Dust Extinction and SDSSV Milky Way Mapper

Discussion slides for SDSSV Milky Way Mapper telecon.

Transcript

1. Dust Extinction Karl D. Gordon Astronomer STScI, Baltimore, MD Milky Way Mapper Dust Telecon 27 Feb 2023 kgordon@stsci.edu @karllark@astrodon.social karllark@github
2. Some Thoughts • Detailed knowledge of extinction – Biased to low A(V) – Biased to withing 1 kpc of Sun + LMC/SMC • 3D mapping of A(V) & R(V) – Probe specific physical environments – Hints from MW and LMC/SMC – R(V) dependent average relationship not the full story – Significant variations in UV and NIR/MIR
3. Wavelength axis variations Allow full FUV-MIR extinction to be seen Wavelength scale is proportional to energy Emphasizes UV wavelengths Versus λ Versus 1/λ UV Opt NIR MIR
4. Witt, Bohlin, & Stecher 1984, 279, 698
5. 2175 A Bump width → strong variation center → almost no variation Fitzpatrick & Massa (1986, ApJ, 307, 286)
6. Fitzpatrick & Massa 1988, ApJ, 328, 734
7. Ultraviolet decomposed
8. Cardelli, Clayton, & Mathis 1988, ApJ, 329L, 33; 1989, ApJ, 345, 245
9. Valencic, Clayton, & Gordon 2004, ApJ, 616, 912
11. Broad Optical Features (origin unknown) Long known Very Broad Structure Explained! Massa, Fitzpatrick, Gordon, et al. 2020, ApJ, 891, 67 Centers: 4370, 4870, & 6300 Å Widths: ~10% Two blue correlate w/ 2175 Å
12. Marjorie Decleir
13. 3.0 μm ice feature measured in the diffuse average at A(ice)/A(V) = 0.0019 +/- 0.007 Not a significant detection, but intriguing at the level predicted by Potapov et al. (2021) if ice is present in shadowed pits in silicate grains
16. Variations and 1st Direct Comparison of UV and MIR Strong variation Not correlated with grain size Silicates not correlated with 2175 A bump
17. Measuring A(V) w/ E(B-V) get R(V) = A(V)/E(B-V) Scatter ~ 7% Scatter ~ 3% I3 = 5.6 μm
18. In preparation Based on spectroscopy at all wavelengths
19. Average Variation with R(V)/grain size
20. Intriguing deviations
21. Coagulation?
22. Processing?
23. Thanks
24. Pair Method Github: karllark/measure_extinction OB stars ideal targets Luminous at all wavelengths Fairly simple atmospheres
25. Basic measurement is the color “excess” versus wavelength (in magnitudes as we are astronomers) Normalize so measurements with different dust columns can be compared A(V) determined by extrapolating to infinite wavelength e.g.,
26. Slide from Dries Van De Puttte
27. MRN Bare Grains Model Mathis, Rumpl, & Nordsieck (1977, ApJ, 217, 425)
28. Updated Bare Grain Model Weingartner & Draine (2003)
29. Coated Grains Model Jones et al. (2013)