Diffuse radio source candidate in CIZA J1358.9−4750

Publications of the Astronomical Society of Japan, vol. 75, pp. S138–S153

Abstract

Abstract We report on results of our upgraded Giant Metrewave Radio Telescope (uGMRT) observations for an early-stage merging galaxy cluster, CIZA J1358.9−4750 (CIZA1359), in Band-3 (300–500 MHz). We achieved the image dynamic range of ∼38000 using the direction dependent calibration and found a candidate of diffuse radio emission at 4σrms significance. The flux density of the candidate at 400 MHz, 24.04 ± 2.48 mJy, is significantly positive compared to noise, where its radio power, 2.40 × 1024 W Hz−1, is consistent with those of typical diffuse radio sources of galaxy clusters. The candidate is associated with a part of the X-ray shock front at which the Mach number reaches its maximum value of $\mathcal {M}\sim 1.7$. The spectral index (Fν ∝ να) of the candidate, α = −1.22 ± 0.33, is in agreement with an expected value derived from the standard diffusive shock acceleration (DSA) model. However, such a low Mach number with a short acceleration time would require seed cosmic rays supplied from active galactic nucleus (AGN) activities of member galaxies, as suggested in some other clusters. Indeed, we found seven AGN candidates inside the diffuse source candidate. Assuming the energy equipartition between magnetic fields and cosmic rays, the magnetic field strength of the candidate was estimated to be 2.1 μG. We also find head–tail galaxies and radio phoenixes or fossils near CIZA1359.

Authors 14

1. Kohei Kurahara corresponding

   National Astronomical Observatory of Japan

   Affiliation as printed

   Mizusawa VLBI Observatory, National Astronomical Observatory of Japan , 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan

2. Takuya Akahori

   SKA Observatory · National Astronomical Observatory of Japan

   Affiliation as printed

   Mizusawa VLBI Observatory, National Astronomical Observatory of Japan , 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan

   Operation Division, Square Kilometre Array Observatory , Lower Withington, Macclesfield, Cheshire SK11 9FT, UK

3. Ruta Kale

   Tata Institute of Fundamental Research · National Centre for Radio Astrophysics

   Affiliation as printed

   National Centre for Radio Astrophysics, Tata Institute of Fundamental Research, S. P. Pune University Campus , Ganeshkhind, Pune 411007, India

4. Hiroki Akamatsu Aachen SRON Netherlands Institute for Space Research

   Space Research Organisation Netherlands

   Affiliation as printed

   SRON Netherlands Institute for Space Research , Niels Bohrweg 4, 2333 CA Leiden, the Netherlands

5. Yutaka Fujita

   Tokyo Metropolitan University

   Affiliation as printed

   Department of Physics, Graduate School of Science, Tokyo Metropolitan University , 1-1 Minami-Osawa, Hachioji-shi, Tokyo 192-0397, Japan

6. Liyi Gu Aachen SRON Netherlands Institute for Space Research

   Space Research Organisation Netherlands

   Affiliation as printed

   SRON Netherlands Institute for Space Research , Niels Bohrweg 4, 2333 CA Leiden, the Netherlands

7. Huib T. Intema Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University , Niels Bohrweg 2, 2333 CA, Leiden, the Netherlands

8. Kazuhiro Nakazawa

   Nagoya University

   Affiliation as printed

   The Kobayashi-Maskawa Institute for the Origin of Particles and the Universe (KMI), Nagoya University , Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan

9. Nobuhiro Okabe

   Hiroshima University

   Affiliation as printed

   Department of Physical Science, Hiroshima University , 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan

   Hiroshima Astrophysical Science Center, Hiroshima University , 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan

10. Yuki Omiya

    Nagoya University

    Affiliation as printed

    Departure of Physics, Nagoya University , Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8601, Japan

11. Viral Parekh

    Rhodes University · South African Radio Astronomy Observatory

    Affiliation as printed

    Centre for Radio Astronomy Techniques and Technologies, Department of Physics and Electronics, Rhodes University , PO Box 94, Makhanda, 6140, South Africa

    South African Radio Astronomy Observatory (SARAO) , 2 Fir Street, Black River Park, Observatory, Cape Town 7925, South Africa

12. T. W. Shimwell Aachen Leiden Observatory

    Leiden University · Leiden Observatory · Netherlands Institute for Radio Astronomy

    Affiliation as printed

    ASTRON, the Netherlands Institute for Radio Astronomy , Oude Hoogeveensedijk 4, 7991 PD Dwingeloo, the Netherlands

    Leiden Observatory, Leiden University , PO Box 9513, NL-2300 RA Leiden, the Netherlands

13. Motokazu Takizawa

    Yamagata University

    Affiliation as printed

    Department of Physics, Yamagata University , 1-4-12 Kojirakawa-machi, Yamagata, Yamagata 990-8560, Japan

14. Reinout J. van Weeren Aachen Leiden Observatory

    Leiden University · Leiden Observatory

    Affiliation as printed

    Leiden Observatory, Leiden University , PO Box 9513, NL-2300 RA Leiden, the Netherlands