Optical coronal emission lines from cooling flows in elliptical galaxies and galaxy clusters

Sarazin, Craig L.; Graney, Christopher M.

doi:10.1086/170215

Cited by 10 publications

(20 citation statements)

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“…(For isochoric cooling, Γ ≈ 2.07 × 10 11 erg g −1 , and the mass rate is ∼2.68 M ⊙ yr −1 .) This is significantly lower than the rate of 20 M ⊙ yr −1 , deduced by C11a using the older results of Sarazin & Graney (1991), and in overall agreement with the X-ray spectroscopy results. Note, however, that this estimate is in excess of the upper limit of 0.8 M ⊙ yr −1 obtained by Sanders et al (2008) by fitting the entire spectrum with a multi-component cooling flow model.…”

Section: Comparison To X-ray Gassupporting

confidence: 89%

“…whereṀ is the mass deposition rate (e.g., Sarazin & Graney 1991). The remaining symbols have their usual meaning.…”

Section: Spectral Simulationsmentioning

confidence: 99%

“…The atomic line database used to compute the cooling is far larger than was available previously, due to our use of both Opacity Project and Chianti line data. Even for lines in common with Sarazin & Graney (1991), the cooling can be quite different due to our use of high-quality close coupling collision rates, rather than the simpler rates that were available at that time. Table 1 lists the optical coronal lines of interest.…”

Section: Comparison With Previous Calculationsmentioning

confidence: 99%

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Implications of coronal line emission in NGC 4696*

Chatzikos

Williams

Ferland

et al. 2014

Monthly Notices of the Royal Astronomical Society

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We announce a new facility in the spectral code CLOUDY that enables tracking the evolution of a cooling parcel of gas with time. For gas cooling from temperatures relevant to galaxy clusters, earlier calculations estimated the [Fe XIV] λ 5303 / [Fe X] λ 6375 luminosity ratio, a critical diagnostic of a cooling plasma, to slightly less than unity. By contrast, our calculations predict a ratio ∼3. We revisit recent optical coronal line observations along the X-ray cool arc around NGC 4696 by , which detected [Fe X] λ 6375, but not [Fe XIV] λ 5303. We show that these observations are not consistent with predictions of cooling flow models. Differential extinction could in principle account for the observations, but it requires extinction levels (A V > 3.625) incompatible with previous observations. The non-detection of [Fe XIV] implies a temperature ceiling of 2.1 million K. Assuming cylindrical geometry and transonic turbulent pressure support, we estimate the gas mass at ∼1 million M ⊙ . The coronal gas is cooling isochorically. We propose that the coronal gas has not condensed out of the intracluster medium, but instead is the conductive or mixing interface between the X-ray plume and the optical filaments. We present a number of emission lines that may be pursued to test this hypothesis and constrain the amount of intermediate temperature gas in the system.

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Section: Comparison To X-ray Gassupporting

confidence: 89%

“…whereṀ is the mass deposition rate (e.g., Sarazin & Graney 1991). The remaining symbols have their usual meaning.…”

Section: Spectral Simulationsmentioning

confidence: 99%

Section: Comparison With Previous Calculationsmentioning

confidence: 99%

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Implications of coronal line emission in NGC 4696*

Chatzikos

Williams

Ferland

et al. 2014

Monthly Notices of the Royal Astronomical Society

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“…The Hα strength would thus be 0.03 (5/2) (kT /µm p )Ṁ , where m p is the proton mass, µ is the mean mass per particle in units of m p , T is the temperature of the hot gas, and k is the Boltzmann constant. In this picture, both the Hα and coronal-line luminosities scale withṀ , leading to well-defined predictions for their ratios, which we list in Table 3 (Voit, Donahue, & Slavin 1994;Sarazin & Graney 1991).…”

Section: Coronal Emission and Coolingmentioning

confidence: 86%

Emission‐Line Properties of the Optical Filaments of NGC 1275

Sabra

Shields

Filippenko

2000

ApJ

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Extended nebular filaments are seen at optical wavelengths in NGC 1275, the central galaxy in the Perseus cluster. The agents responsible for the excitation of these filaments remain poorly understood. In this paper we investigate possible mechanisms for powering the filaments, using measurements from an extensive spectroscopic data set acquired at the Lick Observatory 3-m Shane telescope. The results show that the filaments are in an extremely low ionization and excitation state. The high signal-to-noise ratio of the spectra allows us to measure or place sensitive upper limits on weak but important diagnostic lines. We compare the observed line intensity ratios to the predictions of various ionization models, including photoionization by an active galactic nucleus, shock heating, stellar photoionization, and photoionization by the intracluster medium. We also investigate possible roles for cluster extreme-ultraviolet emission, and filtering of cluster soft X-ray emission by an ionized screen, in the energetics of the filaments. None of these mechanisms provides an entirely satisfactory explanation for the physical state of the nebulae. Heating and ionization by reconnection of the intracluster magnetic field remains a potentially viable alternative, which merits further investigation through Faraday rotation studies.

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“…For this reason and to allow maximum model independence, we fitted, as free parameters, the normalization of the central region relative to other regions, the fraction of a cooling flow (or another spectral component) in the total emission from that model region, and the temperature of its main thermal component, from which the cooling was assumed to start. A cooling flow spectrum was modeled as prescribed in Sarazin & Graney (1991). Because of the large number of free parameters for the central spectra and the PSF uncertainty associated with the small regions (r = 1.5 ′ or 2 ′ ) used to model cooling flows, the derived central temperatures for strong cooling flow clusters are weakly constrained.…”

Section: Treatment Of Cooling Flowsmentioning

confidence: 99%

The Temperature Structure of 30 Nearby Clusters Observed withASCA: Similarity of Temperature Profiles

Markevitch

Forman

Sarazin

et al. 1998

ApJ

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445

115

529

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We present an analysis of ASCA spatially resolved spectroscopic data for a nearly complete sample of bright clusters with redshifts between 0.04 and 0.09. Together with several clusters analyzed elsewhere using the same method, this sample consists of 30 objects with T e ∼ > 3.5 keV for which we obtained projected temperature profiles and, when possible, crude two-dimensional temperature maps. All clusters, with the possible exception of a few with insufficiently accurate data, are found to be nonisothermal with spatial temperature variations (apart from cooling flows) by a factor of 1.3-2. ASCA temperature maps for many clusters reveal merger shocks. The most notable of these are A754, A2065, A3558, A3667, and Cygnus A; merging can also be inferred with lower confidence from the A85, A119, and A2657 temperature maps and from the A3395 and Triangulum Australis entropy maps. About half of the sample shows signs of merging; in about 60% of the sample, we detect cooling flows. Nearly all clusters show a significant radial temperature decline at large radii. For a typical 7 keV cluster, the observed temperature decline between 1 and 6 X-ray core radii (0.15 and 0.9 h −1 Mpc) can be approximately quantified by a polytropic index of 1.2-1.3. Assuming such a polytropic temperature profile and hydrostatic equilibrium, the gravitating mass within 1 and within 6 core radii is approximately 1.35 and 0.7 times the isothermal β-model estimates, respectively.Most interestingly, we find that temperature profiles, excluding those for the most asymmetric clusters, appear remarkably similar when the temperature is plotted against radius in units of the estimated virial radius. We compare the composite temperature profile to a host of published hydrodynamic simulations. The observed profiles appear steeper than predictions of most Lagrangian simulations (Evrard, Metzler, & Navarro 1996;Eke, Navarro, & Frenk 1997). The predictions for Ω = 1 cosmological models are most discrepant, while models with low Ω are closer to our data. We note, however, that at least one Ω = 1 Lagrangian simulation (Katz & White 1993) and the recent high-resolution Eulerian simulation (Bryan & Norman 1997) produced clusters with temperature profiles similar to or steeper than those observed. Our results thus provide a new constraint for adjusting numerical simulations and, potentially, discriminating among models of cluster formation.

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Optical coronal emission lines from cooling flows in elliptical galaxies and galaxy clusters

Cited by 10 publications

References 0 publications

Implications of coronal line emission in NGC 4696*

Implications of coronal line emission in NGC 4696*

Emission‐Line Properties of the Optical Filaments of NGC 1275

The Temperature Structure of 30 Nearby Clusters Observed withASCA: Similarity of Temperature Profiles

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