42309 observed satellites uw astr 323 sp09 eric agol

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Unformatted text preview: causes interac8ng galaxies to fall towards center as they lose velocity: runaway •  Small bodies are _________: may help to explain the thick disk (scaYering by _______ molecular clouds) •  •  •  •  5/16/13 UW, ASTR 323, SP13, Eric Agol ©2013 8 Runaway merger •  •  •  •  •  Angular momentum: L=Mvr Torque: τ=fdr=dL/dt v2 ρ= Isothermal sphere: 4π Gr 2 so fd=CGM2/r2 So, 5/16/13 UW, ASTR 323, SP13, Eric Agol ©2013 9 LMC merger 8mescale •  r0=50 kpc; MLMC=1010 M_sun 5/16/13 UW, ASTR 323, SP13, Eric Agol ©2013 10 Missing satellite problem Predicted satellites Predic8on: lots of ____ satellites! 4/23/09 Observed satellites UW, ASTR 323, SP09, Eric Agol ©2009 11 Missing satellite problem •  Models for forma8on of Milky Way by hierarchical merging predict ~___ satellites above 2×107 M¤༊. •  Only ~___ satellites have been found •  Possible solu8ons: (1) satellites may be ____ to find; (2) small satellites are _______ stars due to feedback or hea8ng of gas; (3) something is _____ with Galaxy forma8on model (different dark maYer model?) 4/23/09 UW, ASTR 323, SP09, Eric Agol ©2009 12 Mass/luminosity uncorrelated 5/16/13 UW, ASTR 323, SP13, Eric Agol ©2013 13 S...
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