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

Hideki Tanimura, Gary Hinshaw, Ian G. McCarthy, Ludovic Van Waerbeke, Nabila Aghanim, Yin-Zhe Ma, Alexander Mead, Alireza Hojjati, Tilman Tröster

Research output: Contribution to journalArticlepeer-review


We search the Planck data for a thermal Sunyaev–Zel’dovich (tSZ) signal due to gas filaments between pairs of Luminous Red Galaxies (LRGs) taken from the Sloan Digital Sky Survey Data Release 12 (SDSS/DR12). We identify ∼260 000 LRG pairs in the DR12 catalogue that lie within 6–10 h−1Mpc of each other in tangential direction and within 6 h−1Mpc 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 (5.3σ) signal between LRG pairs in the stacked data with a magnitude Δy = (1.31 ± 0.25) × 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 overdensity with a radial density profile proportional to rc/r (as determined from simulations), where r is the perpendicular distance from the cylinder axis and rc is the core radius of the density profile, we constrain the product of overdensity and filament temperature to be δc×(Te/107K)×(rc/0.5h−1Mpc)=2.7±0.5⁠. To our knowledge, this is the first detection of filamentary gas at overdensities 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, Δy = (0.84 ± 0.24) × 10−8.
Original languageEnglish
Number of pages10
JournalMonthly Notices of the Royal Astronomical Society
Early online date16 Nov 2018
Publication statusPublished - 1 Feb 2019


  • astro-ph.CO


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