Dusty Thoughts Metals/Dust Meeting #MetalsDust2020 26 Oct 2020 Karl D. 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 

“The objective of this talk (R0.1) will be to try asking the main questions about metals and dust that you would like to be addressed during this conference (given the general program, of course).” 

Dust 

Dust “Have Dust – Will Study” 

Cautions ● Biased by my knowledge/experience ● Focused on Dust ● Dated? (no longer can even scan astrop-ph) ● Comments/suggestions/etc always welcome ● Questions, slack, email, twitter, ... 

Questions ● What is dust? ● What are the dust properties at different z? – Metallicity, redshift, distance in/from a galaxy, ... ● What is the origin of dust? – Young stars, evolved stars, ISM, … 

Connections ● Local ↔ Distant – Local↔ Distant Universe – Often proposed, rarely done ● Observations ↔ Theory – UV, IR, submm, optical, X-ray, ... – Grain models, Radiative Transfer 

Observations ● James Webb Space Telescope (JWST) – What can 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? 

Dust versus Metallicity (UV) ● Ultraviolet → effects of 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 

Also Fitzpatrick (1999) Valencic et al. (2004), Gordon et al. (2009), Fitzpatrick et al. (2019) 

SMC AzV 456 SMC Bar LMC2 LMC General MW Quiescent? Processed? Large Range of Extinction Curves UV Slope Gordon et al. (2003, ApJ, 594, 279) 

MW has “LMC/SMC” like sightlines Low density sightlines show MC 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 

Extinction ↔ Attenuation ● Extinction → direct measure of dust 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? 

Radiative Transfer ● Global and Local geometry matters – Global: spherical, disk, arms, … – Local: small scale clumpiness ● The physics of dust RT restricts the allowed attenuation curves ● Need – Grids: explore parameter space (too simple?) – Individual galaxies: detailed studies (too complex?) 

Global Geometries Local + Global Geometries Witt, Thronsen, & Capuano (1992, ApJ, 393, 611) Witt & Gordon (2000, ApJ, 528, 799) Seon & Draine (2016, ApJ, 833, 201) 

Witt & Gordon (2000, ApJ, 528, 799) For an alternative explanation with MW dust solution for starbursts, see: Panuzzo et al. (2007, MNRAS, 375, 640) SMC-like dust in Starbursts 

Detailed Modeling of M51 De Looze et al. (2014, A&A, 571, 69) Dust Heating 63% from young stars (< 100 Myr) 37% from old stars (~10 Gyr) 

Dust versus Metallicity (IR) ● Emission probes dust and illuminating 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) 

Dust Masses Aniano et al. (2020, ApJ, 889, 150) Data: Herschel+Spitzer Lines: Simple Model with dust formation/destruction time scales 

Total Dust Mass “Scare” Plot Deriving dust mass from IR Emission non-trival Variations with metallicity? Calibration with depletions? Clark et al. (2019, MNRAS, 489, 5256) 

MIR Spectra Starbursts: Engelbracht et al. (2008, ApJ, 678, 804) M101 HII regions: Gordon et al. (2008, ApJ, 682, 336) Galaxies: Smith et al. (2007, ApJ, 656, 770) 

Stacked Z = 1 LIRGs Stacked Z = 2 ULIRGs Fadda et al. (2010, ApJ, 719, 425) 

Relative PAH masses Draine et al. (2007, ApJ, 663, 866) 

Origin of Dust ● Formation: AGB stars, Supernovae, ISM – Do we need all 3? ● Processing – Growth in ISM – Destruction in supernovae shocks ● What are the keys to the dust properties? (testable?) 

Formation ● Stars: AGB/SN/other sources? – Definitely grains condense from the gas phase (SN may destroy all the grains they form?) ● ISM – Atoms move from the gas ↔ solid phase ● Depletions, ice formation 

Magellanic Clouds Excellent census AGB: most dust from a few extreme stars (enough)? Transport? Uncertainties? Srinivasan et al. (2016, MNRAS, 457, 2814) Carbon Oxygen Total 

Magellanic Clouds SN1987A: ~0.8 M_solar Single source Matsuura et al. (2015, ApJ, 800, 50) Indebetouw et al. (2014, ApJL, 78, L2) 

Processing ● What are the grain properties in AGB/SN? – 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 

Milky Way Depletions Jenkins (2009, ApJ, 700, 1299) 

Magellanic Cloud Depletions Roman-Duval et al. (2019, ApJ, 871, 151) Also: Jenkins & Wallerstein (2017, ApJ, 838, 85) LMC: similar to MW? SMC: less depleted See talk by Roman-Duval 

Gas/Dust Ratio Roman-Duval et al. (2017, ApJ, 841, 72) 

Questions ● What is dust? ● What are the dust properties at different z? – Metallicity, redshift, distance in/from a galaxy, ... ● What is the origin of dust? – Young stars, evolved stars, ISM, … 

Thanks 

Simple Attenuation Example 

Global and Local Geometries with Dust Emission Law, Gordon, & Misselt (2018, ApJS, 236, 32) Law, Gordon, & Misselt (2020, in prep)