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We characterise the radial density, metallicity and flattening profile of the Milky Way's stellar halo, based on the large sample of 1757 spectroscopically confirmed giant stars from SDSS/SEGUE-2 after excising stars that were…

Astrophysics of Galaxies · Physics 2015-08-26 Xiang-Xiang Xue , Hans-Walter Rix , Zhibo Ma , Heather Morrison , Jo Bovy , Branimir Sesar , William Janesh

A relativistic analysis of the polarization properties of light elastically scattered by atomic hydrogen is performed, based on the Dirac equation and second order perturbation theory. The relativistic atomic states used for the…

The evolution of the virial overdensity $\Delta_{\rm vir}$ for $\Lambda$CDM and seven dynamical dark-energy models is investigated in the extended spherical collapse model (SCM). Here the virialization process is naturally achieved by…

Cosmology and Nongalactic Astrophysics · Physics 2019-10-10 Francesco Pace , Carlo Schimd , David F. Mota , Antonino Del Popolo

In the Gaia era, understanding the effects of the perturbations of the Galactic disc is of major importance in the context of dynamical modelling. In this theoretical paper we extend previous work in which, making use of the epicyclic…

Astrophysics of Galaxies · Physics 2022-02-02 H. Al Kazwini , Q. Agobert , A. Siebert , B. Famaey , G. Monari , S. Rozier , P. Ramos , R. Ibata , S. Gausland , C. Riviere , D. Spolyar

Considering galaxies as self - gravitating systems of many collisionless particles allows to use methods of statistical mechanics inferring the distribution function of these stellar systems. Actually, the long range nature of the…

Cosmology and Nongalactic Astrophysics · Physics 2014-02-04 V. F. Cardone , M. P. Leubner , A. Del Popolo

With SDSS galaxy data and halo data from up-to-date N-body simulations we construct a semi-empirical catalog (SEC) of early-type systems by making a self-consistent bivariate statistical match of stellar mass (M_star) and velocity…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-04 Kyu-Hyun Chae , Andrey V. Kravtsov , Joshua A. Frieman , Mariangela Bernardi

The halo model (HM) describes the inhomogeneous universe as a collection of halos. The full nonlinear power spectrum of the universe is well approximated by the HM, whose prediction can be easily computed without lengthy numerical…

Cosmology and Nongalactic Astrophysics · Physics 2011-09-07 Kimmo Kainulainen , Valerio Marra

We present useful functions for the profiles of dark-matter (DM) haloes with a free inner slope, from cusps to cores, where the profiles of density, mass-velocity and potential are simple analytic expressions. Analytic velocity is obtained…

Astrophysics of Galaxies · Physics 2017-04-12 Avishai Dekel , Guy Ishai , Aaron A. Dutton , Andrea V. Maccio

We develop a self-consistent and accurate halo model by partitioning matter according to the depletion radii of haloes. Unlike conventional models that define haloes with the virial radius while relying on a separate exclusion radius or…

Cosmology and Nongalactic Astrophysics · Physics 2023-09-20 Yifeng Zhou , Jiaxin Han

Sparse regression algorithms have been proposed as the appropriate framework to model the governing equations of a system from data, without needing prior knowledge of the underlying physics. In this work, we use sparse regression to build…

Astrophysics of Galaxies · Physics 2021-08-25 M. Icaza-Lizaola , Richard G. Bower , Peder Norberg , Shaun Cole , Matthieu Schaller , Stefan Egan

Using a new algorithm for estimating the actions of orbits a parametrised distribution function is automatically fitted to observational data for the solar neighbourhood. We adopt a gravitational potential that is generated by three discs…

Astrophysics of Galaxies · Physics 2015-06-05 James Binney

We present a new analytical solution to the steady-state distribution of stars close to a central supermassive black hole of mass $M_{\bullet}$ in the center of a galaxy. Assuming a continuous mass function of the form $dN/dm \propto…

Astrophysics of Galaxies · Physics 2022-11-30 Itai Linial , Re'em Sari

The virial theorem prescribes the ratio of the globally-averaged equatorial to vertical velocity dispersion of a tracer population in spherical and flattened dark haloes. This gives sequences of physical models in the plane of global…

Astrophysics of Galaxies · Physics 2015-06-03 A. Agnello , N. W. Evans

We describe a simple model which explains the qualitative and (approximate) quantitative features of the distribution of orbital velocities of merging pairs of dark matter halos. Our model considers a primary dark matter halo as a perturber…

Astrophysics of Galaxies · Physics 2021-05-26 A. J. Benson

The distribution of cold gas in dark matter haloes is driven by key processes in galaxy formation: gas cooling, galaxy mergers, star formation and reheating of gas by supernovae. We compare the predictions of four different galaxy formation…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-18 Han-Seek Kim , C. M. Baugh , A. J. Benson , S. Cole , C. S. Frenk , C. G. Lacey , C. Power , M. Schneider

We present new analytical distribution functions for anisotropic spherical galaxies. They have the density profiles of the gamma-models, which allow a wide range of central density slopes, and are widely used to fit elliptical galaxies and…

Astrophysics · Physics 2008-11-26 Pieter Buyle , Chris Hunter , Herwig Dejonghe

Analytic models based on spherical and ellipsoidal gravitational collapse have been used to derive the mass functions of dark matter halos and their progenitors (the conditional mass function). The ellipsoidal model generally provides a…

Astrophysics · Physics 2010-12-16 Jun Zhang , Chung-Pei Ma , Onsi Fakhouri

Dynamical properties of two-component galaxy models whose stellar density distribution is described by a gamma-model while the total density distribution has a pure r^(-2) profile, are presented. The orbital structure of the stellar…

Astrophysics · Physics 2009-11-13 Luca Ciotti , Lucia Morganti , Tim de Zeeuw

We analyse the impact of galaxy--halo misalignment on the ability of weak lensing studies to constrain the shape of dark matter haloes, using a combination of the Millennium dark matter N-body simulation and different semi-analytic galaxy…

Cosmology and Nongalactic Astrophysics · Physics 2016-07-07 Philip E. Bett

Upcoming Stage-IV surveys will deliver measurements of distribution of matter with unprecedented precision, demanding highly accurate theoretical models for cosmological parameter inference. A major source of modeling uncertainty lies in…

Cosmology and Nongalactic Astrophysics · Physics 2026-04-01 Pranjal R. S. , Shivam Pandey , Dhayaa Anbajagane , Elisabeth Krause , Klaus Dolag