J/A+A/676/A37ivo://CDS.VizieR/J/A+A/676/A37doi:10.26093/cds/vizier.36760037CDSKutkin A.M.Oosterloo T.A.Morganti R.Offringa A.R.Adams E.A.K.,Adebahr B.Denes H.Hess K.M.van der Hulst J.M.de Blok W.J.G.,Bozkurt A.van Cappellen W.A.Gunst A.W.Holties H.A.van Leeuwen J.,Loose G.M.Oostrum L.C.Vohl D.Wijnholds S.J.Ziemke J.2024-11-28T20:04:50Z2023-08-04T06:19:12ZCDS support team

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

cds-question@unistra.frsurveysradio-sourcesWe present a new image of a 26.5 square degree region in the Bootes constellation obtained at 1.4GHz using the Aperture Tile in Focus (Apertif) system on the Westerbork Synthesis Radio Telescope. We use a newly developed processing pipeline which includes direction-dependent self-calibration which provides a significant improvement of the quality of the images compared to those released as part of the Apertif first data release. For the Bootes region, we mosaic 187 Apertif images and extract a source catalog. The mosaic image has an angular resolution of 27x11.5 arcsec and a median background noise of 40uJy/beam. The catalog has 8994 sources and is complete down to the 0.3mJy level. We combine the Apertif image with LOFAR images of the Bootes field at 54 and 150MHz to study spectral properties of the sources. We find a spectral flattening towards low flux density sources. Using the spectral index limits from Apertif non-detections we derive that up to 9% of the sources have ultra-steep spectra with a slope steeper than -1.2. Steepening of the spectral index with increasing redshift is also seen in the data showing a different dependency for the low-frequency spectral index and the high frequency one. This can be explained by a population of sources having concave radio spectra with a turnover frequency around the LOFAR band. Additionally, we discuss cases of individual extended sources with an interesting resolved spectral structure. With the improved pipeline, we aim to continue processing data from the Apertif wide-area surveys and release the improved 1.4GHz images of several famous fields.2023A&A...676A..37Khttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/676/A37CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/A+A/655/A40 : LoLSS-Deep Bootes 54MHz catalog (Williams+, 2021)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/676/A37https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/676/A37http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/676/A37https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/676/A37https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/676/A37http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/676/A37GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/676/A37/table1 (Apertif source catalog)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/676/A37/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/676/A37/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/676/A37/table1?GETtext/xml+votable180.050000true214.563183929412834.74601375527790.005555555555555556Cone search capability for table J/A+A/676/A37/table3 (Spectral indices of the sources)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/676/A37/table3?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/676/A37/table3?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/676/A37/table3?GETtext/xml+votable180.050000true214.8280334.868560.0055555555555555565/2285-2287 2298 2628-2630 6/9133 9135 9138-9139 9186 10501 10503 10509 10524-10526 10560-10562 105683.5780776607782883e-26 9.276497240453405e-25https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/676/A37?format=asciiRadiodefaultJ/A+A/676/A37/table1Apertif source catalogrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameSource name (Name)meta.id;meta.maincharRAICRSRight ascension (ICRS, J2000) (RA)degpos.eq.ra;meta.maine_RAICRSRight ascension error (E_RA)arcsecstat.error;pos.eq.radoubleDEICRSDeclination (ICRS, J2000) (DEC)degpos.eq.dec;meta.maine_DEICRSDeclination error (E_DEC)arcsecstat.error;pos.eq.decdoubleFtotTotal flux density at 1.4GHz (Total_flux)mJyphot.flux.density;em.radio.750-1500MHzdoublee_FtotTotal flux density at 1.4GHz error (E_Total_flux)mJystat.errordoubleFpeakPeak flux density 1.4GHz (Peak_flux)mJy/beamphot.flux.density;em.radio.750-1500MHzdoublee_FpeakPeak flux density 1.4GHz error (E_Peak_flux)mJy/beamstat.errordoubleDCMajDeconvolved major source size (DC_Maj)arcsecphys.angSizedoublee_DCMajDeconvolved major source size error (E_DC_Maj)arcsecstat.errordoubleDCMinDeconvolved minor source size (DC_Min)arcsecphys.angSizedoublee_DCMinDeconvolved minor source size error (E_DC_Min)arcsecstat.errordoubleDCPA[-90/90]? Deconvolved position angle of the source (DC_PA) (1)degpos.posAngdoublenullablee_DCPA? Deconvolved position angle error (E_DC_PA)degstat.errordoublenullableIslrmsLocal background noise RMS (Isl_rms)uJy/beaminstr.background;pos.lsr;pos.lgdoubleSCodeSource type as classified by PyBDSF (S_Code) (2)meta.codecharJ/A+A/676/A37/table3Spectral indices of the sourcesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAdeg? Apertif Right ascension (ICRS, J2000) (RA_apt)degpos.eq.ranullableDEdeg? Apertif Declination (ICRS, J2000) (DEC_apt)degpos.eq.decnullableFtot? Apertif total flux density 1.4GHz (Total_flux_apt)mJyphot.flux.density;em.radio.750-1500MHzfloatnullableSIlow? Spectral index between 54 and 150MHz (SI_low)spect.indexfloatnullablee_SIlow? Error of the spectral index between 54 and 150MHz (E_SI_low)stat.errorfloatnullablezbestHBA? Redshift estimate from Lofar value-added catalog (zbest_hba)src.redshift;pos.heliocentricdoublenullable_RARight Ascension (J2000) from SIMBAD (not part of the original data)degpos.eq.ra;meta.mainindexedRAHdeg? LOFAR HBA Right ascension (ICRS, J2000) (RA_hba)degpos.eq.ranullableDEHdeg? LOFAR HBA Declination (ICRS, J2000) (DEC_hba)degpos.eq.decnullableFtotHBA? LOFAR HBA total flux density at 150MHz (Total_flux_hba)mJyphot.flux.density;em.radio.100-200MHzdoublenullableRALdeg? LOFAR LBA Right ascension (ICRS, J2000) (RA_lba)degpos.eq.ranullableDELdeg? LOFAR LBA Declination (ICRS, J2000) (DEC_lba)degpos.eq.decnullableFtotLBA? LOFAR LBA total flux density at 54MHz (Total_flux_lba)mJyphot.flux.density;em.radio.20-100MHzdoublenullablel_SIhighLimit flag on SIhighmeta.code.errorcharSIhigh? Spectral index between 150 and 1400MHz (SI_high)spect.indexfloatnullablee_SIhigh? Error of the spectral index between 150 and 1400MHz (E_SI_high)stat.errorfloatnullablel_SIlowLimit flag on SIlowmeta.code.errorchar_DEDeclination (J2000) from SIMBAD (not part of the original data)degpos.eq.dec;meta.mainindexed