2 WFPC2 photometry

The galaxy images were obtained with the Wide Field and Planetary Camera (WFPC2) aboard the Hubble Space Telescope (HST) between July 23, 1999 and June 20, 2001 as part of our HST snapshot survey (proposals GO 8192, 8601) of nearby galaxy candidates (Seitzer et al. 1999). Each galaxy was observed in the F606W and F814W filters (one 600 s exposure in each filter). Digital Sky Survey images of the galaxies are shown in Fig. 1 with the HST WFPC2 footprints superimposed. Small galaxies were usually centered on the WF3 chip. For some bright objects the WFPC2 position was shifted towards the galaxy periphery to decrease stellar crowding. The WFPC2 images of the galaxies are presented in the upper panels of Fig. 2, where both filters are combined. The compass in each field indicates the North and East directions.

For photometric measurements we used the HSTphot stellar photometry package developed by Dolphin (2000a). The package has been optimized for the undersampled conditions present in the WFPC2 to work in crowded fields. After removing cosmic rays, simultaneous photometry was performed on the F606W and F814W frames using multiphot task. The resulting instrumental magnitudes were measured with an aperture radius of $0\hbox{$.\!\!^{\prime\prime}$ }5$ and corrected for charge-transfer inefficiency. Then they were converted to standard V and I magnitudes using the relations (11) and (12) of Dolphin (2000b). These calibration equations are analogous to equations of Holtzman et al. (1995), but incorporate the pixel area corrections. Additionally, stars with a signal-to-noise ratio S/N < 3, ${\mid \chi \mid} >2.0$, or $\mid$ sharpness ${\mid} >0.4$ in either exposure were eliminated from the final photometry list. The uncertainty of the photometric zero point is estimated to be within $0\hbox{$.\!\!^{\rm m}$ }05$(Dolphin 2000b).