Mass and Metallicity of Five X‐Ray–bright Galaxy Groups

Hwang, U.; Mushotzky, R. F.; Burns, Jack O.; Fukazawa, Yasushi; White, R. A.

doi:10.1086/307147

Cited by 40 publications

(47 citation statements)

References 59 publications

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“…However, this also did not modify the low-energy spectrum. Other authors have also noted the loss in lowenergy response from the SIS appearing as an increase in the inferred column density (Hwang et al 1999 ;Mukai & Smale 2000). We found that an additional SIS-1 absorption of 4.0 ] 1021 cm~2 for GX 354[0 and 2.4 ] 1021 cm~2 for KS 1731[260 was required in our observation.…”

Section: Observation and Resultssupporting

confidence: 75%

ASCAObservations of GX 354−0 and KS 1731−260

Narita

Grindlay

Barret

2001

ApJ

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We report on ASCA observations of the low-mass X-ray binaries GX 354[0 and KS 1731[260. The spectrum of GX 354[0 is best described as a power law or a Comptonized spectrum with q D 5 and kT D 8 keV and a residual at D6.5 keV. The residual may be a disk reÑection or a Compton-broadened Gaussian line from the hot inner advection-dominated accretion ÑowÈlike coronal region. The absorption column density to the source is 2.9 ] 1022 cm~2. No soft thermal component was detected. The spectrum from KS 1731[260 is softer, and it is best Ðt with a two-component model with a column density of 1.1 ] 1022 cm~2. The likely interpretation is emission from a Comptonizing cloud with an optical depth q [ 12 and either a neutron star or a disk blackbody emission. We discuss the likely location of the Comptonizing cloud for both sources within the context of several proposed emission models.

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Section: Observation and Resultssupporting

confidence: 75%

ASCAObservations of GX 354−0 and KS 1731−260

Narita

Grindlay

Barret

2001

ApJ

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“…The luminosity function derived by Burns et al (1996) is a smooth extrapolation of the rich cluster X-ray luminosity function and is consistent with the luminosity function Henry et al (1995) derived from their X-ray selected sample of groups. Follow-up work on some of the brighter sources in the WBL catalog indicates that many of these objects are more massive than typical groups with gas temperatures of 2-3 keV (Hwang et al 1999). These systems are important because they represent the transition objects between poor groups and rich clusters.…”

Section: Rosat Surveys Of Groupsmentioning

confidence: 99%

X-Ray Properties of Groups of Galaxies

Mulchaey

2000

Annu. Rev. Astron. Astrophys.

252

288

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ROSAT observations indicate that approximately half of all nearby groups of galaxies contain spatially extended X-ray emission. The radial extent of the X-ray emission is typically 50-500 h −1 100 kpc or approximately 10-50% of the virial radius of the group. Diffuse X-ray emission is generally restricted to groups that contain at least one early-type galaxy. X-ray spectroscopy suggests the emission mechanism is most likely a combination of thermal bremsstrahlung and line emission. This interpretation requires that the entire volume of groups be filled with a hot, low-density gas known as the intragroup medium. ROSAT and ASCA observations indicate that the temperature of the diffuse gas in groups ranges from approximately 0.3 keV to 2 keV. Higher temperature groups tend to follow the correlations found for rich clusters between X-ray luminosity, temperature, and velocity dispersion. However, groups with temperatures below approximately 1 keV appear to fall off the cluster LX-T relationship (and possibly the LX-σ and σ-T cluster relationships, although evidence for these latter departures is at the present time not very strong.) Deviations from the cluster LX-T relationship are consistent with preheating of the intragroup medium by an early generation of stars and supernovae. There is now considerable evidence that most X-ray groups are real, physical systems and not chance superpositions or large-scale filaments viewed edge-on. Assuming the intragroup gas is in hydrostatic equilibrium, X-ray observations can be used to estimate the masses of individual systems. ROSAT observations indicate that the typical mass of an X-ray group is ∼ 10 13 h100−1

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“…Since the determinations of and r c depend somewhat on the extension of the X-ray surface brightness profile if the available data extend only out to 2 or 3 times the core radius, we truncate each S X ðrÞ at the maximum radii set by the X-ray surface brightness limits S limit ¼ 2 Â 10 À14 and 2 Â 10 À15 ergs s À1 arcmin À2 cm À2 in the 0.5-2.0 keV band, respectively. These two values have approximately covered White et al (1997) and 21 data points of groups ( filled stars) by Mulchaey et al (1996) and Hwang et al (1999) within different radii, which are properly binned according to temperature and radius. Fig.…”

Section: Radial Distribution Of Gas Fractionmentioning

confidence: 99%

“…Next, we choose the two group samples of Mulchaey et at. (1996) and Hwang et al (1999) used in the construction of the f star -T relation (see eq.…”

Section: Radial Distribution Of Gas Fractionmentioning

confidence: 99%

Reexamination of the Galaxy Formation–regulated Gas Evolution Model in Groups and Clusters

Xue

2002

ApJ

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As an alternative explanation of the entropy excess and the steepening of the X-ray luminosity-temperature relation in groups and clusters, the galaxy formation-regulated gas evolution (GG) model proposed recently by Bryan makes an attempt to incorporate the formation of galaxies into the evolution of gas without additional heating by nongravitational processes. This seems to provide a unified scheme for our understanding of the structures and evolution of both galaxies and gas in groups and clusters. In this paper, we present an extensive comparison of the X-ray properties of groups and clusters predicted by the GG model and those revealed by current X-ray observations, using various large data sources in the literature and also taking the observational selection effects into account. These include an independent check of the fundamental working hypothesis of the GG model (i.e., galaxy formation was less efficient in rich clusters than in groups), a new test of the radial gas distributions revealed by both the gas mass fraction and the X-ray surface brightness profiles, and a reexamination of the X-ray luminosity-temperature and entropy-temperature relations. In particular, it shows that the overall X-ray surface brightness profiles predicted by the GG model are very similar in shape and insensitive to the X-ray temperature and that the shallower X-ray surface brightness profiles seen at low-temperature systems may arise from the current observational selection effect. This can be used as the simplest approach to distinguishing between the GG model and the preheating scenario. The latter yields an intrinsically shallower gas distribution in groups than in rich clusters.

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Mass and Metallicity of Five X‐Ray–bright Galaxy Groups

Cited by 40 publications

References 59 publications

ASCAObservations of GX 354−0 and KS 1731−260

ASCAObservations of GX 354−0 and KS 1731−260

X-Ray Properties of Groups of Galaxies

Reexamination of the Galaxy Formation–regulated Gas Evolution Model in Groups and Clusters

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