J/A+A/575/A30 HIFLUGCS XMM/Chandra cross-calibration (Schellenberger+, 2015)
XMM-Newton and Chandra cross-calibration using HIFLUGCS galaxy clusters.
Systematic temperature differences and cosmological impact.
Schellenberger G., Reiprich T.H., Lovisari L., Nevalainen J., David L.
<Astron. Astrophys., 575, A30-30 (2015)>
=2015A&A...575A..30S 2015A&A...575A..30S
ADC_Keywords: Clusters, galaxy
Keywords: X-rays: galaxies: clusters - instrumentation: miscellaneous -
galaxies: clusters: intracluster medium - techniques: spectroscopic
Abstract:
Robust X-ray temperature measurements of the intracluster medium (ICM)
of galaxy clusters require an accurate energy-dependent effective area
calibration. Since the hot gas X-ray emission of galaxy clusters does
not vary on relevant timescales, they are excellent cross-calibration
targets. Moreover, cosmological constraints from clusters rely on
accurate gravitational mass estimates, which in X-rays strongly depend
on cluster gas temperature measurements. Therefore, systematic
calibration differences may result in biased, instrument-dependent
cosmological constraints. This is of special interest in light of the
tension between the Planck results of the primary temperature
anisotropies of the cosmic microwave background (CMB) and
Sunyaev-Zel'dovich-plus-X-ray cluster-count analyses. We quantify in
detail the systematics and uncertainties of the cross-calibration of
the effective area between five X-ray instruments, EPIC-MOS1/MOS2/PN
onboard XMM-Newton and ACIS-I/S onboard Chandra, and the influence on
temperature measurements. Furthermore, we assess the impact of the
cross-calibration uncertainties on cosmology. Using the HIFLUGCS
sample, consisting of the 64 X-ray brightest galaxy clusters, we
constrain the ICM temperatures through spectral fitting in the same,
mostly isothermal regions and compare the different instruments. We
use the stacked residual ratio method to evaluate the
cross-calibration uncertainties between the instruments as a function
of energy. Our work is an extension to a previous one using X-ray
clusters by the International Astronomical Consortium for High Energy
Calibration (IACHEC) and is carried out in the context of IACHEC.
Performing spectral fitting in the full energy band, (0.7-7)keV, as is
typical of the analysis of cluster spectra, we find that best-fit
temperatures determined with XMM-Newton/EPIC are significantly lower
than Chandra/ACIS temperatures. This confirms the previous IACHEC
results obtained with older calibrations with high precision. The
difference increases with temperature, and we quantify this dependence
with a fitting formula. For instance, at a cluster temperature of
10keV, EPIC temperatures are on average 23% lower than ACIS
temperatures. We also find systematic differences between the three
XMM-Newton/EPIC instruments, with the PN detector typically estimating
the lowest temperatures. Testing the cross-calibration of the
energy-dependence of the effective areas in the soft and hard energy
bands, (0.7-2)keV and (2-7)keV, respectively, we confirm the
previously indicated relatively good agreement between all instruments
in the hard and the systematic differences in the soft band. We
provide scaling relations to convert between the different instruments
based on the effective area, gas temperature, and hydrostatic mass. We
demonstrate that effects like multitemperature structure and different
relative sensitivities of the instruments at certain energy bands
cannot explain the observed differences. We conclude that using
XMM-Newton/EPIC instead of Chandra/ACIS to derive full energy band
temperature profiles for cluster mass determination results in an 8%
shift toward lower ΩM values and <1% change of σ8
values in a cosmological analysis of a complete sample of galaxy
clusters. Such a shift alone is insufficient to significantly
alleviate the tension between Planck CMB primary anisotropies and
Sunyaev-Zel'dovich-plus-XMM-Newton cosmological constraints.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 74 63 63 HIFLUGCS clusters (without Abell 2244)
tablea2.dat 91 63 *Best-fit temperatures and 68% confidence levels
for the 4 different detectors (plus EPIC
combined) in the (0.7-7)keV band
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Note on tablea2.dat: The annulus region was used for cool-core clusters.
For details on the excluded spectra, see Sect. 2.
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Cluster Cluster name as used in the paper
10- 17 F8.4 deg RAdeg Right ascension (J2000) (1)
19- 26 F8.4 deg DEdeg Declination (J2000) (1)
28- 33 F6.4 --- z [0.0037/0.22] Redshift (2)
35- 38 F4.2 10+21/cm2 NH Hydrogen column density (2)
40- 45 F6.2 kpc r.cc ?=0 Radius of the cool core region for CC
(Cool Core) clusters only (details in Sect.2)
47- 51 I5 --- ObsIDC [319/14024] Chandra obsid used
52 A1 --- n_ObsIDC [*] * marks Chandra/ACIS-S observations
54- 63 I010 --- ObsIDX [2960101/674560201] XMM obsid used
65- 69 F5.1 ks tACIS [9/135] Cleaned exposure time for Chandra/ACIS
71- 74 F4.1 ks tPN [2/80] Cleaned exposure time for XMM/EPIC-PN
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Note (1): as defined in Hudson et al. (2010A&A...513A..37H 2010A&A...513A..37H).
Note (2): both from Zhang et al. (2011A&A...526A.105Z 2011A&A...526A.105Z), except for Abell 478,
Abell 2163, and Abell 3571, see Sect. 2.
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Byte-by-byte Description of file: tablea2.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Cluster Cluster name
10- 14 F5.2 keV kT.C [1.5/11.8]? Chandra-ACIS temperature kT
16- 19 F4.2 keV E_kT.C ? Error on kT.C (upper value)
21- 24 F4.2 keV e_kT.C ? Error on kT.C (lower value)
26- 29 F4.2 keV kT.M1 ? XMM-.OS1 temperature kT
31- 34 F4.2 keV E_kT.M1 ? Error on kT.M1 (upper value)
36- 39 F4.2 keV e_kT.M1 ? Error on kT.M1 (lower value)
41- 44 F4.2 keV kT.M2 ? XMM-MOS2 temperature kT
46- 49 F4.2 keV E_kT.M2 ? Error on kT.M2 (upper value)
51- 54 F4.2 keV e_kT.M2 ? Error on kT.M2 (lower value)
56- 59 F4.2 keV kT.PN ? XMM-PN temperature kT
61- 64 F4.2 keV E_kT.PN ? Error on kT.PN (upper value)
66- 69 F4.2 keV e_kT.PN ? Error on kT.PN (lower value)
71- 74 F4.2 keV kT.EP ? XMM-EPIC combined temperature kT
76- 79 F4.2 keV E_kT.EP ? Error on kT.EP (upper value)
81- 84 F4.2 keV e_kT.EP ? Error on kT.EP (lower value)
86- 91 F6.2 --- S/bg ? Ratio of source and background count rates
in the (0.7-2.0)keV band
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 01-Jun-2015