residing in the same group. NGC1052-DF4closely resembles NGC1052-DF2 in terms of its size, surface brightness, and morphology; has a similar distance of Dsbf = 19.9 +/- 2.8 Mpc; and also has a population of luminous globular clusters extending out to >7 kpc from the center of the galaxy. Accurate radial velocities of the diffuse galaxy light and seven of the globular clusters were obtained with the Low Resolution Imaging …