Bulletin of the Astronomical Society of India
S. K. Sirothia1*, G. Swarup1 and H. Shukla2
1NCRA-TIFR, Ganeshkhind, Pune 411007,India
2Lawrence Berkley National Laboratory, 1 Cyclotron Road,Mail Stop 50R6048, Berkley, CA 94720, USA
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We describe observations of 20 square degree region towards the WMAP cold spot (l=207.80, b=-56.30; RA = 03h15m, Dec. = -19d35) made with the Giant Metrewave Radio Telescope at 625 MHz, and 325 MHz. We find deficiency in the number counts of radio sources towards the cold spot in a 3 sq. deg region at position (l= 206.600, b= -54.740), similar to that reported by Rudnick et al. (2007). We find that the average value of the spectral index of radio sources in the 3 sq. deg region (’Radio Cold Spot’) is significantly flatter than that elsewhere in the field observed by us of about 20 square degrees. Further, most of the radio sources in the ≈ 3 sq. deg region are relatively compact compared to radio sources elsewhere. It may be noted that the cold spot indicates significant deviation of the CMB from Gaussianity and has been confirmed by the recently released Planck data. We discuss significance of our results.