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1.
We show how future measurements of the Sunyaev–Zel'dovich effect (SZE) can be used to constrain the cosmological parameters. We combine the SZ information expected from the Planck full-sky survey, N ( S ), where no redshift information is included, with the N ( z ) obtained from an optically identified SZ-selected survey covering less than 1 per cent of the sky. We demonstrate how with a small subsample (≈300 clusters) of the whole SZ catalogue observed optically it is possible to reduce the degeneracy among the cosmological parameters drastically. We have studied the requirements for performing the optical follow-up and we show the feasibility of such a project. Finally, we have compared the cluster expectations for Planck with those expected for Newton–XMM during their lifetimes. It is shown that, owing to its larger sky coverage, Planck will detect a factor of ∼5 times more clusters than Newton–XMM and also provide a larger redshift coverage.  相似文献   

2.
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3.
To investigate the transient nature of supersoft sources (SSSs) in M 31, we compared SSS candidates ofthe XMM‐Newton Deep Survey, ROSAT PSPC surveys and the Chandra catalogues in the same field. We found 40 SSSs in the XMM‐Newton observations. While 12 of the XMM‐Newton sources were brighter than the limiting flux of the ROSAT PSPC survey, only two were detected with ROSAT ∼10 yr earlier. Five correlate with recent optical novae which explains why they were not detected by ROSAT. The remaining 28 XMM‐Newton SSSs have fluxes below the ROSAT detection threshold. Nevertheless we found one correlation with a ROSAT source, which had significantly larger fluxes than during the XMM‐Newton observations. Ten of the XMM‐Newton SSSs were detected by Chandra with <1– ∼6yr between the observations. Five were also classified as SSSs by Chandra. Of the 30 ROSAT SSSs three were confirmed with XMM‐Newton, while for 11 sources other classifications are suggested. Of the remaining 16 sources one correlates with an optical nova. Of the 42 Chandra very‐soft sources five are classified as XMM‐Newton SSSs, while for 22 we suggest other classifications. Of the remaining 15 sources, nine are classified as transient by Chandra, one of them correlates with an optical nova. These findings underlined the high variability of the sources of this class and the connection between SSSs and optical novae. Only three sources, were detected by all three missions as SSSs. Thus they are visible for more than a decade, despite their variability (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

4.
With detections of the Sunyaev–Zel'dovich (SZ) effect induced by galaxy clusters becoming routine, it is crucial to establish accurate theoretical predictions. We use a hydrodynamical N -body code to generate simulated maps, of size 1 deg2, of the thermal SZ effect. This is done for three different cosmologies: the currently favoured low-density model with a cosmological constant, a critical-density model and a low-density open model. We stack simulation boxes corresponding to different redshifts in order to include contributions to the Compton y -parameter out to the highest necessary redshifts. Our main results are as follows.
(i) The mean y -distortion is around 4×10−6 for low-density cosmologies, and 1×10−6 for critical density. These are below current limits, but not by a wide margin in the former case.
(ii) In low-density cosmologies, the mean y -distortion is contributed across a broad range of redshifts, with the bulk coming from z ≲2 and a tail out to z ∼5. For critical-density models, most of the contribution comes from z <1.
(iii) The number of SZ sources above a given y depends strongly on instrument resolution. For a 1-arcmin beam, there are around 0.1 sources per deg2 with y >10−5 in a critical-density Universe, and around 8 such sources per deg2 in low-density models. Low-density models with and without a cosmological constant give very similar results.
(iv) We estimate that the Planck satellite will be able to see of order 25 000 SZ sources if the Universe has a low density, or around 10 000 if it has critical density.  相似文献   

5.
We examine the ability of the future Planck mission to provide a catalogue of galaxy clusters observed via their Sunyaev–Zel'dovich (SZ) distortion in the cosmic microwave background (CMB). For this purpose we produce full-sky SZ maps based on N -body simulations and scaling relations between cluster properties for several cosmological models. We extrapolate the N -body simulations by a mass function to high redshifts in order to obtain a realistic SZ background. The simulated Planck observations include, besides the thermal and kinematic SZ effects, contributions from the primordial CMB, extragalactic point sources as well as Galactic dust, free–free and synchrotron emission. A harmonic-space maximum-entropy method is used to separate the SZ signal from contaminating components in combination with a cluster detection algorithm based on thresholding and flux integration to identify clusters and to obtain their fluxes. We estimate a survey sensitivity limit (depending on the quality of the recovered cluster flux) and provide cluster survey completeness and purity estimates. We find that, given our modelling and detection algorithm, Planck will reliably detect at least several thousands of clusters over the full sky. The exact number depends on the particular cosmological model (up to 10 000 cluster detections in a concordance ΛCDM model with  σ8= 0.9  ). We show that the Galaxy does not significantly affect the cluster detection. Furthermore, the dependence of the thermal SZ power spectrum on the matter variance on scales of  8 h −1  Mpc and the quality of its reconstruction by the employed method are investigated. Our simulations suggest that the Planck cluster sample will not only be useful as a basis for follow-up observations, but also will have the ability to provide constraints on cosmological parameters.  相似文献   

6.
First studies of the X‐ray source population of M 31 were performed with the Einstein Observatory and ROSAT. High resolution Chandra Observatory images not only spatially resolved the center area but also supernova remnants (SNRs) in the galaxy. Source catalogues of restricted areas were presented with high astrometric accuracy. Also luminosity function studies and studies of individual sources based on Chandra and XMM‐Newton observations led to a better knowledge of the X‐ray source population. An XMM‐Newton source catalog based on archival observations revealed more than 850 sources down to a 0.2–4.5 keV luminosity of 1035 erg s–1. EPIC hardness ratios as well as informations from earlier X‐ray, optical, and radio catalogues were used to distinguish between different source classes (SNRs, supersoft sources (SSSs), X‐ray binaries (XRBs), globular cluster sources within M 31, and foreground stars and objects in the background). However, many sources could only be classified as “hard”. These sources may either be XRBs or Crab‐like SNRs in M 31 or background sources. Two of the globular cluster sources could be identified as low mass XRBs with a neutron star as compact object as they showed type I X‐ray bursts. Many of the SSSs were identified as optical novae. Inspired by these results an XMM‐Newton survey of the entire D25 disk of M 31 and a dedicated program to monitor X‐ray counterparts of optical novae in M 31 was started. We discuss implications for further nearby galaxy studies. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

7.
Active galaxies     
In this paper I will review, in an unavoidably incomplete and biased way, the main results obtained by XMM‐Newton on Active Galactic Nuclei. I will then highlight the major issues still open in which XMM‐Newton can still give important contributions, expecially if the observing programs will shift in the future towards more long exposures of single objects and observations of large samples. I will also argue in favour of a legacy program consisting of good S/N observations of a flux‐limited, sizeable sample of AGN. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

8.
This paper shows that our understanding of the statistical properties of X‐ray selected normal galaxies (e.g. X‐ray luminosity function) can be significantly improved by combining a wide‐area XMM‐Newton survey with the moderare resolution and high S/N optical spectroscopy of the SDSS. Such a combined dataset has the potential to minimise uncertainties that affect existing normal galaxy samples at X‐rays, such as small number statistics, cosmic variance, AGN contamination and incompleteness at bright X‐ray luminosities. It is demonstrated that a 100 deg2 XMM‐Newton survey in the SDSS area to the limit fX(0.5–2 keV) ≈ 5 × 10–15 erg cm–2 s–1 will detect over 400 X‐ray selected normal galaxies with excellent control over systematic biases, thereby providing tight contraints on the X‐ray luminosity function at z ≈ 0.1. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

9.
We review some recent results on the identification and characterisation of Active Galactic Nuclei (AGN) obtained by cross correlating X‐ray surveys with infrared and submillimetre surveys. We also look toward the scientific gains that could be achieved from an XMM‐Newton survey of the medium‐deep legacy fields that are being observed at ≈ 1–850 μm. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

10.
The Planck mission is the most sensitive all-sky cosmic microwave background (CMB) experiment currently planned. The High-Frequency Instrument (HFI) will be especially suited for observing clusters of galaxies by their thermal Sunyaev–Zel'dovich (SZ) effect. In order to assess Planck 's SZ capabilities in the presence of spurious signals, a simulation is presented that combines maps of the thermal and kinetic SZ effects with a realization of the CMB, in addition to Galactic foregrounds (synchrotron emission, free–free emission, thermal emission from dust, CO-line radiation) as well as the submillimetric emission from celestial bodies of our Solar system. Additionally, observational issues such as the finite angular resolution and spatially non-uniform instrumental noise of Planck 's sky maps are taken into account, yielding a set of all-sky flux maps, the autocorrelation and cross-correlation properties of which are examined in detail. In the second part of the paper, filtering schemes based on scale-adaptive and matched filtering are extended to spherical data sets, that enable the amplification of the weak SZ signal in the presence of all contaminations stated above. The theory of scale-adaptive and matched filtering in the framework of spherical maps is developed, the resulting filter kernel shapes are discussed and their functionality is verified.  相似文献   

11.
We present a sample of eight extended X-ray sources detected in the wide-field (∼2.3 deg2), bright (2–10 ks) XMM–Newton /2dF survey, reaching a flux limit of  ∼2 × 10−14 erg s−1 cm−2  . Of these, seven are identified as secure X-ray clusters in the soft 0.3–2 keV band using a standard wavelet algorithm on either the PN or the MOS images. Spectroscopic or photometric redshifts are available for five clusters, spanning a range between 0.12 and 0.68. The X-ray spectral fittings show temperatures between 1 and 4.6 keV, characteristic of poor clusters and groups of galaxies. We derive for the first time the XMM–Newton cluster number count  log  N –log  S   distribution albeit with poor statistics. Both the  log  N –log  S   and the luminosity–temperature relation are in good agreement with previous ROSAT results.  相似文献   

12.
The well defined selection function of the XMM‐LSS surveys enables a simultaneous modelling of the observed cluster number counts and of the evolution of the LX‐TX relation. We present results pertaining to the first 5 deg2 for a well controlled sample comprising 30 objects: they are compatible with the WMAP3 parameter set along with cluster selfsimilar evolution. Extending such a survey to 200 deg2 would (1) allow discriminating between the major scenarios of the cluster LX‐TX evolution and (2) provide a unique self‐sufficient determination of σ8 and Γ with an accuracy of ∼5% and 10% respectively, when adding mass information from weak lensing and S‐Z observations. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

13.
We present XMM data for the supercluster A901/2, at   z ∼ 0.17  , which is combined with deep imaging and 17-band photometric redshifts (from the COMBO-17 survey), two degree field (2dF) spectra and Spitzer 24 μm data, to identify active galactic nuclei (AGN) in the supercluster. The 90 ksec XMM image contains 139 point sources, of which 11 are identified as supercluster AGN with   L X(0.5−7.5 keV) > 1.7 × 1041 erg cm−2 s−1  . The host galaxies have   M R < −20  and only two of eight sources with spectra could have been identified as AGN by the detected optical emission lines. Using a large sample of 795 supercluster galaxies, we define control samples of massive galaxies with no detected AGN. The local environments of the AGN and control samples differ at ≳98 per cent significance. The AGN host galaxies lie predominantly in areas of moderate projected galaxy density and with more local blue galaxies than the control sample, with the exception of one very bright type I AGN very near the centre of a cluster. These environments are similar to, but not limited to, cluster outskirts and blue groups. Despite the large number of potential host galaxies, no AGN are found in regions with the highest galaxy density (excluding some cluster cores where emission from the intra-cluster medium obscures moderate luminosity AGN). AGN are also absent from the areas with lowest galaxy density. We conclude that the prevalence of cluster AGN is linked to their environment.  相似文献   

14.
We present an XMM observation of the moderately distant (z=0.41)galaxy cluster CL 0939+4713 (Abell 851), an exceptionally rich cluster. The formation and evolution of clusters depends sensitively on cosmological parameters like the mean matter density in the universe Οm. Therefore it is important to determine the dynamical state of clusters at different redshifts, i.e. at different evolutionary states. The X-ray morphology alone is not the best indicator of the dynamical state, but it should be complemented with all other information available, e.g. the temperature map or the galaxy distribution. The combination of all findings gives a detailed picture of the state of a cluster. This analysis, of this relatively distant cluster, can be used as a basis for comparisons at lower and higher redshifts. The capability of XMM to perform spatially resolved spectroscopy can be used also to determine the distribution of the metal abundances. Not only the overall value of metallicity but also its spatial distribution gives important indications on the metal enrichment processes. The X-ray image shows pronounced substructure. There are two main subclusters which have also some internal structure. This is an indication that the cluster is a dynamically young system. This conclusion is supported by the temperature distribution: a hot region is found between the two main subclusters indicating that the cluster is in the process of a major merger, in which the two subclusters will probably collide in a few hundreds of Myr. The intra-cluster gas of CL 0939+4713 shows variations of the metal abundances. The optically richer subcluster has a somewhat higher metallicity. This finding together with the absence of post-starburst galaxies in this region gives interesting hints on the metal enrichment processes favouring recent enrichment processes like ram-pressure stripping or tidal stripping. Throughout this paper we use H 0 =50 km s-1Mpc-1 and q 0 =0.5; all errors are 90% confidence levels. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

15.
We discuss prospects for cluster detection via the Sunyaev–Zel'dovich (SZ) effect in a blank field survey with the interferometer array, the Arcminute MicroKelvin Imager (AMI). Clusters of galaxies selected in the SZ effect probe cosmology and structure formation with little observational bias, because the effect measures integrated gas pressure directly, and does so independently of cluster redshift.
We use hydrodynamical simulations in combination with the Press–Schechter expression to simulate SZ cluster sky maps. These are used with simulations of the observation process to gauge the expected SZ cluster counts. Even with a very conservative choice of parameters we find that AMI will discover at least several tens of clusters every year with     the numbers depend on factors such as the mean matter density, the density fluctuation power spectrum and cluster gas evolution. The AMI survey itself can distinguish between these to some degree, and parameter degeneracies are largely eliminated given optical and X-ray follow-up of these clusters; this will also permit direct investigation of cluster physics and what drives the evolution.  相似文献   

16.
《Astronomische Nachrichten》2017,338(2-3):256-261
This article provides a summary of XMM ‐Newton highlights on stellar tidal disruption events. First found with ROSAT , ongoing and upcoming sky surveys will detect these events in the thousands. In X‐rays, tidal disruption events (TDEs ) provide us with powerful new probes of accretion physics under extreme conditions and on short timescales and of relativistic effects near the super‐massive black holes (SMBHs) , of the formation and evolution of disk winds near or above the Eddington limit, and of the processes of high‐energy emission from newly launched radio jets. TDEs serve as signposts of the presence of dormant single black holes at the cores of galaxies, and of binary black holes as well, since TDE lightcurves are characteristically different in the latter case. XMM ‐Newton has started to contribute to all of these topics, and a rich discovery space is opening up in the next decade.  相似文献   

17.
We present the K -band (2.2 μm) luminosity functions (LFs) of the X-ray-luminous clusters MS1054–0321 ( z  = 0.823), MS0451–0305 ( z  = 0.55), Abell 963 ( z  = 0.206), Abell 665 ( z  = 0.182) and Abell 1795 ( z  = 0.063) down to absolute magnitudes M K  = −20. Our measurements probe fainter absolute magnitudes than do any previous studies of the near-infrared LFs of clusters. All the clusters are found to have similar LFs within the errors, when the galaxy populations are evolved to redshift z  = 0. It is known that the most massive bound systems in the Universe at all redshifts are X-ray-luminous clusters. Therefore, assuming that the clusters in our sample correspond to a single population seen at different redshifts, the results here imply that not only had the stars in present-day ellipticals in rich clusters formed by z  = 0.8, but that they existed in as luminous galaxies then as they do today.   Additionally, the clusters have K -band LFs which appear to be consistent with the K -band field LF in the range −24 <  M K  < −22, although the uncertainties in both the field and cluster samples are large.  相似文献   

18.
To further our understanding of the Great Attractor (GA), we have undertaken a redshift survey using the 2-degree Field (2dF) instrument on the Anglo-Australian Telescope (AAT). Clusters and filaments in the GA region were targeted with 25 separate pointings resulting in approximately 2600 new redshifts. Targets included poorly studied X-ray clusters from the Clusters in the Zone of Avoidance (CIZA) Catalogue as well as the Cen–Crux and PKS 1343−601 clusters, both of which lie close to the classic GA centre. For nine clusters in the region, we report velocity distributions as well as virial and projected mass estimates. The virial mass of CIZA J1324.7−5736, now identified as a separate structure from the Cen–Crux cluster, is found to be  ∼3 × 1014 M⊙  , in good agreement with the X-ray inferred mass. In the PKS 1343−601 field, five redshifts are measured of which four are new. An analysis of redshifts from this survey, in combination with those from the literature, reveals the dominant structure in the GA region to be a large filament, which appears to extend from Abell S0639  ( l = 281°, b =+11°)  to  ( l ∼ 5°, b ∼−50°)  , encompassing the Cen–Crux, CIZA J1324.7−5736, Norma and Pavo II clusters. Behind the Norma cluster at   cz ∼ 15 000 km s−1  , the masses of four rich clusters are calculated. These clusters (Triangulum Australis, Ara, CIZA J1514.6−4558 and CIZA J1410.4−4246) may contribute to a continued large-scale flow beyond the GA. The results of these observations will be incorporated into a subsequent analysis of the GA flow.  相似文献   

19.
We report on the iron Kα line properties of a sample of Seyfert galaxies observed with the XMM‐Newton EPIC pn instrument. Using a systematic and uniform analysis, we find that complexity at iron‐K is extremely common in the XMM‐Newton spectra. Once appropriate soft X‐ray absorption, narrow 6.4 keV emission and associated Compton reflection are accounted for, ∼75% of the sample show an improvement when a further component is introduced. The typical properties of the broad emission are both qualitatively and quantitatively consistent with previous results from ASCA. The complexity is in general very well described by relativistic accretion disk models. In most cases the characteristic emission radius is constrained to be within ∼50R g, where strong gravitational effects become important. We find in about 1/3 of the sample the accretion disk interpretation is strongly favoured over competing models. In a few objects no broad line is apparent. We find evidence for emission within 6R g in only two cases, both of which exhibit highly complex absorption. Evidence for black hole spin based on the X‐ray spectra therefore remains tentative. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

20.
We present the results of the simultaneous XMM‐Newton and Chandra observations of the bright Seyfert 1.9 galaxy MCG–5‐23‐16, which is one of the best known examples of a relativistically broadened iron Kα line. We find that: a) the soft X‐ray emission is likely to be dominated by photoionized gas, b) the complex iron emission line is best modelled with a narrow and a broad component with a FWHM ∼44000 km/s. This latter component has an EW ∼50 eV and its profile is well described with an emission line mainly originating from the accretion disk a few tens of gravitational radii from the central black hole and viewed with an inclination angle ∼40°. We found evidence of a possible sporadic absorption line at ∼7.7 keV which, if associated with Fe XXVI Kα resonance absorption, is indicative of a possible high velocity (v ∼ 0.1c) outflow. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

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