Cosmic Origins
Searching for answers about our universe and its origins

Galaxies Science Interest Group
(Galaxies SIG)

Galaxies SIG Events

How Habitable Worlds Observatory Can Definitively Constrain the 3D Geometry of High-Redshift Milky Way Progenitors

24 January 2024, 1:00pm ET
Viraj Pandya

There is now strong evidence from both NASA's HST and JWST that the majority of high-redshift dwarf galaxies (including Milky Way progenitors) cannot be axisymmetric (circular) disks or spheroids as commonly assumed. Instead, galaxies may start out intrinsically flattened in two dimensions like cigars (prolate ellipsoids) or surfboards (unusually oval, triaxial disks). However, current facilities are unable to make the "smoking gun" measurement needed to confirm this striking finding: constraining the orbits of the stars. It is imperative that we definitively constrain the 3D geometry of high-redshift (z > 2) Milky Way progenitors because it has major astrophysical implications for the origin of our own Galaxy as well as cosmological implications about the nature of dark matter. NASA's Roman mission and the upcoming 30m class telescopes will contribute but not fully address this problem. In this talk, I will make a fresh science case for the Habitable Worlds Observatory (HWO) that helps answer one of NASA's key questions concerning our Cosmic Origins: How Did We Get Here? In particular, I will stress the need for a multi-object spectrograph in space with both high spatial (≤ 0.03") and spectral (R ~10,000) resolution. Such a spectrograph will be required to detect the stellar continuum and resolve absorption lines in the spectra of these incredibly distant, small, elongated and faint early galaxies.

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