The angular power spectrum measurement of the Galactic synchrotron
  emission in two fields of the TGSS survey
  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,
$C_{\ell}=A\times\big(\frac{1000}{l}\big)^{\beta}$, to the measured $C_{\ell}$
over this $\ell$ range. We find that $(A,\beta)$ have values $(356\pm109~{\rm
mK^2},2.8\pm0.3)$ and $(54\pm26~{\rm mK^2},2.2\pm0.4)$ 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.
