The MeerKAT Absorption Line Survey (MALS) Data Release. I. Stokes I Image Catalogs at 1-1.4 GHz
Journal article, 2024
The MeerKAT Absorption Line Survey (MALS) has observed 391 telescope pointings at the L band (900-1670 MHz) at delta less than or similar to +20 degrees. We present radio continuum images and a catalog of 495,325 (240,321) radio sources detected at a signal-to-noise ratio (S/N) > 5 over an area of 2289 deg(2) (1132 deg(2)) at 1006 MHz (1381 MHz). Every MALS pointing contains a central bright radio source (S 1 GHz greater than or similar to 0.2 Jy). The median spatial resolution is 12 ''(8 ''). The median rms noise away from the pointing center is 25 mu Jy beam(-1) (22 mu Jy beam-1) and is within similar to 15% of the achievable theoretical sensitivity. The flux density scale ratio and astrometric accuracy deduced from multiply observed sources in MALS are <1% (8% scatter) and 1 '', respectively. Through comparisons with NVSS and FIRST at 1.4 GHz, we establish the catalog's accuracy in the flux density scale and astrometry to be better than 6% (15% scatter) and 0.'' 8, respectively. The median flux density offset is higher (9%) for an alternate beam model based on holographic measurements. The MALS radio source counts at 1.4 GHz are in agreement with literature. We estimate spectral indices (alpha) of a subset of 125,621 sources (S/N > 8), confirm the flattening of spectral indices with decreasing flux density, and identify 140 ultra-steep-spectrum (alpha < -1.3) sources as prospective high-z radio galaxies (z > 2). We have identified 1308 variable and 122 transient radio sources comprising primarily active galactic nuclei that demonstrate long-term (26 yr) variability in their observed flux densities. The MALS catalogs and images are publicly available at https://mals.iucaa.in.
Author
P. P. Deka
Inter-University Centre for Astronomy and Astrophysics
N. Gupta
Inter-University Centre for Astronomy and Astrophysics
P. Jagannathan
National Radio Astronomy Observatory
S. Sekhar
National Radio Astronomy Observatory
South African Radio Astronomy Observatory (SARAO)
E. Momjian
National Radio Astronomy Observatory
S. Bhatnagar
National Radio Astronomy Observatory
J. Wagenveld
Max Planck Society
H. -R. Kloeckner
Max Planck Society
J. Jose
Thought Works Technol India Pvt Ltd
S. A. Balashev
HSE Univ
Russian Academy of Sciences
F. Combes
Université Paris PSL
M. Hilton
University of Witwatersrand
University of KwaZulu-Natal
D. Borgaonkar
Inter-University Centre for Astronomy and Astrophysics
A. Chatterjee
Thought Works Technol India Pvt Ltd
K. L. Emig
National Radio Astronomy Observatory
A. N. Gaunekar
Thought Works Technol India Pvt Ltd
G. I. G. Jozsa
Max Planck Society
Rhodes University
D. Y. Klutse
University of KwaZulu-Natal
K. Knowles
Rhodes University
J. -k. Krogager
Université de Lyon
A. Mohapatra
Inter-University Centre for Astronomy and Astrophysics
K. Moodley
University of KwaZulu-Natal
Sebastien Muller
Chalmers, Space, Earth and Environment, Onsala Space Observatory
P. Noterdaeme
Centre national de la recherche scientifique (CNRS)
P. Petitjean
Centre national de la recherche scientifique (CNRS)
P. Salas
Green Bank Observ, 155 Observ Rd
S. Sikhosana
University of KwaZulu-Natal
Astrophysical Journal, Supplement Series
0067-0049 (ISSN) 1538-4365 (eISSN)
Vol. 270 2 33Subject Categories (SSIF 2011)
Astronomy, Astrophysics and Cosmology
DOI
10.3847/1538-4365/acf7b9