In the AAOmega run of March 2006, we took some standard stars. They were reduced with drcontrol by changing the type from MFFLX to MFOBJECT. In a discussion with Rob Sharp (AAO) he mentioned that it was a good idea to test the Gaussianity of the standard stars throughout the frames. The reason is that the software uses a constant value for the FWHM of the Gaussian throughout the spectral image. This could have major impact on the relative flux calibration. (Absolute flux calibration with a fibre instrument is quite near to impossible.) The results are in the two figures.




The blue camera is quite constant at a FWHM = 3.05 pix and doesn't vary more than 1% between observations. The red arm, on the other hand, varies a lot more! It varies between a FWHM of 3.5 pix (towards the blue end) down to 3.1 pix and ~2% between observations. The measurements were done with some scripts I wrote in IDL. The FWHM and central pixel of the Gaussian are derived from the sum of 51 columns around the indicated points.

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Consider the following code in IDL:

IDL> a = dblarr(4,4)
IDL> b=[4]
IDL> a[1,4]++
% Attempt to subscript A with <INT ( 4)> is out of range.
% Execution halted at: $MAIN$
IDL> a[1,b]++
IDL> print, a
0.0000000 0.0000000 0.0000000 0.0000000
0.0000000 0.0000000 0.0000000 0.0000000
0.0000000 0.0000000 0.0000000 0.0000000
0.0000000 1.0000000 0.0000000 0.0000000
IDL> b=[6]
IDL> a[1,b]++
IDL> print, a
0.0000000 0.0000000 0.0000000 0.0000000
0.0000000 0.0000000 0.0000000 0.0000000
0.0000000 0.0000000 0.0000000 0.0000000
0.0000000 2.0000000 0.0000000 0.0000000

This is quite annoying. I thought it was a bug (or feature) from IDL, but it seems that I didn't read the manual good enough. With the option compile_opt STRICTARRSUBS this behaviour is not allowed anymore...

Mari Minari from Support at Ittvis (formerly RSI) helped me out on this. Thanks!!

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As part of my thesis I am looking for line emitting objects. During follow up observations of low redshift (z ~ 0.24 - 1.2) emission line galaxies at the AAT with AAOmega, we also included the confirmed Lyman alpha emitter J114334.98-014433.7 (aka S11_5236 aka S11_13368; Westra et al. 2005). Below is the spectrum of this object. The exposure time is ~4 hours. The line can be clearly seen.



The spectrum was first presented at the ASA 2006.

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Just found out how to do a LEFT JOIN on combined tables with UNION. It's a bit tricky, but the point is that the result of a UNION is another table... See below:

SELECT `ID`, "whatever columns" FROM (
SELECT "whatever" FROM t1
UNION DISTINCT
SELECT "whatever" FROM t2
) AS newName1
LEFT JOIN
(
SELECT `ID` FROM t3
UNION DISTINCT
SELECT `ID` FROM t4
) AS newName2
ON `newName1`.`ID` = `newName2`.`ID` WHERE `newName2`.`ID` IS NOT NULL

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Hi all,

This is my attempt to blog whatever I'm doing. Most likely it will contain nothing useful and maybe at some point everything will be just canned, but I thought it might be a good idea to start something, so I can just spit my struggles with computing somewhere ;)

Eduard

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