Search for x-ray emission associated with the Shapley supercluster with Suzaku

Ikuyuki Mitsuishi, Anjali Gupta, Noriko Y. Yamasaki, Yoh Takei, Takaya Ohashi, Kosuke Sato, Massimiliano Galeazzi, J. Patrick Henry, Richard L. Kelley

Research output: Contribution to journalArticle

1 Scopus citations

Abstract

Suzaku performed observations of 3 regions in and around the Shapley supercluster, a region located between A 3558 and A 3556, at ∼0.9 times the virial radii of both clusters, and two other regions at 1° and 4° away from the first pointing. The 4°-offset observation was used to evaluate the Galactic foreground emission. We did not detect significant redshifted Oxygen emission lines (O VII and O VIII) in the spectra of all three pointings, after subtracting the contribution of foreground and background emission. The upper limit for the redshifted O VIII K? line intensity of the warm-hot intergalactic medium (WHIM) is 1.5 × 10-7 photons s-1 cm -2 arcmin-2, which corresponds to an overdensity of ∼380 (Z=0.1 Z--1/2 (L=3Mpc)-1/2, assuming T = 3 × 106K. We found excess continuum emission in the 1°-offset and on-filament regions, represented by thermal models with kT ∼ 1 keV and ∼2keV, respectively. The redshifts of both 0 and that of the supercluster (0.048) are consistent with the observed spectra. The ∼ 1 keV emission can also be fitted with Ne-rich Galactic (zero redshift) thin thermal emission. The radial intensity profile of the 2 keV component suggests contributions from A 3558 and A 3556, but with significant steepening of the intensity slope in the outer region of A 3558. Finally, we summarized the previous Suzaku search for the WHIM, and discussed the feasibility of constraining the WHIM. An overdensity of < 400 could be detectable using O VII and O VIII emission lines in a range of 1.4 × 106 K < T < 5 × 106 K or a continuum emission in a relatively high-temperature range of T > 5 × 106 K with the Suzaku XIS. The non-detection with Suzaku suggests that a typical line-of-sight average overdensity is <400.

Original languageEnglish (US)
JournalPublications of the Astronomical Society of Japan
Volume64
Issue number1
DOIs
StatePublished - Feb 25 2012

Keywords

  • Intergalactic medium
  • Supercluster
  • X-rays: galaxies: clusters

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Mitsuishi, I., Gupta, A., Yamasaki, N. Y., Takei, Y., Ohashi, T., Sato, K., Galeazzi, M., Henry, J. P., & Kelley, R. L. (2012). Search for x-ray emission associated with the Shapley supercluster with Suzaku. Publications of the Astronomical Society of Japan, 64(1). https://doi.org/10.1093/pasj/64.1.18