arXiv subjects

Cameron Leahy

Publications and source records attributed to Cameron Leahy.

3 recordsLinked to original sources

arXiv2026

The Curious Case of Centaurus A II: 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↗

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↗

arXiv2022

AstroSat/UVIT Cluster Photometry in the Northern Disk of M31

The Andromeda Galaxy (M31) is an object of ongoing study with the Ultraviolet Imaging Telescope (UVIT) on AstroSat. UVIT FUV and NUV photometry is carried out here for a set of 239 clusters in the NE disk and bulge of M31 which overlap with the HST/PHAT survey. Padova stellar models were applied to derive ages, masses, metallicities and extinctions for 170 clusters. The ages show a narrow peak at $\sim$4 Myr and a broad peak around 100 Myr. log(Z/Z$_{\odot}$) values are mostly between $-0.3$ and $+0.3$. The 7 clusters in the bulge are low metallicity and high mass. Most clusters are in the spiral arms and have metallicities in the range noted above. The youngest clusters are mostly high metallicity and are concentrated along the brightest parts of the spiral arms. The UVIT FUV and NUV data are sensitive to young stars and detect a new metal rich peak in star formation in the disk at age $\sim4$ Myr.

astro-ph.GA↗