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The assembly bias of emission-line galaxies

Jiménez, Esteban; Padilla, Nelson; Contreras, Sergio; Zehavi, Idit; Baugh, Carlton M; Orsi, Álvaro

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Esteban Jiménez

Nelson Padilla

Sergio Contreras

Idit Zehavi

Álvaro Orsi


The next generation of spectroscopic surveys will target emission-line galaxies (ELGs) to produce constraints on cosmological parameters. We study the large-scale structure traced by ELGs using a combination of a semi-analytical model of galaxy formation, a code that computes the nebular emission from H II regions using the properties of the interstellar medium, and a large-volume, high-resolution N-body simulation. We consider fixed number density samples where galaxies are selected by their H α, [O III] λ5007, or [O II] λλ3727–3729 emission-line luminosities. We investigate the assembly bias signatures of these samples, and compare them to those of stellar mass- and star formation rate-selected samples. Interestingly, we find that the [O III]- and [O II]-selected samples display scale-dependent bias on large scales and that their assembly bias signatures are also scale dependent. Both these effects are more pronounced for lower number density samples. The [O III] and [O II] emitters that contribute most to the scale dependence tend to have a low gas-phase metallicity and are preferentially found in low-density regions. We also measure the baryon acoustic oscillation (BAO) feature and the β parameter related to the growth rate of overdensities. We find that the scale of the BAO peak is roughly the same for all selections and that β is scale dependent at large scales. Our results suggest that ELG samples include environmental effects that should be modelled in order to remove potential systematic errors that could affect the estimation of cosmological parameters.


Jiménez, E., Padilla, N., Contreras, S., Zehavi, I., Baugh, C. M., & Orsi, Á. (2021). The assembly bias of emission-line galaxies. Monthly Notices of the Royal Astronomical Society, 506(3), Article 3155-3168.

Journal Article Type Article
Acceptance Date Jun 16, 2021
Online Publication Date Jul 2, 2021
Publication Date 2021-09
Deposit Date Aug 19, 2021
Publicly Available Date Aug 20, 2021
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Royal Astronomical Society
Peer Reviewed Peer Reviewed
Volume 506
Issue 3
Article Number 3155-3168


Published Journal Article (2.2 Mb)

Copyright Statement
This article has been accepted for publication in Monthly notices of the Royal Astronomical Society. ©: 2020 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

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