We present our discovery of Alaknanda, a large (~10 kpc) grand design spiral galaxy at the redshift of z~4, one of the highest redshift spiral galaxies ever discovered with JWST. Using the data from the UNCOVER program, we detect this galaxy in a total of 21 JWST and HST broad and medium band filters. This enables us to derive parameters such as mass and star formation rate robustly via stellar population synthesis using the code BAGPIPES. We detect flux boosting in the F250M and F335M medium band filters due to the presence of emission line complexes [OIII]+Hβ and Hɑ+[NII] emission line complexes which is consistent with our photometric redshift. We perform bulge disk decomposition using GALFIT which allows us to see two symmetric spiral arms in the residual. We further confirm the disk dominated nature of this galaxy with non parametric morphological measurements using Statmorph.This discovery challenges the existing models of disk/spiral galaxy formation in the early universe.

Presented in the last Galaxies session (after coffee break) on 16th September 2025.