摘要:

A 20 ksec ROSAT PSPC observations of the cluster of galaxies Abell 1795 was used to perform a spatially resolved, spectral model fit, permitting a non‐parametric determination of the de‐projected radial temperature and density distribution (Figs. a, b). We derive the radial distribution of gravitating, gas, and galaxy mass (Fig. c), the dark‐to‐visible mass fraction, and determine the cooling time (Fig. e) and cooling flow. ©1994 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.46744

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

We present the results of ROSAT PSPC and HRI observations of two distant clusters, MS0735+74 and MS0451−03, selected from a sample of serendipitous X‐ray sources. MS0735+74 atz=0216 is a cooling flow candidate because it has extended H&agr; emission in the central brightest galaxy. MS) 451−03, atz=0.55, is the most luminous cluster in the Extended Medium Sensitivity Survey withLx≳1045ergs−1. We have been able to place significant limits onTx, core radii and the &bgr; parameter, and cooling flow contributions. Our preliminary results show that ‘‘cooling flows’’ can be identified by their extended H&agr; emission. Distant clusters probably do not have more intrinsic absorption than nearby clusters. More tentatively, luminous clusters at high redshift may be cooler and may have somewhat lowerMgas/Mtotal(at 1 Mpc scales) than the clusters of comparable luminosity at low redshift. ©1994 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.46692

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

We reprot on our analysis of deep X‐ray observations of Abell 665 and CL0016+16 obtained by the ROSAT position sensitive proportional counter (PSPC) as part of a project to characterize the density and temperature structure of clusters with well‐measured Sunyaev‐Zel’dovich decrements. The X‐ray images of both clusters show dramatic departures from the standard single‐component hydrostatic isothermal‐&bgr; model. ©1994 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.46693

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

Multi‐fiber spectra of galaxies in the Coma cluster in conjunction with ROSAT PSPC images demonstrate that the SW region of COMA is undergoing a major evolutionary event. This event, which appears to involve the infall and merging of a substructure, is likely related to the evolutionary phenomena observed in clusters at high redshift. ©1994 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.46694

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

We present detailed analyses of the X‐ray data for Abell 2142 and Abell 2199. Standard deprojection techniques were applied to the data to obtain 3D temperature and density profiles. The projected PSPC temperature profile in conjunction with the integrated Ginga spectrum of the clusters provides constraints on the total cluster mass. With additinal optical data, the minimum baryonic mass is inferred. ©1994 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.46695

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

A study of distant clusters of galaxies with radio sources was undertaken to study the evolution of the intracluster medium with redshift, and to determine if this evolution is related to the evolution of the radio source population. We obtained ROSAT HRI data for four clusters of galaxies that contain radio sources at redshifts of about 0.5. The results of these observations are presented here. Two of the clusters were detected, and two have interestingly low upper bounds on their X‐ray luminosities.The detected X‐ray emission is unresolved, and in each case could originate from either the hot intracluster medium or the radio source. The fact that the two clusters that contain FRII radio sources have upper bounds on their X‐ray luminosities, while the two clusters with compact or amorphous radio sources have detected X‐ray luminosities supports the notion that the evolution of the environments of FRII radio sources with redshift may be linked to the evolution of the intracluster medium with redshift, as discussed by Wanet al. (1994 a,b). ©1994 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.46696

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

HST FOC and ROSAT HRI X‐ray imaging is presented of the galaxy NGC4696. The X‐ray image shows similar morphology to ground‐based optical images of the emission‐line gas and dust in this object — a one‐armed spiral mostly to the South of the nucleus. A morphological correspondence between cool and hot gas phases is required in the ‘‘merger’’ interpretation of this and other similar systems. That interpretation has been proposed as a viable alter‐native to cooling‐flows, without the large mass depositions of the cooling‐flow scenario, and relying on quite different physical processes to explain the observations.A prediction of the merger model, in which cold accreted gas draws energy from pre‐existing hot coronal gas via electron conduction, was that the X‐ray and optical gaseous morphologies should be closely related. Here, we present a preliminary analysis of high resolution X‐ray imaging data, recently obtained with the ROSAT satellite, as well as high resolution HST FOC data of the core regions of this galaxy. ©1994 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.46697

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

A sample of high‐redshift X‐ray clusters was compiled by combining our ROSAT observations of four distant clusters with results avaiable in the published literature. This sample of 26 distant clusters is divided into two subsamples, those with and without FRII radio sources. It is found that the clusters with FRII radio sources tend to be less luminous X‐ray sources than the high‐redshift clusters that do not have FRII radio sources, though there are exceptions.In addition to comparing the two high‐redshift subsamples, each subsample is compared with a low‐redshift sample of clusters with known optical and X‐ray properties. The high‐redshift clusters with FRII sources also tend to be underluminous in the X‐ray relative to low‐redshift clusters with similar optical properties (richness), and significantly underluminous in the X‐ray if the expected X‐ray emission from the radio sources is taken into account, though the highest power FRII sources appear to be exceptions. The high‐redshift clusters without FRII radio sources show no tendency to be underluminous relative to optically similar low‐redshift clusters.This suggest that the evolution of the environments of FRII radio sources with redshift is closely linked with the evolution of the intracluster medium. It is interesting to note that the fraction of clusters in our distant sample that contain FRII radio sources and are underluminous X‐ray sources is similar to the fraction of clusters missing from the high‐redshift X‐ray luminosity function relative to that for low‐redshift clusters. If further investigations indicate that high‐redshift clusters with and without FRII radio sources are of similar richness, this would imply that the evolution of the cluster X‐ray luminosity function is more strongly linked with the evolution of the intracluster medium than with X‐ray luminosity established for low‐redshift clusters evolves with redshift. ©1994 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.46698

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

The ROSAT PSPC spectrum of NGC 6251 can be fitted with either a multiple‐component model obscured by the gas column within our Galaxy or by a single power‐law component obscured by this Galactic gas and an additional columnN=1.3×1021cm−2. We have used the VLA to search for the the HI line in absorption towards the radio core of NGC 6251 to set limits on the total X‐ray absorbing column. We find marginal evidence for a weak, broad, absorption feature associated with NGC 6251 which could provide the extra HI column suggested by the simpler X‐ray spectral fit. ©1994 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.46699

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

ROSATPSPC observations of the blazars PKS 1034–293 and PKS 1335–127 are presented. In both cases the spectra are well fitted by a single absorbed power law. For PKS 1034–293 we obtainF1keV=0.23±0.02 &mgr;Jy, &Ggr;=1.23+0.54−0.50,nH=1.31.7−1.2(1020cm−2) (90% uncertainty). The column density is significantly smaller than the galactic value derived from Starket al. 1992. For PKS 1335–127 we find FkeV=0.50±0.02 &mgr;Jy, &Ggr;=2.29+0.55−0.51,nH=6.60+3.00−2.23(1020cm−2): in this case the column density derived from the fit is in good agreement with the recent determination by Jacksonet al. 1993. ©1994 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.46741

出版商:AIP    

年代:1994

数据来源: AIP