PKS1830-211: OH and HI at z=0.89 and the first MeerKAT UHF spectrum
  The Large Survey Project (LSP) "MeerKAT Absorption Line Survey" (MALS) is a
blind HI 21-cm and OH 18-cm absorption line survey in the L- and UHF-bands,
with the primary goal to better determine the occurrence of atomic and
molecular gas in the circum-galactic and inter-galactic medium, and its
redshift evolution. Here we present the first results using the UHF-band,
obtained towards the strongly lensed radio source PKS1830, detecting absorption
in the lens galaxy. With merely 90min of data acquired on-source for science
verification and processed using the Automated Radio Telescope Imaging Pipeline
(ARTIP), we detect in absorption the known HI 21-cm and OH 18-cm main lines at
z=0.89 at an unprecedented signal-to-noise ratio (4000 in the continuum, with
6km/s channels). For the first time we report the detection at z=0.89 of OH
satellite lines, so far not detected at z $>$ 0.25. We decompose the OH lines
into a thermal and a stimulated contribution, where the 1612 and 1720MHz lines
are conjugate. The total OH 1720MHz emission line luminosity is 6100Lsun. This
is the most luminous known 1720MHz maser line. The absorption components of the
different images of the background source sample different light paths in the
lensing galaxy, and their weights in the total absorption spectrum are expected
to vary in time, on daily and monthly time scales. We compare our normalized
spectra with those obtained more than 20 yrs ago, and find no variation. We
interpret the absorption spectra with the help of a lens galaxy model, derived
from an N-body hydro-dynamical simulation, with a morphology similar to its
optical HST image. It is possible to reproduce the observations without
invoking any central gas outflows. There are, however, distinct and faint
high-velocity features, most likely high-velocity clouds. These clouds may
contribute to broaden the HI and OH spectra.
