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OH observations with ALFA

OH observations with ALFA. OH hexmap with L-wide Comet 2003 K4 LINEAR July 30. Direct comparison 1667 OH line. Match line flux in 1667 line. Check scaling for 1665 line. 9-level x 1.2 Tsys 25K SEFD 2.2 Jy. 3-level (both lines) Tsys ? >30K SEFD effective 3.7 Jy

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OH observations with ALFA

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  1. OH observations with ALFA

  2. OH hexmap with L-wideComet 2003 K4 LINEAR July 30

  3. Direct comparison 1667 OH line

  4. Match line flux in 1667 line

  5. Check scaling for 1665 line

  6. 9-level x 1.2 Tsys 25K SEFD 2.2 Jy 3-level (both lines) Tsys ? >30K SEFD effective 3.7 Jy Spider scans find SEFD=4.3,5.7 PolB has some problem that can probably be improved L-wide/ALFA = 2.4 line flux ratio

  7. SEFD Pol A

  8. SEFD Pol B

  9. Spider scans central pixel

  10. Spider scans pixel 2

  11. OH hexmap with L-wide

  12. Check pixels 1-6 with L-wide map • SEFD for off pixels is ~1.33 central value (based on measurements at 1400 MHz) • Spacing is 4.1 arcmin in L-wide map, 5 arcmin for ALFA • Assume no contamination from center for now

  13. Compare off pixels 2 and 5

  14. Conclusions • ALFA sensitivity is ~75% that of L-wide at OH in center, ~55% in off pixels • For extended sources, sensitivity and coverage tradeoff is factor of 2–3 net improvement over L-wide (compared to a factor of ~5 at HI) • The simultaneity is a big plus for comets which change on timescales of hours

  15. Compare off pixels 3 and 6

  16. Compare off pixels 1 and 4

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