1804.08907
Exoplanets: past, present, and future
Lee
Our understanding of extra-solar planet systems is highly driven by advances in observations in the past decade. Thanks to high precision spectrograph, we are able to reveal unseen companions to stars with the radial velocity method. High precision photometry from the space, especially with the Kepler mission, enables us to detect planets when they transit their stars and dim the stellar light by merely one percent or smaller. Ultra wide-field, high cadence, continuous monitoring of the Galactic bulge from different sites around the southern hemisphere provides us the opportunity to observe microlensing effects caused by planetary systems from the solar neighborhood, al the way to the Milky Way center. The exquisite AO imaging from ground-based large telescopes, coupled with high-contrast coronagraph, captured the photons directly emitted by planets around other stars. In this article, Present a concise review of the extra-solar planet discoveries, discussion the strengths and weaknesses of the major planetary detection methods, providing an overview of the current understanding of planetary formation and evolution given the tremendous observations delivered by various methods, as well as on-going and planned observation endeavors to provide a clear picture of extra-solar planetary systems.
1804.07049
A predicted astrometric microlensing event by a nearby white dwarf
McGill, et al
Use the Tyco-Gaia Astrometric Solution catalogue, large of Gaia DR1, to search for candidate astrometric microlensing events expected to occur within the remaining lifetime of the Gaia satellite. The search yielded one promising candidate. Predict that the nearby DQ type WD LAWD 37 (WD 1142-645) will lens a background star and will reach closest approach on Nov. 11 2018 (±4 days) with impact parameter 380±10 mas. This will produce an apparent maximum deviation of the source position of 2.8 ±0.1 mas. In the most propitious circumstance, Gaia will be able to determine the mass of LAWD 37 to ~3%. This mass determination will provide an independent check on atmospheric models of white dwarfs with He rich atmospheres, as well as tests of WD mass radius relationships and evolutionary theory.
1804.07401
A new approach to uncovering substructure: proof of concept using Abell 2744
Schwinn, et al
A recent comparison of the massive galaxy cluster Abell 2744 with the Millennium XXL (MXXL) N-body sims has hinted at a tension between the observed substructure distribution and the predictions of LCDM. Follow-up investigations indicated that this could be due to the contribution from the host halo and the sub halo finding algorithm used. To be independent of any sub halo finding algorithm, investigate the particle data of the MXXL sim directly. Propose a new method to find substructures in 2D mass maps using a wavelet transform, which treats the sim and observations equally. Using the same criteria to define a sub halo in observations and simulated data, find 3 Abell 2744 analogues in the MXXL sim. Thus the observations in Abell 2744 are in agreement with the predictions of LCDM. Investigate the reasons for the discrepancy between the results obtained from the SUBFIND and full particle data analyses. Find that this is due to incompatible substructure definitions in observations and SUBFIND.
1804.09381
Gaia Data Release 2: Kinematics of globular clusters and dwarf galaxies around the Milky Way
Gaia Collaboration, et al
The goal of this paper is to demonstrate the outstanding quality of the second data release of the Gaia mission and its power for constraining many different aspects of the dynamics of the satellites of the Milky Way. Focus here on determining the proper motions of 75 Galactic globular clusters, non dwarf spheroidal galaxies, one ultra-faint system, and the Large and Small Magellanic Clouds. Using data extracted from the Gaia archive, derive the proper motions and parallaxes for these systems, as well as their uncertainties. Demonstrate that the errors, statistical and systematic, are relatively well understood. Integrate the orbits of these objects in 3 different Galactic potentials, and characterize their properties. Present the derived proper motions, space velocities, and characteristic orbital parameters in various tables to facilitate their use by the astronomical community. The limited and straightforward analyses have allowed, for example, to (i) determine absolute and very precise proper motions for globular clusters; (ii) detect clear rotation signatures in the proper motions of at least 5 globular clusters; (iii) show that the satellites of the MW are all on high-inclination orbits, but that they do not share a single plane of motions; (iv) derive a lower limit for the mass of the Milky Way of 9.8+6.7-2.7e11 Msun based on the assumption that the Leo I dwarf spheroidal is bound; (v) derive a rotation curve for the LMC based solely on proper motions that is competitive with LoS velocity curves, now using many orders of magnitude more sources; and (vi) unveil the dynamical effect of the bar on the motions of stars in the LMC. All these results highlight the incredible power of the Gaia astrometric mission, and in particular of its second data release.
1804.10199
Halo profiles and the concentration-mass relation for a {\Lambda}CDM Universe
Child, Habib, Heitmann, et al
Profiles of DM-dominated haloes at the group and cluster scales play an important role in modern cosmology. Using results from 2 very large cosmo N-body sims, which increase the available volume at their mass resolution by roughly 2 orders of magnitude, robustly determine the halo concentration-mass (c-M) relation over a wide range of masses employing multiple methods of concentration measurement. Characterize individual halo profiles as well as stacked profiles relevant for gg lensing and next-generation cluster surveys; the redshift range covered is 0<=z<=4, with a minimum halo mass of M_200c~2e11 Msun. Despite the complexity of a proper description of a halo (environmental effects, merger history, non sphericity, relaxation state), when the mass is scaled by the nonlinear mass scale M_*(z), find that a simple non-power law form for the c-M/M_* relation provides an excellent description of the simulation results across 8 decades in M/M_* and for 0<=z<=4. Over the mass range covered, the c-M relation has 2 asymptotic forms: an approximate power law below a mass threshold M/M_*~500-1000, transitioning to a constant value, c_0~3 at higher masses. The relaxed halo fraction decreases with mass, transitioning to a constant value of ~0.5 above the same mass threshold. Compare NFW and Einasto fits to stacked profiles in narrow mass bins at different redshift; expectedly, the Einasto profile provides a better description of the simulation results. At cluster scales at low z, however, both NFW and Einasto profiles are in very good agreement with the sim results, consistent with recent WL observations.
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