J/AJ/149/32ivo://CDS.VizieR/J/AJ/149/32doi:10.26093/cds/vizier.51490032CDSMarvil J.Owen F.Eilek J.2017-06-30T05:48:01Z2015-04-22T15:01:54ZCDS support team

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

cds-question@unistra.frradio-galaxiesgalaxiescatalogsradio-continuum-emissionWe investigate the spectral shape of the total continuum radiation, between 74MHz and 5GHz (400-6cm in wavelength), for a large sample of bright galaxies. We take advantage of the overlapping survey coverage of the VLA Low-Frequency Sky Survey, the Westerbork Northern Sky Survey, the NRAO VLA Sky Survey, and the Green Bank 6cm Survey to achieve significantly better resolution, sensitivity, and sample size compared to prior efforts of this nature. For our sample of 250 bright galaxies we measure a mean spectral index, {alpha}, of -0.69 between 1.4 and 4.85GHz, -0.55 between 325MHz and 1.4GHz, and -0.45 between 74 and 325MHz, which amounts to a detection of curvature in the mean spectrum. The magnitude of this curvature is approximately {Delta}{alpha}=-0.2 per logarithmic frequency decade when fit with a generalized function having constant curvature. No trend in low-frequency spectral flattening versus galaxy inclination is evident in our data, suggesting that free-free absorption is not a satisfying explanation for the observed curvature. The ratio of thermal to non-thermal emission is estimated through two independent methods: (1) using the IRAS far-IR fluxes and (2) with the value of the total spectral index. Method (1) results in a distribution of 1.4GHz thermal fractions of 9%+/-3%, which is consistent with previous studies, while method (2) produces a mean 1.4GHz thermal fraction of 51% with dispersion 26%. The highly implausible values produced by method (2) indicate that the sum of typical power-law thermal and non-thermal components is not a viable model for the total spectral index between 325 and 1.4GHz. An investigation into relationships between spectral index, infrared-derived quantities, and additional source properties reveals that galaxies with high radio luminosity in our sample are found to have, on average, a flatter radio spectral index, and early types tend to have excess radio emission when compared to the radio-infrared ratio of later types. Early types also have radio emission that is more compact than later type galaxies, as compared to the optical size of the galaxy. Despite these differences, no relation between spectral index and galaxy type is detected.2015AJ....149...32Mhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/AJ/149/32CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toVIII/79 : The VLA Low-frequency Sky Survey at 74MHz (Cohen+ 2007)VIII/65 : 1.4GHz NRAO VLA Sky Survey (NVSS) (Condon+ 1998)VIII/62 : The Westerbork Northern Sky Survey (Leiden, 1998)VIII/40 : GB6 catalog of radio sources (Gregory+ 1996)VII/155 : Third Reference Cat. of Bright Galaxies (RC3) (de Vaucouleurs+ 1991)J/ApJ/554/803 : New VLA Sky Survey (NVSS) Cat of IRAS 2 Jy Galaxies (Yun+ 2001)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/AJ/149/32https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/AJ/149/32http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/AJ/149/32https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/AJ/149/32https://vizier.iucaa.in/viz-bin/votable?-source=J/AJ/149/32http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/AJ/149/32GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/AJ/149/32/galaxies (Survey measurements , far-infrared data , additional source properties , and spectral properties)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/AJ/149/32/galaxies?https://vizier.iucaa.in/viz-bin/conesearch/J/AJ/149/32/galaxies?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/AJ/149/32/galaxies?GETtext/xml+votable180.050000true10.51958336.8041670.0055555555555555566/975 1008 1013 1596 1680 1702 1707 2266 2269 2333 2347 2351 2356 2360 2362 2363 2372 2383 2387 2390 2412 2432 2484 2499 2504 2608 2610 2631 2687 2856 3078 3105 3389 3431 3438 3446 3862 5083 5091 5342 5423 5428 5429 5463 5469 5528 5558 5572 5582 5587 5589 5590 5594 5596 5610 5669 5793 5799 5818 5827 5903 5918 5966 5975 5976 5982 5987 5989 5995 6014 6034 6037 6042 6046 6047 6050 6093 6099 6101 6123 6360 6458 6560 6605 6781 6951 6968 6969 6977 6998 7037 7098 7132 7137 7157 7177 7214 7222 7225 7230 7231 7241 7385 7386 7424 7457 7498 7515 7550 7584 7604 7655 7659 7682 7683 7796 7822 7824 7869 7882 7896 7898 7923 7957 7975 7986 8004 8010 8064 9437 9464 9468 9591 9612 9639 9718 9791 9812 9829 9935 9946 10025 10095 10166 10213 10469 10471 10475 10511 10518 10519 10544 10553 10577 10586 10595 10627 10632 10637 10638 10650 10674 10705 10727 10739 10740 10781 10817 10878 10892 10912 10924 10927 10979 10986 10990 10991 11006 11010 11093 11132 11173 11180 11191 11232 11234 11246 11253 11257 11259 11314 11362 11372 11379 11392 11394 11435 11446 11453 11457 11726 11734 11791 11800 11832 11938 11939 11947 11965 11975 12005 12015 12018 13693 13706 13903 13907 13913 13925 13948 14777 14876 14993 15008 15061 15161 15260 15323 15915 15955 16050 16104 16120 28631 286514.903291545219051e-26 3.953759050367298e-21https://cdsarc.cds.unistra.fr/viz-bin/moc/J/AJ/149/32?format=asciiRadiodefaultJ/AJ/149/32/galaxiesSurvey measurements , far-infrared data , additional source properties , and spectral propertiesUGC[444/12883] UGC galaxy number (1)meta.id;meta.mainintONameOther source namemeta.idcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNVSS[7/3686] NVSS (1.4GHz) flux (2)mJyphot.fluxdoublee_NVSS[0.5/111] The 1{sigma} error in NVSS (2)mJystat.errordoublel_MAxis[<] Upper limit flag on MAxismeta.code.errorcharMAxisNVSS fitted (deconvolved) major axis (FWHM) of radio source (3)arcsecphys.angSize;em.radio;meta.modelledintl_mAxis[<] Upper limit flag on mAxismeta.code.errorcharmAxisNVSS fitted (deconvolved) minor axis (FWHM) of radio source (3)arcsecphys.angSize;em.radio;meta.modelledintPA[0/180] Position angle of the major axis (3)degpos.posAngintl_WENSS[<] Upper limit flag on WENSSmeta.code.errorcharWENSSWENSS flux (330MHz) (4)mJyphot.fluxinte_WENSS? The 1{sigma} error in WENSS (4)mJystat.errorintnullablel_VLSSr[<] Upper limit flag on VLSSrmeta.code.errorcharVLSSrVLSSr flux (74MHz) (5)mJyphot.fluxinte_VLSSr? The 1{sigma} error in VLSSr (5)mJystat.errorintnullablel_GB6[<] Upper limit flag on FGB6meta.code.errorcharGB6Green Bank 6cm (5GHz) Survey flux (6)mJyphot.flux.density;em.radio.3-6GHzinte_GB6? The 1{sigma} error in FGB6 (6)mJystat.errorintnullableF60? IRAS 60{mu}m flux S_60{mu}m_Jyphot.flux.density;em.IR.30-60umdoublenullableF100? IRAS 100{mu}m flux S_100{mu}m_Jyphot.flux.density;em.IR.60-100umdoublenullableFIR? Total far-infrared flux (7)1e-14W.m**-2phot.flux;em.IRdoublenullableF1.4? Free-free thermal radio flux at 1.4GHz IR_Sth,1.4_ (8)mJyphot.flux.density;em.radio.750-1500MHzdoublenullablel_f1.4[<]? Upper limit flag on f1.4meta.code.errorcharf1.4? Thermal fraction at 1.4GHz IR_fth,1.4_ (9)%arith.ratio;em.radio.750-1500MHzintnullableq? Log of the FIR/radio flux-ratio parameter (10)stat.param;arith.ratio;em.IRfloatnullableRAJ2000Hour of Right Ascension (J2000) (11)pos.eq.ra;meta.mainDEJ2000Degree of Declination (J2000) (11)pos.eq.dec;meta.mainb/a[0/1] Optical axial ratio (minor to major) (12)phys.angSize;arith.ratiofloatT[-5/99]? Numerical Hubble type (13)meta.note;src.morph.typeintnullablel_logSigma[>] Lower limit flag on logSigmameta.code.errorcharlogSigmaLog of radio surface brightness at 1.4GHz (log{Sigma}) (14)log(mJy.arcmin**-2)phot.mag.sb;em.radio.750-1500MHzfloatl_comp[<] Upper limit flag on compmeta.code.errorcharcompRadio compactness parameter (15)stat.paramfloatDist[20/162]? Hubble flow distance (16)Mpcpos.distanceintnullablel_a0[>] Lower limit flag on a0meta.code.errorchara0[-2.14/0.44]? Spectral index {alpha}_low_ between 74 and 325MHz (17)spect.index;em.radio.200-400MHzdoublenullablee_a0? The 1{sigma} uncertainty on a0 (17)stat.errordoublenullablel_a1[>] Lower limit flag on a1meta.code.errorchara1[-1.37/0.55] Spectral index {alpha}_mid_ between 325 and 1400MHz (18)spect.index;em.radio.750-1500MHzdoublee_a1? The 1{sigma} uncertainty on a1 (18)stat.errordoublenullablel_a2[<] Upper limit flag on a2meta.code.errorchara2[-1.67/0.79] Spectral index {alpha}_high_ between 1400 and 4850MHz (19)spect.index;em.radio.3-6GHzdoublee_a2? The 1{sigma} uncertainty on a2 (19)stat.errordoublenullableR[-7.2/23.7]? Ratio R_low_ of 74 to 325MHz flux (20)phot.flux;arith.ratio;em.radiodoublenullablee_R? The 1{sigma} uncertainty on RLow (20)stat.errordoublenullableRC3Display the data from the third reference catalog of bright galaxies (de Vaucouleurs et al. 1991, cat. VII/155)meta.ref.urlcharSimbadSimbad column added by the CDSmeta.ref.urlcharNEDSimbad column added by the CDSmeta.ref.urlchar