arXiv subjects

Mia Sauda Bovill

Publications and source records attributed to Mia Sauda Bovill.

12 recordsLinked to original sources

arXiv2026

The Curious Case of Centaurus A: On the Subject of the Quenched satellites

The satellite system of Centaurus A presents a curious cosmological puzzle: while the global population is consistent with theoretical expectations, its inner regions (d<150 kpc) exhibit a deficit of luminous satellite galaxies. Using the Galacticus semi-analytic model applied to high-resolution N-body merger trees, we investigate potential quenching mechanisms to explain this trend. Our fiducial models, calibrated to the Milky Way, reproduce the overall Cen A population but overpredict the number of bright inner-halo satellites by a factor of 4 +- 1 at Mv < -15.8. We find that this is not due to statistical variance. Instead, the spatial coincidence of this deficiency with Cen A's massive, kiloparsec-scale radio lobes suggests a powerful environmental driver. We explore a range of physical scenarios, including enhanced tidal disruption, reionization quenching, and suppressed accretion into halos from the surrounding intergalactic medium. Our results indicate that AGN-driven thermal feedback at z < 5 can significantly suppress star formation in satellites, effectively truncating the bright end of the inner luminosity function. Our work suggests that the "Curious Case of Centaurus A" may provide evidence of AGN feedback within the host galaxy that regulates the survival and evolution of its dwarf galaxy satellites.

astro-ph.GA↗

arXiv2025

On the Origins of "Hostless'' Supernovae: Testing the Faint-end Galaxy Luminosity Function and Supernova Progenitors with Events in Dwarf Galaxies

We present arguments on the likely origins of supernovae without associated host galaxies from open field, non-clustered, environments. We show why it is unlikely these ``hostless'' supernovae stem from escaped hyper-velocity stars (HVS) in any appreciable numbers, especially for core-collapse supernovae. It is highly likely that hostless events arise from dwarf host galaxies too faint to be detected in their parent surveys. Several detections and numerous upper limits suggest a large number of field dwarfs, to $M_V>-14$, which themselves may be important to constraining the slope of the low-mass end of the UV luminosity function, understanding galaxy evolution, and putting $Λ$CDM into context. Moreover, the detailed study of these mass and metallicity-constrained host environments, and the variety of supernovae that occur within them, could provide more stringent constraints on the nature of progenitor systems.

astro-ph.GA↗

arXiv2024

Devouring The Centaurus A Satellites: Modeling Dwarf Galaxies with Galacticus

For the first time, systematic studies of dwarf galaxies are being conducted throughout the Local Volume, including the dwarf satellites of the nearby giant elliptical galaxy Centaurus A (NGC 5128). Given Centaurus As mass (roughly ten times larger than that of the Milky Way), AGN activity, and recent major mergers, investigating the dwarf galaxies of Centaurus A and their star formation physics is imperative. However, simulating the faintest dwarfs around a galaxy of Centaurus As mass with sufficient resolution in a hydrodynamic simulation is computationally expensive and currently infeasible. In this study, we seek to reproduce the properties of Centaurus A dwarfs using the semi-analytic model Galacticus to model dwarfs within a 700 kpc region around Centaurus A, corresponding approximately to its splashback radius. We investigate the effects of host halo mass and environment and predict observable properties of Centaurus A dwarfs using astrophysical prescriptions and parameters previously tuned to match properties of the Milky Way's satellite galaxies. This approach allows us to approximately replicate cumulative luminosity functions, and luminosity metallicity and luminosity half-light-radii relations observed in the Centaurus A satellites. We provide predictions for the velocity dispersions, and star formation histories of Centaurus A dwarfs. The agreement between our predicted star formation histories for Centaurus A dwarfs and those of the Milky Way dwarfs implies the presence of universal processes governing star formation in the dwarf galaxies. Overall, our findings shed light on the star formation physics of dwarf galaxies in the Centaurus A system, revealing insights into their properties and dependence on the host environment.

astro-ph.GA↗

arXiv2024

A comprehensive model for the formation and evolution of the faintest Milky Way dwarf satellites

In this study, we modify the semi-analytic model Galacticus in order to accurately reproduce the observed properties of dwarf galaxies in the Milky Way. We find that reproducing observational determinations of the halo occupation fraction and mass-metallicity relation for dwarf galaxies requires us to include H$_2$ cooling, an updated UV background radiation model, and to introduce a model for the metal content of the intergalactic medium. By fine-tuning various model parameters and incorporating empirical constraints, we have tailored the model to match the statistical properties of Milky Way dwarf galaxies, such as their luminosity function and size$-$mass relation. We have validated our modified semi-analytic framework by undertaking a comparative analysis of the resulting galaxy-halo connection. We predict a total of $300 ^{+75} _{-99}$ satellites with an absolute $V$-band magnitude (M$_{V}$) less than $0$ within $300$ kpc from our Milky Way-analogs. The fraction of subhalos that host a galaxy at least this bright drops to $50\%$ by a halo peak mass of $\sim 8.9 \times 10^{7}$ M$_{\odot}$, consistent with the occupation fraction inferred from the latest observations of Milky Way satellite population.

astro-ph.GA↗

arXiv2024

Kindling the First Stars II: Dependence of the Predicted PISN Rate on the Pop III Initial Mass Function

Population III (Pop III) stars formed out of metal free gas in minihalos at $z>20$. While their ignition ended the Dark Ages and begin enrichment of the IGM, their mass distribution remains unconstrained. To date, no confirmed Pop III star has been observed and their direct detection is beyond the reach of the James Webb Space Telescope (JWST) without gravitational lensing. However, a subset of massive Pop III stars end their lives in pair instability supernova (PISN). With typical energies of $\sim10^{53}$~erg, PISN light curve peaks are bright enough to be detectable by JWST and the Roman Space Telescope. The fundamental question of this work is whether or not observed PISN can be used as a diagnostic of the Pop III IMF. In this work, we use a model of the formation of the first stars to determine the dependence of PISN rates at $z~>~5$ for a range of Pop III power law IMFs ($α~=~0.2~-~2.35$) and, critically, the method by which the IMF is populated. At $z~>~15$, we predict typical rates of $10^{-2}~-~10^2$ per deg$^{2}$ per year which will produce $10^{-3}~-~0.1$/year in a single NIRCam pointing and $0.003~-~30$/year in a single Roman pointing with $0.1~-~1000$ per year detected in the HLTDS. Our work highlights that theoretical modeling of PISN rates is required if upcoming PISN studies with JWST and Roman are going to constrain the Pop III IMF.

astro-ph.GA↗

arXiv2022

Kindling the First Stars: I. Dependence of Detectability of the First Stars with JWST on the Pop III Stellar Masses

The first Pop III stars formed out of primordial, metal free gas, in minihalos at z>20, and kickstarted the cosmic processes of reionizaton and enrichment. While these stars are likely more massive than their enriched counterparts, the current unknowns of their astrophysics include; when the first Pop III stars ignited, how massive they were, and when and how the era of the first stars ended. Investigating these questions requires an exploration of a multi-dimensional parameter space, including the slope of the Pop III stellar initial mass function (IMF) and the strength of the non-ionizing UV background. In this work, we present a novel model which treats both the slope and maximum mass of Pop III stars as truly free parameters while including the physics of the fragmentation of primordial gas. Our results also hint at a non-universal Pop III IMF which is dependent on the efficiency of primordial gas fragmentation. Our relatively simple model reproduces the results from hydrodynamic simulations, but with a computational efficiency which allows us to investigate the observable differences between a wide range of potential Pop III IMFs. In addition, the evolution of the number density of Pop III stars may provide insight into the evolution of the H2 dissociating background. While the slope of the Pop III IMF does not significantly affect the predicted number density of the first stars, more top heavy IMFs produce Pop III star clusters which are 2-3 magnitudes brighter than their more bottom heavy counterparts. While the Pop III star clusters are too dim for direct detection by JWST, we find they are within the reach of gravitational lensing.

astro-ph.GA↗

arXiv2022

Devouring the Milky Way Satellites: Modeling Dwarf Galaxies with Galacticus

Dwarf galaxies are ubiquitous throughout the universe and are extremely sensitive to various forms of internal and external feedback. Over the last two decades, the census of dwarf galaxies in the Local Group and beyond has increased markedly. While hydrodynamic simulations (e.g. FIRE II, MINT Justice League) have reproduced the observed dwarf properties down to the ultra-faints, such simulations require extensive computational resources to run. In this work, we constrain the standard physical implementations in the semi-analytic model Galacticus to reproduce the observed properties of the Milky Way satellites down to the ultra-faint dwarfs found in SDSS. We run Galacticus on merger trees from our high-resolution N-body simulation of a Milky Way analog. We determine the best-fit parameters by matching the cumulative luminosity function and luminosity-metallicity relation from both observations and hydrodynamic simulations. With the correct parameters, the standard physics in Galacticus can reproduce the observed luminosity function and luminosity-metallicity relation of the Milky Way dwarfs. In addition, we find a multi-dimensional match with half-light radii, velocity dispersions and mass-to-light ratios at z = 0 down to M_V <= -6 (L >= 10^4 L_solar). In addition to successfully reproducing the properties of the z = 0 Milky Way satellite population, our modeled dwarfs have star formation histories which are consistent with those of the Local Group dwarfs.

astro-ph.GA↗

arXiv2019

Astro2020 APC White Paper: Accessible Astronomy: Policies, Practices, and Strategies to Increase Participation of Astronomers with Disabilities

(Abridged) In this white paper, we outline the major barriers to access within the educational and professional practice of astronomy. We present current best practices for inclusivity and accessibility, including classroom practices, institutional culture, support for infrastructure creation, hiring processes, and outreach initiatives. We present specific ways--beyond simple compliance with the ADA--that funding agencies, astronomers, and institutions can work together to make astronomy as a field more accessible, inclusive, and equitable. In particular, funding agencies should include the accessibility of institutions during proposal evaluation, hold institutions accountable for inaccessibility, and support efforts to gather data on the status and progress of astronomers and astronomy students with disabilities.

astro-ph.IM↗

arXiv2018

A Collection of New Dwarf Galaxies in NGC5128's Western Halo

We report the photometric properties of 16 dwarf galaxies, 15 of which are newly identified, in the Western halo of the nearby giant elliptical galaxy NGC5128. All candidates are found at projected distances $\sim\!100\!-\!225$kpc from their giant host, with luminosities $-10.82\!\leq\!M_V/{\rm mag}\!\leq\!-7.42$ and effective radii $4''\!\leq\!r_{\rm eff}\!\leq\!17''$ (or $75\!\leq\!r_{\rm eff}/{\rm pc}\!\leq\!300$ at the distance of NGC5128). We compare to other low-mass dwarf galaxies in the local universe and find them to populate the faint/compact extension of the size-luminosity relation that was previously not well-sampled by dwarf galaxies in the Centaurus A system, with optical colors similar to compact stellar systems like globular clusters and ultra-compact dwarf galaxies despite having much more diffuse morphologies. From optical $u'g'r'i'z'$ photometry, stellar masses are estimated to be $5.17\!\leq\!\log{\cal M}_\star/M_\odot\!\leq\!6.48$, with colors that show them to fall redward of the dwarf galaxy mass-metallicity relation. These colors suggest star formation histories that require some mechanism that would give rise to extra metal enrichment such as primordial formation within the halos of their giant galaxy hosts, non-primordial star formation from previously enriched gas, or extended periods of star formation leading to self-enrichment. We also report the existence of at least two sub-groups of dwarf candidates, each subtending $10-20'$ on the sky, corresponding to projected physical separations of $10\!-\!20$kpc. True physical associations of these groups, combined with their potentially extended star formation histories, would imply that they may represent dwarf galaxy groups in the early stage of interaction upon infall into a giant elliptical galaxy halo in the very nearby universe.

astro-ph.GA↗

arXiv2017

The Survey of Centaurus A's Baryonic Structures (SCABS). II. The Extended Globular Cluster System of NGC5128 and its Nearby Environment

Wide-field $u'g'r'i'z'$ Dark Energy Camera observations centred on the giant elliptical galaxy NGC5128 covering $\sim21deg^2$ are used to compile a new catalogue of $\sim3200$ globular clusters (GCs). We report 2404 new candidates, including the vast majority within $\sim140$kpc of NGC5128. We find evidence for a transition at a galactocentric radius of $R_{\rm gc}\approx55$kpc from GCs intrinsic to NGC5128 to those likely to have been accreted from dwarf galaxies or that may transition to the intra-group medium of the Centaurus A galaxy group. We fit power-law surface number density profiles of the form $Σ_{N, R_{\rm gc}}\propto R_{\rm gc}^Γ$ and find that inside the transition radius, the red GCs are more centrally concentrated than the blue, with $Γ_{\rm inner,red}\approx-1.78$ and $Γ_{\rm inner,blue}\approx-1.40$. Outside this region both profiles flatten, more dramatically for the red GCs ($Γ_{\rm outer,red}\approx-0.33$) compared to the blue ($Γ_{\rm outer,blue}\approx-0.61$), although the former is more likely to suffer contamination by background sources. The median $(g'\!-\!z')_0\!=\!1.27$mag colour of the inner red population is consistent with arising from the amalgamation of two giant galaxies each less luminous than present-day NGC5128. Both in- and out-ward of the transition radius, we find the fraction of blue GCs to dominate over the red GCs, indicating a lively history of minor-mergers. Assuming the blue GCs to originate primarily in dwarf galaxies, we model the population required to explain them, while remaining consistent with NGC5128's present-day spheroid luminosity. We find that several dozen dwarfs of luminosities $L_{dw,V}\simeq10^{6-9.3}L_{V,\odot}$, following a Schechter luminosity function with a faint-end slope of $-1.50\leqα\leq-1.25$ is favoured, many of which may have already been disrupted in NGC5128's tidal field.

astro-ph.GA↗

arXiv2016

The Survey of Centaurus A's Baryonic Structures (SCABS). I. Survey Description and Initial Source Catalogues

We present new, wide-field, optical ($u'g'r'i'z'$) Dark Energy Camera observations covering $\sim21\,{\rm deg}^2$ centred on the nearby giant elliptical galaxy NGC5128 called "The Survey of Centaurus A's Baryonic Structures" (SCABS). The data reduction and analysis procedures are described including initial source detection, photometric and astrometric calibration, image stacking, and point-spread function modelling. We estimate 50 and 90 percent, field-dependent, point-source completeness limits of at least $u'=24.08$ and $23.62$ mag (AB), $g'=22.67$ and $22.27$ mag, $r'=22.46$ and $22.00$ mag, $i'=22.05$ and $21.63$ mag, and $z'=21.71$ and $21.34$ mag. Deeper imaging in the $u'$-, $i'$- and $z'$-bands provide the fainter limits for the inner $\sim3\,{\rm deg}^2$ of the survey, and we find very stable photometric sensitivity across the entire field of view. Source catalogues are released in all filters including spatial, photometric, and morphological information for a total of $\sim5\times10^5-1.5\times10^6$ detected sources (filter-dependent). We finish with a brief discussion of potential science applications for the data including, but not limited to, upcoming works by the SCABS team.

astro-ph.GA↗

arXiv2016

The Lost Dwarfs of Centaurus A and the Formation of its Dark Globular Clusters

We present theoretical constraints for the formation of the newly discovered dark star clusters (DSCs) with high mass-to-light (M/L) ratios, from Taylor et al (2015). These compact stellar systems photometrically resemble globular clusters (GCs) but have dynamical M/L ratios of ~ 10 - 100, closer to the expectations for dwarf galaxies. The baryonic properties of the dark star clusters (DSCs) suggest their host dark matter halos likely virialized at high redshift with M > 10^8 M_sun. We use a new set of high-resolution N-body simulations of Centaurus A to determine if there is a set of z=0 subhalos whose properties are in line with these observations. While we find such a set of subhalos, when we extrapolate the dark matter density profiles into the inner 20 pc, no dark matter halo associated with Centaurus A in our simulations, at any redshift, can replicate the extremely high central mass densities of the DSCs. Among the most likely options for explaining 10^5 - 10^7 M_sun within 10 pc diameter subhalos is the presence of a central massive black hole. We, therefore, propose that the DSCs are remnant cusps of stellar systems surrounding the central black holes of dwarf galaxies which have been almost completely destroyed by interactions with Centaurus A.

astro-ph.GA↗