Special Seminar | Dr. Guilherme Limberg

Speaker: Dr. Guilherme Limberg (Kavli Institute for Cosmological Physics at the University of Chicago/USA)
Title: Tidal disruption of "mega-diffuse" dwarf galaxies and the stellar mass—metallicity relation in the Local Group

Abstract: Unveiling the driving mechanisms behind galaxy formation and growth is one of the main goals of Astrophysics. In this context, the Local Group serves as a laboratory where star-by-star spectroscopy provides detailed chemistry and kinematics for both the Milky Way itself and its dwarf satellites. In this talk, I will present results from a spectroscopic follow-up program on Crater 2 dwarf galaxy conducted within the Southern Stellar Stream Spectroscopic Survey (S5). Crater 2 is a Milky Way satellite with an extremely low surface brightness of >30 mag per arcsecond squared, which is ~100x more diffuse than so-called “ultra-diffuse” galaxies. The size of Crater 2 for its central velocity dispersion is so humongous that it represents a challenge to galaxy formation in dark matter (Navarro-Frenk-White) cuspy halos. I will present the unequivocal detection of a stellar stream around Crater 2 which aligns with its proper motion vector and with the predicted tidal debris track from orbital dynamical modeling, with stars reaching as far as 20x the half-light radius away from the center of this galaxy. We also detect a >10 sigma line-of-sight velocity gradient, as expected from a tidal disruption scenario. With our program data, I will also discuss how Crater 2, as well as other “mega-diffuse” dwarfs like it (Antlia 2 and Andromeda XIX), has a lower metallicity than predicted from the stellar mass—metallicity relation derived from Local Group galaxies, a discrepancy that becomes even worse after compensating for mass loss. I will cover some hypotheses that could explain both huge sizes and low metallicities of the emerging class of mega-diffuse dwarfs.

Note: Dr. Limberg is visiting AIP for 3 weeks (March 10th until March 28th) as part of the International Research Network for Nuclear Astrophysics (IReNA) Visiting Fellowships for Early Career Researchers

• Datum:
  27. März 2025, 11:00 – 12:00
  
  
• Ort:

  AIP; Schwarzschildhaus, Lecture hall

  
  
• Kontakt:
  Cristina Chiappini
  cristina.chiappini@aip.de