J/A+A/620/A74ivo://CDS.VizieR/J/A+A/620/A74doi:10.26093/cds/vizier.36200074CDSRetana-Montenegro E.Rottgering H.J.AShimwell T.W.van Weeren R.J.,Prandoni I.Brunetti G.Best P.NBruggen M.2019-01-07T09:20:25Z2018-12-03T14:15:21ZCDS support team

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

cds-question@unistra.frsurveysradio-galaxiesradio-continuum-emissionWe have conducted a deep survey (with a central rms of 55uJy) with the LOw Frequency ARray (LOFAR) at 120-168MHz of the Bootes field, with an angular resolution of 3.98"x6.45", and obtained a sample of 10091 radio sources (5{sigma} limit) over an area of 20deg^2^. The astrometry and flux scale accuracy of our source catalog is investigated. The resolution bias, incompleteness and other systematic effects that could affect our source counts are discussed and accounted for. The derived 150MHz source counts present a flattening below sub-mJy flux densities, that is in agreement with previous results from high- and low- frequency surveys. This flattening has been argued to be due to an increasing contribution of star-forming galaxies and faint active galactic nuclei. Additionally, we use our observations to evaluate the contribution of cosmic variance to the scatter in source counts measurements. The latter is achieved by dividing our Bootes mosaic into 10 non-overlapping circular sectors, each one with an approximate area of 2deg^2^. The counts in each sector are computed in the same way as done for the entire mosaic. By comparing the induced scatter with that of counts obtained from depth observations scaled to 150MHz, we find that the 1{sigma} scatter due to cosmic variance is larger than the Poissonian errors of the source counts, and it may explain the dispersion from previously reported depth source counts at flux densities S<1mJy. This work demonstrates the feasibility of achieving deep radio imaging at low-frequencies with LOFAR.2018A&A...620A..74Rhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/620/A74CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/AJ/123/1784 : 1.4GHz imaging of the Bootes field (de Vries+, 2002)J/AJ/127/213 : LALA Bootes field X-ray source catalog (Wang+, 2004)J/AJ/130/923 : Faint radio sources in the NOAO Bootes field (Wrobel+, 2005)J/ApJ/634/L1 : 16{mu}m sources in the NOAO Bootes field (Kasliwal+, 2005)J/ApJS/161/9 : X-ray survey of the NDWFS Bootes field (Kenter+, 2005)J/ApJ/641/140 : Optical counterparts in the NDWFS Bootes field (Brand+ 2006)J/A+A/535/A38 : Observations of NOAO Bootes field at 153MHz (Intema+, 2011)J/ApJ/793/82 : LOFAR Bootes and 3C295 field sources (van Weeren+, 2014)J/MNRAS/450/1477 : VLA 352MHz image of the Bootes field. I. (Coppejans+, 2015)J/ApJ/817/119 : Bootes field Spitzer/IRAC variability surveyJ/MNRAS/460/2385 : Bootes field LOFAR 150-MHz observations (Williams+, 2016)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/620/A74https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/620/A74http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/620/A74https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/620/A74https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/620/A74http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/620/A74GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/620/A74/table2 (LOFAR source catalog)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/620/A74/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/620/A74/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/620/A74/table2?GETtext/xml+votable180.050000true221.058734.36160.005555555555555556Cone search capability for table J/A+A/620/A74/list (Information on fits image)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/620/A74/list?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/620/A74/list?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/620/A74/list?GETtext/xml+votable180.050000true217.819534.218140.0055555555555555565/2286-2287 2628-2629 6/9133 9135 9138-9139 9142-9143 9186 9192 9194-9195 10501 10503 10509 10520-10521 10523-10525 10560 105629.939104750406538e-26 9.939104750406538e-26https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/620/A74?format=asciiRadiodefaultJ/A+A/620/A74/table2LOFAR source catalogrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSourceIDSource name (JHHMMSS.ss+DDMMSS.s) (Source_ID)meta.id;meta.maincharRAJ2000Right ascension (J2000) (RA)degpos.eq.ra;meta.maine_RAJ2000rms uncertainty on RAdeg (E_RA)degstat.error;pos.eq.radoubleDEJ2000Declination (J2000) (DEC)degpos.eq.dec;meta.maine_DEJ2000rms uncertainty on DEdeg (E_DEC)degstat.error;pos.eq.decdoubleFtotalIntegrated source flux density at 150MHz (Ftotal)mJyphot.flux.density;em.radio.100-200MHzdoublee_Ftotalrms uncertainty on Ftotal (e_Ftotal)mJystat.errordoubleFpeakPeak flux density at 150MHzmJy/beamphot.flux.density;em.radio.100-200MHzdoublee_Fpeakrms uncertainty on Fpeak (e_Fpeak)mJy/beamstat.errordoubleFsmearApproximate correction factor to the peak flux density to account for bandwidth- and time-smearing (Fsmear)instr.paramfloatrmsLocal rms noise used for the source detection (rms)mJy/beamstat.stdev;instr.det.noisefloatType[R/U] flag indicating if the source is resolved (R) or unresolved (U) (1)meta.code.errorcharPyBDSF[S/M] flag indicating the source structure code by PyBDSF (PyBDSF_code) (2)meta.codecharEdge[0/1] an object that is located close to or in a facet edge, which could result in some flux loss (Flag_edge)meta.codeintArtifact[0/2] a source is identified as an artefact (Flag_artifact) (3)meta.codeintMerged[0/1] a large diffuse source whose separate components are merged into a single one according to a visual inspection (Flag_merged)meta.codeintJ/A+A/620/A74/listInformation on fits imageNxNumber of pixels along X-axismeta.numberintrecnoRecord 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.mainNyNumber of pixels along Y-axismeta.numberintObs.DateObservation date (YYYY-MM-DDThh:mm:ss.s)time.epoch;obscharFreqObserved frequencyMHzem.freqfloatsizeSize of FITS fileKibytephys.size;meta.fitsintFileNameName of FITS file, in subdirectory fitsmeta.id;meta.fitscharTitleTitle of the FITS filemeta.title;meta.fitschar