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We study vorticity production in isothermal, subsonic, acoustic (nonvortical), decaying turbulence due to the presence of magnetic fields. Using three-dimensional numerical simulations, we always find that the resulting turbulent kinetic energy cascade follows the ordinary Kolmogorov phenomenology involving a constant spectral energy flux. For acoustic turbulence, the corresponding nondimensional prefactor is larger than the standard Kolmogorov constant due to an inefficiency in dissipating kinetic energy. We find that the Lorentz force can not only drive the direct production of vortical motions, but it can also facilitate the conversion of acoustic energy into vortical energy. This conversion is shown to be quadratic in the magnetic field strength and linear in the acoustic flow speed. By contrast, the direct production of vortical motions by the magnetic field is linear in the field strength. Our results suggest that magnetic fields play a crucial role in vorticity production in cosmological flows, particularly in scenarios where significant acoustic turbulence is prevalent. We also discuss the implications of our findings for the early universe, where magnetic fields may convert acoustic turbulence generated during cosmological phase transitions into vortical turbulence., Comment: 11 pages, 12 figures, 1 table, comments welcome

Observations of the circumgalactic medium (CGM) often display coincident absorption from species with widely varying ionization states, providing direct evidence for complex, multiphase interactions. Motivated by these measurements, we perform a series of cloud-crushing simulations that model cold clouds traveling through the hot CGM. We analyze the ion distributions of these clouds, generate mock absorption spectra, and study their implications on quasar (QSO) absorption observations. Our results show interesting multiphase features, in which ions with significantly different ionization potentials exist in the same absorber and share similar spectral features. However, our simulations are unable to explain high ions like O \textsc{vi} and their coexistence with lower ions that appear in many observed QSO absorption systems.

The kinetic Sunyaev-Zel'dovich effect (kSZ) and patchy screening effect are two complementary cosmic microwave background (CMB) probes of the reionization era. The kSZ effect is a relatively strong signal, but is difficult to disentangle from other sources of temperature anisotropy, whereas patchy screening is weaker but can be reconstructed using the cleaner polarization channel. Here, we explore the potential of using upcoming CMB surveys to correlate a reconstructed map of patchy screening with (the square of) the kSZ map, and what a detection of this cross-correlation would mean for reionization science. To do this, we use simulations and theory to quantify the contributions to this signal from different redshifts. We then use the expected survey properties for CMB-S4 and CMB-HD to make detection forecasts. We find that, for or our fiducial reionization scenario, CMB-S4 will obtain a hint of this signal at up to 1.8$\sigma$, and CMB-HD will detect it at up to 14$\sigma$. We explore the physical interpretation of the signal and find that it is uniquely sensitive to the first half of reionization and to the bispectrum of the ionized gas distribution., Comment: 18 pages, 9 figures. Submitted to ApJ

Supersonic turbulence occurs in many environments, particularly in astrophysics. In the crucial case of isothermal turbulence, the probability density function (PDF) of the logarithmic density, $s$, is well measured, but a theoretical understanding of the processes leading to this distribution remains elusive. We investigate these processes using Lagrangian tracer particles to track $s$ and $\frac{ds}{dt}$ in direct numerical simulations, and we show that their evolution can be modeled as a stochastic differential process with time-correlated noise. The temporal correlation functions of $s$ and $\frac{ds}{dt}$ decay exponentially, as predicted by the model, and the decay timescale is $\approx$ 1/6 the eddy turnover time. The behavior of the conditional averages of $\frac{ds}{dt}$ and $\frac{d^2s}{dt^2}$ is also well explained by the model, which shows that the density PDF arises from a balance between stochastic compressions/expansions, which tend to broaden the PDF, and the acceleration/deceleration of shocks by density gradients, which tends to narrow it., Comment: 40 pages, 10 figures, to appear in Science Advances

The thermal history and structure of the intergalactic medium (IGM) at $z \geq 4$ is an important boundary condition for reionization, and a key input for studies using the Ly$\alpha$ forest to constrain the masses of alternative dark matter candidates. Most such inferences rely on simulations that lack the spatial resolution to fully resolve the hydrodynamic response of IGM filaments and minihalos to HI reionization heating. In this letter, we use high-resolution hydrodynamic+radiative transfer simulations to study how these affect the IGM thermal structure. We find that the adiabatic heating and cooling driven by the expansion of initially cold gas filaments and minihalos sources significant small-scale temperature fluctuations. These likely persist in much of the IGM until $z \leq 4$. Capturing this effect requires resolving the clumping scale of cold, pre-ionized gas, demanding spatial resolutions of $\leq 2$ $h^{-1}$kpc. Pre-heating of the IGM by X-Rays can slightly reduce the effect. Our preliminary estimate of the effect on the Ly$\alpha$ forest finds that, at $\log(k /[{\rm km^{-1} s}]) = -1.0$, the Ly$\alpha$ forest flux power (at fixed mean flux) can increase $\approx 10\%$ going from $8$ and $2$ $h^{-1}$kpc resolution at $z = 4-5$ for gas ionized at $z < 7$. These findings motivate more careful analyses of how the effects studied here affect the Ly$\alpha$ forest., Comment: 6+1 pages, 2+1 figures, accepted for publication in MNRAS letters. Comments welcome

We investigate the growth of stellar discs in Milky Way-mass galaxies using the magnetohydrodynamical simulations of the Auriga Project in a full cosmological context. We focus on the gas accretion process along the discs, calculating the net, infall and outflow rates as a function of galactocentric distance, and investigate the relation between them and the star formation activity. The stellar distributions of around 70% of the simulated galaxies exhibit an ``inside-out'' pattern, with older (younger) stellar populations preferentially located in the inner (outer) disc regions. In all cases, we find a very tight correlation between the infall, outflow and net accretion rates, as well as between these three quantities and the star formation rate. This is because the amount of gas which is ultimately available for star formation in each radial ring depends not only on the infall rates, but also on the amount of gas leaving the disc in outflows, which directly relates to the local star formation level. Therefore, any of these rates can be used to identify galaxies with inside-out growth. For these galaxies, the correlation between the dominant times of accretion/star formation and disc radius is well fitted by a linear function. We also find that, when averaged over galaxies with formation histories similar to the Milky Way, the simulated accretion rates show a similar evolution (both temporally- and radially-integrated) to the usual accretion prescriptions used in chemical evolution models, although some major differences arise at early times and in the inner disc regions., Comment: 19 pages, 13 figures

A significant fraction of local galaxies exhibit stellar bars, non-axisymmetric structures composed of stars, gas, and dust. Identifying key differences between the properties of barred and unbarred galaxies can uncover clues about the conditions for triggering bar formation. We explore the early stages of bar formation in a small sample of disc barred galaxies extracted from the TNG50 cosmological simulation, and compare their properties to those of unbarred galaxies. According to our results, the most important difference between barred and unbarred galaxies is that the former have systematically higher fractions of stellar to dark matter mass in their inner regions, from very early stages and prior to the formation of the bars. They harbour high initial gas content, fostering increased star formation rates and leading to a central mass concentration that grows faster over time compared to unbarred galaxies. Examining the evolution of the halo spin within 10 ckpc reveals that barred galaxies have higher angular momentum transfer from the disc to the halo. Curiously, both barred and unbarred galaxies share similar initial low values of the halo spin, consistent with those proposed in the literature for bar formation. Furthermore, we evaluate existing stability criteria to capture the complexity of the process, and investigate the effects of mergers, flybys, and environment as possible drivers of bar formation. We find no clear link between mergers and disc instabilities resulting in the formation of bars, even though some of the simulated barred galaxies might have been influenced by these events., Comment: 20 pages, 20 figures, 2 tables

Galactic winds probe how stellar feedback regulates the mass and metallicity of galaxies. Observations show that galactic winds are multiphase and magnetised. In the local Universe, the dense phase is traced by emission and absorption lines, which reveal the presence of fast-moving clouds embedded in hot streams. Simulations tell us that magnetic fields can shield such clouds and delay their disruption, but there is little discussed on their observational effects. Using 3D MHD simulations, we study the influence of two orientations of the magnetic field (aligned and transverse) on the cloud morphology, temperature and density structure, mixing fraction, ion kinematics, column densities, and absorption spectra. We study supersonic wind-cloud systems with radiative processes, and develop a framework to extract ion column density maps and synthetic absorption spectra. The framework relies on studying ion populations and creating down-the-barrel spectra via an interface that links our PLUTO simulations to TRIDENT using YT, CLOUDY, and STARBURST99. We find that the transverse magnetic field makes the cloud asymmetric, shields and protects dense cold gas, and reduces mixing fractions compared to the aligned case. Ions can reach higher velocities in the transverse field case. The imprints of the initial orientation of the field on the synthetic spectra are: in the cold phase we find no signature of C ii and Si ii when the field is aligned, in the intermediate phase traced by C iv and Si iv we find broader lines in the transverse case, and in the warm phase we find deeper lines for O vi and N v in the aligned case, but they are less sensitive to the field orientation. Magnetic fields significantly affect the absorption spectra of cold clouds. Intermediate ions are the most sensitive to the magnetic field orientation and can potentially yield information about magnetic field topology., Comment: 18 pages, 13 figures

Current models of galaxy formation require strong feedback from active galactic nuclei (AGN) to explain the observed lack of star formation in massive galaxies since z~2 but direct evidence of this energy input is limited. We use the SIMBA cosmological galaxy formation simulations to assess the ability of thermal Sunyaev-Zel'dovich (tSZ) measurements to provide such evidence, by mapping the pressure structure of the circumgalactic medium around massive z~0.2-1.5 galaxies. We undertake a stacking approach to calculate the total tSZ signal and its radial profile in simulations with varying assumptions of AGN feedback, and we assess its observability with current and future telescopes. By convolving our predictions with the 2.1' beam of the Atacama Cosmology Telescope (ACT), we show that current observations at z~1 are consistent with SIMBA's fiducial treatment of AGN feedback, and inconsistent with SIMBA models without feedback. At z~0.5, observational signals lie between SIMBA run with and without AGN feedback, suggesting AGN in SIMBA may inject too much energy at late times. By convolving our data with a 9.5'' beam corresponding to the TolTEC camera on the Large Millimeter Telescope Alfonso Serrano (LMT), we predict a unique profile for AGN feedback that can be distinguished with future higher-resolution measurements. Finally, we explore a novel approach to quantify the non-spherically symmetric features surrounding our galaxies by plotting radial profiles representing the component of the stack with m-fold symmetry., Comment: 16 pages, 13 figures, 3 tables. Accepted by ApJ

Our knowledge of the circumgalactic medium (CGM) is mostly based on quasar absorption-line measurements. These have uncovered a multiphase medium that is likely highly turbulent, but constraints of this turbulence are limited to measurements of the non-thermal width of absorption-line components ($b_{turb}$) and the line-of-sight velocity dispersion between components ($\sigma_{LOS}$). Here we analyze a suite of CGM simulations to determine how well these indirect measures are related to the underlying CGM. Our simulations track the non-equilibrium evolution of all commonly observed ions, and consist of two main types: small-scale simulations of regions of homogeneous CGM turbulence and global simulations of inhomogeneous turbulence throughout a galactic halo. From each simulation, we generate mock spectra of Si II, Si IV, C IV, and O VI, which allow us to directly compare $b_{turb}$ and $\sigma_{LOS}$ to the true line-of-sight turbulence ($\sigma_{1D}$). In the small-scale simulations, $b_{turb}$ is only weakly correlated with $\sigma_{1D}$, likely because it measures random motions within individual warm CGM clouds, which do not sample the overall random motions. Meanwhile, $\sigma_{LOS}$ and $\sigma_{1D}$ are strongly correlated, with $\sigma_{1D}\approx\sigma_{LOS}+10$ km s$^{-1}$ in the densest regions we simulated, though, the strength of this correlation depended weakly on the gas phase being probed. Our large-scale simulations also indicate that $b_{turb}$ and $\sigma_{1D}$ are largely uncorrelated, and that $\sigma_{1D}\approx\sigma_{LOS}+10$ kms$^{-1}$ on average, although it varies along individual sightlines. Moreover, the $\sigma_\mathrm{LOS}$ distributions from our global simulations are similar to recent observations, suggesting that this quantity may provide useful constraints on circumgalactic turbulence regardless of the axis probed., Comment: 16 pages, 9 figures, 2 tables, ApJ, in press

Star formation, together with the associated chemical and energy feedback, is one of the most important processes in galaxy evolution. The star formation activity in galaxies defines and affects many of their fundamental properties, such as stellar mass, morphology and chemical enrichment levels. Simple models for star formation in cosmological hydrodynamical simulations have shown to be successful in reproducing the star formation rate (SFR) levels and shapes of different types of galaxies. However, with the advent of high-resolution simulations and more detailed observations, more sophisticated star formation models are needed; in particular, to better understand the relation between star formation and the amount of gas in the atomic and molecular phases. In this work, we apply a novel star formation model, recently developed to work in the context of hydrodynamical simulations, to the study of the SFR in Milky Way-mass galaxies. The new implementation describes the formation of molecular hydrogen from atomic material, considering also possible dependencies with the chemical abundance of the gas. This allows to implement various star formation models, where the SFR of a gas cloud is determined by the atomic and/or molecular gas phases, and to compare their predictions to recent observational results., Comment: 3 pages, 3 figures. To appear in the 64nd Bulletin of the Argentine Astronomical Society

The Local Group (LG) consists of two giant spiral galaxies, the Milky Way (MW) and Andromeda (M31), and several smaller galaxies. The MW and M31 are approaching each other at a radial velocity of about $-109\,$km\,s$^{-1}$. Observational evidence suggests that there is an overall infalling motion of gas and galaxies in the LG, dominated by the dynamics of its two main members. From our perspective, this flow imprints a velocity dipole pattern in the sky when Galactic rotation is removed. We investigate the kinematic properties of gas and galaxies in the LG using a suite of high-resolution simulations performed by the {\sc Hestia} (High-resolution Environmental Simulations of The Immediate Area) collaboration. Our simulations include the correct cosmography surrounding LG-like regions. We build sky maps from the local, Galactic and LG standard of rest reference frames. Our findings show that the establishment of a radial velocity dipole near the preferred barycentre direction is a natural outcome of simulation kinematics for material \textit{outside} the MW virial radius after removing galaxy rotation when the relative radial velocity of MW and M31 is similar to the observed value. These results favour a scenario where gas and galaxies stream towards the LG barycentre, producing the observed velocity dipole., Comment: 3 pages, 3 figures. To appear in the 64th Bulletin of the Argentine Astronomical Society. arXiv admin note: substantial text overlap with arXiv:2210.15589

In the standard model of structure formation, galaxies form in the centre of dark matter haloes that develop as a result of inhomogeneities in the primordial mass distribution of the Universe. Afterwards, galaxies grow by means of continuous accretion of gaseous material stemming from the intergalactic medium, both in diffuse form and through collisions with other systems. After an initial period of violent growth, the gas settles into a rotationally-supported structure where stars are born, giving birth to the stellar disc. The accretion of gaseous material onto the disc plays a fundamental role in its evolution as it can change its dynamical and morphological properties, generating gas flows within the disc. In this work, we use 30 galaxies from the Auriga Project, a set of cosmological magnetohydrodynamical simulations of disc galaxies, to study the temporal dependence of the gas accretion rates, focusing on the inflowing and outflowing fluxes., Comment: 3 pages, 2 figures. To appear in the 64th Bulletin of the Argentine Astronomical Society

We use public data from the South Pole Telescope (SPT) and Atacama Cosmology Telescope (ACT) to measure radial profiles of the thermal Sunyaev-Zel'dovich (tSZ) effect and dust emission around massive quiescent galaxies at $z\approx1.$ Using survey data from the Dark Energy Survey (DES) and Wide-Field infrared Survey Explorer (WISE), we selected $387,627$ quiescent galaxies within the ACT field, with a mean stellar $\log_{10}(M_{\star}/\rm{M_{\odot}})$ of $11.40$. A subset of $94,452$ galaxies, with a mean stellar $\log_{10}(M_{\star}/\rm{M_{\odot}})$ of $11.36,$ are also covered by SPT. In $0.5$ arcminute radial bins around these galaxies, we detect the tSZ profile at levels up to $11\sigma$, and dust profile up to $20\sigma.$ Both profiles are extended, and the dust profile slope at large radii is consistent with galaxy clustering. We analyze the thermal energy and dust mass versus stellar mass via integration within $R=2.0$ arcminute circular apertures and fit them with a forward-modeled power-law to correct for our photometric stellar mass uncertainty. At the mean log stellar mass of our overlap and wide-area samples, respectively, we extract thermal energies from the tSZ of $E_{\rm{pk}}=6.45_{-1.52}^{+1.67}\times10^{60}{\rm{ erg}}$ and $8.20_{-0.52}^{+0.52}\times10^{60}{\rm{ erg}},$ most consistent with moderate to high levels of active galactic nuclei feedback acting upon the circumgalactic medium. Dust masses at the mean log stellar mass are $M_{\rm{d,pk}}=6.23_{-0.67}^{+0.67}\times10^{8}\rm{ M_{\odot}}$ and $6.76_{-0.56}^{+0.56}\times10^{8}\rm{ M_{\odot}},$ and we find a greater than linear dust-to-stellar mass relation, which indicates that the more massive galaxies in our study retain more dust. Our work highlights current capabilities of stacking millimeter data around individual galaxies and potential for future use., Comment: 23 pages, 12 figures, accepted for publication in ApJ

Motivated by observations of multiphase galaxy outflows, we explore the impact of isotropic and anisotropic electron thermal conduction on the evolution of radiatively-cooled, cold clouds embedded in hot, magnetized winds. Using the adaptive mesh refinement code AthenaPK, we conduct simulations of clouds impacted by supersonic and transonic flows with magnetic fields initially aligned parallel and perpendicular to the flow direction. In cases with isotropic thermal conduction, an evaporative wind forms, stabilizing against instabilities and leading to a mass loss rate that matches the hydrodynamic case. In anisotropic cases, the impact of conduction is more limited and strongly dependent on the field orientation. In runs with initially perpendicular fields, the field lines are folded back into the tail, strongly limiting conduction, but magnetic fields act to dampen instabilities and slow the stretching of the cloud in the flow direction. In the parallel case, anisotropic conduction aids cloud survival by forming a radiative wind near the front of the cloud, which suppresses instabilities and reduces mass loss. In all cases, anisotropic conduction has a minimal impact on the acceleration of the cloud., Comment: accepted by ApJ

We investigate the kinematic properties of gas and galaxies in the Local Group (LG) using high-resolution simulations performed by the {\sc Hestia} (High-resolution Environmental Simulations of The Immediate Area) collaboration. Our simulations include the correct cosmography surrounding LG-like regions consisting of two main spiral galaxies of $\sim 10^{12}$~M$_\odot$, their satellites and minor isolated galaxies, all sharing the same large-scale motion within a volume of a few Mpc. We characterise the gas and galaxy kinematics within the simulated LGs, from the perspective of the Sun, to compare with observed trends from recent HST/COS absorption-line observations and LG galaxy data. To analyse the velocity pattern of LG gas and galaxies seen in the observational data, we build sky maps from the local standard of rest, and the galactic and local group barycentre frames. Our findings show that the establishment of a radial velocity dipole at low/high latitudes, near the preferred barycentre direction, is a natural outcome of simulation kinematics for material {\it outside} the Milky Way virial radius after removing galaxy rotation when the two main LG galaxies are approaching. Our results favour a scenario where gas and galaxies stream towards the LG barycentre producing a velocity dipole resembling observations. While our study shows in a qualitative way the global matter kinematics in the LG as part of its on-going assembly, quantitative estimates of gas-flow rates and physical conditions of the LG gas have to await a more detailed modeling of the ionization conditions, which will be presented in a follow-up paper., Comment: 13 pages, 9 figures, accepted for publication in MNRAS

We use the 30 simulations of the Auriga Project to estimate the temporal dependency of the inflow, outflow and net accretion rates onto the discs of Milky Way-like galaxies. The net accretion rates are found to be similar for all galaxies at early times, increasing rapidly up to $\sim 10~\mathrm{M}_\odot \, \mathrm{yr}^{-1}$. After $\sim 6~\mathrm{Gyr}$ of evolution, however, the net accretion rates are diverse: in most galaxies, these exhibit an exponential-like decay, but some systems instead present increasing or approximately constant levels up to the present time. An exponential fit to the net accretion rates averaged over the MW analogues yields typical decay time-scale of $7.2~\mathrm{Gyr}$. The analysis of the time-evolution of the inflow and outflow rates, and their relation to the star formation rate (SFR) in the discs, confirms the close connection between these quantities. First, the inflow$/$outflow ratio stays approximately constant, with typical values of $\dot{M}_\mathrm{out}/ \dot{M}_\mathrm{in} \sim 0.75$, indicating that the gas mass involved in outflows is of the order of 25% lower compared to that involved in inflows. A similar behaviour is found for the SFR$/$inflow rate ratio, with typical values between 0.1 and 0.3, and for the outflow rate$/$SFR which varies in the range $3.5$--$5.5$. Our results show that continuous inflow is key to the SFR levels in disc galaxies, and that the star formation activity and the subsequent feedback in the discs is able to produce mass-loaded galaxy winds in the disc-halo interface., Comment: 21 pages, 15 figures

The recently launched James Webb Space Telescope promises unparalleled advances in our understanding of the first stars and galaxies, but realizing this potential requires cosmological simulations that capture the key physical processes that affected these objects. Here we show that radiative transfer and subgrid turbulent mixing are two such processes. By comparing simulations with and without radiative transfer but with exactly the same physical parameters and subgrid turbulent mixing model, we show that tracking radiative transfer suppresses the Population III (Pop III) star formation density by a factor of approximately 4. In both simulations, $\gtrsim 90\%$ of Pop III stars are found in the unresolved pristine regions tracked by our subgrid model, which does a better job at modeling the regions surrounding proto-galaxy cores where metals from supernovae take tens of Myrs to mix thoroughly. At the same time, radiative transfer suppresses Pop III star formation, via the development of ionized bubbles that slows gas accretion in these regions, and it results in compact high-redshift galaxies that are surrounded by isolated low mass satellites. Thus turbulent mixing and radiative transfer are both essential processes that must be included to accurately model the morphology, composition, and growth of primordial galaxies., Comment: Accepted by ApJ, Jul 2022, Comments welcome

Absorption-line measurements of the circumgalactic medium (CGM) display a highly non-uniform distribution of lower ionization state species accompanied by more widespread higher ionization state material. This suggests that the CGM is a dynamic, multiphase medium, such as arises in the presence of turbulence. To better understand this evolution, we perform hydrodynamic and magneto-hydrodynamic (MHD) simulations of the CGM surrounding Milky Way-like galaxies. In both cases, the CGM is initially in hydrostatic balance in a $10^{12}$ solar masses dark matter gravitational potential, and the simulations include rotation in the inner halo and turbulence that decreases radially. They also track ionizations, recombinations, and species-by-species radiative cooling in the presence of the redshift-zero UV background, employing the MAIHEM non-equilibrium chemistry package. We find that after 9 Gyrs of evolution, the presence of a magnetic field leads to an overall hotter CGM, with cool gas in the center where magnetic pressure dominates. While the non-MHD run produces more cold clouds overall, we find similar Si IV/O VI and N V/O VI ratios between the MHD and non-MHD runs, which are both very different from their equilibrium values. The non-MHD halo develops cool, low angular momentum filaments above the central disk, in comparison to the MHD run that has more efficient angular momentum transport, especially for the cold gas which forms a more ordered and extended disk late into its evolution., Comment: 24 pages, 16 figures

We investigate the origin of the abundance ratios and scatter of the neutron-capture elements Sr, Ba and Eu in the stellar halo of a Milky Way-mass galaxy formed in a hydrodynamical cosmological simulation, and compare them with those of $\alpha$-elements. For this, we implement a novel treatment for chemical enrichment of Type II supernovae which considers the effects of the rotation of massive stars on the chemical yields and differential enrichment according to the life-times of progenitor stars. We find that differential enrichment has a significant impact on the early enrichment of the interstellar medium which is translated into broader element ratio distributions, particularly in the case of the oldest, most metal-poor stars. We find that the [element/Fe] ratios of the $\alpha-$elements O, Mg and Si have systematically lower scatter compared to the neutron-capture elements ratios Sr, Ba and Eu at [Fe/H]$<-2$, which is $\sim 0.1-0.4$ dex for the former and between $\sim 0.5$ and $1$ dex for the latter. The different scatter levels found for the neutron-capture and $\alpha$-elements is consistent with observations of old stars in the Milky Way. Our model also predicts a high scatter for the [Sr/Ba] ratio, which results from the treatment of the fast-rotating stars and the dependence of the chemical yields on the metallicity, mass and rotational velocities. Such chemical patterns appear naturally if the different ejection times associated to stars of different mass are properly described, without the need to invoke for additional mixing mechanisms or a distinct treatment of the $\alpha-$ and neutron-capture elements., Comment: MNRAS accepted

In the standard paradigm of galaxy formation and evolution, the baryonic component of galaxies forms from the collapse and condensation of gas within dark matter haloes, and later grows from continuous accretion of gaseous mass, both in diffuse form and in mergers with other systems. After a first period of rapid and violent halo growth, the gas settles into a rotationally-supported structure, eventually giving rise to the formation of a stellar disc. Stars evolve and return chemically-processed gas and energy to the interstellar medium, mainly through Type II supernova explosions. In the disc region, the cosmological accretion of gas combines with the outflows resulting from supernovae, affecting the hydrodynamical and structural properties of the disc and producing gas flows in the vertical and radial directions. In this work, we use a simulation of the Auriga Project, a suite of magneto-hydrodynamical, zoom-in cosmological simulations of Milky Way-like galaxies, to study the temporal and radial dependencies of gas accretion onto the disc. We also investigate the disc evolution, focusing on the inside-out disc formation scenario, which is one of the fundamental hypotheses of chemical evolution models of the Galaxy., Comment: 3 pages, 3 figures. To appear in the 62nd Bulletin of the Argentine Astronomical Society

In the context of the concordance cosmology, structure formation in the Universe is the result of the amplification, by gravitational effects, of small perturbations in the primeval density field. This results in the formation of structures known as dark matter haloes, where gas collapses and forms stars, giving birth to galaxies. Numerical simulations are an important tool in the theoretical study of galaxy formation and evolution. In the present work, we describe the implementation of a chemical enrichment model in a state-of-the-art cosmological simulation of the Local Group. The simulation includes sub-grid models for the most relevant physical processes. We analyze the chemical and morphological evolution of two galaxies with virial masses similar to that of our Milky Way. For each of the stellar components (disc, bulge and halo), we establish links between their formation history and their chemical evolution. We find that $\alpha$-element (O, Mg, Si) enrichment happens at early stages of evolution, as their main producers are short-lived stars which end their lives as type II supernova explosions. There is also a gradual contamination with the rest of the elements as type Ia supernovae and winds of stars in the asymptotic giant branch occur., Comment: 3 pages, 4 figures. To appear in the 62nd Bulletin of the Argentine Astronomical Society

We present a new model to describe the star formation process in galaxies, which includes the description of the different gas phases -- molecular, atomic, and ionized -- together with its metal content. The model, which will be coupled to cosmological simulations of galaxy formation, will be used to investigate the relation between the star formation rate (SFR) and the formation of molecular hydrogen. The model follows the time evolution of the molecular, atomic and ionized phases in a gas cloud and estimates the amount of stellar mass formed, by solving a set of five coupled differential equations. As expected, we find a positive, strong correlation between the molecular fraction and the initial gas density, which manifests in a positive correlation between the initial gas density and the SFR of the cloud., Comment: 3 pages, 2 figures. To appear in the 62nd Bulletin of the Argentine Astronomical Society

Although galactic winds play a critical role in regulating galaxy formation, hydrodynamic cosmological simulations do not resolve the scales that govern the interaction between winds and the ambient circumgalactic medium (CGM). We implement the Physically Evolved Wind (PhEW) model of Huang et al. (2020) in the GIZMO hydrodynamics code and perform test cosmological simulations with different choices of model parameters and numerical resolution. PhEW adopts an explicit subgrid model that treats each wind particle as a collection of clouds that exchange mass, metals, and momentum with their surroundings and evaporate by conduction and hydrodynamic instabilities as calibrated on much higher resolution cloud scale simulations. In contrast to a conventional wind algorithm, we find that PhEW results are robust to numerical resolution and implementation details because the small scale interactions are defined by the model itself. Compared to conventional wind simulations with the same resolution, our PhEW simulations produce similar galaxy stellar mass functions at $z\geq 1$ but are in better agreement with low-redshift observations at $M_* < 10^{11}M_\odot$ because PhEW particles shed mass to the CGM before escaping low mass halos. PhEW radically alters the CGM metal distribution because PhEW particles disperse metals to the ambient medium as their clouds dissipate, producing a CGM metallicity distribution that is skewed but unimodal and is similar between cold and hot gas. While the temperature distributions and radial profiles of gaseous halos are similar in simulations with PhEW and conventional winds, these changes in metal distribution will affect their predicted UV/X-ray properties in absorption and emission., Comment: 23 pages, 17 figures, MNRAS accepted

For years, the extragalactic community has divided galaxies in two distinct populations. One of them, featuring blue colours, is actively forming stars, while the other is made up of "red-and-dead" objects with negligible star formation. Yet, are these galaxies really dead? Here we would like to highlight that, as previously reported by several independent groups, state-of-the-art cosmological numerical simulations predict the existence of a large number of quenched galaxies that have not formed any star over the last few Gyr. In contrast, observational measurements of large galaxy samples in the nearby Universe suggest that even the most passive systems still form stars at some residual level close to $sSFR\sim10^{-12}~\text{yr}^{-1}$. Unfortunately, extremely low star formation poses a challenge for both approaches. We conclude that, at present, the fraction of truly dead galaxies is still an important open question that must be addressed in order to understand galaxy formation and evolution., Comment: Accepted for publication in MNRAS. 9 pages, 8 figures

We use combined South Pole Telescope (SPT)+Planck temperature maps to analyze the circumgalactic medium (CGM) encompassing 138,235 massive, quiescent 0.5 $\leq$ z $\leq$ 1.5 galaxies selected from data from the Dark Energy Survey (DES) and Wide-Field Infrared Survey Explorer (WISE). Images centered on these galaxies were cut from the 1.85 arcmin resolution maps with frequency bands at 95, 150, and 220 GHz. The images were stacked, filtered, and fit with a gray-body dust model to isolate the thermal Sunyaev-Zel'dovich (tSZ) signal, which is proportional to the total energy contained in the CGM of the galaxies. We separate these $M_{\star} = 10^{10.9} M_\odot$ - $10^{12} M_\odot$ galaxies into 0.1 dex stellar mass bins, detecting tSZ per bin up to $5.6\sigma$ and a total signal-to-noise ratio of $10.1\sigma$. We also detect dust with an overall signal-to-noise ratio of $9.8\sigma$, which overwhelms the tSZ at 150GHz more than in other lower-redshift studies. We correct for the $0.16$ dex uncertainty in the stellar mass measurements by parameter fitting for an unconvolved power-law energy-mass relation, $E_{\rm therm} = E_{\rm therm,peak} \left(M_\star/M_{\star,{\rm peak}} \right)^\alpha$, with the peak stellar mass distribution of our selected galaxies defined as $M_{\star,{\rm peak}}= 2.3 \times 10^{11} M_\odot$. This yields an $E_{\rm therm,peak}= 5.98_{-1.00}^{+1.02} \times 10^{60}$ erg and $\alpha=3.77_{-0.74}^{+0.60}$. These are consistent with $z \approx 0$ observations and within the limits of moderate models of active galactic nuclei (AGN) feedback. We also compute the radial profile of our full sample, which is similar to that recently measured at lower-redshift by Schaan et al. (2021)., Comment: 23 pages, 9 figures, Published in ApJ. Corrected y-axis label/units of Fig. 5 and fixed minor syntax/typos

Galactic winds are crucial to the cosmic cycle of matter, transporting material out of the dense regions of galaxies. Observations show the coexistence of different temperature phases in such winds, which is not easy to explain. We present a set of 3D shock-multicloud simulations that account for radiative heating and cooling at temperatures between $10^2\,\rm K$ and $10^7\,\rm K$. The interplay between shock heating, dynamical instabilities, turbulence, and radiative heating and cooling creates a complex multi-phase flow with a rain-like morphology. Cloud gas fragments and is continuously eroded, becoming efficiently mixed and mass loaded. The resulting warm mixed gas then cools down and precipitates into new dense cloudlets, which repeat the process. Thus, radiative cooling is able to sustain fast-moving dense gas by aiding condensation of gas from warm clouds and the hot wind. In the ensuing outflow, hot gas with temperatures $\gtrsim 10^6\,\rm K$ outruns the warm and cold phases, which reach thermal equilibrium near $\approx 10^4\,\rm K$ and $\approx 10^2\,\rm K$, respectively. Although the volume filling factor of hot gas is higher in the outflow, most of the mass is concentrated in dense gas cloudlets and filaments with these temperatures. More porous multicloud layers result in more vertically extended outflows, and dense gas is more efficiently produced in more compact layers. The cold phase is not accelerated by ram-pressure, but, instead, precipitates from warm and mixed gas out of thermal equilibrium. This cycle can explain the presence of high-velocity H\,{\sc i} gas with $N_{\rm H\,{\scriptstyle I}}=10^{19-21}\,\rm cm^{-2}$ and $\Delta v_{{\rm FWHM}}\lesssim37\,\rm km\,s^{-1}$ in the Galactic centre outflow., Comment: Accepted for publication in MNRAS, 20 pages, 13 figures. This version includes an additional clump-finding analysis in the Appendix

We carry out a suite of simulations of the evolution of cosmic-ray (CR) driven, radiatively-cooled cold clouds embedded in hot material, as found in galactic outflows. In such interactions, CRs stream towards the cloud at the Alfv\'en speed, which decreases dramatically at the cloud boundary, leading to a bottleneck in which pressure builds up in front of the cloud. At the same time, CRs stream along the sides of the cloud, forming a boundary layer where large filaments develop. Shear in this boundary layer is the primary mode of cloud destruction, which is relatively slow in all cases, but slowest in the cases with the lowest Alfv\'en speeds. Thus the CR ray pressure in the bottleneck region has sufficient time to accelerate the cold clouds efficiently. Furthermore, radiative cooling has relatively little impact on these interactions. Our simulations are two-dimensional and limited by a simplified treatment of cosmic-ray dynamics, the neglect of CR heating, and an idealized magnetic field geometry. Nevertheless, our results suggest that cosmic rays, when acting as the primary source of momentum input, are capable of accelerating clouds to velocities comparable to those observed in galaxy outflows., Comment: 14 pages, 10 figures, ApJ in press

We report three-dimensional hydrodynamical simulations of shocks (${\cal M_{\rm shock}}\geq 4$) interacting with fractal multicloud layers. The evolution of shock-multicloud systems consists of four stages: a shock-splitting phase in which reflected and refracted shocks are generated, a compression phase in which the forward shock compresses cloud material, an expansion phase triggered by internal heating and shock re-acceleration, and a mixing phase in which shear instabilities generate turbulence. We compare multicloud layers with narrow ($\sigma_{\rho}=1.9\bar{\rho}$) and wide ($\sigma_{\rho}=5.9\bar{\rho}$) log-normal density distributions characteristic of Mach $\approx 5$ supersonic turbulence driven by solenoidal and compressive modes. Our simulations show that outflowing cloud material contains imprints of the density structure of their native environments. The dynamics and disruption of multicloud systems depend on the porosity and the number of cloudlets in the layers. `Solenoidal' layers mix less, generate less turbulence, accelerate faster, and form a more coherent mixed-gas shell than the more porous `compressive' layers. Similarly, multicloud systems with more cloudlets quench mixing via a shielding effect and enhance momentum transfer. Mass loading of diffuse mixed gas is efficient in all models, but direct dense gas entrainment is highly inefficient. Dense gas only survives in compressive clouds, but has low speeds. If normalised with respect to the shock-passage time, the evolution shows invariance for shock Mach numbers $\geq10$ and different cloud-generating seeds, and slightly weaker scaling for lower Mach numbers and thinner cloud layers. Multicloud systems also have better convergence properties than single-cloud systems, with a resolution of $8$ cells per cloud radius being sufficient to capture their overall dynamics., Comment: Accepted for publication in MNRAS; 19 pages plus an appendix; 14 figures

We report on a Hubble Space Telescope search for rest-frame ultraviolet emission from the host galaxies of five far-infrared-luminous $z\simeq{}6$ quasars and the $z=5.85$ hot-dust free quasar SDSS J0005-0006. We perform 2D surface brightness modeling for each quasar using a Markov-Chain Monte-Carlo estimator, to simultaneously fit and subtract the quasar point source in order to constrain the underlying host galaxy emission. We measure upper limits for the quasar host galaxies of $m_J>22.7$ mag and $m_H>22.4$ mag, corresponding to stellar masses of $M_\ast<2\times10^{11}M_\odot$. These stellar mass limits are consistent with the local $M_{\textrm{BH}}$-$M_\ast$ relation. Our flux limits are consistent with those predicted for the UV stellar populations of $z\simeq6$ host galaxies, but likely in the presence of significant dust ($\langle A_{\mathrm{UV}}\rangle\simeq 2.6$ mag). We also detect a total of up to 9 potential $z\simeq6$ quasar companion galaxies surrounding five of the six quasars, separated from the quasars by 1.4''-3.2'', or 8.4-19.4 kpc, which may be interacting with the quasar hosts. These nearby companion galaxies have UV absolute magnitudes of -22.1 to -19.9 mag, and UV spectral slopes $\beta$ of -2.0 to -0.2, consistent with luminous star-forming galaxies at $z\simeq6$. These results suggest that the quasars are in dense environments typical of luminous $z\simeq6$ galaxies. However, we cannot rule out the possibility that some of these companions are foreground interlopers. Infrared observations with the James Webb Space Telescope will be needed to detect the $z\simeq6$ quasar host galaxies and better constrain their stellar mass and dust content., Comment: 22 pages, 13 figures. Accepted for publication in ApJ

The circumgalactic medium (CGM) of nearby star-forming galaxies shows clear indications of OVI absorption accompanied by little to no detectable NV absorption. This unusual spectral signature, accompanied by highly non-uniform absorption from lower ionization state species, indicates that the CGM must be viewed as a dynamic, multiphase medium, such as occurs in the presence of turbulence. Motivated by previous isotropic turbulent simulations, we carry out chemodynamical simulations of stratified media in a Navarro-Frenk-White (NFW) gravitational potential with a total mass of $10^{12}$ solar masses and turbulence that decreases radially. The simulations assume a metallicity of 0.3 solar, a redshift zero metagalatic UV background, and they track ionizations, recombinations, and species-by-species radiative cooling using the MAIHEM package. We compare a suite of ionic column densities with the COS-Halos sample of low-redshift star-forming galaxies. Turbulence with an average one-dimensional velocity dispersion approximately 40 km/s, corresponding to an energy injection rate of approximately $10^{49}$ erg/yr, produces a CGM that matches many of the observed ionic column densities and ratios. In this simulation, the NVI to OVI ratio is suppressed from its equilibrium value due to a combination of radiative cooling and cooling from turbulent mixing. This level of turbulence is consistent with expectations from observations of better constrained, higher-mass systems, and could be sustained by energy input from supernovae, gas inflows, and dynamical friction from dark matter subhalos. We also conduct a higher resolution run which yields smaller-scale structures, but remains in agreement with observations., Comment: 24 pages, 19 Figures, ApJ, in press

The propagation and evolution of cold galactic winds in galactic haloes is crucial to galaxy formation models. However, modelling of this process in hydrodynamic simulations of galaxy formation is over-simplified owing to a lack of numerical resolution and often neglects critical physical processes such as hydrodynamic instabilities and thermal conduction. We propose an analytic model, Physically Evolved Winds (PhEW), that calculates the evolution of individual clouds moving supersonically through a uniform ambient medium. Our model reproduces predictions from very high resolution cloud-crushing simulations that include isotropic thermal conduction over a wide range of physical conditions. We discuss the implementation of this model into cosmological hydrodynamic simulations of galaxy formation as a sub-grid prescription to model galactic winds more robustly both physically and numerically., Comment: 21 pages, 9 figures, accepted for publication in MNRAS

Motivated by observations of outflowing galaxies, we investigate the combined impact of magnetic fields and radiative cooling on the evolution of cold clouds embedded in a hot wind. We perform a collection of three-dimensional adaptive mesh refinement, magnetohydrodynamical simulations that span two resolutions, and include fields that are aligned and transverse to the oncoming, super-Alfv\'enic material. Aligned fields have little impact on the overall lifetime of the clouds over the non-magnetized case, although they do increase the mixing between the wind and cloud material by a factor of $\approx 3.$ Transverse fields lead to magnetic draping, which isolates the clouds, but they also squeeze material in the direction perpendicular to the field lines, which leads to rapid mass loss. A resolution study suggests that the magnetized simulations have somewhat better convergence properties than non-magnetized simulations, and that a resolution of 64 zones per cloud radius is sufficient to accurately describe these interactions. We conclude that the combined effects of radiative cooling and magnetic fields are dependent on field orientation, but are unlikely to enhance cloud lifetimes beyond the effect of radiative cooling alone., Comment: 15 pages, 14 figures, accepted to ApJ

Single-phase photoionization equilibrium (PIE) models are often used to infer the underlying physical properties of galaxy halos probed in absorption with ions at different ionization potentials. To incorporate the effects of turbulence, we use the MAIHEM code to model an isotropic turbulent medium exposed to a redshift zero metagalactic UV background, while tracking the ionizations, recombinations, and species-by-species radiative cooling for a wide range of ions. By comparing observations and simulations over a wide range of turbulent velocities, densities, and metallicity with a Markov chain Monte Carlo technique, we find that MAIHEM models provide an equally good fit to the observed low-ionization species compared to PIE models, while reproducing at the same time high-ionization species such as \ion{Si}{4} and \ion{O}{6}. By including multiple phases, MAIHEM models favor a higher metallicity ($Z/Z_\odot \approx 40\%$) for the circumgalactic medium compared to PIE models. Furthermore, all of the solutions require some amount of turbulence ($\sigma_{\rm 3D} \geqslant 26\ {\rm km}\ {\rm s}^{-1}$). Correlations between turbulence, metallicity, column density, and impact parameter are discussed alongside mechanisms that drive turbulence within the halo., Comment: 19 pages, 13 figures, accepted in ApJ

Outflows are a pervasive feature of mechanical feedback from super star clusters (SSC) in starburst galaxies, playing a fundamental role in galaxy evolution. Observations are now starting to confirm that outflows can undergo catastrophic cooling, suppressing adiabatic superwinds. Here we present a suite of one-dimensional, hydrodynamic simulations that study the ionization structure of these outflows and the resulting line emission generated by the cooling gas. We use the non-equilibrium atomic chemistry package within MAIHEM, our modified version of FLASH, which evolves the ionization state of the gas and computes the total cooling rate on an ion-by-ion basis. We find that catastrophically cooling models produce strong nebular line emission compared to adiabatic outflows. We also show that such models exhibit non-equilibrium conditions, thereby generating more highly ionized states than equivalent equilibrium models. When including photoionization from the parent SSC, catastrophically cooling models show strong C IV {\lambda}1549 and O VI {\lambda}1037 emission. For density bounded photoionization, He II {\lambda}1640, {\lambda}4686, C III] {\lambda}1908, Si IV {\lambda}1206, and Si III {\lambda}1400 are also strongly enhanced. These lines are seen in extreme starbursts where catastrophic cooling is likely to occur, suggesting that they may serve as diagnostics of such conditions. The higher ionization generated by these flows may help to explain line emission that cannot be attributed to SSC photoionization alone., Comment: 29 pages, 13 figures, accepted to ApJ

We study a turbulent helical dynamo in a periodic domain by solving the ideal magnetohydrodynamic (MHD) equations with the FLASH code using the divergence-cleaning eight-wave method and compare our results with direct numerical simulations (DNS) using the Pencil Code. At low resolution, FLASH reproduces the DNS results qualitatively by developing the large-scale magnetic field expected from DNS, but at higher resolution, no large-scale magnetic field is obtained. In all those cases in which a large-scale magnetic field is generated, the ideal MHD results yield too little power at small scales. As a consequence, the small-scale current helicity is too small compared with that of the DNS. The resulting net current helicity has then always the wrong sign, and its statistical average also does not approach zero at late times, as expected from the DNS. Our results have implications for astrophysical dynamo simulations of stellar and galactic magnetism using ideal MHD codes., Comment: 9 pages, 14 figures, 2 tables, ApJ 889, 55 (2020)