arXiv subjects

Lori E. Porter

Publications and source records attributed to Lori E. Porter.

5 recordsLinked to original sources

arXiv2026

What Suppresses Star Formation in Bulge-Dominated Early-Type Galaxies?

We investigate the physical origin of star formation suppression in gas-rich early-type galaxies using five high-resolution hydrodynamical idealized galaxy simulations, performed with the moving-mesh code AREPO. These simulations include one Milky Way-like galaxy and four early-type galaxies, of which one early-type galaxy is found to have significantly less star formation despite a substantial molecular gas reservoir. We apply a modified virial theorem to the overdensities in each galaxy to quantify the forces regulating their stability and thus star formation. We find evidence that, in the suppressed galaxy, strong Coriolis forces driven by elevated galactic shear may inhibit gravitational collapse. This is caused by the galaxy's high central compactness, providing a physical mechanism for the suppression of star formation that does not require the removal of molecular gas. In contrast, less compact early-type galaxies host more gravity-dominated clouds and therefore exhibit higher star formation rates. However, we find that this gravitational stability occurs without significantly increasing the classical Toomre-Q parameter, and therefore a new criterion for suppressed star formation may be needed. We also discuss the impact of our choice of overdensity scale and connections to observations of molecular clouds.

astro-ph.GA↗

arXiv2025

Simulating High-Velocity Clouds in the Observational Plane: An Initial Study with the Smith Cloud

High-velocity clouds (HVCs) may fuel future star formation in the Milky Way, but they must first survive their passage through the hot halo. While recent work has improved our understanding of the survival criterion for cloud-wind interactions, few observational comparisons exist that test this criterion. We therefore present an initial comparison of simulations with the Smith Cloud (SC; $d=$ 12.4 kpc, $l, b = 40^{\circ}, -13^{\circ}$) as mapped with the GALFA-HI survey. We use the Smith Cloud's observed properties to motivate simulations of comparable clouds in wind tunnel simulations with Enzo-E, an MHD code. For both observations and simulations, we generate moment maps, characterize turbulence through a projected first-order velocity structure function (VSF), and do the same for HI column density with a normalized autocovariance function. We explore how initial cloud conditions (such as radius, metallicity, thermal pressure, viewing angle, and distance) affect these statistics, demonstrating that the small-scale VSF is sensitive to cloud turbulence while large scales depend on cloud bulk velocity and viewing angle. We find that some simulations reproduce key observational features (particularly the correlation between column density and velocity dispersion) but none match all observational probes at the same time (the large scales of the column density autocovariance is particularly challenging). We find that the simulated cloud (cloud C) showing growth via a turbulent radiative mixing layer (TRML) is the best match, implying the importance of TRML-mediated cooling for Milky Way HVCs. We conclude by suggesting improvements for simulations to better match observed HVCs.

astro-ph.GA↗

arXiv2024

Any Way the Wind Blows: Quantifying Superbubbles and their Outflows in Simulated Galaxies across $z \approx 0-3$

We present an investigation of clustered stellar feedback in the form of superbubbles identified within eleven galaxies from the FIRE-2 (Feedback in Realistic Environments) cosmological zoom-in simulation suite, at both cosmic noon (1 < z < 3) and in the local Universe. We study the spatially-resolved multiphase outflows that these supernovae drive, comparing our findings with recent theory and observations. These simulations consist of five LMC-mass galaxies and six Milky Way-mass progenitors (with a minimum baryonic particle mass of $m_{b.min} = 7100 M_{\odot}$), for which we calculate the local mass and energy loading factors on 750~pc scales from the identified outflows. We also characterize the multiphase morphology and properties of the identified superbubbles, including the `shell' of cool ($T<10^5$ K) gas and break out of energetic hot ($T>10^5$ K) gas when the shell bursts. For all galaxies, the outflow mass, momentum, and energy fluxes appear to reach their peak during the identified superbubbles, and we investigate the effects on the interstellar medium (ISM), circumgalactic medium (CGM), and subsequent star formation rates. We find that these simulations, regardless of redshift, have mass-loading factors and momentum fluxes in the cool gas that largely agree with recent observations. Lastly, we also investigate how methodological choices in measuring outflows can affect loading factors for galactic winds.

astro-ph.GA↗

arXiv2023

The Loneliest Galaxies in the Universe: A GAMA and GalaxyZoo Study on Void Galaxy Morphology

The large-scale structure (LSS) 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 of $9.35 < log(M/M_\odot) < 11.25$, and this sample is split by identifying two redshift-limited regions, 0 < z < 0.075, and, $0.075 < z < 0.15$. To find comparable objects in the sample of field galaxies from GAMA and Galaxy Zoo, we identify "twins" of void galaxies as field galaxies within $\pm$0.05 dex and $\pm$0.15 dex of M and specific star formation rate. We determine the statistical significance of our results using the Kolmogorov-Smirnov (KS) test. We see that void galaxies, in contrast with field galaxies, seem to be disk-dominated and have predominantly round bulges (with > 50 percent of the Galaxy Zoo citizen scientists agreeing that bulges are present).

astro-ph.GA↗

arXiv2022

Spatially Resolved Gas-phase Metallicity in FIRE-2 Dwarfs: Late-Time Evolution of Metallicity Relations in Simulations with Feedback and Mergers

We present an analysis of spatially resolved gas-phase metallicity relations in five dwarf galaxies ($M_{halo} \approx 10^{11} M_\odot$, $M_\star \approx 10^{8.8}-10^{9.6} M_\odot$) from the FIRE-2 (Feedback in Realistic Environments) cosmological zoom-in simulation suite, which include an explicit model for sub-grid turbulent mixing of metals in gas, near $z\approx 0$, over a period of 1.4 Gyrs, and compare our findings with observations. While these dwarf galaxies represent a diverse sample, we find that all simulated galaxies match the observed mass-metallicity (MZR) and mass-metallicity gradient (MZGR) relations. We note that in all five galaxies, the metallicities are effectively identical between phases of the interstellar medium (ISM), with 95$\%$ being within $\pm$0.1 dex between various ISM phases, including the cold and dense gas ($T < 500$ K and $n_{\rm H} > 1$ cm$^{-3}$), ionized gas (near the H$α$ $T \approx 10^4$ K ridge-line), and nebular regions (ionized gas where the 10 Myr-averaged star formation rate is non-zero). We find that most of the scatter in relative metallicity between cold and dense gas and ionized gas/nebular regions can be attributed to either local starburst events or metal-poor inflows. We also note the presence of a major merger in one of our galaxies, m11e, with a substantial impact on the metallicity distribution in the spatially resolved map, showing two strong metallicity peaks and triggering a starburst in the main galaxy.

astro-ph.GA↗