We test the hypothesis that the classical and ultra-faint dwarf spheroidal satellites of the our Galaxy have been the building blocks of the Galactic halo by comparing their [O/Fe] and [Ba/Fe] vs. [Fe/H] patterns with the ones observed in Galactic halo stars. The [O/Fe] ratio deviates substantially from the observed abundance ratios in the Galactic halo stars for [Fe/H] > -2 dex, while they overlap for lower metallicities. On the other hand, for the neutron capture elements, the discrepancy is extended at all the metallicities, suggesting that the majority of stars in the halo are likely to have been formed in situ. We present the results for a model considering the effects of an enriched gas stripped from dwarf satellites on the chemical evolution of the Galactic halo. We find that the resulting chemical abundances of the halo stars depend on the adopted infall time-scale, and the presence of a threshold in the gas for star formation.

Using N-body simulations of the Galactic disks, we qualitatively study how the metallicity distributions of the thick and thin disk stars are modified by radial mixing induced by the bar and spiral arms. We show that radial mixing drives a positive vertical metallicity gradient in the mono-age disk population whose initial scale-height is constant and initial radial metallicity gradient is tight and negative. On the other hand, if the initial disk is flaring, with scale-height increasing with galactocentric radius, radial mixing leads to a negative vertical metallicity gradient, which is consistent with the current observed trend. We also discuss impacts of radial mixing on the metallicity distribution of the thick disk stars. By matching the metallicity distribution of N-body models to the SDSS/APOGEE data, we argue that the progenitor of the Milky Way’s thick disk should not have a steep negative metallicity gradient.

The density distribution of the Milky Way halo is detected with 5351 LAMOST DR3 metal poor K giants using a nonparametric method. The nonparametric fitting method is a model independent way to estimate the halo density distribution while to a large extent avoiding the influence of the halo substucture. We show that the K giants density profile can be fitted well by single power law. We found no indication of a break in the power law index. The powerlaw index n = 5.0−0.64+0.64. The data show that the stellar halo is flattened at smaller radii, and becomes more spherical farther from the Galactic center. The flattening q(r=15Kpc)is about0.64, q(20Kpc) is about 0.8, q(30Kpc) is about 0.96.

This paper presents the thermospheric winds and temperature properties measured with a Fabry-Pérot interferometer (FPI) over Oukaimeden observatory (31.2°N, 7.8°W, 22.8°N magnetic) in Morocco. After Three years of successful functioning from 2014 to 2017, we can address the seasonal behavior of the temperature and the winds (vertical, zonal and meridional). The dependence of the thermospheric winds and temperature on the solar cycle is also presented. The day-to-day variations of the quiet time wind pattern exhibits the importance of other type of waves superposed to the main diurnal tides. The storm time wind and temperature exhibits also a variety of ways to react to the storm. However, there is seasonal effect to the storm that will be illustrated in this paper. The signature of the MTM phenomenon is also present in the winds and temperature in geomagnetically quiet and disturbed nights. The occurrence of this phenomenon over the studied area is also addressed.

We have conducted a large-scale survey of variable stars in the northern Galactic plane, about 320 square degrees using Kiso Wide Field Camera attached to the 105-cm Schmidt telescope at Kiso observatory. In the KISOGP (KWFC Intensive Survey of the Galactic Plane), we collected 40–100 epoch I-band images between 2012 and 2017. In our survey region roughly 5 million stars exist down to the limiting magnitude of ~16.5 mag in I. In the initial data analysis, we detected a couple of thousands of variable stars including approximately 100 Cepheids and more than 700 Miras. More than 80 percents of them were not previously reported as variable stars, indicating that there are still many relatively bright variables to be found in the Galactic plane.

Spacecraft have visited Jupiter and Saturn at all phases of the solar cycle and thus we have a wealth of data with which to explore both upstream parameters and magnetospheric response. In this paper we review upstream parameters including interplanetary magnetic field strength and direction, solar wind dynamic pressure, plasma beta and Mach number. We consider the impact of changing solar wind on dayside coupling via reconnection. We also comment on how solar UV flux variability over a solar cycle influences the plasma and neutral tori in the inner magnetospheres of Jupiter and Saturn, and thus estimate the solar cycle effects on internally driven magnetospheric dynamics. Finally we place our results in the context of the now complete set of data from the Cassini mission at Saturn and the current data streaming in from Juno at Jupiter, outlining future avenues for research.

The globular cluster (GC) system of the Milky Way (MW) provides important information on the MW’s present structure and past evolution. Full 3d motions, accessed through proper motions (PMs), are required to calculate accurate orbits of GCs in the MW halo. We present our HST program to create a PM database for 20 halo GCs. We demonstrate how the observed PMs of individual GCs can be used to study their origins, and we also describe how the PM measurements of our entire targets can be used to constrain the anisotropy profile. Finally, we describe how our PM results can be used for Gaia as an external check, and discuss prospects of PM measurements with HST and Gaia in the coming years.

Narrow-band photometric surveys, such as the Javalambre Photometric Local Universe Survey (J-PLUS), provide not only a means of pre-selection for high-resolution follow-up, but open a new era of precision photometric stellar parameter determination. Using a family of machine learning algorithms known as Artificial Neural Networks (ANNs), we have obtained photometric estimates of effective temperature (Teff) and metallicity ([Fe/H]) across a wide parameter range of temperature and metallicity (4000 < Teff <7000 K; −3.5 <[Fe/H]<0.0) for a number of stars in the J-PLUS Early Data Release. With this methodology, we expect to increase the number of known Carbon-enhanced Metal-poor (CEMP; [C/Fe]>+0.7) stars by several orders of magnitude, as well as constrain the metallicity distribution function of the Milky Way Halo system.

The persistence of the spiral structure in disk galaxies has long been debated. In this work, we investigate the dynamical influence of interstellar gas on the persistence of the spiral arms in disk galaxies. We show that the gas helps the spiral arms to survive for longer time-scale (~ a few Gyr). Also, we show that the addition of gas in calculation is necessary for getting a stable density wave corresponding to the observed pattern speed of the spiral arms.

All recent models of solar magnetic cycle behaviour assume that the Ω-effect stretches an existing poloidal magnetic field into a toroidal field using differential rotation (Featherstone and Miesch 2015). The α-effect recycles the toroidal field back to a poloidal field by convection and rotation and this is repeated throughout the cycle. Computer simulations based on that conceptual model still leave many questions unanswered. It has not resolved where the solar dynamo is located, what it is or what causes the differential rotation which it takes for granted. Does this paradigm need changing? The conceptual model presented here examines the sun in horizontal sections, analyses its internal structure, presents new characterizations for the solar wind and structures found and shows how their interaction creates rotation, differential rotation, the solar dynamo and the magnetic cycle.

The High-Energy Particle Detector (HEPD) will measure electrons, protons and light nuclei fluxes, in low Earth orbit. This detector consists of a high precision silicon tracker, a versatile trigger system, a range-calorimeter and an anti-coincidence system. It is one of the instruments on board the China Seismo-Electromagnetic Satellite (CSES). HEPD can detect multi-MeV particles trapped within the geomagnetic field. When operated at large latitudes HEPD can also detect un-trapped solar particles and low energy cosmic rays. A detailed description of the HEPD will be given.

During the last three decades simulations of the formation of galaxies have made fantastic progress, overcoming problems such as the angular momentum catastrophe and producing galaxies that resemble disk-bulge systems similar to those observed. In this work, I discuss such progress focusing on the formation and evolution of disks in galaxies similar to our Milky Way, and on the effects of different feedback processes that affect galaxies through cosmic time.

I also present the results of simulations that use constrained initial conditions of the Local Group, and discuss environmental effects that might play a role in the formation and evolution of our Galaxy.

High resolution cosmological and hydrodynamical simulations have reached a resolution able to resolve in a self consistent way the disc of our galaxy, the galaxy center and the satellites orbiting around it. We present first results from the NIHAO-UHD project, a set of very high-resolution baryonic zoom-in simulations of Milky Way mass disc galaxies. These simulations model the full cosmological assembly history of the galaxies and their satellite system using the same, well tested physics as the NIHAO project. We show that these simulations can self-consistently reproduce the observed kinematical and morphological features of the X-shaped bulge observed in our own Milky Way.

Hii regions are the sites of massive star formation and are the archetypal tracers of spiral arms. Because of their short lifetimes (<10 Myr) their abundances provide a measure of the nuclear processing of many stellar generations. Here we review our ongoing efforts to explore the metallicity structure of the Galactic disk by observing radio recombination line (RRL) and thermal radio continuum emission toward Hii regions. The RRL-to-continuum ratio provides an accurate measure of the electron temperature which is used as a proxy for metallicity. Since collisionally excited lines from metals (e.g., O, C) are the main coolant in Hii regions, the thermal electron temperature is well correlated with metallicity (e.g., [O/H]). We determine Hii region distances from maser parallax measurements when possible; otherwise we use kinematic distances. Such radio diagnostics of Hii regions yield an extinction free tracer to map the metallicity distribution across the entire Galactic disk.

The Equatorial Electrojet (EEJ) is a narrow band of electrons flowing from east to west at daytime at low latitudes. The electron current produces a magnetic field variation that can be measured at different latitudes. In this work, we have used the data analysis in order to quantify the solar and lunar contributions to those variations and study the morphology of the EEJ current.

The age-metallicity relation (AMR) is a fundamental observational constraint for understanding how the Galactic disc formed and evolved chemically in time. However, there is not yet an agreement on the observational properties of the AMR, primarily due to the difficulty in obtaining accurate ages for individual field stars. We have started an observational campaign for providing new observational input by using wide white dwarf-main sequence (WDMS) binaries. WDs are natural clocks and can be used to derive accurate ages. Metallicities can be obtained from the MS companions. Since the progenitors of WDs and the MS stars were born at the same time, WDMS provide a unique opportunity to constrain in a robust way the properties of the AMR. We present the AMR derived from analysing a pilot sample of 23 WDMS and provide clear evidence for the lack of correlation between age and metallicity at young and intermediate ages.

We present Non-Local Thermodynamic Equilibrium (Non-LTE) abundance corrections for Mg, Ca, and Fe in 12 ultra metal-poor (UMP) stars ([Fe/H] < −4.00). We show that they increase in absolute value toward the lower metallicity up to 0.45 dex for Mg, 0.30 dex for Ca, and 1.00 dex for Fe. This represents a first step toward a full Non-LTE analysis of chemical species in the UMP stars that will enable us to put useful constraints on the properties of the “First” stars.

Metal-poor globular clusters (GCs) show intriguing Al-Mg and Si-Al correlations, which are important clues to decipher the multiple population phenomenon. NGC 5053 is one of the most metal-poor GCs, and has been suggested to be associated with the Sagittarius dwarf galaxy (Sgr), due to its similar location and radial velocity with one of the Sgr arms. In this work, we simulate the orbit of NGC 5053, and argue against the connection between Sgr and NGC 5053. Meanwhile, Mg, Al, and Si spectral lines, which are difficult to detect in the optical spectra, have been detected in the near-infrared APOGEE spectra. We use three different sets of stellar parameters and codes to derive the Mg, Al, and Si abundances, and we always see a large Al variation, and a substantial Si enhancement. Comparing with other metal-poor GCs, we suggest metallicity may not be the only parameter that controls the multiple populations.

We present in this work the development of a solar data assimilation method based on an axisymmetric mean field dynamo model and magnetic surface data. Our mid-term goal is to predict the solar quasi cyclic activity. We focus on the ability of our variational data assimilation algorithm to constrain the deep meridional circulation of the Sun based on solar magnetic observations. Within a given assimilation window, the assimilation procedure minimizes the differences between data and the forecast from the model, by finding an optimal meridional circulation in the convection zone, and an optimal initial magnetic field, via a quasi-Newton algorithm. We demonstrate the capability of the technique to estimate the meridional flow by a closed-loop experiment involving 40 years of synthetic, solar-like data. We show that the method is robust in estimating a (stochastic) time-varying flow fluctuating 30% about the average, and that the horizon of predictability of the method is ~ 1 cycle length.

In this report we present a possible scheme of short-term CME detection forecasting developed on the basis of statistical analysis of solar radio emission regularities prior to “isolated” solar Coronal Mass Ejections registered in 1998, 2003, 2009-2013.