Extinction Curves

The files for the extinction curves can be found at Extinction Curves.

An overview of the available extinction curves is given in the table below.

The following table should aid users in selecting the most appropriate extinction relation.

File Model Extinction Exposure Time1 (seconds) Wavelength Range (Angstroms)
milkyway_diffuse Milky Way Diffuse Rv=3.1 308 1000-22222
milkyway_dense Milky Way Dense Rv=5.0 84 1000-22222
milkyway_rv21 Milky Way CCM Rv=2.1 612 912-50000
milkyway_rv4 Milky Way CCM Rv=4.0 166 912-50000
lmc_diffuse LMC Average Rv=3.41 464 998-21978
lmc_30dorshell LMC2 Supershell Rv=2.76 493 998-21978
smc_bar SMC Bar Rv=2.74 3808 998-21978
xgal_starburst Starburst   92 912-21997


1 The exposure time was calculated using the HST ETC assuming a S /N=10 observation with a Kurucz O5 with V=15 and E(B-V)=0.4, in COS/FUV G130M/1309A through the Primary Science Aperture (PSA).

Interstellar Extinction Curves

The Milky Way extinction curves are taken from Cardelli, Clayton, & Mathis 1989. In addition to curves appropriate for the diffuse and dense ISM cases, two additional curves have been added to provide more choices for Rv:

  • Milky Way Diffuse: An average Galactic extinction curve for diffuse ISM (Rv=3.1)
  • Milky Way Dense: A Galactic extinction curve for dense/molecular ISM (Rv=5.0)
  • Milky Way CCM1: Rv=2.1
  • Milky Way CCM2: Rv=4.0

The Large and Small Magellanic Cloud extinction curves are taken from Gordon et al 2003:

  • LMC Average: Large Magellanic Cloud extinction (Rv=3.41) away from 30Dor
  • LMC Supershell: Large Magellanic Cloud extinction for the Supershell/in the 30Dor region but it does not apply to the 30 Dor Nebula (Rv=2.76)
  • SMC Bar: Small Magellanic Cloud extinction (Rv=2.74)

A general extra-galactic extinction curve is taken from Calzetti et al 2000:

  • Starburst (attenuation law): Appropriate for stellar continuum
References
  • Cardelli, Clayton & Mathis (ApJ, 345, 245, 1989)
  • Gordon et al. (2003, ApJ, 594, 279)
  • Calzetti et al. (2000. ApJ, 533, 682)

Please Contact the HST Help Desk with any Questions

https://hsthelp.stsci.edu.