An X-ray Spectroscopic Search for Dark Matter in the Perseus Cluster with Suzaku

TL;DR

This study used Suzaku X-ray data to search for a 3.5keV dark matter decay line in the Perseus cluster, finding no evidence and discussing instrumental and modeling uncertainties.

Contribution

First Suzaku-based analysis to test the 3.5keV line claim, providing upper limits and discussing calibration and modeling issues affecting detection.

Findings

No 3.5keV line detected in Suzaku data

Set upper limits on line flux below previous claims

Discussed calibration and modeling uncertainties

Abstract

We present the results from deep Suzaku observations of the central region of the Perseus cluster. Bulbul et al. (2014) reported the detection by XMM-Newton instruments of an unidentified X-ray emission line at an energy around 3.5keV in spectra for the Perseus and other clusters. They argued for a possibility of the decay of sterile neutrino, a dark matter candidate. We examine Suzaku X-ray Imaging Spectrometer (XIS) spectra of the Perseus cluster for evidence in the 3.5keV line and other possible dark matter features in the 2-6keV energy band. In order to search for and constrain a weak line feature with the XIS, observations of the Crab nebula are used to evaluate the system's effective area. We found no line feature at the claimed position with a systematic line flux upper limit at a half (1.5eV in line equivalent width) of the claimed best-fit value by Bulbul et al. We discuss this inconsistency in terms of instrumental calibration errors and modeling of continuum emission. Future prospects for high-energy resolution spectroscopy with ASTRO-H are presented.