Impacts of Radial Mixing on the Galactic Thick and Thin Disks

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.Comment: 4 pages, 1 figure, to appear in the proceedings of the IAU Symposium 334 "Rediscovering our Galaxy", Potsdam, 10-14 July 2017, eds. C. Chiappini, I. Minchev, E. Starkenburg, M. Valentin

Galaxy Formation from a Low-Spin Density Perturbation in a CDM Universe

In order to understand the formation process of elliptical galaxies which are not rotationally supported, we have carried out numerical simulations of the galaxy formation from the density perturbation with a rotation corresponding to a small spin parameter. The three-dimensional TREE N-Body/SPH simulation code used in this paper includes the dark matter and gas dynamics, radiative cooling, star formation, supernova feedback, and metal enrichment. The initial condition is a slowly rotating, top-hat over-dense sphere on which the perturbations expected in a cold dark matter (CDM) universe are superposed. By means of the stellar population synthesis, we calculated the surface brightness profile, the metallicity distribution, and the photometric properties of the end-product, and found that these properties quantitatively agree with the observed properties of bright elliptical galaxies. Thus, we conclude that, in a CDM universe, the proto-galaxy which has a spin-parameter as small as 0.02 evolves into an elliptical galaxy.Comment: 12 pages, 9 PS figures, 1 GIF figure, accepted for publication in PASJ; PS version available at http://www.astr.tohoku.ac.jp/~kawata/research/papers.htm

Pollution and Environmental Issues in Agriculture and the Livestock Industry: A Brief Review of the Japanese Case

This paper presents an overview of the current conditions of livestock-related environmental problems in Japan. The former Basic Agriculture Act, which was effective between 1961 and 1999, promoted single cropping, the use of chemicals in agricultural methods, and the use of large-sized machines, which caused problems such as soil impoverishment, replant failure, chemical residue accumulation, ground water pollution, and productivity reduction. Many of these livestock-related environmental problems are closely linked to substances in livestock excreta and excessive nitrogen, which is the prime cause of concern. These problems are related to externality and can be attributed to the overuse of natural resources. In addition, the former law ignored the multiple functions of agriculture, which, in turn, diminished the positive external effects. These problems are related to externality and can be attributed to the underuse of natural resources. This condition has been improved under the Food, Agriculture and Rural Areas Basic Act (New Basic Agriculture Act). Superficially, livestock excreta and excessive nitrogen contribute to the overuse problem, but if we regard them as unused resources, they can also be categorised as factors that contribute to the underuse problem. The new act offers measures to resolve underuse problems, but these measures continue to remain inadequate to arrive at a complete solution. Therefore, in addition to the legal approaches adopted, voluntary countermeasures by agriculture and livestock farmers should also be promoted.externality, livestock-related environmental problems, livestock excreta, multiple functions of agriculture, voluntary countermeasures

Does High Unemployment Rate Result in a High Divorce Rate?: A Test for Japan

The purpose of this paper is to examine if the increase in the unemploymentrate has any effect on the divorce rate. We use time series data andcross section data for the whole of Japan in order to examine this assertion.We also include crime rate and average working hours as explanatory variables.We conducted cointegration analysis to avoid spurious correlation for the timeseries data. We apply OLS for the time series and cross section data. The resultssuggest a positive correlation between the unemployment rate and thedivorce rate. We also confirm that the influence of unemployment over divorceis immediate.**El objetivo de este artículo es determinar si el incremento en latasa de desempleo tiene algún efecto sobre la tasa de divorcios. Con este finse utilizan series de tiempo y datos de corte transversal para Japón. Tambiénse incluyen la tasa de crímenes y el promedio de las horas trabajadas comovariables explicativas. Adicionalmente se efectúa análisis de cointegración conel fin de evitar relaciones espúreas entre las series de tiempo. Los resultadossugieren que existe una correlación positiva entre la tasa de desempleo y la tasade divorcios. También confirmamos que existe una relación cronológica cercanaentre el desempleo y el divorcio.unemployment, marital dissolution.**desempleo, divorcio.

Milky Way's Thick and Thin disk: Is there distinct thick disk?

This article is based on our discussion session on Milky Way models at the 592 WE-Heraeus Seminar, Reconstructing the Milky Way's History: Spectroscopic Surveys, Asteroseismology and Chemodynamical models. The discussion focused on the following question: "Are there distinct thick and thin disks?". The answer to this question depends on the definition one adopts for thin and thick disks. The participants of this discussion converged to the idea that there are at least two different types of disks in the Milky Way. However, there are still important open questions on how to best define these two types of disks (chemically, kinematically, geometrically or by age?). The question of what is the origin of the distinct disks remains open. The future Galactic surveys which are highlighted in this conference should help us answering these questions. The almost one-hour debate involving researchers in the field representing different modelling approaches (Galactic models such as TRILEGAL, Besancon and Galaxia, chemical evolution models, extended distribution functions method, chemodynamics in the cosmological context, and self-consistent cosmological simulations) illustrated how important is to have all these parallel approaches. All approaches have their advantages and shortcomings (also discussed), and different approaches are useful to address specific points that might help us answering the more general question above.Comment: 7 pages, no figure. To appear in Astronomische Nachrichten, special issue "Reconstruction the Milky Way's History: Spectroscopic surveys, Asteroseismology and Chemo-dynamical models", Guest Editors C. Chiappini, J. Montalban, and M. Steffe

Analysis of strong-field enhanced ionization of molecules using Bohmian trajectories

We theoretically investigate the mechanism of enhanced ionization in two-electron molecules by analyzing Bohmian trajectories for a one-dimensional H2 in an intense laser field. We identify both types of ionizing trajectories corresponding to the ejection from the up-field and down-field cores. The trajectories of the two electrons are correlated with each other in the former while correlation is negligible in the latter. The contributions from the two ionization types, though depending on laser intensity and internuclear distance, are comparable to each other.Comment: 9 pages, 9 figure

On-the-job search in urban areas

This study develops an on-the-job search model involving spatial structure. In this model, workers are either employed and commuting frequently to a central business district (CBD) or unemployed and commuting less frequently to the CBD to search for a job. When an unemployed worker succeeds in off-the-job search, the quality of the job match is determined stochastically: a good match yields high-productivity whereas a bad match yields low-productivity. Although a high-productivity worker does not search for a new job, a lowproductivity worker decides whether to conduct an on-the-job search, which would require additional commuting to the CBD. Analysis of this model demonstrates that in equilibrium, the relocation path of workers corresponds to their career path, while welfare analysis demonstrates that such a spatial structure distorts firmsf decision regarding the posting of vacancies.City structure; On-the-job search; Unemployment; Efficiency; Relocation and career paths;