# A Search for Warm/Hot Gas Filaments Between Pairs of SDSS Luminous Red Galaxies

Tanimura, H, Hinshaw, G, McCarthy, IG, Waerbeke, LV, Aghanim, N, Ma, Y-Z, Mead, A, Hojjati, A and Tröster, T (2018) A Search for Warm/Hot Gas Filaments Between Pairs of SDSS Luminous Red Galaxies. Monthly Notices of the Royal Astronomical Society, 483 (1). pp. 223-234. ISSN 0035-8711

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Open Access URL: https://dx.doi.org/10.1093/mnras/sty3118 (Published version)

## Abstract

We search the Planck data for a thermal Sunyaev-Zel'dovich (tSZ) signal due to gas filaments between pairs of Luminous Red Galaxies (LRG's) taken from the Sloan Digital Sky Survey Data Release 12 (SDSS/DR12). We identify $\sim$260,000 LRG pairs in the DR12 catalog that lie within 6-10 $h^{-1} \mathrm{Mpc}$ of each other in tangential direction and within 6 $h^{-1} \mathrm{Mpc}$ in radial direction. We stack pairs by rotating and scaling the angular positions of each LRG so they lie on a common reference frame, then we subtract a circularly symmetric halo from each member of the pair to search for a residual signal between the pair members. We find a statistically significant (5.3$\sigma$) signal between LRG pairs in the stacked data with a magnitude $\Delta y = (1.31 \pm 0.25) \times 10^{-8}$. The uncertainty is estimated from two Monte Carlo null tests which also establish the reliability of our analysis. Assuming a simple, isothermal, cylindrical filament model of electron over-density with a radial density profile proportional to $r_c/r$ (as determined from simulations), where $r$ is the perpendicular distance from the cylinder axis and $r_c$ is the core radius of the density profile, we constrain the product of over-density and filament temperature to be $\delta_c \times (T_{\rm e}/10^7 \, {\rm K}) \times (r_c/0.5h^{-1} \, {\rm Mpc}) = 2.7 \pm 0.5$. To our knowledge, this is the first detection of filamentary gas at over-densities typical of cosmological large-scale structure. We compare our result to the BAHAMAS suite of cosmological hydrodynamic simulations (McCarthy et al. 2017) and find a slightly lower, but marginally consistent Comptonization excess, $\Delta y = (0.84 \pm 0.24) \times 10^{-8}$.

Item Type: Article This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2018 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. 0201 Astronomical and Space Sciences Q Science > QB AstronomyQ Science > QC Physics Astrophysics Research Institute Oxford University Press Author 21 Feb 2019 09:15 03 Sep 2021 23:41 10.1093/mnras/sty3118 https://researchonline.ljmu.ac.uk/id/eprint/10191