Variable faint optical sources discovered by comparing the POSS and SDSS catalogs

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dc.contributor.authorSesar, Branimir
dc.contributor.authorSvilkovic, Domjan
dc.contributor.authorIvezic, Zeljko
dc.contributor.authorLupton, Robert H.
dc.contributor.authorMunn, Jeffrey A.
dc.contributor.authorFinkbeiner, Douglas
dc.contributor.authorSteinhardt, William
dc.contributor.authorSiverd, Rob
dc.contributor.authorJohnston, David E.
dc.contributor.authorKnapp, Gillian R.
dc.contributor.authorGunn, James E.
dc.contributor.authorRockosi, Constance M.
dc.contributor.authorSchlegel, David
dc.contributor.authorVanden Berk, Daniel E.
dc.contributor.authorHall, Pat
dc.contributor.authorSchneider, Donald P.
dc.contributor.authorBrunner, Robert J.
dc.date.accessioned2025-01-21T01:06:09Z
dc.date.available2025-01-21T01:06:09Z
dc.date.issued2006
dc.description.abstractWe present a study of variable faint optical sources discovered by comparing the Sloan Digital Sky Survey (SDSS) and the Palomar Observatory Sky Survey (POSS) catalogs. We use SDSS measurements to photometrically recalibrate several publicly available POSS catalogs (USNO-A2.0, USNO-B1.0, DPOSS [the Digitized Second Palomar Observatory Sky Survey], and GSC2.2 [the Guide Star Catalog 2.2]). A piecewise recalibration of the POSS data in 100 arcmin(2) patches (one SDSS field) generally results in an improvement of photometric accuracy (rms) by nearly a factor of 2, compared to the original data. In addition to the smaller core width of the error distribution, the tails of the distribution become much steeper after the recalibration. These improvements are mostly due to the very dense grid of calibration stars provided by SDSS, which rectifies the intrinsic inhomogeneities of Schmidt plates. We find that the POSS I magnitudes can be improved to similar to 0.15 mag accuracy, and POSS II magnitudes to similar to 0.10 mag accuracy. The smallest final errors are obtained with the GSC2.2 catalog, for which they approach 0.07 mag at the bright end. We use the recalibrated catalogs for the similar to 3300 deg(2) of sky in the SDSS Data Release 2 to construct a catalog of similar to 60,000 sources that are variable on timescales of 10-50 yr, and make it publicly available. Using this catalog, we find that at least 1% of faint optical sources appear variable at the > 0.25 mag level, and that about 20% of the variable population are quasars, although they represent only 0.6% of all point sources in the adopted flux-limited sample (g < 19). A series of statistical tests based on the morphology of SDSS color-magnitude and color-color diagrams, as well as visual comparison of images and comparison with repeated SDSS observations, demonstrate the robustness of the selection methods: three out of four candidate variable sources are correctly recognized to vary. We also demonstrate that candidate RR Lyrae stars trace the same halo structures, such as the Sgr dwarf tidal stream, that were discovered using repeated SDSS observations. We utilize the POSS-SDSS selected candidates to constrain the halo structure in the parts of sky for which repeated SDSS observations do not exist. We quantify the distribution of variable sources in the SDSS color-color diagrams and the variability characteristics of quasars. The observed long-term quasar variability ( structure function) is smaller than predicted by the extrapolation of the power law measured for short timescales using repeated SDSS imaging (0.35 vs. 0.60 mag for SDSS-POSS I and 0.24 vs. 0.35 mag for SDSS-POSS II, rms). This turnover in structure function suggests that the characteristic timescale for quasar variability is on the order of 1 yr in the rest frame.
dc.fuente.origenWOS
dc.identifier.eissn1538-3881
dc.identifier.issn0004-6256
dc.identifier.urihttps://repositorio.uc.cl/handle/11534/96098
dc.identifier.wosidWOS:000238176400005
dc.issue.numero6
dc.language.isoen
dc.pagina.final2825
dc.pagina.inicio2801
dc.revistaAstronomical journal
dc.rightsacceso restringido
dc.subjectgalaxy : halo
dc.subjectgalaxy : stellar content
dc.subjectquasars : general
dc.subjectstars : variables : other
dc.titleVariable faint optical sources discovered by comparing the POSS and SDSS catalogs
dc.typeartículo
dc.volumen131
sipa.indexWOS
sipa.trazabilidadWOS;2025-01-12
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