Remnant Radio Galaxy Candidates of Small Angular Sizes
Remnant radio galaxies (RRGs), characterized by the cessation of AGN activity, represent a short-lived last phase of radio galaxy’s life-cycle. Hitherto, searches for RRGs, mainly based on the morphological criteria, have identified large angular size sources resulting into a bias towards the remnan...
| Κύριοι συγγραφείς: | , , , |
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| Μορφή: | Άρθρο |
| Γλώσσα: | English |
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MDPI AG
2021-12-01
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| Σειρά: | Galaxies |
| Θέματα: | |
| Διαθέσιμο Online: | https://www.mdpi.com/2075-4434/9/4/121 |
| _version_ | 1827672290834251776 |
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| author | Veeresh Singh Sushant Dutta Yogesh Wadadekar C. H. Ishwara-Chandra |
| author_facet | Veeresh Singh Sushant Dutta Yogesh Wadadekar C. H. Ishwara-Chandra |
| author_sort | Veeresh Singh |
| collection | DOAJ |
| description | Remnant radio galaxies (RRGs), characterized by the cessation of AGN activity, represent a short-lived last phase of radio galaxy’s life-cycle. Hitherto, searches for RRGs, mainly based on the morphological criteria, have identified large angular size sources resulting into a bias towards the remnants of powerful FR-II radio galaxies. In this study we make the first attempt to perform a systematic search for RRGs of small angular sizes (<30<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mrow></mrow><mrow><mo>″</mo></mrow></msup></semantics></math></inline-formula>) in the XMM–LSS field. By using spectral curvature criterion we discover 48 remnant candidates exhibiting strong spectral curvature i.e., <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msubsup><mi>α</mi><mrow><mn>150</mn><mspace width="3.33333pt"></mspace><mi>MHz</mi></mrow><mrow><mn>325</mn><mspace width="3.33333pt"></mspace><mi>MHz</mi></mrow></msubsup><mo>−</mo><msubsup><mi>α</mi><mrow><mn>325</mn><mspace width="3.33333pt"></mspace><mi>MHz</mi></mrow><mrow><mn>1.4</mn><mspace width="3.33333pt"></mspace><mi>GHz</mi></mrow></msubsup></mrow></semantics></math></inline-formula> ≥ 0.5. Spectral characteristics at higher frequency regime (>1.4 GHz) indicate that some of our remnant candidates can depict recurrent AGN activity with an active core. We place an upper limit on the remnant fraction (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>f</mi><mi>rem</mi></msub></semantics></math></inline-formula>) to be 3.9%, which increases to 5.4% if flux cutoff limit of S<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mrow></mrow><mrow><mn>150</mn><mspace width="3.33333pt"></mspace><mi>MHz</mi></mrow></msub></semantics></math></inline-formula> ≥ 10 mJy is considered. Our study unveils, hitherto unexplored, a new population of small-size (<200 kpc) remnant candidates that are often found to reside in less dense environments and at higher redshifts (<i>z</i>) > 1.0. We speculate that a relatively shorter active phase and/or low jet power can be plausible reasons for the small size of remnant candidates. |
| first_indexed | 2024-03-10T04:04:25Z |
| format | Article |
| id | doaj.art-8003d98d3ee0499bae982a8ebb348d9c |
| institution | Directory Open Access Journal |
| issn | 2075-4434 |
| language | English |
| last_indexed | 2024-03-10T04:04:25Z |
| publishDate | 2021-12-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Galaxies |
| spelling | doaj.art-8003d98d3ee0499bae982a8ebb348d9c2023-11-23T08:26:31ZengMDPI AGGalaxies2075-44342021-12-019412110.3390/galaxies9040121Remnant Radio Galaxy Candidates of Small Angular SizesVeeresh Singh0Sushant Dutta1Yogesh Wadadekar2C. H. Ishwara-Chandra3Physical Research Laboratory, Ahmedabad 380009, IndiaPhysical Research Laboratory, Ahmedabad 380009, IndiaNational Centre for Radio Astrophysics—TIFR, Pune 411007, IndiaNational Centre for Radio Astrophysics—TIFR, Pune 411007, IndiaRemnant radio galaxies (RRGs), characterized by the cessation of AGN activity, represent a short-lived last phase of radio galaxy’s life-cycle. Hitherto, searches for RRGs, mainly based on the morphological criteria, have identified large angular size sources resulting into a bias towards the remnants of powerful FR-II radio galaxies. In this study we make the first attempt to perform a systematic search for RRGs of small angular sizes (<30<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mrow></mrow><mrow><mo>″</mo></mrow></msup></semantics></math></inline-formula>) in the XMM–LSS field. By using spectral curvature criterion we discover 48 remnant candidates exhibiting strong spectral curvature i.e., <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msubsup><mi>α</mi><mrow><mn>150</mn><mspace width="3.33333pt"></mspace><mi>MHz</mi></mrow><mrow><mn>325</mn><mspace width="3.33333pt"></mspace><mi>MHz</mi></mrow></msubsup><mo>−</mo><msubsup><mi>α</mi><mrow><mn>325</mn><mspace width="3.33333pt"></mspace><mi>MHz</mi></mrow><mrow><mn>1.4</mn><mspace width="3.33333pt"></mspace><mi>GHz</mi></mrow></msubsup></mrow></semantics></math></inline-formula> ≥ 0.5. Spectral characteristics at higher frequency regime (>1.4 GHz) indicate that some of our remnant candidates can depict recurrent AGN activity with an active core. We place an upper limit on the remnant fraction (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>f</mi><mi>rem</mi></msub></semantics></math></inline-formula>) to be 3.9%, which increases to 5.4% if flux cutoff limit of S<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mrow></mrow><mrow><mn>150</mn><mspace width="3.33333pt"></mspace><mi>MHz</mi></mrow></msub></semantics></math></inline-formula> ≥ 10 mJy is considered. Our study unveils, hitherto unexplored, a new population of small-size (<200 kpc) remnant candidates that are often found to reside in less dense environments and at higher redshifts (<i>z</i>) > 1.0. We speculate that a relatively shorter active phase and/or low jet power can be plausible reasons for the small size of remnant candidates.https://www.mdpi.com/2075-4434/9/4/121galaxies: nucleigalaxies: jetsradio continuum: galaxiesgalaxies: evolution |
| spellingShingle | Veeresh Singh Sushant Dutta Yogesh Wadadekar C. H. Ishwara-Chandra Remnant Radio Galaxy Candidates of Small Angular Sizes Galaxies galaxies: nuclei galaxies: jets radio continuum: galaxies galaxies: evolution |
| title | Remnant Radio Galaxy Candidates of Small Angular Sizes |
| title_full | Remnant Radio Galaxy Candidates of Small Angular Sizes |
| title_fullStr | Remnant Radio Galaxy Candidates of Small Angular Sizes |
| title_full_unstemmed | Remnant Radio Galaxy Candidates of Small Angular Sizes |
| title_short | Remnant Radio Galaxy Candidates of Small Angular Sizes |
| title_sort | remnant radio galaxy candidates of small angular sizes |
| topic | galaxies: nuclei galaxies: jets radio continuum: galaxies galaxies: evolution |
| url | https://www.mdpi.com/2075-4434/9/4/121 |
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