Upgrade to Pro — share decks privately, control downloads, hide ads and more …

Far-Ultraviolet to Mid-Infrared Dust Extinction...

Far-Ultraviolet to Mid-Infrared Dust Extinction Curves in the Milky Way, LMC, and SMC

Overview of dust extinction curves in these three galaxies, including very recent results from the SMC.

Karl Gordon

April 29, 2024
Tweet

More Decks by Karl Gordon

Other Decks in Science

Transcript

  1. Karl D. Gordon, Astronomer STScI, Baltimore, MD, USA Visiting Prof,

    Ghent University Ghent University 29 Apr 2024 [email protected] karllark@github “Have Dust – Will Study” Slides on speakerdeck Far-Ultraviolet to Mid-Infrared Dust Extinction Curves in the Milky Way, LMC, and SMC
  2. Extinction • Critical clues to dust grain abundance, size, composition,

    and shape • Clues in the continuum and features • Straightforward measurement • Focus on spectroscopic measurements • Biased by my views, not comprehensive
  3. Extinction (not Attenuation) • Extinction – Absorption and scattering out

    of line- of-sight – Specific to a point source dust – Proportional to dust grain properties • Attenuation – scattering into the line-of-sight – Varying extinction to stars – Applies to galaxies, circumstellar dust, etc.
  4. 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.,
  5. 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
  6. Diffuse vs Dense Dust • Diffuse sightlines – Most detailed

    extinction studies – Generally A(V) values less than a few – No 3.0 μm H2 0 ice feature • Dense sightlines – Generally studied in the NIR/MIR only – Have 3.0 μm H2 0 ice feature Decleir et al. (2022, ApJ, 930, 15) H20 Ice
  7. 2175 A Bump width → strong variation center → almost

    no variation Fitzpatrick & Massa (1986, ApJ, 307, 286)
  8. Pre-FUSE ORFEUS: Sasseen et al. 2002, ApJ, 566, 267 Voyager:

    Snow et al. 1990, ApJ, 399, L23 See also: Buss et al. 1994, France et al. 2004; Lewis et al. 2005
  9. FUV (& all UV) extinction smooth Residuals due to stellar

    or ISM HI FUV rise consistent with feature peaking at ~800 Å
  10. FUV rise extinction component & H2 column Very strong correlation

    & goes through zero!!! Grain responsible for FUV rise and H2 co-spatial Not the case for the 2175 Å bump
  11. Pre-Hubble • Continuum measured mainly via photometry (until 2019) •

    Except for Orion dust – Cadelli & Clayton (1988, AJ, 95, 516) • Very Broad Structure with low resolution spectra – Next slide
  12. Very Broad Structure = Deviations from linear w/ 1/lambda Whiteoak

    1966, ApJ, 144, 305 Hayes 1973, IAUS, 53, 83
  13. Broad Optical Features (origin unknown) Long known Very Broad Structure

    Explained! Massa, Fitzpatrick, & Gordon 2020, ApJ, 891, 67 Centers: 4370, 4870, & 6300 Å Widths: ~10% Two blue correlate w/ 2175 Å
  14. NIR/MIR Extinction • Continuum measured via photometry (until 2021) •

    Features measured spectroscopically – Narrow wavelength ranges or towards “complicated” stars – 3.0 μm ice – 3.4 μm hydrocarbon – 10/20 μm silicate features
  15. • Many ice features • 3.0 μm H2 0 the

    strongest • Requires A(V) > 3 Boogert, Gerakines, & Whittet
  16. 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
  17. Variations and 1st Direct Comparison of UV and MIR Strong

    variation Not correlated with grain size Silicates not correlated with 2175 A bump
  18. MW Extinction Summary • Spectroscopic from FUV to MIR –

    FUV smooth & consistent with feature peaking ~800 Å – H2 correlates with FUV rise → co-spatial! – New optical features → unknown origin – NIR powerlaw & may contain H2 0 ice – MIR versus UV features → 2175 Å not due to silicates – R(V) dependent extinction relationship → one relationship for all wavelengths
  19. SMC Extinction Curves Milky Way-like! (2175 Å bump) 4 similar

    curves are found in the star forming bar of the SMC! Ha image of the SMC Gordon & Clayton (1998, ApJ, 500, 816) Gordon et al. (2003, ApJ, 594, 279) STIS Small region Lots of variation! Maiz Apellaniz & Rubio (2012, A&A, 541, 54)
  20. SMC AzV 456 SMC Bar LMC2 LMC General MW Quiescent

    Processed Continuum of Properties Gordon et al. (2003, ApJ, 594, 279) Gordon et al. (2016, ApJ, 826, 104)
  21. Future • HST programs – M31/M33 UV extinction (PI: Clayton)

    • Extinction beyond the MW/LMC/SMC – MW expanded high/low R(V) sample (PI: Decleir) • Dust at the extremes • JWST programs – WISCI (PI: Zeegers) & MEAD (PI: Decleir) • NIR/MIR MW extinction continuum and features – LMC/SMC MIR spectra (PI: Gordon) • 1st measure of 10 um silicate feature
  22. Summary • Extinction measurements are fundamental to understanding dust •

    Spectroscopic Extinction from FUV to MIR in Milky Way – Overall quite smooth – Few broad features including some new ones – One intriguing correlation, comforting non-correlations – One R(V) extinction relationship for all wavelengths • Beyond Milky Way – Larger variation than MW – Intriguing correlations including with gas-to-dust [N(HI)/A(V)] • Future bright w/ HST and JWST
  23. Thanks • Hiring in Fall – postdoc position, PDRs, extinction

    curves, dust, ... • Interested in joint PhD between UGhent and STScI? – Talk to me • Interested in jobs at STScI – Talk to me
  24. Not Covered • Dust scattering (e.g., albedo, scattering phase function)

    • Dust emission • Atomic composition of dust (e.g., depletions) • Dust Polarization • Dust grain models • All important, but not the focus of this talk
  25. Fitting a Line New penultimate technique* • Fully accounts for

    correlated x & y uncertainties • Allows for different correlations for different points • Line integral for each point *The authors await knowledge of what paper to cite where this was first shown (likely from decades ago)
  26. M31/M33 Extinction • All w/ HST photometry • Similar to

    MW • Radial, metallicity variations • 1st measurements in M33 Petia Yanchulov Merica-Jones Clayton, G et al., in prep Yanchulov M-J, P. et al., in prep
  27. Dust Grain Modeling: DGFit • Calculate how new observations affect

    our understanding of dust grains – Bigger/smaller grains, new materials, ... • Quantitatively compare different grain materials – Bayesian statistics may help (Bayes Factors) • Add additional observational constraints – E.g., albedo and scattering phase function asymmetry
  28. MEAD Measuring Extinction and Abundances of Dust • Cycle 1

    JWST program • PI: Marjorie Decleir (+3 Co-Is) • 9 sightlines towards OB stars – A(V) from 1.2 – 2.5 mag – R(V) from 2.5 – 5, f(H2) from 0.1 – 0.65 – Preexisting HST program, PI: M. Decleir • Measure atomic dust abundances via UV spectra of ISM gas absorption lines (depletions) – Existing IUE spectra, optical/NIR photometry • MIRI MRS + NIRCam grism observations – Spectra from 2.5 – 4 µm & 5 – 28 µm • Data status – NIRCam grism: all data taken – MIRI MRS: 6/9 sightlines (just!) taken
  29. WISCI Webb Investigation of Silicates, Carbon, and Ices • Cycle

    1 JWST program • PI: Sascha Zeegers (+20 Co-Is) • 12 sightlines towards OB stars – A(V) from 4.6 – 8.1 mag – Followup HST program, PI: Zeegers • Optical for all, UV for half • MIRI MRS + NIRCam grism observations – Complete spectrum from 2.5 – 28 µm • Data status – NIRCam grism: all data taken – MIRI MRS: 8/12 sightlines taken Sascha Zeegers ESA
  30. JWST 10 µm Silicate Feature WISCI MEAD Models A(V) =

    5 Models A(V) = 1.5 Si-O Si-O Huα Pfα/Huβ Huα Pfα/Huβ
  31. JWST NIR Carbonaceous Features WISCI MEAD Models A(V) = 5

    Models A(V) = 1.5 C-H (aliphatic) C-H (aromatic) C-H (aliphatic) C-H (aromatic) Pfδ Pfε Pfγ Pfδ Pfε Pfγ
  32. JWST MIR Carbonaceous Features I WISCI MEAD Models A(V) =

    5 Models A(V) = 1.5 C=C C=O C=C=C? C-H? C=C C=O C=C=C? C-H? C=C=C C=O: carbonyl C=C: aromatic/olefinic C-H: aromatic/aliphatic Huγ Huγ