Seminars on formation and evolution of the Galaxy Feb 12, 2002 The construction of the GSC2.2 Catalog Mario G. Lattanzi Osservatorio Astronomico di Torino

Seminars on formation and evolution of the Galaxy Feb 12, 2002 Basic Facts

Seminars on formation and evolution of the Galaxy Feb 12, 2002

GSC exported from the COMPASS Data Base Page = Federated Database = Database = Container = Class/Basic Object Region Database SourceIndex RegionCatalogContainers (for each plate defined area within region) ReferenceCatalogSource (for each reference catalog) Plate Database (for each plate) [ COMPASS Federated Database ] (for each of regions) PlateSource RegionInfoContainerPlateInfoContainer Approximately 1 Billion distinct objects found to date

Seminars on formation and evolution of the Galaxy Feb 12, 2002

Single-plate calibrations Astrometry: polynomial fits + residual maps (mask) to TYCHO2 stars (onto the ICRS reference system) [>Smart] Photometry: fits to a (B)VR CCD sequences to mag (GSPC2) transformed to natural bandpasses (J and F) [GSPC2>Bucciarelli] Classification: 30 ranked features + oblique decision trees + voting [>Smart]

Seminars on formation and evolution of the Galaxy Feb 12, 2002 Single-plate photometric calibrations

Seminars on formation and evolution of the Galaxy Feb 12, 2002 Intensity Sky background Intensity Density S aturation Photographic Density Sky background Stellar PSF

Seminars on formation and evolution of the Galaxy Feb 12, 2002 Intensity Sky background Intensity Density S aturation Photographic Density Integrated density above threshold Sky background GSC-II photometric parameter = Integrated photographic density above threshold (D sky + 3  sky ) Stellar PSF

Seminars on formation and evolution of the Galaxy Feb 12, 2002 Examples of saturated stellar PSF’s

Seminars on formation and evolution of the Galaxy Feb 12, 2002

Tycho stars GSPC2 stars

Seminars on formation and evolution of the Galaxy Feb 12, 2002

GSC2.2 Photographic photometry: bandpasses

Seminars on formation and evolution of the Galaxy Feb 12, 2002 GSC2.2 Photographic photometry: transformation to plate natural bands

Seminars on formation and evolution of the Galaxy Feb 12, 2002 Photographic photometry

Seminars on formation and evolution of the Galaxy Feb 12, 2002 The Catalog

Seminars on formation and evolution of the Galaxy Feb 12, 2002 Catalog extraction rules Only plates included in the GSC2.2 plate list considered (POSS II: 897 XJxxx XFxxx fields; 606 SERC-J, Sxxx, 216 SERC-EJ, Erxxx, and the red material, XSxxx and GRxxx, short exp., plates) Objects brighter than: J<19.5 OR F<18.5 Objects classed as defect on only one plate discarded Astrometry: export the position of that entry of a given object closest to the entry’s plate center (tolerance set to 0.25 deg). Brake ties by selecting entry with the most recent epoch Photometry: for each bandpass, take the value of the entry closest to the plate center

Seminars on formation and evolution of the Galaxy Feb 12, 2002 A view of the GSC2.2.01

Seminars on formation and evolution of the Galaxy Feb 12, 2002

The GSC2 Export Catalog: specifications Positions : <0.”5 absolute (average across one plate); better than 0.”2 relative (over a 0.5 deg field); 0.”15 rms deviation from ICRS (average over all plates) Magnitudes : precision to better than 0.2 mag for stars between 12 and 18 mag; accuracy <0.15 mag Classification : 95% accuracy within 2 mag from plate limit Completeness : V=18 minimum

Seminars on formation and evolution of the Galaxy Feb 12, 2002 Global Error Analysis

Seminars on formation and evolution of the Galaxy Feb 12, 2002 Astrometric errors External Comparisons to: UCAC1 Sky coverage: Southern hemisphere (-90 deg/-15 deg) Mag limit = 16.0, precision: better than 0.1 arcsec per coordinate) 2MASS Approaching all-sky coverage. Mag limit close to that of GSC2.2; position to 0.2 arcsec (per coordinate) Internal comparisons: on average relative error well within the 0.2 arcsec requirement.

Seminars on formation and evolution of the Galaxy Feb 12, 2002 Method: Statistical tests on the residuals (also called catalog-to- catalog differences)>>> d=(GSC external catalog). Ex.: a realization of the statistic d could be declination differences >> {d i = DEC i,gsc2 - DEC i,ext.cat. } The hypothesis put to test is that the residuals follow (within the chosen confidence level) the expected distribution: if the values from the two catalogs are Gaussian distributed >> d is also Gaussian distributed.

Seminars on formation and evolution of the Galaxy Feb 12, 2002 TWO TESTS: Chi-square, Kolmogorov-Smirnov Sample mean and variance are computed before the application of the tests. Outliers are eliminated from the sample to avoid biased values. Chi-square : need to group data to form histogram >> depends on number of bins. Chi-sq statistic

Seminars on formation and evolution of the Galaxy Feb 12, 2002 where n i is the number of differences in bin i-th, and the integral is evaluated using the error function.

Seminars on formation and evolution of the Galaxy Feb 12, 2002 K-S Test : do not need to group data (> reliable even with small samples) K-S statistic where and

Seminars on formation and evolution of the Galaxy Feb 12, 2002 Confidence levels set to 95% for both tests: from the distributions of the Chi-square and K-S statistics we calculate the quantiles (the values) for which the probabilities of the two statistics to be above those values are Finally, if the values of  2 and D n calculated from the samples are smaller than the quantiles the tests are satisfied with the 95% confidence level.

Seminars on formation and evolution of the Galaxy Feb 12, 2002 Astrometric Error (external): UCAC1

Seminars on formation and evolution of the Galaxy Feb 12, 2002 Astrometric Error (external): UCAC1, Chi 2 and K-S tests (Large sample, no mag and no plate-based selection) Both tests fail!….But,…..

Seminars on formation and evolution of the Galaxy Feb 12, 2002 Astrometric Error (external): UCAC1, Chi 2 and K-S tests (Selected sample, mag range , no plate-based selection) K-S tests passed, and Chi 2 also well behaved!!

Seminars on formation and evolution of the Galaxy Feb 12, 2002 Astrometric Error (external): 2MASS

Seminars on formation and evolution of the Galaxy Feb 12, 2002 Astrometric Error (external): 2MASS, Chi 2 and K-S tests (Large sample, no mag and no plate-based selection)

Seminars on formation and evolution of the Galaxy Feb 12, 2002 Astrometric Error (external): Conclusions Overall, the residuals appear well behaved, although simple statistical tests fail. As expected, this indicates the presence of magnitude and plate-based effects. Indeed, the same tests are consistently passed when limited to small magnitude bins or residuals from the same plate. This, in turn, is further proof that the single plate calibrations do obey gaussian statistics.

Seminars on formation and evolution of the Galaxy Feb 12, 2002 Photometric Errors Internal Tests :  J,  F plate-to-plate, J-F=const Semi-internal tests:  J,  F GSC2 vs. GSCPC2 External tests: against photometric catalogs (M67, DMS, EIS, etc.) Comparisons against starcounts from Galaxy models

Seminars on formation and evolution of the Galaxy Feb 12, 2002 Photometric Errors: internal test Residuals: J XJ443 - J XJ444 vs. J (red crosses)

Seminars on formation and evolution of the Galaxy Feb 12, 2002 Internal photometric errors: plate-to-plate comparison statistics RMS(  m)=0.27 /  2 mag from the analysis of stellar objects from 67 GSC-II (CRA) plates by Pannunzio, Morbidelli et al. (2001, OATo Rept. 57/01). This is an upper limit for GSC 2.2 because it is based on all stars down to the plate limits.

Seminars on formation and evolution of the Galaxy Feb 12, 2002 Photometric Errors - Semi-Internal Test: GSC2.2 vs. GSPC2 GSCP2 vs. GSC2.2:  >0°, b>30° (low crowding) GSCP2 vs. GSC2.2:  >0°, -15 ° <b<+15° (galactic plane) (Spagna)

Seminars on formation and evolution of the Galaxy Feb 12, 2002 Photometric Errors - Semi-Internal Test: GSC2.2 vs. GSPC2 GSCP2 vs. GSC2.2 (  >0° b>30° ) - Stellar objects only

Seminars on formation and evolution of the Galaxy Feb 12, 2002 Photometry. External Test: M67 (l=216 °, b=+32 ° ) CCD data (0.5° x 0.5°) from Montgomery et al. (1993, AJ, 106, 181) All objects  J  = RMS=0.11  F  = RMS=0.13 Stars only  J  = RMS=0.10  F  = 0.00 RMS=0.10

Seminars on formation and evolution of the Galaxy Feb 12, 2002 External Test: GSC2.2 vs. DMS CCD data (0.83 sq-deg in six fields) from DMS (Deep Multicolor Survey; Osmer et al, 1998, ApJS, 119, 189) Stellar objects All objects  J  = RMS=0.10  F  = RMS=0.17 Stars only  J  = RMS=0.09  F  = 0.02 RMS=0.15 (Spagna)

Seminars on formation and evolution of the Galaxy Feb 12, 2002 Classification Errors

Seminars on formation and evolution of the Galaxy Feb 12, 2002 Classification Errors

Seminars on formation and evolution of the Galaxy Feb 12, 2002 Classification Errors

Seminars on formation and evolution of the Galaxy Feb 12, 2002 Classification Errors

Seminars on formation and evolution of the Galaxy Feb 12, 2002 Classification Errors

Seminars on formation and evolution of the Galaxy Feb 12, 2002 Catalog Completeness (1/4) All stars, J mag J compl = 17.3 Toward the galactic center (l,b~0.5 deg)

Seminars on formation and evolution of the Galaxy Feb 12, 2002 Catalog Completeness galactic center (l,b~0.5 deg) All stars, F mag F compl = 15.8

Seminars on formation and evolution of the Galaxy Feb 12, 2002 Catalog Completeness galactic center (l,b~0.5 deg) All obj.s, J mag J compl = 18.4

Seminars on formation and evolution of the Galaxy Feb 12, 2002 Catalog Completeness galactic center (l,b~0.5 deg) All obj.s, F mag F compl = 18.0

Seminars on formation and evolution of the Galaxy Feb 12, 2002 Comparison to SDSS

Seminars on formation and evolution of the Galaxy Feb 12, 2002 Contributions for this presentation from: B. Bucciarelli R. Drimmel R. Smart A. Spagna

Seminars on formation and evolution of the Galaxy Feb 12, 2002 THE END

Seminars on formation and evolution of the Galaxy Feb 12, 2002