Alaknanda: A Massive Grand-design Spiral Galaxy from the Universe's Infancy

by Ms Rashi Jain (NCRA)

Friday 27 Feb 2026, 14:30 → 15:30 Asia/Kolkata

A 304 and on Zoom

The James Webb Space Telescope (JWST) has challenged our understanding of galaxy formation and evolution due to its unprecedented sensitivity and resolution in near-infrared allowing us to access the optical rest frame at redshifts even greater than 3 for the first time. JWST has uncovered a vast population of well formed disk galaxies and its resolution allows us to see the faint features of distant galaxies in great detail. In this talk, I will talk about our discovery of “Alaknanda”, a rare, large and massive grand design spiral galaxy at the redshift of z ~ 4 which is just 1.5 billion years after the Big Bang. Spiral galaxies are ubiquitous in our nearby universe and several theories have been developed to explain the origin of spiral structure in the disk galaxies. It is still not known when and how the spiral galaxies emerged in the early universe. 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 a spectral energy distribution (SED) modeling code BAGPIPES. I will also discuss our derived parametric and non parametric morphological properties of this galaxy using Galfit and Statmorph softwares which clearly show its disk dominated nature. I will highlight the importance of our discovery and how future observations will be helpful to understand the origin of spiral structure in this intriguing galaxy.