Low-resolution sodium D absorption is a bad proxy for extinction

Dovi Poznanski*, Mohan Ganeshalingam, Jeffrey M. Silverman, Alexei V. Filippenko

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Dust extinction is generally the least tractable systematic uncertainty in astronomy, and particularly in supernova science. Often in the past, studies have used the equivalent width of NaiD absorption measured from low-resolution spectra as proxies for extinction, based on tentative correlations that were drawn from limited data sets. We show here, based on 443 low-resolution spectra of 172 Type Ia supernovae for which we have measured the dust extinction as well as the equivalent width of NaiD, that the two barely correlate. We briefly examine the causes for this large scatter that effectively prevents one from inferring extinction using this method.

Original languageEnglish
Pages (from-to)L81-L84
JournalMonthly Notices of the Royal Astronomical Society: Letters
Issue number1
StatePublished - Jul 2011
Externally publishedYes


  • Dust, extinction
  • Galaxies: ISM
  • Supernovae: general


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