J/MNRAS/465/2616 Galaxy cluster's rotation (Manolopoulou+, 2017)
Galaxy cluster's rotation.
Manolopoulou M., Plionis M.
<Mon. Not. R. Astron. Soc., 465, 2616-2633 (2017)>
=2017MNRAS.465.2616M 2017MNRAS.465.2616M (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, galaxy ; Galaxies, rotation
Keywords: galaxies: clusters: general
Abstract:
We study the possible rotation of cluster galaxies, developing,
testing, and applying a novel algorithm which identifies rotation, if
such does exist, as well as its rotational centre, its axis
orientation, rotational velocity amplitude, and, finally, the
clockwise or counterclockwise direction of rotation on the plane of
the sky. To validate our algorithms we construct realistic Monte Carlo
mock rotating clusters and confirm that our method provides robust
indications of rotation. We then apply our methodology on a sample of
Abell clusters with z≤0.1 with member galaxies selected from
the Sloan Digital Sky Survey DR10 spectroscopic data base. After
excluding a number of substructured clusters, which could provide
erroneous indications of rotation, and taking into account the
expected fraction of misidentified coherent substructure velocities
for rotation, provided by our Monte Carlo simulation analysis, we find
that ∼23 per cent of our clusters are rotating under a set of
strict criteria. Loosening the strictness of the criteria, on the
expense of introducing spurious rotation indications, we find this
fraction increasing to ∼28 per cent. We correlate our rotation
indicators with the cluster dynamical state, provided either by their
Bautz-Morgan type or by their X-ray isophotal shape and find for those
clusters showing rotation within 1.5h-170 Mpc that the
significance of their rotation is related to the dynamically younger
phases of cluster formation but after the initial anisotropic
accretion and merging has been completed. Finally, finding rotational
modes in galaxy clusters could lead to the necessity of correcting the
dynamical cluster mass calculations.
Description:
We searched for possible cluster rotation in a sample of Abell
clusters using galaxy-member redshifts from the SDSS DR10
spectroscopic data base. We developed a new algorithm in order to be
able to deduce rotation using the line-of-sight velocities of the
galaxy members. We verified the performance of this algorithm by
applying it on various Monte Carlo simulated clusters with known
rotational characteristics.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 35 103 The Abell clusters of our sample
table4.dat 92 18 *The clusters with significant rotation within
r=1.5h-170Mpc and with Nmem≥50
table5.dat 92 24 *The clusters with significant rotation within
r=2.5h-170Mpc and with Nmem≥50
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Note on table4.dat, table5.dat: using either the strict or loose criteria of
rotation detection.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- ACO Cluster Abell number
6- 11 F6.4 --- z Redshift
13- 19 F7.3 deg RAdeg Right ascension (J2000)
21- 28 F8.4 deg DEdeg Declination (J2000)
30- 32 F3.1 --- BM ?=- BM type
34- 35 I2 --- N* Measure of the cluster richness (1)
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Note (1): measure of the cluster richness, provided by the number of bright
(M>M*) members within the 1.5h-170Mpc radius.
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Byte-by-byte Description of file: table4.dat table5.dat
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Bytes Format Units Label Explanations
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1 A1 --- Crit [SL] Strict (S) or loose (L) criteria (2)
3- 6 I4 --- ACO Cluster Abell name
7 A1 --- m_ACO [ab] Multiplicity index on ACO
8 A1 --- n_ACO [*] Note on ACO (1)
10- 16 F7.5 --- z Mean redshift of the members
18- 20 I3 --- Nmem Number of members used
22- 24 I3 deg thetarot Orientation on the plane of the sky of the
rotation axis
26- 28 I3 km/s vrot Rotation amplitude
30- 32 I3 km/s e_vrot rms uncertainty on rotation amplitude
34- 43 F10.6 deg RAcdeg Right ascension of chosen rotation
centre (J2000)
45- 54 F10.6 deg DEcdeg Declination of chosen rotation
centre (J2000)
56- 63 F8.6 --- PKS Minimum value of the KS probability (2)
65- 69 F5.3 --- chi2id/df chi2_id/df (2)
71- 75 F5.3 --- chi2r/df chi2_r/df (2)
77- 81 F5.3 --- chi2id/chi2r chi2id/chi2_r (2)
83 I1 --- I [1/2] Indication for the direction of
rotation (1 meaning clockwise and
2 anticlockwise) (3)
85- 88 I4 km/s sigma Initial cluster velocity dispersion
90- 92 I3 km/s sigmac Corrected, for rotation, cluster velocity
dispersion
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Note (1): * for clusters that show significant rotation only when excluding
the inner cluster core (<0.3h-170Mpc)
Note (2): Criteria that can be used to deduce a significant or not cluster
rotation, which we call the strict criteria, and are as follows:
PKS : PKS, between the galaxy relative velocity distributions of the
two semicircles of maximum difference, which should be PKS<0.01
chi2id/df : between the real and ideal rotation curve, which should be
less or equal to 1 for a rotating cluster
chi2r/df : between the real rotation curve and random curve, which should
be >1 for a rotating cluster
chi2id/chi2r : which should be ideally ≪1 for a rotating cluster, but
practically we take it to be ≤0.2
These criteria can be relaxed to provide a less secure identification of
rotation. For example, we also checked for clusters fulfilling only the
following two criteria: chi2id/chi2r<0.4 and PKS<0.01.
We call these the loose criteria for cluster rotation.
Note (3): indication for the direction of rotation as follows;
1 = clockwise
2 = anticlockwise
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 19-Nov-2018