Implications of Coronal Line Emission in NGC 4696*

Authors

Marios Chatzikos, University of KentuckyFollow
R.J.R. Williams, AWE plc, UK
Gary J. Ferland, University of KentuckyFollow
R. E. A. Canning, Stanford University
A. C. Fabian, University of Cambridge, UK
J. S. Sanders, Max-Planck-Institut für extraterrestrische Physik (MPE), Germany
P. A. M. van Hoof, Royal Observatory of Belgium, Belgium
R. M. Johnstone, University of Cambridge, UK
Matt L. Lykins, University of KentuckyFollow
R. L. Porter, University of Georgia

Abstract

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] λ5303/[Fe x] λ6375 luminosity ratio, a critical diagnostic of a cooling plasma, to slightly less than unity. By contrast, our calculations predict a ratio of ∼3. We revisit recent optical coronal line observations along the X-ray cool arc around NGC 4696 by Canning et al., which detected [Fe x] λ6375, but not [Fe xiv] λ5303. 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.

Document Type

Article

Publication Date

1-11-2015

Notes/Citation Information

Published in Monthly Notices of the Royal Astronomical Society, v. 446, no. 2, p. 1234-1244.

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2014 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

Digital Object Identifier (DOI)

http://dx.doi.org/10.1093/mnras/stu2173

Funding Information

GJF acknowledges support by NSF (0908877, 1108928, and 1109061), NASA (10-ATP10-0053, 10-ADAP10-0073, and NNX12AH73G), JPL (RSA No 1430426), and STScI (HST-AR-12125.01, GO-12560, and HST-GO-12309). ACF thanks European Research Council for the Advanced Grant FEEDBACK. PvH acknowledges support from the Belgian Science Policy Office through the ESA PRODEX programme.

Repository Citation

Chatzikos, Marios; Williams, R.J.R.; Ferland, Gary J.; Canning, R. E. A.; Fabian, A. C.; Sanders, J. S.; van Hoof, P. A. M.; Johnstone, R. M.; Lykins, Matt L.; and Porter, R. L., "Implications of Coronal Line Emission in NGC 4696*" (2015). Physics and Astronomy Faculty Publications. 267.
https://uknowledge.uky.edu/physastron_facpub/267