Astronomy and Astrophysics – Astrophysics – Cosmology and Extragalactic Astrophysics
Scientific paper
2011-08-18
2011MNRAS.418.2584
Astronomy and Astrophysics
Astrophysics
Cosmology and Extragalactic Astrophysics
6 Pages, 4 Figures, 1 Table, Accepted to MNRAS
Scientific paper
10.1111/j.1365-2966.2011.19649.x
Foreground removal is a challenge for 21-cm tomography of the high redshift Universe. We use archival GMRT data (obtained for completely different astronomical goals) to estimate the foregrounds at a redshift ~ 1. The statistic we use is the cross power spectrum between two frequencies separated by \Delta{\nu} at the angular multipole l, or equivalently the multi-frequency angular power spectrum C_l(\Delta{\nu}). An earlier measurement of C_l(\Delta{\nu}) using this data had revealed the presence of oscillatory patterns along \Delta{\nu}, which turned out to be a severe impediment for foreground removal (Ghosh et al. 2011). Using the same data, in this paper we show that it is possible to considerably reduce these oscillations by suppressing the sidelobe response of the primary antenna elements. The suppression works best at the angular multipoles l for which there is a dense sampling of the u-v plane. For three angular multipoles l = 1405, 1602 and 1876, this sidelobe suppression along with a low order polynomial fitting completely results in residuals of (\leq 0.02 mK^2), consistent with the noise at the 3{\sigma} level. Since the polynomial fitting is done after estimation of the power spectrum it can be ensured that the estimation of the HI signal is not biased. The corresponding 99% upper limit on the HI signal is xHI b \leq 2.9, where xHI is the mean neutral fraction and b is the bias.
Ali Saiyad SK.
Bharadwaj Somnath
Chengalur Jayaram N.
Ghosh Abhik
No associations
LandOfFree
Improved foreground removal in GMRT 610 MHz observations towards redshifted 21-cm tomography does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Improved foreground removal in GMRT 610 MHz observations towards redshifted 21-cm tomography, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Improved foreground removal in GMRT 610 MHz observations towards redshifted 21-cm tomography will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-181080