arXiv subjects

Duncan Christie

Publications and source records attributed to Duncan Christie.

At least 19 recordsLinked to original sources

arXiv2026

Three-dimensional transport-induced chemistry on temperate sub-Neptune K2-18b, Part II: the combined effects of atmospheric dynamics and chemical reactions

The upper atmospheres of temperate sub-Neptunes are strongly influenced by atmospheric dynamics due to their cool equilibrium temperature and thereby longer chemical timescales than the atmospheric dynamical timescales. In this study, we used a three-dimensional (3D) general circulation model to investigate the transport-induced disequilibrium chemistry and vertical mixing on temperate gas-rich mini-Neptunes, using K2-18b as an example. We model K2-18b assuming 180 times solar metallicity and consider it as either a synchronous or an asynchronous rotator, exploring spin-orbit resonances of 2:1, 6:1, and 10:1. We find that the vertical transport affects the chemical structure significantly, making CO$_2$ and CO more abundant ($\sim$10$^{-3}$) in the upper atmosphere compared to the chemical equilibrium abundance (<10$^{-15}$), and horizontal winds further homogenize the chemical composition zonally in this region. Molecular abundances in the photosphere generally agree across different rotation periods. We employ a passive tracer in the model to estimate the one-dimensional (1D) equivalent eddy-diffusion coefficient ($K_{zz}$) of K2-18b, providing a parameter useful for future 1D atmospheric models. Additionally, synthetic transmission spectra generated from our model are compared with the JWST observations, and we find that our model can provide a comparable fit to the observations. This work offers a 3D perspective on transport-induced chemistry on a temperate sub-Neptune and derives vertical mixing parameters to support 1D modelling.

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arXiv2026

Super-Solar Metallicity and Tentative Evidence for Photochemistry on WASP-96b from JWST and Ground-Based VLT Transmission Spectroscopy

With its expanded wavelength coverage and increased precision compared to previous space-based observatories, JWST provides the opportunity to revisit benchmark planets and view them in a new light. Here, we conduct an in-depth study of the atmosphere of the hot-Saturn WASP-96b combining a new JWST NIRSpec/G395H transit with archival NIRISS/SOSS and VLT/FORS2 transmission spectra. The combined spectrum shows clearly-visible features from H2O, CO2, and Na. CO, though, remains unconstrained, precluding a firm metallicity derivation from free retrievals alone. However, self-consistent grids yield a broadly super-stellar atmospheric metallicity of 2-6x stellar. When combined with a roughly stellar C/O ratio ($0.41^{+0.10}_{-0.09}$ from self-consistent grids), we find that WASP-96b potentially formed via core-accretion beyond the H2O snowline and subsequently accreted volatile-rich material. Free retrievals also find a moderate preference (ln B=2.69) for models with SO2 versus without. WASP-96b falls directly on the proposed "SO2 shoreline" and the retrieved SO2 abundance is well-matched to predictions from photochemical models. Our combined spectrum displays an optical slope, which our models fit with opacity from scattering aerosols -- either small-particle condensate clouds or photochemical hazes -- though we cannot completely rule out the broad wings of Na or the effects of stellar contamination. Future observations are necessary to disentangle these effects. Finally, we explore the possibility for limb asymmetry in WASP-96b's transmission spectrum and provide several tests to identify asymmetries in our data. We encourage the community to prioritize the development of a robust pathway to quantify the presence of limb asymmetry -- particularly for low signal-to-noise cases.

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arXiv2025

Three-dimensional Transport-induced Chemistry on Temperate sub-Neptune K2-18b, Part I: the Effects of Atmospheric Dynamics

The low equilibrium temperatures of temperate sub-Neptunes lead to extremely long chemical timescales in their upper atmospheres, causing the abundances of chemical species to be strongly shaped by atmospheric transport. Here, we used a three-dimensional (3D) general circulation model involving a passive tracer to investigate the atmospheric circulation and 3D transport of temperate gas-rich sub-Neptunes, using K2-18b as an example. We model K2-18b as a synchronous or asynchronous rotator, exploring spin-orbit resonances (SOR) of 2:1, 6:1, and 10:1. We find that the strong absorption of CO$_2$ and CH$_4$ induces a detached convective zone between 1 and 5 bar, resulting in strong vertical mixing at these levels. The upper atmosphere is dominated by eastward winds (an equatorial superrotating jet present in all simulations), leading to warmer evening terminators and approximately 20% higher passive tracer mass mixing ratios compared to the morning terminators. Rotation rates have minimal impact on the strength of global mean vertical mixing, but significantly influence the latitudinal distribution of passive tracers. For synchronous, 2:1 SOR, and 6:1 SOR simulations, passive tracers are more abundant in the upwelling branches at latitudes within 60$^\circ$, while for the 10:1 SOR simulation, strong transient eddies at high latitudes (>70$^\circ$) between 0.1 to 1 bar can transport passive tracers upward from the deep atmosphere, making them more abundant there, despite their alignment with the downwelling branch of the large-scale circulation. This study focuses on the atmospheric dynamics and its influence on passive tracer transport, while a follow-up paper will incorporate active chemical species.

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arXiv2025

WASP-121b's transmission spectrum observed with JWST/NIRSpec G395H reveals thermal dissociation and SiO in the atmosphere

WASP-121b has been established as a benchmark ultrahot Jupiter, serving as a laboratory for the atmospheric chemistry and dynamics of strongly irradiated extrasolar gas giants. Here, we present and analyze WASP-121b's transmission spectrum observed with NIRSpec G395H on board the James Webb Space Telescope and find evidence for the thermal dissociation of H$_2$O and H$_2$ on the planet's permanent dayside. Additionally, we detect SiO at a statistical significance of $5.2\sigma$ which is compatible with chemical equilibrium in the atmosphere. Constraining the abundance of SiO and abundance ratios between silicon and volatile atoms in WASP-121b's atmosphere could help discriminate between possible migration histories of the planet. The three-dimensional nature of thermal dissociation on WASP-121b's dayside and of recombination on its nightside, however, poses a challenge to constraining molecular abundances and elemental abundance ratios from the transmission spectrum. To account for this, we implemented an atmospheric model in the NEMESIS framework that splits the planet's atmosphere into dayside and nightside. A retrieval applying our atmospheric model to WASP-121b's transmission spectrum favors a higher H$_2$O abundance on the nightside than on the dayside, demonstrating the impact of hemispheric heterogeneity when attempting to constrain WASP-121b's bulk H$_2$O inventory.

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arXiv2025

Escaping Helium and a Highly Muted Spectrum Suggest a Metal-Enriched Atmosphere on Sub-Neptune GJ3090b from JWST Transit Spectroscopy

Sub-Neptunes, the most common planet type, remain poorly understood. Their atmospheres are expected to be diverse, but their compositions are challenging to determine, even with JWST. Here, we present the first JWST spectroscopic study of the warm sub-Neptune GJ3090b (2.13R$_\oplus$, Teq~700 K) which orbits an M2V star, making it a favourable target for atmosphere characterization. We observed four transits of GJ3090b; two each using JWST NIRISS/SOSS and NIRSpec/G395H, yielding wavelength coverage from 0.6-5.2 $\mu$m. We detect the signature of the 10833 \r{A} metastable Helium triplet at a statistical significance of 5.5$\sigma$ with an amplitude of 434$\pm$79 ppm, marking the first such detection in a sub-Neptune with JWST. This amplitude is significantly smaller than predicted by solar-metallicity forward models, suggesting a metal-enriched atmosphere which decreases the mass-loss rate and attenuates the Helium feature amplitude. Moreover, we find that stellar contamination, in the form of the transit light source effect, dominates the NIRISS transmission spectra, with unocculted spot and faculae properties varying across the two visits separated in time by approximately six months. Free retrieval analyses on the NIRSpec/G395H spectrum find tentative evidence for highly muted features and a lack of CH4. These findings are best explained by a high metallicity atmosphere (>100x solar at 3$\sigma$ confidence, for clouds at $\sim \mu$bar pressures) using chemically-consistent retrievals and self-consistent model grids. Further observations of GJ3090b are needed for tighter constraints on the atmospheric abundances, and to gain a deeper understanding of the processes that led to its potential metal enrichment.

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arXiv2025

Modeling Atmospheric Ion Escape from Kepler-1649 b and c over Time

Rocky planets orbiting M-dwarf stars are prime targets for atmospheric characterization, yet their long-term evolution under intense stellar winds and high-energy radiation remains poorly constrained. The Kepler-1649 system, hosting two terrestrial exoplanets orbiting an M5V star, provides a valuable laboratory for studying atmospheric evolution in the extreme environments typical of M-dwarf systems. In this Letter we show that both planets could have retained atmospheres over gigayear timescales. Using a multi-species magnetohydrodynamic model, we simulate atmospheric ion escape driven by stellar winds and extreme ultraviolet radiation from 0.8 to 4.0 Gyr. The results reveal a clear decline in total ion escape rates with stellar age, as captured by a nonparametric LOWESS regression, with O$^{+}$ comprising 98.3%-99.9% of the total loss. Escape rates at 4.0 Gyr are two to three orders of magnitude lower than during early epochs. At 0.8 Gyr, planet b exhibits 3.79$\times$ higher O$^{+}$ escape rates than planet c, whereas by 4.0 Gyr its O$^{+}$ escape rate becomes 39.5$\times$ lower. This reversal arises from a transition to sub-magnetosonic star-planet interactions, where the fast magnetosonic Mach number, $M_f$, falls below unity. Despite substantial early atmospheric erosion, both planets may have retained significant atmospheres, suggesting potential long-term habitability. These findings offer predictive insight into atmospheric retention in the Kepler-1649 system and inform future JWST observations of similar M-dwarf terrestrial exoplanets aimed at refining habitability assessments.

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arXiv2024

JWST/NIRISS reveals the water-rich "steam world" atmosphere of GJ 9827 d

With sizable volatile envelopes but smaller radii than the solar system ice giants, sub-Neptunes have been revealed as one of the most common types of planet in the galaxy. While the spectroscopic characterization of larger sub-Neptunes (2.5-4R$_\oplus$) has revealed hydrogen-dominated atmospheres, smaller sub-Neptunes (1.6--2.5R$_\oplus$) could either host thin, rapidly evaporating hydrogen-rich atmospheres or be stable metal-rich "water worlds" with high mean molecular weight atmospheres and a fundamentally different formation and evolutionary history. Here, we present the 0.6--2.8$\mu$m JWST NIRISS/SOSS transmission spectrum of GJ 9827 d, the smallest (1.98 R$_\oplus$) warm (T$_\mathrm{eq, A_B=0.3} \sim 620$K) sub-Neptune where atmospheric absorbers have been detected to date. Our two transit observations with NIRISS/SOSS, combined with the existing HST/WFC3 spectrum, enable us to break the clouds-metallicity degeneracy. We detect water in a highly metal-enriched "steam world" atmosphere (O/H of $\sim 4$ by mass and H$_2$O found to be the background gas with a volume mixing ratio of >31%). We further show that these results are robust to stellar contamination through the transit light source effect. We do not detect escaping metastable He, which, combined with previous nondetections of escaping He and H, supports the steam atmosphere scenario. In water-rich atmospheres, hydrogen loss driven by water photolysis happens predominantly in the ionized form which eludes observational constraints. We also detect several flares in the NIRISS/SOSS light-curves with far-UV energies of the order of 10$^{30}$ erg, highlighting the active nature of the star. Further atmospheric characterization of GJ 9827 d probing carbon or sulfur species could reveal the origin of its high metal enrichment.

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arXiv2024

Inhomogeneous terminators on the exoplanet WASP-39 b

Transmission spectroscopy has been a workhorse technique over the past two decades to constrain the physical and chemical properties of exoplanet atmospheres. One of its classical key assumptions is that the portion of the atmosphere it probes -- the terminator region -- is homogeneous. Several works in the past decade, however, have put this into question for highly irradiated, hot ($T_{eq}\gtrsim 1000$ K) gas giant exoplanets both empirically and via 3-dimensional modelling. While models predict clear differences between the evening (day-to-night) and morning (night-to-day) terminators, direct morning/evening transmission spectra in a wide wavelength range has not been reported for an exoplanet to date. Under the assumption of precise and accurate orbital parameters on WASP-39 b, here we report the detection of inhomogeneous terminators on the exoplanet WASP-39 b, which allows us to retrieve its morning and evening transmission spectra in the near-infrared ($2-5\ \mu$m) using JWST. We observe larger transit depths in the evening which are, on average, $405 \pm 88$ ppm larger than the morning ones, also having qualitatively larger features than the morning spectrum. The spectra are best explained by models in which the evening terminator is hotter than the morning terminator by $177^{+65}_{-57}$ K with both terminators having C/O ratios consistent with solar. General circulation models (GCMs) predict temperature differences broadly consistent with the above value and point towards a cloudy morning terminator and a clearer evening terminator.

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arXiv2024

JWST Reveals CH$_4$, CO$_2$, and H$_2$O in a Metal-rich Miscible Atmosphere on a Two-Earth-Radius Exoplanet

Even though sub-Neptunes likely represent the most common outcome of planet formation, their natures remain poorly understood. In particular, planets near 1.5-2.5$\,R_\oplus$ often have bulk densities that can be explained equally well with widely different compositions and interior structures, resulting in grossly divergent implications for their formation. Here, we present the full 0.6-5.2$\,\mu \mathrm{m}$ JWST NIRISS/SOSS+NIRSpec/G395H transmission spectrum of the 2.2$\,R_\oplus$ TOI-270d ($4.78\,M_\oplus$, $T_\mathrm{eq}$=350-380 K), delivering unprecedented sensitivity for atmospheric characterization in the sub-Neptune regime. We detect five vibrational bands of CH$_4$ at 1.15, 1.4, 1.7, 2.3, and 3.3$\,\mu$m (9.4$\sigma$), the signature of CO$_2$ at 4.3$\,\mu$m (4.8$\sigma$), water vapor (2.5$\sigma$), and potential signatures of SO$_2$ at 4.0$\,\mu \mathrm{m}$ and CS$_2$ at 4.6$\,\mu\mathrm{m}$. Intriguingly, we find an overall highly metal-rich atmosphere, with a mean molecular weight of $5.47_{-1.14}^{+1.25}$. We infer an atmospheric metal mass fraction of $58_{-12}^{+8}\%$ and a C/O of $0.47_{-0.19}^{+0.16}$, indicating that approximately half the mass of the outer envelope is in high-molecular-weight volatiles (H$_2$O, CH$_4$, CO, CO$_2$) rather than H$_2$/He. We introduce a sub-Neptune classification scheme and identify TOI-270d as a "miscible-envelope sub-Neptune" in which H$_2$/He is well-mixed with the high-molecular-weight volatiles in a miscible supercritical metal-rich envelope. For a fully miscible envelope, we conclude that TOI-270d's interior is $90_{-4}^{+3}\,$wt$\,\%$ rock/iron, indicating that it formed as a rocky planet that accreted a few wt % of H$_2$/He, with the overall envelope metal content explained by magma-ocean/envelope reactions without the need for significant ice accretion. TOI-270d may well be an archetype of the overall population of sub-Neptunes.

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arXiv2023

GMC Collisions As Triggers of Star Formation. VIII. The Core Mass Function

Compression in giant molecular cloud (GMC) collisions is a promising mechanism to trigger formation of massive star clusters and OB associations. We simulate colliding and non-colliding magnetised GMCs and examine the properties of prestellar cores, selected from projected mass surface density maps, including after synthetic {\it ALMA} observations. We then examine core properties, including mass, size, density, velocity, velocity dispersion, temperature and magnetic field strength. After four Myr, $\sim1,000$ cores have formed in the GMC collision and the high-mass end of the core mass function (CMF) can be fit by a power law $dN/d{\rm{log}}M\propto{M}^{-α}$ with $α\simeq0.7$, i.e., relatively top-heavy compared to a Salpeter mass function. Depending on how cores are identified, a break in the power law can appear around a few $\times10\:M_\odot$. The non-colliding GMCs form fewer cores with a CMF with $α\simeq0.8$ to 1.2, i.e., closer to the Salpeter index. We compare the properties of these CMFs to those of several observed samples of cores. Considering other properties, cores formed from colliding clouds are typically warmer, have more disturbed internal kinematics and are more likely to be gravitational unbound, than cores formed from non-colliding GMCs. The dynamical state of the protocluster of cores formed in the GMC-GMC collision is intrinsically subvirial, but can appear to be supervirial if the total mass measurement is affected by observations that miss mass on large scales or at low densities.

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arXiv2022

3D radiative-transfer for exoplanet atmospheres. gCMCRT: a GPU accelerated MCRT code

Radiative-transfer (RT) is a key component for investigating atmospheres of planetary bodies. With the 3D nature of exoplanet atmospheres being important in giving rise to their observable properties, accurate and fast 3D methods are required to be developed to meet future multi-dimensional and temporal data sets. We develop an open source GPU RT code, gCMCRT, a Monte Carlo RT forward model for general use in planetary atmosphere RT problems. We aim to automate the post-processing pipeline, starting from direct global circulation model (GCM) output to synthetic spectra. We develop albedo, emission and transmission spectra modes for 3D and 1D input structures. We include capability to use correlated-k and high-resolution opacity tables, the latter of which can be Doppler shifted inside the model. We post-process results from several GCM groups including ExoRad, SPARC/MITgcm THOR, UK Met Office UM, Exo-FMS and the Rauscher model. Users can therefore take advantage of desktop and HPC GPU computing solutions. gCMCRT is well suited for post-processing large GCM model grids produced by members of the community and for high-resolution 3D investigations.

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arXiv2020

GMC Collisions as Triggers of Star Formation. VII. The Effect of Magnetic Field Strength on Star Formation

We investigate the formation of stars within giant molecular clouds (GMCs) evolving in environments of different global magnetic field strength and large-scale dynamics. Building upon a series of magnetohydrodynamic (MHD) simulations of non-colliding and colliding GMCs, we employ density- and magnetically-regulated star formation sub-grid models in clouds which range from moderately magnetically supercritical to near critical. We examine gas and star cluster morphologies, magnetic field strengths and relative orientations, pre-stellar core densities, temperatures, mass-to-flux ratios and velocities, star formation rates and efficiencies over time, spatial clustering of stars, and kinematics of the stars and natal gas. The large scale magnetic criticality of the region greatly affects the overall gas evolution and star formation properties. GMC collisions enhance star formation rates and efficiencies in magnetically supercritical conditions, but may actually inhibit them in the magnetically critical case. This may have implications for star formation in different Galactic environments such as the Galactic Center and the main Galactic disk.

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arXiv2017

A Model of the H$α$ and Na Transmission Spectrum of HD 189733b

This paper presents a detailed hydrostatic model of the upper atmosphere of HD 189733b, with the goal of constraining its temperature, particle densities, and radiation field over the pressure range $10^{-4}-10\, μ\rm bar$, where the observed H$α$ transmission spectrum is produced. The atomic hydrogen level population is computed including both collisional and radiative transition rates. The Ly$α$ resonant scattering is computed using a Monte-Carlo simulation. The model transmission spectra are in broad agreement with the data. Excitation of the H(2$\ell$) population is mainly by Ly$α$ radiative excitation due to the large Ly$α$ intensity. The density of H(2$\ell$) is nearly flat over two decades in pressure, and is optically thick to H$α$. Additional models computed for a range of the stellar Lyman continuum (LyC) flux suggest that the variability in H$α$ transit depth may be due to the variability in the stellar LyC. Since metal lines provide the dominant cooling of this part of the atmosphere, the atmosphere structure is sensitive to the density of species such as Mg and Na which may themselves be constrained by observations. Since the H$α$ and Na D lines have comparable absorption depths, we argue that the center of the Na D lines are also formed in the atomic layer where the H$α$ line is formed.

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arXiv2017

The Interstellar Medium and Star Formation of Galactic Disks. I. ISM and GMC properties with Diffuse FUV and Cosmic Ray Backgrounds

We present a series of adaptive mesh refinement (AMR) hydrodynamic simulations of flat rotation curve galactic gas disks with a detailed treatment of the interstellar medium (ISM) physics of the atomic to molecular phase transition under the influence of diffuse FUV radiation fields and cosmic ray backgrounds. We explore the effects of different FUV intensities, including a model with a radial gradient designed to mimic the Milky Way. The effects of cosmic rays, including radial gradients in their heating and ionization rates, are also explored. The final simulations in this series achieve $4\:$pc resolution across the $\sim20\:$kpc global disk diameter, with heating and cooling followed down to temperatures of $\sim10\:$K. The disks are evolved for $300\:$Myr, which is enough time for the ISM to achieve a quasi-statistical equilibrium. In particular, the mass fraction of molecular gas stabilizes by $\sim$200 Myr. Additional global ISM properties are analysed. Giant molecular clouds (GMCs) are also identified and the statistical properties of their populations examined. GMCs are tracked as the disks evolve. GMC collisions, which may be a means of triggering star cluster formation, are counted and the rates compared with analytic models. Relatively frequent GMC collision rates are seen in these simulations and their implications for understanding GMC properties, including the driving of internal turbulence, are discussed.

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arXiv2017

GMC Collisions as Triggers of Star Formation. VI. Collision-Induced Turbulence

We investigate collisions between giant molecular clouds (GMCs) as potential generators of their internal turbulence. Using magnetohydrodynamic (MHD) simulations of self-gravitating, magnetized, turbulent, GMCs, we compare kinematic and dynamic properties of dense gas structures formed when such clouds collide compared to those that form in non-colliding clouds as self-gravity overwhelms decaying turbulence. We explore the nature of turbulence in these structures via distribution functions of density, velocity dispersions, virial parameters, and momentum injection. We find that the dense clumps formed from GMC collisions have higher effective Mach number, greater overall velocity dispersions, sustain near-virial equilibrium states for longer times, and are the conduit for injection of turbulent momentum into high density gas at high rates.

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arXiv2017

GMC Collisions As Triggers of Star Formation. IV. The Role of Ambipolar Diffusion

We investigate the role of ambipolar diffusion (AD) in collisions between magnetized giant molecular clouds (GMCs), which may be an important mechanism for triggering star cluster formation. Three dimensional simulations of GMC collisions are performed using a version of the Enzo magnetohydrodynamics code that has been extended to include AD. The resistivities are calculated using the 31-species chemical model of Wu et al. (2015). We find that in the weak-field, $10\:{\rm μG}$ case, AD has only a modest effect on the dynamical evolution during the collision. However, for the stronger-field, $30\:{\rm μG}$ case involving near-critical clouds, AD results in formation of dense cores in regions where collapse is otherwise inhibited. The overall efficiency of formation of cores with $n_{\rm H}\geq10^{6}\:{\rm cm}^{-3}$ in these simulations is increases from about 0.2% to 2% once AD is included, comparable to observed values in star-forming GMCs. The gas around these cores typically has relatively slow infall at speeds that are a modest fraction of the free-fall speed.

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arXiv2017

GMC Collisions as Triggers of Star Formation. III. Density and Magnetically Regulated Star Formation

We study giant molecular cloud (GMC) collisions and their ability to trigger star cluster formation. We further develop our three dimensional magnetized, turbulent, colliding GMC simulations by implementing star formation sub-grid models. Two such models are explored: (1) "Density-Regulated," i.e., fixed efficiency per free-fall time above a set density threshold; (2) "Magnetically-Regulated," i.e., fixed efficiency per free-fall time in regions that are magnetically supercritical. Variations of parameters associated with these models are also explored. In the non-colliding simulations, the overall level of star formation is sensitive to model parameter choices that relate to effective density thresholds. In the GMC collision simulations, the final star formation rates and efficiencies are relatively independent of these parameters. Between non-colliding and colliding cases, we compare the morphologies of the resulting star clusters, properties of star-forming gas, time evolution of the star formation rate (SFR), spatial clustering of the stars, and resulting kinematics of the stars in comparison to the natal gas. We find that typical collisions, by creating larger amounts of dense gas, trigger earlier and enhanced star formation, resulting in 10 times higher SFRs and efficiencies. The star clusters formed from GMC collisions show greater spatial sub-structure and more disturbed kinematics.

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arXiv2016

GMC Collisions as Triggers of Star Formation. II. 3D Turbulent, Magnetized Simulations

We investigate giant molecular cloud (GMCs) collisions and their ability to induce gravitational instability and thus star formation. This mechanism may be a major driver of star formation activity in galactic disks. We carry out a series of three dimensional, magnetohydrodynamics (MHD), adaptive mesh refinement (AMR) simulations to study how cloud collisions trigger formation of dense filaments and clumps. Heating and cooling functions are implemented based on photo-dissociation region (PDR) models that span the atomic to molecular transition and can return detailed diagnostic information. The clouds are initialized with supersonic turbulence and a range of magnetic field strengths and orientations. Collisions at various velocities and impact parameters are investigated. Comparing and contrasting colliding and non-colliding cases, we characterize morphologies of dense gas, magnetic field structure, cloud kinematic signatures, and cloud dynamics. We present key observational diagnostics of cloud collisions, especially: relative orientations between magnetic fields and density structures, like filaments; $^{13}$CO($J$=2-1), $^{13}$CO($J$=3-2), and $^{12}$CO($J$=8-7) integrated intensity maps and spectra; and cloud virial parameters. We compare these results to observed Galactic clouds.

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