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PRODID:UW-Madison-Physics-Events
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SEQUENCE:0
UID:UW-Physics-Event-9074
DTSTART:20250129T160000Z
DTEND:20250129T180000Z
DTSTAMP:20260413T150553Z
LAST-MODIFIED:20250123T222855Z
LOCATION:B343 Sterling
SUMMARY:Interpolation in Cell-Based Coaddition Images and Impacts on S
 hear Measurements\, Preliminary Exam\, Miranda Gorsuch\, Physics PhD G
 raduate Student
DESCRIPTION:Weak gravitational lensing encodes information of the stru
 cture of matter as well as the expansion history of the observable uni
 verse. However\, the weak lensing signal is small\, and requires measu
 rements of the signal across a large sample of galaxies. In the era of
  the Vera C. Rubin Observatory and the Legacy Survey of Space and Time
 \, billions of shape measurements will be detected across 18\,000 squa
 re degrees. A galaxy sample of this scale affirms that we are in the e
 ra of precision cosmology\; now considerable care must be taken to acc
 urately measure the shapes of galaxies in order to preserve the weak l
 ensing signal against systematics. Part of the work for maintaining ac
 curate shape measurements includes a recent method for stacking images
  - or coadding - referred to as cell-based coadds. This coaddition sch
 eme better preserves the shape measurements of galaxies by neglecting 
 input images that do not fully cover the region of the coadd\, which i
 f included introduce systematic biases in the shape measurements. I wi
 ll present my current work that focuses on interpolated pixels within 
 cell-based coadd images. Allowing images with a large fraction of mask
 ed pixels into the final coadd may impact shear measurements\; on the 
 other hand\, discarding too many input images may affect final coadd d
 epth and object detection. I have developed a pipeline to determine th
 e average fraction of input images lost due to the images going over t
 he allowed fraction of masked pixels. The next stage of this project w
 ill use the metadetection algorithm to measure the shear response on s
 imulated image data. The purpose of this stage is to characterize how 
 shear measurements are impacted by changes in the maximum mask fractio
 n of input images. Finally\, an object detection stage will be done to
  understand impacts in the variation of coadded image depths.
URL:https://www.physics.wisc.edu/events/?id=9074
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