AGENDA

3. AGENDA

6. Discussion • Adjourn • *Dinner on Own

11. ABSTRACTS

13. RachaelBeaton Checks& Balances:Testing theDistanceLadderDeterminationoftheHubbleConstant There are two primary means of determining the Hubble constant: (i) empirical determination via the distance ladder (parallax, Cepheids, SNe Ia) and (ii) model-dependent determination via anisotropies in the cosmic microwave background (CMB). These two methods currently disagree at greater than 3-sigma, which could imply we are missing physics from the standard model. An equally likely possibility is that there are unaccounted-for systematic uncertainties in either measurement that, once properly constrained, would relieve the tension. I will present tests of the traditional Cepheid-based distance scale that act to buttress these measurements to argue that it is hard to relieve the tension by adjusting the distance ladderalone. Notes:

14. IvanCabrera-Ziri Challenging the paradigm of the origin of multiple stellar populations in globular clusters Globular clusters are known to host star-to-star variations of some light elements. These multiple populations can be separated with extreme efficacy in some UV colour-colour plots. Recent photometric results have identified a new population among globular cluster stars. This population has been suggested to be the manifestation of a new abundance pattern where the initial mass fraction of He changes among cluster stars that share the same CNO values. The current paradigm for the formation of the multiple stellar populations in globular clusters assumes that variations in He are the product of chemical “enrichment” by the ashes of the CNO-cycle (which changes He and other elements like C, N and O simultaneously). I will present the first spectroscopic study of these stars, and explain what this means for the long held paradigm for the origin of the abundance variations in globularclusters. Notes:

15. EnaChoi ThesignatureofAGNfeedbackonCGMproperties Recently, theoretical work has begun to compare the simulated circumgalactic medium (CGM) to column densities and equivalent width measurements as a function of impact parameter from the center of the galaxy. The majority of the simulations underproduce the amount of metal-enriched gas at large impact parameters compared to observations and fail to match the large amount and high covering fraction of OVI measurements tracing the hottest gas phase, as well as less ionized cooler lines such as MgII, CIII and SiIV. However, none of these studies include mechanical AGN feedback, which may play an important role in driving winds and enriching CGM at large distance. To elucidate how the physical conditions and dynamical state of the CGM gas change by AGN feedback, we run a suite of hydrodynamical simulations incorporating a new treatment of AGN feedback which is implemented in a fully self-consistent way, launching high-velocity mass outflow. We post-process these sets of simul ations with a synthetic spectrum generation code and compare covering fractions, equivalent widths, ion ratios, and kinematics to observations as a function of impact parameter and specific star formation rate. We show that the AGN feedback effectively enrich CGM ‘inside-out’ by spreading centrally enriched metals to the outskirts of galaxies along the AGN-driven outflow, as well as ‘outside-in’, where winds propagate further from galaxies at earlier epochs of high AGN activity and then ejected metals recollect into the CGM at latertimes. Notes:

16. SusanClark Themagneticinterstellarmediuminthreedimensions The interstellar medium (ISM) is multi-phase, turbulent, and magnetic. This makes the ISM an ideal laboratory for studying the multi-scale physics of star formation and galactic evolution. This unfortunately also makes the ISM a formidable foreground for cosmology experiments, such as the search for inflationary gravitational wave B-mode polarization in the cosmic microwave background. I will discuss recent work on magnetic fields in the diffuse ISM, with a focus on insights from high-dynamic range observations of neutral hydrogen and polarized dust emission. Armed with an understanding of the link between the morphology of the neutral ISM and the magnetic field, I will present a new data-driven model for the polarized dust emission from the three- dimensionalISM. Notes:

17. PhilipCowperthwaite Chasing Optical Counterparts to Gravitational Wave Events with Next-GenerationFacilities. The era of joint gravitational wave and electromagnetic (GW-EM) astronomy began on August 17, 2017 with the coincident detection of gravitational waves and light from the binary neutron star merger GW170817. As the Advanced LIGO and Virgo interferometers continue to improve in sensitivity and new interferometers (LIGO-India and KAGRA) join the global network, we will begin to detect a greater number of merger events at greater distances. In this talk, I will discuss the landscape of joint GW-EM astronomy over the next decade. I will focus on several challenges including: detecting optical counterparts with next generation facilities such as LSST, prospects for modeling the transient light curves, and identifying promising targets for additional science goals such as joint GW-EMcosmology. Notes:

18. DianaDragomir Extending the period rangeof TESS planets One of the most exciting but also challenging outcomes of the TESS survey will be the discovery and characterization of longer-period exoplanets. In the coming years, we can look forward to measuring the masses and probing the atmospheres of a sizeable sample of small planets with periods beyond ~20 days. I will present the first such exoplanet discovered with TESS. For gas giants, we will be able to push to even longer periods. I will discuss how single-transit planet candidates from TESS can be leveraged toward thisgoal. Once confirmed, these long-period planets of all sizes will facilitate the search for trends between planet properties and orbital period by extending the period range over which such investigations can be undertaken. These studies will in turn enable new constraints on the composition and formation of temperate exoplanets. Notes:

19. DeckerFrench TidalDisruptionEventHostGalaxies:PuzzlesandToolsforFutureSurveys The accretion of individual stars by supermassive black holes can be observed when stars are torn apart through tidal forces, resulting in a bright observable flare. I will present recent work demonstrating that these tidal disruption events (TDEs) occur at a high rate in galaxies which have experienced a recent galaxy-wide burst of star formation. I will explore several possibilities for what might connect the small-scale dynamics at the centers of these galaxies to their large-scale star formation histories, and present a method for using this host galaxy preference to find new TDEs in next-generation large transientsurveys. Notes:

20. DanielGoldstein Foundations of Strongly Lensed Supernova Cosmology In this talk I will present solutions to some problems associated with using strongly gravitationally lensed supernovae (gLSNe) to measure the cosmological parameters. Chief among these are new methods for finding gLSNe and extracting their time delays in the presence of microlensing. The latter of these results involved performing simulations of radiation transport in supernova atmospheres. I will also talk about how these simulations provided evidence that some Type Ia supernovae come from sub-Chandrasekhar mass progenitors. Notes:

21. MaxGronke TheWindofChange:moving,multiplying,andmeasuringcoldgas Multiphase gas is omnipresent in astrophysical systems but it is notoriously hard to understand and model. During my talk, I will discuss the phenomenon of galactic winds which are are large-scale, multiphase outflows crucial for the galactic ecosystem. The common picture is that the cold gas within them has been accelerated by ram pressure forces. However, reproducing this observation in hydrodynamical simulations has proven to be challenging - simply because the destruction time is shorter than the acceleration time. During my talk, I will show some analytical estimates and results from recent (magneto-)hydrodynamics simulations which suggest a solution to this classical "entrainment problem". I will conclude by discussing potential implications for larger scale galactic simulations, and observables of cold gas in the surroundings of galaxies. In particular, I want to point out that the Lyman-alpha line can be a powerful probe of the distribution of neutral hydrogen which reveals problems of most currentsimulations. Notes:

22. AnneJaskot TheNeutralISMandtheEscapeofIonizingRadiation The reionization of the intergalactic medium at z>6 is one of the major transformations in the universe’s history, yet we still do not know which galaxies were responsible. Since we cannot directly detect ionizing radiation from galaxies at z>6, we must study lower redshift systems to understand how and from which galaxies ionizing radiation escapes. Some of the most promising lower-redshift analogs are the Green Pea galaxies, one of the only known populations of star-forming galaxies with escaping ionizing radiation. Using VLA HI 21 cm and HST COS UV spectral observations, I will discuss the neutral gas content and geometry of the Green Peas and the implications for the escape of ionizing radiation. Finally, I will introduce the Low- Redshift Lyman Continuum Survey, an HST survey of low-redshift galaxies that will systematically test proposed diagnostics of ionizing radiationescape. Notes:

23. AlexanderJi TheNeutralISMandtheEscapeofIonizingRadiation Several independent lines of evidence now suggest that neutron star mergers are the dominant form of r- process element production in the universe. The composition of the ejecta may differ in each merger, which is reflected by variations in the lanthanide fraction (XLa). The lanthanide fractions produced by neutron star mergers can be inferred both from abundances of metal-poor stars and from observations of kilonova afterglows. Here, I present the lanthanide fraction distribution computed from metal-poor stars. The bulk distribution peaks at logXLa ~ -2.0, roughly matching the lanthanide fraction inferred for the afterglow of GW170817. However, the stars with the highest r-process enhancements ([Eu/Fe] > 0.7) logXLa ~ -1.5. We thus expect upcoming followup of kilonova afterglows to detect a population of neutron star mergers with higher lanthanide fractions, reinforcing the importance of late-time infrared observations. If high-XLa afterglows of neutron star mergers are not found, this may imply that the stars with the highest r-process enhancements have a different origin for their r-processelements. Notes:

24. SeanJohnson Surveysof metalenrichedhalogas atz<1aroundgalaxiesfromfielddwarfsto quasar hosts in absorption andemission The growth and evolution of galaxies is fueled by baryon accretion from circum-/intergalactic gas reservoirs and satellites. In turn this accretion is regulated by feedback from stars/supernovae and active galactic nuclei. Observations of the diffuse halo gas around galaxies that dominates the baryon budget (often called the circum-galactic medium) therefore represent a sensitive means of probing the physical processes that govern galaxy evolution. I will present results from a deep and highly complete galaxy redshift survey in the fields of quasars with high quality UV absorption spectra from HST as well as a new programs to observe the enriched halo gas of quasar hosts in absorption and emission. Together, these observations provide a census of the metal enriched halo gas of a wide range of galaxies from star-forming field dwarfs to massive quasar hosts to better inform out understanding of the baryon cycles that regulate galaxygrowth. Notes:

25. MelodieKao UsingRadioEmissionfromBrownDwarfstoUnderstandPlanetaryMagnetism Magnetic fields play a pervasive role in stellar and planetary systems, impacting interior structure, atmospheric evolution, and habitability. Empirical studies of fully convective dynamos are particularly important for characterizing the magnetic fields of planetary systems and cool substellar objects because such dynamos are ubiquitousinlowmassstars,browndwarfs,gasgiantplanets,andevensmallrockyplanets. Until we can measure fields on exoplanets, the best tests of exoplanetary convective dynamos are young planetary-mass objects. Observations of coherent radio pulses at GHz frequencies provide the only direct measurements of magnetic fields on L and later type brown dwarfs and planetary-mass objects. I present the first radio detection of a free-floating young, planetary-mass object, review the state of the art for measurements of radio emission from other young planetary-mass objects, highlight implications for models of substellar magnetism, and discuss implications for searches of radio emission from extrasolar planets and how next generation radio capabilities can push our understanding of brown dwarf and extrasolar planetary magnetism. Notes:

26. SebastiaanKrijt PhysicalandchemicalevolutionofCOinprotoplanetarydisks Observational studies of young protoplanetary disks are finding that the CO to hydrogen ratio in the warm regions of several disks is up to 1 to 2 orders of magnitude lower than in the interstellar medium, possibly showing variability with radial distance from the central star. Understanding the origin of this dramatic depletion is important because CO and its isotopologues are still the most commonly used gas mass tracers, and disk mass estimates therefore depend directly on understanding the CO to hydrogen ratio. Recent studies focusing exclusively on astrochemical (i.e., local destruction of CO) or physical (i.e., sequestration of CO ice) processes have been only partially successful in explaining the observed trends, both having difficulties reaching the reported levels of depletion on reasonable timescales. I will present new simulations that combine all relevant chemical and physical processes self-consistently, show how their combined effects solve the timescale issue, and discuss how models like these might be used to further our understanding of disks and the early stages of planetformation Notes:

27. SarahLoebman Simulating the Evolving Milky Way in the Era ofGaia The release of Gaia DR2 transformed our perspective from a static image of the Milky Way to a 3D movie that is alive with the motion of over a billion stars. This unprecedented dataset, crossed matched with existing survey data, holds vast potential for constraining the origin and evolution of our Galaxy at its earliest epochs. I will review recent results from two separate groups that suggest the inner Milky Way is dominated by stellar debris from a single, large satellite merger that occurred 10 Gyr ago. Hydrodynamic simulations can help inform our understanding of this merger event and provide evidence for a causal connection between the accretion event and the genesis of the chemically enhanced thick disk. I will further discuss what orbital analysis of stellar halo stars can or cannot tell us about theirorigin. Notes:

28. CharlotteMason What Can Galaxies Tell Us AboutReionization? The timeline of reionization is currently uncertain but if it is accurately measured it can unveil properties of 'first light' sources. I will describe how we can use galaxies at our current observational frontiers to learn about reionization. In particular, Lyman alpha (Lyα) emission from galaxies can probe the intergalactic medium at high redshift, but requires modeling physics from pc to Gpc scales. I will present current constraints on reionization from observations of galaxies, focusing on Lyα observations at z>6 using a multi-scale forward- modelling approach, and describe future prospects withJWST. Notes:

29. BrettMcGuire Probing TheOriginsofAromaticsinSpacewithGOTHAM Aromatic molecules (typically 5 and 6-carbon rings) are at the core of nearly every organic chemistry reaction on Earth. Some 80% of cataloged chemical species contain one. In space, the enigmatic polycyclic aromatic hydrocarbons (PAHs) are thought to contain as much as 25% of interstellar carbon. Yet, we cannot disentangle their overlapping signals, and thus we cannot study their chemistry directly. In molecular clouds, while more than 20 species have been found with enough carbons to form an aromatic ring, only two (10%, not 80%) have been detected. I will discuss our first detection of the second, benzonitrile, in the cold, starless cloud TMC-1, and the laboratory and observational programs that detection has kicked off, focusing on the ongoing GOTHAM (GBT Observations of TMC-1: Hunting Aromatic Molecules) LargeProject. Notes:

30. AnneMedling TracingBlackHoleFuelingandFeedbackinHighResolution I will present KOALA: the Keck OSIRIS AO LIRG Analysis, an adaptive optics-assisted near-infrared integral field spectroscopy campaign of 30+ nearby gas-rich galaxy merger nuclei. Our dataset traces stellar and gas kinematics and properties at few 10s of pc resolution, providing an excellent laboratory for studying the fueling and feedback associated with the central supermassive black holes and nuclear starbursts. Recent long-baseline ALMA observations enable a true multiphase picture of the nuclear disks/inflows and outflows around supermassive black holes, critical constraints for hydrodynamic simulations of black hole accretion andfeedback. Notes:

31. AaronMeisner Revealing the Sun's Coldest Neighbors withNEOWISE A complete census of the solar neighborhood provides the best way to identify and study the Galactic substellar population and constrain its mass function. NASA’s WISE satellite, with its unique wide-area sensitivity at 4.6 microns, has unrivaled potential to pinpoint the coldest brown dwarfs down to planetary masses. I have been leading a wide-ranging effort to repurpose the vast NEOWISE asteroid-hunting data set for Galactic (and extragalactic) astrophysics, by producing the deepest ever full-sky maps, source catalogs, and proper motion measurements at 3-5 microns. Thousands of previously overlooked brown dwarfs have already been revealed by mining these new all-sky data products. I will highlight our ongoing Spitzer campaign targeting the coolest such discoveries, several of which appear to be among the coldest brown dwarfs yet known. JWST follow-up will be necessary to fully characterize these extremely faint, cold discoveries and thereby better constrain the low-mass cutoff of starformation. Notes:

32. GauthamNarayan Learning about progenitor physics with RAPIDfollow-up of Kepler Supernovae I will present type Ia supernovae discovered with the K2 mission as part of the Kepler Extragalactic Survey (KEGS) during campaigns 16 and 17. The K2 observations have an exquisite 30-minute cadence, and crucially, have incomparable sampling along the early-rise, allowing us to probe the physics of the explosions. I’ll detail the constraints we infer from comparing the observations of these objects to physical models of type Ia explosions and discuss the implications for different SNIa progenitor scenarios. I’ll discuss our work on Real- time Photometric Identification (RAPID) - a cutting edge deep learning framework to identify such events within the thousands being discovered by the Zwicky Transient Facility (ZTF), and how we’re preparing the community to jump scale from the current-generation of surveys to LSST using the ANTARES brokersystem. Notes:

33. EricaNelson The Emergence of GalacticStructure I will discuss the emergence of galactic structure: how the Universe evolved from its uniform state shortly after the Big Bang to the rich diversity of galaxies today. Despite having determined the primary structural building blocks that comprise local galaxies -- bulges and disks -- we still do not know how they formed. The improved spatial resolution with which we can now observe early galaxies has given us a clearer window into how they grew. Combining millimeter interferometry, near infrared integral field spectroscopy, and cosmological hydrodynamical simulations, I will discuss new insights into the formation of disks and bulges at the peak epoch of star formation. Finally, the impending launch of the James Webb Space Telescope will revolutionize our understanding of early galaxy formation. I will conclude with a discussion of where the field is moving and the rich discovery space in this new era of extragalacticastrophysics. Notes:

34. PaolaPinilla TransitionDisks:Laboratoriestoexploretheevolutionfromcosmicdusttoplanetesimals In this new era of powerful telescopes such as ALMA, we are now able to study the birth of planets in disks around young stars, in more detail than ever before. These new observations are revealing fascinating structures in protoplanetary disks that are transforming our understanding of the formation and evolution of planetary systems. In this talk, I will explain theoretical models of dust evolution in protoplanetary disks, in particular the dynamics and growth from cosmic dust to planetesimals. I will compare these theoretical predictions with current multi-wavelength observations of protoplanetary disks. I will focus on transition disks, one of the most mysterious set of protoplanetary disks. This link between models and observations is providing significant insights about how different physical conditions play a crucial role in the formation of planetesimals, and is extending our understanding of how initial conditions of protoplanetary disks are reflected in the large diversity of extrasolarsystems. Notes:

35. Sarah Sadavoy Resolving the Magnetic Field of IRAS 16293-2422 with ALMA We present ALMA high-resolution dust polarization observations of IRAS 16293-2422. The dust polarization and inferred magnetic field are well resolved across the protostellar sources and the filamentary structures seen between them. The magnetic field is aligned parallel to the filamentary structures rather than showing a pinched morphology expected for accreting stars. The parallel magnetic fields seen in IRAS 16293 are an unique feature and may represent magnetized accretion channels that have been theorized in the literature but never previously detected. Future theoretical work will need to understand both the origin of these filamentary structures and their impact on the evolution of the young stars.

36. AnnaSchauer Constraining First Star Formation with 21cmCosmology Within standard LambdaCDM cosmology, Population III (Pop III) star formation in minihalos of mass M > 5x10^5 Msol provides the first stellar sources of Lyman-alpha photons. The Experiment to Detect the Global Epoch of Reionization Signature (EDGES) has measured a strong absorption signal of the redshifted 21 cm radiation from neutral hydrogen at z~17, requiring efficient formation of massive stars before then. We investigate whether star formation in minihalos plays a significant role in establishing the early Lyman-alpha background required to produce the EDGES absorption feature. We find that Pop III stars are important in providing the necessary Lyman-alpha flux at high redshifts, and derive a best-fitting average Pop III stellar mass of ~120 Msol per minihalo. Further, it is important to include baryon-dark matter streaming velocities in the calculation, to limit the efficiency of Pop III star formation in minihalos. Without this effect, the cosmic dawn coupling between 21 cm spin temperature and that of the gas would occur at redshifts higher than what is implied by EDGES. Notes:

37. EvanSchneider Theoriginof multiphasegalaxyoutflows Star-forming galaxies are often observed to host galactic winds - gas that is flowing out of the galaxy in phases ranging from cold molecular clouds to hot X-ray emitting plasma. While these multiphase outflows are routinely observed, theoretically constraining their origin and evolution has proven difficult. Explaining the prevalence and velocities of the cool ionized phase (T~10^4 K) in particular poses a challenge. In this talk, I will discuss a potential dual origin for this cool gas. Through a series of extremely high-resolution simulations run with the GPU-based Cholla code, I will show that in high star formation surface density systems, dense disk gas can be pushed out by the collective effect of clustered supernovae, explaining the low-velocity material. Simultaneously, shredding and mixing of these clouds increases the density of the hot phase of the wind, leading to large-scale radiative losses that produce high velocity cool gas. In addition to explaining the nature of outflows themselves, these multiphase winds could potentially be a source of the cool photo- ionized gas that is found in abundance in galaxyhalos. Notes:

38. JosiahSchwab DoubleWhiteDwarfMergersandtheFormationofRCoronaeBorealisStars The merger of two white dwarfs is a promising channel for the production of hydrogen deficient stars. I will discuss the modeling these merger events, including the process of connecting the output of hydrodynamical simulations of the merger to stellar evolution calculations of their remnants. As an example, I will present the results of simulations of the formation and evolution of R Coronae Borealis stars (RCBs) using the MESA stellar evolutioncode. Notes:

39. IreneShivaei Amulti-wavelengthstudyof starformationratediagnosticsatintermediateredshifts Star formation rate (SFR) is one of the fundamental parameters that defines galaxies and their evolution across cosmic time. Although multi-wavelength SFR diagnostics have been extensively studied in nearby galaxies, high-redshift galaxies have intrinsic physical differences that may affect the level of accuracy of the local calibrations. Using a large sample of rest-frame optical spectra of galaxies at z~2 from the MOSDEF survey, and incorporating UV and IR data from Hubble, Spitzer, and Herschel space telescopes, I will review our recent findings on some of the most commonly-used SFR indicators at z~1.5-3.5, the peak epoch of star formation activity in the universe. In the process of studying the SFR diagnostics, we will gain valuable insights on the stellar and dust conditions in high redshift galaxies and how they evolve with cosmic time. Moreover, I will review the main goals of the US JWST/MIRI extragalactic GTO program to construct a mid-IR survey in the HUDF field, covering 30 square-arcmin with eight MIRI bands at 5-25micron. Notes:

40. JordanStone The LEECH Exoplanet Imaging Survey: Limits on PlanetOccurrence Rates under ConservativeAssumptions I will present the results of the largest L' (3.8 um) direct imaging survey for exoplanets to date, the Large Binocular Telescope Interferometer (LBTI) Exozodi Exoplanet Common Hunt (LEECH). Cool planets emit a larger share of their flux in L' compared to shorter wavelengths, affording LEECH an advantage in detecting low-mass, old, and cold-start giant planets. LEECH emphasized proximity over youth in target selection, probing physical separations smaller than other direct imaging surveys. For FGK stars, LEECH outperforms many previous studies, placing tighter constraints on the hot-start planet occurrence frequency interior to ~20 au. For less luminous, cold-start planets, LEECH provides the best constraints on giant-planet frequency interior to ~20 au around FGK stars. Direct imaging survey results depend sensitively on both the choice of evolutionary model (e.g., hot or cold- start) and assumptions (explicit or implicit) about the shape of the underlying planet distribution, in particular its radial extent. Artificially low limits on the planet occurrence frequency can be derived when the shape of the planet distribution is assumed to extend to very large separations, well beyond typical protoplanetary dust-disk radii (~50 au), and when hot-start models are used exclusively. LEECH places a conservative upper limit on the planet occurrence frequency using cold-start models and planet population distributions that do not extend beyond typical protoplanetary dust-disk radii. We find that ~90% of FGK systems can host a 7 to 10 Jupiter mass planet from 5 to 50~au. This limit leaves open the possibility that planets in this range arecommon. Notes:

41. TuguldurSukhbold Missing Red Supergiants and CarbonBurning Direct imaging studies of supernova progenitors are providing unique opportunities to decode the relationship between birth properties and final fates of massive stars. Recent measurements on Type II core-collapse supernova progenitors indicate a possible threshold around ~ 16-20 solar masses, where red supergiants with larger birth masses do not appear to result in supernova explosions, and instead possibly imploding directly into a black hole. This is now widely known as the "missing red supergiant problem" and is often claimed that it challenges our current understanding of stellar evolution and explosion. In this talk I will argue that this is in fact a theoretically expected result, and it is not a coincidence that this observed threshold closely matches with the critical transition of central carbon burning in massive stars from convective to radiative regime, after which the stellar cores become significantly harder to blow up. I'll provide a general sensitivity of this transition mass with uncertain input stellar physics, with a particular focus on the reaction rate of c12(a,g) and overshoot mixing efficiency. I will also turn the problem around, and present the potential of use of this observed upper mass limit of exploding red supergiants to constrain massive stellar evolutioncalculations. Notes:

42. JamieTayar CoreandSurfaceRotationRatesofEvolvedIntermediateMassStars Intermediate mass stars (M ~ 2.0 - 3.0 Msun) provide important tests of the role of rotation in the structure and evolution of stars because they live in an important transitional regime. Like massive stars, they rotate rapidly on the main sequence and have convective cores. However, they evolve to become secondary red clump stars, where their structure and internal rotation can be measured with the tools of red giant asteroseismology developed for lower mass stars. I will demonstrate that the slow surface rotation rates of these stars provide conclusive evidence for enhanced angular momentum loss and I will also show that the core rotation rates of these stars provide strong evidence for significant angular momentum transport between the cores and envelopes of these stars on a timescale similar to their evolution. Finally, I will discuss the implications of these results for models of internal transport and the impact of rotation on stellar evolution. Notes:

43. JohannaTeske Characterizingsmallplanetsfromthegroundup With the launch in spring 2018 of the Transiting Exoplanet Survey Satellite (TESS), a new phase of exoplanet detection, follow-up, and characterization began. In this talk, I will describe the motivation and methodology behind a new ground-based survey I am leading to study small transiting planets detected by TESS. This survey, combining several different observational techniques, is designed to investigate whether super-Earth (~1-1.6 Rearth) and sub-Neptune (~2-3 Rearth) planets formed in the same way but were sculpted by post- formation processes and so appear different now, or formed differently from the start. The goal of this survey is to double the number of well-characterized small planets known at the start of TESS, while creating an unbiased sample for better constraining the small end of the mass-radius relation. The products of this survey and others like it will feed directly into near-term (JWST, SDSS-V) and longer-term (LUVOIR, HabEx, OST, EELTs) projects intended to measure exoplanet atmospheric compositions, detect evidence of life, and understand how common Earth-like planets are in theGalaxy. Notes:

44. Yuan-SenTing Milky Way, machine learning, bigdata Understanding physical processes responsible for the formation and evolution of galaxies like the Milky Way is a fundamental but unsolved problem in astrophysics. Fortunately, most stars are long-lived. As such, using the stars as "fossil records" (what is known as Galactic archaeology) can offer unparalleled insight into the assembly of galaxies. In recent years, the landscape of Galactic archaeology is rapidly changing thanks to on- going large-scale surveys (astrometry, photometry, spectroscopy, asteroseismology) which provide a few orders of magnitude more stars than before. In this talk, I will discuss new "phenomenological" opportunities enabled by large surveys. I will also discuss how machine-learning tools could leverage the big data about the Milky Way by maximally harnessing information from low-resolution stellar spectra as well as the time-series photometric fluxes of stars. I will also present the new opportunities in Galactic archaeology in the era of deep photometry, such as LSST andDES Notes:

45. SiyaoXu Turbulent dynamo in a weakly ionizedmedium The small-scale turbulent dynamo is an important process contributing to the cosmic magnetization. In partially ionized astrophysical plasmas, the dynamo growth of magnetic energy strongly depends on the coupling state between ions and neutrals and the ion-neutral collisional damping effect. A new damping stage of turbulent dynamo in a weakly ionized medium was theoretically predicted by Xu & Lazarian (2016). By carrying out a 3D two-fluid dynamo simulation, we for the first time numerically confirmed the physical conditions and the linear-in-time growth of magnetic field strength of the damping stage of dynamo. The dynamo-amplified magnetic field has a characteristic length as the damping scale, which increases with time and can reach the injection scale of turbulence after around eight largest eddy-turnover times given sufficiently low ionization fraction and weak initial magnetic field. Due to the weak coupling between ions and neutrals, most turbulent energy carried by neutrals cannot be converted to the magnetic energy, resulting in a relatively weak magnetic field at the end of dynamo. This result has important implications for the growth of magnetic fields in the partially ionized interstellar medium and shock acceleration of Galactic cosmicrays. Notes:

46. KeZhang SystematicCOdepletioningas-richprotoplanetarydisks CO is the most commonly used gas tracers in protoplanetary disks. It is typically assumed to have an interstellar abundance inside the warm molecular layer of a disk and thus is assured to serve as a proxy of the gas mass distribution of a disk. However, recent observations suggest that the CO gas abundance in numerous protoplanetary disks (several-Myr-old) may be depleted by a factor of ten or more compared to its interstellar ratio. The proposed depletion mechanisms include chemical processes that convert CO into other molecules and the evolution of ice-coated dust grains that sequesters CO in the disk mid-plane. These chemical and physical processes are expected to alter the CO gas abundance in both location and time. I will talk about how the CO abundance varies with radius in four well- studied disks, based on spatially resolved CO isotopologue line observations and detailed thermo-chemical models. I will also show the first direct evidence that the CO gas abundance is similar to the ISM ratio in a young embedded disk (<1 Myr old). These studies open a new front to study the multi-dimensional evolution of molecular reservoirs during planetformation. Notes:

47. PARTICIPANTS