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Gravitational lensing deflects light. A single lens deflector can only shear images, but cannot induce rotations. Multiple lens planes can induce rotations. Such rotations can be observed in quadruply imaged sources, and can be used to distinguish between two proposed solutions of the flux anomaly problem: substructures in lensing galaxies versus large-scale structure. We predict the expected amount of rotation due to large-scale structure in strong lensing systems, and show how this effect can be measured using ∼mas very long baseline interferometry astrometry of quadruple lenses with extended source structures. The magnitude of rotation is around 1°. The biggest theoretical uncertainty is the power spectrum of dark matter on very small scales. This procedure can potentially be turned around to measure the dark matter power spectrum on very small scales. We list the predicted rms rotation angles for several quadruple lenses with known lens and source redshifts. [ABSTRACT FROM AUTHOR]

Interferometers from the ground and space will be able to resolve the two images in a microlensing event. This will at least partially lift the inherent degeneracy between physical parameters in microlensing events. To increase the signal-to-noise ratio, intrinsically bright events with large magnifications will be preferentially selected as targets. These events may be influenced by finite source size effects both photometrically and astrometrically. Using observed finite source size events as examples, we show that the fringe visibility can be affected by ∼5–10 per cent, and the closure phase by a few degrees – readily detectable by ground and space interferometers. Such detections will offer unique information about the lens–source trajectory relative to the baseline of the interferometers. Combined with photometric finite source size effects, interferometry offers a way to measure the angular sizes of the source and the Einstein radius accurately. Limb-darkening changes the visibility by a small amount compared with a source with uniform surface brightness, marginally detectable with ground-based instruments. We discuss the implications of our results for the plans to make interferometric observations of future microlensing events. [ABSTRACT FROM AUTHOR]

We present a systematic search for parallax microlensing events among a total of 512 microlensing candidates in the OGLE II data base for the 1997–1999 seasons. We fit each microlensing candidate with both the standard microlensing model and a parallax model that accounts for the Earth's motion around the Sun. We then search for the parallax signature by comparing the χ[sup 2] of the standard and parallax models. For the events which show a significant improvement, we further use the ‘duration’ of the event and the signal-to-noise ratio as criteria to separate true parallax events from other noisy microlensing events. We have discovered one convincing new candidate, sc33_4505, and seven other marginal cases. The convincing candidate (sc33_4505) is caused by a slow-moving, and likely low-mass, object, similar to other known parallax events. We found that irregular sampling and gaps between observing seasons hamper the recovery of parallax events. We have also searched for long-duration events that do not show parallax signatures. The lack of parallax effects in a microlensing event puts a lower limit on the Einstein radius projected on to the observer plane, which in turn imposes a lower limit on the lens mass divided by the relative lens–source parallax. Most of the constraints are however quite weak. [ABSTRACT FROM AUTHOR]

We test possible lensing scenarios of the JVAS system B2114+022, in which two galaxies at different redshifts (‘G1’ at z[sub 1]=0.3157 and ‘G2’ at z[sub 2]=0.5883) are found within 2 arcsec of quadruple radio sources. For our investigation, we use possible lensing constraints derived from a wealth of data on the radio sources obtained with VLA, MERLIN, VLBA and EVN as well as HST imaging data on the two galaxies, which were presented recently in Augusto et al. In the present study, we focus on reproducing the widest separated, observationally similar radio components A and D as lensed images. We first treat G2 (which is the more distant one from the geometric centre) as a shear term, and then consider two-plane lensing explicitly including G2's potential at the z[sub 2] plane as the first case of two-plane lens modelling. Our modelling results not only support the hypothesis that the system includes gravitationally lensed images of a higher-redshift extragalactic object, but they also show that the explicit inclusion of G2's potential at the second lens plane is necessary in order to fit the data with astrophysically plausible galaxy parameters. Finally, we illustrate a natural consequence of a two-plane lens system, namely the prediction of distortion as well as shift and stretching of G2's isophotes by G1's potential, which can in principle be measured by subtracting out G1's light distribution in an image of high signal-to-noise ratio and good angular resolution, especially a multicolour one. [ABSTRACT FROM AUTHOR]

We investigate how the stellar rotational support changes as a function of spatially resolved stellar population age (⁠|$D_n4000$|⁠) and relative central stellar surface density (⁠|$\Delta \Sigma _1$|⁠) for MaNGA isolated/central disc galaxies. We find that the galaxy rotational support indicator |$\lambda _{R_\mathrm{e}}$| varies smoothly as a function of |$\Delta \Sigma _1$| and |$D_n4000$|⁠. |$D_n4000$| versus |$\Delta \Sigma _1$| follows a 'J-shape', with |$\lambda _{R_\mathrm{e}}$| contributing to the scatters. In this 'J-shaped' pattern rotational support increases with central |$D_n4000$| when |$\Delta \Sigma _1$| is low but decreases with |$\Delta \Sigma _1$| when |$\Delta \Sigma _1$| is high. Restricting attention to low- |$\Delta \Sigma _1$| (i.e. large-radius) galaxies, we suggest that the trend of increasing rotational support with |$D_n4000$| for these objects is produced by a mix of two different processes, a primary trend characterized by growth in |$\lambda _{R_\mathrm{e}}$| along with mass through gas accretion, on top of which disturbance episodes are overlaid, which reduce rotational support and trigger increased star formation. An additional finding is that star-forming galaxies with low |$\Delta \Sigma _1$| have relatively larger radii than galaxies with higher |$\Delta \Sigma _1$| at fixed stellar mass. Assuming that these relative radii rankings are preserved while galaxies are star forming then implies clear evolutionary paths in central |$D_n4000$| versus |$\Delta \Sigma _1$|⁠. The paper closes with comments on the implications that these paths have for the evolution of pseudo-bulges versus classical bulges. The utility of using |$\rm D_n4000$| – |$\Delta \Sigma _1$| to study |$\lambda _{R_\mathrm{e}}$| reinforces the notion that galaxy kinematics correlate both with structure and with stellar-population state, and indicates the importance of a multidimensional description for understanding bulge and galaxy evolution. [ABSTRACT FROM AUTHOR]

ABSTRACT The number density and clustering properties of Lyman-break galaxies (LBGs) are consistent with them being the central galaxies of the most massive dark haloes present at z ∼ 3. This conclusion holds in all currently popular hierarchical models for structure formation, and is almost independent of the global cosmological parameters. We examine whether the sizes, luminosities, kinematics and star formation rates of LBGs are also consistent with this identification. Simple formation models tuned to give good fits to low-redshift galaxies can predict the distribution of these quantities in the LBG population. The LBGs should be small (with typical half-light radii of 0.6--2 h-1kpc), should inhabit haloes of moderately high circular velocity (180--290 km s-1) but have low stellar velocity dispersions (70--120 km s-1) and should have substantial star formation rates (15--100 M⊙ yr-1). The numbers here refer to the predicted median values in the LBG sample of Adelberger et al.; the first number assumes an ω0=1 universe and the second number a flat universe with ω0=0.3. For either cosmology these predictions are consistent with the current (rather limited) observational data. Following the work of Kennicutt, we assume stars to form more rapidly in gas of higher surface density. This predicts that LBG samples should preferentially contain objects with low angular momentum, and therefore small size, for their mass. In contrast, samples of damped Ly α systems (DLSs) should be biased towards objects with large angular momentum. Bright LBGs and DLSs may therefore form distinct populations, with very different sizes and star formation rates, LBGs being smaller and more metal-rich than DLSs of similar mass and redshift. [ABSTRACT FROM AUTHOR]

Using the final Mapping Nearby Galaxies at Apache Point Observatory sample of 10K galaxies, we investigate the dark matter (DM) fraction f DM within one half-light radius R e for about 6K galaxies with good kinematics spanning a wide range of morphologies and stellar velocity dispersion. We employ two techniques to estimate f DM: (i) Jeans anisotropic modelling (JAM), which performs DM decomposition based on stellar kinematics and (ii) comparing the total dynamical mass-to-light ratios (M / L)JAM and (M */ L)SPS from stellar population synthesis (SPS). We find that both methods consistently show a significant trend of increasing f DM with decreasing σe and low f DM at larger σe. For 235 early-type galaxies with the best models, we explore the variation of stellar initial mass function (IMF) by comparing the stellar mass-to-light ratios from JAM and SPS. We confirm that the stellar mass excess factor αIMF increases with σe, consistent with previous studies that reported a transition from Chabrier-like to Salpeter IMF among galaxies. We show that the αIMF trend cannot be driven by M */ L or IMF gradients as it persists when allowing for radial gradients in our model. We find no evidence for the total M / L increasing toward the centre. We detect weak positive correlations between αIMF and age, but no correlations with metallicity. We stack galaxy spectra according to their αIMF to search for differences in IMF-sensitive spectral features (e.g. the |$\rm Na_{\rm I}$| doublet). We only find marginal evidence for such differences, which casts doubt on the validity of one or both methods to measure the IMF. [ABSTRACT FROM AUTHOR]

We try to understand the trends in the mass density slopes as a function of galaxy properties. We use the results from the best Jeans Anisotropic Modelling (JAM) of the integral-field stellar kinematics for near 6000 galaxies from the MaNGA DynPop project, with stellar masses |$10^9\ {\rm {\rm M}_{\odot }}\lesssim M_*\lesssim 10^{12}\ {\rm {\rm M}_{\odot }}$|⁠ , including both early-type and late-type galaxies. We use the mass-weighted density slopes for the stellar |$\overline{\gamma }_*$|⁠ , dark |$\overline{\gamma }_{_{\rm DM}}$| and total |$\overline{\gamma }_{_{\rm T}}$| mass from the MaNGA DynPop project. As previously reported, |$\overline{\gamma }_{_{\rm T}}$| approaches a constant value of |$\overline{\gamma }_{_{\rm T}}\approx 2.2$| for high σe galaxies, and flattens for |$\lg (\sigma _{\rm e}/{\rm km\ s^{-1}})\lesssim 2.3$| galaxies, reaching |$\overline{\gamma }_{_{\rm T}}\approx 1.5$| for |$\lg (\sigma _{\rm e}/{\rm km\ s^{-1}})\approx 1.8$|⁠. We find that total and stellar slopes track each other tightly, with |$\overline{\gamma }_{_{\rm T}}\approx \overline{\gamma }_*-0.174$| over the full σe range. This confirms the dominance of stellar matter within R e. We also show that there is no perfect conspiracy between baryonic and dark matter, as |$\overline{\gamma }_*$| and |$\overline{\gamma }_{_{\rm DM}}$| do not vary inversely within the σe range. We find that the central galaxies from TNG50 and TNG100 simulations do not reproduce the observed galaxy mass distribution, which we attribute to the overestimated dark matter fraction, possibly due to a constant IMF and excessive adiabatic contraction effects in the simulations. Finally, we present the stacked dark matter density profiles and show that they are slightly steeper than the pure dark matter simulation prediction of |$\overline{\gamma }_{_{\rm DM}}\approx 1$|⁠ , suggesting moderate adiabatic contraction in the central region of galaxies. Our work demonstrates the power of stellar dynamics modelling for probing the interaction between stellar and dark matter and testing galaxy formation theories. [ABSTRACT FROM AUTHOR]

Galaxy properties are known to correlate most tightly with the galaxy effective stellar velocity dispersion σe. Here, we look for additional trends at fixed σe using 1339 galaxies (M * ≳ 6 × 109 M⊙) with different morphologies in the MaNGA (DR14) sample with integral-field spectroscopy data. We focus on the gradients (γrms ≡ σ(R e/4)/σe) of the stellar root-mean-square velocity (⁠|$V_{\rm rms} \equiv \sqrt{V^2 + \sigma ^2}$|⁠), which we show traces the total mass density gradient γtot derived from dynamical models and, more weakly, the bulge fraction. We confirm that γrms increases with σe, age, and metallicity. We additionally find that these correlations still exist at fixed σe, where galaxies with larger γrms are found to be older and more metal-rich. It means that mass density gradients contain information of the stellar population which is not fully accounted for by σe. This result puts an extra constraint on our understanding of galaxy quenching. We compare our results with galaxies in the IllustrisTNG hydrodynamical simulations and find that, at fixed σe, similar trends exist with age, the bulge fraction, and the total mass density slope but, unlike observations, no correlation with metallicity can be detected in the simulations. [ABSTRACT FROM AUTHOR]

We undertake the first study of two-planet microlensing models recovered from simulations of microlensing events generated by realistic multiplanet systems in which 292 planetary events, including 16 two-planet events, were detected from 6690 simulated light curves. We find that when two planets are recovered, their parameters are usually close to those of the two planets in the system most responsible for the perturbations. However, in 1 of the 16 examples, the apparent mass of both detected planets was more than doubled by the unmodeled influence of a third, massive planet. This fraction is larger than but statistically consistent with the roughly 1.5% rate of serious mass errors due to unmodeled planetary companions for the 274 cases from the same simulation in which a single planet is recovered. We conjecture that an analogous effect due to unmodeled stellar companions may occur more frequently. For 7 out of 23 cases in which two planets in the system would have been detected separately, only one planet was recovered because the perturbations due to the two planets had similar forms. This is a small fraction (7/274) of all recovered single-planet models, but almost a third of all events that might plausibly have led to two-planet models. Still, in these cases, the recovered planet tends to have parameters similar to one of the two real planets most responsible for the anomaly. [ABSTRACT FROM AUTHOR]

We use Schwarzschild's orbit-superposition technique to construct self-consistent models of the Galactic bar. Using χ2 minimisation, we find that the best-fit Galactic bar model has a pattern speed Ωp=60 km s−1 kpc−1, disk mass Md=1.0×1011M⊙ and bar angle θbar=20° for an adopted bar mass Mbar=2×1010M⊙. The model can reproduce not only the three-dimensional and projected density distributions but also velocity and velocity dispersion data from the BRAVA survey. We also predict the proper motions in the range l=[−12°,12°], b=[−10°,10°], which appear to be higher than observations in the longitudinal direction. The model is stable within a timescale of 0.5 Gyr, but appears to deviate from steady-state on longer timescales. Our model can be further tested by future observations such as those from GAIA. [ABSTRACT FROM PUBLISHER]

The development of modern large-scale spectroscopic survey telescopes responds to the urgent demand for spectral information in astronomical research. Tsinghua University has previously proposed a 6.5 m MUltiplexed Survey Telescope consisting of a Ritchey-Chretien configuration and a 1.8 m multi-element wide-field corrector, achieving excellent performance and world-leading survey efficiency. However, an optimized 1.65 m multi-element corrector with five lenses is proposed to overcome the constraints on glass uniformity and verification in fabrication of the previous corrector design. It maintains outstanding image quality, with the 80% enclosed energy diameter not more than 0.559 arcsec within 3° FoV over up to a 55° zenith angle. The optimized optical system does not revise the working mode of the ADC or the curvature of the primary mirror while ensuring the reasonability and accuracy of manufacturing of large corrector elements. It provides a more feasible reference optical design for the MUltiplexed Survey Telescope in subsequent iterations and communications with manufacturers.