Volume 635, March 2020
|Number of page(s)||7|
|Section||Cosmology (including clusters of galaxies)|
|Published online||06 March 2020|
AGN jets versus accretion as reionization sources
Departament de Física Quàntica i Astrofísica, Institut de Ciències del Cosmos (ICC), Universitat de Barcelona (IEEC-UB), Martí i Franquès 1, 08028 Barcelona, Spain
2 ICREA, Pg. Lluís Companys 23, 08010 Barcelona, Spain
Accepted: 9 January 2020
Context. Cosmic reionization put an end to the dark ages that came after the recombination era. Observations seem to favor the scenario of massive-star photons generated in low-mass galaxies being responsible for the bulk of reionization and, whereas a possible contribution from AGN accretion disks has been widely considered, they are currently thought to have had a minor role in reionization.
Aims. We aim to study the possibility of AGN having contributed to reionization not only through their accretion disks, but also through ionizing photons coming from the AGN jets interacting with the intergalactic medium.
Methods. We adopt an empirically derived AGN luminosity function at z ≃ 6, use X-ray observations to correct it for the presence of obscured sources, and estimate the density of jetted AGN. We then use analytical calculations to derive the fraction of jet energy that goes into ionizing photons. Finally, we compute the contribution of AGN jets to the H II volume filling factor at redshifts z ≃ 15−5.
Results. We show that the contribution of the AGN jet lobes to the reionization of the Universe at z ∼ 6 might have been as high as ≳10% of that of star-forming galaxies, under the most favorable conditions of jetted and obscuration fraction.
Conclusions. The contribution of AGN to the reionization, while most likely not dominant, could have been higher than previously assumed, thanks to the radiation originated in the jet lobes.
Key words: dark ages, reionization, first stars / galaxies: active / galaxies: jets / radiation mechanisms: non-thermal / intergalactic medium
© ESO 2020
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.