MGL/OATo 7th GSC2 Meeting, Barolo (I), 22 Oct 2001 The GSC2.2 Catalog: Global Properties Mario G. Lattanzi Osservatorio Astronomico di Torino

MGL/OATo 7th GSC2 Meeting, Barolo (I), 22 Oct 2001

The GSC2.2 Catalog: Global Properties

Mario G. Lattanzi

Osservatorio Astronomico di Torino


GSC2.2.01 exported from the COMPASS Data Base

Page = Federated Database

= Database

= Container

= Class/Basic Object

Region Database

SourceIndex

RegionCatalogContainers

(for each plate definedarea within region)

ReferenceCatalogSource (for each reference catalog)

Plate Database

(for each plate)

[ COMPASS Federated Database ]

(for each of 32768 regions)

PlateSource

RegionInfoContainer PlateInfoContainer

Approximately 1 Billion distinct objects found to date


Single-plate calibrations

•Astrometry: polynomial fits + residual maps (mask) to

TYCHO2 stars (onto the ICRS reference system)

•Photometry: fits to a (B)VR CCD sequences to 18-19 mag

(GSPC2) transformed to natural bandpasses (J and F)

•Classification: 30 ranked features + oblique decision trees

+ voting


GSC2.2 Photographic photometry: bandpasses


GSC2.2 Photographic photometry: transformation to plate natural bands

MGL/OATo 7th GSC2 Meeting, Barolo (I), 22 Oct 2001 Photographic photometry

Photometric system of GSC-II

Band Survey Emulsion+Filter Lambda_eff FWHM (Angstrom)J385 POSS-II J DEC>0 IIIaJ+GG385 4660 1095F610 POSS-II F > 0 IIIaF+RG610 6540 580I9 POSS-II N > 0 IV-N+RG9 8060 1100J395 SERC J DEC<0 IIIaJ+GG395 4635 1080F590 SES F < 0 IIIaF+OG590 6450 720I715 UKST IR <0 IV-N+RG715 8020 1170


Catalog extraction rules

•Only plates included in the GSC2.2 plate list considered (POSS II: 897 XJxxx + 897 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


A view of the GSC2.2.01


GSC 2.2.01 Global counts

Hemisphere N.ro of stars N.ro of ObjectsNorth (0 ) 66,646,991 152,259,610South (<0 ) 112,738,987 303,591,627Total 179,385,978 455,851,237

Galactic coordinates N.ro of ObjectsLow Latitudes (b<20 ) 411,061,869High latitudes (b20 ) 44,789,368Total 455,851,237

(A. Spagna)


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


Global Error Analysis

MGL/OATo 7th GSC2 Meeting, Barolo (I), 22 Oct 2001 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 (see last year’s meeting)

Method: Chi-square and K-S tests on the residuals (GSC2.2.01 - external catalog). The hypothesis put to test is that, with the values from the two catalogs assumed Gaussian distributed, the residuals are also Gaussian distributed.

MGL/OATo 7th GSC2 Meeting, Barolo (I), 22 Oct 2001 Astrometric Error (external): UCAC1

MGL/OATo 7th GSC2 Meeting, Barolo (I), 22 Oct 2001 Astrometric Error (external): UCAC1, Chi2 and K-S tests

(Large sample, no mag and no plate-based selection)

Both tests fail!….But,…..

MGL/OATo 7th GSC2 Meeting, Barolo (I), 22 Oct 2001 Astrometric Error (external): UCAC1 , Chi2 and K-S tests

(Selected sample, mag range 16-16.5, no plate-based selection)

K-S tests passed, and Chi2 also well behaved!!

MGL/OATo 7th GSC2 Meeting, Barolo (I), 22 Oct 2001 Astrometric Error (external): 2MASS

MGL/OATo 7th GSC2 Meeting, Barolo (I), 22 Oct 2001 Astrometric Error (external): 2MASS , Chi2 and K-S tests

(Large sample, no mag and no plate-based selection)


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.


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


Photometric Errors: internal test

Residuals: JXJ443 - JXJ444 vs. J (red crosses)

(Spagna)


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.

(Spagna)

MGL/OATo 7th GSC2 Meeting, Barolo (I), 22 Oct 2001 Photometric Errors - Semi-Internal Test: GSC2.2 vs. GSPC2

n.ro (red)objects

F(mag)

RMS[F](mag)

n.ro (blue)objects

J(mag)

RMS[J](mag)

Stars 8298 +0.002 0.089 7080 -0.035 0.099

Multiple-stars 451 -0.013 0.123 423 -0.023 0.166

Non-stars 1877 -0.262 0.275 1360 -0.403 0.394

All objects 9788 -0.018 0.114 8050 -0.020 0.123

n.ro (red)objects

F(mag)

RMS[F](mag)

n.ro (blue)objects

J(mag)

RMS[J](mag)

Stars 12874 +0.042 0.109 11869 +0.035 0.125

Multiple-stars 3495 +0.046 0.167 3323 +0.063 0.191

Non-stars 19926 -0.071 0.199 14119 -0.083 0.218

All objects 32365 -0.020 0.168 25692 -0.019 0.181

GSCP2 vs. GSC2.2: >0°, b>30° (low crowding)

GSCP2 vs. GSC2.2: >0°, -15 ° <b<+15° (galactic plane)(Spagna)

MGL/OATo 7th GSC2 Meeting, Barolo (I), 22 Oct 2001 Photometric Errors - Semi-Internal Test: GSC2.2 vs. GSPC2

GSCP2 vs. GSC2.2 (>0° b>30° ) - Stellar objects only

(Spagna)

MGL/OATo 7th GSC2 Meeting, Barolo (I), 22 Oct 2001 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 = -0.07 RMS=0.11

F = -0.01 RMS=0.13

Stars only

J = -0.06 RMS=0.10

F = 0.00 RMS=0.10

(Spagna)

MGL/OATo 7th GSC2 Meeting, Barolo (I), 22 Oct 2001 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 = -0.06 RMS=0.10

F = +0.01 RMS=0.17

Stars only

J = -0.05 RMS=0.09

F = 0.02 RMS=0.15

(Spagna)

MGL/OATo 7th GSC2 Meeting, Barolo (I), 22 Oct 2001 Classification Errors

(Smart)






Catalog Completeness (1/4)

All stars, J mag

Jcompl = 17.3

Toward the galactic center (l,b~0.5 deg)

(R. Drimmel)


Catalog Completeness

galactic center (l,b~0.5 deg)

All stars, F mag

Fcompl = 15.8

(R. Drimmel)




All obj.s, J mag

Jcompl = 18.4

(R. Drimmel)




All obj.s, F mag

Fcompl = 18.0

(R. Drimmel)


THE END

Documents

MGL/OATo 7th GSC2 Meeting, Barolo (I), 22 Oct 2001 The GSC2.2 Catalog: Global Properties Mario G. Lattanzi Osservatorio Astronomico di Torino