scholarly journals The origin of X-ray coronae around simulated disc galaxies

2021 ◽  
Vol 502 (2) ◽  
pp. 2934-2951
Author(s):  
Ashley J Kelly ◽  
Adrian Jenkins ◽  
Carlos S Frenk
Keyword(s):  
Galaxy Formation ◽  
Scaling Law ◽  
X Ray ◽  
Massive Galaxies ◽  
Star Forming ◽  
Hot Gas ◽  
Dark Matter Mass ◽  
Central Regions ◽  
Low Mass ◽  
Low X

ABSTRACT The existence of hot, accreted gaseous coronae around massive galaxies is a long-standing central prediction of galaxy formation models in the ΛCDM cosmology. While observations now confirm that extraplanar hot gas is present around late-type galaxies, the origin of the gas is uncertain with suggestions that galactic feedback could be the dominant source of energy powering the emission. We investigate the origin and X-ray properties of the hot gas that surrounds galaxies of halo mass, $(10^{11}\!-\!10^{14}) \, \mathrm{M}_\odot$, in the cosmological hydrodynamical eagle simulations. We find that the central X-ray emission, ≤0.10Rvir, of haloes of mass $\le 10^{13} \, \mathrm{M}_\odot$ originates from gas heated by supernovae (SNe). However, beyond this region, a quasi-hydrostatic, accreted atmosphere dominates the X-ray emission in haloes of mass $\ge 10^{12} \, \mathrm{M}_\odot$. We predict that a dependence on halo mass of the hot gas to dark matter mass fraction can significantly change the slope of the LX–Mvir relation (which is typically assumed to be 4/3 for clusters) and we derive the scaling law appropriate to this case. As the gas fraction in haloes increases with halo mass, we find a steeper slope for the LX–Mvir in lower mass haloes, $\le 10^{14} \, \mathrm{M}_\odot$. This varying gas fraction is driven by active galactic nuclei feedback. We also identify the physical origin of the so-called ‘missing feedback’ problem, the apparently low X-ray luminosities observed from high star-forming, low-mass galaxies. This is explained by the ejection of SNe-heated gas from the central regions of the halo.

scholarly journals SDSS IV MaNGA: Metallicity and ionisation parameter in local star-forming galaxies from Bayesian fitting to photoionisation models

2020 ◽  
Vol 636 ◽  
pp. A42 ◽  
Author(s):  
M. Mingozzi ◽  
F. Belfiore ◽  
G. Cresci ◽  
K. Bundy ◽  
M. Bershady ◽  
...  
Keyword(s):  
Galaxy Formation ◽  
Theoretical Work ◽  
Universal Relation ◽  
Star Forming ◽  
Spatially Resolved ◽  
Integral Field Spectroscopy ◽  
Radial Profiles ◽  
Central Regions ◽  
Optical Line ◽  
Low Mass

We measured gas-phase metallicity, ionisation parameter, and dust extinction for a representative sample of 1795 local star-forming galaxies using integral field spectroscopy from the SDSS-IV MaNGA survey. We self-consistently derive these quantities by comparing observed line fluxes with photoionisation models using a Bayesian framework. We also present the first comprehensive study of the [S III]λλ9069,9532 nebular lines, which have long been predicted to be ideal tracers of the ionisation parameter. However, we find that current photoionisation model predictions substantially over-predict the intensity of the [S III] lines, while broadly reproducing other observed optical line ratios. We discuss how to nonetheless make use of the information provided by the [S III] lines by setting a prior on the ionisation parameter. Following this approach, we derive spatially resolved maps and radial profiles of metallicity and ionisation parameter. The metallicity radial profiles derived are comparable with previous works, with metallicity declining toward the outer parts and showing a flattening in the central regions. This is in agreement with infall models of galaxy formation, which predict that spiral discs build up through accretion of material, leading to an inside-out growth. On the other hand, ionisation parameter radial profiles are flat for low-mass galaxies, while their slope becomes positive as galaxy mass increases. However, the ionisation parameter maps we obtain are clumpy, especially for low-mass galaxies. The ionisation parameter is tightly correlated with the equivalent width of Hα [EW(Hα)], following a nearly universal relation, which we attribute to the change of the spectral shape of ionising sources due to ageing of H II regions. We derive a positive correlation between ionisation parameter and metallicity at fixed EW(Hα), in disagreement with previous theoretical work that predict an anti-correlation.

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 Hot gaseous atmospheres of rotating galaxies observed with XMM–Newton

2020 ◽  
Vol 499 (4) ◽  
pp. 5163-5174
Author(s):  
A Juráňová ◽  
N Werner ◽  
P E J Nulsen ◽  
M Gaspari ◽  
K Lakhchaura ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Active Galactic Nuclei ◽  
Spiral Galaxy ◽  
Galactic Nuclei ◽  
X Ray ◽  
Hot Gas ◽  
Heating And Cooling ◽  
Theoretical Predictions ◽  
Central Regions ◽  
Gaseous Atmospheres

ABSTRACT X-ray emitting atmospheres of non-rotating early-type galaxies and their connection to central active galactic nuclei have been thoroughly studied over the years. However, in systems with significant angular momentum, processes of heating and cooling are likely to proceed differently. We present an analysis of the hot atmospheres of six lenticulars and a spiral galaxy to study the effects of angular momentum on the hot gas properties. We find an alignment between the hot gas and the stellar distribution, with the ellipticity of the X-ray emission generally lower than that of the optical stellar emission, consistent with theoretical predictions for rotationally supported hot atmospheres. The entropy profiles of NGC 4382 and the massive spiral galaxy NGC 1961 are significantly shallower than the entropy distribution in other galaxies, suggesting the presence of strong heating (via outflows or compressional) in the central regions of these systems. Finally, we investigate the thermal (in)stability of the hot atmospheres via criteria such as the TI- and C-ratio, and discuss the possibility that the discs of cold gas present in these objects have condensed out of the hot atmospheres.

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.

scholarly journals The Bimodality of Galaxy Populations Revisited Through Spectral Synthesis

2006 ◽  
Vol 2 (S235) ◽  
pp. 139-139
Author(s):  
L. Sodré ◽  
A. Mateus ◽  
R. Cid Fernandes ◽  
G. Stasińska ◽  
W. Schoenell ◽  
...  
Keyword(s):  
Galaxy Formation ◽  
Spectral Synthesis ◽  
Synthesis Method ◽  
Local Universe ◽  
Massive Galaxies ◽  
Star Forming ◽  
The Galaxy ◽  
Galaxy Populations ◽  
Galaxy Population ◽  
Stellar Masses

AbstractWe revisit the bimodality of the galaxy population seen in the local universe. We address this issue in terms of physical properties of galaxies, such as mean stellar ages and stellar masses, derived from the application of a spectral synthesis method to galaxy spectra from the SDSS. We show that the mean light-weighted stellar age of galaxies presents the best description of the bimodality seen in the galaxy population. The stellar mass has an additional role since most of the star-forming galaxies present in the local universe are low-mass galaxies. Our results give support to the existence of a ‘downsizing’ in galaxy formation, where nowadays massive galaxies tend to have stellar populations older than those found in less massive objects.

scholarly journals Galaxies and the intergalactic medium in groups

2000 ◽  
Vol 174 ◽  
pp. 187-196
Author(s):  
Trevor J. Ponman ◽  
Ed Lloyd-Davies ◽  
Stephen F. Helsdon
Keyword(s):  
Galaxy Formation ◽  
Intergalactic Medium ◽  
Preliminary Evidence ◽  
Early Type ◽  
Present Evidence ◽  
X Ray ◽  
Hot Gas ◽  
Isolated Galaxies ◽  
The Relationship

AbstractThe study of the relationship between the hot gas in groups and the galaxies they contain can help to constrain the evolution of both galaxies and groups. Here we present evidence that the intergalactic medium in groups has been strongly affected by preheating associated with galaxy formation which mostly preceded group collapse. The presence of this effect appears to be unrelated to the morphology of group galaxies, which supports models in which galaxy types are not primordial. We also present preliminary evidence that early-type galaxies in groups are not underluminous in the X-ray compared to isolated galaxies, suggesting that their dark halos may not have been substantially stripped.

scholarly journals New ASCA Observations of two Anomalous X-ray Pulsars

2000 ◽  
Vol 177 ◽  
pp. 695-698 ◽  
Author(s):  
B. Paul ◽  
M. Kawasaki ◽  
T. Dotani ◽  
F. Nagase
Keyword(s):  
Accretion Rate ◽  
Accretion Disc ◽  
Spectral Shape ◽  
Energy Spectra ◽  
Pulse Profile ◽  
X Ray ◽  
Low Mass ◽  
Low X ◽  
Star Surface ◽  
Made In

AbstractNewASCAobservations of two anomalous X-ray pulsars (AXP) 4U 0142+61 and 1E 1048.1-5937, made in 1998, when compared to earlier observations in 1994 show remarkable stability in the intensity, spectral shape and pulse profile. The energy spectra consist of two components, a power-law and a blackbody emission from the neutron star surface. In IE 1048.1-5937, we have identified three epochs with different spin-down rates and discuss its implications for the magnetar hypothesis of the AXPs. We also note that the spin-down rate and its variations in IE 1048.1-5937 are much larger than what normally can be produced by an accretion disc with very low mass accretion rate corresponding to its low X-ray luminosity.

scholarly journals The fates of merging supermassive black holes and a proposal for a new class of X-ray sources

2020 ◽  
Vol 498 (3) ◽  
pp. 3807-3816
Author(s):  
Charles Zivancev ◽  
Jeremiah Ostriker ◽  
Andreas H W Küpper
Keyword(s):  
Black Holes ◽  
Structure Formation ◽  
Hierarchical Structure ◽  
Dynamical Evolution ◽  
Supermassive Black Holes ◽  
Host Galaxy ◽  
X Ray ◽  
Massive Galaxies ◽  
New Class ◽  
Low Mass

ABSTRACT We perform N-body simulations on some of the most massive galaxies extracted from a cosmological simulation of hierarchical structure formation with total masses in the range 1012 M⊙ < Mtot < 3 × 1013 M⊙ from 4 ≥ z ≥ 0. After galactic mergers, we track the dynamical evolution of the infalling black holes (BHs) around their host’s central BHs (CBHs). From 11 different simulations, we find that, of the 86 infalling BHs with masses >104 M⊙, 36 merge with their host’s CBH, 13 are ejected from their host galaxy, and 37 are still orbiting at z = 0. Across all galaxies, 33 BHs are kicked to a higher orbit after close interactions with the CBH binary or multiple, after which only one of them merged with their hosts. These orbiting BHs should be detectable by their anomalous (not low-mass X-ray binary) spectra. The X-ray luminosities of the orbiting massive BHs at z = 0 are in the range $10^{28}-10^{43}\, \mathrm{erg}~\mathrm{s}^{-1}$, with a currently undetectable median value of $10^{33}\, \mathrm{erg}~\mathrm{s}^{-1}$. However, the most luminous ∼5 per cent should be detectable by existing X-ray facilities.

scholarly journals A multi-phase model for simulations of galaxy formation

2003 ◽  
Vol 208 ◽  
pp. 273-282 ◽  
Author(s):  
Volker Springel ◽  
Lars Hernquist
Keyword(s):  
Star Formation ◽  
Galaxy Formation ◽  
Phase Structure ◽  
Formation Rate ◽  
Disk Galaxies ◽  
Two Phase ◽  
Star Forming ◽  
Hot Gas ◽  
Feedback Model ◽  
Multi Phase

We discuss SPH simulations of galaxy formation which use a hybrid method to describe a two-phase structure of the star forming ISM on unresolved scales. Our modeling includes radiative cooling, heating due to a UV background, growth of cold clouds embedded in an ambient hot gas, star formation out of cloud material, feedback due to supernovae in the form of thermal heating and cloud evaporation, starbursts that can lead to galactic outflows, and metal enrichment. Our particular model for the treatment of the two-phase structure is based on a modified and extended version of the grid-based approach of Yepes et al. (1997). We discuss the properties of the feedback model and show how it stabilizes star forming disk galaxies and reduces the cosmic star formation rate to a level consistent with current observational constraints.

scholarly journals An X-Ray View of Interacting Binaries Outside The Galaxy

2004 ◽  
Vol 194 ◽  
pp. 3-6
Author(s):  
Andrea H. Prestwich
Keyword(s):  
Supernova Remnants ◽  
Luminosity Function ◽  
Local Group ◽  
Spiral Galaxies ◽  
High Mass ◽  
X Ray ◽  
Star Forming ◽  
Star Forming Regions ◽  
Low Mass ◽  
X Ray Binaries

AbstractChandra and XMM-Newton are revolutionizing our understanding of compact binaries in external galaxies, allowing us to study sources in detail in Local Group Galaxies and study populations in more distant systems. In M31 the X-ray luminosity function depends on the local stellar population in the sense that areas with active star formation have more high luminosity sources, and a higher overall source density (Kong. Di Stefano. Garcia, & Greiner 2003). This result is also true in galaxies outside the Local Group; starburst galaxies have flatter X-ray luminosity functions than do spiral galaxies which are in turn flatter than elliptical galaxies. These observational results suggest that the high end of the luminosity function in star forming regions is dominated by short-lived high mass X-ray binaries.In Chandra Cycle 2 we started a Large Project to survey a sample of 11 nearby (< 10Mpc) face-on spiral galaxies. We find that sources can be approximately classified on the basis of their X-ray color into low mass X-ray binaries, high mass X-ray binaries and supersoft sources. There is an especially interesting class of source that has X-ray colors softer (“redder”) than a typical low mass X-ray binary source, but not so extreme as supersoft sources. Most of these are probably X-ray bright supernova remnants, but some may be a new type of black hole accretor. Finally, when we construct a luminosity function of sources selecting only sources with low mass X-ray binary colors (removing soft sources) we find that there is a dip or break probably associated with the Eddington luminosity for a neutron star.

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