Title: NuSTAR Observations of Abell 2163: Constraints on Non-thermal Emission

Abstract

Since the first non-thermal reports of inverse Compton (IC) emission from the intracluster medium (ICM) of galaxy clusters at hard X-ray energies, we have yet to unambiguously confirm IC emission in observations with newer facilities. RXTE detected IC emission in one of the hottest known clusters, Abell 2163 (A2163), a massive merging cluster with a giant radio halo—the presumed source of relativistic electrons IC scattering CMB photons to X-ray energies. The cluster's redshift (z ~ 0.2) allows its thermal and non-thermal radio emission to fit the field of view of the Nuclear Spectroscopic Telescope Array (NuSTAR), permitting a deep observation capable of confirming or ruling out the RXTE report. The IC flux provides constraints on the average magnetic field strength in a cluster. To determine the global diffuse IC emission in A2163, we fit its global NuSTAR spectrum with four models: single- (1T) and two-temperature (2T), 1T+power-law component (T+IC), and multi-temperature+power law (9T+IC). Each represents different characterizations of the thermal ICM emission, with power-law components added to represent IC emission. We find that the 3–30 keV spectrum can be described by purely thermal emission, with a global average temperature of kT = (11.8 ± 0.2) keV. The IC flux ismore » constrained to <4.0 × 10^–12 erg s^–1 cm^–2 using the 1T+IC model and <1.6 × 10^–12 erg s^–1 cm^–2 with the more physical 9T+IC model, both to 90% confidence levels. Here, combining these limits with 1.4 GHz diffuse radio data from the VLA, we find the average magnetic field strength to be >0.22 μG and >0.35 μG, respectively, providing the strongest constraints on these values in A2163 to date.« less

Authors:

Rojas Bolivar, Randall A.  ^[1];

• Search DOE PAGES for author "Rojas Bolivar, Randall A."
• Search DOE PAGES for ORCID "0000-0002-8882-6426"

Wik, Daniel R.  ^[1];

• Search DOE PAGES for author "Wik, Daniel R."
• Search DOE PAGES for ORCID "0000-0001-9110-2245"

Giacintucci, Simona  ^[2];

• Search DOE PAGES for author "Giacintucci, Simona"
• Search DOE PAGES for ORCID "0000-0002-1634-9886"

Gastaldello, Fabio  ^[3];

• Search DOE PAGES for author "Gastaldello, Fabio"
• Search DOE PAGES for ORCID "0000-0002-9112-0184"

Hornstrup, Allan  ^[4];

• Search DOE PAGES for author "Hornstrup, Allan"
• Search DOE PAGES for ORCID "0000-0002-3363-0936"

Westergaard, Niels-Jorgen  ^[4];

• Search DOE PAGES for author "Westergaard, Niels-Jorgen"
• Search DOE PAGES for ORCID "0000-0001-5839-8590"

Madejski, Grzegorz  ^[5]

• Search DOE PAGES for author "Madejski, Grzegorz"
• Search DOE PAGES for ORCID "0000-0002-2114-5626"

---

+ Show Author Affiliations

1. Univ. of Utah, Salt Lake City, UT (United States)
2. Naval Research Lab., Washington, DC (United States)
3. Istituto di Astrofisica e Fiseca Cosmica-Milano Via Edoardo Bassini (Italy)
4. Technical Univ. of Denmark, Lyngby (Denmark)
5. SLAC National Accelerator Lab., Menlo Park, CA (United States)

Publication Date:

Tue Jan 12 00:00:00 EST 2021

Research Org.:

SLAC National Accelerator Lab., Menlo Park, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1767940

Grant/Contract Number:  

AC02-76SF00515; 80NAAX19K0915

Resource Type:

Accepted Manuscript

Journal Name:

The Astrophysical Journal (Online)

Additional Journal Information:

Journal Name: The Astrophysical Journal (Online); Journal Volume: 906; Journal Issue: 2; Journal ID: ISSN 1538-4357

Publisher:

Institute of Physics (IOP)

Country of Publication:

United States

Language:

English

Subject:

79 ASTRONOMY AND ASTROPHYSICS