Measurements of the diffuse Galactic synchrotron spectral index and curvature from MeerKLASS pilot data

Abstract

21cm intensity mapping experiments are bringing an influx of high spectral resolution observational data in the $\sim 100$ MHz $-1$ GHz regime. We use pilot $971-1075$ MHz data from MeerKAT in single-dish mode, recently used to test the calibration and data reduction scheme of the upcoming MeerKLASS survey, to probe the spectral index of diffuse synchrotron emission below 1 GHz within $145^{\circ }<\alpha <180^{\circ }$, $-1^{\circ }<\delta <8^{\circ }$. Through comparisons with data from the OVRO Long Wavelength Array and the Maipu and MU surveys, we find an average spectral index of $-2.75<\beta <-2.71$ between 45 and 1055 MHz. By fitting for spectral curvature with a spectral index of the form $\beta +c\ln (\nu /73\mathrm{MHz})$, we measure $\beta =-2.55\pm 0.13$ and $c=-0.12\pm 0.05$ within our target field. Our results are in good agreement (within $1\sigma$) with existing measurements from experiments such as ARCADE2 and EDGES. These results show the calibration accuracy of current data and demonstrate that MeerKLASS will also be capable of achieving a secondary science goal of probing the interstellar medium.

arXiv comment17 pages, 13 figures, accepted for publication in MNRAS. Updated to match published paper (additional references and acknowledgements)

References in corpus (44)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• The NumPy array: a structure for efficient numerical computation
• HEALPix -- a Framework for High Resolution Discretization, and Fast Analysis of Data Distributed on the Sphere
• The Five-Hundred-Meter Aperture Spherical Radio Telescope (FAST) Project
• A model of diffuse Galactic Radio Emission from 10 MHz to 100 GHz
• Planck 2018 results. IV. Diffuse component separation
• Baryon Acoustic Oscillation Intensity Mapping as a Test of Dark Energy
• ARCADE 2 Measurement of the Extra-Galactic Sky Temperature at 3-90 GHz
• Late-time cosmology with 21cm intensity mapping experiments
• GLEAM: The GaLactic and Extragalactic All-sky MWA survey
• Multifrequency analysis of 21 cm fluctuations from the Era of Reionization
• The Rapid ASKAP Continuum Survey I: Design and First Results
• The Python Sky Model: software for simulating the Galactic microwave sky
• HI intensity mapping : a single dish approach
• Separation of anomalous and synchrotron emissions using WMAP polarization data
• Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Galactic Foreground Emission
• An Improved Model of Diffuse Galactic Radio Emission from 10 MHz to 5 THz
• Lack of clustering in low-redshift 21-cm intensity maps cross-correlated with 2dF galaxy densities
• HIRAX: A Probe of Dark Energy and Radio Transients
• Galactic synchrotron emission with cosmic ray propagation models
• The radio emission from the Galaxy at 22 MHz
• Neutral hydrogen surveys for high redshift galaxy clusters and proto-clusters
• All-sky Galactic radiation at 45 MHz and spectral index between 45 and 408 MHz
• A Determination of the Spectral Index of Galactic Synchrotron Emission in the 1-10 GHz range
• The 21 cm Power Spectrum from the Cosmic Dawn: First Results from the OVRO-LWA
• Toward Empirical Constraints on the Global Redshifted 21 cm Brightness Temperature During the Epoch of Reionization
• Imprints of Cosmic Rays in Multifrequency Observations of the Interstellar Emission
• The LWA1 Low Frequency Sky Survey
• The Radio Sky at Meter Wavelengths: m-Mode Analysis Imaging with the Owens Valley Long Wavelength Array
• The contribution of the Unresolved Extragalactic Radio Sources to the Brightness Temperature of the sky
• HI intensity mapping with MeerKAT: Calibration pipeline for multi-dish autocorrelation observations
• SKAO HI Intensity Mapping: Blind Foreground Subtraction Challenge
• Sparsity and adaptivity for the blind separation of partially correlated sources
• MeerKLASS: MeerKAT Large Area Synoptic Survey
• Spectral Index of the Diffuse Radio Background Between 50 and 100 MHz
• Synchrotron Spectral Curvature from 22 MHz to 23 GHz
• The C-Band All-Sky Survey (C-BASS): Design and capabilities
• Calibrating CHIME, A New Radio Interferometer to Probe Dark Energy
• BINGO: a single dish approach to 21cm intensity mapping
• Spectral index of the Galactic foreground emission in the 50-87 MHz range
• Absolute Calibration of Diffuse Radio Surveys at 45 and 150 MHz
• Spectral index of synchrotron emission: insights from the diffuse and magnetised interstellar medium
• CMB foreground measurements through broad-band radio spectro-polarimetry: prospects of the SKA-MPG telescope
• CMB foregrounds - A brief review