AST460: Assignment 6 
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(Oct 20 2014)

Process your observations following these instructions 
(please ignore Section 5 in the "Project Intro" document):

- Using class notes, read your specific data file in IDL and place data in a 2-dimensional 
array representing a stack of spectra (each row of the array will be a single
HI spectrum).

- Identify your cal_on, cal_off, and the HI spectra to be used for integration.

- Using the information provided in your data file, build a frequency array 
for your observations. Plot cal_on vs frequency, and overplot on this plot cal_off vs frequency.
Note that the y-axis shows data values in arbitrary telescope units.

- Using cal_on and cal_off scans calculate the spectral shape or gain function 
(use the equation provided in class notes but smooth or boxcar average this spectrum using a 5-bin window).
Plot this spectral shape function vs frequency. Note that the noise diode has a temperature of 356 K.
Over most of the frequency range shape function should have a value close to 1.
Please note if this is not the case.

- Average all HI spectra after cal_on and cal_off to produce a single HI spectrum. 
Your y-axis now shows Antenna Temperature in units of Kelvin as the noise calibration 
(noisecal) applied automatically the conversion from arbitrary telescope units to K. 
Plot this spectrum as a function of frequency. 

- Use the Doppler equation to convert from Frequency to the Topocentric Radial Velocity. 
To convert from Topocentric to LSR Velocity you will need to ADD a correction factor
to your velocity array. 

The correction factor is:
for (l, b) = (38, 0) -8.88, file observed on oct 17 2014
for (l, b) = (41, 0) -8.10, file observed on oct 17 2014
for (l, b) = (44, 0) -7.28, file observed on oct 17 2014
for (l, b) = (47, 0) -6.45, file observed on oct 17 2014
for (l, b) = (50, 0) -5.60, file observed on oct 17 2014
for (l, b) = (53, 0) -4.74, file observed on oct 17 2014
for (l, b) = (65, 0) -0.74, file observed on oct 13
for (l, b) = (68, 0)  0.22, file observed on oct 13
for (l, b) = (71, 0)  1.18, file observed on oct 13
for (l, b) = (56, 0) -3.61, file observed on oct 13
for (l, b) = (59, 0) -2.66, file observed on oct 13
for (l, b) = (62, 0) -1.71, file observed on oct 13
for (l, b) = (29, 0) -10.77, file observed on oct 20
for (l, b) = (32, 0) -10.11, on oct 20
for (l, b) = (35, 0) -9.42, on oct 20
for (l, b) = (20, 0) -12.58, on oct 20
for (l, b) = (23, 0) -12.01, on oct 20
for (l, b) = (26, 0) -11.41, on oct 20

If your observations were obtained on a different day, please contact me and I 
will calculate your correction factor.


- Produce the HI spectrum corrected for the spectral gain and plot this spectrum as a function of the LSR velocity.

-  As you can see from class notes, this shape-corrected HI spectrum should be flat at velocities
without significant HI signal, but it is still sitting on a pedestal provided by 
the system temperature. To remove this constant effect, find a signal-free range of velocities 
and estimate the mean value of spectral data points. 
Remove this constant value from your shape-corrected HI spectrum to produce the final HI spectrum.
Plot this resultant spectrum as a function of the LSR velocity. 


Focus on one data file first to make sure all steps are working well.
But write your processing script/procedure by having in mind that you will
have two more data files. Now process the additional two data files to 
obtain final HI spectra at all three positions.

The assignment is due at the next class meeting.