General HLA questions, problem reports and suggestions

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hubble.leg...@gmail.com

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Sep 23, 2008, 10:49:08 AM9/23/08
to HLA Forum
This is a forum for users to post and discuss general HLA questions,
problem reports and suggestions.

skyguy

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Sep 29, 2008, 5:06:55 PM9/29/08
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The HLA is amazing!...and this forum is a great Idea.

I have a couple of suggestions.

First, I would really appreciate a much more extensive tutorial than
those available at the HLA site. In particular, I've had trouble
understanding how to use the spectral analysis features. For example,
I'm not clear on how to select spectral targets/regions.

I understand the principals of spectral analysis but I've never done
any. A link to a tabulation of line wavelengths would be a big help.

You ought to provide a link to this forum on the HLA site.

Thanks for a wonderful opportunity.

Bill McDonald

Brad Whitmore

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Sep 30, 2008, 10:44:26 AM9/30/08
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Hi Bill - Here is an example and a few comments that might help get
you started.
Note that at present the plotting tool is mainly for quick look rather
than
detailed work. For example, we do not have a way to measure accurate
line wavelengths or line widths yet. We should have this for the next
release in about 6 months.

Brad Whitmore (HLA Project Scientist)

On Sep 29, 5:06 pm, skyguy <skyhig...@cableone.net> wrote:
> The HLA is amazing!...and this forum is a great Idea.
>
> I have a couple of suggestions.
>
> First, I would really appreciate a much more extensive tutorial than
> those available at the HLA site.  In particular, I've had trouble
> understanding how to use the spectral analysis features. For example,
> I'm not clear on how to select spectral targets/regions.
>

Here is an example that might be of interest.
Enter "antennae" in the search box and just get the STIS data.
Go to image O5HE06010 and look at it with the interactive
display. Move your cursor to a y value of 765 (e.g., .
to show a spectrum of the of the region around X=295, Y=795
which happens to be the H alpha line of Hydrogen) and hit "L".
You should get a line plot. You can fool around with coadding lines
(I use 3), changing the x and y min and max values etc.
Note that the real lines are around 6580 Angstroms (N), 6595 A
(H_alpha),
6615 A (N), and 6750 and 6765 A (S). Most of the other "lines"
are due to cosmic rays (this is the kind of thing that gets
fixed in detailed reductions).

One thing you can do is get an approximate wavelength.
Blow up the x axis so you just get the H_alpha line (i.e.,
from say 6560 to 6610 for min and max X values ). The line
center looks like about 6596 A. This line should be
at 6563 A if the object were at rest. Hence it is
redshifted 33 A. The formula to convert to velocity
is delta_wavelength/wavelength = delta velocity/300,000 (speed of
light).
Hence 33/6563 = delta_velocity/300,000 or
delta_velocity = 33/6563 * 300,000 = 1508 .
Hence this region is moving away from us at ~ 1500 km/sec.

Now look at my article at

http://adsabs.harvard.edu/abs/2005AJ....130.2104W
Hit "Full Refereed Journal article (PDF/Postscript)

Relevant Figures are 1, 2b, 3, 4b, 5b, 6b.

We find this images is from visit 6, the object we measured is
number 3 in region D, the velocity (CZ) in figure 6b) is about 1500
kms,
hence our rough measurement from above was right.

Also note from fig. 3 that the spectrum down around X= 295, Y = 218 is
region B
which shows a steep-gradient feature discussed in the paper. You can
see this best by enlarging the region and using the darker button
a few times to improve the contrast.

Hope that gives you a little traction on getting started playing with
spectra.


> I understand the principals of spectral analysis but I've never done
> any. A link to a tabulation of line wavelengths would be a big help.
>

Hopefully someone else has a reference to look at line lists?
I googled around a bit and did not run into anything obvious.
I just use a book called "Astrophysical Quanties" by Allen.
If we find something good we can add a link to a FAQ (which
we will probably convert this example into).

> You ought to provide a link to this forum on the HLA site.
>

We actually added a link to this forum at the bottom
of the HLA page last friday :-) .

hubble.leg...@gmail.com

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Sep 30, 2008, 11:16:24 AM9/30/08
to HLA Forum
For information on line wavelengths and oscillator strengths, try the
following links:

General link to atomic data and line lists:
http://physics.nist.gov/PhysRefData/Handbook/index.html
http://fuse.pha.jhu.edu/support/atomdata/atom.html

A more technical list of line information can be found at:
http://www.hia-iha.nrc-cnrc.gc.ca/staff/morton_e.html

And the papers by Morton can be found at:
http://adsabs.harvard.edu/cgi-bin/nph-ref_query?bibcode=2000ApJS..130..403M&amp;refs=ASSOCIATED&amp;db_key=AST
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