The Apertif science verification campaign: Characteristics of polarised radio sources
Journal article, 2022

Context. The characteristics of the polarised radio sky are a key ingredient in constraining evolutionary models of magnetic fields in the Universe and their role in feedback processes. The origin of the polarised emission and the characteristics of the intergalactic medium on the line of sight can be investigated using large samples of polarised sources. Ancillary infrared (IR) and optical data can be used to study the nature of the emitting objects. Aims. We analyse five early science datasets from the APERture Tile in Focus (Apertif) phased array feed system to verify the polarisation capabilities of Apertif in view of future larger data releases. We aim to characterise the source population of the polarised sky in the L-Band using polarised source information in combination with IR and optical data.
Methods. We use automatic routines to generate full field-of-view Q- and U-cubes and perform rotation measure (RM)-Synthesis, source finding, and cross-matching with published radio, optical, and IR data to generate polarised source catalogues. All sources were inspected individually by eye for verification of their IR and optical counterparts. Spectral energy distribution (SED)-fitting routines were used to determine photometric redshifts, star-formation rates, and galaxy masses. IR colour information was used to classify sources as active galactic nuclei (AGN) or star-forming-dominated and early- or late-type.
Results. We surveyed an area of 56 deg2 and detected 1357 polarised source components in 1170 sources. The fraction of polarised sources is 10.57% with a median fractional polarisation of 4.70 ± 0.14%. We confirmed the reliability of the Apertif measurements by comparing them with polarised cross-identified NVSS sources. Average RMs of the individual fields lie within the error of the best Milky Way foreground measurements. All of our polarised sources were found to be dominated by AGN activity in the radio regime with most of them being radio-loud (79%) and of the Fanaroff-Riley (FR)II class (87%). The host galaxies of our polarised source sample are dominated by intermediate disc and star-forming disc galaxies. The contribution of star formation to the radio emission is on the order of a few percent for 10% of the polarised sources while for 90% it is completely dominated by the AGN. We do not see any change in fractional polarisation for different star-formation rates of the AGN host galaxies.
Conclusions. The Apertif system is suitable for large-area high-sensitivity polarised sky surveys. The data products of the polarisation analysis pipeline can be used to investigate the Milky Way magnetic field on projected scales of several arcminutes as well as the origin of the polarised emission in AGN and the properties of their host galaxies.

Surveys

Galaxies: magnetic fields

Methods: data analysis

Polarization

Galaxies: active

Author

B. Adebahr

Ruhr-Universität Bochum

A. Berger

Ruhr-Universität Bochum

E. A.K. Adams

University of Groningen

Netherlands Institute for Radio Astronomy (ASTRON)

K. M. Hess

Netherlands Institute for Radio Astronomy (ASTRON)

University of Groningen

Institute of Astrophysics of Andalusia (IAA)

W.J.G. de Blok

University of Groningen

University of Cape Town

Netherlands Institute for Radio Astronomy (ASTRON)

H. Dénes

Netherlands Institute for Radio Astronomy (ASTRON)

V. A. Moss

Netherlands Institute for Radio Astronomy (ASTRON)

Commonwealth Scientific and Industrial Research Organisation (CSIRO)

The University of Sydney

R. Schulz

Netherlands Institute for Radio Astronomy (ASTRON)

J. M. van der Hulst

Netherlands Institute for Radio Astronomy (ASTRON)

L. Connor

Netherlands Institute for Radio Astronomy (ASTRON)

California Institute of Technology (Caltech)

Sieds Damstra

Netherlands Institute for Radio Astronomy (ASTRON)

B. Hut

Netherlands Institute for Radio Astronomy (ASTRON)

Marianna Ivashina

Chalmers, Electrical Engineering, Communication, Antennas and Optical Networks

G. M. Loose

Netherlands Institute for Radio Astronomy (ASTRON)

Y. Maan

Netherlands Institute for Radio Astronomy (ASTRON)

National Centre for Radio Astrophysics India

Mika

Netherlands Institute for Radio Astronomy (ASTRON)

H. Mulder

Netherlands Institute for Radio Astronomy (ASTRON)

M. J. Norden

Netherlands Institute for Radio Astronomy (ASTRON)

L. C. Oostrum

Netherlands Institute for Radio Astronomy (ASTRON)

Netherlands eScience Center

Anton Pannekoek Institute for Astronomy

E. Orrú

Netherlands Institute for Radio Astronomy (ASTRON)

Mark Ruiter

Netherlands Institute for Radio Astronomy (ASTRON)

R. Smits

Netherlands Institute for Radio Astronomy (ASTRON)

W. van Cappellen

Netherlands Institute for Radio Astronomy (ASTRON)

J. van Leeuwen

Anton Pannekoek Institute for Astronomy

Netherlands Institute for Radio Astronomy (ASTRON)

N. Vermaas

Netherlands Institute for Radio Astronomy (ASTRON)

D. Vohl

University of Amsterdam

Netherlands Institute for Radio Astronomy (ASTRON)

J. Ziemke

Netherlands Institute for Radio Astronomy (ASTRON)

University of Oslo

Astronomy and Astrophysics

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

Vol. 663 A103

Subject Categories

Accelerator Physics and Instrumentation

Astronomy, Astrophysics and Cosmology

Environmental Sciences

DOI

10.1051/0004-6361/202243201

More information

Latest update

8/3/2022 2