2006MNRAS.370...25S


C.D.S. - SIMBAD4 rel 1.7 - 2020.10.21CEST04:05:54

2006MNRAS.370...25S - Mon. Not. R. Astron. Soc., 370, 25-42 (2006/July-3)

The X-ray properties of the dwarf Magellanic-type galaxy NGC 55.

STOBBART A.-M., ROBERTS T.P. and WARWICK R.S.

Abstract (from CDS):

We present an analysis of the X-ray properties of the Magellanic-type galaxy NGC 55 based on two contiguous XMM-Newton observations. We detect a total of 137 X-ray sources in the field of view, down to a flux of ∼5 x10–15erg.cm–2.s–1 (0.3-6 keV), 42 of which are located within the optical confines of the galaxy. On the basis of X-ray colour classification and after correcting for background objects, we conclude that our source sample includes ∼20 X-ray binaries (XRBs), five supernova remnants and seven very soft sources (including two good candidate supersoft sources) associated with NGC 55. We also detect an X-ray source coincident with a previously identified globular cluster in NGC 55. Detailed spectral and timing analysis was carried out on four of the brightest X-ray sources (excluding the brightest source, which was the subject of a previous paper). One of these objects is identified with a Galactic foreground star and is a possible new RS CVn system. The other three are persistent X-ray sources with X-ray spectra well described by either a single absorbed power law (Γ ∼ 2) or a multicolour disc blackbody (kT≲1keV) model. While the observed luminosities of these sources (LX∼ 1-2x1038erg.s–1) and their X-ray spectra are consistent with accreting XRBs, further evidence of short-term variability is required to confirm this. Although the observed X-ray emission from NGC 55 is dominated by point sources, we do find evidence of an underlying component, which is concentrated on the bar region but has an extent of at least 6 arcmin (3 kpc) in the plane of the galaxy and ±1 arcmin (±500 pc) perpendicular to it. This emission is best fitted by a thermal plasma (mekal) (kT ∼ 0.2 keV) plus power-law (Γ ∼ 2) model but with high intrinsic absorption consistent with its location in the central disc of the galaxy. We interpret the soft component as diffuse thermal emission linked to regions of current star formation, whilst the hard power-law component may originate in unresolved X-ray binary sources. The intrinsic luminosity of this residual disc emission may exceed LX∼ 6x1038erg.s–1 (0.3-6 keV). A comparison with other Magellanic systems confirms that, in terms of both its discrete X-ray source population and its extended emission, NGC 55 has X-ray properties which are typical of its class.

Abstract Copyright: 2006 The Authors. Journal compilation © 2006 RAS

Journal keyword(s): galaxies: individual: NGC 55 - galaxies: Magellanic Clouds - X-rays: binaries - X-rays: galaxies

VizieR on-line data: <Available at CDS (J/MNRAS/370/25): table2.dat>

Nomenclature: Table 2: [SRW2006] NNN (Nos 1-137).

Status at CDS : All or part of tables of objects could be ingested in SIMBAD with priority 2.

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 NGC 45 LSB 00 14 03.989 -23 10 55.53 11.92 11.21 10.73 10.58 10.4 ~ 228 1
2 V* UY Scl RR* 00 14 45.7519693501 -39 14 35.567831721   12.44 11.53     ~ 21 0
3 NGC 55 GiG 00 14 53.602 -39 11 47.86 8.54 8.58 7.87 7.84   ~ 712 2
4 [BWE2015] NGC 55 119 ULX 00 15 28.89 -39 13 18.8           ~ 40 0
5 M 31 G 00 42 44.330 +41 16 07.50 4.86 4.36 3.44     ~ 11051 1
6 NGC 247 LSB 00 47 08.554 -20 45 37.44 10.11 9.61 9.10 8.87   ~ 376 2
7 NGC 253 SyG 00 47 33.134 -25 17 19.68   8.03   6.94 8.1 ~ 2954 2
8 NGC 300 GiG 00 54 53.4460065856 -37 41 03.182962667 8.83 8.69 8.13 7.46   ~ 1328 2
9 NAME Scl Group GrG 01 00 06 -33 44.2           ~ 465 0
10 M 33 GiG 01 33 50.904 +30 39 35.79 6.17 6.27 5.72     ~ 5191 1
11 NAME Magellanic Clouds GrG 03 00 -71.0           ~ 5757 1
12 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 14988 1
13 NGC 4449 EmG 12 28 11.118 +44 05 36.81 10.11 9.98 9.64 9.45   ~ 1027 1
14 NGC 4697 GiG 12 48 35.8992791100 -05 48 02.497675635   10.97   9.83   ~ 806 0
15 M 51 GiP 13 29 52.698 +47 11 42.93   9.26 8.36 8.40   ~ 3833 4
16 M 83 SBG 13 37 00.919 -29 51 56.74 8.85 8.11 7.52 7.21   ~ 2249 2
17 M 101 GiP 14 03 12.583 +54 20 55.50   8.46 7.86 7.76   ~ 2576 2
18 NGC 7793 GiG 23 57 49.7533807411 -32 35 27.708304655 10.26 9.74 9.28 9.06 9.7 ~ 936 2

    Equat.    Gal    SGal    Ecl

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2020.10.21-04:05:54

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