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SUMMARY:Tidally perturbed 'feeble giant' dwarf galaxies
DTSTART;VALUE=DATE-TIME:20230322T093500Z
DTEND;VALUE=DATE-TIME:20230322T093700Z
DTSTAMP;VALUE=DATE-TIME:20241114T092434Z
UID:indico-contribution-254@meetings.aip.de
DESCRIPTION:Speakers: Alexandra Borukhovetskaya (University of Victoria)\n
 The unusually low velocity dispersion and large sizes of `feeble giant' ga
 laxies\, such as Crater II or Antlia II\, pose a challenge to our understa
 nding of dwarf galaxies in the Lambda Cold Dark Matter (LCDM) cosmogony. T
 heir low velocity dispersions suggest either a dark halo mass much lower t
 han the minimum expected from hydrogen cooling limit arguments\, or one th
 at is in the late stages of extreme tidal stripping. The tidal interpretat
 ion has been favoured in recent work and is supported by the small pericen
 tric distances consistent with available kinematic estimates from Gaia. We
  use N-body simulations to examine this interpretation in detail\, assumin
 g a Navarro-Frenk-White (NFW) profile for the Crater II and Antlia II prog
 enitor halos. Our main finding is that\, although the low velocity dispers
 ions can indeed result from the effect of tides\, the large sizes of feebl
 e giants are inconsistent with this hypothesis. This is because galaxies s
 tripped in mass to match the observed velocity dispersions are also reduce
 d to sizes much smaller than the observed half-light radii of Crater II an
 d Antlia II. Unless their sizes has been substantially overestimated\, rec
 onciling systems like these (including Andromeda XXV and XIX) with LCDM re
 quires that either (i) they are not bound and near equilibrium (unlikely\,
  given their crossing times are shorter than the time elapsed since perice
 ntre)\, or that (ii) their progenitor halos deviate from the assumed NFW p
 rofile. The latter alternative may signal that baryons can affect the inne
 r halo cusp even in extremely faint dwarfs or\, more intriguingly\, may si
 gnal effects associated with the intimate nature of the dark matter\, such
  as finite self-interactions\, or other such deviations from the canonical
  LCDM paradigm.\n\nhttps://iaus379.aip.de/event/20/contributions/254/
LOCATION:Haus H\, Telegrafenberg
URL:https://iaus379.aip.de/event/20/contributions/254/
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