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Building a digital twin of a luminous red galaxy spectroscopic survey: galaxy properties and clustering covariance

Hernández-Aguayo, César and Prada, Francisco and Baugh, Carlton M and Klypin, Anatoly (2021) 'Building a digital twin of a luminous red galaxy spectroscopic survey: galaxy properties and clustering covariance.', Monthly notices of the Royal Astronomical Society, 503 (2). pp. 2318-2339.


Upcoming surveys will use a variety of galaxy selections to map the large-scale structure of the Universe. It is important to make accurate predictions for the properties and clustering of such galaxies, including the errors on these statistics. Here, we describe a novel technique which uses the semi-analytical model of galaxy formation GALFORM, embedded in the high-resolution N-body Planck-Millennium simulation, to populate a thousand halo catalogues generated using the Parallel-PM N-body GLAM code. Our hybrid scheme allows us to make clustering predictions on scales that cannot be modelled in the original N-body simulation. We focus on luminous red galaxies (LRGs) selected in the redshift range z = 0.6 − 1 from the GALFORM output using similar colour-magnitude cuts in the r, z, and W1 bands to those that will be applied in the Dark Energy Spectroscopic Instrument (DESI) survey, and call this illustrative sample ‘DESI-like’ LRGs. We find that the LRG-halo connection is non-trivial, leading to the prediction of a non-standard halo occupation distribution; in particular, the occupation of central galaxies does not reach unity for the most massive haloes, and drops with increasing mass. The GLAM catalogues reproduce the abundance and clustering of the LRGs predicted by GALFORM. We use the GLAM mocks to compute the covariance matrices for the two-point correlation function and power spectrum of the LRGs and their background dark matter density field, revealing important differences. We also make predictions for the linear-growth rate and the baryon acoustic oscillations distances at z = 0.6, 0.74, and 0.93. All ‘DESI-like’ LRG catalogues are made publicly available.

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Publisher statement:This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2021 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Date accepted:09 February 2021
Date deposited:14 July 2021
Date of first online publication:15 February 2021
Date first made open access:14 July 2021

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