How can I recognize H alpha line?

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SUMMARY

The discussion centers on identifying the H alpha line in a redshifted galaxy spectrum. It is established that while individual line identification is uncertain due to redshift, the presence of multiple spectral lines allows for confident redshift determination. The pattern of these lines remains consistent, enabling accurate identification. Reference to visual aids, such as figures from Wikipedia, is suggested for better understanding of absorption lines.

PREREQUISITES
  • Understanding of galaxy spectra and redshift concepts
  • Familiarity with Balmer series and H alpha line characteristics
  • Knowledge of spectral line patterns and their significance in astrophysics
  • Ability to interpret graphical data from astrophysical resources
NEXT STEPS
  • Research the Balmer series and its role in spectral analysis
  • Learn about redshift calculations and their implications in astronomy
  • Study the methods for identifying multiple spectral lines in astrophysical data
  • Explore resources on interpreting absorption line spectra
USEFUL FOR

Astronomers, astrophysics students, and researchers analyzing galaxy spectra and redshift phenomena will benefit from this discussion.

19matthew89
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Hi everyone!
If I measure a galaxy spectrum in order to compute galaxy redshift, and I know that Balmer's H alpha line is evident in the spectrum, how can I recognize it? In other words, how can I be sure that the peaked line I clearly see on the spectrum is really H alpha line and not another line that I don't know?
I cannot obiously use the wavelength because it'll be shifted...can I use line intensity instead? But the intensity could be attenuated...and so...could I use H alpha shape to recognize it?
I'd be grateful towards you if you could help me.

Thank you
 
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You really can't be sure you have identified a single line in a redshifted spectrum. But if you have several lines, then you can determine the redshift with high confidence. This is because all of the lines are redshifted by the same factor, so the pattern of the lines is unambiguous. Look at the second figure down on the left (with the caption that begins "Absorption lines in the...") on this page:

http://en.wikipedia.org/wiki/Redshift
 

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