J/MNRAS/308/233ivo://CDS.VizieR/J/MNRAS/308/233doi:10.26093/cds/vizier.73080233CDSMittaz J.P.D.Carrera F.J.Romero-Colmenero E.Mason K.O.Hasinger G.,McMahon R.Andernach H.Bower R.Burgos-Martin J.Gonzalez-serrano J.I.,Wonnacott D.2024-06-26T20:16:08Z2013-10-21T11:53:36ZCDS support team

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

cds-question@unistra.frx-ray-sourcesredshiftedWe present results of an extensive study of the X-ray spectral properties of sources detected in the RIXOS survey, which is a large, nearly complete sample of objects detected serendipitously in ROSAT PSPC fields down to a flux limit of 3x10^-14^erg/cm2/s (0.5-2keV). We show that for X-ray surveys containing sources with low count rate, such as RIXOS, spectral slopes estimated using simple hardness ratios in the ROSAT band can be biased. Instead, we analyse three-colour X-ray data using statistical techniques appropriate to the Poisson regime which remove the effects of this bias. We also show that the use of three-colour data enables some discrimination between thermal and non-thermal spectra. We have then applied this technique to the RIXOS survey to study the spectral properties of the sample. For the AGN we find an average energy index of 1.05+/-0.05, with no evidence for spectral evolution with redshift. Individual AGN are shown to have a range of properties, including soft X-ray excesses and intrinsic absorption. Narrow-emission-line galaxies (NLLGs) also seem to fit to a power-law spectrum, which may indicate a non-thermal origin for their X-ray emission. We infer that most of the clusters in the sample have a bremsstrahlung temperature >3keV, although some show evidence for a cooling flow. The stars deviate strongly from a power-law model but fit to a thermal model. Finally, we have analysed the whole RIXOS sample (extending the flux cut-off to the sensitivity threshold of each individual observation) containing 1762 sources to study the relationship between spectral slope and flux. We find that the mean spectral slope of the sources hardens at lower fluxes, in agreement with results from other samples. However, a study of the individual sources demonstrates that the majority have relatively soft spectra even at faint flux levels, and the hardening of the mean is caused by the appearance of a population of very hard sources at the lowest fluxes. This has implications for the nature of the soft X-ray background.1999MNRAS.308..233Mhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/MNRAS/308/233CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/MNRAS/311/456 : RIXOS source catalogue (Mason+, 2000)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/MNRAS/308/233https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/MNRAS/308/233http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/MNRAS/308/233https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/MNRAS/308/233https://vizier.iucaa.in/viz-bin/votable?-source=J/MNRAS/308/233http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/MNRAS/308/233GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/MNRAS/308/233/table2 (Table of X-ray data for the RIXOS sample)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/308/233/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/308/233/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/308/233/table2?GETtext/xml+votable180.050000true217.04870833.3358890.0055555555555555566/551 556-557 4303 4321 4324-4326 4403 4409 4444 4831 5063 5069 5074 5080 5102-5103 5429 5671 5689 5804 5806 5855 5918 5922 5928 5975 5981 5989 6026 6038 6048 6050-6051 6056-6057 6059 6449 6452 6464-6465 6532 7246 7389 7391 7424 7426-7427 7642 7664 7741 7777 7780 7784 7896 7959 8687 8845 8906 9146-9147 9457-9459 10037 10039 10163 10169 10386-10387 10422 10512 10691 10877 10879 11029 11048 11050 11100-11101 11203 11206 11430 11668 11723 11745 11761 11763-11764 11766 12111 12122 12133 16058-16059 18190 18195 18198 18212 19566-19567 19970 19975 19981 20178 22658-22659 22690 22697 23123 23134 23223 25584-25585 26561 26563 27127 27132-27133 27349 27383 27514 27552 27554 28060 28062 28184 28353 28356 28358 28471 28492 28494 28510 28517 28519 28529 28532 28559 28581https://cdsarc.cds.unistra.fr/viz-bin/moc/J/MNRAS/308/233?format=asciiX-rayOpticaldefaultJ/MNRAS/308/233/table2Table of X-ray data for the RIXOS samplerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintFID[110/305] Field identification number (1)meta.id;obs.fieldintSRCSource identification number in the field (1)meta.id;obs.fieldintNHHydrogen column density1e+20cm**-2phys.columnDensityfloatObsObservation datetime.epoch;obsnullableExpExposure time of the field in ks.kstime.duration;obs.exposurefloatRad[0.3/0.9] Extraction radius for the source countsarcminphys.angSizefloatFx0Original flux (0.5-2keV), assuming an absorbed power law of slope 1 (in units of (10^-14^erg/cm^2^/s)1e-17W.m**-2phot.flux;em.X-rayfloatC1Extracted total counts in band S1 (2)ctphot.count;em.X-rayintC2Extracted total counts in band H1 (2)ctphot.count;em.X-rayintC3Extracted total counts in band H2 (2)ctphot.count;em.X-rayintB1Estimated background counts within the extraction circle for band S1 (2)ctinstr.backgroundfloatB2Estimated background counts within the extraction circle for band H1 (2)ctinstr.backgroundfloatB3Estimated background counts within the extraction circle for band H2 (2)ctinstr.backgroundfloatalphaMarginalized power-law slope {alpha}_1D_spect.indexfloatE_alphaError in alpha (upper limit)stat.error;stat.maxfloate_alphaError in alpha (lower limit)stat.error;pos.eq.rafloatNorm2Normalization of the best fit N_2D_ (in units of 10^-5^photon/keV/cm^2^/s)0.1keV**-1.m**-2.s**-1phot.flux;em.X-rayfloatalpha2Best-fitting slope {alpha}_2D_spect.indexfloatFx2Flux (0.5-2keV) determined from the best-fitting data (2D) (10^-14^erg/cm^2^/s)1e-17W.m**-2phot.flux;em.X-rayfloate_Fx2rms uncertainty on Fx21e-17W.m**-2stat.errorfloatTypeObject type (3)src.classcharu_TypeUncertainty flag on Typemeta.notecharz? Redshift (if applicable)src.redshiftfloatnullableu_zUncertainty flag on zmeta.code.error;src.redshiftcharSimbadSimbad column added by the CDSmeta.ref.urlchar_RAPosition, from RIXOS catalogue (Mason et al. 2000, Cat. J/MNRAS/311/456) (right ascension part)degpos.eq.ra;meta.main_DEPosition, from RIXOS catalogue (Mason et al. 2000, Cat. J/MNRAS/311/456) (declination part)degpos.eq.dec;meta.main