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
and shape • Clues in the continuum and features • Straightforward measurement • Focus on spectroscopic measurements • Biased by my views, not comprehensive
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.
as we are astronomers) Normalize so measurements with different dust columns can be compared A(V) determined by extrapolating to infinite wavelength e.g.,
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
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
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
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)
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
• Dust emission • Atomic composition of dust (e.g., depletions) • Dust Polarization • Dust grain models • All important, but not the focus of this talk
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)
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
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