Mightee-hi: Evolution of hi scaling relations of star-forming galaxies at z < 0.5*

Abstract

We present the first measurements of H I galaxy scaling relations from a blind survey at z > 0.15. We perform spectral stacking of 9023 spectra of star-forming galaxies undetected in H I at 0.23 < z < 0.49, extracted from MIGHTEE-H I Early Science data cubes, acquired with the MeerKAT radio telescope. We stack galaxies in bins of galaxy properties (stellar mass M*, star formation rateSFR, and specific star formation rate sSFR, with sSFR ≡ M*/SFR), obtaining 5σ detections in most cases, the strongest H I-stacking detections to date in this redshift range. With these detections, we are able to measure scaling relations in the probed redshift interval, finding evidence for a moderate evolution from the median redshift of our sample zmed ∼ 0.37 to z ∼ 0. In particular, low-M* galaxies (  ~ * log 9 10( ) M M ) experience a strong H I depletion (∼0.5 dex in log10( ) M M H I  ), while massive galaxies (  ~ * log 11 10( ) M M ) keep their H I mass nearly unchanged. When looking at the star formation activity, highly star-forming galaxies evolve significantly in MH I ( fH I, where fH I ≡ MH I/M*) at fixed SFR (sSFR), while at the lowest probed SFR (sSFR) the scaling relations show no evolution.