Difference image analysis (DIA) is an effective technique for obtaining photometry in crowded fields, relative to a chosen reference image. As yet, however, optimal reference image selection is an unsolved problem. We examine how this selection depends on the combination of seeing, background and detector pixel size. Our tests use a combination of simulated data and quality indicators from DIA of well-sampled optical data and under-sampled near-infrared data from the Optical Gravitational Lensing Experiment and VVV surveys, respectively. We search for a figure-of-merit (FoM) which could be used to select reference images for each survey. While we do not find a universally applicable FoM, survey-specific measures indicate that the effect of spatial under-sampling may require a change in strategy from the standard DIA approach, even though seeing remains the primary criterion. We find that background is not an important criterion for reference selection, at least for the dynamic range in the images we test. For our analysis of VVV data in particular, we find that spatial under-sampling is best handled by reversing the standard DIA procedure and convolving target images to a better-sampled (poor-seeing) reference image.
[1]
R. Lupton,et al.
A Method for Optimal Image Subtraction
,
1997,
astro-ph/9712287.
[2]
Austin B. Tomaney,et al.
Expanding the Realm of Microlensing Surveys with Difference Image Photometry
,
1996
.
[3]
A. Udalski,et al.
The Optical Gravitational Lensing Experiment. Final Reductions of the OGLE-III Data
,
2008,
0807.3884.
[4]
C. Alard.
Image subtraction using a space-varying kernel
,
2000
.
[5]
R. de Grijs,et al.
VISTA Variables in the Via Lactea (VVV): The public ESO near-IR variability survey of the Milky Way
,
2009,
0912.1056.
[6]
R. de Grijs,et al.
Vvv dr1: the first data release of the milky way bulge and southern plane from the near-infrared eso public survey vista variables in the via lactea
,
2011,
1111.5511.
[7]
Prasanth H. Nair,et al.
Astropy: A community Python package for astronomy
,
2013,
1307.6212.