| Name: Partha Pratim Deka |
| Affiliation: University of Cape Town, South Africa |
| Conference ID: ASI2026_470 |
| Title: An "unbiased" view of cold atomic gas associated with radio-loud AGNs from the MeerKAT Absorption Line Survey (MALS) |
| Abstract Type: Poster |
| Abstract Category: Galaxies and Cosmology |
| Author(s) and Co-Author(s) with Affiliation: Partha Pratim Deka(University of Cape Town, South Africa), Neeraj Gupta(IUCAA, India) |
| Abstract: The MeerKAT Absorption Line Survey (MALS) has observed 391 telescope pointings at L-band (900-1670 MHz) at declinations < +20 degrees. In this talk, I will present radio continuum images and a catalog of 715,760 unique radio sources detected at SNR > 5 over an area of ~3000 deg^2 across 15 spectral windows (SPWs) within the L-band. We used catalogs at 1.0 and 1.4 GHz to characterize the properties of these sources. With excellent continuum sensitivity (20 microJy/beam) and spectral sensitivity (0.5 mJy/beam per 6 km/s channel), this catalog forms the base for future HI 21-cm and OH 18-cm absorption line searches, addressing the main theme of MALS: evolution of cold gas in galaxies up to z ~ 2. The MALS catalogs and images are publicly available at https://mals.iucaa.in. Moreover, by combining optical spectroscopy from SDSS with radio properties from MALS, we created a sample of 352 low- and high-excitation radio galaxies. The talk will present results from the search for HI 21-cm absorption in these systems, highlighting statistical differences in the properties of cold gas - an aspect currently underrepresented in the literature. Additionally, I will discuss the detection of HI 21-cm absorption associated with a QSO at z = 1.353. By analyzing this source alongside literature samples of QSOs and radio galaxies with HI absorption, we conducted a joint radio and optical analysis to constrain the location and characteristics of cold gas in quasars versus radio galaxies. The talk will conclude with the new opportunities that will be offered by upcoming facilities such as ngVLA and SKA in order to better understand the properties of cold gas associated with AGNs and its evolution across cosmic time.
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