skip to main content

Title: Polarization diagnostics for cool core cluster emission lines

The nature of the interaction between low-excitation gas filaments at ∼10{sup 4} K, seen in optical line emission, and diffuse X-ray emitting coronal gas at ∼10{sup 7} K in the centers of galaxy clusters remains a puzzle. The presence of a strong, empirical correlation between the two gas phases is indicative of a fundamental relationship between them, though as yet of undetermined cause. The cooler filaments, originally thought to have condensed from the hot gas, could also arise from a merger or the disturbance of cool circumnuclear gas by nuclear activity. Here, we have searched for intrinsic line emission polarization in cool core galaxy clusters as a diagnostic of fundamental transport processes. Drawing on developments in solar astrophysics, direct energetic particle impact induced polarization holds the promise to definitively determine the role of collisional processes such as thermal conduction in the ISM physics of galaxy clusters, while providing insight into other highly anisotropic excitation mechanisms such as shocks, intense radiation fields, and suprathermal particles. Under certain physical conditions, theoretical calculations predict of the order of 10% polarization. Our observations of the filaments in four nearby cool core clusters place stringent upper limits (≲ 0.1%) on the presence of emission linemore » polarization, requiring that if thermal conduction is operative, the thermal gradients are not in the saturated regime. This limit is consistent with theoretical models of the thermal structure of filament interfaces.« less
Authors:
; ; ;  [1] ;  [2] ; ;  [3] ;  [4] ;  [5]
  1. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
  2. Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom)
  3. Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824-2320 (United States)
  4. University of Hertfordshire, College Lane, Hatfield AL10 9AB (United Kingdom)
  5. CFHT, 65-1238 Mamalahoa Hwy, Kamuela, HI 96743 (United States)
Publication Date:
OSTI Identifier:
22348320
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 780; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ANISOTROPY; ASTROPHYSICS; DISTURBANCES; DRAWING; EMISSION; EXCITATION; FILAMENTS; GALAXIES; GALAXY CLUSTERS; HEAT EXCHANGERS; INTERACTIONS; INTERFACES; POLARIZATION; TEMPERATURE GRADIENTS; THERMAL CONDUCTION; X RADIATION