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

Abstract

Emission line galaxies (ELGs), more generally star-forming galaxies, are valuable tracers of large-scale structure and therefore main targets of upcoming wide-area spectroscopic galaxy surveys. We propose a fixed-aperture shape estimator of each ELG for extracting the intrinsic alignment (IA) signal, and assess the performance of the method using image simulations of ELGs generated from the IllustrisTNG simulation including observational effects such as the sky background noise. We show that our method enables a significant detection of the IA power spectrum with the linear-scale coefficient A IA ≃ (13–15) ± 3.0 up to z = 2, even from the small simulation volume ∼ 0.009 ( h − 1 Gpc ) 3 , in contrast to the null detection with the standard method. Thus the ELG IA signal, measured with our method, opens up opportunities to exploit cosmology and galaxy physics in high-redshift universe.

Tightening geometric and dynamical constraints on dark energy and gravity: galaxy clustering, intrinsic alignment and kinetic Sunyaev-Zel'dovich effect

“…Ref. [69] has proposed an estimator to directly detect IA of host halos using the observation of the ELGs. In the forecast analysis presented below, we consider that the power spectra related to the IA are measured with this estimator.…”

“…2 Following the result of Ref. [69], we set the fiducial value of the IA amplitude to A IA = 18, assuming its redshift independence. The PFS galaxy sample provides high-quality shape information thanks to the imaging survey of the HSC [74,75], and we thus set the shape noise, σ γ , to σ γ = 0.2 for the deep survey [112].…”

“…Ongoing and future galaxy surveys focus on observing LSS at higher redshifts, z > 1, at which the emission line galaxies (ELG) would be an ideal tracer of the LSS [18][19][20][63][64][65]. Although IA has not yet been detected for ELG [47,[66][67][68], recent work [69] has proposed an effective estimator to determine the IA of dark-matter halos using ELG, enhancing the signal-to-noise ratio at a statistically significant level. In any case, the accurate determination of galaxy shapes is of critical importance for IA to be a powerful tool to constrain cosmology.…”

Living with Neighbors. V. Better-aligned Spiral+Spiral Galaxy Pairs Show Stronger Star Formation

“…;Lee & Erdogdu 2007;Slosar et al 2009;Lee 2011;Hung & Ebeling 2012;Li et al 2013;Zhang et al 2013;Krolewski et al 2019;Kraljic et al 2021;Shamir 2022) and computational studies (e.g.,Porciani et al 2002;Bailin & Steinmetz 2005;Faltenbacher et al 2008;Trowland et al 2013;Prieto et al 2015;González et al 2017;Lee 2019;Shi et al 2021…”

“…galaxy pairs remains inconclusive(Joachimi & Schneider 2010;Andrae & Jahnke 2011;Lee 2011;Buxton & Ryden 2012;Chisari et al 2015;Sifón et al 2015;Koo & Lee 2018;Krolewski et al 2019). Such alignment signals also seem to be subtly influenced by various intrinsic properties of the galaxies, including the halo mass(Li et al 2013;Trowland et al 2013;Xia et al 2017), bulge mass(Barsanti et al 2022), SF activity(Jimenez et al 2010;Shi et al 2021), and spiral morphology(Hu et al 1995;Lee 2011;Koo & Lee 2018). For example,…”