Matching LOFAR sources across radio bands

Abstract

Aims. With the recent preliminary release of the LOFAR LBA Sky Survey (LoLSS), the first wide-area, ultra-low frequency observations from LOFAR were published. Our aim is to combine this data set with other surveys at higher frequencies to study the spectral properties of a large sample of radio sources. Methods. We present a new cross-matching algorithm taking into account the sizes of the radio sources and apply it to the LoLSS-PR, LoTSS-DR1, LoTSS-DR2 (all LOFAR), TGSS-ADR1 (GMRT), WENSS (WSRT) and NVSS (VLA) catalogues. We then study the number of matched counterparts for LoLSS radio sources and their spectral properties. Results. We find counterparts for 22 607 (89.5%) LoLSS sources. The remaining 2 640 sources (10.5%) are identified either as an artefact in the LoLSS survey (3.6%) or flagged due to their closeness to bright sources (6.9%). We find an average spectral index of $\alpha =-0.77\pm 0.18$ between LoLSS and NVSS. Between LoLSS and LoTSS-DR2 we find $\alpha =-0.71\pm 0.31$. The average spectral index is flux density independent above $S_{54}=181$ mJy. Comparison of the spectral slopes from LoLSS--LoTSS-DR2 with LoTSS-DR2--NVSS indicates that the probed population of radio sources exhibits evidence for a negative spectral curvature.

arXiv comment13 pages, 22 figures and 2 tables. Accepted for publication in A&A

References in corpus (31)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Astropy: A Community Python Package for Astronomy
• The NumPy array: a structure for efficient numerical computation
• LOFAR: The LOw-Frequency ARray
• The GMRT 150 MHz All-sky Radio Survey: First Alternative Data Release TGSS ADR1
• Relativistic Jets in Active Galactic Nuclei
• Active Galactic Nuclei: what's in a name?
• The LOFAR Two-metre Sky Survey - II. First data release
• The LOFAR Two-metre Sky Survey -- V. Second data release
• Distant Radio Galaxies and their Environments
• Revisiting the Fanaroff-Riley dichotomy and radio-galaxy morphology with the LOFAR Two-Metre Sky Survey (LoTSS)
• The LOFAR Two-metre Sky Survey (LoTSS) III. First Data Release: optical/IR identifications and value-added catalogue
• Probabilistic Cross-Identification of Astronomical Sources
• A radio spectral index map and catalogue at 147-1400 MHz covering 80 per cent of the sky
• The X-ray -- radio alignment in the z = 2.2 radio galaxy PKS 1138--262
• The LOFAR LBA Sky Survey I. survey description and preliminary data release
• The Lockman Hole project: LOFAR observations and spectral index properties of low-frequency radio sources
• Dust and star formation in distant radio galaxies
• The LOFAR Two-metre Sky Survey Deep Fields Data Release 1: V. Survey description, source classifications and host galaxy properties
• The LOFAR Two-metre Sky Survey IV. First Data Release: Photometric redshifts and rest-frame magnitudes
• Deep Low-Frequency Radio Observations of the NOAO Bootes Field: I. Data Reduction and Catalog Construction
• The ATESP 5 GHz radio survey I. Source counts and spectral index properties of the faint radio population
• T-RaMiSu: The Two-meter Radio Mini Survey I. The Bootes Field
• 325-MHz observations of the ELAIS-N1 field using the Giant Metrewave Radio Telescope
• The LOFAR LBA Sky Survey II. First data release
• PUMA: The Positional Update and Matching Algorithm
• The nature of faint radio galaxies at high redshifts
• Ultra Steep Spectrum radio sources in the Lockman Hole: SERVS identifications and redshift distribution at the faintest radio fluxes
• Dust in 3C324
• The LOFAR LBA Sky Survey: Deep Fields I. The Boötes Field
• Optimal Probabilistic Catalogue Matching for Radio Sources

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