A search for warm/hot gas filaments between pairs of SDSS Luminous Red Galaxies
Abstract
We search the Planck data for a thermal SunyaevZel'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 610 $h^{1} \, \mathrm{Mpc}$ 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 (5.3σ) 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 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 overdensity and filament temperature to be $\delta _\mathrm{ c} \times (T_{\rm e}/10^7 \, {\rm K}) \times (r_\mathrm{ c}/0.5h^{1} \, {\rm Mpc}) = 2.7 \pm 0.5$. To our knowledge, this is the first detection of filamentary gas at overdensities typical of cosmological largescale 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}.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 February 2019
 DOI:
 10.1093/mnras/sty3118
 arXiv:
 arXiv:1709.05024
 Bibcode:
 2019MNRAS.483..223T
 Keywords:

 galaxies: clusters: general;
 galaxies: groups: general;
 galaxies: haloes;
 largescale structure of Universe;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 10 pages, 9 figures, accepted for publication in MNRAS (v4 and v5 to include funding acknowledgements. No other changes.)