20-24 March 2023
Haus H, Telegrafenberg
Europe/Berlin timezone

Small-scale stellar haloes: detecting extended substructure in the outskirts of Milky Way dwarf galaxy satellites

22 Mar 2023, 11:45
Haus H, Telegrafenberg

Haus H, Telegrafenberg

Potsdam, Germany
Contributed talk SESSION 3 : Dwarf galaxies: dwarf spheroidal, ultra-faint dwarfs, dwarf irregulars SESSION 3 : Dwarf galaxies: dwarf spheroidal, ultra-faint dwarfs, dwarf irregulars


Jaclyn Jensen (University of Victoria)


Dwarf galaxies are valuable laboratories for dynamical studies related to dark matter and galaxy evolution, yet it is currently unknown just how extended their stellar components are. Each satellite orbiting within the Milky Way’s (MW’s) gravitational potential may undergo tidal stripping by the host galaxy, or alternatively, may themselves have accreted yet smaller systems whose debris settles into the satellite’s own stellar halo. Both processes could mean that significant populations of member stars are found far from the center of the dwarf. Stars in the outskirts of these systems are especially valuable – and rare – tracers of the dwarf’s dynamics in low acceleration regimes, and they give insight into the dwarf’s evolutionary history. In this work, we examine the MW’s ~60 dwarf satellites to search for these rare, distant member stars. Using Gaia eDR3 and a maximum likelihood approach allowing for multi-component extended substructures, we find 9 dwarfs that exhibit a secondary, lower-density, outer profile, that we argue is indicative of an extended stellar halo and/or tidal disruption. Our method shows excellent consistency with spectroscopically confirmed members from the literature and requires no radial velocity information. For each dwarf galaxy, we derive a sample of high-confidence members which will prove useful for studying even the faintest MW dwarfs. We also briefly discuss a current spectroscopic follow-up campaign for the most radially distant outskirt members, which will feature the newly commissioned Gemini High-resolution Optical SpecTrograph (GHOST). Already, initial spectra obtained during GHOST commissioning has proven useful for comprehensive chemodynamics of these Galactic building blocks.

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Primary author

Jaclyn Jensen (University of Victoria)


Dr Alan McConnachie (NRC Herzberg Astronomy & Astrophysics) Dr Christian Hayes (NRC Herzberg Astronomy & Astrophysics) Fletcher Waller (University of Victoria)

Presentation Materials