J/A+A/592/A94ivo://CDS.VizieR/J/A+A/592/A94doi:10.26093/cds/vizier.35920094CDSFrank B.S.Morganti R.Oosterloo T.Nyland K.Serra P.2016-08-04T08:19:19Z2016-08-04T09:18:43ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frgalaxiesradio-sourcesh-i-line-emissionWe 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 HI 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 HI disc warps back towards the stellar mid-plane in a way that mirrors the warping of the radio lobes. We suggest that the polar HI 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.2016A&A...592A..94Fhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/592/A94CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/592/A94https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/592/A94http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/592/A94https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/592/A94https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/592/A94http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/592/A94GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/592/A94/list (List of fits files)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/592/A94/list?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/592/A94/list?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/592/A94/list?GETtext/xml+votable180.050000true179.4827855.45250.0055555555555555566/5975https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/592/A94?format=asciiRadiodefaultJ/A+A/592/A94/listList of fits filesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAJ2000Right Ascension of center (J2000)degpos.eq.ra;meta.mainDEJ2000Declination of center (J2000)degpos.eq.dec;meta.mainNx[1050] Number of pixels along X-axismeta.numberintNy[1050] Number of pixels along Y-axismeta.numberintNz[150]? Number of slicesmeta.numberintnullableObs.DateObservation date (YYYY-MM-DDThh:mm:ss.ss)time.epoch;obscharFreqFrequency or lower value of frequency intervalHzem.freqdoubleBFreq? Upper value of frequency intervalHzem.freq;stat.maxdoublenullabledFreq? Frequency resolutionHzspect.resolutionfloatnullablesizeSize of FITS fileKibytephys.size;meta.fitsintFileNameName of FITS file, in subdirectory fitsmeta.id;meta.fitscharTitleTitle of the FITS filemeta.title;meta.fitschar