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SUMMARY:Do dark-matter-deficient dwarf galaxies present a challenge to the
  LCDM paradigm? - Sugata Kaviraj\, Hertfordshire
DTSTART:20211021T150000Z
DTEND:20211021T160000Z
UID:TALK162619@talks.cam.ac.uk
CONTACT:Nicolas Laporte
DESCRIPTION:In the standard LCDM paradigm\, dwarf galaxies are expected to
  be dark matter-rich\, as baryonic feedback is thought to quickly drive ga
 s out of their shallow potential wells and quench star formation at early 
 epochs. Recent observations of local dwarfs with extremely low dark matter
  content appear to contradict this picture\, potentially bringing the vali
 dity of the standard model into question. We use New Horizon\, a high-reso
 lution cosmological simulation\, to demonstrate that sustained stripping o
 f dark matter\, in tidal interactions between a massive galaxy and a dwarf
  satellite\, naturally produces dwarfs that are dark matter-deficient\, ev
 en though their initial dark matter fractions are normal. The process of d
 ark matter stripping is responsible for the large scatter in the halo-to-s
 tellar mass relation in the dwarf regime. The degree of stripping is drive
 n by the closeness of the orbit of the dwarf around its massive companion 
 and\, in extreme cases\, produces dwarfs with halo-to-stellar mass ratios 
 as low as unity\, consistent with the findings of recent observational stu
 dies. ~30 per cent of dwarfs show some deviation from normal dark matter f
 ractions due to dark matter stripping\, with 10 per cent showing high leve
 ls of dark matter deficiency (M_halo/M_⋆< 10). Given their close orbits\
 , a significant fraction of dark matter-deficient dwarfs merge with their 
 massive companions (e.g. ~70 per cent merge over time-scales of ~3.5 Gyr)\
 , with the dark matter-deficient population being constantly replenished b
 y new interactions between dwarfs and massive companions. The creation of 
 these galaxies is therefore a natural by-product of galaxy evolution and t
 heir existence is not in tension with the standard paradigm.\n
LOCATION:Sackler (sign-up needed) + ONLINE - Details will be sent by email
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