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SNe Ia data - photon flux or energy flux?



 
 
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  #1  
Old October 20th 06, 05:43 PM posted to sci.astro.research
Bob Day
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Posts: 8
Default SNe Ia data - photon flux or energy flux?

Is modern distance modulus vs redshift data from type Ia supernovae
based on photon flux, so that the expansion of space would cause a
1/(z+1) decrease in the flux, or is it based on energy flux, in which case
the expansion of space would cause a 1/((z+1)^2) diminution?

-- Bob Day
  #2  
Old October 21st 06, 01:22 PM posted to sci.astro.research
Stupendous_Man
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Posts: 57
Default SNe Ia data - photon flux or energy flux?

Bob Day wrote:
Is modern distance modulus vs redshift data from type Ia supernovae
based on photon flux, so that the expansion of space would cause a
1/(z+1) decrease in the flux, or is it based on energy flux, in which case
the expansion of space would cause a 1/((z+1)^2) diminution?


Most measurements these days in the optical
and near-IR are made with detectors which count
photons, not energy.

What people do with the measurements afterwards
is very hard to follow properly.

Michael Richmond
  #3  
Old October 22nd 06, 09:28 AM posted to sci.astro.research
Phillip Helbig---remove CLOTHES to reply
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Posts: 198
Default SNe Ia data - photon flux or energy flux?

In article , "Bob Day"
writes:

Is modern distance modulus vs redshift data from type Ia supernovae
based on photon flux, so that the expansion of space would cause a
1/(z+1) decrease in the flux, or is it based on energy flux, in which case
the expansion of space would cause a 1/((z+1)^2) diminution?


Energy.
  #4  
Old October 22nd 06, 09:29 AM posted to sci.astro.research
Phillip Helbig---remove CLOTHES to reply
external usenet poster
 
Posts: 198
Default SNe Ia data - photon flux or energy flux?

In article ,
"Stupendous_Man" writes:

Bob Day wrote:
Is modern distance modulus vs redshift data from type Ia supernovae
based on photon flux, so that the expansion of space would cause a
1/(z+1) decrease in the flux, or is it based on energy flux, in which case
the expansion of space would cause a 1/((z+1)^2) diminution?


Most measurements these days in the optical
and near-IR are made with detectors which count
photons, not energy.


Yes. But the raw measurements are converted.

What people do with the measurements afterwards
is very hard to follow properly.


You need K-corrections etc. Standard stuff. The 1/((z+1)^2) factor is
for a K-correction of 0.
 




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