AST460: Assignment 5 
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(Oct 12 2012)

1. Here are our observing assignments:

Snez (l=20, 25 deg), Ryan (l=30 deg), Dan (l=35 deg),
Adam (l=40 deg), Pooja (l=45 deg), Felipe (l=50 deg),
Jessie (l=55 deg), Briana (l=60 deg), Tenzin (l=65 deg), 
Nate (l=70 deg), Claire (l=75 deg).

Please modify your script for Galactic HI observations 
to observe your assigned position. Please use the file naming convention as 
described in the Project Introduction document. 

Your observing script will have to do the following:
open an observing file, set central frequency to 1420.405 and use observing mode 4;
go to a selected Galactic position, integrate for 300 sec,
close the observing file. (Please do not stow the SRT at the end so we can save 
some driving time.)

2.
Go through the IDL document ("Quick IDL Tutorial number 1") to become familiar
with IDL's basic functionality.

If you are a less experienced IDL user do problems 2.a and 2.b (but feel free
to challenge yourself with problem 2.c!).
If you already know some IDL, do 2.b and 2.c.


2.a  Generate a sequence of numbers, x.
Write an IDL script (or a procedure) that uses your
array of x-values and a 3-element vector containing the amplitude,
centroid and width, and returns a Gaussian function evaluated at 
each value of x. 
Plot your result.

2.b In the class directory, /usr/users/astro_460/Class_2012,
you will find an idl save file called smc.sav .
Open this file in idl. This is essentially an image of the Small Magellanic Cloud
where each pixel contains the number of hydrogen atoms in that direction (or the HI
column density).

Plot the HI column density profile of the image at row number 200.
Plot the HI column density profile of the image at column number 450.
What is the HI column density value of the image at pixel (320,600)?
What is the maximum HI column density in the image?
What is the sum of all pixels in the image?


2.c Plot the H-R diagram by using the Hipparcos stellar catalog.

Your result should look like the graph shown at:
http://www.ugastro.berkeley.edu/~phiggins/idl_decal/assignment_07.html
but without color. Here are the steps:

(i) Downloading the Catalogue:
-Go to this website: http://webviz.u-strasbg.fr/viz-bin/VizieR
-Type "hipparcos" into the first box and click "find catalogue".
-On the next page, click the first option, "The Hipparcos Main Catalogue".
-Under Preferences, for "Max Entries per Table", select "9999", 
in the next box change from "HTML table" to "|-separated-Values". (| is a pipe.)
-Then scroll down and uncheck all of the "Show" boxes under "Query by Constraints applied on Columns", 
EXCEPT for "Vmag", "Plx", and "B-V".
-Now click "submit query", and save to disk. 
(the file will down load to your computer desktop. move it to where you will be running IDL for 
this problem - your directory.)

(ii) Sort the Data:
-Now open an idl session or xemacs file to begin typing code,
-type "template=ascii_template('asu.tsv')" to open a widget program.
(asu.tsv is the file you saved in the beginning.)
-For "Data starts at line:" type 46. Scroll down in the lower box and keep note of what it says 
in Line 43. This tells us which column is which. Then click next.
-For "Delimeter Between Elements:" click "Other" and type "|", which is a Pipe, not an L or a 1. Then click Next.
-Now, in the first box, change "Field1", "Field2" ... etc to descriptive column names which you made 
note of from Line 24 (something like: RA, DEC, Vmag, Parallax, B-V).
-Now click finish!

(iii) Extract the Data:
-Back in IDL type, "star_struc=read_ascii('asu.tsv',template=template)". 
This gives you a structure called star_struc with each field being the data column 
you named in the last step.
-do a help with a "/str" on the structure to see what the field names are.
-extract each of the fields into separate variables.
-The PLX column gives you a measure of each star's parallax in mili-arcseconds. Convert it to arcseconds.
-use the equation "distance equals 1 over parallax" to get distances for each star in parsecs.
-Now convert the V column, (which is each star's visual magnitude), to Absolute magnitude, 
using the equation, V = v - 5 * log(distance) + 5
-Now plot the Absolute Visual magnitude versus the color (B-V) column. 
This should look something like the figure shown at the above link. You may need to
select the right x- and y-axis range to make your graph look exactly the same.


NOTE for plotting:
To make a hardcopy of your results, in the form of a postscript file, please use procedures called:
 psopen and psclose. You can copy them from /d/leffe/astro_460/Class_2012 to your directory and
use in the following way:

psopen, 'myplot.ps', xsize=5, ysize=4, /inches
{your plotting commands here}
psclose

.ps files can be sent to the floor3 printer.

The assignment is due at the start of next class.