scholarly journals High accuracy analytical solutions for the projected mass (counts) & surface density (brightness) of Einasto profiles

2021 ◽  
Author(s):  
Barun K Dhar
Keyword(s):  
Dark Matter ◽  
Gravitational Lensing ◽  
Surface Density ◽  
Surface Brightness ◽  
Analytical Approximation ◽  
High Accuracy ◽  
Density Profiles ◽  
Massive Galaxies ◽  
Multiple Components ◽  
Number Counts

Abstract The Einasto profile has been successful in describing the density profiles of dark matter haloes in ΛCDM N-body simulations. It has also been able to describe multiple components in the surface brightness profiles of galaxies. However, analytically projecting it to calculate quantities under projection is challenging. In this paper, we will see the development of a highly accurate analytical approximation for the mass (or counts) enclosed in an infinitely long cylindrical column for Einasto profiles—also known as the projected mass (or counts)—using a novel methodology. We will then develop a self-consistent high accuracy model for the surface density from the expression for the projected mass. Both models are quite accurate for a broad family of functions, with a shape parameter α varying by a factor of 100 in the range 0.05 ≲ α ≲ 5.0, with fractional errors ∼10−6 for α ≲ 0.4. Profiles with α ≲ 0.4 have been shown to fit the density profiles of dark matter haloes in N-body simulations as well as the luminosity profiles of the outer components of massive galaxies. Since the projected mass and the surface density are used in gravitational lensing, I will illustrate how these models facilitate (for the first time) analytical computation of several quantities of interest in lensing due to Einasto profiles. The models, however, are not limited to lensing and apply to similar quantities under projection, such as the projected luminosity, the projected (columnar) number counts and the projected density or the surface brightness.

scholarly journals THE STELLAR MASS STRUCTURE OF MASSIVE GALAXIES FROMz= 0 TOz= 2.5: SURFACE DENSITY PROFILES AND HALF-MASS RADII

2013 ◽  
Vol 763 (2) ◽  
pp. 73 ◽  
Author(s):  
Daniel Szomoru ◽  
Marijn Franx ◽  
Pieter G. van Dokkum ◽  
Michele Trenti ◽  
Garth D. Illingworth ◽  
...  
Keyword(s):  
Surface Density ◽  
Stellar Mass ◽  
Density Profiles ◽  
Massive Galaxies

Dark matter distribution in superthin galaxies

2020 ◽  
Vol 495 (4) ◽  
pp. 3722-3726
Author(s):  
Ilia Kalashnikov
Keyword(s):  
Dark Matter ◽  
Surface Density ◽  
Distribution Density ◽  
Spherically Symmetric ◽  
Matter Distribution ◽  
Galactic Disc ◽  
Density Profiles ◽  
Visible Matter ◽  
Simple Physical Model ◽  
Dark Matter Distribution

ABSTRACT This paper presents a new method of calculating dark matter density profiles for superthin axial symmetric galaxies without a bulge. This method is based on a simple physical model, which includes an infinitely thin galactic disc immersed in a spherically symmetric halo of dark matter. To obtain the desired distribution density, it suffices to know a distribution of visible matter surface density in a galaxy and a dependence of angular velocity on the radius. As a byproduct, the well-known expression, which reproduces surface density of a superthin galaxy expressed through a rotation law, was obtained.

scholarly journals Testing Gravity using Void Profiles

2014 ◽  
Vol 11 (S308) ◽  
pp. 555-560 ◽  
Author(s):  
Yan-Chuan Cai ◽  
Nelson Padilla ◽  
Baojiu Li
Keyword(s):  
Dark Matter ◽  
Gravitational Lensing ◽  
Modified Gravity ◽  
Large Scale ◽  
Line Of Sight ◽  
Number Density ◽  
Density Profiles ◽  
Photometric Redshift ◽  
Redshift Survey ◽  
Near Future

AbstractWe investigate void properties inf(R)models using N-body simulations, focusing on their differences from General Relativity (GR) and their detectability. In the Hu-Sawickif(R)modified gravity (MG) models, the halo number density profiles of voids are not distinguishable from GR. In contrast, the samef(R)voids are more empty of dark matter, and their profiles are steeper. This can in principle be observed by weak gravitational lensing of voids, for which the combination of a spectroscopic redshift and a lensing photometric redshift survey over the same sky is required. Neglecting the lensing shape noise, thef(R)model parameter amplitudesfR0=10-5and 10-4may be distinguished from GR using the lensing tangential shear signal around voids by 4 and 8 σ for a volume of 1 (Gpc/h)3. The line-of-sight projection of large-scale structure is the main systematics that limits the significance of this signal for the near future wide angle and deep lensing surveys. For this reason, it is challenging to distinguishfR0=10-6from GR. We expect that this can be overcome with larger volume. The halo void abundance being smaller and the steepening of dark matter void profiles inf(R)models are unique features that can be combined to break the degeneracy betweenfR0and σ8.

scholarly journals Massive low-surface-brightness galaxies in the eagle simulation

2020 ◽  
Vol 496 (3) ◽  
pp. 3996-4016
Author(s):  
Andrea Kulier ◽  
Gaspar Galaz ◽  
Nelson D Padilla ◽  
James W Trayford
Keyword(s):  
Dark Matter ◽  
Angular Momentum ◽  
Surface Density ◽  
Surface Brightness ◽  
Initial Conditions ◽  
High Surface ◽  
Formation Rate ◽  
Dark Matter Halo ◽  
Low Surface Brightness ◽  
Low Surface Brightness Galaxies

ABSTRACT We investigate the formation and properties of low surface brightness galaxies (LSBGs) with M* > 109.5 M⊙ in the eagle hydrodynamical cosmological simulation. Galaxy surface brightness depends on a combination of stellar mass surface density and mass-to-light ratio (M/L), such that low surface brightness is strongly correlated with both galaxy angular momentum (low surface density) and low specific star formation rate (high M/L). This drives most of the other observed correlations between surface brightness and galaxy properties, such as the fact that most LSBGs have low metallicity. We find that LSBGs are more isolated than high-surface-brightness galaxies (HSBGs), in agreement with observations, but that this trend is driven entirely by the fact that LSBGs are unlikely to be close-in satellites. The majority of LSBGs are consistent with a formation scenario in which the galaxies with the highest angular momentum are those that formed most of their stars recently from a gas reservoir co-rotating with a high-spin dark matter halo. However, the most extended LSBG discs in EAGLE, which are comparable in size to observed giant LSBGs, are built up via mergers. These galaxies are found to inhabit dark matter haloes with a higher spin in their inner regions (<0.1r200c), even when excluding the effects of baryonic physics by considering matching haloes from a dark-matter-only simulation with identical initial conditions.

scholarly journals Survey of gravitationally-lensed objects in HSC imaging (SuGOHI)

2019 ◽  
Vol 630 ◽  
pp. A71 ◽  
Author(s):  
Alessandro Sonnenfeld ◽  
Anton T. Jaelani ◽  
James Chan ◽  
Anupreeta More ◽  
Sherry H. Suyu ◽  
...  
Keyword(s):  
Dark Matter ◽  
Gravitational Lensing ◽  
Mass Function ◽  
Initial Mass Function ◽  
Dark Matter Halo ◽  
Open Problems ◽  
Massive Galaxies ◽  
Spatially Resolved ◽  
Stellar Masses ◽  
The Imf

Context. The determination of the stellar initial mass function (IMF) of massive galaxies is one of the open problems in cosmology. Strong gravitational lensing is one of the few methods that allow us to constrain the IMF outside of the Local Group. Aims. The goal of this study is to statistically constrain the distribution in the IMF mismatch parameter, defined as the ratio between the true stellar mass of a galaxy and that inferred assuming a reference IMF, of massive galaxies from the Baryon Oscillation Spectroscopic Survey (BOSS) constant mass (CMASS) sample. Methods. We took 23 strong lenses drawn from the CMASS sample, measured their Einstein radii and stellar masses using multi-band photometry from the Hyper Suprime-Cam survey, then fitted a model distribution for the IMF mismatch parameter and dark matter halo mass to the whole sample. We used a prior on halo mass from weak lensing measurements and accounted for strong lensing selection effects in our model. Results. Assuming a Navarro Frenk and White density profile for the dark matter distribution, we infer a value μIMF = −0.04 ± 0.11 for the average base-10 logarithm of the IMF mismatch parameter, defined with respect to a Chabrier IMF. A Salpeter IMF is in tension with our measurements. Conclusions. Our results are consistent with a scenario in which the region of massive galaxies where the IMF normalisation is significantly heavier than that of the Milky Way is much smaller than the scales 5 − 10 kpc probed by the Einstein radius of the lenses in our sample, as recent spatially-resolved studies of the IMF in massive galaxies suggest.

scholarly journals A universality of dark-halo surface density for the Milky Way and Andromeda dwarf satellites as a probe of the coldness of dark matter

2015 ◽  
Vol 11 (S317) ◽  
pp. 306-307
Author(s):  
Kohei Hayashi ◽  
Masashi Chiba
Keyword(s):  
Dark Matter ◽  
Surface Density ◽  
Milky Way ◽  
Mass Range ◽  
Dark Halo ◽  
Density Profiles ◽  
Dwarf Spheroidal Galaxies ◽  
Galaxy Sample ◽  
Low Mass ◽  
The Mean

AbstractWe propose a new astrophysical test on the nature of dark matter based on the properties of dark halos associated with dwarf spheroidal galaxies. The method adopts a mean surface density of a dark halo defined within a radius of maximum circular velocity, which is derivable for a wide variety of galaxies with any dark-matter density profiles. We find that even though dark halo density profiles are derived based on the different assumptions for each galaxy sample, this surface density is generally constant across a wide mass range of galaxy. We find that at higher halo-mass scales, this constancy for real galaxies can be naturally reproduced by both cold and warm dark matter (CDM and WDM) models. However, at low-mass scales, for which we have estimated from the Milky Way and Andromeda dwarf satellites, the mean surface density derived from WDM models largely deviates from the observed constancy, whereas CDM models are in reasonable agreement with observations.

REEXAMINING THE UNIVERSALITY OF THE BURKERT PROFILE ON CLUSTER SCALES: DARK MATTER CORES

2001 ◽  
Vol 10 (02) ◽  
pp. 239-244
Author(s):  
YAN-JIE XUE ◽  
XIANG-PING WU
Keyword(s):  
Dark Matter ◽  
Cross Section ◽  
Gravitational Lensing ◽  
Surface Brightness ◽  
Matter Density ◽  
Great Success ◽  
Analytic Approximation ◽  
Dark Halo ◽  
X Ray ◽  
Strong Gravitational Lensing

The Burkert profile is a competing candidate for the analytic approximation of virialized dark halos especially when dark matter particles have a finite cross-section for elastic collisions. In this paper we reexamine its universality in massive systems, using an ensemble of 45 nearby X-ray clusters and 20 distant X-ray/lensing clusters. Despite the fact that this empirical profile turns out a great success on galactic scales and also reproduces approximately the X-ray observed surface brightness profiles of clusters, the dark matter cores of clusters predicted by the Burkert profile are too large to be reconciled with the strong gravitational lensing measurements. Specifically, the typical dark halo cores of clusters represented by the Burkert profile are about 0.2 Mpc, and only a small fraction (~1/4) of clusters can have compact cores smaller than 0.1 Mpc. This will constitute a critical challenge to the Burkert profile as a universal dark matter density law over entire mass ranges.

scholarly journals On the origin of Sérsic profiles of galaxies and Einasto profiles of dark-matter halos

2016 ◽  
Vol 11 (S321) ◽  
pp. 87-89
Author(s):  
Carlo Nipoti
Keyword(s):  
Dark Matter ◽  
Analytic Function ◽  
Numerical Experiments ◽  
Density Fluctuation ◽  
Surface Brightness ◽  
Initial Density ◽  
Dark Matter Halos ◽  
Density Profiles ◽  
Fluctuation Field

AbstractThe surface-brightness profiles of galaxies I(R) and the density profiles of dark-matter halos ρ(r) are well represented by the same analytic function, named after either Sérsic, I∝e−(R/R*)1/m, or Einasto, ρ∝e−(r/r*)α, where R* and r* are characteristic radii. Systems with high Sérsic index m (or low Einasto index α) have steep central profiles and shallow outer profiles, while systems with low m (or high α) have shallow central profiles and steep profiles in the outskirts. We present the results of idealized numerical experiments which suggest that the origin of these profiles can be traced back to the initial density fluctuation field: high-α (low-m) systems form in smooth regions via few mergers, while low-α (high-m) systems form in clumpy regions via several mergers.

scholarly journals Self-gravitating dark matter gets in shape

2020 ◽  
Vol 29 (14) ◽  
pp. 2043017
Author(s):  
Jenny Wagner
Keyword(s):  
Dark Matter ◽  
Gravitational Lensing ◽  
Spatial Configuration ◽  
Mass Density ◽  
Gravitational Interaction ◽  
Mathematical Approach ◽  
Density Profiles ◽  
Physical Methods ◽  
The Universe ◽  
Galaxy Rotation Curves

In our current best cosmological model, the vast majority of matter in the universe is dark, consisting of yet undetected, nonbaryonic particles that do not interact electro-magnetically. So far, the only significant evidence for dark matter has been found in its gravitational interaction, as observed in galaxy rotation curves or gravitational lensing effects. The inferred dark matter agglomerations follow almost universal mass density profiles that can be reproduced well in simulations, but have eluded an explanation from a theoretical viewpoint. Forgoing standard (astro-)physical methods, I show that it is possible to derive these profiles from an intriguingly simple mathematical approach that directly determines the most likely spatial configuration of a self-gravitating ensemble of collisionless dark matter particles.

scholarly journals Cold dark matter: Controversies on small scales

2015 ◽  
Vol 112 (40) ◽  
pp. 12249-12255 ◽  
Author(s):  
David H. Weinberg ◽  
James S. Bullock ◽  
Fabio Governato ◽  
Rachel Kuzio de Naray ◽  
Annika H. G. Peter
Keyword(s):  
Dark Matter ◽  
Gravitational Lensing ◽  
Cold Dark Matter ◽  
Dwarf Galaxy ◽  
Analytical Models ◽  
Small Scale ◽  
Dark Sector ◽  
Massive Galaxies ◽  
Galaxy Dynamics ◽  
Wide Range

The cold dark matter (CDM) cosmological model has been remarkably successful in explaining cosmic structure over an enormous span of redshift, but it has faced persistent challenges from observations that probe the innermost regions of dark matter halos and the properties of the Milky Way’s dwarf galaxy satellites. We review the current observational and theoretical status of these “small-scale controversies.” Cosmological simulations that incorporate only gravity and collisionless CDM predict halos with abundant substructure and central densities that are too high to match constraints from galaxy dynamics. The solution could lie in baryonic physics: Recent numerical simulations and analytical models suggest that gravitational potential fluctuations tied to efficient supernova feedback can flatten the central cusps of halos in massive galaxies, and a combination of feedback and low star formation efficiency could explain why most of the dark matter subhalos orbiting the Milky Way do not host visible galaxies. However, it is not clear that this solution can work in the lowest mass galaxies, where discrepancies are observed. Alternatively, the small-scale conflicts could be evidence of more complex physics in the dark sector itself. For example, elastic scattering from strong dark matter self-interactions can alter predicted halo mass profiles, leading to good agreement with observations across a wide range of galaxy mass. Gravitational lensing and dynamical perturbations of tidal streams in the stellar halo provide evidence for an abundant population of low-mass subhalos in accord with CDM predictions. These observational approaches will get more powerful over the next few years.

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