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SUMMARY:Galaxy mergers and disk angular momentum evolution: stellar halos 
 as a critical test
DTSTART:20260511T124500Z
DTEND:20260511T130000Z
DTSTAMP:20260509T051800Z
UID:indico-event-1823@indico.dfa.unipd.it
DESCRIPTION:Speakers: Guanyu Wang (Università degli Studi di Padova)\n\nW
 e investigate the role of hierarchical assembly in the angular momentum (A
 M) evolution of galaxies using a sample of 471 Milky Way-mass galaxies fro
 m the TNG-50 simulation. While galaxy orientation is often attributed to t
 idal torques and the cooling of gas within halos\, we demonstrate that gal
 axy reorientation (tilting) is a common consequence of satellite accretion
 . Specifically\, 80% of galaxies show alignment between their present-day 
 AM and the orbital AM of their most massive (dominant) merger progenitor. 
 This reorientation typically results in changes of around 50% in the galax
 ies’ specific AM\, with the most significant shifts occurring in galaxie
 s that were initially highly misaligned. We find only a weak influence fro
 m the second most massive merger\, and negligible impacts from surviving s
 atellites. We show that accreted stellar halos encode the history of this 
 reorientation. Driven by the same accretion event\, the main bodies of gal
 axies and their stellar halos tend to co-align\, with 81% of TNG-50 stella
 r halos showing prograde rotation relative to the galaxy. This signature w
 ill be detectable through major-axis kinematics with 30-meter class telesc
 opes for Milky Way mass galaxies\, offering a valuable observational test 
 of this picture. While halo rotation directly constrains the specific AM o
 f mergers within the last \,Gyr\, this kinematic ‘memory’ is largely e
 rased for older and more radial events. Consequently\, the Milky Way itsel
 f appears to be a notable exception to the general merger-driven trend: TN
 G-50 analogs with early\, radial\, and low angular momentum dominant merge
 rs affect present-day disk orientation minimally. The current MW disk orie
 ntation may instead reflect the accumulated influences of gas accretion or
  dark matter torques.\n\n\nhttps://indico.dfa.unipd.it/event/1823/
LOCATION:Aula Rosino (Dipartimento di Fisica e Astronomia - Edificio ex-Ri
 zzato)
URL:https://indico.dfa.unipd.it/event/1823/
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