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EVLA L-Band Spectral-Line Science Below 1200 MHz

EVLA L-Band Spectral-Line Science Below 1200 MHz. Emmanuel Momjian NRAO-Socorro. The VLA @ L-band. The VLA L-band system has: OMT bandwidth of 1200-1800 MHz. LNA bandwidth of 1200-1800 MHz. Post-Amp bandwidth of 1200-1800 MHz. VLA antennas can tune between 1225 and 1900 MHz.

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EVLA L-Band Spectral-Line Science Below 1200 MHz

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  1. EVLA L-Band Spectral-Line Science Below 1200 MHz Emmanuel Momjian NRAO-Socorro

  2. The VLA @ L-band • The VLA L-band system has: • OMT bandwidth of 1200-1800 MHz. • LNA bandwidth of 1200-1800 MHz. • Post-Amp bandwidth of 1200-1800 MHz. • VLA antennas can tune between 1225 and 1900 MHz.

  3. The VLA @ L-band • The VLA can also tune between 1100 and 1225 MHz, but with limited capability. Perley & Hayward 2008 The poor sensitivity windows are caused by resonances within VLA’s dielectric phase shifter and/or microwave lens.

  4. The EVLA @ L-band • EVLA antennas will tune between 930-2000 MHz. • Currently, all EVLA antennas, except for one, use the OMTs of the VLA. However, • these EVLA antennas do not have the microwave lens of the VLA, and • the dielectic phase shifter is replaced with a quadrature hybrid.

  5. Interim EVLA L-Band Sensitivity Interim EVLA ? EVLA

  6. RFI at L-band B. Hesman

  7. RFI (960-1200 MHz) B. Hesman

  8. RFI • The RFI below 1150 MHz is primarily due to radar transponders used for aeronautical navigation. • The strongest are at 1090 (air to ground) and 1030 (ground to air). • The others are due to civilian DMEs and Military TACAN systems located every 500 kHz between 1025 and 1150 MHz.

  9. Science Below 1200 MHz • To test whether radio astronomical science can be delivered at the lowest frequencies of the L-band, we observed HI absorption lines at: • 1139 MHz; a frequency that the whole array can observe. • 1082 MHz; a frequency that only EVLA antennas can observe. • 1019 MHz; a frequency that only EVLA antennas can observe.

  10. PKS 1413+135 • z=0.2467 (HI frequency at ~1139 MHz). • Total time 1 hours (~75% on target) in B-configuration starting at ~7 am MST. • Bandwidth 3.1 MHz with 127 spectral channels.

  11. PKS 1413+135 RFI Short baseline Intermediate baseline Long baseline • Short baselines are clearly affected by the navigation transponders. • The pulses are 3.5 microsecond long (1.1 km) separated by 12 microsecond.

  12. PKS 1413+135 • rms = 4.7 mJy/bm/ch • Theoretical value = 2.5 mJy/bm/ch

  13. RFI: D-configuration PKS 1413+135 B-conf. D-conf. Baseline 16-17~ 60 m

  14. PKS 1127-145 • z=0.3127 (HI frequency at ~1082 MHz). • Total time 1 hours (~75% on target) in B-configuration starting at ~2 am MST. • Bandwidth 3.1 MHz with 127 spectral channels.

  15. PKS 1127-145 rms = 10 mJy/bm/ch Hardly any RFI.

  16. RFI: D-configuration PKS 1127-145 B-conf. D-conf.

  17. QSO 0248+430 • z=0.3941 (HI frequency at ~1019 MHz). • Total time 1.5 hours (~75% on target) in C-configuration starting at ~12 noon MST. • Bandwidth 1.56 MHz with 255 spectral channels.

  18. QSO 0248+430 rms = 20 mJy/bm/ch RFI-clean data set.

  19. Summary • Successful L-band observations were carried out with the EVLA at frequencies down to 1019 MHz. • The RFI environment had a marginal or no effect for night-time observations and/or extended configurations. • These results show that the EVLA, with its new L-band capabilities, will become a major player in spectral-line observations down to ~930 MHz (zHI~0.53).

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