aas notes day 3

CH4 Production via Refractory Carbon Destruction in Disks: Predictions for JWST
-JWST will look at lots of disks
-what are the carbon carriers in inner proplyds?
-how does this effect crbon delivery to planets
-carbon in proplyds: 1/2 refractory minerals, 1/2 volatiles (mainly CO)
-methane is notably missing from list of inner propyld, only detected in ONE proplyd to date.
-methane could be a result of destruction of refractory carbon inherited from the ISM.
-run simulations of t-tauri disk
-model variations: turn on/off refrac C destruction. alter initial abundance of water, alter initial major carbon carriers.
-model suggests warm surface: mostly CO, some CO2, H2O, OH, C2H2, and little CH4.
-change water in the disk (imagine radial drift bringing in ices from the snowline, OR deprive ice by locking it in the midplane or beyond snowline) removing water enhances difference between models and obs.
-Enhanced C/O ratios may be indicator of refravtory carbon destruction, they could also be the result of alt processes or initial comp.
-C/O ratio significance required for understanding distribution of carbon in proplyds.
-outer regions must be understood to understand inner regions.

The impact of dust growth on the observed sub-structures in protoplanetary disks
-I am sorry to say I am struggling to understand the presenters' accent, especially with the low audio quality.
-proplyds: ringed structures, asymmetry, and clumpy, all different structures.
-planet formation: evilution of solids: ISM dust-sand-pebble-planetesimal-planet
-dust trap by gaseous vortex. pressure bump at edge of a planet gap can trap dust. steep density gradient, lead to asymmetric vortex.
-vortex lifetime: 5000 orbits.
-HOWEVER: dust coagulation changes things: dust size is nonuniform in vortex region. dust size growth facilitates increase of dust/gas ratio
-vortex lfietime can be significantly impacted by dust feedback with coagulation, destoryed early.
-rings produced instead of vortex.
-if planet doesn't open gap quick enough an inner ring is impeded due to dust coagulation and subsequent radial drift.
-eccentric super-earth: can leave a signature on the dust, even after it circularizes it leaves a gap.

Gregory Brannon11:20:17 AM
I have a question for anyone who studies disks: what generally is the density of a disk? pressure of gas? Comparable to terrestrial pressures or more like close-to-vacuum?
Ilse Cleeves11:21:54 AM
It can be a substantial range but much lower than terrestrial. Maybe as high as 1e14 H2 per cm^3 close to the star and 1e7 H2 per cm^3 at the midplane at ~100 au though there is a lot of debate on how we measure it
Gregory Brannon11:24:14 AM
I'm not a scientist (I'm here with my community college astronomy club) so I have a tough time thinking of pressures in terms of H2/cm^3. do you have an estimate of pressure for those values?
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Ilse Cleeves11:27:07 AM
I think about 1e-6 bar in the innermost high density regions and .... much much less in the outer disk. both temperatures and densities are changing (decreasing) with distance
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Ilse Cleeves11:27:18 AM
also welcome to your astronomy club!
Dana Anderson11:32:51 AM
Also for comparison, the atmosphere at Earth’s surface has a pressure of 10^19 molecules per cm^3

Ward Howard4:59:57 AM
How might PPD inhomogeneities help with particle accretion from sub-mm to m sized objects, if at all? Could they help overcome loss due to collisions at higher impact energies and ultimately promote growth of planetesimals?
Ilse Cleeves11:24:12 AM
Li should jump in here, but over densities should help promote growth by just having the increased self-gravity. What scale inhomogeneity are you thinking?
Yaping Li11:26:23 AM
Once there is a pressure bump either radially or azithmuthally, it can slow down or even stop the dust radial drift. This can then also be helpful for dust size growth due to the more frequent collision between dust particles.

An exploration of the Zeeman Effect detectability of magnetic substructure in protoplanetary disks
-Magnetic fields are important in disks.
-what is the configuration of the field.
-vertical field??? (disk collapse occurs along field lines)
-but also
-toroidal field??? (the disk has angular momentum)
-what is magnetic field like in a typical disk???
-linear polarization doesnt tell the whole story.
-Zeeman effect: when there's no magnetic field, an energy level transition has one transition, wit a field they can be multiple transitions.
-proplyds should generally be fairly weakly magnetic.
-very technical discussion of magnetic fields which i am unable to follow.

Multi-band imaging of HD 34700 disk with Subaru/CHARIS
-i notice the disk is very floculent!
-premainsequence 5myr binary system, 5" separation
-365.5+/0 6.1 pc
-ring discontinuity, large gap, 5 spirals
-a single exposure detected scattered light from ring.
-data reduction between ringed star and reference star.
-no companion candidates detected.
-data reduction with a fake source: planet pops out easily. (so the real one has  no planet)
-darkening features, shadows cast by inner disks, geometric features related to outer spirals.
-very large pitch angles.
-stellar flyby or infall?
-one of the spirals might have formed differently.

A Hydrocarbon Rich Atmosphere in the Closest Planet Forming Disk?
-presenter first i've heard saying she explicitly supports BLM and opressed people. (Ilse Cleeves)
-ALMA revolutionized our image of planet formation.
-ALL HAIL HL TAU
-these photos are only 1% of the disk. The dust is a small constituent.
-ALMA is also changing our picture of gas as well.
-ALMA: image chemistry
-disks are structured chemistry! Patterns in abundances trace udnerlying chem/physical changes.
-planets forming at different locations in disks will have different compositions.
-C/O ratio of inner planets is lower.
-isotopic ratios (good for SS record)
-TW Hydra as a chemical rosetta stone. closest, best studied disk. every telescope that can osberve it has.
-understanding organic chem, deuterium chem, N2H+ distribution, sulfur chem, CO based temp maps, N isotope
-Hydrocarbons are excellent tracers of C/O. C2H
-C/O is actively changing in planet disks. carbon is mostly volatile, so you can move C vs O by moving around icy mantles.
-C3H2: are we looking at surface, midplane? planet forming or not?
-Not tracing planetforming midplane (0.25-2 scale heights above midplane)
-hydrocarbons on surface, but, the gas might be diving into the ring gaps?

X-ray Flaring Events Drive Non-Equilibrium Chemistry in Protoplanetary Disks
-Abygail Waggoner also highlights BLM, nice.
-Xray variablility for young stars.
-this has effects on chemistry.
-chemical/physical evolution is more dynamic than we assume?
-single x-ray flare can impact water abundance to the point it can be osberved.
-made a simulated xray light curve generator.
-implement into chemical model

A Weathering Framework to Model the Inorganic Carbon Cycle on Rocky Exoplanets
-NO DISKS??!! SACRILEGE!
-terrestrial carbon cycle: atmo to rivers/ocean, silicate weathering. ocean to seafloor. seafloor to mantle. mantle to atmo through outgassing/degassing
-silicate weathering: high temp, high co2 weathing.


plenary:
Our Dynamic Solar Neighborhood
-20-500pc =solar enighborfdhhfih
-intrinsically dim sources in beautiful detail in the solar neighbordhdosh
-the solar neighborhood has a good sample of low mass stellar and high mass planetary
-flight through the nearby solar neighborhood
-i wish i had taken more notes. might go back and rewatch


Laboratory Astrophysics Division (LAD) Meeting: Planetary Atmospheres, Protoplanetary Disks, and Small Bodies

LAD Early Career Award: Planets in a Bottle: Exploring Planetary Atmospheres in the Lab
-trying to understand atmospheric haze.
-she's acknowledging current events:
--Black Lives Matter
--shows a list of black folks who were killed by police recently.
--there is a problem
--moment of silence for these people.
--discussing privilege.
--white and male are overrepresented in planetary science and astronomy
--race is neglected in inclusivity discussions.
--absence of voices/lost paths,lost thoughts, lost ideas/who are we missing?
--who is missing from your list of nominees for awards, teams, etc.
--Clancy et al: double jeopardy in astro: women of color face greater risks of gendered and racial harrassment.
--too many people saying they don't feel safe at work.
--40% of woc don't feel safe for their gender, 20% due to their gender. AT THEIR JOB as Lunarplanetaryscience. This does not even include the people who have left.
--so few women of color in astro & p.s. that if they broke up race beyond "p o c" they risked individually identifying women of color.
--too many decide that racism and sexism and harassment is ok.
--where to start? nashville recommendations:
---remove barriers to access. financial, gre scores, sterotype threat
---create inclusive climate: effective mentoring, address microaggr.
---improving inclusive access to power, policy, & leadership.
---establish community of inclusive practice: active measures to ensure your event, teams, groups, is inclusive.
--lots of committees to address inclusivity.
-time for planets in a bottle.
-lab experiments
-how far can org chem proceed in an atmo w/o life?
-what materials are on ocean worlds and exoplanets?
-if we're seriously going to look for life, what molecules are ACTUALLY biosignatures, and which ones can we make without life by putting atmo chemicals and energy in a lab.
-haze layer could be the difference between liquid water and not, due to temperature.
-understand titan haze, you udnerstand exoplanet haze.
-organic haze is produced by CH4 photochem in mildly reduced atmo.
-this is not the one true path for haze formation. it's more complex than above.
-Titan's haze is not just hydrocarbon haze. nitrogen participates in chemistry, but mostly partitions itself into solid phases
-nitrogen increases particle production.
-titan isn't only haze because methane, it's hazy because nitrogen AND methane, a really good combination.
-cassini, labs, and models show nitrogen is important.
-miller-urey experiment is an early version of this kind of science. start with simple, abundant gases, expose to plasma or uv or other enrgy, get a complex organic solid.
-What do cassini mdiscoveries mean for lab?
-what happenes if you put in CO?
-aerosol production increases with CO concentration.
-nitrogen/methane/co is even better for haze formation.
-some of these hazes are important for life, like bio amino acids and bases A & G from dna.
-if CO does cool stuff, what about other compositions?
-exoplanets expand phase space of things which can be studied.
-H2 rich, H2O rich, and CO2 rich at 800 600 400 300 K, some with no methane, with all sorts of gases and particles resulting.
-water rich has even more haze, surprisingly and as yet inexplicably.
-abiotic molecular oxygen production from some of these atmosphere haze experiments. biosignatures made in the lab???
-(probably didn't make life in the lab)
-evidence of sugars?
-hazes don't require methane
-oxidized atmo may be favorable for haze
-planet atmo evolution means haze evolution.
-put titan haze and atmo through rigorous chemical analysis with Dragonfly.

Gregory Brannon3:19:06 PM
is it possible that there might be no valid biosignatures because exoplanets can make so many different kinds of organic haze? could we tell if it's from abiotic or biological sources?
Sarah Horst3:27:13 PM
I worry about this sometimes. We really need better models and to do that we need more experiments (of many different kinds) and also more observations of lots of different kinds of planets to validate the models (which exoplanets will definitely help with!)

Using Small Solar System Bodies to Trace Processes in the Early Solar System
-nex gen telescopes will probe terrestrial planet formation regions of proplyds
-looking at disk chemistry as well
-solar system is fairly unique among known systems
-least altered minor planets used to trace early solar system formation
-meteorites: well studied, have been altered
-icy asteroids: unexplored, may be partially unaltered
-comets: untraceable dynamics, formed cold, remained cold.
-icy sats: formed cold, have been heated. (evolved)
-interstellar objects (unexplored)
-Giotto spacecraft: do comets even HAVE solid nuclei? Yes, they're water ice and rocky bodies.
-stardust: sample return: dust migration in early solar system. not untouched distant bodies
-deep impact: comets are good insulators; little surface ice
-comet ejects large chunks of cm/10cm scales. cryovolcanoes, not water sublimation from surface. CO2 plays major role
-comets have mostly the same amount of carbon chains, some actually have less carbon chains. not related to formation after all
-rosetta provided enormous comet detail
-comets formed cold, remains cold.
-inherited from disk? inherited from presolar nebula?
-very porous, low density, low strength bodies
-what is primordial, what comes from sunlight? how do comets work?
-shouting matches in rosetta: do clathrates exist and are they important?
-new types of small bodies? long period comet without a tail, with S-type asteroid spectrum. No water allowed by observed spectrum!
-formed near SS snowline, ejected to oort cloud very early on.
-2 distinct resevoirs of molybdenum or tungsten rich meteorites: there was a change over time in proplyd, or materials were physically separated.
-Jupiter forms early to prevent mixing between molybenum and tungsten.
-Steve Desch, not our Steve tho, referenced.
-I also see Sean Raymond referenced!
-anything from beyond Jupiter can provide volatiles to earth and scatter into asteroid belt.
-single isotope won't tell the whole story re: earth's volatiles and comets.

New Near-UV H2O Cross-Sections Dramatically Affect Photochemistry of Anoxic Abiotic Rocky Planet Atmospheres
-modellin atmos of rocky exoplanets.
-upcoming era of the characterization of rocky exoplanets. we can currently characterized giant planets, we want rocky with JWST and ELTs
-photochemical models to prepare for observation programs and itnerpret measurments
-models disagree sometimes. some models: CO on the order of percent. other models: 100 PPM CO.
-early-earth-like-exoplanets. anoxic atmospheres, CO2-N2. like venus and mars.
-null signature for biosignatures: CO2/N2
-OH controls buildup of spectrally active gasses: CH4, CO, SO2. OH: detergent of (earth)'s atmo.
-OH controls stability of atmospheres. CO2 is efficiently destroyed by UV. CO2 atmosphere devolves into CO and O2, except OH recombines CO and O back to CO2.
-OH source: water photolysis. H2O+energy -> H+OH
-H2O Near UV prescriptions. actually not well observed, need prescriptions.
-modelling CO2-N2, intercomparison of 3 major models, repaired errors, didn't fix errors
-errors resulted from H2O cross section discrepancies.
-could reproduce high and low CO by changing model assuptions.
-lab measurements: triplicate measurements of N2 purged, subsaturation-no-droplet H2O at 292K
-New H2O NUV prescriptions: vastly different than expected.
-orders of magnitude more NUV absorption than expected. implications for photochemistry.
-eliminate low-outgassing abiotic O2 false positive around sunlike stars.
-higher OH abundances makes more prebiotically relevant compounds.
-get our models ready!
-models assume clement, 288K surface covered in a water ocean