ترغب بنشر مسار تعليمي؟ اضغط هنا

The Mass-Concentration-Redshift Relation of Cold Dark Matter Halos

176   0   0.0 ( 0 )
 نشر من قبل Aaron Ludlow Ph.D.
 تاريخ النشر 2013
  مجال البحث فيزياء
والبحث باللغة English
 تأليف Aaron D. Ludlow




اسأل ChatGPT حول البحث

We use the Millennium Simulation series to investigate the mass and redshift dependence of the concentration of equilibrium cold dark matter (CDM) halos. We extend earlier work on the relation between halo mass profiles and assembly histories to show how the latter may be used to predict concentrations for halos of all masses and at any redshift. Our results clarify the link between concentration and the ``collapse redshift of a halo as well as why concentration depends on mass and redshift solely through the dimensionless ``peak height mass parameter, $ u(M,z)=delta_{rm crit}(z)/sigma(M,z)$. We combine these results with analytic mass accretion histories to extrapolate the $c(M,z)$ relations to mass regimes difficult to reach through direct simulation. Our model predicts that, at given $z$, $c(M)$ should deviate systematically from a simple power law at high masses, where concentrations approach a constant value, and at low masses, where concentrations are substantially lower than expected from extrapolating published empirical fits. This correction may reduce the expected self-annihilation boost factor from substructure by about one order of magnitude. The model also reproduces the $c(M,z)$ dependence on cosmological parameters reported in earlier work, and thus provides a simple and robust account of the relation between cosmology and the mass-concentration-redshift relation of CDM halos.



قيم البحث

اقرأ أيضاً

The density field in the outskirts of dark matter halos is discontinuous due to a caustic formed by matter at its first apocenter after infall. In this paper, we present an algorithm to identify the splashback shell formed by these apocenters in indi vidual simulated halos using only a single snapshot of the density field. We implement this algorithm in the code SHELLFISH (SHELL Finding In Spheroidal Halos) and demonstrate that the code identifies splashback shells correctly and measures their properties with an accuracy of $<5%$ for halos with more than 50,000 particles and mass accretion rates of $Gamma_textrm{DK14}>0.5$. Using SHELLFISH, we present the first estimates for several basic properties of individual splashback shells, such as radius, $R_textrm{sp}$, mass, and overdensity, and provide fits to the distribution of these quantities as functions of $Gamma_textrm{DK14}$, $ u_textrm{200m}$, and $z.$ We confirm previous findings that $R_textrm{sp}$ decreases with increasing $Gamma_textrm{DK14}$, but we show that independent of accretion rate, it also decreases with increasing $ u_textrm{200m}$. We also study the 3D structures of these shells and find that they generally have non-ellipsoidal oval shapes. We find that splashback radii estimated by SHELLFISH are $20%-30%$ larger than those estimated in previous studies from stacked density profiles at high accretion rates. We demonstrate that the latter are biased low due to the contribution of high-mass subhalos to these profiles and show that using the median instead of mean density in each radial bin mitigates the effect of substructure on density profiles and removes the bias.
We analyze the total and baryonic acceleration profiles of a set of well-resolved galaxies identified in the EAGLE suite of hydrodynamic simulations. Our runs start from the same initial conditions but adopt different prescriptions for unresolved ste llar and AGN feedback, resulting in diverse populations of galaxies by the present day. Some of them reproduce observed galaxy scaling relations, while others do not. However, regardless of the feedback implementation, all of our galaxies follow closely a simple relationship between the total and baryonic acceleration profiles, consistent with recent observations of rotationally supported galaxies. The relation has small scatter: different feedback implementations -- which produce different galaxy populations -- mainly shift galaxies along the relation, rather than perpendicular to it. Furthermore, galaxies exhibit a characteristic acceleration, $g_{dagger}$, above which baryons dominate the mass budget, as observed. These observations, consistent with simple modified Newtonian dynamics, can be accommodated within the standard cold dark matter paradigm.
(Abriged) Assuming that the hydrostatic equilibrium holds between the intracluster medium and the gravitational potential, we constrain the NFW profiles in a sample of 44 X-ray luminous galaxy clusters observed with XMM-Newton in the redshift range 0 .1-0.3. We evaluate several systematic uncertainties that affect our reconstruction of the X-ray masses. We measure the concentration c200, the dark mass M200 and the gas mass fraction within R500 in all the objects of our sample, providing the largest dataset of mass parameters for galaxy clusters in this redshift range. We confirm that a tight correlation between c200 and M200 is present and in good agreement with the predictions from numerical simulations and previous observations. When we consider a subsample of relaxed clusters that host a Low-Entropy-Core (LEC), we measure a flatter c-M relation with a total scatter that is lower by 40 per cent. From the distribution of the estimates of c200 and M200, with associated statistical (15-25%) and systematic (5-15%) errors, we use the predicted values from semi-analytic prescriptions calibrated through N-body numerical runs and measure sigma_8*Omega_m^(0.60+-0.03)= 0.45+-0.01 (at 2 sigma level, statistical only) for the subsample of the clusters where the mass reconstruction has been obtained more robustly, and sigma_8*Omega_m^(0.56+-0.04) = 0.39+-0.02 for the subsample of the 11 more relaxed LEC objects. With the further constraint from the fgas distribution in our sample, we break the degeneracy in the sigma_8-Omega_m plane and obtain the best-fit values sigma_8~1.0+-0.2 (0.75+-0.18 when the subsample of the more relaxed objects is considered) and Omega_m = 0.26+-0.01.
Dark matter halos of sub-solar mass are the first bound objects to form in cold dark matter theories. In this article, I discuss the present understanding of microhalos, their role in structure formation, and the implications of their potential prese nce, in the interpretation of dark matter experiments.
We propose a new approach for measuring the mass profile and shape of groups and clusters of galaxies, which uses lensing magnification of distant background galaxies. The main advantage of lensing magnification is that, unlike lensing shear, it reli es on accurate photometric redshifts only and not galaxy shapes, thus enabling the study of the dark matter distribution with unresolved source galaxies. We present a feasibility study, using a real population of z > 2.5 Lyman Break Galaxies as source galaxies, and where, similar to galaxy-galaxy lensing, foreground lenses are stacked in order to increase the signal-to-noise. We find that there is an interesting new observational window for gravitational lensing as a probe of dark matter halos at high redshift, which does not require measurement of galaxy shapes.
التعليقات
جاري جلب التعليقات جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
mircosoft-partner

هل ترغب بارسال اشعارات عن اخر التحديثات في شمرا-اكاديميا