NGC 2820


Science case: looking for vertically extended ionized gas filaments in this edge on spiral. This work forms part of Scott Miller's PhD thesis work (Maryland) with Sylvain Veilleux. See the summary article by Miller & Veilleux in the Feb 1999 AAO Newsletter article which shows several other edge-on spirals. The observations have been carried out with the TTF at the WHT  and the AAT.
Below, we show raw WHT data for one such object, NGC 2820.


Observers: JBH, KGB, RA Date: 12-MAR-1997

WHT 4.2m f/4 0.29"/pix binned 2x2 0.75" seeing, dark sky, some cirrus around

TTF tuned to 6597.4A (H-alpha @ 1581 km/s) 11um gap, or 8A bandpass measured, finesse = 25

6590/130 blocking filter. Accurate calibration off three lines with CuNe arc.

Plate parallelism checked with CuAr + 4 quadrants to better than 1A.

Exposure times = 1800 sec each Read noise 3.0e-, gain 1.0

TTF efficiency close to 20%

3 images:

(i) 460 through filter alone

(ii) 461 at H-alpha redshifted. (Not correctly specified. Put it right on an OH line.)

(iii) 462 off band (6576, right on top of OH line)

Subtracting the last two removes the f/4 camera ghost in the field. This flatfields out in any case. But since flatfield is pretty much the same at both, difference o.k.