J/ApJ/793/82ivo://CDS.VizieR/J/ApJ/793/82doi:10.26093/cds/vizier.17930082CDSvan Weeren R.J.Williams W.L.Tasse C.Rottgering H.J.A.Rafferty D.A.,van der Tol S.Heald G.White G.J.Shulevski A.Best P.Intema H.T.,Bhatnagar S.Reich W.Steinmetz M.van Velzen S.Ensslin T.A.,Prandoni I.de Gasperin F.Jamrozy M.Brunetti G.Jarvis M.J.,McKean J.P.Wise M.W.Ferrari C.Harwood J.Oonk J.B.R.Hoeft M.,Kunert-Bajraszewska M.Horellou C.Wucknitz O.Bonafede A.Mohan N.R.,Scaife A.M.M.Klockner H.-R.van Bemmel I.M.Merloni A.Chyzy K.T.,Engels D.Falcke H.Pandey-Pommier M.Alexov A.Anderson J.,Avruch I.M.Beck R.Bell M.E.Bentum M.J.Bernardi G.Breitling F.,Broderick J.Brouw W.N.Bruggen M.Butcher H.R.Ciardi B.de Geus E.,de Vos M.Deller A.Duscha S.Eisloffel J.Fallows R.A.Frieswijk W.,Garrett M.A.Griessmeier J.Gunst A.W.Hamaker J.P.Hassall T.E.,Horandel J.van der Horst A.Iacobelli M.Jackson N.J.Juette E.,Kondratiev V.I.Kuniyoshi M.Maat P.Mann G.McKay-Bukowski D.,Mevius M.Morganti R.Munk H.Offringa A.R.Orru E.Paas H.,Pandey V.N.Pietka G.Pizzo R.Polatidis A.G.Renting A.Rowlinson A.,Schwarz D.Serylak M.Sluman J.Smirnov O.Stappers B.W.Stewart A.,Swinbank J.Tagger M.Tang Y.Thoudam S.Toribio C.Vermeulen R.,Vocks C.Zarka P.2017-06-08T12:22:19Z2017-05-03T15:34:01ZCDS support team

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

cds-question@unistra.frseyfert-galaxiesinterferometrysurveysradio-sourcesWe present Low Frequency Array (LOFAR) Low Band observations of the Bootes and 3C 295 fields. Our images made at 34, 46, and 62 MHz reach noise levels of 12, 8, and 5 mJy/beam, making them the deepest images ever obtained in this frequency range. In total, we detect between 300 and 400 sources in each of these images, covering an area of 17-52 deg^2^. From the observations, we derive Euclidean-normalized differential source counts. The 62 MHz source counts agree with previous GMRT 153 MHz and Very Large Array 74 MHz differential source counts, scaling with a spectral index of -0.7. We find that a spectral index scaling of -0.5 is required to match up the LOFAR 34 MHz source counts. This result is also in agreement with source counts from the 38 MHz 8C survey, indicating that the average spectral index of radio sources flattens toward lower frequencies. We also find evidence for spectral flattening using the individual flux measurements of sources between 34 and 1400 MHz and by calculating the spectral index averaged over the source population. To select ultra-steep spectrum ({alpha}<-1.1) radio sources that could be associated with massive high-redshift radio galaxies, we compute spectral indices between 62 MHz, 153 MHz, and 1.4 GHz for sources in the Bootes field. We cross-correlate these radio sources with optical and infrared catalogs and fit the spectral energy distribution to obtain photometric redshifts. We find that most of these ultra-steep spectrum sources are located in the 0.7<~z<~2.5 range.2014ApJ...793...82Vhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/793/82CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/AJ/130/923 : Faint radio sources in the NOAO Bootes field (Wrobel+, 2005)J/A+A/598/A104 : LOFAR Two-metre Sky Survey (Shimwell+, 2017)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/793/82https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/793/82http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/793/82https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/793/82https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/793/82http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/793/82GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/793/82/table3 (Combined LOFAR Bootes and 3C295 field source catalogs)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/793/82/table3?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/793/82/table3?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/793/82/table3?GETtext/xml+votable180.050000true220.8276233.186050.0055555555555555564/671 5/2286 2287 2628 2629 2679 2683 2772 2773 2850 2851 2856 2858 6/9133 9135 9139 9142 9143 9192 9194 10501 10503 10520 10521 10524 10525 10560 10710 10711 10714 10715 10725 10727 11076 11077 11394 11395 11398 11399 11416 11428 11429 11430 11436 11437 11438 11440 11776 11777 11778https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/793/82?format=asciiRadiodefaultJ/ApJ/793/82/table3Combined LOFAR Bootes and 3C295 field source catalogsIDSource identifier (JHHMMSS.s+DDMMSS)meta.id;meta.maincharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintFieldField identifiermeta.id;obs.fieldcharFreqObservational frequency (34, 46 or 62)MHzem.freqintRAJ2000Right Ascension in decimal degrees (J2000)degpos.eq.ra;meta.maine_RAJ2000The 1{sigma} uncertainty in RAdegarcsecstat.error;pos.eq.rafloatDEJ2000Declination in decimal degrees (J2000)degpos.eq.dec;meta.maine_DEJ2000The 1{sigma} uncertainty in DEdegarcsecstat.error;pos.eq.decfloatSLOFAR flux density at FreqmJyphot.flux.density;em.radiointe_SThe 1{sigma} uncertainty in SmJystat.errorint