| Name: Barenya Dev |
| Affiliation: Indian Institute of Technology Indore |
| Conference ID: ASI2026_1074 |
| Title: Extreme radio spectra and dense environments in compact AGN |
| Abstract Type: Poster |
| Abstract Category: Galaxies and Cosmology |
| Author(s) and Co-Author(s) with Affiliation: Mukul Mhaskey(Homi Bhabha Centre for Science Education (HBCSE-TIFR), Mumbai - 400008, India), Baraneya Dev(Indian Institute of Technology, Indrore - 453552, India), Surajit Paul(Manipal Centre for Natural Sciences, Centre of Excellence, Manipal Academy of Higher Education, Manipal - 576104, India) |
| Abstract: Low-frequency spectral turnovers in compact radio galaxies (peaked spectrum sources) provide crucial insight into the early evolution of active galactic nuclei (AGN) and their interaction with dense galactic environments. Sources exhibiting extreme spectral inversion at metre wavelengths are particularly valuable, as their radio spectra encode both intrinsic synchrotron processes and the effects of surrounding ionised media. Interpreting such sources, however, has been limited by sparse spectral coverage and non-simultaneous observations.
We present a broadband radio study of a sample of extremely inverted-spectrum compact radio galaxies using quasi-simultaneous observations with the upgraded Giant Metrewave Radio Telescope (uGMRT) between 150 and 1400 MHz and the Karl G. Jansky Very Large Array (VLA) between 1 and 8 GHz. These data yield well-sampled radio spectral energy distributions that robustly capture the spectral turnover and optically thick regime while minimising variability and flux-scale uncertainties. All sources show pronounced low-frequency turnovers, typically around 0.5-1 GHz, with optically thick spectral indices that are steeper than the canonical value of +2.5 expected for homogeneous synchrotron self-absorption (SSA). We model the spectra using a composite radiative transfer framework combining inhomogeneous SSA with external free-free absorption (FFA). The results demonstrate that pure SSA models are generally insufficient and that absorption by dense ionised foreground gas is often required to reproduce the observed extreme spectral inversion and broad turnover shapes. The inferred free-free optical depths imply high emission measures and electron densities on parsec scales.
Our study provides one of the most systematic broadband characterisations of extremely inverted peaked spectrum radio galaxies to date, establishing these sources as a distinct population of compact radio galaxies shaped by both intrinsic synchrotron inhomogeneity and strong jet-environment interaction, and highlighting their importance as probes of early or environmentally confined phases of radio AGN activity.
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