Events Daily

Tuesday, November 9, 2021

Unraveling The Milky Way’s Stellar Halo
Rohan Naidu, Harvard University
Event Type: Astro Seminar
Time: 2:00 PM - 3:15 PM
Location: Speaker: Zoom; Audience: 940 or Zoom
Abstract: The Milky Way has assimilated smaller systems throughout its history. Its outer reaches the stellar halo are a melting pot for stars that were born elsewhere, but now call the MW their home. Despite being scattered across the Galaxy, these immigrant stars retain memory of their common origin that may be accessed via their shared chemistry and 3D positions + 3D velocities. In this talk I will present results from the H3 Survey -- the first dedicated halo survey in the Gaia era 150+ nights on the 6.5m MMT, 150k+ spectra of distant stars. I will present a comprehensive anatomy of our Galaxy out to 50 kpc, charting debris from various known and newly discovered mergers. I will present results from two exciting lines of inquiry that the immigrant galaxies discovered in our survey have opened up: 1: they provide convenient, star-by-star access to the stellar chemistry of ``high-z” galaxies within a few kpc from the Sun at a resolution and scale inaccessible even to JWST -- as a case study I will present stringent constraints on the birth-sites of r-process elements; 2: the dark matter substructure produced by each of these mergers is upending our picture of the Galaxy -- as a case study I will argue that the last major merger at z~2 induced a 30 degree tilt in the Milky Way’s dark matter halo with respect to the disk that remarkably persists to this day, requiring us to revisit almost every conclusion drawn about the inner Galaxy assuming axisymmetry.

Link to the Event Video