J/A+A/636/A15 X-ray galaxy cluster sample (Migkas+, 2020)
Probing cosmic isotropy with a new X-ray galaxy cluster sample through the
LX-T scaling relation.
Migkas K., Schellenberger G., Reiprich T.H., Pacaud F., Ramos-ceja M.E.,
Lovisari L.
<Astron. Astrophys., 636, A15 (2020)>
=2020A&A...636A..15M 2020A&A...636A..15M (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, galaxy ; X-ray sources
Keywords: cosmology: observations - X-rays: galaxies: clusters -
large-scale structure of Universe - galaxies: clusters: general -
methods: statistical - catalogs
Abstract:
The isotropy of the late Universe and consequently of the X-ray galaxy
cluster scaling relations is an assumption greatly used in astronomy.
However, within the last decade, many studies have reported deviations
from isotropy when using various cosmological probes; a definitive
conclusion has yet to be made. New, effective and independent methods
to robustly test the cosmic isotropy are of crucial importance. In
this work, we use such a method. Specifically, we investigate the
directional behavior of the X-ray luminosity-temperature (LX-T)
relation of galaxy clusters. A tight correlation is known to exist
between the luminosity and temperature of the X-ray-emitting
intracluster medium of galaxy clusters. While the measured luminosity
depends on the underlying cosmology through the luminosity distance
DL, the temperature can be determined without any cosmological
assumptions. By exploiting this property and the homogeneous sky
coverage of X-ray galaxy cluster samples, one can effectively test the
isotropy of cosmological parameters over the full extragalactic sky,
which is perfectly mirrored in the behavior of the normalization A of
the LX-T relation. To do so, we used 313 homogeneously selected
X-ray galaxy clusters from the Meta-Catalogue of X-ray detected
Clusters of galaxies. We thoroughly performed additional cleaning in
the measured parameters and obtain core-excised temperature
measurements for all of the 313 clusters. The behavior of the LX-T
relation heavily depends on the direction of the sky, which is
consistent with previous studies. Strong anisotropies are detected at
a≥4σ confidence level toward the Galactic coordinates
(l, b)~(280°, -20°), which is roughly consistent with the
results of other probes, such as Supernovae Ia. Several effects that
could potentially explain these strong anisotropies were examined.
Such effects are, for example, the X-ray absorption treatment, the
effect of galaxy groups and low redshift clusters, core metallicities,
and apparent correlations with other cluster properties, but none is
able to explain the obtained results. Analyzing 105 bootstrap
realizations confirms the large statistical significance of the
anisotropic behavior of this sky region. Interestingly, the two
cluster samples previously used in the literature for this test appear
to have a similar behavior throughout the sky, while being fully
independent of each other and of our sample. Combining all three
samples results in 842 different galaxy clusters with luminosity and
temperature measurements. Performing a joint analysis, the final
anisotropy is further intensified (∼5σ), toward
(l, b)~(303°, -27°), which is in very good agreement with
other cosmological probes. The maximum variation of DL seems to be
∼16±3% for different regions in the sky. This result demonstrates
that X-ray studies that assume perfect isotropy in the properties of
galaxy clusters and their scaling relations can produce strongly
biased results whether the underlying reason is cosmological or
related to X-rays. The identification of the exact nature of these
anisotropies is therefore crucial for any statistical cluster physics
or cosmology study.
Description:
The cluster sample used in this work is a homogeneously selected one
based on the Meta-Catalogue of X-ray detected Clusters of galaxies
(MCXC, Piffaretti et al., 2011, Cat. J/A+A/534/A109).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablec1.dat 119 313 Properties of the 313 clusters used in this work
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See also:
J/A+A/534/A109 : MCXC Meta-Catalogue X-ray galaxy Clusters (Piffaretti+, 2011)
Byte-by-byte Description of file: tablec1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 16 A16 --- Cluster Cluster name
17- 19 A3 --- Note [* ] Note (1)
22- 26 F5.3 --- z Redshift
28- 34 F7.3 deg GLON Galactic longitude
36- 42 F7.3 deg GLAT Galactic latitude
44- 49 F6.3 keV T Temperature within 0.2-9.5R500
52- 56 F5.3 keV E_T Error on T, upper value
59- 63 F5.3 keV e_T Error on T, lower value
65- 70 F6.3 10+35W LX X-ray luminosity within R500 for the
0.1-2.4keV energy range
72- 75 F4.1 % e_LX Error on LX
77- 82 F6.2 10-15W/m2 FX X-ray flux 10-15W/m2
84- 88 F5.2 10+20cm-2 NHtot Neutral + molecular hydrogen column density
90- 94 F5.3 -- Z Metal abundance within 0.2-0.5R500
97-101 F5.3 --- E_Z Error on Z, upper value
104-108 F5.3 --- e_Z Error on Z, lower value
110-119 A10 --- Inst Instrument used for analysis
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Note (1): Notes as follows:
* = X-ray redshifts noted
** = redetermined redshifts based on optical spectroscopic data noted
*** = clusters for which their luminosities were found based on
redshift-independent methods
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 16-Jun-2020