2025/01/03 by K. Rajpurohit, Rajpurohit, Kamlesh, Tirna Deb +21 · 1 citation
Physics and Astronomy · #Stellar, planetary, and galactic studies #Astrophysical Phenomena and Observations #Astronomy and Astrophysical Research
paper · pdf · doi:10.48550/arxiv.2501.02076
We present new MeerKAT L-band (continuum and HI) and upgraded Giant Metrewave Radio Telescope (300-850 MHz) observations of the archetypal cool-core group-dominant early-type galaxy NGC 5044. Our new continuum images reveal diffuse, steep spectrum (α0.99 \rm GHz1.56 \rm GHz=-1.53±0.6) radio emission extending about 25 kpc around the unresolved radio core. The observed radio emission overlaps with the known X-ray cavities, but is not confined to them. We also find the first direct evidence of neutral atomic gas in NGC 5044, in the form of a 3.8σ significant two-component HI absorption line seen against the emission of the active nucleus. The peak velocities are well correlated with the previously reported CO(2-1) absorption, but the HI lines are moderately broader, spanning velocities from 265 \rm km s-1 to 305 \rm km s-1. We do not detect HI emission, but place an upper limit of MHI< 5.4 × 107 M\odot in the central 15 arcsec (2.2 kpc) of the galaxy. This is significantly less than the estimated molecular gas content, and implies a molecular-to-atomic mass ratio of ≥ 1.7:1, consistent with these gas phases forming through cooling from the hot intra-group medium. We also constrain the spin temperature to T\rm spin≤ 950 \rm K, indicating that the detected HI is in the cold neutral phase.