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supernova question?



 
 
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  #1  
Old October 19th 08, 05:45 PM posted to sci.astro
Mike Dworetsky
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Default supernova question?

"WG" wrote in message
...
Is there an online catalogue for supernovas which lists data?
specifically redshift and distances determined by light curves?

If I have this right, the distance determined by light curves [supernova as
standard candles], differs from distance determined by redshift [hubbles
law] by a significant amount.
This difference I believe was the reason why dark energy was postulated and
currently accepted.

Thanks
---------------------------------------------------------------------------------------

These days the data files are often published along with the papers
themselves. Probably on the CDS database. The links would be given with the
ADS listing of the papers, or you could try searching the CDS for catalogues
with supernova data. You might even find the spectra, etc. in FITS format.
You might well find tables of the data you need.

--
Mike Dworetsky

(Remove pants sp*mbl*ck to reply)

  #2  
Old October 19th 08, 05:52 PM posted to sci.astro
Enes
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Posts: 23
Default supernova question?

On 19 Pa¼, 19:17, "WG" wrote:
Is there an online catalogue for supernovas which lists data?
specifically redshift and distances determined by light curves?

If I have this right, the distance determined by light curves [supernova as standard candles], differs from distance determined by redshift [hubbles law] by a significant amount.
This difference I believe was the reason why dark energy was postulated and currently accepted.

Thanks


Dark energy and matter are fabulist"s wishes.
IMHO H. C. Andersen had better real physical base.
  #3  
Old October 19th 08, 06:17 PM posted to sci.astro
WG
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Posts: 19
Default supernova question?

Is there an online catalogue for supernovas which lists data?
specifically redshift and distances determined by light curves?

If I have this right, the distance determined by light curves [supernova as standard candles], differs from distance determined by redshift [hubbles law] by a significant amount.
This difference I believe was the reason why dark energy was postulated and currently accepted.

Thanks
  #4  
Old October 19th 08, 07:27 PM posted to sci.astro
dlzc
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Posts: 1,426
Default supernova question?

Dear WG:

On Oct 19, 10:17*am, "WG" wrote:
Is there an online catalogue for supernovas which lists
data? specifically redshift and distances determined
by light curves?


I'd try the references in these recent papers:
http://arxiv.org/abs/0809.0537
http://arxiv.org/abs/0808.2655
http://arxiv.org/abs/0807.1244
http://arxiv.org/abs/0805.4136
http://arxiv.org/abs/0803.3441

If I have this right, the distance determined by light
curves [supernova as standard candles], differs from
distance determined by redshift [hubbles law] by a
significant amount.


Papers I have read have this as an insignificant amount up to a z of
1.3 or so, after which it becomes very difficult to determine what
object the supernova'd star was actually in.

This difference I believe was the reason why dark
energy was postulated and currently accepted.


Not at all. Standard redshift of "stellar" spectra is all that is
required, and the "Drunkard's Walk" of course.

And Dark Energy is not so much "accepted" as tolerated in light of our
current understanding. It is always being challenged, as is
everything else in Science.

David A. Smith
  #5  
Old October 22nd 08, 10:42 PM posted to sci.astro
Steve Willner
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Posts: 1,172
Default supernova question?

In article ,
"WG" writes:
Is there an online catalogue for supernovas which lists data?


See http://supernova.lbl.gov/Union/

If I have this right, the distance determined by light curves
[supernova as standard candles], differs from distance determined
by redshift [hubbles law] by a significant amount. This difference
I believe was the reason why dark energy was postulated and
currently accepted.


That's a bit confusing, but I think you are on the right track. The
two distances differ _if you don't include dark energy_ in Hubble's
Law. If you do include dark energy, the redshift distance and the
standard candle distance agree just fine, and the amount of dark
energy is consistent with other data (such as microwave background
fluctuations). You might want to take a look at
http://www.astro.ucla.edu/~wright/sne_cosmology.html

--
Steve Willner Phone 617-495-7123
Cambridge, MA 02138 USA
(Please email your reply if you want to be sure I see it; include a
valid Reply-To address to receive an acknowledgement. Commercial
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  #6  
Old October 23rd 08, 02:44 AM posted to sci.astro
John Polasek
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Posts: 95
Default supernova question?

On Wed, 22 Oct 2008 21:42:28 +0000 (UTC),
(Steve Willner) wrote:

In article ,
"WG" writes:
Is there an online catalogue for supernovas which lists data?


See
http://supernova.lbl.gov/Union/

If I have this right, the distance determined by light curves
[supernova as standard candles], differs from distance determined
by redshift [hubbles law] by a significant amount. This difference
I believe was the reason why dark energy was postulated and
currently accepted.


That's a bit confusing, but I think you are on the right track. The
two distances differ _if you don't include dark energy_ in Hubble's
Law. If you do include dark energy, the redshift distance and the
standard candle distance agree just fine, and the amount of dark
energy is consistent with other data (such as microwave background
fluctuations). You might want to take a look at
http://www.astro.ucla.edu/~wright/sne_cosmology.html


Maybe you can clarify the logic. The y-axis is cz which boldly goes to
900000km/s. At z = 1 recession velocity is c. The light would be
invisible. Isn't it a fact that v = cz is limited to very small values
of z?
If I have z =1 then WL is lengthened by 1+z, the frequency by 1/1+z or
f' = f/1+z = f/2.
I fail to see how they continue the abcissa to 900,000 km/s for I
suppose z = 3, and then plot the ordinate as 12 Gpsc.
I would appreciate clarification.
John Polasek
  #7  
Old October 24th 08, 06:15 PM posted to sci.astro
Steve Willner
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Posts: 1,172
Default supernova question?

http://www.astro.ucla.edu/~wright/sne_cosmology.html

In article ,
John Polasek writes:
Maybe you can clarify the logic. The y-axis is cz which boldly goes to
900000km/s.


No logic needed, but the plot units are confusing. The y axis really
is the product of c and z. Yes, that makes no physical sense, but
I'm afraid plotting those units is fairly common. Just mentally
change the units to z and divide the values by 3E5, and all will be
well. As you say, (1+z) is just the ratio of observed to emitted
wavelength, and there's no limit on how large it can be.

I'm going to email Ned and ask him to change the plot.

By the way, the Kowalski et al. paper is well worth reading:
http://arxiv.org/abs/0804.4142

--
Steve Willner Phone 617-495-7123
Cambridge, MA 02138 USA
(Please email your reply if you want to be sure I see it; include a
valid Reply-To address to receive an acknowledgement. Commercial
email may be sent to your ISP.)
 




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