Princeton University Thunch Talk

I will present surprising observational results on the 3D shapes and large-scale alignments of high-redshift galaxies from JWST. I will show that there are many more linear, elongated dwarf galaxies than there are round, circular dwarf galaxies seen in projection at high redshift (z>1). This puzzle was first hinted at with HST ~30 years ago but has defied a clear explanation since. After ruling out a detection bias against faint, face-on disks with JWST, I will explore a variety of solutions. One reasonable interpretation is that, unlike in the local Universe, the majority of high-redshift dwarf galaxies (including Milky Way progenitors at z>2) may be significantly flattened along two axes like prolate (cigar-shaped) or triaxial (surfboard-shaped) ellipsoids. This preferential elongation is naturally expected from the tidal field of the filamentary cosmic web, in which case we should also see strong intrinsic alignments. I will present evidence for such alignments when averaging over the orientations of background galaxies in a "blank" JWST deep field. We cannot yet rule out a lensing origin for the alignments and I will discuss implications for upcoming weak lensing searches with Roman and Euclid. If confirmed, this new dominant class of early elongated protogalaxies may hold unique clues about the origin of the Hubble Sequence and the emergence of early cosmic web filaments. Finally, I will also summarize how this seemingly niche puzzle bridges together many different areas of astrophysics and cosmology (including Galactic archaeology, dynamics and dark matter phenomenology), unlocks fresh science cases for the upcoming era of Extremely Large Telescopes, and requires a mixture of theory, observations, statistics and AI/ML to fully understand.