Group galaxy number density profiles far out: is the 'one-halo' term NFW out to $>10$ virial radii?

Abstract

While the density profiles (DPs) of $\Lambda$CDM haloes obey the NFW law out to roughly one virial radius, $r_{\mathrm{vir}}$, the structure of their outer parts is still poorly understood, since the 1-halo term describing the halo itself is dominated by the 2-halo term representing the other haloes picked up. Using a semi-analytical model, we measure the real-space `1-halo' number DP of groups out to $20r_{\mathrm{vir}}$ by assigning each galaxy to its nearest group with mass above $M_{\mathrm{a}}$, in units of the group $r_{\mathrm{vir}}$. If $M_{\mathrm{a}}$ is small (large), the outer DP of groups falls rapidly (slowly). We find that there is an optimal $M_{\mathrm{a}}$ for which the stacked DP resembles the NFW model to $0.1$ dex accuracy out to $\simeq 13r_{\mathrm{vir}}$. We find similar long-range NFW surface DPs (out to $\simeq 10r_{\mathrm{vir}}$) in the SDSS observations using a galaxy assignment scheme that combines the non-linear virialized regions of groups with their linear outer parts. The optimal $M_{\mathrm{a}}$ scales as the minimum mass of the groups that are stacked to the power $0.25-0.3$. Our results suggest that the NFW model does not solely originate from violent relaxation. Moreover, populating haloes with galaxies using HOD models must proceed out to larger radii than usually done.

5 pages, 4 figures. Accepted for publication in MNRAS Letters. Final version including discussion on the backsplash radius

References in corpus (7)

• K-corrections and filter transformations in the ultraviolet, optical, and near infrared
• Galaxy Groups in the SDSS DR4: I. The Catalogue and Basic Properties
• Rotation-Dependent Catastrophic Disruption of Gravitational Aggregates
• Methods for Rapidly Processing Angular Masks of Next-Generation Galaxy Surveys
• Understanding the shape of the halo-mass and galaxy-mass cross-correlation functions
• A Consistent Study of Metallicity Evolution at 0.8 < z < 2.6
• The universal distribution of halo interlopers in projected phase space. Bias in galaxy cluster concentration and velocity anisotropy?

Cited by in corpus (8)

• Euclid preparation III. Galaxy cluster detection in the wide photometric survey, performance and algorithm selection
• SPIDERS: overview of the X-ray galaxy cluster follow-up and the final spectroscopic data release
• From Blue Cloud to Red Sequence: Evidence of Morphological Transition Prior to Star Formation Quenching
• LoCuSS: The splashback radius of massive galaxy clusters and its dependence on cluster merger history
• The properties and environment of very young galaxies in the local Universe
• Stellar Population Properties of ETGs in Compact Groups of Galaxies
• Anisotropy and characteristic scales in halo density gradient profiles
• A full reconstruction of two galaxy clusters intra-cluster medium with strong gravitational lensing