Ni Abundance in the Core of the Perseus Cluster: An Answer to the Significance of Resonant Scattering

Gastaldello, F.; Molendi, S.

doi:10.1086/379970

Cited by 30 publications

(31 citation statements)

References 31 publications

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“…Churazov et al (2004) use the Fe-K complex of lines at 6.7 keV to find a lower limit to the turbulence in the Perseus cluster. Independently, using the same data, Gastaldello & Molendi (2004) reached similar conclusions. The spectral resolution of the current instruments at these energies is however low, which limits the accuracy of the measurement.…”

Section: Introductionsupporting

confidence: 61%

Estimating turbulent velocities in the elliptical galaxies NGC 5044 and NGC 5813

Plaa

Zhuravleva

Werner

et al. 2012

A&A

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Context. The interstellar and intra-cluster medium (ICM) in giant elliptical galaxies and clusters of galaxies is often assumed to be in hydrostatic equilibrium. Numerical simulations, however, show that about 5-30% of the pressure in a cluster is provided by turbulence induced by, for example, the central active galactic nucleus (AGN) and merger activity. Aims. We aim to put constraints on the turbulent velocities and the turbulent pressure in the ICM of the giant elliptical galaxies NGC 5044 and NGC 5813 using XMM-Newton reflection grating spectrometer (RGS) observations. Methods. The magnitude of the turbulence is estimated using the Fe xvii lines at 15.01 Å, 17.05 Å, and 17.10 Å in the RGS spectra. At low turbulent velocities, the gas becomes optically thick in the 15.01 Å line due to resonant scattering, while the 17 Å lines remain optically thin. By comparing the (I 17.05 + I 17.10 )/I 15.01 line ratio from RGS with simulated line ratios for different Mach numbers, the level of turbulence is constrained. The measurement is, however, limited by the systematic uncertainty in the line ratio for an optically thin plasma, which is about 20-30%. Results. We find that the (I 17.05 + I 17.10 )/I 15.01 line ratio in NGC 5813 is significantly higher than in NGC 5044. This difference can be explained by a higher level of turbulence in NGC 5044. The best estimates for the turbulent velocities using resonant scattering and upper limits from the line widths, are 320 < V turb < 720 km s −1 for NGC 5044 and 140 < V turb < 540 km s −1 for NGC 5813 at the 90% confidence limit. Conclusions. The high turbulent velocities and the fraction of the turbulent pressure support of >40% in NGC 5044, assuming isotropic turbulence, confirm that it is a highly disturbed system, probably due to an off-axis merger. The turbulent pressure support in NGC 5813 is more modest at 15-45%. The (I 17.05 + I 17.10 )/I 15.01 line ratio in an optically thin plasma, calculated using AtomDB v2.0.1, is 2σ above the ratio measured in NGC 5044, which cannot be explained by resonant scattering. This shows that the discrepancies between theoretical, laboratory, and astrophysical data on Fe xvii lines need to be reduced to improve the accuracy of the determination of turbulent velocities using resonant scattering.

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Section: Introductionsupporting

confidence: 61%

Estimating turbulent velocities in the elliptical galaxies NGC 5044 and NGC 5813

Plaa

Zhuravleva

Werner

et al. 2012

A&A

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“…The gas in the cluster may be optically thick to resonantly scattered lines (e.g. Gilfanov, Syunyaev & Churazov 1987); however, Dupke & Arnaud (2001), Churazov et al (2004) and Gastaldello & Molendi (2004) observe no evidence for resonant scattering in this cluster. Another effect is known as ‘Fe‐bias’ (Buote 2000), where one underestimates the abundance of the emitting gas if it consists of more than one phase.…”

Section: Abundance Structurementioning

confidence: 99%

Mapping small-scale temperature and abundance structures in the core of the Perseus cluster

Sanders

Fabian

Allen

et al. 2004

Monthly Notices of the Royal Astronomical Society

150

185

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We report further results from a 191‐ks Chandra observation of the core of the Perseus cluster, Abell 426. The emission‐weighted temperature and abundance structures are mapped in detail. There are temperature variations down to ∼1 kpc in the brightest regions. Globally, the strongest X‐ray surface brightness features appear to be caused by temperature changes. Density and temperature changes conspire to give approximate azimuthal balance in pressure showing that the gas is in hydrostatic equilibrium. Si, S, Ar, Ca, Fe and Ni abundance profiles rise inwards from about 100 kpc, peaking at about 30–40 kpc. Most of these abundances drop inwards of the peak, but Ne shows a central peak, all of which may be explained by resonance scattering. There is no evidence for a widespread additional cooler temperature component in the cluster with a temperature greater than a factor of 2 from the local temperature. There is, however, evidence for a widespread hard component which may be non‐thermal. The temperature and abundance of gas in the cluster are observed to be correlated in a manner similar to that found between clusters.

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“…For the Perseus cluster, an initial analysis suggested that resonant scattering effects were present (Molendi et al 1998;Akimoto et al 1999), although subsequent studies (Churazov et al 2004;Gastaldello and Molendi 2004) did not support these results (see also Ezawa et al 2001;Dupke and Arnaud 2001;Sanders et al 2004). Several other clusters, including M87, Centaurus and A2199, were searched for resonant scattering effects (e.g, Kaastra et al 1999;Akimoto et al 1999Akimoto et al , 2000Sanders and Fabian 2006;Mathews et al 2001;Sakelliou et al 2002), with mixed results.…”

Section: Introductionmentioning

confidence: 99%

Resonant Scattering of X-ray Emission Lines in the Hot Intergalactic Medium

et al. 2010

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While very often a hot intergalactic medium (IGM) is optically thin to continuum radiation, the optical depth in resonant lines can be of order unity or larger. Resonant scattering in the brightest X-ray emission lines can cause distortions in the surface brightness distribution, spurious variations in the abundance of heavy elements, changes in line spectral shapes and even polarization of line emission. The magnitude of these effects not only depends on the density, temperature and ionization state of the gas, but is also sensitive to the characteristics of the gas velocity field. This opens a possibility to use resonant scattering as a convenient and powerful tool to study IGM properties. We discuss the application of these effects to galaxy clusters.

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Ni Abundance in the Core of the Perseus Cluster: An Answer to the Significance of Resonant Scattering

Cited by 30 publications

References 31 publications

Estimating turbulent velocities in the elliptical galaxies NGC 5044 and NGC 5813

Estimating turbulent velocities in the elliptical galaxies NGC 5044 and NGC 5813

Mapping small-scale temperature and abundance structures in the core of the Perseus cluster

Resonant Scattering of X-ray Emission Lines in the Hot Intergalactic Medium

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