ELUCID. VI. Cosmic Variance of the Galaxy Distribution in the Local Universe

Abstract

Halo merger trees are constructed from ELUCID, a constrained N -body simulation in the Sloan Digital Sky Survey (SDSS) volume. These merger trees are used to populate dark matter halos with galaxies according to an empirical model of galaxy formation. Mock catalogs in the SDSS sky coverage are constructed, which can be used to study the spatial distribution of galaxies in the low-z Universe. These mock catalogs are used to quantify the cosmic variance in the galaxy stellar mass function (GSMF) measured from the SDSS survey. The GSMF estimated from the SDSS magnitude-limited sample can be affected significantly by the presence of the under-dense region at z < 0.03, so that the low-mass end of the function can be underestimated significantly. Several existing methods designed to deal with the effects of the cosmic variance in the estimate of GSMF are tested, and none is found to be able to fully account for the cosmic variance. We propose a method based on the conditional stellar mass functions in dark matter halos, which can provide an unbiased estimate of the global GSMF. The application of the method to the SDSS data shows that the GSMF has a significant upturn at M * < 10 9.5 h −1 M , which has been missed in many earlier measurements of the local GSMF. Subject headings: dark matter -large-scale structure of the universe -galaxies: halos -methods: statistical

The Morphological Transformation and the Quenching of Galaxies

“…Criterion (3) guarantees that galaxies can be identified with reliable large-scale environments. Criterion (4) is to minimize the completeness problem for less massive galaxies (see Chen et al (2019) for more details). The reconstruction region is restricted to the redshift range of 0.01 < z < 0.12, where groups with lg M halo 12 are complete.…”

Finding proto-clusters to trace galaxy evolution: I. The finder and its performance

“…For the most massive galaxies, the increase of the stellar mass in the descendants is modest, about a factor of 1.5 to 2. We note that the results here are based on the the empirical model (Lu et al 2014(Lu et al , 2015 proto-cluster finder 11 Chen et al 2019). However, the evolution tracks of cluster galaxies discussed above are expected to be valid in the general paradigm of galaxy formation.…”

“…We populate dark matter halos in ELUCID with galaxies using the empirical model (Lu et al 2014(Lu et al , 2015Chen et al 2019). This model treats central and satellite galaxies separately.…”

“…The positions and velocities of individual galaxies are assigned according to those of halos (for central galaxies) and subhalos (for satellite galaxies). The details of the implementation of the empirical model to the simulation can be found in Chen et al (2019).…”

The specific star formation rate function at different mass scales and quenching: A comparison between cosmological models and SDSS

“…It is constrained (in terms of initial conditions) by the re-constructed initial density field of SDSS DR 7 (Wang et al 2014). ELUCID has been used to study galaxy quenching (Wang et al 2018), galaxy intrinsic alignment (Wei et al 2018) and cosmic variance (Chen et al 2019) while it was also combined with an abundance matching method to evaluate galaxy formation models (Yang et al 2018). In our work, we combine the merger trees taken from the ELUCID N-body simulations with the L-Galaxies Semi Analytic Model (SAM, Luo et al 2016).…”