Cross-calibration of Suzaku XIS and XMM-Newton EPIC using clusters of galaxies

TL;DR

This study compares Suzaku/XIS and XMM-Newton/EPIC instruments using galaxy clusters to evaluate and improve calibration accuracy, especially in the soft X-ray band, revealing necessary adjustments to contaminant models for better consistency.

Contribution

It extends previous cross-calibration work to include Suzaku/XIS, identifying calibration discrepancies and proposing contaminant column density adjustments for improved spectral consistency.

Findings

XIS instruments' hard band temperatures agree within 5%.

Soft band temperatures disagree by 9-29%, indicating calibration issues.

Adjusting contaminant column densities improves fit quality and consistency.

Abstract

We extend a previous cross-calibration study by the International Astronomical Consortium for High Energy Calibration (IACHEC) on XMM-Newton/EPIC, Chandra/ACIS and BeppoSAX/MECS X-ray instruments with clusters of galaxies to Suzaku/XIS instruments. Our aim is to study the accuracy of the energy-dependent effective area calibration of the XIS instruments by comparison of spectroscopic temperatures, fluxes and fit residuals obtained with Suzaku/XIS and XMM-Newton/EPIC-pn for the same cluster. The temperatures measured in the hard 2.0-7.0 keV energy band with all instruments are consistent within 5 %. However, temperatures obtained with the XIS instruments in the soft 0.5-2.0 keV band disagree by 9-29 %. We investigated residuals in the XIS soft band, which showed that if XIS0 effective area shape is accurately calibrated, the effective areas of XIS1 and XIS3 are overestimated below 1.0 keV (or vice versa). Adjustments to the modelling of the column density of the XIS contaminant in the 3-6 arcmin extraction region while forcing consistent emission models in each instrument for a given cluster significantly improved the fits. The oxygen column density in XIS1 and XIS3 contaminant must be increased by 1-2E17 cm^-2 in comparison to the values implemented in the current calibration, while the column density of the XIS0 contaminant given by the analysis is consistent with the public calibration. XIS soft band temperatures obtained with the modification to the column density of the contaminant agree better with temperatures obtained with the EPIC-pn instrument of XMM-Newton, than with those derived using the Chandra-ACIS instrument. However, comparison of hard band fluxes obtained using Suzaku-XIS to fluxes obtained using the Chandra-ACIS and EPIC-pn instruments proved inconclusive.