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The characteristics of the polarised radio sky are a key ingredient to constrain 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 in the line-of-sight can be investigated using large samples of polarised sources. Ancillary infrared and optical data can be used to study the nature of the emitting objects. 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 infrared and optical data. We use automatic routines to generate full field-of-view Q- and U-cubes and perform RM-Synthesis, source finding and cross-matching with published radio, optical and infrared data to generate polarised source catalogues. All sources were inspected individually by eye for a verification of their infrared and optical counterparts. SED-fitting routines were used to determine photometric redhifts, star-formation rates and galaxy masses. Infrared colour information was used to classify sources as AGN or star-forming dominated and early- or late-type. We surveyed an area of 56 deg^2 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 Rotation Measures 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 FRII-class (87%). Our polarised source sample is dominated by late-type spiral 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 identified a possible decrease of fractional polarisation towards higher star-formation rates of the AGN host galaxies. 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.
This table has an associated publication. If you use data from it, it may be appropriate to reference 2022A&A...663A.103A (ADS BibTeX entry for the publication) either in addition to or instead of the service reference.
To cite the table as such, we suggest the following BibTeX entry:
@MISC{vo:svc_main, year=2022, title={The Apertif Science Verification Campaign}, author={Adebahr, B. and Berger, A. and Adams, E. A. K. and Hess, K. M. and Dénes, H. D. and Moss, V. A. and Schulz, R. and van der Hulst, J. M. and Damstra, S. and Ivashina, M. V. and Loose, G. M. and Maan, Y and Mika, A and Mulder, H and Oostrum, L. C. and Orrú, E. and Ruiter, M. and Smits, R. and Leeuwen, J and Vohl, D. and Ziemke, J.}, url={https://vo.astron.nl/tableinfo/svc.main}, howpublished={{VO} resource provided by the The VO @ {ASTRON}} }
Sorted by DB column index. [Sort alphabetically]
Name | Table Head | Description | Unit | UCD |
---|---|---|---|---|
accref | Product key | Access key for the data | N/A | N/A |
owner | Owner | Owner of the data | N/A | N/A |
embargo | Embargo ends | Date the data will become/became public | a | N/A |
mime | Type | MIME type of the file served | N/A | meta.code.mime |
accsize | File size | Size of the data in bytes | byte | VOX:Image_FileSize |
index | Index | Source index | N/A | meta.id;meta.main |
ID | Id | Source identifier concatenated from a prefix and the right ascension and declination of the central position of the source in degrees | N/A | meta.id |
RA | Ra | Right Ascension of the central position of the source in degrees. | deg | pos.eq.ra;meta.main |
RA_err | Ra_err | Uncertainty of the right Ascension of the central position of the source in degrees. | deg | stat.error;pos.eq.ra;meta.main |
DEC | Dec | Declination of the central position of the source in degrees. | deg | pos.eq.dec;meta.main |
DEC_err | Dec_err | Uncertainty of the declination of the central position of the source in degrees. | deg | stat.error;pos.eq.dec;meta.main |
IPI | PI | Integrated polarised intensity of the source in units of Jy. | Jy | phys.polarization;meta.main |
IPI_err | Ipi_err | Uncertainty of the integrated polarised intensity of the source in units of Jy. | Jy | stat.error;phys.polarization;meta.main |
S_Code | S_code | S for unresolved sources, E for resolved sources | N/A | meta.code |
RA_Comp | Ra_comp | Right ascension of the position of the source component in degrees. | deg | pos.eq.ra |
RA_Comp_err | Ra_comp_err | Uncertainty of the right ascension of the position of the source component in degrees. | deg | stat.error;pos.eq.ra |
DEC_Comp | Dec_comp | Declination of the position of the source component in degrees. | deg | pos.eq.dec |
DEC_Comp_err | Dec_comp_err | Uncertainty of the declination of the position of the source component in degrees. | deg | stat.error;pos.eq.ra |
PI_Comp | Pi_comp | Polarised emission of the source component in units of Jy | Jy | phys.polarization |
PI_Comp_err | Pi_comp_err | Uncertainty of the polarised emission of the source component in units of Jy | Jy | stat.error;phys.polarization |
PI_Comp_Peak | Pi_comp_peak | Peak polarised emission of the source component in units of Jy. | Jy | phys.polarization;stat.max |
PI_Comp_Peak_err | Pi_comp_peak_err | Uncertainty of the peak polarised emission of the source component in units of Jy. | Jy | stat.error;phys.polarization;stat.max |
PI_rms | Pi_rms | Standard deviation at the peak position of the source component in units of Jy/beam. | Jy/beam | stat.stdev;phys.polarization |
RM_Comp | Rm_comp | Rotation measure at the peak position of the source component in units of rad/m**2. | rad/m**2 | phys.polarization.rotmeasure |
RM_Comp_err | Rm_comp_err | Uncertainty of the rotation measure at the peak position of the source component in units of rad/m**2. | rad/m**2 | stat.error;phys.polarization.rotmeasure |
TP_ID | Tp_id | Total power source identifier. For internal usage only. Was used for cross-matching. | N/A | meta |
TP | Tp | Radio continuum flux of the cross-matched total power counterpart in units of Jy. | Jy | phot.flux.density;em.radio;spect.continuum |
TP_err | Tp_err | Uncertainty of the radio continuum flux of the cross-matched total power counterpart in units of Jy. | Jy | stat.error;phot.flux.density;em.radio;spect.continuum |
RA_TP | Ra_tp | Right ascension of the central position of the total power counterpart in units of degrees. | deg | pos.eq.ra |
RA_TP_err | Ra_tp_err | Uncertainty of the right ascension of the central position of the total power counterpart in units of degrees. | deg | stat.error;pos.eq.ra |
DEC_TP | Dec_tp | Declination of the central position of the total power counterpart in units of degrees. | deg | pos.eq.dec |
DEC_TP_err | Dec_tp_err | Uncertainty of the declination of the central position of the total power counterpart in units of degrees. | deg | stat.error;pos.eq.dec |
FP | Fp | Fractional polarisation of the source derived from the integrated polarised and total power fluxes. | N/A | phys.polarization |
FP_err | Fp_err | Uncertainty of the fractional polarisation of the source derived from the integrated polarised and total power fluxes. | N/A | stat.error;phys.polarization |
NVSS_I | Nvss_i | Total power flux of a possible NVSS counterpart in units of Jy. | Jy | phot.flux.density |
NVSS_I_err | Nvss_i_err | Uncertainty of the total power flux of a possible NVSS counterpart in units of Jy. | Jy | stat.error;phot.flux.density |
NVSS_PI | Nvss_pi | Polarised intensity flux of a possible NVSS counterpart in units of Jy. | Jy | phot.flux.density |
NVSS_PI_err | Nvss_pi_err | Uncertainty of the polarised intensity flux of a possible NVSS counterpart in units of Jy. | Jy | stat.error;phot.flux.density |
NVSS_FP | Nvss_fp | Fractional polarisation of a possible NVSS counterpart. | N/A | phys.polarization |
NVSS_FP_err | Nvss_fp_err | Uncertainty of the fractional polarisation of a possible NVSS counterpart. | N/A | stat.error;phys.polarization |
NVSS_RM | Nvss_rm | Rotation measure of a possible NVSS counterpart in units of rad/m**2. | rad/m**2 | phys.polarization.rotMeasure |
NVSS_RM_err | Nvss_rm_err | Uncertainty of the rotation measure of a possible NVSS counterpart in units of rad/m**2. | rad/m**2 | stat.error;phys.polarization.rotMeasure |
NVSS_RA | Nvss_ra | Right ascension of a possible NVSS counterpart in units of degrees. | deg | pos.eq.ra |
NVSS_RA_err | Nvss_ra_err | Uncertainty of the right ascension of a possible NVSS counterpart in units of degrees. | deg | stat.error;pos.eq.ra |
NVSS_DEC | Nvss_dec | Declination of a possible NVSS counterpart in units of degrees. | deg | pos.eq.dec |
NVSS_DEC_err | Nvss_dec_err | Uncertainty of the declination of a possible NVSS counterpart in units of degrees. | deg | stat.error;pos.eq.dec |
WISE_ID | Wise_id | AllWISE ID of a possible counterpart. | N/A | meta.id |
WISE_RA | Wise_ra | Right ascension of a possible AllWISE counterpart in units of degrees. | deg | pos.eq.ra |
WISE_RA_err | Wise_ra_err | Uncertainty of the right ascension of a possible AllWISE counterpart in units of degrees. | deg | stat.error;pos.eq.ra |
WISE_DEC | Wise_dec | Declination of a possible AllWISE counterpart in units of degrees. | deg | pos.eq.dec |
WISE_DEC_err | Wise_dec_err | Uncertainty of the declination of a possible AllWISE counterpart in units of degrees. | deg | stat.error;pos.eq.dec |
WISE_Flux_3_4 | Wise_flux_3_4 | Brightness of a possible AllWISE counterpart in units of mag at 3.4μm. | mag | phot.mag;em.IR.3-4um |
WISE_Flux_3_4_err | Wise_flux_3_4_err | Uncertainty of the brightness of a possible AllWISE counterpart in units of mag at 3.4μm. | mag | stat.error;phot.mag;em.IR.3-4um |
WISE_SNR_3_4 | Wise_snr_3_4 | Signal-to-noise ratio of a possible AllWISE counterpart in units of mag at 3.4μm. | mag | stat.snr;phot.mag;em.IR.3-4um |
WISE_Flux_4_6 | Wise_flux_4_6 | Brightness of a possible AllWISE counterpart in units of mag at 4.6μm. | mag | phot.mag;em.IR.4-8um |
WISE_Flux_4_6_err | Wise_flux_4_6_err | Uncertainty of the brightness of a possible AllWISE counterpart in units of mag at 4.6μm. | mag | stat.error;phot.mag;em.IR.4-8um |
WISE_SNR_4_6 | Wise_snr_4_6 | Signal-to-noise ratio of a possible AllWISE counterpart in units of mag at 4.6μm. | mag | stat.snr;phot.mag;em.IR.4-8um |
WISE_Flux_12 | Wise_flux_12 | Brightness of a possible AllWISE counterpart in units of mag at 12μm. | mag | phot.mag;em.IR.8-15um |
WISE_Flux_12_err | Wise_flux_12_err | Uncertainty of the brightness of a possible AllWISE counterpart in units of mag at 12μm. | mag | stat.error;phot.mag;em.IR.8-15um |
WISE_SNR_12 | Wise_snr_12 | Signal-to-noise ratio of a possible AllWISE counterpart in units of mag at 12μm. | mag | stat.snr;phot.mag;em.IR.8-15um |
WISE_Flux_22 | Wise_flux_22 | Brightness of a possible AllWISE counterpart in units of mag at 22μm. | mag | phot.mag;em.IR.15-30um |
WISE_Flux_22_err | Wise_flux_22_err | Uncertainty of the brightness of a possible AllWISE counterpart in units of mag at 22μm. | mag | stat.error;phot.mag;em.IR.15-30um |
WISE_SNR_22 | Wise_snr_22 | Signal-to-noise ratio of a possible AllWISE counterpart in units of mag at 22μm. | mag | stat.snr;phot.mag;em.IR.15-30um |
SDSS_ID | Sdss_id | SDSS DR16 ID of a possible counterpart. | N/A | meta.id |
SDSS_RA | Sdss_ra | Right ascension of a possible SDSS DR16 counterpart in units of degrees. | deg | pos.eq.ra |
SDSS_DEC | Sdss_dec | Declination of a possible SDSS DR16 counterpart in units of degrees. | deg | pos.eq.dec |
SDSS_Flux_U | Sdss_flux_u | Brightness of a possible SDSS DR16 counterpart in units of mag in the U filter. | mag | phot.mag;em.opt.U |
SDSS_Flux_U_err | Sdss_flux_u_err | Uncertainty of the brightness of a possible SDSS DR16 counterpart in units of mag in the U filter. | mag | stat.error;phot.mag;em.opt.U |
SDSS_Flux_G | Sdss_flux_g | Brightness of a possible SDSS DR16 counterpart in units of mag in the G filter. | mag | phot.mag;em.opt.B |
SDSS_Flux_G_err | Sdss_flux_g_err | Uncertainty of the brightness of a possible SDSS DR16 counterpart in units of mag in the G filter. | mag | stat.error;phot.mag;em.opt.B |
SDSS_Flux_R | Sdss_flux_r | Brightness of a possible SDSS DR16 counterpart in units of mag in the R filter. | mag | phot.mag;em.opt.R |
SDSS_Flux_R_err | Sdss_flux_r_err | Uncertainty of the brightness of a possible SDSS DR16 counterpart in units of mag in the R filter. | mag | stat.error;phot.mag;em.opt.R |
SDSS_Flux_I | Sdss_flux_i | Brightness of a possible SDSS DR16 counterpart in units of mag in the I filter. | mag | phot.mag;em.opt.R |
SDSS_Flux_I_err | Sdss_flux_i_err | Uncertainty of the brightness of a possible SDSS DR16 counterpart in units of mag in the I filter. | mag | stat.error;phot.mag;em.opt.R |
SDSS_Flux_Z | Sdss_flux_z | Brightness of a possible SDSS DR16 counterpart in units of mag in the Z filter. | mag | phot.mag;em.opt.I |
SDSS_Flux_Z_err | Sdss_flux_z_err | Uncertainty of the brightness of a possible SDSS DR16 counterpart in units of mag in the Z filter. | mag | stat.error;phot.mag;em.opt.I |
SDSS_z | Sdss_z | Photometric or if available sprectroscopic redshift of a possible SDSS DR16 counterpart. | N/A | src.redshift.phot |
SDSS_z_err | Sdss_z_err | Uncertainty of the photometric or if available sprectroscopic redshift of a possible SDSS DR16 counterpart. | N/A | stat.error;src.redshift.phot |
Columns that are parts of indices are marked like this.
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The characteristics of the polarised radio sky are a key ingredient to constrain 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 in the line-of-sight can be investigated using large samples of polarised sources. Ancillary infrared and optical data can be used to study the nature of the emitting objects. 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 infrared and optical data. We use automatic routines to generate full field-of-view Q- and U-cubes and perform RM-Synthesis, source finding and cross-matching with published radio, optical and infrared data to generate polarised source catalogues. All sources were inspected individually by eye for a verification of their infrared and optical counterparts. SED-fitting routines were used to determine photometric redhifts, star-formation rates and galaxy masses. Infrared colour information was used to classify sources as AGN or star-forming dominated and early- or late-type. We surveyed an area of 56 deg^2 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 Rotation Measures 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 FRII-class (87%). Our polarised source sample is dominated by late-type spiral 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 identified a possible decrease of fractional polarisation towards higher star-formation rates of the AGN host galaxies. 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.