Systematic errors on optical-SED stellar-mass estimates for galaxies across cosmic time and their impact on cosmology

¹ CENTRA, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais 1, 1049-001 Lisboa, Portugal
e-mail: apaulinoafonso@tecnico.ulisboa.pt
² Institute of Space Sciences (ICE, CSIC), Campus UAB, Carrer de Can Magrans, s/n, 08193 Barcelona, Spain
³ Institut d’Estudis Espacials de Catalunya (IEEC), 08034 Barcelona, Spain
⁴ DARK, Niels Bohr Institute, University of Copenhagen, Jagtvej 128, 2200 Copenhagen, Denmark
⁵ School of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ, UK
⁶ European Southern Observatory, Alonso de Córdova 3107, Casilla 19, Santiago, Chile
⁷ Department of Physics, University of Warwick, Coventry CV4 7AL, UK
⁸ Tuorla Observatory, Department of Physics and Astronomy, 20014 University of Turku, Finland
⁹ Finnish Centre for Astronomy with ESO (FINCA), 20014 University of Turku, Finland
¹⁰ GEPI, Observatoire de Paris, PSL University, CNRS, 5 Place Jules Janssen, 92190 Meudon, France

Received: 3 November 2021
Accepted: 25 January 2022

Abstract

Studying galaxies at different cosmic epochs entails several observational effects that need to be taken into account to compare populations across a large time-span in a consistent manner. We use a sample of 166 nearby galaxies that hosted type Ia supernovae (SNe Ia) and have been observed with the integral field spectrograph MUSE as part of the AMUSING survey. Here, we present a study of the systematic errors and bias on the host stellar mass with increasing redshift, which are generally overlooked in SNe Ia cosmological analyses. We simulate observations at different redshifts (0.1 <  z <  2.0) using four photometric bands (griz, similar to the Dark Energy Survey-SN program) to then estimate the host galaxy properties across cosmic time. We find that stellar masses are systematically underestimated as we move towards higher redshifts, due mostly to different rest-frame wavelength coverage, with differences reaching 0.3 dex at z ∼ 1. We used the newly derived corrections as a function of redshift to correct the stellar masses of a known sample of SN Ia hosts and derive cosmological parameters. We show that these corrections have a small impact on the derived cosmological parameters. The most affected is the value of the mass step Δ_M, which is reduced by ∼0.004 (6% lower). The dark energy equation of state parameter w changes by Δw∼ 0.006 (0.6% higher) and the value of Ω_m increases at most by 0.001 (∼0.3%), all within the derived uncertainties of the model. While the systematic error found in the estimate of the host stellar mass does not significantly affect the derived cosmological parameters, it is an important source of systematic error that needs to be corrected for as we enter a new era of precision cosmology.