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Galaxies SIG Seminar

Galaxies Science Interest Group

DATE

Jan 24, 2024

TIME

1:00pm

COMMUNITY

Galaxies SIG

TYPE

Seminar

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

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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An illustration of Sun-like star HD 181327 and its surrounding debris disk. The star is at top right. It is surrounded by a far larger debris disk that forms an incomplete ellpitical path and is cut off at right. There’s a huge cavity between the star and the disk. The debris disk is shown in shades of light gray. Toward the top and left, there are finer, more discrete points in a range of sizes. The disk appears hazier and smokier at the bottom. The star is bright white at center, with a hazy blue region around it. The background of space is black. The label Artist's Concept appears at lower left.