Baryonic Imprints on DM Halos: Population Statistics from Dwarf Galaxies to Galaxy Clusters

Abstract

In a purely cold dark matter universe, the initial matter power spectrum and its subsequent gravitational growth contain no special mass-or time-scales, and so neither do the emergent population statistics of internal dark matter (DM) halo properties. Using 1.5 million halos from three I TNG realizations of a ΛCDM universe, we show that galaxy formation physics drives non-monotonic features ("wiggles") into DM property statistics across six decades in halo mass, from dwarf galaxies to galaxy clusters. We characterize these features by extracting the halo mass-dependent statistics of five DM halo properties -velocity dispersion, NFW concentration, density-and velocity-space shapes, and formation time -using kernellocalized linear regression (K ). Comparing precise estimates of normalizations, slopes, and covariances between realizations with and without galaxy formation, we find systematic deviations across all mass-scales, with maximum deviations of 25% at the Milky-Way mass of 10 12 M . The mass-dependence of the wiggles is set by the interplay between different cooling and feedback mechanisms, and we discuss its observational implications. The property covariances depend strongly on halo mass and physics treatment, but the correlations are mostly robust. Using multivariate K and interpretable machine learning, we show the halo concentration and velocity-space shape are principal contributors, at different mass, to the velocity dispersion variance. Statistics of mass accretion rate and DM surface pressure energy are provided in an appendix. We publicly release halo property catalogs and K parameters for the TNG runs at twenty epochs up to 𝑧 = 12.

Galaxy Velocity Bias in Cosmological Simulations: Towards Percent-level Calibration

“…This expectation has since been confirmed for DMO and non-radiative simulations by Evrard et al (2008), whose meta-analysis found 𝛼 = 0.3361 ± 0.0026. Simulations with full baryonic physics treatments of galaxy formation find similar results for high mass halos (Lau et al 2010;Armitage et al 2018), but deviations of order 10% in amplitude are found as one moves toward lower mass halos (Anbajagane et al 2021).…”

“…In principle, one could also add other halo properties to the scaling relation; studies of the I TNG simulations find that the scatter in 𝜎 DM is strongly correlated with secondary DM halo properties such as concentration and shape (Anbajagane et al 2021) and so it is plausible, though not necessary, that these secondary properties correlate with 𝜎 sat, 1D as well. At the halo mass scales of this study, Anbajagane et al (2021) show that the intrinsic variance in 𝜎 DM can be reduced by a factor of 2 when concentration and velocity anisotropy are included in the regression.…”

“…This is a localized linear regression method that provides mass-dependent estimates of the scaling parameters, and extracts the variation (or lack-thereof) of slope and scatter across halo mass. The method is particularly useful for estimating scaling relations in simulations that include baryonic processes; Anbajagane et al (2021) show that the scaling relations of key DM halo propertiesincluding 𝜎 DM -have clear mass-dependent features, across six decades in halo mass, that originate from these baryonic processes. The K method is also described in detail in that work.…”

“…We note the relevance of multiple full physics simulations exhibiting a mass-dependent slope across the range of redshifts probed in this analysis. The study of Anbajagane et al (2021), which spans six decades in halo mass across three I TNG simulation volumes, finds that population statistics of multiple DM propertiesvelocity dispersion, concentration, halo shapes, formation histories etc. -contain non-monotonic, mass-localized features which originate from the interplay between AGN feedback and gas cooling.…”

Shocks in the stacked Sunyaev-Zel’dovich profiles of clusters II: Measurements from SPT-SZ + Planck Compton-y map

“…The location of shock features also depends closely on the mass accretion rate of the cluster and can potentially serve as an observational proxy for the same (Lau et al 2015;Shi 2016;Zhang et al 2020Zhang et al , 2021. The mass accretion rate has strong theoretical connections to key dark matter halo properties like concentration and formation time (Wechsler et al 2002), and has also been shown to have significant correlations with a broad range of halo properties (e.g., Lau et al 2021;Anbajagane et al 2021). However, it has remained difficult to infer observationally.…”