The Optical-Infrared Extinction Curve and its Variation in the Milky Way

New Extinction Curve

We make new measurements of the extinction curve, and have made a new monochromatic extinction curve consistent with these measurements. The curve is normalized to 1 at 5420 Å, and depends on a single parameter, x, which is roughly one-to-one related with R(V). A python implementation of this curve is available here:

• extcurve_s16.py
• cubicspline.py

Example code using this extinction curve:

import extcurve_s16
ec = extcurve_s16.extcurve(0.) # mean extinction curve
lam = numpy.linspace(5000, 45000., 1000.) # angstroms
plot(lam, ec(lam))
xlabel('$\lambda$ (A)')
ylabel('$A(\lambda)/A(5420 A)$')

Varying R(V) can be obtained by calling extcurve() with different arguments. For example,

ec = extcurve_s16.extcurve(0.04)

roughly corresponds to R(V) = 3.6.