| Name: | APARNA RAJ |
| Affiliation: | K. E COLLEGE, MANNANAM, KOTTAYAM,KERALA |
| Conference ID : | ASI2024_993 |
| Title : | A Method for Identifying Episodic Radio Sources in Active Galactic Nuclei using Spectral Index Variation |
| Authors : | Aparna Raj, C. H. Ishwara-Chandra, Sudheesh T, Biju K. G,4 and Joe Jacob |
| Authors Affiliation: | 1. (a) Newman College, Thodupuzha, Kerala 685584, India, (b) K.E College, Mannanam, Kerala, 686561, India
2. National Centre for Radio Astrophysics, TIFR, Post Bag No. 3, Ganeshkhind, Pune 411007, India
3. WMO Arts, and Science college, Muttil, Wayanad, Kerala 673122, India.
4. Christ (Deemed to be University), Hosur Rd, Bengaluru, Karnataka 560029, India
5. Newman College, Thodupuzha, Kerala 685584, India |
| Mode of Presentation: | Poster |
| Abstract Category : | Galaxies and Cosmology |
| Abstract : | Active galaxies with radio jets can go through two distinct active phases, which are distinguished by the presence of two sets of radio lobes. These episodic radio sources are typically discovered through morphological investigations, where the presence of these lobes denotes distinct jet activity periods. However, one limitation of this approach is that it does not include sources that lack the obvious double-double morphology. Here, we propose a unique method to identify such sources based on the difference in its spectral index values (Δα) between a set of low and high radio frequencies. This approach is based on the observation that radio emission from the prior episode of (remnant) activity is dominant at low frequencies, whereas the influence of previous activity is comparatively smaller at higher frequencies. The goal of this search is to increase the number of known episodic sources that may not follow clear double-double morphology. Using this technique, we have found 9,407 candidate episodic radio sources by cross-matching the VLSS, TGSS, and NVSS catalogs at frequencies ranging from 74 MHz to 1.4 GHz, and by choosing criteria of Δα >= 0.5.
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