What observational challenge requires precise de-projection when estimating the physical size of a galaxy observed at z=8?
Cosmological distance effects dependent on the assumed cosmological model ($ ext{ extLambda CDM}$)
Measuring the apparent size of a high-redshift galaxy provides only its angular size on the sky, not its true physical size at that early time. This conversion from apparent to physical size is complicated by the expansion history of the universe, which is parameterized by cosmological models, specifically the $ ext{ extLambda CDM}$ model. The measured size is fundamentally dependent on the assumed expansion rate and geometry encoded in that model. Therefore, improving the accuracy of size measurements for distant objects like a galaxy at z=8 not only refines our understanding of that galaxy but also provides critical data points that help constrain the fundamental parameters describing the universe's overall expansion history.
