Populations Of Satellite Galaxies With The Illustristng Simulations
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Populations Of Satellite Galaxies With The Illustristng Simulations
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Author : Christoph Engler
language : en
Publisher:
Release Date : 2021*
Populations Of Satellite Galaxies With The Illustristng Simulations written by Christoph Engler and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2021* with categories.
The Impact Of Inhomogeneous Reionization On The Satellite Galaxy Population Of The Milky Way
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Author :
language : en
Publisher:
Release Date : 2009
The Impact Of Inhomogeneous Reionization On The Satellite Galaxy Population Of The Milky Way written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2009 with categories.
We use the publicly available subhalo catalogs from the via Lactea simulation along with a Gpc-scale N-body simulation to understand the impact of inhomogeneous reionization on the satellite galaxy population of the Milky Way. The large-volume simulation is combined with a model for reionization that allows us to predict the distribution of reionization times for Milky Way mass halos. Motivated by this distribution, we identify candidate satellite galaxies in the simulation by requiring that any subhalo must grow above a specified mass threshold before it is reionized; after this time the photoionizing background will suppress both the formation of stars and the accretion of gas. We show that varying the reionization time over the range expected for Milky Way mass halos can change the number of satellite galaxies by roughly two orders of magnitude. This conclusion is in contradiction with a number of studies in the literature, and we conclude that this is a result of inconsistent application of the results of Gnedin (2000); subtle changes in the assumptions about how reionization affects star formation in small galaxies can lead to large changes in the effect of changing the reionization time on the number of satellites. We compare our satellite galaxies to observations using both abundance matching and stellar population synthesis methods to assign luminosities to our subhalos and account for observational completeness effects. Additionally, if we assume that the mass threshold is set by the virial temperature T{sub vir} = 8 x 103 K we find that our model accurately matches the vmax distribution, radial distribution, and luminosity function of observed Milky Way satellites for a reionization time z{sub reion} = 9.6{sub -2.1}{sup 1.0}, assuming that the via Lactea subhalo distribution is representative of the Milky Way. This results in the presence of 11950{sup +202} satellite galaxies.
Searching For Satellite Galaxy Populations Of Low Mass Host Galaxies
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Author : Daniella M. Roberts
language : en
Publisher:
Release Date : 2022
Searching For Satellite Galaxy Populations Of Low Mass Host Galaxies written by Daniella M. Roberts and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2022 with Dark matter (Astronomy) categories.
Evolution Of Dwarf Galaxy Properties In Local Group Environments
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Author : Kenza Sigrid Arraki
language : en
Publisher:
Release Date : 2016
Evolution Of Dwarf Galaxy Properties In Local Group Environments written by Kenza Sigrid Arraki and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016 with Dwarf galaxies categories.
Understanding galaxy evolution depends on connecting large-scale structures determined by the [Lambda]CDM model with, at minimum, the small-scale physics of gas, star formation, and stellar feedback. Formation of galaxies within dark matter halos is sensitive to the physical phenomena occurring within and around the halo. This is especially true for dwarf galaxies, which have smaller potential wells and are more susceptible to the effects of tidal stripping and gas ionization and removal than larger galaxies. At dwarf galaxies scales comparisons of dark matter-only simulations with observations has unveiled various differences such as the core-cusp, the missing satellites, and the too big to fail problems. We have run suites of collisionless and hydrodynamical simulations of dwarf galaxies evolution in massive host environments to address these issues. We performed controlled, numerical simulations, which mimic the effects of baryons, in order to examine the assumptions implicitly made by dark matter-only simulations. The too big to fail problem is due to the overabundance of relatively massive, dense satellite galaxies found in simulations of Milky Way-like environments. We found that the removal of a small baryonic component from the central region of forming dwarf spheroidal galaxies and the inclusion of a disk component in the host galaxy can substantially reduce the central dark matter density of satellites, bringing simulations and observations of satellites into agreement. Additionally, we studied hydrodynamical simulations of massive host galaxies and their surrounding dwarf galaxy populations. The VELA simulation suite of cosmological zoom-in simulations is run with the ART code, stochastic star formation, and stellar feedback (supernovae feedback, stellar winds, radiation pressure, and photoionization pressure). The suite includes host galaxies with M[subscript vir](z = 0 ) = 1011 - 1012 M[sol] and their satellite dwarf galaxies and local isolated dwarf galaxies around each primary galaxy. We found that the inclusion of these relevant physical processes aligned the velocity functions and star formation histories of the dwarf galaxy populations closer to observations of the Local Group dwarf galaxies. By reproducing observations of dwarf galaxies we show how the inclusion of baryons in simulations relieves many of the discovered tensions between dark matter-only simulations and observations.
Models Of The Galaxy And The Massive Spectroscopic Stellar Survey Rave
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Author :
language : en
Publisher:
Release Date : 2014
Models Of The Galaxy And The Massive Spectroscopic Stellar Survey Rave written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014 with categories.
Numerical simulations of galaxy formation and observational Galactic Astronomy are two fields of research that study the same objects from different perspectives. Simulations try to understand galaxies like our Milky Way from an evolutionary point of view while observers try to disentangle the current structure and the building blocks of our Galaxy. Due to great advances in computational power as well as in massive stellar surveys we are now able to compare resolved stellar populations in simulations and in observations. In this thesis we use a number of approaches to relate the results of the two fields to each other. The major observational data set we refer to for this work comes from the Radial Velocity Experiment (RAVE), a massive spectroscopic stellar survey that observed almost half a million stars in the Galaxy. In a first study we use three different models of the Galaxy to generate synthetic stellar surveys that can be directly compared to the RAVE data. To do this we evaluate the RAVE selection function to great detail. Among the Galaxy models is the widely used Besancon model that performs well when individual parameter distribution are considered, but fails when we study chemodynamic correlations. The other two models are based on distributions of mass particles instead of analytical distribution functions. This is the first time that such models are converted to the space of observables and are compared to a stellar survey. We show that these models can be competitive and in some aspects superior to analytic models, because of their self-consistent dynamic history. In the case of a full cosmological simulation of disk galaxy formation we can recover features in the synthetic survey that relate to the known issues of the model and hence proof that our technique is sensitive to the global structure of the model. We argue that the next generation of cosmological galaxy formation simulations will deliver valuable models for our Galaxy. Testing these models with our approach will provide a direct connection between stellar Galactic astronomy and physical cosmology. In the second part of the thesis we use a sample of high-velocity halo stars from the RAVE data to estimate the Galactic escape speed and the virial mass of the Milky Way. In the course of this study cosmological simulations of galaxy formation also play a crucial role. Here we use them to calibrate and extensively test our analysis technique. We find the local Galactic escape speed to be 533 (+54/-41) km/s (90% confidence). With this result in combination with a simple mass model of the Galaxy we then construct an estimate of the virial mass of the Galaxy. For the mass profile of the dark matter halo we use two extreme models, a pure Navarro, Frenk & White (NFW) profile and an adiabatically contracted NFW profile. When we use statistics on the concentration parameter of these profile taken from large dissipationless cosmological simulations we obtain an estimate of the virial mass that is almost independent of the choice of the halo profile. For the mass M_340 enclosed within R_340 = 180 kpc we find 1.3 (+0.4/-0.3) x 10^12 M_sun. This value is in very good agreement with a number of other mass estimates in the literature that are based on independent data sets and analysis techniques. In the last part of this thesis we investigate a new possible channel to generate a population of Hypervelocity stars (HVSs) that is observed in the stellar halo. Commonly, it is assumed that the velocities of these stars originate from an interaction with the super-massive black hole in the Galactic center. It was suggested recently that stars stripped-off a disrupted satellite galaxy could reach similar velocities and leave the Galaxy. Here we study in detail the kinematics of tidal debris stars to investigate the probability that the observed sample of HVSs could partly originate from such a galaxy collision. We use a suite of $N$-body simulations following the encounter of a satellite galaxy with its Milky Way-type host galaxy. We quantify the typical pattern in angular and phase space formed by the debris stars and develop a simple model that predicts the kinematics of stripped-off stars. We show that the distribution of orbital energies in the tidal debris has a typical form that can be described quite accurately by a simple function. The main parameters determining the maximum energy kick a tidal debris star can get is the initial mass of the satellite and only to a lower extent its orbit. Main contributors to an unbound stellar population created in this way are massive satellites (M_sat > 10^9 M_sun). The probability that the observed HVS population is significantly contaminated by tidal debris stars appears small in the light of our results
Orbital Decay Of Satellite Galaxies
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Author : Tjeerd R. Bontekoe
language : en
Publisher:
Release Date : 1988
Orbital Decay Of Satellite Galaxies written by Tjeerd R. Bontekoe and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1988 with Galaxies categories.
The Hierarchical Build Up Of Massive Galaxies And The Intracluster Light Since Z
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Author :
language : en
Publisher:
Release Date : 2007
The Hierarchical Build Up Of Massive Galaxies And The Intracluster Light Since Z written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2007 with categories.
We use a set of simulation-based models for the dissipationless evolution of galaxies since z = 1 to constrain the fate of accreted satellites embedded in dark matter subhalos. These models assign stellar mass to dark matter halos at z = 1 by relating the observed galaxy stellar mass function (GSMF) to the halo+subhalo mass function monotonically. The evolution of the stellar mass content is then followed using halo merger trees extracted from N-body simulations. Our models are differentiated only in the fate assigned to satellite galaxies once subhalos, within which satellites are embedded, disrupt. These models are confronted with the observed evolution in the massive end of the GSMF, the z ≈ 0 brightest cluster galaxy (BCG)-cluster mass relation, and the combined BCG and intracluster light (ICL) luminosity distribution--all observables expected to evolve approximately dissipationlessly since z = 1. The combined observational constraints favor a model in which the vast majority (≈> 80%) of satellite stars from disrupted subhalos go into the ICL (operationally defined here as light below a surface brightness cut of [mu]{sub i} ≈ 23mag arcsec−2). Conversely, models that leave behind a significant population of satellite galaxies once the subhalo has disrupted are strongly disfavored, as are models that put a significant fraction of satellite stars into the BCG. Our results show that observations of the ICL provide useful and unique constraints on models of galaxy merging and the dissipationless evolution of galaxies in groups and clusters.
The Local Group And Its Dwarf Galaxy Members In The Standard Model Of Cosmology
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Author : Azadeh Fattahi
language : en
Publisher:
Release Date : 2017
The Local Group And Its Dwarf Galaxy Members In The Standard Model Of Cosmology written by Azadeh Fattahi and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017 with categories.
According to the current cosmological paradigm, ``Lambda Cold Dark Matter'' (LambdaCDM), only ~20% of the gravitating matter in the universe is made up of ordinary (i.e. baryonic) matter, while the rest consists of invisible dark matter (DM) particles, which existence can be inferred from their gravitational influence on baryonic matter and light. Despite the large success of the LambdaCDM model in explaining the large scale structure of the Universe and the conditions of the early Universe, there has been debate on whether this model can fully explain the observations of low mass (dwarf) galaxies. The Local Group (LG), which hosts most of the known dwarf galaxies, is a unique laboratory to test the predictions of the LambdaCDM model on small scales. I analyze the kinematics of LG members, including the Milky~Way-Andromeda (MW-M31) pair and dwarf galaxies, in order to constrain the mass of the LG. I construct samples of LG analogs from large cosmological N-body simulations, according to the following kinematics constraints: (a) the separation and relative velocity of the MW-M31 pair; (b) the receding velocity of dwarf galaxies in the outskirts of the LG. I find that these constraints yield a median total mass of 2*10^#x12; solar masses for the MW and M31, but with a large uncertainty. Based on the mass and the kinematics constraints, I select twelve LG candidates for the APOSTLE simulations project. The APOSTLE project consists of high-resolution cosmological hydrodynamical simulations of the LG candidates, using the EAGLE galaxy formation model. I show that dwarf satellites of MW and M31 analogs in APOSTLE are in good agreement with observations, in terms of number, luminosity and kinematics. There have been tensions between the observed masses of LG dwarf spheroidals and the predictions of N-body simulations within the LambdaCDM framework; simulations tend to over-predict the mass of dwarfs. This problem is known as the ``too-big-to-fail'' problem. I find that the enclosed mass within the half-light radii of Galactic classical dwarf spheroidals, is in excellent agreement with the simulated satellites in APOSTLE, and that there is no too-big-to-fail problem in APOSTLE simulations. A few factors contribute in solving the problem: (a) the mass of haloes in hydrodynamical simulations are lower compared to their N-body counterparts; (b) stellar mass-halo mass relation in APOSTLE is different than the ones used to argue for the too-big-to-fail problem; (c) number of massive satellites correlates with the virial mass of the host, i.e. MW analogs with virial masses above ~ 3*10^#x12; solar masses would have faced too-big-to-fail problems; (d) uncertainties in observations were underestimated in previous works. Stellar mass-halo mass relation in APOSTLE predicts that all isolated dwarf galaxies should live in haloes with maximum circular velocity (V_max) above 20 km/s. Satellite galaxies, however, can inhabit lower mass haloes due to tidal stripping which removes mass from the inner regions of satellites as they orbit their hosts. I examine all satellites of the MW and M31, and find that many of them live in haloes less massive than V_max=20 km/s. I additionally show that the low mass population is following a different trend in stellar mass-size relation compared to the rest of the satellites or field dwarfs. I use stellar mass-halo mass relation of APOSTLE field galaxies, along with tidal stripping trajectories derived in Penarrubia et al., in order to predict the properties of the progenitors of the LG satellites. According to this prediction, some satellites have lost a significant amount of dark matter as well as stellar mass. Cra~II, And~XIX, XXI, and XXV have lost 99 per-cent of their stellar mass in the past. I show that the mass discrepancy-acceleration relation of dwarf galaxies in the LG is at odds with MOdified Newtonian Dynamics (MOND) predictions, whereas tidal stripping can explain the observations very well. I compare observed velocity dispersion of LG satellites with the predicted values by MOND. The observations and MOND predictions are inconsistent, in particular in the regime of ultra faint dwarf galaxies.
Galactic Satellite Galaxies
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Author : Quan Guo
language : en
Publisher:
Release Date : 2013
Galactic Satellite Galaxies written by Quan Guo and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with categories.
In this thesis, we investigate the luminosity functions (LFs) and projected number density profiles of galactic satellites around isolated primaries of differing luminosity. To this end, we develop a new method to select isolated galactic satellite systems using the Sloan Digital Sky Survey (SDSS) spectroscopic and photometric galaxy samples. For specific luminosity primaries, we are able to stack as many as ~ 50,000 galaxy systems to obtain robust statisitcal results. Based on these samples, we derive accurate satellite luminosity functions extending almost 8 magnitudes fainter than their primaries and accurate projected number densities profiles of satellites down to 4 magnitudes fainter than their primaries. Then, we determine how the satellite luminosity functions and projected number density profiles vary with both the properties of their satellites and their primaries. In addition, we find that the normalized profiles can be well fitted by the NFW profiles in most cases. The dependence of the NFW concentration parameters on the luminosity of the satellites and their primaries are explored. Inspired by the similar independent study, we also explore the dependence of estimates of satellite luminosity functions on two different background subtraction methods. We then measure these quantities for model satellites placed into the Millennium and Millennium II dark matter simulations by the GALFORM semi-analytic galaxy formation model for different bins of primary galaxy magnitude. We compare our model predictions to the data that we previously measured. The generally successful comparison of the GALFORM model with the SDSS data performed here provides a non-trivial validation of the assumptions and framework of this kind of modelling.
High Performance Computing In Science And Engineering 18
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Author : Wolfgang E. Nagel
language : en
Publisher: Springer
Release Date : 2019-06-07
High Performance Computing In Science And Engineering 18 written by Wolfgang E. Nagel and has been published by Springer this book supported file pdf, txt, epub, kindle and other format this book has been release on 2019-06-07 with Computers categories.
This book presents the state-of-the-art in supercomputer simulation. It includes the latest findings from leading researchers using systems from the High Performance Computing Center Stuttgart (HLRS) in 2018. The reports cover all fields of computational science and engineering ranging from CFD to computational physics and from chemistry to computer science with a special emphasis on industrially relevant applications. Presenting findings of one of Europe’s leading systems, this volume covers a wide variety of applications that deliver a high level of sustained performance. The book covers the main methods in high-performance computing. Its outstanding results in achieving the best performance for production codes are of particular interest for both scientists and engineers. The book comes with a wealth of color illustrations and tables of results.