J/A+A/621/A139ivo://CDS.VizieR/J/A+A/621/A139doi:10.26093/cds/vizier.36210139CDSTisanic K.Smolcic V.Delhaize J.Novak M.Intema H.Delvecchio I.,Schinnerer E.Zamorani G.Bondi M.Vardoulaki E.2020-08-25T13:25:45Z2019-01-18T07:59:17ZCDS support team

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

cds-question@unistra.frradio-galaxiesradio-continuum-emissionWe construct the average radio spectral energy distribution (SED) of highly star-forming galaxies (HSFGs) up to z~4. Infrared and radio luminosities are bound by a tight correlation that is defined by the so-called q parameter. This infrared-radio correlation provides the basis for the use of radio luminosity as a star-formation tracer. Recent stacking and survival analysis studies find q to be decreasing with increasing redshift. It was pointed out that a possible cause of the redshift trend could be the computation of rest-frame radio luminosity via a single power-law assumption of the star-forming galaxies' (SFGs) SED. To test this, we constrained the shape of the radio SED of a sample of HSFGs. To achieve a broad rest-frame frequency range, we combined previously published Very Large Array observations of the COSMOS field at 1.4GHz and 3GHz with unpublished Giant Meterwave Radio Telescope (GMRT) observations at 325MHz and 610MHz by employing survival analysis to account for non-detections in the GMRT maps. We selected a sample of HSFGs in a broad redshift range (z{in}[0.3,4], SFR>=100M_{sun}_/yr) and constructed the average radio SED. By fitting a broken power-law, we find that the spectral index changes from {sigma}_1_=0.42+/-0.06 below a rest-frame frequency of 4.3GHz to {sigma}_2_=0.94+/-0.06 above 4.3GHz. Our results are in line with previous low-redshift studies of HSFGs (SFR>10M_{sun}_/yr) that show the SED of HSFGs to differ from the SED found for normal SFGs (SFR<10M_{sun}}/yr). The difference is mainly in a steeper spectrum around 10GHz, which could indicate a smaller fraction of thermal free-free emission. Finally, we also discuss the impact of applying this broken power-law SED in place of a simple power-law in K-corrections of HSFGs and a typical radio SED for normal SFGs drawn from the literature. We find that the shape of the radio SED is unlikely to be the root cause of the q-z trend in SFGs.2019A&A...621A.139Thttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/621/A139CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/ApJS/188/384 : The VLA-COSMOS survey. IV. (Schinnerer+, 2010)J/A+A/602/A1 : VLA-COSMOS 3 GHz Large Project (Smolcic+, 2017)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/621/A139https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/621/A139http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/621/A139https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/621/A139https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/621/A139http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/621/A139GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/621/A139/matched (Table of cross-matched fluxes)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/621/A139/matched?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/621/A139/matched?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/621/A139/matched?GETtext/xml+votable180.050000true150.60320832.53655560.0055555555555555565/6814 6/27245 272472.1534725313611987e-25 1.987820871092403e-24https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/621/A139?format=asciiRadiodefaultJ/A+A/621/A139/matchedTable of cross-matched fluxesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintCOSMOSVLA3VLA-COSMOS name of the source, JHHMMSS.ss+DDMMSS.smeta.id;meta.maincharF325MHz325MHz flux densityuJyphot.flux.density;em.radio.200-400MHzintl_F325MHz[Det Ulim] Detection or upper limit at 325MHzmeta.code.errorcharF610MHz610MHz flux densityuJyphot.flux.density;em.radio.400-750MHzintl_F610MHz[Det Ulim] Detection or upper limit at 610MHzmeta.code.errorcharF1.4GHz1.4GHz flux density (1)uJyphot.flux.density;em.radio.750-1500MHzintF3GHz3 GHz flux density (2)uJyphot.flux.density;em.radio.1500-3000MHzintSimbadSimbad column added by the CDSmeta.ref.urlchar_RAPositions from Name (right ascension part)degpos.eq.ra;meta.main_DEPositions from Name (declination part)degpos.eq.dec;meta.main