Assembly Of The First Dwarf Galaxies

Understanding the formation and evolution of the first stars and galaxies is crucial to understanding reionization, a key epoch in the history of the Universe. Detailed theoretical studies of the galaxies before and during reionization are now particularly urgent because of the wealth of observational data that will soon be provided by the next generation of telescopes, such as JWST, ALMA, LOFAR, MWA, and others. We simulate the formation of the first galaxies using cosmological smoothed particle hydrodynamics simulations. Zooming in on individual galaxies, we explore how various physical processes affect their assembly and further evolution. A highlight of our study will be the simulation of the radiation-hydrodynamics of galaxy assembly, which we will perform using our multi-frequency radiative transfer method TRAPHIC. Feedback from radiation has long been suspected to play a decisive role in galaxy formation and we will investigate its implications for observable properties of the first galaxies.Astronom

Accuracy analysis of the box-counting algorithm

Accuracy of the box-counting algorithm for numerical computation of the fractal exponents is investigated. To this end several sample mathematical fractal sets are analyzed. It is shown that the standard deviation obtained for the fit of the fractal scaling in the log-log plot strongly underestimates the actual error. The real computational error was found to have power scaling with respect to the number of data points in the sample ($n_{tot}$). For fractals embedded in two-dimensional space the error is larger than for those embedded in one-dimensional space. For fractal functions the error is even larger. Obtained formula can give more realistic estimates for the computed generalized fractal exponents' accuracy.Comment: 3 figure

The First Supernovae: Source Density And Observability Of Pair Instability Supernovae

Theoretical models predict that some of the first stars ended their lives as extremely energetic Pair Instability Supernovae (PISNe). With energies approaching 10(53) erg, these supernovae are expected to be within the detection limits of the upcoming James Webb Space Telescope (JWST) allowing observational constraints to be placed on the properties of the first stars. We estimate the source density of PISNe using a semi-analytic Press-Schecter based approach informed by cosmological simulations, with an upper limit of similar to 0.2 PISNe visible per JWST field of view at any given time. We find that the main obstacle to observing PISNe is their scarcity rather than their faintness. Given this we suggest a mosaic style search strategy for detecting PISNe from the first stars.Astronom

The Source Density And Observability Of Pair-Instability Supernovae From The First Stars

Theoretical models predict that some of the first stars ended their lives as extremely energetic pair-instability supernovae (PISNe). With energies approaching 10(53) erg, these supernovae are expected to be within the detection limits of the upcoming James Webb Space Telescope (JWST), allowing observational constraints to be placed on the properties of the first stars. We estimate the source density of PISNe using a semi-analytic halo mass function based approach, accounting for the effects of feedback from star formation on the PISN rate using cosmological simulations. We estimate an upper limit of similar to 0.2 PISNe per JWST field of view at any given time. Feedback can reduce this rate significantly, e. g., lowering it to as little as one PISN per 4000 JWST fields of view for the most pessimistic explosion models. We also find that the main obstacle to observing PISNe from the first stars is their scarcity, not their faintness; exposures longer than a few times 10(4) s will do little to increase the number of PISNe found. Given this, we suggest a mosaic style search strategy for detecting PISNe from the first stars. Even rather high-redshift PISNe are unlikely to be missed by moderate exposures, and a large number of pointings will be required to ensure a detection.NSF AST-0708795, AST-1009928NASA ATFP NNX09AJ33GAstronom

Liquid crystal hyperbolic metamaterial for wide-angle negative-positive refraction and reflection

We show that nanosphere dispersed liquid crystal (NDLC) metamaterial can be characterized in near IR spectral region as an indefinite medium whose real parts of effective ordinary and extraordinary permittivities are opposite in signs. Based on this fact we design a novel electrooptic effect: external electric field driven switch between normal refraction, negative refraction and reflection of TM incident electromagnetic wave from the boundary vacuum/NDLC. A detailed analysis of its functionality is given based on effective medium theory combined with a study of negative refraction in anisotropic metamaterials, and Finite Elements simulations

Black Hole Feedback On The First Galaxies

We study how the first galaxies were assembled under feedback from the accretion onto a central black hole (BH) that is left behind by the first generation of metal-free stars through self-consistent, cosmological simulations. X-ray radiation from the accretion of gas onto BH remnants of Population III (Pop III) stars, or from high-mass X-ray binaries (HMXBs), again involving Pop III stars, influences the mode of second generation star formation. We track the evolution of the black hole accretion rate and the associated X-ray feedback starting with the death of the Pop III progenitor star inside a minihalo and following the subsequent evolution of the black hole as the minihalo grows to become an atomically cooling galaxy. We find that X-ray photoionization heating from a stellar-mass BH is able to quench further star formation in the host halo at all times before the halo enters the atomic cooling phase. X-ray radiation from a HMXB, assuming a luminosity close to the Eddington value, exerts an even stronger, and more diverse, feedback on star formation. It photoheats the gas inside the host halo, but also promotes the formation of molecular hydrogen and cooling of gas in the intergalactic medium and in nearby minihalos, leading to a net increase in the number of stars formed at early times. Our simulations further show that the radiative feedback from the first BHs may strongly suppress early BH growth, thus constraining models for the formation of supermassive BHs.Astronom

ОЦІНКА ФІНАНСОВОГО СТАНУ РАЙОНІВ СВЄНТОКШИСЬКОГО ВОЄВОДСТВА. (ASSESSMENT OF FINANCIAL CONDITION OF DISTRICTS IN ŚWIĘTOKRZYSKIE PROVINCE).

Одним із найбільш важливих чинників, що визначають розвиток органів місцевого самоврядування, є їхній фінансовий стан, який має беззаперечний вплив на усі види діяльності, які проводяться органами місцевого самоврядування. Це може бути проаналізоване з погляду поточних чи інвестиційних витрат і доходів, а також загальних доходів і витрат. Неспри ятливе фінансове становище може обмежити можливості розвитку органів місцевого самоврядування. Муніципателітети в доброму фінансовому стані більш конкурентоздатні та ефективні у проведенні політики розвитку. (One of the most important determinants of the development of the local government unit is its financial situation, which has an undeniable impact on the whole activities conducted in local government. This can be analyzed both in terms of current or investment expenditure and revenues, as well as incomes and expenses. Inconvenient financial situation may limit the opportunities of the local government development. Municipalities in good financial condition are more competitive and efficient in conducting development policy)

Energy transfer study on Tb3+/Eu3+ Co-activated sol-gel glass-ceramic materials containing MF3 (M = Y, La) nanocrystals for NUV optoelectronic devices

In the present work, the Tb3+/Eu3+ co-activated sol-gel glass-ceramic materials (GCs) containing MF3 (M = Y, La) nanocrystals were fabricated during controlled heat-treatment of silicate xerogels at 350 C. The studies of Tb3+ ! Eu3+ energy transfer process (ET) were performed by excitation and emission spectra along with luminescence decay analysis. The co-activated xerogels and GCs exhibit multicolor emission originated from 4fn–4fn optical transitions of Tb3+ (5D4 !7FJ, J = 6–3) as well as Eu3+ ions (5D0 ! 7FJ, J = 0–4). Based on recorded decay curves, it was found that there is a significant prolongation in luminescence lifetimes of the 5D4 (Tb3+) and the 5D0 (Eu3+) levels after the controlled heat-treatment of xerogels. Moreover, for both types of prepared GCs, an increase in ET e ciency was also observed (from ET 16% for xerogels up to ET = 37.3% for SiO2-YF3 GCs and ET = 60.8% for SiO2-LaF3 GCs). The changes in photoluminescence behavior of rare-earth (RE3+) dopants clearly evidenced their partial segregation inside low-phonon energy fluoride environment. The obtained results suggest that prepared SiO2-MF3:Tb3+, Eu3+ GC materials could be considered for use as optical elements in RGB-lighting optoelectronic devices operating under near-ultraviolet (NUV) excitation