New insights and methods for the clustering of emission line galaxies.
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Date
2019
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Abstract
We study the dependence of emission line galaxies (ELG) clustering in halo properties besides mass, an effect known as assembly bias (AB). This AB signature is scale-dependent in some
ELG samples and may contribute with potential systematic effects on cosmology constraints. We
test different implementations of the halo occupation distribution (HOD) model to construct mock
galaxy catalogues that mimic ELG selected samples produced by a semi-analytical model (SAM).
These catalogues are useful to understand the future observational samples. We select galaxies
from two different SAMs, applied to the Millennium-WMAP7 and the MultiDark Plank 2 simulation. We use fixed number density galaxy samples selected according to stellar mass, star formation
rate (SFR), and emission line luminosity from Hα, [OIII]λ5007, and [OII]λλ3727 − 3729 emission, obtained from a photoionization code. We develop three different schemes to populate haloes
with galaxies with increasing complexity, considering the scatter of the satellites HOD as an additional parameter in the modellings. The quality of the HOD modelling is determined by comparing
the two-point correlation function (2PCF) of the HOD mocks and the SAM samples. The HOD
modelling that uses the HOD of centrals and satellites separately, and assume a negative binomial
distribution for the satellite HOD, produce the best clustering predictions. The scatter in the satellites HOD is a key consideration for HOD mock catalogues that mimic ELG selected samples in
future galaxy surveys. The origin of the scale-dependent AB seems to be related to an environment selection effect rather than a physical reason. We found that galaxies in underdense regions
and low gas metallicity, make the main contribution to the scale-dependent signature. We obtain
that the peak of the Baryon Acoustic Oscillation (BAO) for some ELG samples is in lower scales
than expected, and the β parameter is non-constant in large scales. Hence, this selection effect can
introduce systematic in the inferred cosmology from ELGs.
Description
Tesis (Magíster en Astrofísica)--Pontificia Universidad Católica de Chile, 2019