toy model for splashback€¦ · • quiz time: which halo in fig 1 has a larger accretion rate?...
TRANSCRIPT
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33.. SShhaarrpp ddrroopp iinn ddeennssiittyy:: aa pphhyyssiiccaall ffeeaattuurree
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TThhee SSppllaasshhbbaacckk RRaaddiiuussSurhud More (Kavli IPMU), Benedikt Diemer (Harvard), Andrey Kravtsov (UChicago),
Hironao Miyatake (JPL), Masahiro Takada (Kavli IPMU), Neal Dalal (UIUC)
SSuummmmaarryy• Splashback radius is a physical boundary for dark matter halos, which
depends upon the mass and the mass accretion rate history of the halo.• We have detected the splashback radius of massive galaxy clusters from
SDSS, a preliminary comparison shows that it is smaller than expectedfrom cosmological simulations, a systematic study is currentlyunderway.
RReeffeerreenncceess• The density profiles (upper
panels) of the halos aboveshow sharp density drops attheir outskirts.
• The solid circles in the pollabove capture the steepest slopeof the density profile (lowerpanel).
More, Diemer & Kravtsov 2015
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• Do dark matter halos have boundaries? Yes!
• Are these boundaries physically interesting? Yes!
• Can these halo boundaries be observed? Yes!
More, Diemer & Kravtsov 2015
• These galaxy clustersized halos have equal masses.• Which of these lines would you assign as the physical
boundary of dark matter halos? Poll by ticking below:• Solid:• Dotted:
• Splashback radius is related to the orbits of dark matter particleswithin halos.
• The observed density drops are a result of the pile up of darkmatter particles due to small radial velocities near the apocenter.
• If the potential deepens during the particle orbit due to massaccretion on to the halo, particles do not reach as far out.
• Larger the accretion rate, smaller the splashback radius• Quiz time: Which halo in Fig 1 has a larger accretion rate?
Sp
lash
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Faster accretion rate, smaller splashback radius
Toy model for Splashback
• We obtained the surface density profiles of galaxies around massiveclusters identified from the Sloan Digital Sky Survey
• The surface density profiles also show sharp steepening (solid line)corresponding to the splashback radius of these clusters
• Subhalo density profiles around simulated clusters of similar mass(dashed line) show that the observed splashback radius is smaller byabout 20 percent.
• Could it be due to some systematics in optical cluster finding or dueto dark matter selfinteractions?
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Mi-5 logh<-19.43
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More et al. 2016
Pseudoevolution of halo mass, Diemer,More & Kravtsov 2013, ApJ, 766, 25;
The outer density profiles of dark matterhalos, Diemer & Kravtsov, 2014, ApJ,789, 1;
Splashback radius as the physical haloboundary and the growth of halo mass,More, Diemer & Kravtsov, 2015, ApJ,810, 1;
Detection of the Splashback radius and haloassembly bias of massive clusters, Moreet al. 2016, ApJ, 825, 39;