MIGHTEE-HI: Evolution of HI Scaling Relations of Star-forming Galaxies at z < 0.5

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 equivalent to M-*/SFR), obtaining greater than or similar to 5 sigma 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 z(med) similar to 0.37 to z similar to 0. In particular, low-M-* galaxies (log(10)(M-*/M-circle dot) similar to 9) experience a strong H I depletion (similar to 0.5 dex in log(10)(M-H (I)/M-circle dot)), while massive galaxies (log(10)(M-*/M-circle dot) similar to 11) keep their H I mass nearly unchanged. When looking at the star formation activity, highly star-forming galaxies evolve significantly in M (H I) (f (H I), where f (H I) equivalent to M (H I)/M-*) at fixed SFR (sSFR), while at the lowest probed SFR (sSFR) the scaling relations show no evolution. These findings suggest a scenario in which low-M (*) galaxies have experienced a strong H I depletion during the last similar to 5 Gyr, while massive galaxies have undergone a significant H I replenishment through some accretion mechanism, possibly minor mergers. Interestingly, our results are in good agreement with the predictions of the simba simulation. We conclude that this work sets novel important observational constraints on galaxy scaling relations.

Automated summary

We present the first measurements of H I galaxy scaling relations from a blind survey at z > 0.15. Using spectral stacking of star-forming galaxies undetected in H I, we obtain greater than or similar to 5 sigma detections in most cases, revealing a moderate evolution in the scaling relations for low-M-* galaxies and no evolution for massive galaxies. The findings suggest a scenario in which low-M(*) galaxies have experienced H I depletion while massive galaxies have undergone H I replenishment, supporting the predictions of the simba simulation.