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DESI 1% survey: Halo Occupation Distribution of Emission Line Galaxies
Speaker
Antoine Rocher CEA Paris-Saclay (Paris, France)
Abstract
I will present the first results of the dark matter (DM) halo-galaxy connection of the emission line galaxies (ELGs) from the Early Data Release (EDR) of the Dark Energy Spectroscopic Instrument (DESI) survey. Over 5 years, DESI will observe ∼ 40M galaxies and quasars over 0.1 < z < 3.5, including ∼ 17M ELGs in 0.6 < z < 1.6, to strongly constrain dark energy models. In only two months of early observations, DESI observed 267k ELGs which is the largest ELGs spectroscopic sample to date. Thanks to its completeness, this sample provides precise clustering measurements down to very small scales, 0.03 [Mpc/h]. We use Halo Occupation Distribution (HOD) models to reproduce the DESI ELG clustering. We perform a joint fit to the projected correlation function (wp) and the two-point correlation function monopole ξ0 and quadrupole ξ2 using a novel and promising HOD fitting method, based on Gaussian processes. DESI early data reveal a strong clustering at very small separation rp < 0.3 [Mpc/h] that is challenging for physically motivated HOD. To reproduce this signal, we show that we need to introduce close pairs of galaxies in low mass halos ($<10^{12} M_{\odot}$), which is totally unexpected from previous ELGs studies. We investigate conformity bias, i.e. prior information for the satellite probability function depending whether the DM halo already hosts a central galaxy to solve this issue and it improves the modeling of clustering data.
Date and Time
April 6 2023 4pm KST (= 7am UTC) Zoom link (active once the seminar starts)