Thoughts on Dust (invited intro talk) for the "The Rise of Metals and Dust in Galaxies through Cosmic Time" meeting held Oct, 2020 (https://metals-dust.sciencesconf.org/)
Gordon Astronomer STScI [email protected] @karllark2000 karllark@github “Have Dust – Will Study” Image: Messenger, Scott & Sandford, S. & Brownlee, D.. (2006). The Population of Starting Materials Available for Solar System Construction
we expect for dust? • ALMA & HST • Optical/NIR/MIR ground-based observatories • Archival Observations – IRAS, ISO, Spitzer, Herschel, Akari, Chandra, etc. • What have/will we learn about dust?
strong, 2175 A bump • UV extinction → Local Group – Average varies with metallicity yet full range at single metallicity • UV attenuation → More distant galaxies – Wider range of metallicities – Extinction ↔ Attenuation – What is the full range of observed UV attenuations? – Radiative Transfer needed to interpret
dust Same sightlines also show signatures of processing (high Ca/Na line ratios) Clayton et al. (2000, ApJS,129, 147) Valencic et al. (2003, ApJ, 598, 369) HD 204827 shows SMC Bar dust after foreground subtracted HD 204827 SMC Bar
grains – Hard to measure outside the Local Group (except GRBs?) (with existing facilities) • Attenuation → dust grains + geometry – Geometry = star/dust & ISM structure – Can be measured at many redshifts – Need dust different than Local Group?
sources • Total emission → mass of dust – High redshift/low metallicity → clues to dust formation • Aromatic/PAH features – Probes of carbonaceous dust – Galaxies with different environments (SF, metallicity)
Features? 2175 A, silicates, aromatic/PAH, DIBs, etc. (observationally challenging?) • How important is cycling between diffuse/dense clouds to get observed ISM dust properties? • Is the growth in the ISM → clouds balanced by destruction ← clouds? – Is something left on the grain? (observational signatures?) • Depletions, Gas/Dust Ratio → observational signatures