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

E. F. Schlafly, A. M. Meisner, A. M. Stutz, J. Kainulainen, J. E. G. Peek, K. Tchernyshyov, H.-W. Rix, D. P. Finkbeiner, et al.

### 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:

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.

Edward Schlafly, ‮ed.aipm ta ylfalhcs