Using the most powerful explosion as probes of the high-redshift Universe – BEaPro

For goal (a):
- analysis of the photometric and spectroscopic observations of GRB host galaxies;
- determination of the host galaxy properties (stellar mass, star-formation rate, metallicity,...);
- comparison of the host galaxy properties with those of star-forming galaxies found in galaxy surveys;
- comparison of the host galaxy properties with those of the host galaxies of other extreme/peculiar explosions.

For goal (b):
- analysis of the spectroscopic observations of GRB afterglows and host galaxies;
- combination of the information (kinematic, metallicity, star formation...) obtained through the data analysis;
- modelling of the combined properties;
- modelling of the lyman-alpha emission line.

Thanks to this project we will be able to:
- determine how to use LGRBs to trace star formation;
- put indirect constraints LGRB progenitors;
- combine for the first time the properties of the absorbing gas (including metallicity), the continuum and the liman-alpha emission of a sub-luminous star-forming galaxy at redshift z~6;
- test the models of the lyman-alpha emission;
- characterise a population of faint star-forming galaxies, partially missed in galaxy surveys but probably forming the bulk of the high-redshift galaxy population;
- thanks to the combination of the properties of the absorbing gas in the ISM with those of the ionised gas, bring new and unique information on the link between the properties of the ISM and star formation activity up to very high redshift.

Our results will be of major interest for a much broader community than the GRB one, as they will have a significant impact on our knowledge on star formation at very high redshift and on the properties of faint star-forming galaxies up to the highest redshift, where they form the bulk of the galaxy population.
Furthermore, our findings will also impact the studies on the final stages of massive stars.

France will play a leading role in the near future in this field, thanks to its involvement in the space mission SVOM, a Chinese-French satellite to detect and study GRBs, that will be launched in 2021. Our project will boost the French scientific activity in this field and will enhance the scientific return of the SVOM mission.

We expect to publish at least 7 articles over the 4 years of the project and to present our results at the major international conferences and workshops on these topics.

6 invited talk at international conferences.
More than 10 contributed talk at international conferences.

Publications in refereed journals:

Lyman continuum leakage in faint star-forming galaxies at redshift z = 3 - 3.5 probed by gamma-ray bursts
Vielfaure, J. -B.; Vergani, S. D.; Japelj, J.; Fynbo, J. P. U.; Gronke, M.; et al. 2020, A&A, in press (arXiv:2006.09377).

Are long gamma-ray bursts biased tracers of star formation? Clues from the host galaxies of the Swift/BAT6 complete sample of bright LGRBs. III: Stellar masses, star formation rates and metallicities at z > 1
Palmerio, J.T.; Vergani, S.D.; Salvaterra, R.; Sanders, R.L.; Japelj, J.; et al. 2019, A&A, 623, 26.

Host galaxies of SNe Ic-BL with and without long gamma-ray bursts
Japelj, J.; Vergani, S. D.; Salvaterra, R.; Renzo, M.; Zapartas, E.; de Mink, S. E.; et al. 2018, A&A, 617, 105

The X-shooter GRB afterglow legacy sample (XS-GRB)
Selsing, J.; Malesani, D.; Goldoni, P.; Fynbo, J. P. U.; Kruhler, T.; et al. (incl. Vergani, S.D.) 2019, A&A, 623, 92.

Investigation of dust attenuation and star formation activity in galaxies hosting GRBs Corre, D.; Buat, V.; Basa, S.; Boissier, S.; Japelj, J.; Palmerio, J.; et al. (incl. Vergani, S.D.) 2018, A&A, 617, 141

Molecular gas rich GRB host galaxy at the peak of cosmic star formation with significant out- flowing gas
Arabsalmani, M.; Le Floc’h, E.; Dannerbauer, H.; Feruglio, C.; Daddi, E.; et al. (incl. Vergani, S.D.) 2018, MNRAS, 476, 2332

Solving the conundrum of intervening strong Mg II absorbers towards gamma-ray bursts and quasars
Christensen, L.; Vergani, S.D.; Schulze, S.; Annau, N.; Selsing, J.; et al. 2017, A&A, 608, 84

Thanks to their exceptional brightness gamma-ray burst (GRB) afterglows can be used as extra-galactic background sources capable of unveiling the properties of the universe at different redshifts. The class of long GRBs (LGRBs) is associated with the collapse of the most massive stars, making them a tool to investigate star formation in the early Universe.
The goals of this project are: (a) to study the properties of a complete sample of LGRB host galaxies; (b) to combine up to the highest redshifts the properties of the absorbing gas in the inter-stellar medium (ISM) of GRB host galaxies derived from the afterglow spectroscopy with those of the ionized gas derived from the host galaxy spectroscopy.
The results will 1. allow a robust use of LGRBs as SFR tracers in the Universe; 2. put indirect constraints on the GRB progenitor star models; 3. allow the characterization up to the highest redshift of a population of low-mass star forming galaxies forming the bulk of the high redshift galaxy population; 4. bring unique information on the link between the properties of the ISM and star formation activity up to very high redshift.
The project presented here gives the opportunity to the Scientific Coordinator to build her team and to develop a strong group in France for the use of GRBs as probes of the high-redshift Universe. Bringing to new and unique results, this project will boost the French scientific activity in this field and will enhance the scientific return of the SVOM mission.