The angular power spectrum measurement of the Galactic synchrotron emission in two fields of the TGSS survey

Abstract

Characterizing the diffuse Galactic synchrotron emission at arcminute angular scales is needed to reliably remove foregrounds in cosmological 21-cm measurements. The study of this emission is also interesting in its own right. Here, we quantify the fluctuations of the diffuse Galactic synchrotron emission using visibility data for two of the fields observed by the TIFR GMRT Sky Survey (TGSS). We have used the 2D Tapered Gridded Estimator (TGE) to estimate the angular power spectrum $(C_{\ell })$ from the visibilities. We find that the sky signal, after subtracting the point sources, is likely dominated by the diffuse Galactic synchrotron radiation across the angular multipole range $240\le \ell \lesssim 500$. We present a power law fit, $C_{\ell }=A\times (\frac{1000}{l}{)}^{\beta }$, to the measured $C_{\ell }$ over this $\ell$ range. We find that $(A,\beta )$ have values $(356\pm 109\mathrm{m}{\mathrm{K}}^2,2.8\pm 0.3)$ and $(54\pm 26\mathrm{m}{\mathrm{K}}^2,2.2\pm 0.4)$ in the two fields. For the second field, however, there is indication of a significant residual point source contribution, and for this field we interpret the measured $C_{\ell }$ as an upper limit for the diffuse Galactic synchrotron emission. While in both fields the slopes are consistent with earlier measurements, the second field appears to have an amplitude which is considerably smaller compared to similar measurements in other parts of the sky.

6 pages, 1 table, 3 figures. Accepted for publication in MNRAS Letters. The definitive version will be available at http://mnrasl.oxfordjournals.org/

References in corpus (7)

• Cosmology at Low Frequencies: The 21 cm Transition and the High-Redshift Universe
• On using visibility correlations to probe the HI distribution from the dark ages to the present epoch I: Formalism and the expected signal
• Foregrounds for redshifted 21 cm studies of reionization: GMRT 153 MHz observations
• Characterizing Foreground for redshifted 21-cm radiation: 150 MHz GMRT observations
• Visibility based angular power spectrum estimation in low frequency radio interferometric observations
• GMRT observation towards detecting the Post-reionization 21-cm signal
• The impact of Galactic synchrotron emission on CMB anisotropy measurements. I. Angular power spectrum analysis of total intensity all-sky surveys

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