Multi-tracer extension of the halo model: probing quenching and conformity in eBOSS

Shadab Alam, John A. Peacock, Katarina Kraljic, Ashley J. Ross, Johan Comparat

Research output: Contribution to journalArticlepeer-review


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 x 1013 h-1M ο, 1.1 x 1012 h-1Mο and 5x1012 h-1Mο 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 signifcance, while obtaining upper limits on 2-halo confor-mity. We also look at the environmental dependence of the galaxy quenching effciency and find that halo mass driven quenching successfully explains the behaviour in high density regions, but it fails to describe the quenching effciency in low density regions.
In particular, we show that the quenching effciency 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.
Original languageEnglish
Pages (from-to)581-595
Number of pages15
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
Early online date8 Jul 2020
Publication statusPublished - 1 Sep 2020


  • astro-ph.CO
  • astro-ph.GA


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