The evolution of galaxy intrinsic alignments in the MassiveBlackII universe

Abstract

We investigate the redshift evolution of the intrinsic alignments (IA) of galaxies in the MassiveBlackII (MBII) simulation. We select galaxy samples above fixed subhalo mass cuts (M h > 10 11,12,13 M /h) at z = 0.6 and trace their progenitors to z = 3 along their merger trees. Dark matter components of z = 0.6 galaxies are more spherical than their progenitors while stellar matter components tend to be less spherical than their progenitors. The distribution of the galaxy-subhalo misalignment angle peaks at ∼ 10 deg with a mild increase with time. The evolution of the ellipticity-direction (ED) correlation amplitude ω(r) of galaxies (which quantifies the tendency of galaxies to preferentially point towards surrounding matter overdensities) is governed by the evolution in the alignment of underlying dark matter (DM) subhaloes to the matter density of field, as well as the alignment between galaxies and their DM subhaloes. At scales ∼ 1 cMpc/h, the alignment between DM subhaloes and matter overdensity gets suppressed with time, whereas the alignment between galaxies and DM subhaloes is enhanced. These competing tendencies lead to a complex redshift evolution of ω(r) for galaxies at ∼ 1 cMpc/h. At scales > 1 cMpc/h, alignment between DM subhaloes and matter overdensity does not evolve significantly; the evolution of the galaxy-subhalo misalignment therefore leads to an increase in ω(r) for galaxies by a factor of ∼ 4 from z = 3 to 0.6 at scales > 1 cMpc/h. The balance between competing physical effects is scale dependant, leading to different conclusions at much smaller scales (∼ 0.1 Mpc/h).

The Three Hundred project: shapes and radial alignment of satellite, infalling, and backsplash galaxies

“…Previous studies (i.e. Tenneti et al 2014;Velliscig et al 2015a;Chisari et al 2017;Xia et al 2017;Bhowmick et al 2019) state that lower mass objects tend to show marginally less alignment, as the stellar component becomes more spherical for lower halo masses hence making it more difficult for alignment to be quantified. However, we only observe such a tendency for the infalling population that has not yet experienced any influence of the central galaxy cluster.…”

“…There is quite a body of theoretical work in connection to the relation between the shape and halo mass including field haloes (Allgood et al 2006;Hahn et al 2007;Chisari et al 2017;Chua et al 2019), subhaloes (Kuhlen et al 2007;Tenneti et al 2014;Vera-Ciro et al 2014;Barber et al 2015;Velliscig et al 2015a;Bhowmick et al 2019), and also the stellar component (Tenneti et al 2014(Tenneti et al , 2015bBhowmick et al 2019). They all report a mild dependence of shape on halo mass in the sense that more massive haloes appear to be less spherical; Tenneti et al (2014) even provide a fitting function for this relation.…”

Strong detection of the CMB lensing and galaxy weak lensing cross-correlation from ACT-DR4,PlanckLegacy, and KiDS-1000

“…We turn now to parameters of the model. We follow the same modelling methods described as for the main cosmological inference analysis, but here we fix the cosmological parameters to a Planck 2018 cosmology and constrain ∆z and m. It is anticipated that intrinsic alignment is highly suppressed at such high redshifts (Chisari et al 2017;Bhowmick et al 2020), hence we set the intrinsic alignment amplitude A IA = 0.…”

Tightening weak lensing constraints on the ellipticity of galaxy-scale dark matter haloes

“…Several approaches have been used to test this prediction and constrain halo shapes as well as the relative alignment of galaxies with their haloes observationally; these approaches have included the use of baryonic tracers such as satellite galaxies (e.g., Okumura et al 2009;Agustsson & Brainerd 2010;Hayashi & Chiba 2014;Shin et al 2018;Georgiou et al 2019a) and studies of stellar and gas kinematics in polar ring (Khoperskov et al 2014) or edge-on galaxies (Peters et al 2017). Such measurements allow us to test predictions from hydrodynamical simulations, which aim to model galaxy formation and evolution, including the interplay, relative distribution, and alignment of the baryonic and dark matter components (e.g., Tenneti et al 2014Tenneti et al , 2016Laigle et al 2015;Debattista et al 2015;Velliscig et al 2015;Codis et al 2018;Chua et al 2019;Bate et al 2020;Bhowmick et al 2020).…”