Power spectrum of intrinsic alignments of galaxies in IllustrisTNG

Abstract

We present the 3-dimensional intrinsic alignment power spectra between the projected 2d galaxy shape/spin and the 3d tidal field across 0.1<k/<60 using cosmological hydrodynamical simulation, Illustris-TNG300, at redshifts ranging from 0.3 to 2. The shape-tidal field alignment increases with galaxy mass and the linear alignment coefficient AIA, defined with respect to the primordial tidal field, is found to have weak redshift dependence. We also show a promising detection of the shape/spin-tidal field alignments for stellar mass limited samples and a weak or almost null signal for star-forming galaxies for the TNG300 volume, ∼ 0.01 (h-1 Gpc)3. We further study the morphology and environmental dependence of the intrinsic alignment power spectra. The shape of massive disk- and spheroid-galaxies tend to align with the tidal field. The spin of low mass disks (and spheroids at low redshifts) tend to be parallel with the tidal field, while the spin of massive spheroids and disks tend to be perpendicular to tidal field. The shape and spin of massive centrals align with the tidal field at both small and large scales. Satellites show a radial alignment within the one-halo term region, and low mass satellites have an intriguing alignment signal in the two-halo term region. We also forecast a feasibility to measure the intrinsic alignment power spectrum for spectroscopic and imaging surveys such as Subaru HSC/PFS and DESI. Our results thus suggest that galaxy intrinsic alignment can be used as a promising tool for constraining the galaxy formation models.

An Optimal Estimator of Intrinsic Alignments for Star-forming Galaxies in IllustrisTNG Simulation

“…The column "σ " in Table 1 gives the intrinsic rms ellipticities for the new method (Eq. 1), showing that the new method gives a larger σ ∼ 0.4 than that of the usual method, σ ∼ 0.3 as shown in Shi et al (2021). The IA power spectrum between matter density field δ m and E-mode shear field γ E is estimated following the method in Kurita et al (2021):…”

“…Observationally, several studies have shown a significant detection of the IA effect for luminous red galaxies up to z ∼ 0.7 (Mandelbaum et al 2006;Hirata et al 2007;Okumura & Jing 2009;Singh, Mandelbaum & More 2015;Singh & Mandelbaum 2016). In contrast, jingjing.shi@ipmu.jp there is no clear signature of the IA effect reported for blue star-forming galaxies from data (Mandelbaum et al 2011;Tonegawa et al 2018;Yao et al 2020) nor from simulations (Chisari et al 2016a;Tenneti, Mandelbaum & Di Matteo 2016;Shi et al 2021). Star-forming galaxies are useful tracers of large-scale structures up to the higher redshifts, and indeed main targets for upcoming wide-area galaxy redshift surveys such as the Subaru Prime Focus Spectrograph (PFS) survey (Takada et al 2014) and the DESI survey 1 .…”

“…To do this we use star-forming galaxies simulated in the IllustrisTNG (Springel et al 2018). We use our method to characterize shapes of the galaxies, and then measure the IA power spectrum based on the method in Kurita et al (2021) (also see Shi et al 2021). To make the realistic predictions, we take into account observational effects (sky background, filter transmission and seeing) when characterizing the galaxy shapes.…”

How the Galaxy Stellar Spins Acquire a Peculiar Tidal Connection?

“…Unlike the first one, however, the second question still awaits a conclusive answer, which requires expensive high-resolution cosmological hydrodynamical simulations. While several works reported that the alignment tendencies of the galaxy stellar spins with the local filaments were found similar to those of DM spins at low redshifts z ≤ 0.5 (e.g., Wang et al 2018;Kraljic et al 2020), several others claimed that the nonlinear baryonic process responsible for the deviation of the galaxy stellar spin directions from those of DM counterparts must have completely destroyed any tidal connection, randomizing the galaxy stellar spin vectors relative to the local filaments at z ≤ 0.5 (e.g., Codis et al 2018;Ganeshaiah Veena et al 2019;Shi et al 2021). The difference in the identifications of the filaments has been suggested as a possible reason for the discrepant results Kraljic et al (2020).…”

Intrinsic alignments of the extended radio continuum emission of galaxies in the EAGLE simulations

“…Duffy et al 2010;Schaller et al 2015a;Springel et al 2018). Hydrodynamical simulations have been used to study the intrinsic alignment of galaxies even well within the non-linear, one-halo regime (Chisari et al 2015(Chisari et al , 2016Codis et al 2015;Tenneti et al 2015;Velliscig et al 2015b;Hilbert et al 2017;Harvey et al 2021;Shi et al 2021). They offer a means to obtain physical insights into the origins of galaxy shape correlations, and to assess the accuracy of analytic alignment models (Samuroff et al 2021).…”