The Decameter sky at sub-arcminute resolution

Research Square

Abstract

Abstract The largely unexplored decameter radio band (10-30 MHz) provides a unique window for studying a range of astronomical topics, such as auroral emission from exoplanets, low-energy cosmic ray electrons, and the physics of free-free absorption. The scarcity of low-frequency studies is mainly due to the severe perturbing effects of the ionosphere. Correcting for the ionosphere is challenging as it changes rapidly in time and across the sky at low frequencies. Building upon previous successes at higher frequencies, we present a calibration strategy that can correct for the ionosphere in the decameter band. To evade the majority of radio frequency interference, we apply this to a night-time observation from the Low Frequency Array (LOFAR) between 16–30 MHz. This allows us to map a 305 square degrees region of sky at a resolution of 45", achieving a sensitivity of 12 mJy beam-1. This represents over an order of magnitude improvement in terms of sensitivity and resolution compared to previous decameter band observations, emphasising the large discovery potential of our data. Our work shows that sensitive sub-arcminute resolution decameter band surveys are possible with ground-based arrays.

Authors 13

1. Christian Groeneveld Aachen

   Leiden University

   Affiliation as printed

   Leiden University

2. Reinout J. van Weeren Aachen

   Leiden University

   Affiliation as printed

   Leiden University

3. E. Osinga

   Leiden Observatory

   Affiliation as printed

   Leiden Observatory

4. Wendy L. Williams

   SKA Observatory

   Affiliation as printed

   SKA Observatory

5. J. R. Callingham Aachen

   Leiden University

   Affiliation as printed

   Leiden University

6. F. de Gasperin

   Istituto di Radioastronomia di Bologna · National Institute for Astrophysics

   Affiliation as printed

   IRA-INAF

7. A. Botteon

   Istituto di Radioastronomia di Bologna · National Institute for Astrophysics

   Affiliation as printed

   INAF-IRA

8. T. W. Shimwell

   Leiden Observatory

   Affiliation as printed

   Leiden Observatory

9. Frits Sweijen Aachen

   Leiden University

   Affiliation as printed

   Leiden University

10. GEORGE K. MILEY

    Leiden Observatory

    Affiliation as printed

    Leiden Observatory

11. G. Brunetti

    Istituto di Radioastronomia di Bologna · National Institute for Astrophysics

    Affiliation as printed

    IRA - INAF

12. M. Brüggen

    Universität Hamburg

    Affiliation as printed

    University of Hamburg

13. Huub J. A. Röttgering

    Leiden Observatory

    Affiliation as printed

    Leiden Observatory