We present the H i emission project within the MIGHTEE survey, currently being carried out with the newly commissioned MeerKAT radio telescope. This is one of the first deep, blind, medium-wide interferometric surveys for neutral hydrogen (H i) ever undertaken, extending our knowledge of H i emission to z = 0.6. The science goals of this medium-deep, medium-wide survey are extensive, including the evolution of the neutral gas content of galaxies over the past 5 billion years. Simulations predict nearly 3000 galaxies over 0 < z < 0.4 will be detected directly in H i, with statistical detections extending to z = 0.6. The survey allows us to explore H i as a function of galaxy environment, with massive groups and galaxy clusters within the survey volume. Additionally, the area is large enough to contain as many as 50 local galaxies with H i mass < 10 8 M ⊙ , which allows us to study the low-mass galaxy population. The 20 deg 2 main survey area is centred on fields with exceptional multi-wavelength ancillary data, with photometry ranging from optical through far-infrared wavelengths, supplemented with multiple spectroscopic campaigns. We describe here the survey design and the key science goals. We also show first results from the Early Science observations, including kinematic modelling of individual sources, along with the redshift, H i, and stellar mass ranges of the sample to date.
We present details of the Automated Radio Telescope Imaging Pipeline (ARTIP) and the results of a sensitive blind search for H i and OH absorbers at z < 0.4 and z < 0.7, respectively. ARTIP is written in Python 3.6, extensively uses the Common Astronomy Software Application tools and tasks, and is designed to enable the geographically distributed MeerKAT Absorption Line Survey (MALS) team to collaboratively process large volumes of radio interferometric data. We apply it to the first MALS data set obtained using the 64-dish MeerKAT radio telescope and 32 K channel mode of the correlator. With merely 40 minutes on target, we present the most sensitive spectrum of PKS 1830-211 ever obtained and characterize the known H i (z = 0.19) and OH (z = 0.89) absorbers. We further demonstrate ARTIP's capabilities to handle realistic observing scenarios by applying it to a sample of 72 bright radio sources observed with the upgraded Giant Metrewave Radio Telescope (uGMRT) to blindly search for H i and OH absorbers. We estimate the numbers of H i and OH absorbers per unit redshift to be n 21(z ∼ 0.18) < 0.14 and n OH(z ∼ 0.40) < 0.12, respectively, and constrain the cold gas covering factor of galaxies at large impact parameters (50 kpc < ρ < 150 kpc) to be less than 0.022. Due to the small redshift path, Δz ∼ 13 for H i with column density >5.4 × 1019 cm−2, the survey has probed only the outskirts of star-forming galaxies at ρ > 30 kpc. MALS with the expected Δz ∼ 103–4 will overcome this limitation and provide stringent constraints on the cold gas fraction of galaxies in diverse environments over 0 < z < 1.5.
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