Multitracer extension of the halo model: probing quenching and conformity in eBOSS

Abstract

<jats:title>Abstract</jats:title> <jats:p>We develop a new Multi-Tracer Halo Occupation Distribution (MTHOD) framework for the galaxy distribution and apply it to the extended Baryon Oscillation Spectroscopic Survey (eBOSS) final data between z = 0.7 − 1.1. We obtain a best fit MTHOD for each tracer and describe the host halo properties of these galaxies. The mean halo masses for LRGs, ELGs and QSOs are found to be 1.9 × 1013 h−1M⊙, 1.1 × 1012 h−1M⊙ and 5 × 1012 h−1M⊙ respectively in the eBOSS data. We use the MTHOD framework to create mock galaxy catalogues and predict auto- and cross-correlation functions for all the tracers. Comparing these results with data, we investigate galactic conformity, the phenomenon whereby the properties of neighbouring galaxies are mutually correlated in a manner that is not captured by the basic halo model. We detect 1-halo conformity at more than 3σ statistical significance, while obtaining upper limits on 2-halo conformity. We also look at the environmental dependence of the galaxy quenching efficiency and find that halo mass driven quenching successfully explains the behaviour in high density regions, but it fails to describe the quenching efficiency in low density regions. In particular, we show that the quenching efficiency in low density filaments is higher in the observed data, as compared to the prediction of the MTHOD with halo mass driven quenching. The mock galaxy catalogue constructed in this paper is publicly available on this website†.</jats:p>

The completed SDSS-IV extended Baryon Oscillation Spectroscopic Survey: N-body mock challenge for the eBOSS emission line galaxy sample

“…Such behaviour is not possible to accommodate in the SHOD model. Therefore, Alam et al (2019) proposed a modified HOD framework encapsulating such behaviour called High Mass Quenched model (HMQ).…”

“…The effect of various parameters on the HMQ occupation function is illustrated in Figure 1 of Alam et al (2019).The parameter M c is the cut-off mass of ELG centrals impacting the location of the peak in occupation probability. Q sets the quenching efficiency for high mass haloes; a larger value of Q implies more efficient quenching.…”

“…We create a series of mocks, from a total of 40 different models, with variations in the parameters discussed in § 6 and beyond (Alam et al 2019;Avila et al 2020). As we discussed in § 6, ELG host dark matter haloes properties are still under investigation.…”

“…Therefore, we adapt halo occupation distribution (HOD) models (Benson et al 2000;Seljak 2000;Peacock & Smith 2000;White et al 2001;Berlind & Weinberg 2002;Cooray & Sheth 2002) for ELG using N-body simulations to produce mock galaxy catalogues occupying large volumes (e.g. Alam et al 2019). We first test the RSD models through a series of non-blind mocks with a variety of baryonic physics added to the mock catalogues.…”

Galaxy: Dark matter connection in cosmology

“…These galaxies allow a high‐reliability spectroscopic redshift estimation helping on the measure of the total matter density field and the Redshift Space Distortions study. However, due to the quenching of star formation by UV background, ELG population decreases for halo masses greater than 10 12 M ⊙ (Alam et al 2020). This behavior implies a nonlinear relation between the ELG and the underlying dark matter densities.…”