Discovery of an X-ray QSO

Ricker, G.; Clarke, G. W.; Doxsey, R.; Dower, R. G.; Jernigan, J. G.; Delvaille, J. P.; MacAlpine, G. M.; Hjellming, R. M.

doi:10.1038/271035a0

Cited by 43 publications

(22 citation statements)

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“…MR 2251−178 ( z = 0.064; Canizares, McClintock & Ricker 1978; Bergeron et al 1983) was first detected as a bright X‐ray source during the Ariel V all‐sky survey (Cooke et al 1978) and subsequently identified as a radio‐quiet quasar by Ricker et al (1978) using SAS‐3 observations. The quasar is located on the outskirts of a cluster of approximately 50 galaxies (Phillips 1980) and is surrounded by a large extended nebula of diffuse gas which is characterized by [O iii ] emission in the optical (Bergeron et al 1983).…”

Section: Introductionmentioning

confidence: 99%

A broad-band X-ray view of the warm absorber in radio-quiet quasar MR 2251−178

Gofford¹,

Reeves²,

Turner³

et al. 2011

Monthly Notices of the Royal Astronomical Society

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We present the analysis of a new broad-band X-ray spectrum (0.6-180.0 keV) of the radioquiet quasar MR 2251−178 which uses both Suzaku and Swift/Burst Alert Telescope data. In accordance with previous observations, we find that the general continuum can be well described by a power law with = 1.6 and an apparent soft excess below 1 keV. Warm absorption is clearly present, and absorption lines due to the Fe unresolved transition array, Fe L (Fe XXIII-XXIV), S XV and S XVI are detected below 3 keV. At higher energies, Fe K absorption from Fe XXV-XXVI is detected and a relatively weak (EW = 25 +12 −8 eV) narrow Fe Kα emission line is observed (E = 6.44 ± 0.04 keV) which is well modelled by the presence of a mildly ionized (ξ 30) reflection component with a low reflection fraction (R < 0.2). At least five ionized absorption components with 10 20 N H 10 23 cm −2 and 0 log ξ /erg cm s −1 4 are required to achieve an adequate spectral fit. Alternatively, we show that the continuum can also be fit if a ∼ 2.0 power law is absorbed by a column of N H ∼ 10 23 cm −2 which covers ∼30 per cent of the source flux. Independent of which continuum model is adopted, the Fe L and Fe XXV Heα lines are well fit by a single absorber outflowing with v out ∼ 0.14c. Such an outflow/disc-wind is likely to be substantially clumped (b ∼ 10 −3 ) in order to not vastly exceed the likely accretion rate of the source.

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Section: Introductionmentioning

confidence: 99%

A broad-band X-ray view of the warm absorber in radio-quiet quasar MR 2251−178

Gofford¹,

Reeves²,

Turner³

et al. 2011

Monthly Notices of the Royal Astronomical Society

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“…Based on positional coincidences, Cooke et al (1978) suggested the identification of seven X-ray sources in the 2A catalog as groups of galaxies. Subsequent observations showed that several of these X-ray sources were variable, indicating they were actually active galaxies within the group (Ricker et al 1978, Ward et al 1978, Griffiths et al 1979. However, several of the remaining objects in Cooke et al (1978) were later shown to be poor clusters (Schwartz et al 1980).…”

Section: Introductionmentioning

confidence: 99%

X-Ray Properties of Groups of Galaxies

Mulchaey

2000

Annu. Rev. Astron. Astrophys.

250

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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“…Given the high ratio of L x /L opt of MR 2251-178 (Ricker et al 1978), is it possible that a cooling flow contributes 3 If we increase the amount of absorbing material by NH = 5 10 19 cm −2 and re-fit the X-ray spectrum, the fit is drastically worse, with a change ∆χ 2 = 187. We therefore consider NH = 5 10 19 cm −2 as an upper limit to the excess absorption along the line of sight.…”

Section: High L X /L Opt and Presence Of A Cooling Flow?mentioning

confidence: 99%

“…MR 2251-178 was detected as a bright X-ray source in the course of the Ariel V all-sky survey (Cooke et al 1978) and identified with the quasar by Ricker et al (1978) from observations with the SAS-3 X-ray observa-tory. The X-ray spectrum of MR 2251-178 was first studied by Halpern (1984) who deduced the presence of a warm absorber based on the observed variability pattern of the Einstein data.…”

Section: Introductionmentioning

confidence: 99%

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The X-ray view of the quasar MR 2251-178 and its host cluster: Variability, absorption, and intracluster gas emission

Komossa

2001

A&A

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Abstract. MR 2251-178 was the first quasar initially discovered in X-rays, and the first one found to host a warm absorber. The quasar turned out to be an outstanding object in many respects. It has a high ratio of X-ray/optical luminosity, is surrounded by the largest quasar emission-line nebula known, and is located in the outskirts of a cluster of galaxies. Here, we present results from an analysis of the X-ray spectral, temporal, and spatial properties of this source and its environment based on deep ROSAT observations. Remarkably, we do not detect any excess X-ray cold absorption expected to originate from the giant gas nebula surrounding MR 2251-178. This excludes the presence of a huge HI envelope around the quasar. The X-ray spectrum of MR 2251-178 is best fit by a warmabsorbed powerlaw with an ionization parameter log U = 0.5 and a column density log Nw = 22.6 which, however, cannot be the same material as the giant optical emission line nebula. The mean (0.1-2.4) keV X-ray luminosity amounts to 10 45 erg/s. A spatial analysis shows that the bulk of the X-ray emission from the quasar is consistent with a point source, as expected in view of the powerlaw-shaped X-ray spectrum and the rapid X-ray variability we detect. In addition, extended emission appears at weak emission levels, including a bridge between the quasar and the cD galaxy of the cluster. The X-ray emission from the intra-cluster medium is weak or absent. We derive an upper limit on the X-ray luminosity of Lx ≤ 1.6 10 42 erg/s, weaker than other clusters of comparable richness. None of the other member galaxies of the cluster to which MR 2251-178 belongs, are detected in X-rays. However, east of the quasar there is a significant excess of X-ray sources, several of them without optical counterparts on the UK Schmidt plates.

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Discovery of an X-ray QSO

Cited by 43 publications

References 10 publications

A broad-band X-ray view of the warm absorber in radio-quiet quasar MR 2251−178

A broad-band X-ray view of the warm absorber in radio-quiet quasar MR 2251−178

X-Ray Properties of Groups of Galaxies

The X-ray view of the quasar MR 2251-178 and its host cluster: Variability, absorption, and intracluster gas emission

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