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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. Dust Extinction
    Karl D. Gordon
    Astronomer
    STScI, Baltimore, MD
    Milky Way Mapper Dust Telecon
    27 Feb 2023
    [email protected]
    @[email protected]
    karllark@github

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  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

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  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

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  4. Witt, Bohlin, & Stecher 1984, 279, 698

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  5. 2175 A Bump
    width → strong variation
    center → almost no variation
    Fitzpatrick & Massa (1986, ApJ, 307, 286)

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  6. Fitzpatrick & Massa 1988, ApJ, 328, 734

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  7. Ultraviolet decomposed

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  8. Cardelli, Clayton, & Mathis 1988, ApJ, 329L, 33; 1989, ApJ, 345, 245

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  9. Valencic, Clayton, & Gordon 2004, ApJ, 616, 912

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  10. 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

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  11. Marjorie Decleir

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  12. 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

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  13. Variations and 1st Direct Comparison of UV and MIR
    Strong variation
    Not correlated
    with grain size
    Silicates not correlated
    with 2175 A bump

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  14. Measuring A(V)
    w/ E(B-V) get R(V) = A(V)/E(B-V)
    Scatter ~ 7% Scatter ~ 3%
    I3 = 5.6 μm

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  15. In preparation
    Based on spectroscopy
    at all wavelengths

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  16. Average
    Variation with
    R(V)/grain size

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  17. Intriguing deviations

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  18. Coagulation?

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  19. Pair Method
    Github: karllark/measure_extinction
    OB stars ideal targets
    Luminous at all wavelengths
    Fairly simple atmospheres

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  20. 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.,

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  21. Slide from Dries Van De Puttte

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  22. MRN Bare Grains Model
    Mathis, Rumpl, & Nordsieck (1977, ApJ, 217, 425)

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  23. Updated Bare Grain Model
    Weingartner & Draine (2003)

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  24. Coated Grains
    Model
    Jones et al. (2013)

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