GSPC-II Program

GOAL:

• extend GSPC-I photometry to B = V ˜ 20

• add R band to calibrate red second-epoch surveysHOW:

• take B,V,R CCD exposures centered at GSPC-I faintest star OR

• conveniently close to POSS-II centers (for POSS-II offset plates)

The Data

• Given the long time span of this survey project, data come from different telescopes as well as different CCD cameras

• Size of camera fields vary from ˜ 3.5 arc minutes to ˜20 arc minutes

• Pixel scale ranges from ˜ 0.35 arc seconds/pixel to ˜ 0.7 arc seconds/pixel

• When appropriate, both long and short exposures are acquired

• Pre-selected sets of standard stars from the Landolt catalog are observed each night

• Common fields are also regularly observed

Example of CCD frames taken at the 0.9m ESO Dutch

Crowded

poor

medium

Telescope Latitude(deg)

Size(m)

POSS-I POSS-II SERC-J TotalRuns

UsefulNights

Epoch Range

Kitt Peak +31.9 0.9 320 134 34 17 63 1990-1999Cerro Tololo -30 0.9 177 21 540 23 116 1989-2001ESO Dutch -29.2 0.9 - 6 528 14 103 1991-1998 Wise +30.6 1 226 - 2 24 36 1989-1991Mt. Hopkins +31.6 1.2 50 - 2 4 5 1994-1995Mt. Laguna +32.8 1 84 - 5 2 9 1990-1999 Lowell +35.2 1 10 - - 1 2 1990Mt. Megantic +45.4 1.6 6 - - 3 1 1990 McDonald +30.6 0.8 2 - 1 1 1 1990La Palma JKT +28.7 1 90 90 29 5 23 1998-2001

Telescope usage and number of GSPC-II sequences collected (as of October 2001)

• Target sequences are 1780 (1478 GSPC-I centers + 302 POSS-II new sequences)

• Current in-house catalog contains 1619 sequences, of which 776 in the north and 856 in the south

• data from one and a half runs performed in semester 01A still to be included in catalog

• two more runs of 7 nights each, one at the ING/JKT and one at the CTIO 0.9m, to be performed in November/December

Relevant Numbers

1794 GSPCII targets - 1679 observed - 115 still remain

Sky Coverage

Magnitude limit of current catalog sequences

Number of stars/sequence in current catalog

GSPC-II Reduction Pipeline

• Photometry carried out with pipeline software (ARLO, Casalegno 1998) developed under IRAF 2.10.4

• Astrometry done within ARLO - fit to DSS positions

• Catalog of all frame data is a flat ASCII file including photometric, astrometric and other relevant information about the original exposures

• IRAF tables including additional statistical information are generated along with the frame catalogs

• Object naming performed in IRAF/IDL (naming convention: S001-AAAA, S002-AAAB, etc…)

Photometric Accuracy

• Only fits to Landolt stars with rms better than 0.05 are accepted

•Aperture photometry is carried out with fixed radius (2.3FWHM or < 4.5”) therefore not reliable in crowded fields

• PSF photometry more stable, but need to be checked for systematic errors in case of bad choice of template stars for analytical PSF

• Zero-point errors of transformation to standard system is also critical because it induces a photometric error of comparable magnitude

Released Sequences

• 622 GSPC-II fields ( Bucciarelli, Garcia, Casalegno et al. 2001, A&A 368, 335), 744 northern and 444 southern fields

•data are from KPNO, CTIO and ESO, for a total of 153 observing nights

• Aperture photometry only

• selection criteria based on agreement between Aperture and PSF photometry:

Linear regression M(apt) - M(psf) = Z + k M(apt)

sequences for which |k| < 0.01 and rms < 0.3 mag were retained

Zero-point errors Cumulative Distributions

GSPC-I/GSPC-II Comparison

597 V objects rms 0.07 mag, mean 0.001 mag

380 B objects rms 0.06 mag, mean 0.003 mag

Comparison of 10 common fields CTIO/KPNO

Comparison of 47 common fields CTIO/ESO

Summary

• 95% of GSPC-II data secured and practically all reduced

• Spin-off of observing activity

• 622 photometric sequences made available to community

•QA of new set of sequences for second release in progress

• Plan to put images, along with photometric reduction files, on-line for easy retrieval