اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديد3D Genus Topology of Luminous Red Galaxies
141
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
We measure the 3D genus topology of large scale structure using Luminous Red Galaxies (LRGs) in the Sloan Digital Sky Survey and find it consistent with the Gaussian random phase initial conditions expected from the simplest scenarios of inflation. This studies 3D topology on the largest scales ever obtained. The topology is sponge-like. We measure topology in two volume-limited samples: a dense shallow sample studied with smoothing length of 21h^{-1}Mpc, and a sparse deep sample studied with a smoothing length of 34h^{-1}Mpc. The amplitude of the genus curve is measured with 4% uncertainty. Small distortions in the genus curve expected from non-linear biasing and gravitational effects are well explained (to about 1-sigma accuracy) by N-body simulations using a subhalo-finding technique to locate LRGs. This suggests the formation of LRGs is a clean problem that can be modeled well without any free fitting parameters. This bodes well for using LRGs to measure the characteristic scales such as the baryon oscillation scale in future deep redshift surveys.
قيم البحث
اقرأ أيضاً
Luminous red galaxies (LRGs) are much rarer and more massive than L* galaxies. Coupled with their extreme colours, LRGs therefore provide a demanding testing ground for the physics of massive galaxy formation. We present the first self-consistent pre
dictions for the abundance and properties of LRGs in hierarchical structure formation models. We test two published models which use quite different mechanisms to suppress the formation of massive galaxies: the Bower et al. (2006) model, which invokes ``AGN-feedback to prevent gas from cooling in massive haloes, and the Baugh et al. (2005) model which relies upon a ``superwind to eject gas before it is turned into stars. Without adjusting any parameters, the Bower et al. model gives an excellent match to the observed luminosity function of LRGs in the SDSS (with a median redshift of z=0.24) and to their clustering; the Baugh et al. model is less successful in these respects. Both models fail to match the observed abundance of LRGs at z=0.5 to better than a factor of ~2. In the models, LRGs are typically bulge dominated systems with M* of ~2x10^11 h^{-1} M_sun and velocity dispersions of ~250 km s^{-1}. Around half of the stellar mass in the model LRGs is already formed by z~2.2 and is assembled into one main progenitor by z~1.5; on average, only 25% of the mass of the main progenitor is added after z~1. LRGs are predicted to be found in a wide range of halo masses, a conclusion which relies on properly taking into account the scatter in the formation histories of haloes. Remarkably, we find that the correlation function of LRGs is predicted to be a power law down to small pair separations, in excellent agreement with observational estimates. Neither the Bower et al. nor the Baugh et al. model is able to reproduce the observed radii of LRGs.
We study the role of major and minor mergers in the mass growth of luminous red galaxies. We present small-scale ($0.01<r<8,hMpc$) projected cross-correlation functions of $23043$ luminous early-type galaxies from the Sloan Digital Sky Survey (SDSS)
Luminous Red Galaxy (LRG) sample ($0.16<z<0.30$, $MMiapprox -22.75,mag$) with all their companions in the SDSS imaging sample, split into color and luminosity subsamples with $MMi<-18,mag$. We de-project the two-dimensional functions to obtain three-dimensional real-space LRG--galaxy cross-correlation functions for each companion subsample. We find that the cross-correlation functions are not purely power-law and that there is a clear ``one-halo to ``two-halo transition near $1,hMpc$. We convert these results into close pair statistics and estimate the LRG accretion rate from each companion galaxy subsample using timescales from dynamical friction arguments for each subsample of the companions. We find that the accretion onto LRGs is dominated by dry mergers of galaxies more luminous than $Lstar$. We integrate the luminosity accretion rate from mergers over all companion galaxy subsamples and find that LRGs are growing by $[1.7pm 0.1]$ percent per $Gyr$, on average, from merger activity at redshift $zsim 0.25$. This rate is almost certainly an over-estimate because we have assumed that all close pairs are merging as quickly as dynamical friction allows; nonetheless it is on the low side of the panoply of measurements in the literature, and lower than any rate predicted from theory.
We use a stacking method to study the radial light profiles of luminous red galaxies (LRGs) at redshift $sim 0.62$ and $sim 0.25$, out to a radial range of 200 kpc. We do not find noticeable evolution of the profiles at the two redshifts. The LRG pro
files appear to be well approximated by a single Sersic profile, although some excess light can be seen outside 60 kpc. We quantify the excess light by measuring the integrated flux and find that the excess is about 10% -- a non-dominant but still nonnegligible component.
We perform Halo Occupation Distribution (HOD) modeling to interpret small-scale and intermediate-scale clustering of 35,000 luminous early-type galaxies and their cross-correlation with a reference imaging sample of normal L* galaxies in the Sloan Di
gital Sky Survey. The modeling results show that most of these luminous red galaxies (LRGs) are central galaxies residing in massive halos of typical mass M ~ a few times 10^13 to 10^14 Msun/h, while a few percent of them have to be satellites within halos in order to produce the strong auto-correlations exhibited on smaller scales. The mean luminosity Lc of central LRGs increases with the host halo mass, with a rough scaling relation of Lc propto M^0.5. The halo mass required to host on average one satellite LRG above a luminosity threshold is found to be about 10 times higher than that required to host a central LRG above the same threshold. We find that in massive halos the distribution of L* galaxies roughly follows that of the dark matter and their mean occupation number scales with halo mass as M^1.5. The HOD modeling results also allows for an intuitive understanding of the scale-dependent luminosity dependence of the cross-correlation between LRGs and L_* galaxies. Constraints on the LRG HOD provide tests to models of formation and evolution of massive galaxies, and they are also useful for cosmological parameter investigations. In one of the appendices, we provide LRG HOD parameters with dependence on cosmology inferred from modeling the two-point auto-correlation functions of LRGs.
In the standard model of non-linear structure formation, a cosmic web of dark-matter dominated filaments connects dark matter halos. In this paper, we stack the weak lensing signal of an ensemble of filaments between groups and clusters of galaxies.
Specifically, we detect the weak lensing signal, using CFHTLenS galaxy ellipticities, from stacked filaments between SDSS-III/BOSS luminous red galaxies (LRGs). As a control, we compare the physical LRG pairs with projected LRG pairs that are more widely separated in redshift space. We detect the excess filament mass density in the projected pairs at the $5sigma$ level, finding a mass of $(1.6 pm 0.3) times 10^{13} M_{odot}$ for a stacked filament region 7.1 $h^{-1}$ Mpc long and 2.5 $h^{-1}$ Mpc wide. This filament signal is compared with a model based on the three-point galaxy-galaxy-convergence correlation function, as developed in Clampitt, Jain & Takada (2014), yielding reasonable agreement.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
