Asymmetric Drift Research Articles

Testing screened modified gravity with SDSS-IV-MaNGA

ABSTRACT Fifth forces are ubiquitous in modified gravity theories and must be screened to evade stringent local tests. This can introduce unusual behaviour in galaxy phenomenology by affecting galaxies’ components differently. Here, we use the SDSS-IV (Sloan Digital Sky Survey IV)-MaNGA (Mapping Nearby Galaxies at Apache Point Observatory) data set to search for a systematic excess of gas circular velocity over stellar circular velocity, expected in thin-shell-screened theories in the partially screened regime. Accounting for asymmetric drift and calibrating our model on screened subsamples, we find no significant evidence for a screened fifth force. We bound the fifth-force strength to $\Delta G/G_\text{N} < 0.1$ for all astrophysical ranges, strengthening to $\sim$0.01 at Compton wavelength of 3 Mpc for the Hu–Sawicki model, for instance. This implies a stringent constraint on scalar–tensor theories, for example $f_{\mathcal {R}0} \lesssim 10^{-8}$ in Hu–Sawicki $f(\mathcal {R})$ gravity.

Construction of magnetic and photothermal wood membrane with asymmetric wettabilities and wind drift resistance for solar-driven seawater desalination and purification

To generate clean freshwater controllably and efficiently, Fe3O4/CNT nanomaterials and hydrophobic PVDF were introduced to delignified wood with man-made-cutting structure (D-Wood) in simple brushing method for constructing the magnetic and photothermal wood evaporator with asymmetric wettabilities and wind drift resistance. Such method could endow wood with various shapes design, outstanding magnetically sensitivity, remarkable photothermal conversion efficiency (129.08 %), high evaporation rate (1.92 kg·m−2·h−1), good dye degradability (97.23 %), and excellent wind resistance (6.6 m/s). The superhydrophilic and underwater superoleophobic bottom of Fe3O4/CNT/PVDF@D-Wood evaporator accelerated the bulk seawater transport during its evaporation procedure, but prevented the oil pollutants blocking the microchannels of evaporator during the long periods of flotation at sea. Meantime, its hydrophobic top could effectively reduce the downward diffusion of heat, and improve the salt tolerance. After 10 cycles of acid-base, ultrasound treatments and evaporating experiments, Fe3O4/CNT/PVDF@D-Wood evaporator still exhibited excellent evaporation rate and conversion efficiency, displaying remarkable repeatability and long-term durability. In weak magnetic field (3 V), its furthest response displacement and time were 5 cm and 41 s, respectively. After prolonged evaporation procedure, the magnetic responsivity of Fe3O4/CNT/PVDF@D-Wood evaporator could be in almost constant level, which offers a promising biomass product for seawater desalination and polluted-water purification.

Asymmetric Drift Map of the Milky Way Disk Populations between 8 -16 kpc with LAMOST and Gaia datasets

The application of asymmetric drift (AD) tomography across different populations provides valuable insights into the kinematics, dynamics, and rotation curves of the Galactic disk. By leveraging common stars identified in both the LAMOST and Gaia surveys, alongside Gaia DR3’s circular velocity curve, we conducted a qualitative exploration of asymmetric drift distributions within the Galactic disk spanning distances from 8 to 16 kpc. In the R-Z plane, we observed that the asymmetric drift is minimal near the mid-plane of the Galactic disk and gradually increases with vertical distance, resulting in a distinctive “horn” shape. Additionally, our analysis revealed that populations with higher [ α/Fe] ratios exhibit greater asymmetric drift compared to those with lower [ α/Fe] ratios. Specifically, we found the asymmetric drift around the solar location to be approximately 6 km s −1, with a median value of 16 km s −1 across the entire sample. Notably, the median asymmetric drift in the northern region of the Galactic disk (20 km s −1) surpasses that in the southern region (13 km s −1), with errors remaining within 2 km s −1. Furthermore, our investigation into mono-age stellar populations unveiled that older stellar populations tend to exhibit larger asymmetric drift and velocity dispersion, aligning closely with predictions from previous numerical models. Finally, based on chemical compositions, we observed that the median asymmetric drift of the thick disk significantly exceeds that of the thin disk and found that star formation within the thick disk primarily occurred 8-10 billion years ago, whereas the thin disk’s predominant star formation period spanned 6-8 billion years ago.

Asymmetric drift in MaNGA: mass and radially dependent stratification rates in galaxy discs

ABSTRACT We measure the age–velocity relationship from the lag between ionized gas and stellar tangential speeds in ∼500 nearby disc galaxies from MaNGA in Sloan Digital Sky Survey IV (SDSS-IV). Selected galaxies are kinematically axisymmetric. Velocity lags are asymmetric drift, seen in the Milky Way’s (MW) solar neighbourhood and other Local Group galaxies; their amplitude correlates with stellar population age. The trend is qualitatively consistent in rate ($\dot{\sigma }$) with a simple power-law model where σ ∝ tb that explains the dynamical phase-space stratification in the solar neighbourhood. The model is generalized based on disc dynamical times to other radii and other galaxies. We find in-plane radial stratification parameters σ0,r (dispersion of the youngest populations) in the range of 10–40 km s−1 and 0.2 < br < 0.5 for MaNGA galaxies. Overall, brincreases with galaxy mass, decreases with radius for galaxies above 10.4 dex (M⊙) in stellar mass, but is ∼constant with radius at lower mass. The measurement scatter indicates the stratification model is too simple to capture the complexity seen in the data, unsurprising given the many possible astrophysical processes that may lead to stellar population dynamical stratification. None the less, the data show dynamical stratification is broadly present in the galaxy population, with systematic trends in mass and density. The amplitude of the asymmetric drift signal is larger for the MaNGA sample than the MW, and better represented in the mean by what is observed in the discs of M31 and M33. Either typical discs have higher surface-density or, more likely, are dynamically hotter (hence thicker) than the MW.

Asymmetric post earnings announcement drift and order flow imbalance: The impact on stock market returns

We conduct an event study around the earning announcement to examine the asymmetric post earnings announcement drift, and its relationship with the bid-ask bias, order follow imbalance on post earnings announcement period for UK stock market from 2000 2021. The earning drift is significantly asymmetric in the post earnings announcement period, stocks with good news have less drift, and it (at least) partly due to the order flow imbalance during the event period. The earning announcement attracts more sell than buy orders, and an overall negative reaction in the market. The difference between transaction price return and quote price returns shows that the bid-ask bias is also a possible explanation of post earnings announcement drift. Our results are robust across different estimations and robustness tests.

MeerKAT Pulsar Timing Array parallaxes and proper motions

Abstract We have determined positions, proper motions, and parallaxes of 77 millisecond pulsars (MSPs) from ∼3 years of MeerKAT radio telescope observations. Our timing and noise analyses enable us to measure 35 significant parallaxes (12 of them for the first time) and 69 significant proper motions. Eight pulsars near the ecliptic have an accurate proper motion in ecliptic longitude only. PSR J0955−6150 has a good upper limit on its very small proper motion (<0.4 mas yr−1). We used pulsars with accurate parallaxes to study the MSP velocities. This yields 39 MSP transverse velocities, and combined with MSPs in the literature (excluding those in Globular Clusters) we analyse 66 MSPs in total. We find that MSPs have, on average, much lower velocities than normal pulsars, with a mean transverse velocity of only 78(8) km s−1 (MSPs) compared with 246(21) km s−1 (normal pulsars). We found no statistical differences between the velocity distributions of isolated and binary millisecond pulsars. From Galactocentric cylindrical velocities of the MSPs, we derive 3-D velocity dispersions of σρ, σφ, σz = 63(11), 48(8), 19(3) km s−1. We measure a mean asymmetric drift with amplitude 38(11) km s−1, consistent with expectation for MSPs, given their velocity dispersions and ages. The MSP velocity distribution is consistent with binary evolution models that predict very few MSPs with velocities >300 km s−1 and a mild anticorrelation of transverse velocity with orbital period.

The rotation curve and mass distribution of M31

ABSTRACT To gain a better understanding of the Andromeda galaxy M31 and its role in the Local Group, measuring its mass precisely is essential. In this work, we have constructed the rotation curve of M31 out to ∼125 kpc using 13 679 M31 objects obtained from various sources, including the LAMOST data release 9 (LAMOST DR9), the DESI survey, and relevant literature. We divide all objects in our sample into bulge, disc, and halo components. For the sources in the M31 disc, we have measured their circular velocities by a kinematic model with asymmetric drift corrections. For the bulge and halo objects, we calculate their velocity dispersions and use the spherical and projected Jeans equation to obtain the circular velocities. Our findings indicate a nearly isotropic nature for the M31 bulge, while the halo exhibits tangential anisotropy. The results show that the rotation curve remains constant at ∼220 km s−1 up to radius ∼25 kpc and gradually decreases to ∼170 km s−1 further out. Based on the newly determined rotation curve, we have constructed a mass distribution model for M31. Our measurement of the M31 virial mass is $M_{\rm vir} = 1.14^{+0.51}_{-0.35} \times 10^{12} M_\odot$ within rvir = 220 ± 25 kpc.

Atmospheric highs drive asymmetric sea ice drift during lead opening from Point Barrow

Abstract. Throughout winter, the winds of migrating weather systems drive the recurrent opening of sea ice leads from Alaska's northernmost headland, Point Barrow. As leads extend offshore into the Beaufort and Chukchi seas, they produce sea ice velocity discontinuities that are challenging to represent in models. We investigate how synoptic wind patterns form leads originating from Point Barrow and influence patterns of sea ice drift across the Pacific Arctic. We identify 135 leads from satellite thermal infrared imagery between January–April 2000–2020 and generate an ensemble of lead-opening sequences by averaging atmospheric conditions and ice velocity across events. On average, leads open as migrating atmospheric highs drive differing ice–coast interactions across Point Barrow. Northerly winds compress the Beaufort ice pack against the coast over several days, slowing ice drift. As winds west of Point Barrow shift offshore, the ice cover fractures and a lead extends from the headland into the pack interior. Ice west of the lead accelerates as it separates from the coast, drifting twice as fast (relative to winds) as ice east of the lead, which remains coastally bound. Consequently, sea ice drift and its contribution to climatological ice circulation becomes zonally asymmetric across Point Barrow. These findings highlight how coastal boundaries modify the response of the consolidated ice pack to wind forcing in winter, producing spatially varying regimes of ice stress and kinematics. Observed connections between winds, ice drift, and lead opening provide test cases for sea ice models aiming to capture realistic ice transport during these recurrent deformation events.

A Bayesian estimation of the Milky Way’s circular velocity curve using Gaia DR3

Aims. Our goal is to calculate the circular velocity curve of the Milky Way, along with corresponding uncertainties that quantify various sources of systematic uncertainty in a self-consistent manner. Methods. The observed rotational velocities are described as circular velocities minus the asymmetric drift. The latter is described by the radial axisymmetric Jeans equation. We thus reconstruct the circular velocity curve between Galactocentric distances from 5 kpc to 14 kpc using a Bayesian inference approach. The estimated error bars quantify uncertainties in the Sun’s Galactocentric distance and the spatial-kinematic morphology of the tracer stars. As tracers, we used a sample of roughly 0.6 million stars on the red giant branch stars with six-dimensional phase-space coordinates from Gaia Data Release 3 (DR3). More than 99% of the sample is confined to a quarter of the stellar disc with mean radial, rotational, and vertical velocity dispersions of (35 ± 18) km s−1, (25 ± 13) km s−1, and (19 ± 9) km s−1, respectively. Results. We find a circular velocity curve with a slope of 0.4 ± 0.6 km s−1 kpc−1, which is consistent with a flat curve within the uncertainties. We further estimate a circular velocity at the Sun’s position of vc(R0) = 233 ± 7 km s−1 and that a region in the Sun’s vicinity, characterised by a physical length scale of ∼1 kpc, moves with a bulk motion of VLSR = 7 ± 7 km s−1. Finally, we estimate that the dark matter (DM) mass within 14 kpc is log10 MDM(R < 14kpc)/ M⊙ =(11.2+2.0-2.3) and the local spherically averaged DM density is ρDM(RO)=(0.41+0.10-0.09) GeV cm-3 = (0.011+0.003-0.002) M⊙pc-3. In addition, the effect of biased distance estimates on our results is assessed.

Kelvin–Helmholtz Instability at Mars: In Situ Observations and Kinetic Simulations

Kelvin–Helmholtz (K-H) instability is a fundamental boundary instability between two fluids with different speeds, exchanging the mass, momentum, and energy across the boundary. Although the K-H instability has been suggested to play a critical role in atmospheric ion loss on Mars, the knowledge about its formation and evolution is still poor, due to the limitation of spacecraft missions and a dearth of dedicated simulation codes. In this study, we combine observations from the Mars Atmosphere and Volatile EvolutioN mission and global 3D kinetic simulations to investigate the solar wind–Mars interaction. For the first time, it is found that K-H waves prominently appear in the −E hemisphere, which is attributed to the stronger proton velocity shear therein associated with the asymmetric diamagnetic drift motion of protons. The K-H instability is mainly excited in the −E hemisphere and propagates downstream along the boundary, with the waves also able to be generated near the subsolar point. The K-H waves produce plasma clouds with a net oxygen ion escape rate of about 1.5 × 1024 s−1, contributing to almost half of the global loss on present-day Mars. This heavy ion escape pattern associated with K-H instability is cyclic and could occur on other nonmagnetized planets, potentially influencing planetary atmosphere evolution and habitability.

The SAMI survey: evidence for dynamical coupling of ionized gas and young stellar populations

ABSTRACT We explore local and global dynamical differences between the kinematics of ionized gas and stars in a sample of galaxies from Data Release 3 of the SAMI Galaxy Survey. We find better agreement between local (i.e. comparing on a spaxel-to-spaxel basis) velocities and dispersion of gas and stars in younger systems as with previous work on the asymmetric drift in galaxies, suggesting that the dynamics of stars and ionized gas are initially coupled. The intrinsic scatter around the velocity and dispersion relations increases with increasing stellar age and mass, suggesting that subsequent mechanisms, such as internal processes, divergent star formation, and assembly histories, also play a role in setting and altering the dynamics of galaxies. The global (flux-weighted) dynamical support of older galaxies is hotter than in younger systems. We find that the ionized gas in galaxies is almost always dynamically colder than the stars with a steeper velocity gradient. In absolute terms, the local difference in velocity dispersion is more pronounced than the local difference in velocity, possibly reflecting inherent differences in the impact of turbulence, inflow and/or feedback on gas compared to stars. We suggest how these findings may be taken into account when comparing high and low redshift galaxy samples to infer dynamical evolution.

Residuals of an equilibrium model for the galaxy reveal a state of disequilibrium in the Solar Neighbourhood

ABSTRACTWe simultaneously model the gravitational potential and phase space distribution function (DF) of giant stars near the Sun using the Gaia DR2 radial velocity catalogue. We assume that the Galaxy is in equilibrium and is symmetric about both the spin axis of the disc and the Galactic mid-plane. The potential is taken as a sum of terms that nominally represent contributions from the gas and stellar discs, the bulge, and the dark matter halo. Our model for the DF comprises two components to account for a mix of thin and thick disc stars. Each component is described by an analytic function of the energy, the spin angular momentum, and the vertical energy, in accord with Jeans theorem. We present model predictions for the radial and vertical forces within $\sim 2\, {\rm kpc}$ of the Sun, highlighting the rotation curve, the asymmetric drift curve, and the vertical force profile. We then show residuals for star counts in the R–z and z–vz planes as well as maps of the mean radial and azimuthal velocities in the z–vz plane. Using our model for the potential, we map the star count residuals in action-frequency-angle coordinates. The Gaia phase spiral, velocity arches, bending waves, and some of the known moving groups appear as well-defined features in these maps.

Real and counterfeit cores: how feedback expands haloes and disrupts tracers of inner gravitational potential in dwarf galaxies

ABSTRACT The tension between the diverging density profiles in Lambda cold dark matter simulations and the constant-density inner regions of observed galaxies is a long-standing challenge known as the ‘core–cusp’ problem. We demonstrate that the SMUGGLE galaxy formation model implemented in the arepo moving mesh code forms constant-density cores in idealized dwarf galaxies of M⋆ ≈ 8 × 107 Msun with initially cuspy dark matter (DM) haloes of M200 ≈ 1010 Msun. Identical initial conditions run with an effective equation of state interstellar medium model preserve cuspiness. Literature on the subject has pointed to the low density threshold for star formation, ρth, in such effective models as an obstacle to baryon-induced core formation. Using a SMUGGLE run with equal ρth, we demonstrate that core formation can proceed at low density thresholds, indicating that ρth is insufficient on its own to determine whether a galaxy develops a core. We reaffirm that the ability to resolve a multiphase interstellar medium at sufficiently high densities is a more reliable indicator of core formation than any individual model parameter. In SMUGGLE, core formation is accompanied by large degrees of non-circular motion, with gas rotational velocity profiles that consistently fall below the circular velocity $v_\text{circ} = \sqrt{GM/R}$ out to ∼2 kpc. Asymmetric drift corrections help recover the average underlying DM potential for some of our less efficient feedback runs, but time-variations in the instantaneous azimuthal gas velocity component are substantial, highlighting the need for careful modelling in the inner regions of dwarfs to infer the true distribution of DM.

Domain Adaptation on Asymmetric Drift Data for an Electronic Nose

Domain adaptation, a type of transfer learning, has been theoretically adopted to the electronic nose (EN) drift problem. Current academic achievements in this field are inspired by symmetric data, requiring identical sample categories between source and target domains. Commonly, the source domain comprises prepared EN data with intact ground truth; the target domain contains EN drift data to be recognized without class labels. However, in practical cases, the category number of collected drift data is always less than that of prepared data. Hence, performance degradation would be occurred using traditional domain adaptation. To address this problem, we modified and fused dictionary learning, canonical correlation analysis, and locality preserving projection for the asymmetry domain data. Accordingly, selective first-order, second-order alignments, and topology preservation have been realized via sparse and generalized regulation. Specifically, we presented an associated iterative solution process to gain the projected subspace. Then, we utilized two drift datasets to create several asymmetric EN drift scenarios for performance validation. The experimental results showed the highest recognition accuracies achieved by the proposed method on asymmetric drift data in most scenarios. The proposed methodology was conducted with higher accuracy and stability in drift sample recognition than the other referenced drift compensation methods. It is a suitable choice for EN drift compensation on asymmetric data.

BgRT Motion Management Maintains Target Dose Coverage for Respiratory and Non-Respiratory Motion

<h3>Purpose/Objective(s)</h3> Biology-guided radiotherapy (BgRT) uses outgoing emissions after administration of an injected radiotracer to dynamically guide the delivery of radiation treatment to PET-avid targets. In this study, we evaluated the tracking performance of FDG-guided BGRT for two potential types of motion management (respiratory and non-respiratory (gastrointestinal)) while exploring different target shapes: spherical and non-spherical. BgRT is designed to ensure target coverage while keeping organ-at-risk (OAR) doses low. <h3>Materials/Methods</h3> A large custom anthropomorphic phantom with 2 robotic articulating arms was used to place a target and organ-at-risk inside a 27-liter water filled cavity. The targets consisted of an integrated ion chamber inside a 3D printed 22 mm sphere or a small non-spherical ovoid shape filled with FDG. The hot FDG-filled OAR consisted of either a 3D printed large C-shape annulus (mimicking a heart), large ovoid (mimicking a kidney), or a 30 mm sphere, all with integrated ion chambers. Both the 3D printed target and the OAR were filled with an 8:1 concentration ratio versus the water background. Three different 10 Gy/fraction treatment plans with two different target shapes and realistic nearby OARs were created with a 5 mm margin added to the CTV to generate the PTV. 3D printed targets and OARs were loaded with EBT-XD radiographic film. A 3D elliptical motion trajectory with breathing induced hysteresis with a maximum amplitude of +/- 12 mm was used for the respiratory motion model. An asymmetric slow-moving drift waveform with long-step shifts of +13/-5mm mm was used for the non-respiratory (gastrointestinal) motion model. Dosimetric results were evaluated based on 2-dimensional comparisons between measured film and planned dose distributions for the target and OAR. BgRT must maintain a prescription dose margin greater than 2 mm on the CTV for the three different motion experiments. Also, ion-chamber point dose and maximum film dose on the OAR must be within bounds predicted by the treatment planning system. <h3>Results</h3> BgRT was able to meet minimum margin requirements (a margin loss < 3mm) and meet prescription dose coverage in both motion management scenarios while maintaining OAR dose limits within the plan predicted bounds (see Table 1). <h3>Conclusion</h3> BgRT is able to provide motion management in complex cases that is agnostic to the type of motion. BgRT is able to maintain the PTV coverage with less than 3 mm reduction from the original 5mm margin.

Scaling relations ofz∼ 0.25–1.5 galaxies in various environments from the morpho-kinematics analysis of the MAGIC sample

Context.The evolution of galaxies is influenced by many physical processes, which may vary depending on their environment.Aims.We combineHubbleSpace Telescope (HST) and Multi-Unit Spectroscopic Explorer (MUSE) data of galaxies at 0.25 ≲ z ≲ 1.5 to probe the impact of environment on the size-mass relation, the main sequence (MS) relation, and the Tully-Fisher relation (TFR).Methods.We perform a morpho-kinematics modelling of 593 [O II] emitters in various environments in the COSMOS area from the MUSE-gAlaxy Groups In Cosmos survey. The HST F814W images are modelled with a bulge-disk decomposition to estimate their bulge-disk ratio, effective radius, and disk inclination. We use the [O II]λλ3727, 3729 doublet to extract the galaxies’ ionised gas kinematics maps from the MUSE cubes, and we model those maps for a sample of 146 [O II] emitters, including bulge and disk components constrained from morphology and a dark matter halo.Results.We find an offset of 0.03 dex (1σsignificant) on the size-mass relation zero point between the field and the large structure sub-samples, with a richness threshold ofN = 10 to separate between small and large structures, and of 0.06 dex (2σ) withN = 20. Similarly, we find a 0.1 dex (2σ) difference on the MS relation withN = 10 and 0.15 dex (3σ) withN = 20. These results suggest that galaxies in massive structures are smaller by 14% and have star formation rates reduced by a factor of 1.3 − 1.5 with respect to field galaxies atz ≈ 0.7. Finally, we do not find any impact of the environment on the TFR, except when usingN = 20 with an offset of 0.04 dex (1σ). We discard the effect of quenching for the largest structures, which would lead to an offset in the opposite direction. We find that, atz ≈ 0.7, if quenching impacts the mass budget of galaxies in structures, these galaxies would have been affected quite recently and for roughly 0.7 − 1.5 Gyr. This result holds when including the gas mass but vanishes once we include the asymmetric drift correction.

A slow bar in the lenticular barred galaxy NGC 4277

Aims.We characterised the properties of the bar hosted in lenticular galaxy NGC 4277, which is located behind the Virgo cluster.Methods.We measured the bar length and strength from the surface photometry obtained from the broad-band imaging of the Sloan Digital Sky Survey and we derived the bar pattern speed from the stellar kinematics obtained from the integral-field spectroscopy performed with the Multi Unit Spectroscopic Explorer at the Very Large Telescope. We also estimated the co-rotation radius from the circular velocity, which we constrained by correcting the stellar streaming motions for asymmetric drift, and we finally derived the bar rotation rate.Results.We found that NGC 4277 hosts a short (Rbar = 3.2−0.6+0.9kpc), weak (Sbar = 0.21 ± 0.02), and slow (ℛ = 1.8−0.3+0.5) bar and its pattern speed (Ωbar = 24.7 ± 3.4 km s−1kpc−1) is amongst the best-constrained ones ever obtained with the Tremaine–Weinberg (TW) method with relative statistical errors of ∼0.2.Conclusions.NGC 4277 is the first clear-cut case of a galaxy hosting a slow stellar bar (ℛ &gt; 1.4 at more than a 1σconfidence level) measured with the model-independent TW method. A possible interaction with the neighbour galaxy NGC 4273 could have triggered the formation of such a slow bar and/or the bar could be slowed down due to the dynamical friction with a significant amount of dark matter within the bar region.

The VMC survey – XLVI. Stellar proper motions in the centre of the Large Magellanic Cloud

ABSTRACT We present proper motion (PM) measurements within the central region of the Large Magellanic Cloud (LMC), using near-infrared data from the VISTA survey of the Magellanic Cloud system (VMC). This work encompasses 18 VMC tiles covering a total sky area of ∼28 deg2. We computed absolute stellar PMs from multiepoch observations in the Ks filter over time baselines between ∼12 and 47 months. Our final catalogue contains ∼6322 000 likely LMC member stars with derived PMs. We employed a simple flat-rotating disc model to analyse and interpret the PM data. We found a stellar centre of rotation ($\alpha _{0} = 79.95^{\circ }\,^{+0.22}_{-0.23}$, $\delta _0 = -69.31^{\circ }\,^{+0.12}_{-0.11}$) that is in agreement with that resulting from Hubble Space Telescope data. The inferred viewing angles of the LMC disc ($i=33.5^{\circ }\,^{+1.2}_{-1.3}$, $\Theta =129.8^{\circ }\,^{+1.9}_{-1.9}$) are in good agreement with values from the literature but suggest a higher inclination of the central parts of the LMC. Our data confirm a higher rotation amplitude for the young (≲0.5 Gyr) stars compared to the intermediate-age/old (≳1 Gyr) population, which can be explained by asymmetric drift. We constructed spatially resolved velocity maps of the intermediate-age/old and young populations. Intermediate-age/old stars follow elongated orbits parallel to the bar’s major axis, providing first observational evidence for x1 orbits within the LMC bar. In the innermost regions, the motions show more chaotic structures. Young stars show motions along a central filamentary bar structure.

LEGA-C: Analysis of Dynamical Masses from Ionized Gas and Stellar Kinematics at z ∼ 0.8

Abstract We compare dynamical mass estimates based on spatially extended stellar and ionized gas kinematics (M dyn,* and M dyn,eml, respectively) of 157 star-forming galaxies at 0.6 ≤ z &lt; 1. Compared with z ∼ 0, these galaxies have enhanced star formation rates, with stellar feedback likely affecting the dynamics of the gas. We use LEGA-C DR3, the highest-redshift data set that provides sufficiently deep measurements of a K s -band limited sample. For M dyn,*, we use Jeans anisotropic multi-Gaussian expansion models. For M dyn,eml, we first fit a custom model of a rotating exponential disk with uniform dispersion, whose light is projected through a slit and corrected for beam smearing. We then apply an asymmetric drift correction based on assumptions common in the literature to the fitted kinematic components to obtain the circular velocity, assuming hydrostatic equilibrium. Within the half-light radius, M dyn,eml is on average lower than M dyn,*, with a mean offset of –0.15 ± 0.016 dex and galaxy-to-galaxy scatter of 0.19 dex, reflecting the combined random uncertainty. While data of higher spatial resolution are needed to understand this small offset, it supports the assumption that the galaxy-wide ionized gas kinematics do not predominantly originate from disruptive events such as star formation–driven outflows. However, a similar agreement can be obtained without modeling from the integrated emission line dispersions for axis ratios q &lt; 0.8. This suggests that our current understanding of gas kinematics is not sufficient to efficiently apply asymmetric drift corrections to improve dynamical mass estimates compared with observations lacking the signal-to-noise ratio required for spatially extended dynamics.

Can deepwater bottom currents generate clinothems? An example of a large, asymmetric mounded drift in Upper Jurassic to Lower Cretaceous sediments from northwestern Australia

Abstract Clinoforms and clinothems are ubiquitous in shallow marine and shelf margin environments, where they show remarkable seaward progradation trends. Consensus holds that these features do not form in deepwater settings. This study describes an example of a large, asymmetric mounded deposit formed in Upper Jurassic to Lower Cretaceous sediments along the Exmouth Plateau (offshore northwestern Australia). Although it formed in deepwater environments, the deposit has previously been interpreted to reflect either a deltaic or shelf margin system based on clinoform and clinothem geometries. We support that this deposit shares similarities with a delta drift that evolved into a large, mounded drift (~180 km in length, ~120 km in width, and up to ~1.7 km in sedimentary thickness) that exhibits two migration trends: one westward and the other northeastward. Three evolutionary phases are proposed: (1) an onset drift stage (ca. 146.5–143.5 Ma); (2) a growth drift stage (ca. 143.5–138.2 Ma); and (3) a burial stage (ca. 138.2 Ma), which marks the completion of the drift and a shift in depositional style. The drift asymmetry and clinoform orientations indicate the influence of a northward-flowing water mass with two main cores. Our analysis thus suggests that bottom currents can create complex deposits with geometries that resemble clinothems in deepwater environments.