The stellar edge of NGC 1494 with LSST Data Preview 1

Galaxy size traces how galaxies grow and evolve, yet traditional metrics like the effective radius are biased metric as they mainly capture the concentration of light of a galaxy.

A more accurate size proxy is the stellar edge: the outermost region of in situ star formation, shaped by gas density thresholds. Thanks to the depth of LSST Data Preview 1, we can now move beyond 1D profiles to 2D spatial analyses previously unattainable. We present an innovative way of processing DP1 raw data tailored to recover low surface brightness features, avoiding over subtraction of standard coadds. Applying it to multi-band ComCam data of NGC 1494, we detect a clear stellar edge at ~13 kpc, where the stellar mass surface density drops to ~1 M⊙/pc², which is consistent with theoretical thresholds for in situ star formation. This approach reveals structural 2D asymmetries at the stellar edge of NGC1494 and demonstrates the power of LSST to probe galaxy sizes in the era of wide-deep surveys.