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GMRT observations of a sample of extragalactic radio sources at 618 MHz

Assoc. Prof Somanah R University of Mauritius Dr. Oozeer Nadeem HartRAO. GMRT observations of a sample of extragalactic radio sources at 618 MHz. Low frequency survey The Mauritius Radio Telescope Our sample GMRT observations Preliminary Analysis & Results Conclusion. Outline.

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GMRT observations of a sample of extragalactic radio sources at 618 MHz

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  1. Assoc. Prof Somanah R University of Mauritius Dr. Oozeer Nadeem HartRAO GMRT observations of a sample of extragalactic radio sources at 618 MHz

  2. Low frequency survey The Mauritius Radio Telescope Our sample GMRT observations Preliminary Analysis & Results Conclusion Outline

  3. utility in identifying classes of objects that can be observed at other wavelengths less affected by optical depth and beaming provides samples with an isotropic source distribution. particular interest for finding radio galaxies, especially those at large redshifts. Low frequency survey

  4. AGN

  5. Analytical model of FRII source Q - energy supplied per unit time U - energy density r - distance frome core Assume density IGM = k r - α

  6. The Mauritius Radio Telescope(MRT)‏ • T-shaped Fourier synthesis non-coplanar array • 2048 m long East-West (EW) arm • 880 m long North-South (NS) arm • operating at 151.5 Mhz. • EW - 1024 fixed helices arranged in 32 groups at the same height but the different groups are at not co-planar.

  7. Elements – Helical antenna

  8. MRT layout

  9. DATA processing steps at MRT • Data Selection • Calibration • Fourier Transform • Deconvolution • Source extraction

  10. Dirty Image

  11. CLEANed image

  12. Galactic centre at 151.5 MHz

  13. SNRs in the galactic plane

  14. VELA SNR

  15. Extragalactic radio sources from MRT survey

  16. Spectra

  17. Giant Metre wave radio Telescope • Pune India • 30 parabolic mesh grid dish of 45m diameter each • Y-shaped • Shortest spacing 60m (central square)‏ • Longest spacing 25 km

  18. GMRT follow upSample • selected from the MRC using similar criteria as the MRC/1Jy sample • 14h04m < RA < 20h20m • -30o < dec < -20o • No of sources 117 sources • Frequency 618 Mhz • Snapshots 3 x 15 min each

  19. Sample Region

  20. MRC 1404-209 MRC 1947-284

  21. MRC 1410-298 MRC 1421-272

  22. Spectra of some sources

  23. Results • By considering the spectral index a of the sources in the MRC/1Jy-B sample (107 sources), between 1400 MHz and the 408 MHz: • 27.3% of the sources show ultra steep spectrum • 67.3% show steep spectrum features and • remaining, 4.6% were flat spectrum sources.

  24. Morphology • 41% - singles or unresolved, • 49% - apparent double structures • 5% - triple sources • 5% - complex structures.

  25. MRC 1925-296

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