LOFAR Deep Fields: Probing faint Galactic polarised emission in ELAIS-N1
Artikel i vetenskaplig tidskrift, 2023

We present the first deep polarimetric study of Galactic synchrotron emission at low radio frequencies. Our study is based on 21 observations of the European Large Area Infrared Space Observatory Survey-North 1 (ELAIS-N1) field using the Low-Frequency Array (LOFAR) at frequencies from 114.9 to 177.4 MHz. These data are a part of the LOFAR Two-metre Sky Survey Deep Fields Data Release 1. We used very low-resolution (4.3') Stokes QU data cubes of this release. We applied rotation measure (RM) synthesis to decompose the distribution of polarised structures in Faraday depth, and cross-correlation RM synthesis to align different observations in Faraday depth. We stacked images of about 150 h of the ELAIS-N1 observations to produce the deepest Faraday cube at low radio frequencies to date, tailored to studies of Galactic synchrotron emission and the intervening magneto-ionic interstellar medium. This Faraday cube covers ∼36 deg2 of the sky and has a noise of 27 μJy PSF-1 RMSF-1 in polarised intensity. This is an improvement in noise by a factor of approximately the square root of the number of stacked data cubes (√20), as expected, compared to the one in a single data cube based on five-to-eight-hour observations. We detect a faint component of diffuse polarised emission in the stacked cube, which was not detected previously. Additionally, we verify the reliability of the ionospheric Faraday rotation corrections estimated from the satellite-based total electron content measurements to be of ∼0.05 Cyrillic small letter GHEad m-2. We also demonstrate that diffuse polarised emission itself can be used to account for the relative ionospheric Faraday rotation corrections with respect to a reference observation.

ISM: magnetic fields

Techniques: polarimetric

Radio continuum: ISM

ISM: structure

ISM: general

Techniques: interferometric

Författare

Iva Šnidariać

Ruder Boskovic Institute

Vibor Jeliać

Ruder Boskovic Institute

M. Mevius

Netherlands Institute for Radio Astronomy (ASTRON)

M. Brentjens

Netherlands Institute for Radio Astronomy (ASTRON)

Ana Erceg

Ruder Boskovic Institute

T. W. Shimwell

Netherlands Institute for Radio Astronomy (ASTRON)

Universiteit Leiden

Sara Piras

Chalmers, Rymd-, geo- och miljövetenskap, Astronomi och plasmafysik

Cathy Horellou

Chalmers, Rymd-, geo- och miljövetenskap, Astronomi och plasmafysik

J. Sabater

University of Edinburgh

P.N. Best

University of Edinburgh

Andrea Bracco

Laboratoire de Physique de l’Ecole Normale Supérieure

L. Ceraj

Radboud Universiteit

M. Haverkorn

Radboud Universiteit

Shane P. Oa'sullivan

Dublin City University

Luka Turiać

Ruder Boskovic Institute

V. Vacca

Istituto nazionale di astrofisica (INAF)

Astronomy and Astrophysics

0004-6361 (ISSN) 1432-0746 (eISSN)

Vol. 674 A119

Ämneskategorier

Astronomi, astrofysik och kosmologi

Geofysik

Signalbehandling

DOI

10.1051/0004-6361/202245124

Mer information

Senast uppdaterat

2023-09-15