| Description: | Deep galaxy surveys have revealed that the global star formation rate density in the Universe peaks at z~1-2 and sharply declines towards z = 0. The star formation rate (SFR) is directly related to the amount of the cold gas present in galaxies and its physical properties. However, very little is known about the evolution of cold gas in galaxies. Recently, 4000 hrs of MeerKAT time has been allocated to the MeerKAT Absorption Line Survey (MALS) to trace the evolution of cold gas in galaxies in an unbiased way and unravel the physical processes that drive the evolution of SFR. MALS is led by Neeraj Gupta of ASTRON (the Netherlands) and Raghunathan Srianand of IUCAA (India) and involves researchers from the US, India, France, Chile, South Africa and the Netherlands (including Raffaella Morganti and Tom Oosterloo). It is one of the two large MeerKAT surveys led by the researchers from ASTRON (see yesterday's daily image).
MALS will use MeerKAT’s 0.58-1.75 GHz frequency band to search for 21-cm absorbers at z<1.5 and OH absorbers at z<1.8. It expects to detect more than 650 HI 21-cm absorption systems at z<1.5. This is approximately 20 times the number of 21-cm absorbers known today. The main goals are (i) to reliably measure the number density of 21-cm absorbers per unit redshift and its evolution in the redshift range z<1.5, (ii) to measure, for the first time, the number density per unit redshift of OH absorbers over the redshift range z<1.8, (iii) to probe the redshift clustering of HI 21-cm and OH absorbers, (iv) to constrain the variation of fundamental constants of physics using OH lines, (v) to estimate the dust bias involved in the 21-cm searches towards optically selected radio sources, (vi) to probe the magnetic field in galaxies through Faraday rotation and Zeeman splitting, and (vii) to study the properties of 21-cm and OH absorbers associated with ~1000 radio sources. All data and data products will be publicly available. The sample of detected 21-cm and OH absorbers will be ideally suited for various multi-wavelength projects that can be undertaken by the astronomy community using ALMA, EVLA, VLBA, SALT and VLT.
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