scholarly journals The atomic gas in outer disks in semi-analytic models of galaxy formation

2016 ◽  
Vol 11 (S321) ◽  
pp. 131-131
Author(s):  
Jian Fu ◽  
Yu Luo
Keyword(s):  
Galaxy Formation ◽  
Surface Density ◽  
Mass Relation ◽  
Gas Stripping ◽  
Density Region ◽  
Radial Profiles ◽  
Gas Accretion ◽  
Analytic Models ◽  
Gas Component ◽  
Cold Gas

AbstractWe use semi-analytic models of galaxy formation L-Galaxies based on ΛCDM cosmology to study the HI gas component in galaxy outskirts. We adopt the radially-resolved version of the models by Fu et al. (2013), which includes both atomic and molecular gas component in interstellar medium. This model has been recently updated by Luo et al. (2016) to include cold gas stripping in the outer disk regions of the satellite galaxies by ram pressure. In our models, we can perfectly reproduce the HI size-mass relation, which is discovered by Broeils & Rhee (1997) and confirmed by many subsequent observations. In our model, the reason for such tight correlation between HI size and mass is atomic-molecular phase conversion in high gas surface density regions while HI ionization in low gas surface density region, which leads to very narrow distribution of HI mean surface density. The models also reproduce the universal exponential HI radial profiles in galaxy outskirts found by Bluedisk (Wang et al. 2013), which arises from cold gas accretion onto the galaxy disks in exponentially profiles.

scholarly journals HI Gas in Disk and Dwarf Galaxies in the Semi-analytic Models of Galaxy Formation

2015 ◽  
Vol 11 (S315) ◽  
Author(s):  
Jian Fu ◽  
Jing Wang ◽  
Yu Luo
Keyword(s):  
Galaxy Formation ◽  
Surface Density ◽  
Dwarf Galaxies ◽  
Mass Function ◽  
Molecular Gas ◽  
Mass Relation ◽  
Model Framework ◽  
Satellite Problem ◽  
Nearby Galaxies ◽  
Analytic Models

AbstractWe construct the radially-resolved semi-analytic models of galaxy formation based on the L-Galaxies model framework, which include both atomic and molecular gas phase in ISM. The models run on the halo outputs of ΛCDM cosmology N-body simulation. Our models can reproduce varies observations of HI gas in nearby galaxies, e.g. the HI mass function, the HI-to-star ratio vs stellar mass and stellar surface density, universal HI radial surface density profile in outer disks etc. We also give the physical origin of HI size-mass relation. Based on our model results for local dwarf galaxies, we show that the “missing satellite problem” also exists in the HI component, i.e., the models over-predict dwarf galaxies with low HI mass around the Milky Way. That is a shortcoming of current ΛCDM cosmology framework. Future survey for HI gas in local dwarf galaxies (e.g. MeerKAT, SKA & FAST) can help to verify the nature of dark matter (cold or warm).

Radial resolved galaxy disks models based on semi-analytic models of galaxy formation

2019 ◽  
Vol 15 (S341) ◽  
pp. 273-274
Author(s):  
Jian Fu
Keyword(s):  
Galaxy Formation ◽  
Scaling Relations ◽  
Chemical Enrichment ◽  
Galaxy Disk ◽  
Analytic Models ◽  
Cold Gas

AbstractWe show our work on the L-Galaxies semi-analytic models of galaxy formation, which includes the radial resolved distribution of star, gas, SFR and metallicity on each galaxy disk. The newest version of the codes include the H22-to-HI gas transition prescriptions and the chemical enrichment of various elements. Our revised model can give results on cold gas components, radial metallicity gradients and scaling relations, which can fit the recent observations.

scholarly journals Origin of the galaxy H i size–mass relation

2019 ◽  
Vol 490 (1) ◽  
pp. 96-113 ◽  
Author(s):  
Adam R H Stevens ◽  
Benedikt Diemer ◽  
Claudia del P Lagos ◽  
Dylan Nelson ◽  
Danail Obreschkow ◽  
...  
Keyword(s):  
Galaxy Formation ◽  
Surface Density ◽  
Mass Relation ◽  
Local Pressure ◽  
Density Profiles ◽  
Hydrodynamic Simulation ◽  
Variable Threshold ◽  
The Galaxy ◽  
Analytical Argument ◽  
A Minor

ABSTRACT We analytically derive the observed size–mass relation of galaxies’ atomic hydrogen (H i), including limits on its scatter, based on simple assumptions about the structure of H i discs. We trial three generic profiles for H i surface density as a function of radius. First, we assert that H i surface densities saturate at a variable threshold, and otherwise fall off exponentially with radius or, secondly, radius squared. Our third model assumes the total gas surface density is exponential, with the H i fraction at each radius depending on local pressure. These are tested against a compilation of 110 galaxies from the THINGS, LITTLE THINGS, LVHIS, and Bluedisk surveys, whose H i surface density profiles are well resolved. All models fit the observations well and predict consistent size–mass relations. Using an analytical argument, we explain why processes that cause gas disc truncation – such as ram-pressure stripping – scarcely affect the H i size–mass relation. This is tested with the IllustrisTNG(100) cosmological, hydrodynamic simulation and the Dark Sage semi-analytic model of galaxy formation, both of which capture radially resolved disc structure. For galaxies with $m_* \ge 10^9\, {\rm M}_{\odot }$ and $m_{\rm H\, {\small {I}}} \ge 10^8\, {\rm M}_{\odot }$, both simulations predict H i size–mass relations that align with observations, show no difference between central and satellite galaxies, and show only a minor, second-order dependence on host halo mass for satellites. Ultimately, the universally tight H i size–mass relation is mathematically inevitable and robust. Only by completely disrupting the structure of H i discs, e.g. through overly powerful feedback, could a simulation predict the relation poorly.

scholarly journals The influence of environment on satellite galaxies in the GAEA semi-analytic model

2020 ◽  
Vol 498 (3) ◽  
pp. 4327-4344 ◽  
Author(s):  
Lizhi Xie ◽  
Gabriella De Lucia ◽  
Michaela Hirschmann ◽  
Fabio Fontanot
Keyword(s):  
Galaxy Evolution ◽  
Galaxy Formation ◽  
Analytic Model ◽  
Gas Stripping ◽  
Hot Gas ◽  
Ram Pressure ◽  
Low Mass ◽  
Quenching Mechanisms ◽  
Satellite Galaxies ◽  
Cold Gas

ABSTRACT Reproducing the observed quenched fraction of satellite galaxies has been a long-standing issue for galaxy formation models. We modify the treatment of environmental effects in our state-of-the-art GAlaxy Evolution and Assembly (GAEA) semi-analytic model to improve our modelling of satellite galaxies. Specifically, we implement gradual stripping of hot gas, ram-pressure stripping of cold gas, and an updated algorithm to account for angular momentum exchanges between the gaseous and stellar disc components of model galaxies. Our updated model predicts quenched fractions that are in good agreement with local observational measurements for central and satellite galaxies, and their dependencies on stellar mass and halo mass. We also find consistency between model predictions and observational estimates of quenching times for satellite galaxies, H i, H2 fractions of central galaxies, and deficiencies of H i, H2, SFR of galaxies in cluster haloes. In the framework of our updated model, the dominant quenching mechanisms are hot gas stripping for low-mass satellite galaxies, and AGN feedback for massive satellite galaxies. The ram-pressure stripping of cold gas only affects the quenched fraction in massive haloes with Mh > 1013.5 M⊙, but is needed to reproduce the observed H i deficiencies.

HI gas component in dwarf and disk galaxies in the view of semi-analytic models

2018 ◽  
Vol 14 (S344) ◽  
pp. 274-275
Author(s):  
Jian Fu
Keyword(s):  
Galaxy Formation ◽  
Recent Progress ◽  
Milky Way ◽  
Mass Function ◽  
The Other ◽  
Disk Galaxies ◽  
Model Based ◽  
Low Mass ◽  
Analytic Models ◽  
Gas Component

AbstractWe show our recent progress on the L-Galaxies semi-analytic models of galaxy formation, which focuses on the HI gas in low mass galaxies. We find that the model based on ELUCID haloes can reproduce the HI mass function from ALFALFA 100 at low mass end. On the other hand, our models predict some gas rich low mass galaxies around the Milky Way, which may offer opportunities for future HI 21cm survey in nearby universe by FAST and SKA-1.

scholarly journals Simulating Metal Distributions in the ICM

2004 ◽  
Vol 217 ◽  
pp. 326-327
Author(s):  
C. M. Cress
Keyword(s):  
Star Formation ◽  
Structure Formation ◽  
Hierarchical Structure ◽  
Galaxy Formation ◽  
Metal Content ◽  
Metal Enrichment ◽  
Radial Profiles ◽  
Analytic Models

The metal enrichment of the intra-cluster medium within a hierarchical structure formation scenario is investigated using a combination of N-body + Hydro simulations and semi-analytic models of galaxy formation. In our simulation, rates and sites of star formation are identified and gas particles in the environment of these ‘galaxies’ are then enriched with metals using various prescriptions. We investigate the paths of enriched particles, demonstrating how gas enriched at higher redshifts is distributed in a cluster after it has formed. We are then able to predict a number of observable quantities such as the radial profiles of metals from both SNII and SNIa and the evolution of metal content with redshift.

scholarly journals Emerge: Empirical predictions of galaxy merger rates since z ∼ 6

2020 ◽  
Author(s):  
Joseph A O’Leary ◽  
Benjamin P Moster ◽  
Thorsten Naab ◽  
Rachel S Somerville
Keyword(s):  
Galaxy Formation ◽  
Power Law ◽  
Stellar Mass ◽  
Direct Result ◽  
Mass Relation ◽  
Massive Galaxies ◽  
The Galaxy ◽  
Major Merger ◽  
Low Mass ◽  
Merger Rate

Abstract We explore the galaxy-galaxy merger rate with the empirical model for galaxy formation, emerge. On average, we find that between 2 per cent and 20 per cent of massive galaxies (log10(m*/M⊙) ≥ 10.3) will experience a major merger per Gyr. Our model predicts galaxy merger rates that do not scale as a power-law with redshift when selected by descendant stellar mass, and exhibit a clear stellar mass and mass-ratio dependence. Specifically, major mergers are more frequent at high masses and at low redshift. We show mergers are significant for the stellar mass growth of galaxies log10(m*/M⊙) ≳ 11.0. For the most massive galaxies major mergers dominate the accreted mass fraction, contributing as much as 90 per cent of the total accreted stellar mass. We reinforce that these phenomena are a direct result of the stellar-to-halo mass relation, which results in massive galaxies having a higher likelihood of experiencing major mergers than low mass galaxies. Our model produces a galaxy pair fraction consistent with recent observations, exhibiting a form best described by a power-law exponential function. Translating these pair fractions into merger rates results in an inaccurate prediction compared to the model intrinsic values when using published observation timescales. We find the pair fraction can be well mapped to the intrinsic merger rate by adopting an observation timescale that decreases linearly with redshift as Tobs = −0.36(1 + z) + 2.39 [Gyr], assuming all observed pairs merge by z = 0.

scholarly journals Realistic mock observations of the sizes and stellar mass surface densities of massive galaxies in FIRE-2 zoom-in simulations

2020 ◽  
Vol 501 (2) ◽  
pp. 1591-1602
Author(s):  
T Parsotan ◽  
R K Cochrane ◽  
C C Hayward ◽  
D Anglés-Alcázar ◽  
R Feldmann ◽  
...  
Keyword(s):  
Galaxy Formation ◽  
Surface Density ◽  
Stellar Mass ◽  
Massive Galaxies ◽  
Star Forming ◽  
Stellar Feedback ◽  
Central Surface ◽  
Stellar Ages ◽  
The Galaxy ◽  
Zoom In

ABSTRACT The galaxy size–stellar mass and central surface density–stellar mass relationships are fundamental observational constraints on galaxy formation models. However, inferring the physical size of a galaxy from observed stellar emission is non-trivial due to various observational effects, such as the mass-to-light ratio variations that can be caused by non-uniform stellar ages, metallicities, and dust attenuation. Consequently, forward-modelling light-based sizes from simulations is desirable. In this work, we use the skirt  dust radiative transfer code to generate synthetic observations of massive galaxies ($M_{*}\sim 10^{11}\, \rm {M_{\odot }}$ at z = 2, hosted by haloes of mass $M_{\rm {halo}}\sim 10^{12.5}\, \rm {M_{\odot }}$) from high-resolution cosmological zoom-in simulations that form part of the Feedback In Realistic Environments project. The simulations used in this paper include explicit stellar feedback but no active galactic nucleus (AGN) feedback. From each mock observation, we infer the effective radius (Re), as well as the stellar mass surface density within this radius and within $1\, \rm {kpc}$ (Σe and Σ1, respectively). We first investigate how well the intrinsic half-mass radius and stellar mass surface density can be inferred from observables. The majority of predicted sizes and surface densities are within a factor of 2 of the intrinsic values. We then compare our predictions to the observed size–mass relationship and the Σ1−M⋆ and Σe−M⋆ relationships. At z ≳ 2, the simulated massive galaxies are in general agreement with observational scaling relations. At z ≲ 2, they evolve to become too compact but still star forming, in the stellar mass and redshift regime where many of them should be quenched. Our results suggest that some additional source of feedback, such as AGN-driven outflows, is necessary in order to decrease the central densities of the simulated massive galaxies to bring them into agreement with observations at z ≲ 2.

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