Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.naic.edu/alfa/galfa/meetings/3/galfa3_ellen-OH.pdf Дата изменения: Wed Sep 29 01:50:37 2004 Дата индексирования: Sun Dec 23 02:19:01 2007 Кодировка: Поисковые слова: http www.astronomy.ru forum index.php topic 4644.0.html

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


L-wide/ALFA = 2.4 line flux ratio
· 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


SEFD Pol A


SEFD Pol B


Spider scans central pixel


Spider scans pixel 2


Spider scans pixel 5 (best)


OH hexmap with L-wide


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


Compare off pixels 2 and 5


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 2­3 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


Compare off pixels 3 and 6


Compare off pixels 1 and 4