Influence of baryonic physics in galaxy simulations: a semi-analytic treatment of the molecular component

Recent work in galaxy formation has enlightened the important role of baryon physics, to solve the main problems encountered by the standard theory at the galactic scale, such as the galaxy stellar mass functions, or the missing satellites problem. The present work aims at investigating in particular the role of the cold and dense molecular phase, which could play a role of gas reservoir in the outer galaxy discs, with low star formation efficiency. Through TreeSPH simulations, implementing the cooling to low temperatures, and the inclusion of the molecular hydrogen component, several feedback efficiencies are studied, and results on the gas morphology and star formation are obtained. It is shown that molecular hydrogen allows some slow star formation (with gas depletion times of about 5 Gyr) to occur in the outer parts of the discs. This dense and quiescent phase might be a way to store a significant fraction of dark baryons, in a relatively long time-scale, in the complete baryonic cycle, connecting the galaxy discs to hot gaseous haloes and to the cosmic filaments.Comment: Accepted for publication in Astronomy and Astrophysics, 21 pages, 29 figure

Quantifying stellar radial migration in an N-body simulation: blurring, churning, and the outer regions of galaxy discs

Radial stellar migration in galactic discs has received much attention in studies of galactic dynamics and chemical evolution, but remains a dynamical phenomenon that needs to be fully quantified. In this work, using a Tree-SPH simulation of an Sb-type disc galaxy, we quantify the effects of blurring (epicyclic excursions) and churning (change of guiding radius). We quantify migration (either blurring or churning) both in terms of flux (the number of migrators passing at a given radius), and by estimating the population of migrators at a given radius at the end of the simulation compared to non-migrators, but also by giving the distance over which the migration is effective at all radii. We confirm that the corotation of the bar is the main source of migrators by churning in a bar-dominated galaxy, its intensity being directly linked to the episode of a strong bar, in the first 1-3 Gyr of the simulation. We show that within the outer Lindblad resonance (OLR), migration is strongly dominated by churning, while blurring gains progressively more importance towards the outer disc and at later times. Most importantly, we show that the OLR limits the exchange of angular momentum, separating the disc in two distinct parts with minimal or null exchange, except in the transition zone, which is delimited by the position of the OLR at the epoch of the formation of the bar, and at the final epoch. We discuss the consequences of these findings for our understanding of the structure of the Milky Way disc. Because the Sun is situated slightly outside the OLR, we suggest that the solar vicinity may have experienced very limited churning from the inner disc.Comment: Accepted for publication in Astronomy and Astrophysics (acceptance date: 27/04/15), 24 pages, 24 figure

ARCHITECTURE OF DICOTYLEDONOUS WEEDS IN SOME AREAS OF BANYUMAS REGENCY CENTRAL JAVA

B. SUNARNO & F. HALLE. 1986, Arsitektur jenis-jenis gulma dikotil di beberapa daerah Banyumas, Jawa Tengah. Bcriia Biologi 3(4): 146 - 154 Pengamatan lapangan dilakukan untuk mengetahui jenis-jenis gulma dikotil yang pola pertumbuhannya mirip dengan model arsitektur pohon.Hasilnya menunjukkan adanya 14 model pada 180 jenis gulma yang tumbuh di 4 daerah Kecamatandi Kabupaten Banyumas.Model yang paling umum dijumpai adalah model STONE, model LEETJWENBERG dan model ATTIMS.Suku yang dianggap kaya dengan model antara lain Euphorbiaceae (10 jenis).Lamiaceae (14 jenis), Papilionaceae (20 jenis) yang masing-masing memiliki 5 model dan Asteraceae (37 jenis) dengan 4 model.Marga polimorfik dijumpai pada Cassia, Desmodium, dan Lindernia yang masing-masing dengan 3 model dan pada Mimosa. Ocimum, Polygala serta Pluchea masing-masing memiliki 2 model.Dalam penelitian ini tidak diketemukan model arsitektur yang baru

SPATIAL DISTRIBUTION OF DICOTYLEDONOUS WEED ARCHITECTURES IN A SHRUB VEGETATION OF MENGGALA, CENTRAL JAVA

B. SUNARNO & F. HALLE. 1986. Distiibusi spasial model arsitektur gulma dikotil di daerah vegetasi semak, Menggala, Jawa Tengah. Berita Biologi 3(6): 253 - 260. Ketapatan dan frekuensi kehadiran model-model arsitektur gulma dikotil di daerah vegetasi semak Menggala, Jawa Tengah telah dipelajari.Model CHAMPAGNAT yang diwakili oleh Mimosa invisa dan Rubus chrysophyllus merupakan model yang nilai kerapatannya paling tinggi (17,97%) dan merupakan pola pertumbuhan yang umum dijumpai di setiap stratum.Semakin tinggi tingkat stratumnya semakin rendah jumlah model dan jumlah individunya. Perbandingan antara gulma masa mendatang dengan gulma masa kini di daerah semak ini, adalah 3 : 2, menunjukkan a,danya proses suksesi yang sedang berjala

Reaction of Cr+, Mn+, Fe+, Co+, and Ni+ with O2 and N2O. Examination of the translational energy dependence of the cross sections of endothermic reactions

Journal ArticleReactions of Cr+, Mn+, Fe+, Co+, and Ni+ with 02 and N20 to yield metal oxide ions are examined using an ion beam apparatus. Reaction cross sections a as a function of ion translational energy E are reported. With one exception, Fe+ + N20, the cross sections exhibit an energy threshold E0

Reaction of Cr + , Mn + , Fe + , Co + , and Ni + with O2 and N2O. Examination of the translational energy dependence of the cross sections of endothermic reactions

Reactions of Cr + , Mn + , Fe + , Co + , and Ni + with O2 and N2O to yield metal oxide ions are examined using an ion beam apparatus. Reaction cross sections sigma as a function of ion translational energy E are reported. With one exception, Fe + +N2O, the cross sections exhibit an energy threshold Eo. Several models are used to interpret the excitation functions for the O2 reactions and it is concluded that the classical line-of-centers form sigma alpha (1–Eo/E) is most useful. Bond energies derived in this manner are D°(CrO + ) = 3.45±0.1 eV, D°(MnO + ) = 2.48±0.1 eV, D°(FeO + ) = 3.01±0.1 eV, D°(CoO + ) = 2.76±0.1 eV, and D°(NiO + ) = 1.95±0.1 eV. Since these bond energies are all greater than D°(N2–O) = 1.7 eV, the observation of energy thresholds for the reactions with N2O are surprising. These results are explained in terms of a qualitative view of the electronic potential energy surfaces involved

Automata-based Optimization of Interaction Protocols for Scalable Multicore Platforms (Technical Report)

Multicore platforms offer the opportunity for utilizing massively parallel resources. However, programming them is challenging. We need good compilers that optimize commonly occurring synchronization/interaction patterns. To facilitate optimization, a programming language must convey what needs to be done in a form that leaves a considerably large decision space on how to do it for the compiler/run-time system. Reo is a coordination-inspired model of concurrency that allows compositional construction of interaction protocols as declarative specifications. This form of protocol programming specifies only what needs to be done and leaves virtually all how-decisions involved in obtaining a concrete implementation for the compiler and the run-time system to make, thereby maximizing the potential opportunities for optimization. In contrast, the imperative form of protocol specification in conventional concurrent programming languages, generally, restrict implementation choices (and thereby hamper optimization) due to overspecification. In this paper, we use the Constraint Automata semantics of Reo protocols as the formal basis for our optimizations. We optimize a generalization of the producer-consumer pattern, by applying CA transformations and prove the correctness of the transforms

Studies of the Energetics and Mechanisms of Organometallic Reactions in the Gas Phase

An ion beam apparatus is used to study reactions of the three first row group 8 atomic metal ions, Fe+, Co+, and Ni+, as well as the diatomic FeH+ species, with small organic molecules. The kinetic energy dependence of these processes is examined. Analysis of the thresholds for endothermic reactions yields bond strengths of the metal ion to various substituent groups. The thermochemical information derived in this manner and from more qualitative observations is used to assess the mechanisms by which these ions react with small organic molecules. Chapter I provides a brief summary of some of the organometallic systems previously studied using the ion beam apparatus. Chapter II presents the culmination of our studies of reactions of the first row group 8 metal ions with alkanes in which the extensive use of deuterium and 13C-labeled compounds provides further elaboration of the mechanisms by which these ions activate carbon-carbon and carbon-hydrogen bonds. Chapter III examines the consequences of incorporating a carbonyl group into the hydrocarbon from investigations of the reactions of Co+ with aldehydes and ketones. Analysis of products formed at high relative kinetic energies are used in conjunction with thermochemical estimates to infer mechanistic details and construct qualitative reaction coordinate diagrams for the interactions of Co+ with carbonyl compounds. Chapter IV represents an extension of our determinations of metal-carbon bond strengths to include fluorinated substituents. In particular, measurements of the Ni+-CH2 and N+-CF2 bond energies are reported. The implication of these carbene bond strengths for the metathesis of fluorinated olefins is discussed. Chapter V reports the first ion beam experiment of an organometallic fragment, the FeH+ species. Thermochemical information is obtained from reactions involving proton transfer from, and hydride transfer to, FeH+. We find that oxidative addition of FeH+ to D2 or hydrocarbons via Fe(IV) or four-centered intermediates is not a facile process, while reversible insertion of olefins into Fe+-H occurs with moderate cross section at low energies. Preliminary results for the reactions of FeH+ with alcohols, aldehydes, and ethers are also discussed.</p