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Group environments far out: density profiles and galaxy properties up to large halo-centric distances – Marina Trevisan (IF/UFRGS)
7 de março de 2018: 12:30 - 13:45
While the density profiles of ΛCDM haloes obey the Navarro, Frenk & White (NFW) law out to roughly one virial radius, r_vir, the structure of their outer parts is still poorly understood. By assigning each galaxy to its nearest group out to 20 r_vir, in both 3D (real space) simulated galaxy catalogues and 2+1D (redshift space) observed catalogues, we find that the group density profiles resemble the NFW model to 0.1 dex accuracy out to 10-13 r_vir. Thus, contrary to popular belief, it appears that the -3 slope of the NFW model is not caused by halo mergers, but by the combination of the primordial density field and the slow gravitational pull from the proto-group. Besides, if group haloes extend to such large distances, environmental effects on galaxies may occur far beyond r_vir. This is confirmed by our analysis of the radial variation of the fraction of star-forming galaxies, f_SF: f_SF increases smoothly up to ~6 r_vir. We explore if this large-scale variation of f_SF is caused by pre-processing in low-mass groups or if it is caused by a large-scale conformity related to a combination of the statistics of the primordial density field with assembly bias.