New synthesis models of consistent extragalactic background light over cosmic time
Abstract
We present new synthesis models of the extragalactic background light (EBL) from far infra-red (FIR) to TeV γ-rays, with an emphasis on the extreme ultraviolet (UV) background that is responsible for the observed ionization and thermal state of the intergalactic medium across the cosmic time. Our models use updated values of the star formation rate density and dust attenuation in galaxies, QSO emissivity, and the distribution of H {I} gas in the intergalactic medium. Two of the most uncertain parameters in these models, the escape fraction of H {I} ionizing photons from galaxies and the spectral energy distribution (SED) of QSOs, are determined to be consistent with the latest measurements of H {I} and He {II} photoionization rates, the He {II} Lyman-α effective optical depths, various constraints on H {I} and He {II} reionization history, and many measurements of the local EBL from soft X-rays till γ-rays. We calculate the EBL from FIR to TeV γ-rays by using FIR emissivities from our previous work and constructing an average SED of high-energy emitting QSOs, i.e, type-2 QSOs and blazars. For public use, we also provide the EBL models obtained using different QSO SEDs at extreme-UV energies over a wide range of redshifts. These can be used to quantify uncertainties in the parameters derived from photoionization models and numerical simulations originating from the allowed variations in the UV background radiation.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- April 2019
- DOI:
- 10.1093/mnras/stz174
- arXiv:
- arXiv:1801.09693
- Bibcode:
- 2019MNRAS.484.4174K
- Keywords:
-
- galaxies: evolution;
- intergalactic medium;
- quasars: general;
- diffuse radiation;
- Astrophysics - Astrophysics of Galaxies;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- 29 pages, 15 figures, accepted for publication in MNRAS, all EBL tables are available online and included in the latest versions of cloudy software