Volume 603, July 2017
|Number of page(s)||26|
|Section||Cosmology (including clusters of galaxies)|
|Published online||19 July 2017|
Sardinia Radio Telescope observations of Abell 194
The intra-cluster magnetic field power spectrum
1 INAF–Osservatorio Astronomico di Cagliari via della Scienza 5, 09047 Selargius (CA), Italy
2 Dip. di Fisica, Università degli Studi di Cagliari, Strada Prov.le Monserrato-Sestu Km 0.700, 09042 Monserrato (CA), Italy
3 Dip. di Fisica, Università degli Studi di Trieste – Sezione di Astronomia, via Tiepolo 11, 34143 Trieste, Italy
4 INAF–Osservatorio Astronomico di Trieste, via Tiepolo 11, 34143 Trieste, Italy
5 INAF–IASF Milano, via Bassini 15, 20133 Milano, Italy
6 Dep. of Physics and Astronomy, University of California at Irvine, 4129 Frederick Reines Hall, Irvine, CA 92697-4575, USA
7 INAF–Istituto di Radioastronomia, Bologna via Gobetti 101, 40129 Bologna, Italy
8 Dip. di Fisica e Astronomia, Università degli Studi di Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy
9 Agenzia Spaziale Italiana (ASI), 00100 Roma, Italy
10 SKA SA, 3rd Floor, The Park, Park Road, 7405 Pinelands, The Cape Town, South Africa
11 Department of Physics and Electronics, Rhodes University, PO Box 94, 6140 Grahamstown, South Africa
12 Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany
13 Fundación G. Galilei – INAF TNG, Rambla J. A. Fernández Pérez 7, 38712 Breña Baja (La Palma), Spain
14 Instituto de Astrofísica de Canarias, C/Vía Láctea s/n, 38205 La Laguna (Tenerife), Spain
15 Dep. de Astrofísica, Univ. de La Laguna, Av. del Astrofísico Francisco Sánchez s/n, 38205 La Laguna (Tenerife), Spain
16 ASTRON, the Netherlands Institute for Radio Astronomy, Postbus 2, 7990 AA, Dwingeloo, The Netherlands
17 Kapteyn Astronomical Institute, Rijksuniversiteit Groningen, Landleven 12, 9747 AD Groningen, The Netherlands
18 Naval Research Laboratory, Washington, District of Columbia 20375, USA
19 School of Physics, University of the Witwatersrand, Private Bag 3, 2050 Johannesburg, South Africa
20 University of Leiden, Rapenburg 70, 2311 EZ Leiden, The Netherlands
21 Astronomy Department, University of Geneva, 16 Ch. d’Ecogia, 1290 Versoix, Switzerland
22 Max Planck Institut für Astrophysik, Karl-Schwarzschild-Str.1, 85740 Garching, Germany
23 Laboratoire Lagrange, UCA, OCA, CNRS, Bd de l’Observatoire, CS 34229, 06304 Nice Cedex 4, France
24 School of Chemical & Physical Sciences, Victoria University of Wellington, PO Box 600, 6140 Wellington, New Zealand
25 Argelander-Institut für Astronomie, Auf dem Hügel 71, 53121 Bonn, Germany
26 National Radio Astronomy Observatory, PO Box O, Socorro, NM 87801, USA
27 Department of Physics and Astronomy, University of New Mexico, Albuquerque, NM 87131, USA
Received: 23 December 2016
Accepted: 23 March 2017
Aims. We study the intra-cluster magnetic field in the poor galaxy cluster Abell 194 by complementing radio data, at different frequencies, with data in the optical and X-ray bands.
Methods. We analyzed new total intensity and polarization observations of Abell 194 obtained with the Sardinia Radio Telescope (SRT). We used the SRT data in combination with archival Very Large Array observations to derive both the spectral aging and rotation measure (RM) images of the radio galaxies 3C 40A and 3C 40B embedded in Abell 194. To obtain new additional insights into the cluster structure, we investigated the redshifts of 1893 galaxies, resulting in a sample of 143 fiducial cluster members. We analyzed the available ROSAT and Chandra observations to measure the electron density profile of the galaxy cluster.
Results. The optical analysis indicates that Abell 194 does not show a major and recent cluster merger, but rather agrees with a scenario of accretion of small groups, mainly along the NE−SW direction. Under the minimum energy assumption, the lifetimes of synchrotron electrons in 3C 40 B measured from the spectral break are found to be 157 ± 11 Myr. The break frequency image and the electron density profile inferred from the X-ray emission are used in combination with the RM data to constrain the intra-cluster magnetic field power spectrum. By assuming a Kolmogorov power-law power spectrum with a minimum scale of fluctuations of Λmin = 1 kpc, we find that the RM data in Abell 194 are well described by a magnetic field with a maximum scale of fluctuations of Λmax = (64 ± 24) kpc. We find a central magnetic field strength of ⟨ B0 ⟩ = (1.5 ± 0.2) μG, which is the lowest ever measured so far in galaxy clusters based on Faraday rotation analysis. Further out, the field decreases with the radius following the gas density to the power of η = 1.1 ± 0.2. Comparing Abell 194 with a small sample of galaxy clusters, there is a hint of a trend between central electron densities and magnetic field strengths.
Key words: galaxies: clusters: general / galaxies: clusters: individual: Abell 194 / magnetic fields / large-scale structure of Universe
© ESO, 2017
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.