arXiv subjects

Amiel Sternberg

Publications and source records attributed to Amiel Sternberg.

At least 19 recordsLinked to original sources

arXiv2026

TNG SAM: Bridging Hydrodynamical Complexity and Semi-Analytic Efficiency to Model Galaxy Formation

All cosmological models of galaxy formation must navigate the trade-off between physical accuracy and computational efficiency. Hydrodynamical simulations provide spatially resolved predictions for the co-evolution of dark matter, gas, stars, and black holes, but rely on phenomenological subgrid models for small-scale processes (e.g., star formation). Semi-analytic models (SAMs), by contrast, gain efficiency through simplified, analytic treatments of the same processes, at the cost of reduced predictive scope. In this work, we leverage the strengths of the Santa Cruz SAM and the IllustrisTNG hydrodynamical simulation to develop the TNG SAM. Calibrated to reproduce baryon cycling in stellar feedback-dominated TNG galaxies ($\sim 10^{10}M_\odot < M_{200} < 10^{12}M_\odot$), the TNG SAM introduces several key updates to the Santa Cruz framework regarding: 1) halo gas (re-)accretion efficiency, 2) a cooling model that moves beyond the traditional cold/hot mode dichotomy, 3) explicit treatment of both galactic- and halo-scale outflows, 4) star formation efficiency, and 5) the circulation of metals between galaxies and their surroundings. These changes enable the TNG SAM to reproduce TNG's flow of gas and metals from the scale of the galaxy to the halo, as well as global galaxy (e.g., stellar mass) and halo (e.g. hot halo gas mass) properties within $\lesssim 30\%$ accuracy out to $z=6$. This work demonstrates that, with appropriate calibration, SAMs can capture the complex physics of galaxy formation modeled in hydrodynamical simulations while providing a flexible framework for studying galaxy evolution across the large cosmological volumes targeted by future observational surveys.

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arXiv2026

NOEMA$^\rm{3D}$: A deep view of cold gas flows in a barred spiral galaxy at $z\sim1$

We present a deep, high-resolution CO(4-3) IRAM-NOEMA observation of a main sequence, barred, spiral galaxy at $z\approx1.12$, with an on-source integration time of $\approx37$ hours and a beam FWHM of $\approx0.\!\!^{\prime\prime}3$. We use the molecular gas data in conjunction with the available deep multi-band JWST and HST imaging, covering restframe UV to near-IR wavelengths, to quantitatively study the gas flows in the disk plane of this cosmic noon barred spiral. We find that this target is a massive ($\log(M_{\rm{baryons}}/M_\odot)\approx10.96$), baryon-dominated ($f_{\rm{dm}}(<R_e)=u^2_{\rm{circ,dm}}(R_e)/u^2_{\rm{circ}}(R_e)\sim4\%$), gas-rich ($f_{\rm{gas}}=M_{\rm{gas}}/(M_{\rm{\star}}+M_{\rm{gas}})\approx40\%$) disk, hosting a long ($a_{\rm{bar}}\approx4.2$ kpc), strong ($Q_{\rm{b}}\approx0.37$), and fast ($\mathcal{R}=R_{\rm{CR}}/a_{\rm{bar}}\approx1.05$) bar, which rotates at an angular speed of $\Omega_{\rm{pattern}}\approx$ 50 km/s/kpc. This bar is driving molecular gas inflows with a net inflow rate of $\dot{M}\sim30$ $M_\odot$/yr, based on three estimates, which is of the same order as the galaxy-integrated star formation rate ($\rm{SFR}\approx36$ $M_\odot$/yr). We additionally identify evidence of a well-defined dust lane shock at the northwestern side of the bar, with gas motions parallel to this feature, in agreement with expectations for an established bar-driven flow. Our study highlights the possible role of bars as key drivers of galaxy evolution for a significant fraction of cosmic noon galaxies, offering a detailed picture of well-defined, bar-driven inflows in a high-$z$ barred spiral.

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arXiv2026

Molecular Outflows in the Nucleus of the Nearby Compton-thick AGN NGC 3079

We present Northern Extended Millimeter Array (NOEMA) observations of the CO (2-1) molecular gas kinematics in the nearby Compton-thick Seyfert 2 galaxy NGC 3079, with an angular resolution of 0.5" ($\sim$40 pc). To interpret the observed CO (2-1) kinematics, we model the rotating disk using two software tools, 3D-Barolo and DysmalPy, to generate mock 3D data cubes. Both models indicate, in addition to the rotating disk, the presence of a spatially unresolved nuclear component characterized by high velocity dispersion. Analysis of the visibility data reveals that the blue-shifted, high-velocity component is spatially offset from the continuum peak by 0.17" ($\sim$ 14 pc) and exhibits line-of-sight velocities of $v$ - $v_{sys}$ = -350 to -450 km s$^{-1}$, which we interpret as a nuclear molecular outflow. We calculate a molecular gas mass outflow rate of 8.82 $M_\odot$ yr$^{-1}$, with a kinetic power ($\dot{E}_{\text{out}}$) of 3.8 $\times$ 10$^{41}$ erg s$^{-1}$ and a momentum rate ($\dot{p}_{\text{out}}$) of 2.05 $\times$ 10$^{34}$ Dyne. The momentum rate exceeds the AGN radiation momentum rate by a factor of $\sim$15, suggesting an energy-driven outflow. Furthermore, we argue that the derived kinetic power of the nuclear molecular outflow favors a jet-powered scenario that explains the slowdown and brightening of the parsec-scale radio source observed with the Very Long Baseline Array.

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arXiv2026

NOEMA3D: Resolving radial gas flows in disk galaxies at z~1.1-1.6 with high-resolution CO observations

We present NOEMA3D, a unique high-resolution study of purely molecular gas kinematics at $z \sim 1.1$ to 1.6, providing a dedicated view of cold gas dynamics at the late stages of the peak epoch of cosmic star formation. Using deep ($> 20$ hr on source per target) IRAM-NOEMA CO observations of 10 massive ($10.45 < \log(M^*/M_\odot) < 11.43$)) main-sequence galaxies, complemented by high-resolution JWST imaging, we resolve the molecular gas kinematics and morphology on kiloparsec scales. We find that all galaxies exhibit ordered rotation with moderate intrinsic turbulence (median $σ_0 \sim 32 \pm 10$ km/s, median $V_c/σ_0 \sim 8.6 \pm 2.9$), consistent with dynamically turbulent disks at late cosmic noon. After modeling the axisymmetric rotation with the forward-modeling code DysmalPy, we reveal spatially coherent velocity residuals in all but one more inclined system. The inferred in-plane non circular motions reach amplitudes of $\sim 50$-100 km/s, significantly larger than typically observed in local disk galaxies. Interpreting these non-circular motions as radial flows we find that the velocity residuals spatially coincide with non-axisymmetric structures -- spiral arms and bars -- demonstrating a direct link between galaxy morphology and gas transport at $z \sim 1$-2. In spiral galaxies, the residual velocity patterns are typically dominated by inflows, while barred systems display an apparent inflow-outflow pattern, characteristic of in-plane bar-driven gas motions. We further find that the inferred molecular gas inflow rates are substantial, with a typical net inflow rate of the order of the star formation rate ($\dot M \sim -50 M_\odot$/yr). This implies that spiral arms and bars at cosmic noon are highly efficient at funneling cold gas toward galaxy centers, perhaps driving the buildup of bulges and feeding central star forming regions and supermassive black holes.

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arXiv2026

NOEMA3D: Extended CO, [C I] and dust in massive star-forming main-sequence galaxies at cosmic noon

We present a spatially resolved study of cold molecular gas and dust in ten main-sequence galaxies at z=1.1-1.6, using observations of CO(4-3), CO(3-2), [CI](1-0), and dust continuum from the NOEMA3D survey. We find widespread spatially extended molecular gas and dust, with sizes comparable to those of the stellar disk, in contrast to those of centrally dominated starburst galaxies at similar redshifts. Among the targeted molecular gas tracers, the CO line (J=3-2 or J=4-3) remains the most effective for mapping molecular gas distribution and kinematics. The spatially resolved correlations between different molecular gas tracers exhibit about twice the scatter as their galactic-integrated correlations, indicating that interstellar medium (ISM) conditions already deviate from global averages on scales of 3-6 kpc. This likely reflects the clumpy or inhomogeneous ISM in cosmic noon star-forming galaxies. Within our sample, both the molecular gas fraction and its depletion time are nearly constant across the galactic disks out to 2xRe, supporting a global linear Kennicutt-Schmidt law. These galaxies also have relatively small bulges, with bulge-to-total ratios between 6-24%, and are actively forming stars. These results provide a resolved view of how galaxies can remain on the star-forming main sequence during their secular evolution at late cosmic noon, an evolutionary stage supported by quasi-steady gas accretion and efficient gas transport via prominent spiral arms and/or bars.

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arXiv2026

The ALPINE-CRISTAL-JWST Survey: Gas-phase abundance gradients of main sequence star-forming galaxies and their kinematics at $4 < z < 6$

We present gas-phase radial metallicity profiles for 20 main-sequence galaxies at $4 0.05{\rm dexkpc^{-1}}$ at $1\sigma$, and none have a significant negative gradient. We investigated the correlation between the metallicity gradients and the intrinsic gas velocity dispersion $\sigma_0$ as well as the $V_{\rm rot}/\sigma_0$ ratio of the disks. Combining our sample with mass-matched literature samples at $3<z<7$, we found a negative shallow correlation between $V_{\rm rot}/\sigma_0$ and the metallicity gradients, but no strong relationships with $\sigma_0$. As $V_{\rm rot}/\sigma_0$ increases towards later cosmic times, the observed negative trend with $V_{\rm rot}/\sigma_0$ is consistent with the overall cosmic evolution of metallicity gradients from high to low redshifts. This suggests that disk maturity plays a crucial role in shaping the radial metallicity gradients. [Abridged abstract]

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arXiv2026

The Cosmic Baryon Cycle in IllustrisTNG: flows of mass, energy, and metals

We measure and analyze the inflows and outflows of mass, energy, and metals through the interstellar medium (ISM) and circumgalactic medium (CGM) of galaxies in the IllustrisTNG100 simulations. We identify the dominant feedback mechanism in bins of halo virial mass and redshift by computing the integrated energy input from SNe and the ``kinetic'' and ``thermal'' mode of AGN feedback. We measure all quantities in a shell at the virial radius (``halo scale'') and one chosen to be approximately at the interface of the CGM and the interstellar medium (ISM; ``ISM scale''). We find that galaxies have strong net positive inflows on halo scales, and weaker but still net positive inflows on ISM scales, at $z\gtrsim 2$. At later times, partially due to the onset of kinetic AGN feedback in massive halos, inflows and outflows nearly balance one another, leading to the familiar effects of the slow-down of galaxy growth and the onset of quenching. Halos dominated by SN feedback show only weak evidence of preventative feedback on halo scales, and we see excess ISM scale accretion indicative of rapid gas recycling. Wind mass loadings decrease with increasing halo mass, and with increasing redshift, while energy loadings are nearly independent of both mass and redshift. The detailed catalogs of these mass, metal, and energy inflow and outflow rates on galaxy and halo scales can be used to guide empirical and semi-analytic models, and provide deeper insight into how galaxy growth and quenching is regulated in the IllustrisTNG simulations.

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arXiv2025

The GHOSDT Simulations: II. Missing H$_2$ in Simulations of a Self-Regulated Interstellar Medium

Observations in the Galaxy and nearby spirals have established that the HI-to-H$_2$ transition at solar metallicity occurs at gas weight of $P_{\rm DE}/k_B\approx 10^4 \ \rm K \ cm ^{-3}$, similar to solar neighbourhood conditions. Even so, state-of-the-art models of a self-regulated interstellar medium underproduce the molecular fraction ($R_{\rm mol} \equiv M_{{\rm H}_2}/M_{HI}$) at solar neighbourhood conditions by a factor of $\approx2-4$. We use the GHOSDT suite of simulations at a mass resolution range of $100-0.25\ M_{\odot}$ (effective spatial resolution range of $\sim 20-0.05\ \rm pc$) run for 500 Myr to show how this problem is affected by modeling choices such as the inclusion of photoionizing radiation, assumed supernova energy, numerical resolution, inclusion of magnetic fields, and including a model for sub-grid clumping. We find that $R_{\rm mol}$ is not converged even at a resolution of 1 $M_{\odot}$, with $R_{\rm mol}$ increasing by a factor of 2 when resolution is improved from 10 to $1\ M_{\odot}$. Models excluding either photoionization or magnetic fields result in a factor 2 reduction in $R_{\rm mol}$. The only model that agrees with the observed value of $R_{\rm mol}$ includes our sub-grid clumping model, which enhances $R_{\rm mol}$ by a factor of $\sim3$ compared with our fiducial model. This increases the time-averaged $R_{\rm mol}$ to $0.25$, in agreement with the Solar circle value, and closer to the observed median value of $0.42$ in regions comparable to the solar neighbourhood in nearby spirals. Our findings show that small-scale clumping in the ISM plays a significant role in H$_2$ formation even in high-resolution numerical simulations.

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arXiv2025

Molecular Hydrogen in High-redshift Damped Lyman-α Absorbers

Simulations predict that circumgalactic hydrogen gas surrounding massive ($M_{\rm{halo}}^{z=1}=10^{12}-10^{13}\ M_{\odot}$) galaxies at $z\sim4$ may be predominantly neutral, and could produce damped Ly$α$ absorbers (DLAs) along sight-lines to background quasars \citep{Stern2021}. A circumgalactic medium (CGM) origin for DLAs naturally explains high redshift HI absorption-selected galaxy detections at physical separations much greater than the likely extents of the galaxy disks \citep{Neeleman2017, Neeleman2019}. The observed $z\sim 4$ DLA HI column densities are large and comparable to interstellar (ISM) gas columns at which substantial molecular hydrogen (H$_2$) abundances occur. We therefore investigate the possible molecular content of high-redshift CGM gas, and its potential detectability via (rest-frame) far-ultraviolet (UV) absorption line studies. For this purpose we develop an analytic sub-grid model for HI-to-H$_2$ transitions and incorporate the model with zoom-in FIRE-2 simulations of evolving high-$z$ galaxies. We include dust absorption and scattering computations for the transfer of photodissociating Lyman-Werner (LW) band radiation. We find that the typical extents of detectable H$_2$ sightlines are $\approx 0.1\, R_{\rm vir}$, independent of redshift from $z=2.5$ to 5. We argue that a CGM origin for DLAs naturally explains the low detection rates of H$_2$ in DLA observations, as the low CGM densities and relatively strong far-UV fields lead to molecular fractions much lower than observed in the ISM at comparable HI columns.

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arXiv2025

Resolving stellar populations, star formation, and interstellar medium conditions with JWST in a large spiral galaxy at $z\approx2$

Cosmic noon represents the prime epoch of galaxy assembly, and a sweet spot for observations with the James Webb Telescope (JWST) and ground-based near-IR integral-field unit (IFU) spectrographs. This work analyses JWST NIRSpec Micro Shutter Array (MSA), NIRCam Wide Field Slitless Spectroscopy (WFSS) of K20-ID7, a large spiral, star-forming (SF) galaxy at z=2.2, with evidence for radial gas inflows. By exploiting the synergy with ground-based IFU ERIS observations, we conduct a comprehensive and resolved study of the interstellar medium (ISM) and stellar properties, from rest optical to near-IR, via emission-line diagnostics, resolved spectral energy distribution (SED) fitting of high-resolution imaging, and Pa$\beta$ line detection in NIRCam WFSS data. Our analysis reveals massive ($M_{\star}\simeq$(0.67-3.5)$\times$10$^{9}$ $M_{\odot}$) SF clumps with star formation rates (SFRs) ~3-24 $M_{\odot}$/yr, and quite low dust attenuation ($A_V\simeq$0.4), electron density ($n_{e}$<300 cm$^{-3}$), and ionisation (log(U)$\simeq -3.0$). The central bulge turns out to be modestly massive ($M_{\star}$=(7$\pm$3)$\times$10$^{9}$ M$_{\odot}$), heavily obscured ($A_V$=6.43$\pm$0.55), and likely to have formed most of its stellar mass in the past (SFR=82$\pm$42 $M_{\odot}$/yr over the last 100 Myr), yet still forming stars at a lower rate (SFR=12$\pm$8 M$_{\odot}$/yr over the last 10 Myr). We infer a metallicity 12+log(O/H)~8.54 and an apparent enhancement of the N/O abundance (log(N/O)$\simeq -1.0$) in all distinct galaxy regions, a likely consequence of dilution effects due to radial inflows of metal-poor gas. We measure a sub-solar sulfur abundance (log(S/O)$\simeq$-1.9). Finally, the radial stellar age profile reveals older stellar populations in the inner galaxy regions compared to the outskirts, pointing to an inside-out growth of K20-ID7.

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arXiv2025

The ALMA-CRISTAL survey: Resolved kinematic studies of main sequence star-forming galaxies at 4<z<6

We present a detailed kinematic study of a sample of 32 massive ($9.5\leqslant\log(M_*/{\rm M_{\odot}})\leqslant10.9$) main-sequence star-forming galaxies (MS SFGs) at $4<z<6$ from the ALMA-CRISTAL program. The data consist of deep (up to 15hr observing time per target), high-resolution ($\sim1$kpc) ALMA observations of the [CII]158$μ$m line emission. This data set enables the first systematic kpc-scale characterisation of the kinematics nature of typical massive SFGs at these epochs. We find that $\sim50\%$ of the sample are disk-like, with a number of galaxies located in systems of multiple components. Kinematic modelling reveals these main sequence disks exhibit high-velocity dispersions ($σ_0$), with a median disk velocity dispersion of $\sim70{\rm kms^{-1}}$ and $V_{\rm rot}/σ_0\sim2$, and consistent with dominant gravity driving. The elevated disk dispersions are in line with the predicted evolution based on Toomre theory and the extrapolated trends from $z\sim0$-$2.5$ MS star-forming disks. The inferred dark matter (DM) mass fraction within the effective radius $f_{\rm DM}(<R_{\rm e})$ for the disk systems decreases with the central baryonic mass surface density, and is consistent with the trend reported by kinematic studies at $z\lesssim3$; roughly half the disks have $f_{\rm DM}(<R_{\rm e})\lesssim30\%$. The CRISTAL sample of massive MS SFGs provides a reference of the kinematics of a representative population and extends the view onto typical galaxies beyond previous kpc-scale studies at $z\lesssim3$.

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arXiv2025

PHIBSS: Searching for Molecular Gas Outflows in Star-Forming Galaxies at $z =$ 0.5-2.6

We present an analysis of millimeter CO observations to search and quantify signatures of molecular gas outflows. We exploit the large sample of $0.5 < z < 2.6$ galaxies observed as part of the PHIBSS1/2 surveys with the IRAM Plateau de Bure interferometer, focusing on the 154 typical massive star-forming galaxies with CO detections (mainly CO(3-2), but including also CO(2-1) and CO(6-5)) at signal-to-noise (SNR) > 1.5 and available properties (stellar mass, star formation rate, size) from ancillary data. None of the individual spectra exhibit a compelling signature of CO outflow emission even at high SNR > 7. To search for fainter outflow signatures, we carry out an analysis of stacked spectra, including the full sample, as well as subsets, split in terms of stellar mass, redshift, inclination, offset in star formation rate (SFR) from the main sequence, and AGN activity. None of the physically motivated subsamples show any outflow signature. We report a tentative detection in a subset statistically designed to maximize outflow signatures. We derive upper limits on molecular gas outflow rate and mass loading factors $η$ based on our results and find $η\leq$ 2.2-35.4, depending on the subsample. Much deeper CO data and observations of alternative tracers are needed to decisively constrain the importance of cold molecular gas component of outflows relative to other gas phases.

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arXiv2025

NOEMA$^{\rm 3D}$: A first kpc resolution study of a $z\sim1.5$ main sequence barred galaxy channeling gas into a growing bulge

We present a very deep CO(3-2) observation of a massive, gas-rich, main sequence, barred spiral galaxy at $z\approx1.52$. Our data were taken with the IRAM-NOEMA interferometer for a 12-antenna equivalent on-source integration time of $\sim$ 50 hours. We fit the major axis kinematics using forward modelling of a rotating disk, and then subtract the two-dimensional beam convolved best-fit model revealing signatures of planar non-circular motions in the residuals. The inferred in-plane radial velocities are remarkably large, of the order of $\approx60$ km/s. Direct comparisons with a high-resolution, simulated, gas-rich, barred galaxy, obtained with the moving mesh code AREPO and the TNG sub-grid model, show that the observed non-circular gas flows can be explained as radial flows driven by the central bar, with an inferred net inflow rate of the order of the SFR. Given the recent evidence for a higher-than-expected fraction of barred disk galaxies at cosmic noon, our results suggest that rapid gas inflows due to bars could be important evolutionary drivers for the dominant population of star-forming galaxies at the peak epoch of star and galaxy formation.

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arXiv2025

The Molecular Cloud Lifecycle I: Constraining H2 formation and dissociation rates with observations

Molecular clouds (MCs) are the birthplaces of new stars in galaxies. A key component of MCs are photodissociation regions (PDRs), where far-ultraviolet radiation plays a crucial role in determining the gas's physical and chemical state. Traditional PDR models assume chemical steady state (CSS), where the rates of H$_2$ formation and photodissociation are balanced. However, real MCs are dynamic and can be out of CSS. In this study, we demonstrate that combining H$_2$ emission lines observed in the far-ultraviolet or infrared with column density observations can be used to derive the rates of H$_2$ formation and photodissociation. We derive analytical formulae that relate these rates to observable quantities, which we validate using synthetic H$_2$ line emission maps derived from the SILCC-Zoom hydrodynamical simulation. Our method estimates integrated H$_2$ formation and dissociation rates with an accuracy $\approx 30$ % (on top of uncertainties in observed H$_2$ emission maps and column densities). Our simulations, valid for column densities $N \leq 2 \times 10^{22}$ cm$^{-2}$, cover a wide dynamic range in H$_2$ formation and photodissociation rates, showing significant deviations from CSS, with 74 % of the MC's mass deviating from CSS by a factor greater than 2. Our analytical formulae can effectively distinguish between regions in and out of CSS. When applied to actual H$_2$ line observations, our method can assess the chemical state of MCs, providing insights into their evolutionary stages and lifetimes. A NASA Small Explorer mission concept, Eos, will be proposed in 2025 and is specifically designed to conduct the types of observations outlined in this study.

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arXiv2024

Disk kinematics at high redshift: DysmalPy's extension to 3D modeling and comparison with different approaches

Spatially-resolved emission line kinematics are invaluable to investigating fundamental galaxy properties and have become increasingly accessible for galaxies at $z\gtrsim0.5$ through sensitive near-infrared imaging spectroscopy and millimeter interferometry. Kinematic modeling is at the core of the analysis and interpretation of such data sets, which at high-z present challenges due to lower signal-to-noise ratio (S/N) and resolution compared to data of local galaxies. We present and test the 3D fitting functionality of DysmalPy, examining how well it recovers intrinsic disk rotation velocity and velocity dispersion, using a large suite of axisymmetric models, covering a range of galaxy properties and observational parameters typical of $z\sim1$-$3$ star-forming galaxies. We also compare DysmalPy's recovery performance to that of two other commonly used codes, GalPak3D and 3DBarolo, which we use in turn to create additional sets of models to benchmark DysmalPy. Over the ranges of S/N, resolution, mass, and velocity dispersion explored, the rotation velocity is accurately recovered by all tools. The velocity dispersion is recovered well at high S/N, but the impact of methodology differences is more apparent. In particular, template differences for parametric tools and S/N sensitivity for the non-parametric tool can lead to differences up to a factor of 2. Our tests highlight and the importance of deep, high-resolution data and the need for careful consideration of: (1) the choice of priors (parametric approaches), (2) the masking (all approaches) and, more generally, evaluating the suitability of each approach to the specific data at hand. This paper accompanies the public release of DysmalPy.

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arXiv2024

Bursts of star formation and radiation-driven outflows produce efficient LyC leakage from dense compact star clusters

The escape of LyC photons emitted by massive stars from the dense interstellar medium of galaxies is one of the most significant bottlenecks for cosmological reionization. The escape fraction shows significant scatter between galaxies, and anisotropic, spatial variation within them, motivating further study of the underlying physical factors responsible for these trends. We perform numerical radiation hydrodynamic simulations of idealized clouds with different gas surface densities (compactness) $Σ\sim 10^2$--$10^5 \, M_{\odot} \rm{pc}^{-2}$, meant to emulate star cluster-forming clumps ranging from conditions typical of the local Universe to the high ISM-pressure conditions more frequently encountered at high redshift. Our results indicate that dense compact star clusters with $Σ\gtrsim 10^4 \, M_{\odot} \rm{pc}^{-2}$ efficiently leak LyC photons, with cloud-scale luminosity-weighted average escape fractions $\gtrsim 80\%$ as opposed to $\lesssim 10\%$ for $Σ\sim 100 \, M_{\odot} \rm{pc}^{-2}$. This occurs due to higher star formation efficiencies and shorter dynamical timescales at higher $Σ$; the former results in higher intrinsic LyC emission, and the latter implies rapid evolution, with a burst of star formation followed by rapid gas dispersal, permitting high LyC escape well before the intrinsic LyC emission of stellar populations drop ($\sim 4 \, \mathrm{Myr}$). LyC escape in dense clouds is primarily facilitated by highly ionized outflows driven by radiation pressure on dust with velocities $ \sim 3$ times the cloud escape velocity. We also vary the (assumed) dust abundances ($Z_{\rm{d}}$) and find a very mild increase ($\sim 10%$) in the escape fraction for $\sim 100$ lower $Z_{\mathrm{d}}$. Our results suggest a scenario in which localized compact bursts of star formation in galaxies are disproportionately productive sites of LyC leakage.

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arXiv2024

Sunyaev-Zeldovich Signals from $L^*$ Galaxies: Observations, Analytics, and Simulations

We analyze measurements of the thermal Sunyaev-Zeldovich (tSZ) effect arising in the circumgalactic medium (CGM) of $L^*$ galaxies, reported by Bregman et al. 2022 and Das et al. 2023. In our analysis we use the Faerman et al. 2017 and Faerman et al. 2020 CGM models, a new power-law model (PLM), and the TNG100 simulation. For a given $M_{\rm vir}$, our PLM has four parameters; the fraction, $f_{\rm hCGM}$, of the halo baryon mass in hot CGM gas, the ratio, $ϕ_T$, of the actual gas temperature at the virial radius to the virial temperature, and the power-law indicies, $a_{P,{\rm th}}$ and $a_n$ for the thermal electron pressure and the hydrogen nucleon density. The B+22 Compton-$y$ profile implies steep electron pressure slopes ($a_{P,{\rm th}}\simeq 2$). For isothermal conditions the temperature is at least $1.1\times 10^6$ K, with a hot CGM gas mass of up to $3.5\times 10^{11}$ M$_\odot$ for a virial mass of $2.75\times 10^{12}$ M$_\odot$. However, if isothermal the gas must be expanding out of the halos. An isentropic equation of state is favored for which hydrostatic equilibrium is possible. The B+22 and D+23 results are consistent with each other and with recent (0.5-2 keV) CGM X-ray observations by Zhang et al. 2024 of Milky Way mass systems. For $M_{\rm vir}\simeq 3\times 10^{12}$ M$_\odot$, the scaled Compton pressure integrals, $E(z)^{-2/3}Y_{500}/M_{\rm vir,12}^{5/3}$, lie in the narrow range, $2.5\times 10^{-4}$ to $5.0\times 10^{-4}$ kpc$^2$, for all three sets of observations. TNG100 underpredicts the tSZ parameters by factors $\sim 0.5$ dex for the $L^*$ galaxies, suggesting that the feedback strengths and CGM gas losses are overestimated in the simulated halos at these mass scales.

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arXiv2024

X-ray signatures of galactic outflows into the circumgalactic medium

We present a set of controlled hydrodynamical simulations to study the effects of strong galactic outflows on the density and temperature structures, and associated X-ray signatures, of extra-planar and circumgalactic gas. We consider three initial state models, isothermal, isentropic, and rotating cooling-flow, for the hot circumgalactic medium (CGM) into which the outflows are driven. The energy sources are either stellar winds and supernovae, or active galactic nuclei. We consider energy injection rates in the range $10^{40} < \dot{E}_{\rm inj} <10^{44.5}$ erg s$^{-1}$, and compute the time-dependent soft X-ray (0.5-2 keV) surface brightness. For $\dot{E}_{\rm inj} \gtrsim 10^{41} - 10^{42}$ erg s$^{-1}$, with the exact threshold depending on the initial CGM state, the X-ray response is dominated by dense hot gas in the forward shock that eventually fades into the CGM as a sound wave. The shock surrounds an inner hot bubble leading to a radial flattening of the X-ray surface brightness. For lower energy injection rates, the X-ray surface brightness of the initial CGM state is almost unaffected. We present analytic approximations for the outflow shock propagation and the associated X-ray emissions.

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