1809.09116
The aftermath of the great collision between our galaxy and the Large Magellanic Cloud
Cautun, et al
The MW offers a uniquely detailed view of galactic structure and is often regarded as a prototypical spiral galaxy. But recent observations indicate that the MW is atypical: it has an undersized supermassive black hole at its centre; it is surrounded by a very low mass, excessively metal-poor stellar halo; and it has an unusually large nearby satellite galaxy, the LMC. Here, show that the LMC is on a collision course with the MW with which it will merge in 2.4+1.2-0.8 Gyrs (68% CL). This catastrophic and long-overdue event will restore the MW to normality. Using the EAGLE galaxy formation simulation, show that, as a result of the merger, the central supermassive black hole will increase in mass by up to a factor of 8. The Galactic stellar halo will undergo an equally impressive transformation, becoming 5x more massive. The additional stars will come predominantly from the disrupted LMC, but a sizable number will be ejected onto the halo from the stellar disc. The post-merger stellar halo will have the median metallicity of the LMC, [Fe/H]=-0.5 dex, which is typical of other galaxies of similar mass to the MW. At the end of this exceptional event, the MW will become a true benchmark for spiral galaxies, at least temporarily.
1809.10045
Weak lensing constraints on splash back around massive clusters
Contigiani, Hoekstra, Bahé
The splash back radius r_sp separates the physical regimes of collapsed and infalling material around massive DM haloes. In cosmo sims, this location is associated with a steepening of the spherically averaged density profile rho(r). In this work, measure the splash back feature in the stacked WL signal of 27 massive clusters from the CCCP with a careful control of residual systematics effects. Find that the shear introduced by the presence of additional structure along the line of sight significantly affects the noise at large cluster centric distances. Do not detect a significant steepening, but are able to constrain both r_sp=3.6+1.2-0.7 comoving Mpc and the value of the logarithmic slope gamma=log(rho) / log(r) at this point, gamma(r_sp)=-4.2+1.0-1.8.
The aftermath of the great collision between our galaxy and the Large Magellanic Cloud
Cautun, et al
The MW offers a uniquely detailed view of galactic structure and is often regarded as a prototypical spiral galaxy. But recent observations indicate that the MW is atypical: it has an undersized supermassive black hole at its centre; it is surrounded by a very low mass, excessively metal-poor stellar halo; and it has an unusually large nearby satellite galaxy, the LMC. Here, show that the LMC is on a collision course with the MW with which it will merge in 2.4+1.2-0.8 Gyrs (68% CL). This catastrophic and long-overdue event will restore the MW to normality. Using the EAGLE galaxy formation simulation, show that, as a result of the merger, the central supermassive black hole will increase in mass by up to a factor of 8. The Galactic stellar halo will undergo an equally impressive transformation, becoming 5x more massive. The additional stars will come predominantly from the disrupted LMC, but a sizable number will be ejected onto the halo from the stellar disc. The post-merger stellar halo will have the median metallicity of the LMC, [Fe/H]=-0.5 dex, which is typical of other galaxies of similar mass to the MW. At the end of this exceptional event, the MW will become a true benchmark for spiral galaxies, at least temporarily.
1809.10045
Weak lensing constraints on splash back around massive clusters
Contigiani, Hoekstra, Bahé
The splash back radius r_sp separates the physical regimes of collapsed and infalling material around massive DM haloes. In cosmo sims, this location is associated with a steepening of the spherically averaged density profile rho(r). In this work, measure the splash back feature in the stacked WL signal of 27 massive clusters from the CCCP with a careful control of residual systematics effects. Find that the shear introduced by the presence of additional structure along the line of sight significantly affects the noise at large cluster centric distances. Do not detect a significant steepening, but are able to constrain both r_sp=3.6+1.2-0.7 comoving Mpc and the value of the logarithmic slope gamma=log(rho) / log(r) at this point, gamma(r_sp)=-4.2+1.0-1.8.
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