arXiv subjects

Dylan Nelson

Publications and source records attributed to Dylan Nelson.

At least 73 records · Page 4Linked to original sources

arXiv2023

VERTICO and IllustrisTNG: The spatially resolved effects of environment on galactic gas

It has been shown in previous publications that the TNG100 simulation quantitatively reproduces the observed reduction in each of the total atomic and total molecular hydrogen gas for galaxies within massive halos, i.e.~dense environments. In this Letter, we study how well TNG50 reproduces the resolved effects of a Virgo-like cluster environment on the gas surface densities of satellite galaxies with $m_* > \! 10^9\,{\rm M}_\odot$ and ${\rm SFR} \! > 0.05\,{\rm M}_\odot\,{\rm yr}^{-1}$. We select galaxies in the simulation that are analogous to those in the HERACLES and VERTICO surveys, and mock-observe them to the common specifications of the data. Although TNG50 does not quantitatively match the observed gas surface densities in the centers of galaxies, the simulation does qualitatively reproduce the trends of gas truncation and central density suppression seen in VERTICO in both HI and H$_2$. This result promises that modern cosmological hydrodynamic simulations can be used to reliably model the post-infall histories of cluster satellite galaxies.

astro-ph.GA↗

arXiv2023

Azimuthal Anisotropy of Magnetic Fields in the Circumgalactic Medium Driven by Galactic Feedback Processes

We use the TNG50 cosmological magnetohydrodynamical simulation of the IllustrisTNG project to show that magnetic fields in the circumgalactic medium (CGM) have significant angular structure. This azimuthal anisotropy at fixed distance is driven by galactic feedback processes that launch strong outflows into the halo, preferentially along the minor axes of galaxies. These feedback-driven outflows entrain strong magnetic fields from the interstellar medium, dragging fields originally amplified by small-scale dynamos into the CGM. At the virial radius, $z=0$ galaxies with M$_\star \sim 10^{10}\,\rm{M_\odot}$ show the strongest anisotropy ($\sim 0.35$ dex). This signal weakens with decreasing impact parameter, and is also present but weaker for lower mass as well as higher mass galaxies. Creating mock Faraday rotation measure (RM) sightlines through the simulated volume, we find that the angular RM trend is qualitatively consistent with recent observational measurements. We show that rich structure is present in the circumgalactic magnetic fields of galaxies. However, TNG50 predicts small RM amplitudes in the CGM that make detection difficult as a result of other contributions along the line of sight.

astro-ph.GA↗

arXiv2023

IllustrisTNG in the HSC-SSP: image data release and the major role of mini mergers as drivers of asymmetry and star formation

At fixed galaxy stellar mass, there is a clear observational connection between structural asymmetry and offset from the star forming main sequence, $Δ$SFMS. Herein, we use the TNG50 simulation to investigate the relative roles of major mergers (stellar mass ratios $μ\geq0.25$), minor ($0.1 \leq μ< 0.25$), and mini mergers ($0.01 \leq μ< 0.1$) in driving this connection amongst star forming galaxies (SFGs). We use dust radiative transfer post-processing with SKIRT to make a large, public collection of synthetic Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) images of simulated TNG galaxies over $0.1\leq z \leq 0.7$ with $\log M_{\star} / \mathrm{M}_{\odot}\geq9$ ($\sim750$k images). Using their instantaneous SFRs, known merger histories/forecasts, and HSC-SSP asymmetries, we show (1) that TNG50 SFGs qualitatively reproduce the observed trend between $Δ$SFMS and asymmetry and (2) a strikingly similar trend emerges between $Δ$SFMS and the time-to-coalescence for mini mergers. Controlling for redshift, stellar mass, environment, and gas fraction, we show that individual mini merger events yield small enhancements in SFRs and asymmetries that are sustained on long timescales (at least $\sim3$ Gyr after coalescence, on average) -- in contrast to major/minor merger remnants which peak at much greater amplitudes but are consistent with controls only $\sim1$ Gyr after coalescence. Integrating the boosts in SFRs and asymmetries driven by $μ\geq0.01$ mergers since $z=0.7$ in TNG50 SFGs, we show that mini mergers are responsible for (i) $55$ per cent of all merger-driven star formation and (ii) $70$ per cent of merger-driven asymmetric structure. Due to their relative frequency and prolonged boost timescales, mini mergers dominate over their minor and major counterparts in driving star formation and asymmetry in SFGs.

astro-ph.GA↗

arXiv2023

Mapping the Intracluster Medium in the Era of High-resolution X-ray Spectroscopy

High-resolution spectroscopy in soft X-rays will open a new window to map multiphase gas in galaxy clusters and probe physics of the intracluster medium (ICM), including chemical enrichment histories, circulation of matter and energy during large-scale structure evolution, stellar and black hole feedback, halo virialization, and gas mixing processes. An eV-level spectral resolution, large field-of-view, and effective area are essential to separate cluster emissions from the Galactic foreground and efficiently map the cluster outskirts. Several mission concepts that meet these criteria have been proposed recently, e.g., LEM, HUBS, and SuperDIOS. This theoretical study explores what information on ICM physics could be recovered with such missions and the associated challenges. We emphasize the need for a comprehensive comparison between simulations and observations to interpret the high-resolution spectroscopic observations correctly. Using Line Emission Mapper (LEM) characteristics as an example, we demonstrate that it enables the use of soft X-ray emission lines (e.g., O VII/VIII and Fe-L complex) from the cluster outskirts to measure the thermodynamic, chemical, and kinematic properties of the gas up to $r_{200}$ and beyond. By generating mock observations with full backgrounds, analysing their images/spectra with observational approaches, and comparing the recovered characteristics with true ones from simulations, we develop six key science drivers for future missions, including the exploration of multiphase gas in galaxy clusters (e.g., temperature fluctuations, phase-space distributions), metallicity, ICM gas bulk motions and turbulence power spectra, ICM-cosmic filament interactions, and advances for cluster cosmology.

astro-ph.HE↗

arXiv2023

Imposters among us: globular cluster kinematics and the halo mass of ultra-diffuse galaxies in clusters

The velocity dispersion of globular clusters (GCs) around ultra-diffuse galaxies (UDGs) in the Virgo cluster spans a wide range, including cases where GC kinematics suggest halos as massive as (or even more massive than) that of the Milky Way around these faint dwarfs. We analyze the catalogs of GCs derived in post-processing from the TNG50 cosmological simulation to study the GC system kinematics and abundance of simulated UDGs in galaxy groups and clusters. UDGs in this simulation reside exclusively in dwarf-mass halos with $M_{200} \sim 10^{11}$ M$_{\odot}$. When considering only GCs gravitationally bound to simulated UDGs, we find GCs properties that overlap well with several observational measurements for UDGs. In particular, no bias towards overly massive halos is inferred from the study of bound GCs, confirming that GCs are good tracers of UDG halo mass. However, we find that contamination by intra-cluster GCs may, in some cases, substantially increase velocity dispersion estimates when performing projected mock observations of our sample. We caution that targets with less than $10$ GC tracers are particularly prone to severe uncertainties.Measuring the stellar kinematics of the host galaxy should help confirm the unusually massive halos suggested by GC kinematics around some UDGs

astro-ph.GA↗

arXiv2023

X-ray metal line emission from the hot circumgalactic medium: probing the effects of supermassive black hole feedback

We derive predictions from state-of-the-art cosmological galaxy simulations for the spatial distribution of the hot circumgalactic medium (CGM, ${\rm [0.1-1]R_{200c}}$) through its emission lines in the X-ray soft band ($[0.3-1.3]$ keV). In particular, we compare IllustrisTNG, EAGLE, and SIMBA and focus on galaxies with stellar mass $10^{10-11.6}\, \MSUN$ at $z=0$. The three simulation models return significantly different surface brightness radial profiles of prominent emission lines from ionized metals such as OVII(f), OVIII, and FeXVII as a function of galaxy mass. Likewise, the three simulations predict varying azimuthal distributions of line emission with respect to the galactic stellar planes, with IllustrisTNG predicting the strongest angular modulation of CGM physical properties at radial range ${\gtrsim0.3-0.5\,R_{200c}}$. This anisotropic signal is more prominent for higher-energy lines, where it can manifest as X-ray eROSITA-like bubbles. Despite different models of stellar and supermassive black hole (SMBH) feedback, the three simulations consistently predict a dichotomy between star-forming and quiescent galaxies at the Milky-Way and Andromeda mass range, where the former are X-ray brighter than the latter. This is a signature of SMBH-driven outflows, which are responsible for quenching star formation. Finally, we explore the prospect of testing these predictions with a microcalorimeter-based X-ray mission concept with a large field-of-view. Such a mission would probe the extended hot CGM via soft X-ray line emission, determine the physical properties of the CGM, including temperature, from the measurement of line ratios, and provide critical constraints on the efficiency and impact of SMBH feedback on the CGM.

astro-ph.GA↗

arXiv2023

Reducing the qubit requirement of Jordan-Wigner encodings of $N$-mode, $K$-fermion systems from $N$ to $\lceil \log_2 {N \choose K} \rceil$

To simulate a fermionic system on a quantum computer, it is necessary to encode the state of the fermions onto qubits. Fermion-to-qubit mappings such as the Jordan-Wigner and Bravyi-Kitaev transformations do this using $N$ qubits to represent systems of $N$ fermionic modes. In this work, we demonstrate that for particle number conserving systems of $K$ fermions and $N$ modes, the qubit requirement can be reduced to the information theoretic minimum of $\lceil \log_2 {N \choose K} \rceil$. This will improve the feasibility of simulation of molecules and many-body systems on near-term quantum computers with limited qubit number.

quant-ph↗

arXiv2023

Zooming in on the circumgalactic medium: resolving small-scale gas structure with the GIBLE cosmological simulations

We introduce Project GIBLE (Gas Is Better resoLved around galaxiEs), a suite of cosmological zoom-in simulations where gas in the circumgalactic medium (CGM) is preferentially simulated at ultra-high numerical resolution. Our initial sample consists of eight galaxies, all selected as Milky Way-like galaxies at $z=0$ from the TNG50 simulation. Using the same galaxy formation model as IllustrisTNG, and the moving-mesh code AREPO, we re-simulate each of these eight galaxies maintaining a resolution equivalent to TNG50-2 ($m_{\rm{gas}}$ $\sim$ $8 \times 10^5 {\rm M}_{\odot}$). However, we use our super-Lagrangian refinement scheme to more finely resolve gas in the CGM around these galaxies. Our highest resolution runs achieve 512 times better mass resolution ($\sim$ $10^3 {\rm M}_{\odot}$). This corresponds to a median spatial resolution of $\sim$ $75$ pc at $0.15~R_{\rm{200,c}}$, which coarsens with increasing distance to $\sim$ $700$ pc at the virial radius. We make predictions for the covering fractions of several observational tracers of multi-phase CGM gas: HI, MgII, CIV and OVII. We then study the impact of improved resolution on small scale structure. While the abundance of the smallest cold, dense gas clouds continues to increase with improving resolution, the number of massive clouds is well converged. We conclude by quantifying small scale structure with the velocity structure function and the auto-correlation function of the density field, assessing their resolution dependence. The GIBLE cosmological hydrodynamical simulations enable us to improve resolution in a computationally efficient manner, thereby achieving numerical convergence of a subset of key CGM gas properties and observables.

astro-ph.GA↗

arXiv2023

Resonant scattering of the OVII X-ray emission line in the circumgalactic medium of TNG50 galaxies

We study the impact of resonantly scattered X-ray line emission on the observability of the hot circumgalactic medium (CGM) of galaxies. We apply a Monte Carlo radiative transfer post-processing analysis to the high-resolution TNG50 cosmological magnetohydrodynamical galaxy formation simulation. This allows us to model the resonant scattering of OVII(r) X-ray photons within the complex, multi-phase, multi-scale CGM. The resonant transition of the OVII He-like triplet is one of the brightest, and most promising, X-ray emission lines for detecting the hot CGM and measuring its physical properties. We focus on galaxies with stellar masses 10 < log(M*/Msun) < 11 at z ~ 0. After constructing a model for OVII(r) emission from the central galaxy as well as from CGM gas, we forward model these intrinsic photons to derive observable surface brightness maps. We find that scattering significantly boosts the observable OVII(r) surface brightness of the extended and diffuse CGM. This enhancement can be large -- an order of magnitude on average at a distance of 200 projected kpc for high-mass M* = 10^10.7 Msun galaxies. The enhancement is larger for lower mass galaxies, and can even reach a factor of 100, across the extended CGM. Galaxies with higher star formation rates, AGN luminosities, and central OVII(r) luminosities all have larger scattering enhancements, at fixed stellar mass. Our results suggest that next-generation X-ray spectroscopic missions including XRISM, LEM, ATHENA, and HUBS -- which aim to detect the hot CGM in emission -- could specifically target halos with significant enhancements due to resonant scattering.

astro-ph.GA↗

arXiv2023

Circumgalactic Medium on the Largest Scales: Detecting X-ray Absorption Lines with Large-Area Microcalorimeters

The circumgalactic medium (CGM) plays a crucial role in galaxy evolution as it fuels star formation, retains metals ejected from the galaxies, and hosts gas flows in and out of galaxies. For Milky Way-type and more massive galaxies, the bulk of the CGM is in hot phases best accessible at X-ray wavelengths. However, our understanding of the CGM remains largely unconstrained due to its tenuous nature. A promising way to probe the CGM is via X-ray absorption studies. Traditional absorption studies utilize bright background quasars, but this method probes the CGM in a pencil beam, and, due to the rarity of bright quasars, the galaxy population available for study is limited. Large-area, high spectral resolution X-ray microcalorimeters offer a new approach to exploring the CGM in emission and absorption. Here, we demonstrate that the cumulative X-ray emission from cosmic X-ray background sources can probe the CGM in absorption. We construct column density maps of major X-ray ions from the Magneticum simulation and build realistic mock images of nine galaxies to explore the detectability of X-ray absorption lines arising from the large-scale CGM. We conclude that the OVII absorption line is detectable around individual massive galaxies at the $3σ-6σ$ confidence level. For Milky Way-type galaxies, the OVII and OVIII absorption lines are detectable at the $\sim\,6σ$ and $\sim\,3σ$ levels even beyond the virial radius when co-adding data from multiple galaxies. This approach complements emission studies, does not require additional exposures, and will allow probing of the baryon budget and the CGM at the largest scales.

astro-ph.GA↗

arXiv2023

The BarYon CYCLE Project (ByCycle): Identifying and Localizing MgII Metal Absorbers with Machine Learning

The upcoming ByCycle project on the VISTA/4MOST multi-object spectrograph will offer new prospects of using a massive sample of $\sim 1$ million high spectral resolution ($R$ = 20,000) background quasars to map the circumgalactic metal content of foreground galaxies (observed at $R$ = 4000 - 7000), as traced by metal absorption. Such large surveys require specialized analysis methodologies. In the absence of early data, we instead produce synthetic 4MOST high-resolution fibre quasar spectra. To do so, we use the TNG50 cosmological magnetohydrodynamical simulation, combining photo-ionization post-processing and ray tracing, to capture MgII ($\lambda2796$, $\lambda2803$) absorbers. We then use this sample to train a Convolutional Neural Network (CNN) which searches for, and estimates the redshift of, MgII absorbers within these spectra. For a test sample of quasar spectra with uniformly distributed properties ($λ_{\rm{MgII,2796}}$, $\rm{EW}_{\rm{MgII,2796}}^{\rm{rest}} = 0.05 - 5.15$ Å, $\rm{SNR} = 3 - 50$), the algorithm has a robust classification accuracy of 98.6 per cent and a mean wavelength accuracy of 6.9 Å. For high signal-to-noise spectra ($\rm{SNR > 20}$), the algorithm robustly detects and localizes MgII absorbers down to equivalent widths of $\rm{EW}_{\rm{MgII,2796}}^{\rm{rest}} = 0.05$ Å. For the lowest SNR spectra ($\rm{SNR=3}$), the CNN reliably recovers and localizes EW$_{\rm{MgII,2796}}^{\rm{rest}}$ $\geq$ 0.75 Å\, absorbers. This is more than sufficient for subsequent Voigt profile fitting to characterize the detected MgII absorbers. We make the code publicly available through GitHub. Our work provides a proof-of-concept for future analyses of quasar spectra datasets numbering in the millions, soon to be delivered by the next generation of surveys.

astro-ph.GA↗

arXiv2023

MUSE-ALMA Halos XI: Gas flows in the circumgalactic medium

The flow of gas into and out of galaxies leaves traces in the circumgalactic medium which can then be studied using absorption lines towards background quasars. We analyse 27 log(N_HI) > 18.0 HI absorbers at z = 0.2 to 1.4 from the MUSE-ALMA Halos survey with at least one galaxy counterpart within a line of sight velocity of +/-500 km s^{-1}. We perform 3D kinematic forward modelling of these associated galaxies to examine the flow of dense, neutral gas in the circumgalactic medium. From the VLT/MUSE, HST broadband imaging and VLT/UVES and Keck/HIRES high-resolution UV quasar spectroscopy observations, we compare the impact parameters, star-formation rates and stellar masses of the associated galaxies with the absorber properties. We find marginal evidence for a bimodal distribution in azimuthal angles for strong HI absorbers, similar to previous studies of the MgII and OVI absorption lines. There is no clear metallicity dependence on azimuthal angle and we suggest a larger sample of absorbers are required to fully test the relationship predicted by cosmological hydrodynamical simulations. A case-by-case study of the absorbers reveals that ten per cent of absorbers are consistent with gas accretion, up to 30 per cent trace outflows while the remainder trace gas in the galaxy disk, the intragroup medium and low-mass galaxies below the MUSE detection limit. Our results highlight that the baryon cycle directly affects the dense neutral gas required for star-formation and plays a critical role in galaxy evolution.

astro-ph.GA↗

arXiv2023

Satellites of Milky Way- and M31-like galaxies with TNG50: quenched fractions, gas content, and star formation histories

We analyse the quenched fractions, gas content, and star formation histories of ~1200 satellite galaxies with $M_* \geq 5 \times 10^6~{\rm M}_\odot$ around 198 Milky Way- (MW) and Andromeda-like (M31) hosts in TNG50, the highest-resolution simulation of IllustrisTNG. Satellite quenched fractions are larger for smaller masses, for smaller distances to their host galaxy, and in the more massive M31-like compared to MW-like hosts. As satellites cross their host's virial radius, their gas content drops: most satellites within 300 kpc lack detectable gas reservoirs at $z=0$, unless they are massive like the Magellanic Clouds and M32. Nevertheless, their stellar assembly exhibits a large degree of diversity. On average, the cumulative star formation histories are more extended for brighter, more massive satellites with a later infall, and for those in less massive hosts. Based on these relationships, we can even infer infall periods for observedMWand M31 dwarfs: e.g. 0-4 Gyr ago for the Magellanic Clouds and Leo I, 4-8 and 0-2 Gyr ago for M32 and IC 10, respectively. Ram pressure stripping (in combination with tidal stripping) deprives TNG50 satellites of their gas reservoirs and ultimately quenches their star formation, even though only a few per cent of the present-day satellites around the 198 TNG50 MW/M31-like hosts appear as jellyfish. The typical time since quenching for currently quenched TNG50 satellites is $6.9^{+2.5}_{-3.3}~{\rm Gyr}$ ago. The TNG50 results are consistent with the quenched fractions and stellar assembly of observed MW and M31 satellites, however, satellites of the SAGA survey with $M_* \sim 10^{8-9}~{\rm M}_\odot$ exhibit lower quenched fractions than TNG50 and other, observed analogues.

astro-ph.GA↗

arXiv2023

Jellyfish galaxies with the IllustrisTNG simulations -- Citizen-science results towards large distances, low-mass hosts, and high redshifts

We present the ``Cosmological Jellyfish'' project - a citizen-science classification program to identify jellyfish galaxies within the IllustrisTNG cosmological simulations. Jellyfish (JF) are satellite galaxies that exhibit long trailing gas features -- `tails' -- extending from their stellar body. Their distinctive morphology arises due to ram-pressure stripping (RPS) as they move through the background gaseous medium. Using the TNG50 and TNG100 simulations, we construct a sample of $\sim 80,000$ satellite galaxies spanning an unprecedented range of stellar masses, $10^{8.3-12.3}\,\mathrm{M_\odot}$, and host masses of $M_\mathrm{200,c}=10^{10.4-14.6}\,\mathrm{M_\odot}$ back to $z=2$ \citep[extending the work of][]{yun_jellyfish_2019}. Based on this sample, $\sim 90,000$ galaxy images were presented to volunteers in a citizen-science project on the Zooniverse platform who were asked to determine if each galaxy image resembles a jellyfish. Based on volunteer votes, each galaxy was assigned a score determining if it is a JF or not. This paper describes the project, the inspected satellite sample, the methodology, and the classification process that resulted in a dataset of $5,307$ visually-identified jellyfish galaxies. We find that JF galaxies are common in nearly all group- and cluster-sized systems, with the JF fraction increasing with host mass and decreasing with satellite stellar mass. We highlight JF galaxies in three relatively unexplored regimes: low-mass hosts of $M_\mathrm{200,c}\sim10^{11.5-13}\,\mathrm{M_\odot}$, radial positions within hosts exceeding the virial radius $R_\mathrm{200,c}$, and at high redshift up to $z=2$. The full dataset of our jellyfish scores is publicly available and can be used to select and study JF galaxies in the IllustrisTNG simulations.

astro-ph.GA↗

arXiv2023

Line Emission Mapper (LEM): Probing the physics of cosmic ecosystems

The Line Emission Mapper (LEM) is an X-ray Probe for the 2030s that will answer the outstanding questions of the Universe's structure formation. It will also provide transformative new observing capabilities for every area of astrophysics, and to heliophysics and planetary physics as well. LEM's main goal is a comprehensive look at the physics of galaxy formation, including stellar and black-hole feedback and flows of baryonic matter into and out of galaxies. These processes are best studied in X-rays, and emission-line mapping is the pressing need in this area. LEM will use a large microcalorimeter array/IFU, covering a 30x30' field with 10" angular resolution, to map the soft X-ray line emission from objects that constitute galactic ecosystems. These include supernova remnants, star-forming regions, superbubbles, galactic outflows (such as the Fermi/eROSITA bubbles in the Milky Way and their analogs in other galaxies), the Circumgalactic Medium in the Milky Way and other galaxies, and the Intergalactic Medium at the outskirts and beyond the confines of galaxies and clusters. LEM's 1-2 eV spectral resolution in the 0.2-2 keV band will make it possible to disentangle the faintest emission lines in those objects from the bright Milky Way foreground, providing groundbreaking measurements of the physics of these plasmas, from temperatures, densities, chemical composition to gas dynamics. While LEM's main focus is on galaxy formation, it will provide transformative capability for all classes of astrophysical objects, from the Earth's magnetosphere, planets and comets to the interstellar medium and X-ray binaries in nearby galaxies, AGN, and cooling gas in galaxy clusters. In addition to pointed observations, LEM will perform a shallow all-sky survey that will dramatically expand the discovery space.

astro-ph.IM↗

arXiv2023

Metal line emission from galaxy haloes at z~1

We present a study of the metal-enriched halo gas, traced using MgII and [OII] emission lines, in two large, blind galaxy surveys - the MUSE (Multi Unit Spectroscopic Explorer) Analysis of Gas around Galaxies (MAGG) and the MUSE Ultra Deep Field (MUDF). By stacking a sample of ~600 galaxies (stellar masses M* ~10^{6-12} Msun), we characterize for the first time the average metal line emission from a general population of galaxy haloes at 0.7 <= z <= 1.5. The MgII and [OII] line emission extends farther out than the stellar continuum emission, on average out to ~25 kpc and ~45 kpc, respectively, at a surface brightness (SB) level of 10^{-20} erg/s/cm2/arcsec2. The radial profile of the MgII SB is shallower than that of the [OII], suggesting that the resonant MgII emission is affected by dust and radiative transfer effects. The [OII] to MgII SB ratio is ~3 over ~20-40 kpc, also indicating a significant in situ origin of the extended metal emission. The average SB profiles are intrinsically brighter by a factor ~2-3 and more radially extended by a factor of ~1.3 at 1.0 < z <= 1.5 than at 0.7 <= z <= 1.0. The average extent of the metal emission also increases independently with increasing stellar mass and in overdense group environments. When considering individual detections, we find extended [OII] emission up to ~50 kpc around ~30-40 percent of the group galaxies, and extended (~30-40 kpc) MgII emission around two z~1 quasars in groups, which could arise from outflows or environmental processes.

astro-ph.GA↗

arXiv2023

Milky Way and Andromeda analogs from the TNG50 simulation

We present the properties of Milky Way- and Andromeda-like (MW/M31-like) galaxies simulated within TNG50, the highest-resolution run of the IllustrisTNG suite of $Λ$CDM magneto-hydrodynamical simulations. We introduce our fiducial selection for MW/M31 analogs, which we propose for direct usage as well as for reference in future analyses. TNG50 contains 198 MW/M31 analogs, i.e. galaxies with stellar disky morphology, with a stellar mass in the range of $M_* = 10^{10.5 - 11.2}$ Msun, and within a MW-like Mpc-scale environment at z=0. These are resolved with baryonic (dark matter) mass resolution of $8.5\times10^4$ Msun ($4.5\times10^5$ Msun) and $\sim150$ pc of average spatial resolution in the star-forming regions: we therefore expand by many factors (2 orders of magnitude) the sample size of cosmologically-simulated analogs with similar ($\times 10$ better) numerical resolution. The majority of TNG50 MW/M31 analogs at $z=0$ exhibit a bar, 60 per cent are star-forming, the sample includes 3 Local Group (LG)-like systems, and a number of galaxies host one or more satellites as massive as e.g. the Magellanic Clouds. Even within such a relatively narrow selection, TNG50 reveals a great diversity in galaxy and halo properties, as well as in past histories. Within the TNG50 sample, it is possible to identify several simulated galaxies whose integral and structural properties are consistent, one or more at a time, with those measured for the Galaxy and Andromeda. With this paper, we document and release a series of broadly applicable data products that build upon the IllustrisTNG public release and aim to facilitate easy access and analysis by public users. These include datacubes across snapshots ($0 \le z \le 7$) for each TNG50 MW/M31-like galaxy, and a series of value-added catalogs that will be continually expanded to provide a convenient and up to date community resource.

astro-ph.GA↗

arXiv2023

Disk flaring with TNG50: diversity across Milky Way and M31 analogs

We use the sample of 198 Milky Way (MW) and Andromeda (M31) analogs from TNG50 to quantify the level of disk flaring predicted by a modern, high-resolution cosmological hydrodynamical simulation. Disk flaring refers to the increase of vertical stellar disk height with galactocentric distance. The TNG50 galaxies are selected to have stellar disky morphology, a stellar mass in the range of $M_* = 10^{10.5 - 11.2}~\rm{M_{\odot}}$, and a MW-like Mpc-scale environment at $z=0$. The stellar disks of such TNG50 MW/M31 analogs exhibit a wide diversity of structural properties, including a number of galaxies with disk scalelength and thin and thick disk scaleheights that are comparable to those measured or inferred for the Galaxy and Andromeda. With one set of physical ingredients, TNG50 returns a large variety of flaring flavours and amounts, also for mono-age stellar populations. With this paper, we hence propose a non-parametric characterization of flaring. The typical MW/M31 analogs exhibit disk scaleheights that are $1.5-2$ times larger in the outer than in the inner regions of the disk for both old and young stellar populations, but with a large galaxy-to-galaxy variation. Which stellar population flares more, and by how much, also varies from galaxy to galaxy. TNG50 de facto brackets existing observational constraints for the Galaxy and all previous numerical findings. A link between the amount of flaring and the $z=0$ global galaxy structural properties or merger history is complex. However, a connection between the scaleheights and the local stellar vertical kinematics and gravitational potential is clearly in place.

astro-ph.GA↗