Affiliation: University of Geneva

Contribution: Oral

Title: 1,000 Hα emitters at z~4-6: a new tracer of galaxy build-up in the first ~1.5 Gyr

Abstract: The pace at which galaxies form stars is known to vary throughout cosmic history. Even at short timescales, early galaxies experience variations in their star formation rates, leading to sequences of bursts followed by more quiescent phases. The Hα emission line is among the most reliable methods to probe star formation on short timescales. However, Hα was not accessible spectroscopically at z>~3 before JWST, as it is redshifted beyond the K-band, leading previous studies to derive it from broad-band photometry or use different estimators. Here, we use JWST observations to study the Hα emission line as a tracer of galactic star formation and its evolution throughout cosmic history. We present spectroscopic measurements of ~500 Hα-emitting galaxies at 4.9<z<6.7 with the FRESCO survey, which observed the GOODS fields with NIRCam/grism spectroscopy. We obtain the first Hα luminosity function at z~5 and z~6 based purely on spectroscopic data. We derive the star formation rate density and burstiness of these galaxies. By combining these results with previous studies at different redshifts, we present the cosmic evolution of star-forming galaxies. Our work shows the power of JWST to obtain complete emission-line-selected galaxy samples to provide unprecedented constraints on galaxy formation models.

This contribution can be found here (pdf).