Central rotations of Milky Way Globular Clusters

Most Milky Way globular clusters (GCs) exhibit measurable flattening, even if on a very low level. Both cluster rotation and tidal fields are thought to cause this flattening. Nevertheless, rotation has only been confirmed in a handful of GCs, based mostly on individual radial velocities at large radii. We are conducting a survey of the central kinematics of Galactic GCs using the new Integral Field Unit instrument VIRUS-W. We detect rotation in all 11 GCs that we have observed so far, rendering it likely that a large majority of the Milky Way GCs rotate. We use published catalogs of the ACS survey of GCs to derive central ellipticities and position angles. We show that in all cases where the central ellipticity permits an accurate measurement of the position angle, those angles are in excellent agreement with the kinematic position angles that we derive from the VIRUS-W velocity fields. We find an unexpected tight correlation between central rotation and outer ellipticity, indicating that rotation drives flattening for the objects in our sample. We also find a tight correlation between central rotation and published values for the central velocity dispersion, most likely due to rotation impacting the old dispersion measurements.Comment: 6 pages, 3 figures; accepted for publication in ApJ Letter

Quantifying the Bayesian Evidence for a Planet in Radial Velocity Data

We present results from a data challenge posed to the radial velocity (RV) community: Namely, to quantify the Bayesian "evidence"for n = {0, 1, 2, 3} planets in a set of synthetically generated RV data sets containing a range of planet signals. Participating teams were provided the same likelihood function and set of priors to use in their analysis. They applied a variety of methods to estimate the marginal likelihood for each n-planet model, including cross-validation, the Laplace approximation, importance sampling, and nested sampling. We found the dispersion in across different methods grew with increasing n-planet models: ∼3 for zero planets, ∼10 for one planet, ∼102-103 for two planets, and >104 for three planets. Most internal estimates of uncertainty in for individual methods significantly underestimated the observed dispersion across all methods. Methods that adopted a Monte Carlo approach by comparing estimates from multiple runs yielded plausible uncertainties. Finally, two classes of numerical algorithms (those based on importance and nested samplers) arrived at similar conclusions regarding the ratio of for n- A nd (n + 1)-planet models. One analytic method (the Laplace approximation) demonstrated comparable performance. We express both optimism and caution: We demonstrate that it is practical to perform rigorous Bayesian model comparison for models of ≤3 planets, yet robust planet discoveries require researchers to better understand the uncertainty in and its connections to model selection.Fil: Nelson, Benjamin E.. Northwestern University; Estados UnidosFil: Ford, Eric B.. Pennsylvania State University; Estados UnidosFil: Buchner, Johannes. Pontificia Universidad Católica de Chile; Chile. Universidad Católica de Chile; ChileFil: Cloutier, Ryan. University of Toronto; CanadáFil: Díaz, Rodrigo Fernando. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Faria, Joaõ P.. Universidad de Porto; PortugalFil: Hara, Nathan C.. Universite Ifm Geneve (ifm); SuizaFil: Rajpaul, Vinesh M.. University of Cambridge; Estados UnidosFil: Rukdee, Surangkhana. Pontificia Universidad Católica de Chile; Chile. Universidad Católica de Chile; Chil

IGRINS Mirror Mount Design for Three Off-Axis Collimators and One Slit-Viewer Fold Mirror

The Korea Astronomy and Space Science Institute and the Department of Astronomy at the University of Texas at Austin are developing a near infrared wide-band high resolution spectrograph, immersion grating infrared spectrometer (IGRINS). The compact white-pupil design of the instrument optics uses seven cryogenic mirrors, including three aspherical off-axis collimators and four flat fold mirrors. In this study, we introduce the optomechanical mount designs of three off-axis collimating mirrors and one flat slit-viewer fold mirror. Two of the off-axis collimators are serving as H and K-band pupil transfer mirrors, and are designed as system alignment compensators in combination with the H2RG focal plane array detectors in each channel. For this reason, the mount designs include tip-tilt and parallel translation adjustment mechanisms to properly perform the precision alignment function. This means that the off-axis mirrors’ optomechanical mount designs are among the most sensitive tasks in all IGRINS system hardware. The other flat fold mirror is designed within its very limitedly allowed work space. This slit-viewer fold mirror is mounted with its own version of the six-point kinematic optics mount. The design work consists of a computer-aided 3D modeling and finite element analysis (FEA) technique to optimize the structural stability and the thermal behavior of the mount models. From the structural and thermal FEA studies, we conclude that the four IGRINS mirror mounts are well designed to meet all optical stability tolerances and system thermal requirements

SVOM-MXT optic and telescope testing at PANTER

The Microchannel X-ray Telescope (MXT) for the Space-based multi-band astronomical Variable Objects Monitor (SVOM), a Franco-Chinese mission (CNES/CNSA), is designed for the soft X-ray range (0.2-10 KeV) to observe gamma-ray bursts (GRBs) from the beginning to the afterglow emission. In the past years, the PANTER test facility has been testing the different MXT optics models. Each optic is made up of an array of 5 x 5 Micro Pore Optic (MPO) plates. We characterized the performance of the SVOM optic at different phases: Bread-Board (BB), Qualification Model (QM), Flight Model (FM), and Flight Spare (FS) for the optic followed by the Performance Model (PM) and Flight Model (FM) for the complete telescope fully integrated with the optic, detector, radiator and electronics. For the FM end-to-end test, in October 2021, the goal was to determine the half-energy width (HEW) on-axis and off-axis, and to characterize the flight telescope's energy-dependent efficiency (effective area) under different thermal loads, i.e. different detector and optics temperatures. The final numbers will be presented in a paper in preparation. This paper provides the overview of various activities: setup, metrology and measurement, carried out at the PANTER facility during the development of the SVOM-MXT towards the end-to-end test

Performance simulations for the ground-based, expanded-beam x-ray source BEaTriX

The BEaTriX (Beam Expander Testing X-ray) facility, being completed at INAF-Brera Astronomical Observatory, will represent an important step in the acceptance roadmap of Silicon Pore Optics mirror modules, and so ensure the final angular resolution of the ATHENA X-ray telescope. Aiming at establishing the final angular resolution that can be reached and the respective fabrication/positioning tolerances, we have been dealing with a set of comprehensive optical simulations. Simulations based on wave optics were carried out to predict the collimation performances of the paraboloidal mirror, including the effect of surface errors obtained from metrology. Full-ray-tracing routines were subsequently employed to simulate the full beamline. Finally, wavefront propagation simulation allowed us assessing the sensitivity and the response of a wavefront sensor that will be utilized for the qualification of the collimated beam. We report the simulation results and the methodologies we adopted