An empirical relation between sodium absorption and dust extinction

Dovi Poznanski*, J. Xavier Prochaska, Joshua S. Bloom

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Dust extinction and reddening are ubiquitous in astronomical observations and are often a major source of systematic uncertainty. We present here a study of the correlation between extinction in the Milky Way and the equivalent width of the NaiD absorption doublet. Our sample includes more than 100 high-resolution spectra from the Keck telescopes and nearly a million low-resolution spectra from the Sloan Digital Sky Survey (SDSS). We measure the correlation to unprecedented precision, constrain its shape and derive an empirical relation between these quantities with a dispersion of the order of 0.15 mag in E(B - V). From the shape of the curve of growth we further show that a typical sight line through the Galaxy, as seen within the SDSS footprint, crosses about three dust clouds. We provide a brief guide on how to best estimate extinction to extragalactic sources such as supernovae, using the NaiD absorption feature, under a variety of circumstances.

Original languageEnglish
Pages (from-to)1465-1474
Number of pages10
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
StatePublished - 21 Oct 2012


  • Dust, extinction
  • ISM: atoms


Dive into the research topics of 'An empirical relation between sodium absorption and dust extinction'. Together they form a unique fingerprint.

Cite this