MIGHTEE-H I: the first MeerKAT H I mass function from an untargeted interferometric survey

Abstract

We present the first measurement of the H I mass function (HIMF) using data from MeerKAT, based on 276 direct detections from the MeerKAT International GigaHertz Tiered Extragalactic Exploration (MIGHTEE) Survey Early Science data covering a period of approximately a billion years (0 ≤ z ≤ 0.084). This is the first HIMF measured using interferometric data over non-group or cluster field, i.e. a deep blank field. We constrain the parameters of the Schechter function that describes the HIMF with two different methods: 1/Vmax and modified maximum likelihood (MML). We find a low-mass slope α = −1.29+0.37−0.26, 'knee' mass log10(M∗/M⊙) = 10.07+0.24−0.24 and normalization log10(φ∗/Mpc−3) = −2.34+0.32−0.36 (H0 = 67.4 km s−1 Mpc−1) for 1/Vmax, and α = −1.44+0.13−0.10, 'knee' mass log10(M∗/M⊙) = 10.22+0.10−0.13 and normalization log10(φ∗/Mpc−3) = −2.52+0.1−0.14 for MML. When using 1/Vmax we find both the low-mass slope and 'knee' mass to be consistent within 1σ with previous studies based on single-dish surveys. The cosmological mass density of H I is found to be slightly larger than previously reported: ΩH I = 5.46+0.94−0.99 × 10−4 h−167.4 from 1/Vmax and ΩH I = 6.31+0.31−0.31 × 10−4 h−167.4 from MML but consistent within the uncertainties. We find no evidence for evolution of the HIMF over the last billion years