J/A+A/699/A319ivo://CDS.VizieR/J/A+A/699/A319doi:10.26093/cds/vizier/bc-nv/ldbjCDSArias M.Timmerman R.Sweijen F.van Weeren R.J.Bassa C.G.2026-08-03T06:55:45Z2025-07-16T08:51:15ZCDS support team

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

cds-question@unistra.frsupernova-remnantsradio-sourcesWe present International LOw Frequency ARray (LOFAR) Telescope (ILT) observations of the Crab Nebula, the remnant of a core-collapse supernova explosion observed by astronomers in 1054. The field of the Crab Nebula was observed between 120 and 168MHz as part of the LOFAR Two Meter Sky Survey (LoTSS), and the data were re-processed to include the LOFAR international stations to create a high angular resolution (0.43"x0.28") map at a central frequency of 145MHz. Combining the ILT map with archival centimeter-range observations of the Nebula with the Very Large Array (VLA) and LOFAR data at 54MHz, we become sensitive to the effects of free-free absorption against the synchrotron emission of the pulsar wind nebula. This absorption is caused by the ionised filaments visible in optical and infrared data of the Crab Nebula, which are the result of the pulsar wind nebula expanding into the denser stellar ejecta that surrounds it and forming Rayleigh-Taylor fingers. The LOFAR observations are sensitive to two components of these filaments: their dense cores, which show electron densities of >=1000cm^-3^, and the diffuse envelopes, with electron densities of ~50-250cm^-3^. The denser structures have widths of ~0.03pc, whereas the diffuse component is at one point as large as 0.2pc. The morphology of the two components is not always the same. These finding suggests that the layered temperature, density, and ionisation structure of the Crab optical filaments extends to larger scales than previously considered.2025A&A...699A.319Ahttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/699/A319CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/699/A319https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/699/A319http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/699/A319https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/699/A319https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/699/A319http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/699/A319GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/699/A319/list (List of fits images)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/699/A319/list?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/699/A319/list?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/699/A319/list?GETtext/xml+votable180.050000true83.6304122.022590.0055555555555555566/24185https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/699/A319?format=asciiRadiodefaultJ/A+A/699/A319/listList of fits imagesrecnoRecord 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.mainNxNumber of pixels along X-axismeta.numberintNyNumber of pixels along Y-axismeta.numberintObs.dateObservation datestime.epoch;obsnullableFreqObserved frequencyHzem.freqdoublesizeSize of FITS fileKibytephys.size;meta.fitsintFileNameName of FITS file, in subdirectory fitsmeta.id;meta.fitscharTitleTitle of the FITS filemeta.title;meta.fitschar