2018A&A...619A.162X


C.D.S. - SIMBAD4 rel 1.7 - 2020.08.04CEST22:05:00

2018A&A...619A.162X - Astronomy and Astrophysics, volume 619A, 162-162 (2018/11-1)

A new X-ray-selected sample of very extended galaxy groups from the ROSAT All-Sky Survey.

XU W., RAMOS-CEJA M.E., PACAUD F., REIPRICH T.H. and ERBEN T.

Abstract (from CDS):


Context. Some indications for tension have long been identified between cosmological constraints obtained from galaxy clusters and primary cosmic microwave background (CMB) measurements. Typically, assuming the matter density and fluctuations, as parameterized with Ωm and σ8, estimated from CMB measurements, many more clusters are expected than those actually observed. This has been reinforced recently by the Planck collaboration. One possible explanation could be that certain types of galaxy groups or clusters were missed in samples constructed in previous surveys, resulting in a higher incompleteness than estimated.
Aims. In this work, we aim to determine if a hypothetical class of very extended, low-surface-brightness galaxy groups or clusters have been missed in previous X-ray cluster surveys based on the ROSAT All-Sky Survey (RASS).
Methods. We applied a dedicated source-detection algorithm sensitive also to more unusual group or cluster surface-brightness distributions. It includes a multiresolution filtering, a source-detection algorithm, and a maximum-likelihood fitting procedure. To optimize parameters, this algorithm is calibrated using extensive simulations before it is used to reanalyze the RASS data. In addition, the cross-correlation of the candidates with optical/infrared surveys is used for cluster identification and redshift estimation.
Results. We found many known groups but also a number of new group candidates, which are not included in any previous X-ray or SZ cluster catalogs. In this paper, we present a pilot sample of 13 very extended groups discovered in the RASS at positions where no X-ray source has been detected previously and with clear optical counterparts. The X-ray fluxes of at least 5 of these are above the nominal flux-limits of previous RASS cluster catalogs (≥3x10–12erg/s/cm2 in the 0.1-2.4keV energy band). They have low mass (1013M≤M500≤1014M; i.e., they are galaxy groups), are at low redshift (z<0.08), and exhibit flatter surface-brightness distributions than usual.
Conclusions. We demonstrate that galaxy groups were missed in previous RASS surveys, possibly due to the flat surface-brightness distributions of this potential new population. Analysis of the full sample will show if this might have a significant effect on previous cosmological parameter constraints based on RASS cluster surveys.

Abstract Copyright: © ESO 2018

Journal keyword(s): galaxies: clusters: general - galaxies: groups: general - galaxies: clusters: intracluster medium - large-scale structure of Universe - X-rays: galaxies: clusters

Status at CDS:   Examining the need for a new acronym.

CDS comments: Objects MSPM NNNNN not in SIMBAD.

Simbad objects: 18

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Number of rows : 18

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 USGC S061 GrG 01 36 29.7 -13 56 16           ~ 3 0
2 CAN 15 ClG 02 25.6 +36 57           ~ 8 0
3 USGC U118 GrG 02 25 36.9 +37 07 24           ~ 2 0
4 USGC U142 GrG 02 40 58.1 +08 43 30           ~ 2 0
5 NGC 1044 GiG 02 41 06.183 +08 44 16.72   14.8       ~ 61 1
6 NAME Magellanic Clouds GrG 03 00 -71.0           ~ 5691 1
7 [CPV2011] GRPM2 1204 GrG 10 49 53 +00 11.9           ~ 2 0
8 SDSS-C4 1156 ClG 10 49 58.854 +00 19 20.31           ~ 7 0
9 NAME Vir I ClG 12 26 32.1 +12 43 24   10.00 8.49     ~ 5839 0
10 NAME SHAPLEY-CENTAURUS CL SCG 13 06.0 -33 04           ~ 502 0
11 ACO 1736 ClG 13 26 52.1 -27 06 33           ~ 238 2
12 ACO S 736 ClG 13 30 59 -28 02.4           ~ 5 0
13 HCG 67 CGG 13 49 03.5 -07 12 20           ~ 51 0
14 ACO 2152 ClG 16 05 22.4 +16 26 55           ~ 153 0
15 NAME NEP reg 18 00 00.000 +66 33 38.55           ~ 256 0
16 ACO 3742 ClG 21 06 41 -47 08.9           ~ 42 2
17 ACO S 924 ClG 21 07 53 -47 10.9           ~ 2 0
18 WBL 704 ClG 23 17.5 +29 01           ~ 2 0

    Equat.    Gal    SGal    Ecl

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2020.08.04-22:05:00

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