J/A+A/622/A13ivo://CDS.VizieR/J/A+A/622/A13doi:10.26093/cds/vizier.36220013CDSMahatma V.H.Hardcastle M.J.Williams W.L.Best P.N.Croston J.H.,Duncan K.Mingo B.Morganti R.Brienza M.Cochrane R.K.Guerkan G.,Harwood J.J.Jarvis M.J.Jamrozy M.Jurlin N.Morabito L.K.,Roettgering H.J.A.Sabater J.Shimwell T.W.Smith D.J.B.Shulevski A.,Tasse C.2020-08-25T14:08:09Z2019-02-21T17:23:36ZCDS support team

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

cds-question@unistra.fractive-galactic-nucleiradio-galaxiesDouble-double radio galaxies (DDRGs) represent a short but unique phase in the life-cycle of some of the most powerful radio-loud active galactic nuclei (RLAGN). These galaxies display large-scale remnant radio plasma in the intergalactic medium left behind by a past episode of active galactic nuclei (AGN) activity, and meanwhile, the radio jets have restarted in a new episode. The knowledge of what causes the jets to switch off and restart is crucial to our understanding of galaxy evolution, while it is important to know if DDRGs form a host galaxy dichotomy relative to RLAGN. The sensitivity and field of view of LOFAR enables the observation of DDRGs on a population basis rather than single-source observations. Using statistical comparisons with a control sample of RLAGN, we may obtain insights into the nature of DDRGs in the context of their host galaxies, where physical differences in their hosts compared to RLAGN as a population may allow us to infer the conditions that drive restarting jets. We utilised the LOFAR Two-Metre Sky Survey (LoTSS) DR1, using a visual identification method to compile a sample of morphologically selected candidate DDRGs, showing two pairs of radio lobes. To confirm the restarted nature in each of the candidate sources, we obtained follow-up observations with the Karl. G. Jansky Very Large Array (VLA) at higher resolution to observe the inner lobes or restarted jets, the confirmation of which created a robust sample of 33 DDRGs.We created a comparison sample of 777 RLAGN, matching the luminosity distribution of the DDRG sample, and compared the optical and infrared magnitudes and colours of their host galaxies. We find that there is no statistically significant difference in the brightness of the host galaxies between double-doubles and single-cycle RLAGN. The DDRG and RLAGN samples also have similar distributions in WISE mid-infrared colours, indicating similar ages of stellar populations and dust levels in the hosts of DDRGs. We conclude that DDRGs and 'normal' RLAGN are hosted by galaxies of the same type, and that DDRG activity is simply a normal part of the life cycle of RLAGN. Restarted jets, particularly for the class of low-excitation radio galaxies, rather than being a product of a particular event in the life of a host galaxy, must instead be caused by smaller scale changes, such as in the accretion system surrounding the black hole.2019A&A...622A..13Mhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/622/A13CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/A+A/622/A1 : LOFAR Two-metre Sky Survey DR1 source catalog (Shimwell+, 2019)J/A+A/622/A4 : LOFAR observations XMM-LSS field (Hale+, 2019)J/A+A/622/A8 : NGC 3184, 4736, 5055 and 5194 LOFAR & WSRT maps (Heesen+, 2019)J/A+A/622/A11 : LoTSS/HETDEX. Optical quasars. I. (Guerkan+, 2019)J/A+A/622/A15 : Broad absorption line quasars in LDR1 (Morabito+, 2019)J/A+A/622/A22 : Abell 1914 multiwavelength radio images (Mandal+, 2019)J/A+A/622/A23 : LoTSS HCG and MLCG systems (Nikiel-wroczynski+, 2019)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/622/A13https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/622/A13http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/622/A13https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/622/A13https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/622/A13http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/622/A13GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/622/A13/list (List of fits images)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/622/A13/list?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/622/A13/list?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/622/A13/list?GETtext/xml+votable180.050000true162.891208351.747550.0055555555555555566/5583 5591 5600 5611 5916 5940 5948 5997 6081 10745 10941 10967 10971-10972 10979 10986 10995 11001 11026 11034 11042 11045 11094 11098 11112 11116 11122 11139 11168 11208 11301 11303-11304 11336 11339 11360 11399 11413https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/622/A13?format=asciiRadiodefaultJ/A+A/622/A13/listList of fits imagesz? Redshift (1)src.redshiftfloatnullablerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameName (ILTJHHMMSS.ss+DDMMSS.s) (1)meta.id;meta.maincharn_Name[+] Note on name (1) (2)meta.notecharRAJ2000Right ascension (J2000) (1)pos.eq.ra;meta.mainDEJ2000Declination (J2000) (1)pos.eq.dec;meta.mainONameOther name (1) (3)meta.idcharu_Name[*] * for Misidentified source (see Section 2.2.3 of the paper)meta.code.errorcharn_z[sp] Spectroscopic (s) or photometric (p) redshift (1)meta.notecharNxNumber of pixels along X-axismeta.numberintNyNumber of pixels along Y-axismeta.numberintObs.dateObservation date (YYYY-MM-DDThh.mm.ss.ssssss)stime.epoch;obsnullableFreq[1.5195] Observed frequencyGHzem.freqfloatsizeSize of FITS fileKibytephys.size;meta.fitsintFileNameName of FITS file, in subdirectory fitsmeta.id;meta.fitscharSimbadSimbad column added by the CDSmeta.ref.urlchar