2004A&A...428..867G


Query : 2004A&A...428..867G

2004A&A...428..867G - Astronomy and Astrophysics, volume 428, 867-875 (2004/12-4)

RXJ1821.6+6827: A cool cluster at z=0.81 from the ROSAT NEP survey.

GIOIA I.M., WOLTER A., MULLIS C.R., HENRY J.P., BOEHRINGER H. and BRIEL U.G.

Abstract (from CDS):

We present an analysis of the properties of the cluster of galaxies RX J1821.6+6827, or NEP5281, at a redshift z=0.816 ±0.001. RX J1821.6+6827 was discovered during the optical identification of the X-ray sources in the North Ecliptic Pole (NEP) region of the ROSAT All-Sky Survey and it is the highest redshift cluster of galaxies of the NEP survey. We have measured spectroscopic redshifts for twenty cluster galaxies using the Keck-I and the Canada-France-Hawai'i (CFH) telescopes. The value for the cluster velocity dispersion is σV=775+182–113km/s. The cluster was also observed by XMM-Newton. Both the optical and X-ray data are presented in this paper. The cluster has an unabsorbed X-ray flux in the 2-10keV energy band of F2–10keV=1.24+0.16–0.23x10–13erg/cm2/s and a K-corrected luminosity in the same band of L_2-10 keV=6.32-0.73+0.76x1044h-2^50erg/s (90% confidence level). The cluster X-ray bolometric luminosity is LBOL,X=1.35+0.08–0.21x1045h50–2erg/s (LBOL,X=1.17+0.13–0.18x1045h70–2erg/s in the concordance cosmology). The data do not allow fitting both metal abundance and temperature at the same time. The abundance is unconstrained and can vary in the range 0.28-1.42Z while the best fit X-ray temperature is T=4.7+1.2–0.7keV. This emission weighted X-ray temperature is a little lower, barely within the uncertainties, than the predicted temperature, T=6.34+0.13–0.35keV, from the LX-TX relation of local clusters published in the literature. The optically measured velocity dispersion is consistent with the velocity dispersion expected from the σV-TX relationship. We also examine the point X-ray source RX J1821.9+6818, or NEP5330, located to the south east of the cluster which was identified as a QSO at z=1.692±0.008 in the ROSAT NEP survey. The X-ray source is well fitted by an absorbed power law model with NH=4.1–3.0+3.1x1020atoms/cm2 and a photon index Γ=1.67±0.12 typical of an active galactic nucleus.

Abstract Copyright:

Journal keyword(s): galaxies: clusters: general - galaxies: clusters: individual: RX J1821.6+6827 - X-rays: general - X-rays: individual: RX J1821.6+6827 - X-rays: galaxies: clusters - galaxies: intergalactic medium

Nomenclature: Table 1: [GWM2004b] NN (Nos 1-20).

Simbad objects: 25

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Number of rows : 25
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
#notes
1 ClG 1054-03 ClG 10 57 00.2 -03 37 27     22     ~ 454 0
2 ClG J1716+6708 ClG 17 16 49.6 +67 08 30           ~ 134 0
3 NAME NEP reg 18 00 00.000 +66 33 38.55           ~ 352 0
4 [GWM2004b] 1 GiC 18 21 16.6 +68 30 25           ~ 1 0
5 [GWM2004b] 15 GiC 18 21 18.2 +68 27 00           ~ 1 0
6 [GWM2004b] 2 GiC 18 21 21.5 +68 29 57           ~ 1 0
7 [GWM2004b] 3 GiC 18 21 26.2 +68 29 31           ~ 1 0
8 [GWM2004b] 5 GiC 18 21 27.9 +68 28 43           ~ 1 0
9 [GWM2004b] 4 AGN 18 21 30.8 +68 29 29           ~ 2 0
10 [GWM2004b] 7 GiC 18 21 32.6 +68 27 54           ~ 1 0
11 ClG 1821+6827 ClG 18 21 33 +68 27.9           ~ 31 0
12 [GWM2004b] 10 GiC 18 21 33.6 +68 27 50           ~ 1 0
13 [GWM2004b] 6 GiC 18 21 33.8 +68 28 40           ~ 1 0
14 [GWM2004b] 8 GiC 18 21 34.9 +68 27 53           ~ 1 0
15 [GWM2004b] 11 GiC 18 21 35.2 +68 27 34           ~ 1 0
16 [GWM2004b] 12 GiC 18 21 36.6 +68 27 21           ~ 1 0
17 [GWM2004b] 9 AGN 18 21 37.2 +68 27 51           ~ 2 0
18 [GWM2004b] 13 GiC 18 21 37.5 +68 27 07           ~ 1 0
19 [GWM2004b] 14 GiC 18 21 37.9 +68 27 00           ~ 1 0
20 [GWM2004b] 16 GiC 18 21 47.7 +68 27 06           ~ 1 0
21 [GWM2004b] 20 GiC 18 21 47.8 +68 25 18           ~ 1 0
22 [GWM2004b] 19 GiC 18 21 50.8 +68 26 09           ~ 1 0
23 [GWM2004b] 17 GiC 18 21 51.1 +68 27 17           ~ 1 0
24 [GWM2004b] 18 GiC 18 21 57.7 +68 27 25           ~ 1 0
25 7C 182212.59+681701.00 QSO 18 21 59.49167990 +68 18 43.0088715           ~ 27 1

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