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Dust Extinction and SDSSV Milky Way Mapper

Karl Gordon
February 27, 2023

Dust Extinction and SDSSV Milky Way Mapper

Discussion slides for SDSSV Milky Way Mapper telecon.

Karl Gordon

February 27, 2023

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  1. 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
  2. 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
  3. 2175 A Bump width → strong variation center → almost

    no variation Fitzpatrick & Massa (1986, ApJ, 307, 286)
  4. 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
  5. 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
  6. Variations and 1st Direct Comparison of UV and MIR Strong

    variation Not correlated with grain size Silicates not correlated with 2175 A bump
  7. 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.,