Degree-Scale Galactic Radio Emission at 122 MHz around the North Celestial Pole with LOFAR-AARTFAAC

Abstract

Aims: Contamination from bright diffuse Galactic thermal and non-thermal radio emission poses crucial challenges in experiments aiming to measure the 21-cm signal of neutral hydrogen from the Cosmic Dawn and Epoch of Reionization. If not included in calibration, this diffuse emission can severely impact the analysis and signal extraction in 21-cm experiments. We examine large-scale diffuse Galactic emission at 122~MHz, around the North Celestial Pole, using the AARTFAAC-HBA system. Methods: In this pilot project, we present the first-ever wide-field image produced with a single sub-band of the data recorded with the AARTFAAC-HBA. We demonstrate two methods: multiscale CLEAN and shapelet decomposition, to model the diffuse emission revealed in the image. We use angular power spectrum metrics to quantify different components of the emission and compare the performance of the two diffuse structure modelling approaches. Results: We observe that the point sources dominate the angular power spectrum ($\ell (\ell +1)C_{\ell }/2\pi \equiv {\Delta }^2(\ell )$) of the emission in the field on scales $\ell \gtrsim 60$ ($\lesssim 3$~degree). The angular power spectrum after subtraction of compact sources is flat within $20\lesssim \ell \lesssim 200$ range, suggesting that the residual power is dominated by the diffuse emission on scales $\ell \lesssim 200$. The residual diffuse emission has a brightness temperature variance of ${\Delta }_{\ell =180}^2=(145.64\pm 13.61){\mathrm{K}}^2$ at 122~MHz on angular scales of 1~degree, and is consistent with a power-law following $C_{\ell }\propto {\ell }^{-2.0}$ in $20\lesssim \ell \lesssim 200$ range. We also find that, in the current setup, the multiscale CLEAN is suitable to model the compact and diffuse structures on a wide range of angular scales, whereas the shapelet decomposition method better models the large scales, which are of the order of a few degrees and wider.

arXiv comment11 pages, 9 figures, accepted (A&A)

References in corpus (60)

• Astropy: A Community Python Package for Astronomy
• LOFAR: The LOw-Frequency ARray
• Cosmology at Low Frequencies: The 21 cm Transition and the High-Redshift Universe
• An absorption profile centred at 78 megahertz in the sky-averaged spectrum
• WSClean: an implementation of a fast, generic wide-field imager for radio astronomy
• 21-cm Tomography of the Intergalactic Medium at High Redshift
• Hydrogen Epoch of Reionization Array (HERA)
• Multi-Scale CLEAN deconvolution of radio synthesis images
• 21 Centimeter Fluctuations from Cosmic Gas at High Redshifts
• The VLA Low-frequency Sky Survey
• A morphological algorithm for improving radio-frequency interference detection
• Bright Source Subtraction Requirements For Redshifted 21 cm Measurements
• Shapelets: I. A Method for Image Analysis
• A method for subtracting foregrounds from multi-frequency CMB sky maps
• A simulation calibrated limit on the HI power spectrum from the GMRT Epoch of Reionization experiment
• A Per-Baseline, Delay-Spectrum Technique for Accessing the 21cm Cosmic Reionization Signature
• Science with the Murchison Widefield Array
• An optimized algorithm for multi-scale wideband deconvolution of radio astronomical images
• Four Fundamental Foreground Power Spectrum Shapes for 21 cm Cosmology Observations
• Improved upper limits on the 21-cm signal power spectrum of neutral hydrogen at $\mathbf{z}\approx 9.1$ from LOFAR
• Upper limits on the 21-cm Epoch of Reionization power spectrum from one night with LOFAR
• Measuring Polarization In Cosmic Microwave Background
• Imaging the Epoch of Reionization: limitations from foreground confusion and imaging algorithms
• Deep multi-redshift limits on Epoch of Reionisation 21cm Power Spectra from Four Seasons of Murchison Widefield Array Observations
• Radio Foregrounds for the 21cm Tomography of the Neutral Intergalactic Medium at High Redshifts
• The impact of point source subtraction residuals on 21 cm Epoch of Reionization estimation
• Overcoming real-world obstacles in 21 cm power spectrum estimation: A method demonstration and results from early Murchison Widefield Array data
• Calibration Requirements for Detecting the 21 cm Epoch of Reionization Power Spectrum and Implications for the SKA
• Foregrounds for observations of the cosmological 21 cm line: I. First Westerbork measurements of Galactic emission at 150 MHz in a low latitude field
• Foreground Removal using FastICA: A Showcase of LOFAR-EoR
• Initial deep LOFAR observations of Epoch of Reionization windows: I. The North Celestial Pole
• Improving the Epoch of Reionization Power Spectrum Results from Murchison Widefield Array Season 1 Observations
• The Scale of the Problem : Recovering Images of Reionization with GMCA
• Duchamp: a 3D source finder for spectral-line data
• Bayesian constraints on the global 21-cm signal from the Cosmic Dawn
• The 21 cm Power Spectrum from the Cosmic Dawn: First Results from the OVRO-LWA
• Foregrounds for observations of the cosmological 21 cm line: II. Westerbork observations of the fields around 3C196 and the North Celestial Pole
• Characterizing Foreground for redshifted 21-cm radiation: 150 MHz GMRT observations
• The Impact of Modeling Errors on Interferometer Calibration for 21 cm Power Spectra
• Systematic biases in low frequency radio interferometric data due to calibration: the LOFAR EoR case
• The first power spectrum limit on the 21-cm signal of neutral hydrogen during the Cosmic Dawn at z=20-25 from LOFAR
• Non-parametric foreground subtraction for 21cm epoch of reionization experiments
• The LWA1 Low Frequency Sky Survey
• The Fundamental Multi-Baseline Mode-Mixing Foreground in 21 cm EoR Observations
• Fundamental Limitations on the Calibration of Redundant 21 cm Cosmology Instruments and Implications for HERA and the SKA
• Distributed Radio Interferometric Calibration
• The Radio Sky at Meter Wavelengths: m-Mode Analysis Imaging with the Owens Valley Long Wavelength Array
• ARCADE 2 Observations of Galactic Radio Emission
• Understanding the Diversity of 21 cm Cosmology Analyses
• SARAS 3 CD/EoR Radiometer: Design and Performance of the Receiver
• The AARTFAAC Cosmic Explorer: observations of the 21-cm power spectrum in the EDGES absorption trough
• Quantifying Suppression of the Cosmological 21-cm Signal due to Direction Dependent Gain Calibration in Radio Interferometers
• Polarization leakage in epoch of reionization windows: II. Primary beam model and direction dependent calibration
• Polarization leakage in epoch of reionization windows: III. Wide-field effects of narrow-field arrays
• Constraining Polarized Foregrounds for EOR Experiments II: Polarization Leakage Simulations in the Avoidance Scheme
• A Map of Diffuse Radio Emission at 182 MHz to Enhance Epoch of Reionization Observations in the Southern Hemisphere
• Modelling and peeling extended sources with shapelets: a Fornax A case study
• Measurement of the Anisotropy Power Spectrum of the Radio Synchrotron Background
• AARTFAAC Flux Density Calibration and Northern Hemisphere Catalogue at 60 MHz
• Exploring the Cosmic Dawn with NenuFAR

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