| Name: Aminabi Thekkoth |
| Affiliation: TIFR-National Centre for Radio Astrophysics, Pune |
| Conference ID: ASI2026_844 |
| Title: Revisiting the Morphological Properties of FR II Quasars through uGMRT Observations |
| Abstract Type: Poster |
| Abstract Category: Galaxies and Cosmology |
| Author(s) and Co-Author(s) with Affiliation: Aminabi T(National Centre for Radio Astrophysics, Pune - 411007, India), Preethi Kharb(National Centre for Radio Astrophysics, Pune - 411007, India), Ayan Biswas(National Centre for Radio Astrophysics, Pune - 411007, India), Sravani Vaddi(Arecibo Observatory, PR-625, Arecibo, 00612, Puerto Rico), Salmoli Ghosh(National Centre for Radio Astrophysics, Pune - 411007, India) |
| Abstract: Extended radio AGN are classified as FRI or FRII, where FR II sources consist of a core, collimated jets, large lobes, and bright hotspots at the lobe edges. In some systems, an older pair of outer lobes is also seen, indicating a previous activity episode. A few FRIIs additionally show faint, diffuse emission along a secondary axis, giving them a winged/X-shaped appearance. These features may arise from jet reorientation, instabilities in the accretion disk, or backflow of plasma from the hotspots. Sensitive low-frequency imaging is crucial to test the presence of these features.
In a recent study, Vaddi et al. (2019) analyzed VLA 1.4/5 GHz maps of 11 powerful FR II quasars along with radio galaxies to test orientation effects. The smaller inclination angles inferred for quasars, along with their higher core prominence, support orientation hypothesis. However, quasars also show larger lobe distortions, and the absence of correlations between misalignment angle and radio core prominence suggests intrinsic or environmental influences are significant. Low-frequency 150MHz images of 3C205, 3C208, 3C249, and 3C263 revealed faint extended and X-shaped emission missed in VLA maps. Likewise, GMRT 610 MHz observations of 3C336 and 3 249.1 exposed wing-like relic lobes beyond the 1.4GHz hotspots, pointing episodic activity or jet axis changes.
We are revisiting this study using uGMRT Band 3 and Band 4 observations to detect such features in detail. Initial imaging already shows extended low-frequency emission in some sources. With uGMRT’s wide bandwidth, spectral-index mapping combined with VLA data will allow robust estimates of spectral parameters and help to quantify relic and newly restarted emission. We also plan to incorporate optical and X-ray images to explore the role of the surrounding environment and to test whether jet reorientation or environmental factors primarily shape the observed radio morphology. |
