Probing the peak of the star formation rate density with the extragalactic background light

TL;DR

This study constrains the star formation rate density across cosmic time by analyzing the extragalactic background light, revealing potential tensions with traditional star formation measurements at certain redshifts.

Contribution

It introduces a novel method to constrain the star formation rate density using EBL observations and models its impact across different parameters and assumptions.

Findings

SFRD constrained to <~ 0.1 M_solar yr^-1 Mpc^-3 at z~1

SFRD constrained to < 0.2 M_solar yr^-1 Mpc^-3 at z~2

Tensions identified between EBL-based constraints and star formation tracers at z~1

Abstract

The extragalactic background light (EBL), i.e., the diffuse meta-galactic photon field in the ultraviolet to infrared, is dominated by the emission from stars in galaxies. It is, therefore, intimately connected with the integrated star formation rate density (SFRD). In this paper, the SFRD is constrained using recent limits on the EBL density derived from observations of distant sources of high and very-high energy gamma-rays. The stellar EBL contribution is modeled utilizing simple stellar population spectra including dust attenuation and emission. For modeling the SFRD up to z=4 a broken power law function in z+1 is assumed. A wide range of values for the different model parameters (SFRD(z), metallicity, dust absorption) is investigated and their impact on the resulting EBL is studied. The calculated EBL densities are compared with the specific EBL density limits and constraints on the SFRD are derived. For the fiducial model, adopting a Chabrier initial mass function (IMF) and a second power law index for the SFRD of beta=0.3, the SFRD is constrained to <~ 0.1 M_solar yr^-1 Mpc^-3 and < 0.2 M_solar yr^-1 Mpc^-3 for a redshift of z~1 and z~2, respectively. The limits for a redshift of z~1 are in tension with SFRD measurements derived from instantaneous star formation tracers. While the tension for the conservative fiducial model in this study is not yet overly strong, the tension increases when applying plausible changes to the model parameters, e.g., using a Salpeter instead of a Chabrier IMF or a adopting a sub-solar metallicity.