J/MNRAS/300/665 J/MNRAS/300/665 HST VI Photometry of Six LMC Old Globular Clusters K A G Olsen P W Hodge M Mateo E W Olszewski R A Schommer N B Suntzeff A R Walker Mon. Not. R. Astron. Soc. 300 665 1998 1998MNRAS.300..665O Clusters, globular Magellanic Clouds Photometry The following tables contain the results of photometry performed on Hubble Space Telescope WFPC2 images of the Large Magellanic Cloud globular clusters NGC 1754, 1835, 1898, 1916, 2005, and 2019. The magnitudes reported here were measured from Planetary Camera F555W and F814W images using DoPHOT (Schechter, Mateo, & Saha 1993) and afterwards transformed to Johnson V/Kron-Cousins I using equation 9 of Holtzman et al. (1995b). We carried out photometry on both long (1500 sec combined in F555W, 1800 sec in F814W) and short (40 sec combined in F555W, 60 sec in F814W) exposures. Where the short exposure photometry produced smaller errors, we report those magnitudes in place of those measured from the long exposures. For each star, we give an integer identifier, its x and y pixel position as measured in the F555W PC image, its V and I magnitude, the photometric errors reported by DoPHOT, both the V and I DoPHOT object types (multiplied by 10 if the reported magnitude was measured in the short exposure frame), and a flag if the star was removed during our procedure for statistical field star subtraction. Summary of data reduction and assessment of photometric accuracy: Cosmic ray rejection, correction for the y-dependent CTE effect (Holtzman et al. 1995a), geometric distortion correction, and bad pixel flagging were applied to the images before performing photometry. For the photometry, we used version 2.5 of DoPHOT, modified by Eric Deutsch to handle floating-point images. We found that there were insufficient numbers of bright, isolated stars in the PC frames for producing aperture corrections. Aperture corrections as a function of position in the frame were instead derived using WFPC2 point spread functions kindly provided by Peter Stetson. As these artificially generated aperture corrections agree well with ones derived from isolated stars in the WF chips, we trust that they are reliable to better than 0.05 mag. In agreement with the report of Whitmore & Heyer (1997), we found an offset in mean magnitudes between the short- and long-exposure photometry. We corrected for this effect by adjusting the short-exposure magnitudes to match, on average, those of the long exposures. Finally, we merged the short- and long- exposure lists of photometry as described above and transformed the magnitudes from the WFPC2 system to Johnson V/Kron-Cousins I, applying the Holtzman et al. (1995b) zero points. Statistical field star subtraction was performed using color-magnitude diagrams of the field stars produced from the combined WF frames. Completeness and random and systematic errors in the photometry were extensively modelled through artificial star tests. Crowding causes the completeness to be a strong function of position in the frame, with detection being most difficult near the cluster centers. In addition, we found that crowding introduces systematic errors in the photometry, generally <0.05 mag, that depend on the V-I and V of the star. Fortunately, these errors are well-understood. However, unknown errors in the zero points may persist at the ~0.05 mag level.

HST NGC 175404 54 18.70-70 26 32.1 NGC 183505 05 06.44-69 24 14.5 NGC 189805 16 42.41-69 39 24.6 NGC 191605 19 -69 27 NGC 200505 30 10.36-69 45 09.0 NGC 201905 31 56.73-70 09 33.3

Star Star ID --- X X pixel position from F555W PC image pix Y Y pixel position from F555W PC image pix V V magnitude mag SigV Error in V magnitude (DoPHOT) mag I I magnitude mag SigI Error in I magnitude (DoPHOT) mag Vtyp DoPHOT object type for V measurement Where short exposure photometry was used, object type has been multiplied by 10. Explanation of DoPHOT object types is given by Schechter, Mateo, & Saha (1993) --- Ityp DoPHOT object type for I measurement --- Sub y Indicates that star was removed during statistical subtraction procedure --- Star Star ID --- X X pixel position from F555W PC image pix Y Y pixel position from F555W PC image pix V V magnitude mag SigV Error in V magnitude (DoPHOT) mag I I magnitude mag SigI Error in I magnitude (DoPHOT) mag Vtyp DoPHOT object type for V measurement Where short exposure photometry was used, object type has been multiplied by 10. Explanation of DoPHOT object types is given by Schechter, Mateo, & Saha (1993) --- Ityp DoPHOT object type for I measurement --- Sub y indicates that star was removed during statistical subtraction procedure --- Star Star ID --- X X pixel position from F555W PC image pix Y Y pixel position from F555W PC image pix V V magnitude mag SigV Error in V magnitude (DoPHOT) mag I I magnitude mag SigI Error in I magnitude (DoPHOT) mag Vtyp DoPHOT object type for V measurement Where short exposure photometry was used, object type has been multiplied by 10. Explanation of DoPHOT object types is given by Schechter, Mateo, & Saha (1993) --- Ityp DoPHOT object type for I measurement --- Sub y indicates that star was removed during statistical subtraction procedure --- Star Star ID --- X X pixel position from F555W PC image pix Y Y pixel position from F555W PC image pix V V magnitude mag SigV Error in V magnitude (DoPHOT) mag I I magnitude mag SigI Error in I magnitude (DoPHOT) mag Vtyp DoPHOT object type for V measurement Where short exposure photometry was used, object type has been multiplied by 10. Explanation of DoPHOT object types is given by Schechter, Mateo, & Saha (1993) --- Ityp DoPHOT object type for I measurement --- Star Star ID --- X X pixel position from F555W PC image pix Y Y pixel position from F555W PC image pix V V magnitude mag SigV Error in V magnitude (DoPHOT) mag I I magnitude mag SigI Error in I magnitude (DoPHOT) mag Vtyp DoPHOT object type for V measurement Where short exposure photometry was used, object type has been multiplied by 10. Explanation of DoPHOT object types is given by Schechter, Mateo, & Saha (1993) --- Ityp DoPHOT object type for I measurement --- Sub y indicates that star was removed during statistical subtraction procedure --- Star Star ID --- X X pixel position from F555W PC image pix Y Y pixel position from F555W PC image pix V V magnitude mag SigV Error in V magnitude (DoPHOT) mag I I magnitude mag SigI Error in I magnitude (DoPHOT) mag Vtyp DoPHOT object type for V measurement Where short exposure photometry was used, object type has been multiplied by 10. Explanation of DoPHOT object types is given by Schechter, Mateo, & Saha (1993) --- Ityp DoPHOT object type for I measurement --- Sub y indicates that star was removed during statistical subtraction procedure --- Knut Olsen NOAO and James E. Gass ADC/SSDOO 1998Dec30We thank Eric Deutsch for his modifications to DoPHOT which made it easier to use and Peter Stetson for providing us with his WFPC2 PSFs. This work was supported by STScI grant GO05916 to NBS. J_MNRAS_300_665.xml