A rare example of low surface-brightness radio lobes in a gas-rich early-type galaxy: the story of NGC 3998

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dc.contributor.authorFrank, Bradley S
dc.contributor.authorMorganti, Raffaella
dc.contributor.authorOosterloo, Tom
dc.contributor.authorNyland, Kristina
dc.contributor.authorSerra, Paolo
dc.date.accessioned2021-10-08T06:20:34Z
dc.date.available2021-10-08T06:20:34Z
dc.date.issued2016
dc.description.abstractWe study the nearby lenticular galaxy NGC 3998. This galaxy is known to host a low-power radio AGN with a kpc-size one-sided jet and a large, nearly polar H i disc. It is therefore a good system to study to understand the relation between the availability of cold-gas and the triggering of AGNs in galaxies. Our new WSRT data reveal two faint, S-shaped radio lobes extending out to ~10 kpc from the galaxy centre. Remarkably, we find that the inner H i disc warps back towards the stellar mid-plane in a way that mirrors the warping of the radio lobes. We suggest that the polar H i disc was accreted through a minor merger, and that the torques causing it to warp in the inner regions are also responsible for feeding the AGN. The “S” shape of the radio lobes would then be due to the radio jets adapting to the changing angular momentum of the accreted gas. The extended radio jets are likely poorly collimated, which would explain their quick fading and, therefore, their rarity in galaxies similar to NGC 3998. The fuelling of the central super-massive black hole is likely occurring via “discrete events”, suggested by the observed variability of the radio core and the extremely high core dominance, which we attribute to the formation and ejection of a new jet resulting from a recent fuelling event.
dc.identifier.apacitationFrank, B. S., Morganti, R., Oosterloo, T., Nyland, K., & Serra, P. (2016). A rare example of low surface-brightness radio lobes in a gas-rich early-type galaxy: the story of NGC 3998. <i>Astronomy and Astrophysics</i>, 592(4), A94 - 177. http://hdl.handle.net/11427/34308en_ZA
dc.identifier.chicagocitationFrank, Bradley S, Raffaella Morganti, Tom Oosterloo, Kristina Nyland, and Paolo Serra "A rare example of low surface-brightness radio lobes in a gas-rich early-type galaxy: the story of NGC 3998." <i>Astronomy and Astrophysics</i> 592, 4. (2016): A94 - 177. http://hdl.handle.net/11427/34308en_ZA
dc.identifier.citationFrank, B.S., Morganti, R., Oosterloo, T., Nyland, K. & Serra, P. 2016. A rare example of low surface-brightness radio lobes in a gas-rich early-type galaxy: the story of NGC 3998. <i>Astronomy and Astrophysics.</i> 592(4):A94 - 177. http://hdl.handle.net/11427/34308en_ZA
dc.identifier.issn0004-6361
dc.identifier.issn1432-0746
dc.identifier.ris TY - Journal Article AU - Frank, Bradley S AU - Morganti, Raffaella AU - Oosterloo, Tom AU - Nyland, Kristina AU - Serra, Paolo AB - We study the nearby lenticular galaxy NGC 3998. This galaxy is known to host a low-power radio AGN with a kpc-size one-sided jet and a large, nearly polar H i disc. It is therefore a good system to study to understand the relation between the availability of cold-gas and the triggering of AGNs in galaxies. Our new WSRT data reveal two faint, S-shaped radio lobes extending out to ~10 kpc from the galaxy centre. Remarkably, we find that the inner H i disc warps back towards the stellar mid-plane in a way that mirrors the warping of the radio lobes. We suggest that the polar H i disc was accreted through a minor merger, and that the torques causing it to warp in the inner regions are also responsible for feeding the AGN. The “S” shape of the radio lobes would then be due to the radio jets adapting to the changing angular momentum of the accreted gas. The extended radio jets are likely poorly collimated, which would explain their quick fading and, therefore, their rarity in galaxies similar to NGC 3998. The fuelling of the central super-massive black hole is likely occurring via “discrete events”, suggested by the observed variability of the radio core and the extremely high core dominance, which we attribute to the formation and ejection of a new jet resulting from a recent fuelling event. DA - 2016 DB - OpenUCT DP - University of Cape Town IS - 4 J1 - Astronomy and Astrophysics LK - https://open.uct.ac.za PY - 2016 SM - 0004-6361 SM - 1432-0746 T1 - A rare example of low surface-brightness radio lobes in a gas-rich early-type galaxy: the story of NGC 3998 TI - A rare example of low surface-brightness radio lobes in a gas-rich early-type galaxy: the story of NGC 3998 UR - http://hdl.handle.net/11427/34308 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/34308
dc.identifier.vancouvercitationFrank BS, Morganti R, Oosterloo T, Nyland K, Serra P. A rare example of low surface-brightness radio lobes in a gas-rich early-type galaxy: the story of NGC 3998. Astronomy and Astrophysics. 2016;592(4):A94 - 177. http://hdl.handle.net/11427/34308.en_ZA
dc.language.isoeng
dc.publisher.departmentDepartment of Astronomy
dc.publisher.facultyFaculty of Science
dc.sourceAstronomy and Astrophysics
dc.source.journalissue4
dc.source.journalvolume592
dc.source.paginationA94 - 177
dc.source.urihttps://dx.doi.org/10.1051/0004-6361/201628282
dc.subject.othergalaxies: active
dc.subject.othergalaxies: individual: NGC 3998
dc.subject.otherISM: jets and outflows
dc.subject.otherradio continuum: galaxies
dc.subject.otherradio lines: galaxies
dc.subject.otherhistory and philosophy of astronomy
dc.titleA rare example of low surface-brightness radio lobes in a gas-rich early-type galaxy: the story of NGC 3998
dc.typeJournal Article
uct.type.publicationResearch
uct.type.resourceJournal Article
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