Semi-analytic Model Of Galaxy Formation Research Articles

Galaxy catalogs from the Sage Semi-Analytic Model calibrated on The Three Hundred hydrodynamical simulations: A method to push the limits toward lower mass galaxies in dark matter only clusters simulations

The new generation of upcoming deep photometric and spectroscopic surveys will allow us to measure the astrophysical properties of faint galaxies in massive clusters. This would demand to produce simulations of galaxy clusters with better mass resolution than the ones available today if we want to make comparisons between the upcoming observations and predictions of cosmological models. But producing full-physics hydrodynamical simulations of the most massive clusters is not an easy task. This would involve billions of computational elements to reliably resolve low mass galaxies similar to those measured in observations. On the other hand, dark matter only simulations of cluster size halos can be done with much larger mass resolution but at the cost of having to apply a model that populate galaxies within each of the subhalos in these simulations. In this paper we present the results of a new set of dark matter only simulations with different mass resolutions within the The Three Hundred project. We have generated catalogs of galaxies with stellar and luminosity properties by applying the Sage Semi-Analytical Model of galaxy formation. To obtain the catalogs consistent with the results from hydrodynamical simulations, the internal physical parameters of Sage were calibrated with the Particle Swarm Optimization method using a subset of full-physics runs with the same mass resolution than the dark matter only ones.

Dark Sage: Next-generation semi-analytic galaxy evolution with multidimensional structure and minimal free parameters

Abstract After more than five years of development, we present a new version of Dark Sage, a semi-analytic model (SAM) of galaxy formation that breaks the mould for models of its kind. Included among the major changes is an overhauled treatment of stellar feedback that is derived from energy conservation, operates on local scales, affects gas gradually over time rather than instantaneously, and predicts a mass loading factor for every galaxy. Building on the model’s resolved angular momentum structure of galaxies, we now consider the heating of stellar discs, delivering predictions for disc structure both radially and vertically. We add a further dimension to stellar discs by tracking the distribution of stellar ages in each annulus. Each annulus–age bin has its own velocity dispersion and metallicity evolved in the model. This allows Dark Sage to make structural predictions for galaxies that previously only hydrodynamic simulations could. We present the model as run on the merger trees of the highest-resolution gravity-only simulation of the MillenniumTNG suite. Despite its additional complexity relative to other SAMs, Dark Sage only has three free parameters, the least of any SAM, which we calibrate exclusively against the cosmic star formation history and the $z = 0$ stellar and H i mass functions using a particle-swarm optimisation method. The Dark Sage codebase, written in C and python, is publicly available at https://github.com/arhstevens/DarkSage.

Dark-ages reionization and galaxy formation simulation – XXI. Constraining the evolution of the ionizing escape fraction

ABSTRACT The fraction of ionizing photons that escape their host galaxies to ionize hydrogen in the intergalactic medium (IGM) is a critical parameter in analyses of the reionization era. In this paper, we use the meraxes semi-analytic galaxy formation model to infer the mean ionizing photon escape fraction and its dependence on galaxy properties through joint modelling of the observed high redshift galaxy population and existing constraints on the reionization history. Using a Bayesian framework, and under the assumption that escape fraction is primarily related to halo mass, we find that the joint constraints of the ultraviolet luminosity function, cosmic microwave background optical depth, and the Ly α forest require an escape fraction of $(18\pm 5)$ per cent for galaxies within haloes of M ≲ 109 M⊙ and $(5\pm 2)$ per cent for more massive haloes. In terms of galaxy properties, this transition in escape fraction occurs at stellar masses of M⋆ ∼ 107 M⊙, nearly independent of redshift. As a function of redshift, reionization is dominated by the smaller M⋆ ≲ 107 M⊙ galaxies with high escape fractions at z ≳ 6 and by the larger M⋆ ≳ 107 M⊙ galaxies with lower escape fractions at z ≲ 6. Galaxies with star formation rates of 10−2.5 M⊙yr−1 to 10−1.5 M⊙yr−1 provide the dominant source of ionizing photons throughout reionization. Our results are consistent with recent direct measurements of a $\sim 5~{{\ \rm per\ cent}}$ escape fraction from massive galaxies at the end of reionization and support the picture of low mass galaxies being the dominant sources of ionizing photons during reionization.

Exploring the multiband gravitational wave background with a semi-analytic galaxy formation model

ABSTRACT An enormous number of compact binary systems, spanning from stellar to supermassive levels, emit substantial gravitational waves during their final evolutionary stages, thereby creating a stochastic gravitational wave background (SGWB). We calculate the merger rates of stellar compact binaries and massive black hole binaries using a semi-analytic galaxy formation model – Galaxy Assembly with Binary Evolution (GABE) – in a unified and self-consistent approach, followed by an estimation of the multiband SGWB contributed by those systems. We find that the amplitudes of the principal peaks of the SGWB energy density are within one order of magnitude ΩGW ∼ 10−9–10−8. This SGWB could easily be detected by the Square Kilometre Array (SKA), as well as by the planned interferometric detectors, such as the Einstein Telescope and the Laser Interferometer Space Antenna (LISA). The energy density of this background varies as ΩGW ∝ f2/3 in the SKA band. The shape of the SGWB spectrum in the frequency range ∼[10−4,1] Hz could allow the LISA to distinguish the black hole seed models. The amplitude of the SGWB from merging stellar binary black holes at ∼100 Hz is approximately 10 and 100 times greater than those from merging binary neutron stars and neutron-star–black-hole mergers, respectively. Note that, since the cosmic star formation rate density predicted by GABE is somewhat lower than the observational results by ∼0.2 dex at z < ∼2, the amplitude of the SGWB in the frequency range ∼[1, 104] Hz may be underestimated by a similar factor at most.

Compact groups from semi-analytical models of galaxy formation – V. Their assembly channels as a function of the environment

ABSTRACT We delved into the assembly pathways and environments of compact groups (CGs) of galaxies using mock catalogues generated from semi-analytical models (SAMs) on the Millennium simulation. We investigate the ability of SAMs to replicate the observed CG environments and whether CGs with different assembly histories tend to inhabit specific cosmic environments. We also analyse whether the environment or the assembly history is more important in tailoring CG properties. We find that about half of the CGs in SAMs are non-embedded systems, 40 per cent are inhabiting loose groups or nodes of filaments, while the rest distribute evenly in filaments and voids, in agreement with observations. We observe that early-assembled CGs preferentially inhabit large galaxy systems ($\sim 60~{{\ \rm per\ cent}}$), while around 30 per cent remain non-embedded. Conversely, lately formed CGs exhibit the opposite trend. We also obtain that lately formed CGs have lower velocity dispersions and larger crossing times than early-formed CGs, but mainly because they are preferentially non-embedded. Those lately formed CGs that inhabit large systems do not show the same features. Therefore, the environment plays a strong role in these properties for lately formed CGs. Early-formed CGs are more evolved, displaying larger velocity dispersions, shorter crossing times, and more dominant first-ranked galaxies, regardless of the environment. Finally, the difference in brightness between the two brightest members of CGs is dependent only on the assembly history and not on the environment. CGs residing in diverse environments have undergone varied assembly processes, making them suitable for studying their evolution and the interplay of nature and nurture on their traits.

The Intracluster Light and Its Link with the Dynamical State of the Host Group/Cluster: The Role of the Halo Concentration

We investigate the role of halo concentration in the formation of intracluster light (ICL) in galaxy groups and clusters, as predicted by a state-of-the-art semianalytic model of galaxy formation, coupled with a set of high-resolution dark-matter-only simulations. The analysis focuses on how the fraction of ICL correlates with halo mass, concentration, and fraction of early-type galaxies (ETGs) in a large sample of groups and clusters with . The fraction of ICL follows a normal distribution, a consequence of the stochastic nature of the physical processes responsible for the formation of the diffuse light. The fractional budget of ICL depends on both halo mass (very weakly) until group scales, and concentration (remarkably). More interestingly, the ICL fraction is higher in more concentrated objects, a result of the stronger tidal forces acting in the innermost regions of the halos where the concentration is the quantity playing the most relevant role. Our model predictions do not show any dependence between the ICL and ETGs fractions, and so we instead suggest the concentration rather than the mass, as recently claimed, to be the main driver of the ICL formation. The diffuse light starts to form in groups via stellar stripping and mergers and later assembled in more-massive objects. However, the formation and assembly keep going on group/cluster scales at lower redshift through the same processes, mainly via stellar stripping in the vicinity of the central regions where tidal forces are stronger.

The Galaxy Number Density Profile of Halos

More precise measurements of galaxy clustering will be provided by the next generation of galaxy surveys, such as DESI, WALLABY, and the Square Kilometre Array. To utilize this information to improve our understanding of the Universe, we need to accurately model the distribution of galaxies in their host dark matter halos. In this work, we present a new galaxy number density profile of halos, which makes predictions for the positions of galaxies in the host halo, different to the widely adopted Navarro–Frenk–White (NFW) profile, since galaxies tend to be found more in the outskirts of halos (nearer the virial radius) than an NFW profile. The parameterized galaxy number density profile model of halos is fit and tested using the Dark Sage semi-analytic model of galaxy formation. We find that our galaxy number density profile model of halos can accurately reproduce the halo occupation distribution and galaxy two-point correlation function of the Dark Sage simulation. We also derive the analytic expressions for the circular velocity and gravitational potential energy for this profile model. We use the SDSS Data Release 10 galaxy group catalog to validate this galaxy number density profile model of halos. Compared to the NFW profile, we find that our model more accurately predicts the positions of galaxies in their host halo and the galaxy two-point correlation function.

Dwarf galaxy archaeology from chemical abundances and star-formation histories

ABSTRACT We model the stellar abundances and ages of two disrupted dwarf galaxies in the Milky Way stellar halo: Gaia-Sausage Enceladus (GSE) and Wukong/LMS-1. Using a statistically robust likelihood function, we fit one-zone models of galactic chemical evolution with exponential infall histories to both systems, deriving e-folding time-scales of τin = 1.01 ± 0.13 Gyr for GSE and $\tau _\text{in} = 3.08^{+3.19}_{-1.16}$ Gyr for Wukong/LMS-1. GSE formed stars for $\tau _\text{tot} = 5.40^{+0.32}_{-0.31}$ Gyr, sustaining star formation for ∼1.5–2 Gyr after its first infall into the Milky Way ∼10 Gyr ago. Our fit suggests that star formation lasted for $\tau _\text{tot} = 3.36^{+0.55}_{-0.47}$ Gyr in Wukong/LMS-1, though our sample does not contain any age measurements. The differences in evolutionary parameters between the two are qualitatively consistent with trends with stellar mass M⋆ predicted by simulations and semi-analytic models of galaxy formation. Our inferred values of the outflow mass-loading factor reasonably match $\eta \propto M_\star ^{-1/3}$ as predicted by galactic wind models. Our fitting method is based only on Poisson sampling from an evolutionary track and requires no binning of the data. We demonstrate its accuracy by testing against mock data, showing that it accurately recovers the input model across a broad range of sample sizes (20 ≤ N ≤ 2000) and measurement uncertainties (0.01 ≤ σ[α/Fe], σ[Fe/H] ≤ 0.5; $0.02 \le \sigma _{\log _{10}(\text{age})} \le 1$). Due to the generic nature of our derivation, this likelihood function should be applicable to one-zone models of any parametrization and easily extensible to other astrophysical models which predict tracks in some observed space.

Compact groups from semi-analytical models of galaxy formation – IV: Effect of group assembly on the evolution of their galaxies

ABSTRACT Using over 3000 compact groups (CGs) of galaxies extracted from mock catalogues built from semi-analytical models (SAMs) of galaxy formation, we study whether the CG assembly channel affects the z = 0 properties of galaxies and their evolution. The evolution of CG galaxy properties with time is a clear function of their stellar masses. For instance, high-stellar-mass CG galaxies have lived their last 8 Gyr with little cold gas content while maintaining their reservoir of hot gas, while low-mass CG galaxies still preserve some of their cold gas content at the present but they have completely drained their hot gas reservoir. Beyond that, we find that the evolution of CG galaxies is also a function of the assembly history of the CGs: with more extreme losses of gas content, faster mass gain rates for black holes and more marked suppression of star formation as a function of cosmic time as we go from recent to early CG assembly. Thus, CGs constitute another laboratory for galaxy assembly bias, as the later assembling groups have later star formation. Our results show that classifying CGs according to their assembly channel is a way of distinguishing different paths by which galaxies transform their properties throughout their history.

The MillenniumTNG Project: semi-analytic galaxy formation models on the past lightcone

ABSTRACT Upcoming large galaxy surveys will subject the standard cosmological model, Lambda Cold Dark Matter, to new precision tests. These can be tightened considerably if theoretical models of galaxy formation are available that can predict galaxy clustering and galaxy–galaxy lensing on the full range of measurable scales, throughout volumes as large as those of the surveys, and with sufficient flexibility that uncertain aspects of the underlying astrophysics can be marginalized over. This, in particular, requires mock galaxy catalogues in large cosmological volumes that can be directly compared to observation, and can be optimized empirically by Monte Carlo Markov Chains or other similar schemes, thus eliminating or estimating parameters related to galaxy formation when constraining cosmology. Semi-analytic galaxy formation methods implemented on top of cosmological dark matter simulations offer a computationally efficient approach to construct physically based and flexibly parametrized galaxy formation models, and as such they are more potent than still faster, but purely empirical models. Here, we introduce an updated methodology for the semi-analytic L-Galaxies code, allowing it to be applied to simulations of the new MillenniumTNG project, producing galaxies directly on fully continuous past lightcones, potentially over the full sky, out to high redshift, and for all galaxies more massive than $\sim 10^8\, {\rm M}_\odot$. We investigate the numerical convergence of the resulting predictions, and study the projected galaxy clustering signals of different samples. The new methodology can be viewed as an important step towards more faithful forward-modelling of observational data, helping to reduce systematic distortions in the comparison of theory to observations.

Uchuu–ν2GC galaxies and AGN: cosmic variance forecasts of high-redshift AGN for JWST, Euclid, and LSST

ABSTRACT Measurements of the luminosity function of active galactic nuclei (AGN) at high redshift (z ≳ 6) are expected to suffer from field-to-field variance, including cosmic and Poisson variances. Future surveys, such as those from the Euclid telescope and JWST, will also be affected by field variance. We use the Uchuu simulation, a state-of-the-art cosmological N-body simulation with 2.1 trillion particles in a volume of 25.7 Gpc3, combined with a semi-analytic galaxy and AGN formation model, to generate the Uchuu–ν2GC catalogue, publicly available, that allows us to investigate the field-to-field variance of the luminosity function of AGN. With this Uchuu–ν2GC model, we quantify the cosmic variance as a function of survey area, AGN luminosity, and redshift. In general, cosmic variance decreases with increasing survey area and decreasing redshift. We find that at z ∼ 6 − 7, the cosmic variance depends weakly on AGN luminosity. This is because the typical mass of dark matter haloes in which AGN reside does not significantly depend on luminosity. Due to the rarity of AGN, Poisson variance dominates the total field-to-field variance, especially for bright AGN. We also examine the effect of parameters related to galaxy formation physics on the field variance. We discuss uncertainties present in the estimation of the faint-end of the AGN luminosity function from recent observations, and extend this to make predictions for the expected number of AGN and their variance for upcoming observations with Euclid, JWST, and the Legacy Survey of Space and Time (LSST).

Fisher matrix forecasts on the astrophysics of galaxies during the epoch of reionization from the 21-cm power spectra

ABSTRACT The hyperfine 21-cm transition of neutral hydrogen from the early Universe (z > 5) is a sensitive probe of the formation and evolution of the first luminous sources. Using the Fisher matrix formalism we explore the complex and degenerate high-dimensional parameter space associated with the high-z sources of this era and forecast quantitative constraints from a future 21-cm power spectrum (21-cm PS) detection. This is achieved using $\rm {\small ERAXES}$, a coupled semi-analytic galaxy formation model and reionization simulation, applied to an N-body halo merger tree with a statistically complete population of all atomically cooled galaxies out to z ∼ 20. Our mock observation assumes a 21-cm detection spanning z ∈ [5, 24] from a 1000 h mock observation with the forthcoming Square Kilometre Array, and is calibrated with respect to ultraviolet luminosity functions (UV LFs) at z ∈ [5, 10], the optical depth of CMB photons to Thompson scattering from Planck, and various constraints on the IGM neutral fraction at z > 5. In this work, we focus on the X-ray luminosity, ionizing UV photon escape fraction, star formation, and supernova feedback of the first galaxies. We demonstrate that it is possible to recover five of the eight parameters describing these properties with better than 50 per cent precision using just the 21-cm PS. By combining with UV LFs, we are able to improve our forecast, with five of the eight parameters constrained to better than 10 per cent (and all below 50 per cent).

Implications of z ≳ 12 JWST galaxies for galaxy formation at high redshift

ABSTRACT Using a semi-analytic galaxy formation model, we study analogues of eight z ≳ 12 galaxies recently discovered by James Webb Space Telescope (JWST). We select analogues from a cosmological simulation with a (311 cMpc)3 volume and an effective particle number of 1012 enabling the resolution of every atomic-cooling galaxy at z ≤ 20. We vary model parameters to reproduce the observed ultraviolet (UV) luminosity function at 5 < z < 13, aiming for a statistically representative high-redshift galaxy mock catalogue. Using the forward-modelled JWST photometry, we identify analogues from this catalogue and study their properties as well as possible evolutionary paths and local environment. We find faint JWST galaxies (MUV ≳ − 19.5) to remain consistent with the standard galaxy formation model and that our fiducial catalogue includes large samples of their analogues. The properties of these analogues broadly agree with conventional spectral energy distribution-fitting results, except for having systematically lower redshifts due to the evolving ultraviolet luminosity function, and for having higher specific star formation rates as a result of burstier histories in our model. On the other hand, only a handful of bright galaxy analogues can be identified for the observed z ∼ 12 galaxies. Moreover, in order to reproduce the z ≳ 16 JWST galaxy candidates, boosting star-forming efficiencies through reduced feedback regulation and increased gas depletion rate is necessary relative to models of lower redshift populations. This suggests star formation in the first galaxies could differ significantly from their lower redshift counterparts. We also find that these candidates are subject to low-redshift contamination, which is present in our fiducial results as both the dusty or quiescent galaxies at z ∼ 5.

Environmental effects on associations of dwarf galaxies

ABSTRACT We study the properties of associations of dwarf galaxies and their dependence on the environment. Associations of dwarf galaxies are extended systems composed exclusively of dwarf galaxies, considering as dwarf galaxies those galaxies less massive than $M_{\star , \rm max} = 10^{9.0}$${\rm M}_{\odot }\, h^{-1}$. We identify these particular systems using a semi-analytical model of galaxy formation coupled to a dark matter-only simulation in the Λ Cold Dark Matter cosmological model. To classify the environment, we estimate eigenvalues from the tidal field of the dark matter particle distribution of the simulation. We find that the majority, two thirds, of associations are located in filaments (∼67 per cent), followed by walls (∼26 per cent), while only a small fraction of them are in knots (∼6 per cent) and voids (∼1 per cent). Associations located in more dense environments present significantly higher velocity dispersion than those located in less dense environments, evidencing that the environment plays a fundamental role in their dynamical properties. However, this connection between velocity dispersion and the environment depends exclusively on whether the systems are gravitational bound or unbound, given that it disappears when we consider associations of dwarf galaxies that are gravitationally bound. Although less than a dozen observationally detected associations of dwarf galaxies are currently known, our results are predictions on the eve of forthcoming large surveys of galaxies, which will enable these very particular systems to be identified and studied.

Predictions of the 21 cm global signal in the JWST and ALMA era

ABSTRACT We calculate the redshift evolution of the global 21 cm signal in the first billion years using an advanced semi-analytical galaxy formation model delphi. Employing only two redshift- and mass-independent free parameters, our model predicts galaxy populations in accord with data from both the JWST and the Atacama Large Millimetre Array (ALMA) at z ∼ 5–12. In addition to this ‘fiducial’ model, which fully incorporates the impact of dust attenuation, we also explore an unphysical ‘maximal’ model wherein galaxies can convert a 100 per cent of their gas into stars instantaneously (and supernova feedback is ignored) required to explain JWST data at z > =13. We also explore a wide range of values for our 21 cm parameters that include the impact of X-ray heating (fX,h = 0.02–2.0) and the escape fraction of Lyman Alpha photons (fα = 0.01–1.0). Our key findings are (i) the fiducial model predicts a global 21 cm signal, which reaches a minimum brightness temperature of Tb, min ∼ −215 mK at a redshift zmin ∼ 14; (ii) since the impact of dust on galaxy properties only becomes relevant at z < = 8, dust does not have a sensible impact on the global 21 cm signal; (iii) the ‘maximal’ model predicts Tb, min = −210 mK as early as zmin ∼ 18; and (iv) galaxy formation and 21 cm parameters have a degenerate impact on the global 21 cm signal. A combination of the minimum temperature and its redshift will therefore be crucial in constraining galaxy formation parameters and their coupling to the 21 cm signal at these early epochs.

The MillenniumTNG Project: high-precision predictions for matter clustering and halo statistics

ABSTRACT Cosmological inference with large galaxy surveys requires theoretical models that combine precise predictions for large-scale structure with robust and flexible galaxy formation modelling throughout a sufficiently large cosmic volume. Here, we introduce the millenniumTNG (MTNG) project which combines the hydrodynamical galaxy formation model of illustrisTNG with the large volume of the millennium simulation. Our largest hydrodynamic simulation, covering $(500 \, h^{-1}{\rm Mpc})^3 \simeq (740\, {\rm Mpc})^3$, is complemented by a suite of dark-matter-only simulations with up to 43203 dark matter particles (a mass resolution of $1.32\times 10^8 \, h^{-1}{\rm M}_\odot$) using the fixed-and-paired technique to reduce large-scale cosmic variance. The hydro simulation adds 43203 gas cells, achieving a baryonic mass resolution of $2\times 10^7 \, h^{-1}{\rm M}_\odot$. High time-resolution merger trees and direct light-cone outputs facilitate the construction of a new generation of semi-analytic galaxy formation models that can be calibrated against both the hydro simulation and observation, and then applied to even larger volumes – MTNG includes a flagship simulation with 1.1 trillion dark matter particles and massive neutrinos in a volume of $(3000\, {\rm Mpc})^3$. In this introductory analysis we carry out convergence tests on basic measures of non-linear clustering such as the matter power spectrum, the halo mass function and halo clustering, and we compare simulation predictions to those from current cosmological emulators. We also use our simulations to study matter and halo statistics, such as halo bias and clustering at the baryonic acoustic oscillation scale. Finally we measure the impact of baryonic physics on the matter and halo distributions.

Non-Gaussian assembly bias from a semi-analytic galaxy formation model

ABSTRACT We produce z = 1 galaxy catalogues with the semi-analytic code galacticus to study the dependence on the assembly history of the host halos of the non-Gaussian bias parameter bϕ for galaxies selected by colour magnitude and emission line luminosities. Galaxies selected by g–r colour shows a large assembly bias consistent with previous analyses: a larger value of the normalization amplitude σ8 implies a faster mass assembly and therefore older and redder galaxies. For galaxies selected by H α luminosity, we do not detect a significant assembly bias for the redshift and the halo masses considered here. This indicates that the non-Gaussian assembly bias should be less of a concern for future emission line galaxy surveys. We investigate, for the first time, the sensitivity of the non-Gaussian assembly bias to a change in the parameters of the galaxy formation model: these induce variations up to order unity in the measured Δbϕ, but the overall trends with colour or luminosity remain the same. Since these results may be sensitive to the specific galaxy formation model, it will be prudent to extend this analysis to other semi-analytic models in addition to halo mass and redshift.

Exploring binary black hole mergers and host galaxies withsharkand COMPAS

ABSTRACTWe explore the connection between the gravitational wave (GW) merger rates of stellar-mass binary black holes (BBHs) and galaxy properties. We do this by generating populations of stars using the binary population synthesis code COMPAS and evolving them in galaxies from the semi-analytic galaxy formation model Shark, to determine the number of mergers occurring in each simulation time-step. We find that metal-rich and massive galaxies with star formation rate (SFR) greater than $1\, {\rm M}_{\odot }\, \rm yr^{-1}$ are 10 times more likely to have GW events compared to younger, less massive, and metal-poor galaxies. Our simulation with the default input parameters predicts a higher local merger rate density compared to the third GW transient catalogue (GWTC-3) prediction from LIGO, VIRGO, and KAGRA, due to short coalescence times, low metallicities, and a high SFR at low redshift in the simulation, which produces more BBHs that merge within the age of the Universe compared to observations. We identify alternate remnant mass models that more accurately reproduce the volumetric rate and provide updated fits to the merger rate as a function of redshift. We then investigate the relative fraction of GW events in our simulation that are in observable host galaxies from upcoming galaxy surveys, determining which of those are ideal for tracing host galaxies with high merger rates. The implications of this work can be utilized for constraining stellar evolution models, better informing follow-up programs, and placing informative priors on host galaxies when measuring cosmological parameters such as the Hubble constant.

Mock X-Ray Observations of Hot Gas with L-Galaxies Semi-analytic Models of Galaxy Formation

We create mock X-ray observations of hot gas in galaxy clusters with a new extension of the L-Galaxies semi-analytic model of galaxy formation, which includes the radial distribution of hot gas in each halo. Based on the model outputs, we first build some mock light cones, then generate mock spectra with the SOXS package and derive the mock images in the light cones. Using the mock data, we simulate mock X-ray spectra for the ROSAT all-sky survey, and compare the mock spectra with the observational results. Then, we consider the design parameters of the HUBS mission and simulate the observation of the halo hot gas for HUBS as an important application of our mock work. We find: (1) our mock data match the observations by current X-ray telescopes. (2) The survey of hot baryons in resolved clusters by HUBS is effective below redshift 0.5, and the observations of the emission lines in point-like sources at z > 0.5 by HUBS help us understand the hot baryons in the early universe. (3) By taking advantage of the large simulation box and flexibility in semi-analytic models, our mock X-ray observations provide the opportunity to select targets and observation strategies for forthcoming X-ray facilities.

Outflows in the gaseous disks of active galaxies and their impact on black hole scaling relations

To solve the still unsolved and fundamental problem of the role of active galactic nucleus (AGN) feedback in the shaping of galaxies, we implement eda new physical treatment of AGN-driven winds into our semi-analytic model of galaxy formation. With each galaxy in our model, we associated solutions for the outflow expansion and the mass outflow rates in different directions, depending on the AGN luminosity, on the circular velocity of the host halo and on the gas content of the considered galaxy. We also assigned an effective radius to each galaxy that we derived from energy conservation during merger events, and a stellar velocity dispersion that we self-consistently computed via Jeans modeling. We derived all the main scaling relations between the black hole (BH) mass and the stellar mass of the host galaxy and of the bulge, the velocity dispersion, the host halo dark matter mass, and the star formation efficiency. We find that our improved AGN feedback mostly controls the dispersion around the relations, but it plays a subdominant role in shaping slopes and/or normalizations of the scaling relations. The models agree better with the available data when possible limited-resolution selection biases are included. The model does not indicate that any more fundamental galactic property is linked to BH mass. The velocity dispersion plays a similar role as stellar mass, which disagrees with current data. In line with other independent studies carried out on comprehensive semi-analytic and hydrodynamic galaxy-BH evolution models, our current results signal either that the current cosmological models of galaxy formation are inadequate in their reproduction of the local scaling relations in terms of both shape and residuals, and/or they indicate that the local sample of dynamically measured BHs is only incompletely known.