ODIN: Comparison of Source Extractor and Tractor Source Detection for Lyman Alpha Emitting Galaxy Selection at z=3.1

Lyman Alpha Emitting galaxies (LAEs) are young, actively star-forming galaxies identified by their strong Lyman-alpha emission at a rest-frame wavelength of 121.6 nm, making them valuable tracers of galaxy evolution and the large-scale structure of the Universe. The One-hundred-deg^2 DECam Imaging in narrow-bands (ODIN) survey collects LAE samples during Cosmic Noon. Because LAE selection is based on photometric measurements derived from source-detection algorithms, the choice of detection method can directly affect the resulting LAE samples. We therefore compare two prominent source detection methods, Source Extractor (SE) and Tractor (Tr), to determine which is better suited for LAE selection in ODIN. We investigate differences between SE and Tr in the ODIN-COSMOS field, focusing on the z=3.1 LAE sample. We find that a significant fraction of Tr LAEs have low continuum flux measurements, increasing the inferred narrow-band excess and resulting in an LAE sample nearly twice as large as SE. However, LAEs detected by Tr but not SE exhibit equivalent width estimates indicative of potential contamination. We introduce an additional LAE selection criterion based on the expected Lyman-break behavior of LAEs at z~3 to reduce low-redshift contamination without requiring a significant detection of the break itself. Our results demonstrate that differences in source detection can significantly affect narrow-band LAE selection and motivate the use of SE photometry for ODIN LAE catalogs.