We report the results of performance evaluation of the first Japanese astrometry satellite, Nano-JASMINE. It is a very small satellite and weighs only 35 kg. It aims to carry out astrometry measurement of nearby bright stars (z ≤ 7.5 mag) with an accuracy of 3 milli-arcseconds. Nano-JASMINE will be launched by Cyclone-4 rocket in August 2011 from Brazil. The current status is in the process of evaluating the performances. A series of performance tests and numerical analysis were conducted. As a result, the engineering model (EM) of the telescope was measured to be achieving a diffraction-limited performance and confirmed that it has enough performance for scientific astrometry.

We present a Bayesian method that simultaneously takes all available observables for a given star, their uncertainties and prior knowledge like the initial mass function into account to determine probability distributions of the stellar parameters based on grids of stellar evolutionary models. This allows to homogeneously analyse stars, to determine stellar parameters including robust uncertainties and to identify stars that cannot be reproduced by current stellar models. Our code is available through an easy-to-use web-interface.

The cooling of baryons in the centers of dark matter halos leads to a more concentrated dark matter distribution. This effect has traditionally been calculated using the model of adiabatic contraction, which assumes spherical symmetry, while in hierarchical formation scenarios halos grow via multiple violent mergers. We test the adiabatic contraction model in high-resolution cosmological simulations and find that the dissipation of gas indeed increases the density of dark matter and steepens its radial profile compared to the case without cooling. Although the standard model systematically overpredicts the increase of dark matter density, a simple modification of the assumed invariant from M(r)r to $M(\bar{r})r$, where $\bar{r}$ is the orbit-averaged particle position, reproduces the simulated profiles within 10%.

In the last years, some issues concerning Cepheids have beenresolved, based on observations and modeling. However, as usual, newdifficulties arise. The link between the dynamical structure ofCepheid atmosphere and the distance scale calibration in theuniverse is now clearly established. To support observations, wecurrently need fully consistent hydrodynamical models, includingpulsating and evolutionary theories, convective energy transport,adaptive numerical meshes, and a refined calculation of theradiative transfer within the pulsating atmosphere, and also in theexpected circumstellar envelope (hereafter CSE). Confronting suchmodels with observations (spectral line profiles, spatial- andspectral- visibility curves), will permit to resolve and/orstrengthen subtle questions concerning (1) the limb-darkening, (2)the dynamical structure of Cepheids' atmosphere, (3) the expectedinteraction between the atmosphere and the CSE, and (4) it willbring new insights in determining the fundamental parameters ofCepheids. All these physical quantities are supposed furthermore tobe linked to the pulsation period of Cepheids. From these studies,it will be possible to paint a glowing picture of all Cepheidswithin the instability strip, allowing an unprecedent calibration ofthe period-luminosity relation (hereafter PL relation),leading to new insights in the fields of extragalactic distancescales and cosmology.

The detailed abundance patterns in extremely metal-poor (EMP) stars are examined, using the results of the First Stars ESO-VLT Large Program on large samples of dwarfs (located close to the main sequence turnoff) and giant stars (Cayrel et al. 2004; Bonifacio et al. 2007 and subsequent papers). Abundances measured in giants are compared to those measured in turnoff stars, and to comparable quality data in the literature, to demonstrate that the systematics involved in most abundance ratios are very small. A few exceptions are discussed: a reanalysis of Na and Al in EMP samples is performed using NLTE computations. In addition, giants with luminosities brighter than the RGB bump are shown to exhibit the sign of surface pollution by mixing of the products of H-burning, affecting the measured abundances of C, N and Li. 
The implications of a few key abundance ratios (among those considered to be robust and representative of the early galactic gas) are examined in terms of the early Milky-Way enrichment processes and the possible nucleosynthesis contributors (PISNs, SNII, hypernovae). The very low dispersion found around the mean trends is also discussed in terms of chemical enrichment processes.

In low-mass disks, turbulent torques are probably the most importantway of redistributing angular momentum. Here we present the theory ofturbulent accretion disks. We show the molecular viscosity is far toosmall to account for the evolutionary timescale of disks, and wedescribe how turbulence may result in enhanced transport of (angular)momentum. We then turn to the magnetorotational instability, whichthus far is the only mechanism that has been shown to initiate andsustain turbulence in disks. Finally, we present both the basis andthe structure of α disk models.

A possible method of pupil apodization using Zernike's phase contrastis presented. I recall the phase contrast principle and show through numericalsimulations that it may be used to generate an apodization using very simpleoptics in the monochromatic case. I also demonstrate that the generalformalism for Lyot and Roddier & Roddier coronagraphy can be extended to theZernike case. This may improve the quality of the simulations undertakento demonstrate the technique's performances.

We use the combination of the very large Millennium and Millennium-II simulations to follow galaxy formation over a stellar mass range of more than five orders of magnitude throughout representative cosmological volumes. These are the first simulations to address the abundance and spatial distribution of galaxies ranging from cD’s down to dSph’s. We demonstrate that stronger feedback is needed than in previous models, epically at low mass, if the SDSS stellar mass function is to be matched in a LCDM universe. Models which satisfy this constraint also reproduce the observed abundance of faint dwarfs around the Milky Way and M 31. Only the very faintest objects are significantly affected by the treatment of reionisation. Our model can reproduce most galaxy properties in the local Universe. Problems remain with respect to the stellar age distributions and kinematics of dwarfs.

The mechanisms of nucleation and growth of carbon dust particles in circumstellarenvelopes of carbon-rich stars in the red giant and AGB phases of their evolution arepoorly understood. It has been proposed that the transition of gas phase species to solidparticles,is achieved by the formation of a critical nucleus composed of two PAHs heldtogether by van der Waals forces. Some insights into the validity of the nucleation of PAHmolecules in the envelope can be gained through the investigation of the thermodynamics ofdimers,representing the first stage towards condensation. We have performed experimentsto identify the temperature range over which small PAH clusters form in saturated uniformsupersonic flows. The kinetics of the formation has also been investigated. Theexperimental data have been combined with theoretical calculations. We unambiguouslydemonstrate that the association of small PAHs such as pyrene(C16H10) is slower than the destruction of the dimer in warm andhot environments such as IRC +10216. Our findings challenge a formation model based on thephysical stacking of small PAH units in circumstellar shells of carbon rich stars.

Infrared spectroscopy in the mid- and far-infrared provides powerful diagnostics for studying the emission regions in active galaxies. The large variety of ionic fine structure lines can probe gas conditions in a variety of physical conditions, from highly ionized gas excited by photons originated by black hole accretion to gas photoionized by young stellar systems. The critical density and the ionization potential of these transitions allow to fully cover the density-ionization parameter space. Some examples of line ratios diagrams using both mid-infrared and far-infrared ionic fine structure lines are presented. The upcoming space observatory Herschel will be able to observe the far-infrared spectra of large samples of local active galaxies. Based on the observed near-to-far infrared emission line spectrum of the template galaxy NGC 1068, are presented the predictions for the line fluxes expected for galaxies at high redshift. To observe spectroscopically large samples of distant galaxies, we will have to wait for the future space missions, like SPICA and, ultimately, FIRI.

We introduce a new model of gamma ray burst (GRB) that explains its observed promptsignals, namely, its primary quasi-thermal spectrum and high energy tail. This mechanismcan be applied to either assumption of GRB progenitor: coalescence of compact objects orhypernova explosion. The key ingredients of our model are: (1) The initial stage of a GRBis in the form of a relativistic quark-gluon plasma lava; (2) The expansion and cooling ofthis lava results in a QCD phase transition that induces a sudden gravitational stoppageof the condensed non-relativistic baryons and form a hadrosphere; (3) Acoustic shocks andAlfven waves (magnetoquakes) that erupt in episodes from the epicenter efficientlytransport the thermal energy to the hadrospheric surface and induce a rapid detachment ofleptons and photons from the hadrons; (4) The detachede + e −  and γform an opaque, relativistically hot leptosphere, which expands and cools toT ~ mc2, or 0.5 MeV,wheree + e −  → 2γand its reverse process becomes unbalanced, and the GRB photons are finally released; (5)The mode-conversion of Alfven waves into electromagnetic waves in the leptosphere providesa snowplow acceleration and deceleration that gives rise to both the high energy spectrumof GRB and the erosion of its thermal spectrum down to a quasi-thermal distribution.According to this model, the observed GRB photons should have a redshifted peak frequencyatEp ~ Γ(1 + β/2)mc2/(1 + z),where Γ ~ O(1) is the Lorentz factor of the bulk flow of the lava,which may be determined from the existing GRB data.

bonnfires, a new generation of population synthesis code, can calculate nuclear reaction, various mixing processes and binary interaction in a timely fashion. We use this new population synthesis code to study the interplay between binary mass transfer and rotation. We aim to compare theoretical models with observations, in particular the surface nitrogen abundance and rotational velocity. Preliminary results show binary interactions may explain the formation of nitrogen-rich slow rotators and nitrogen-poor fast rotators, but more work needs to be done to estimate whether the observed frequencies of those stars can be matched.

Chemical abundances and radial velocities for ∼210 stars in WLM, ∼130 new stars from DEIMOS spectroscopy, and 80 stars from Leaman et al. (2009) are presented. This sample shows that this isolated dwarf has chemically, dynamically, and spatially distinct stellar populations similar to the nearby dwarf spheroidals. The kinematics of the stars appear to be decoupled from the HI gas, which shows a higher rotational velocity profile. This thicker stellar configuration for a distant, isolated dwarf irregular may have implications for timescales of tidal transformation scenarios of infalling galaxies in the Local Group.

Recent observations of UGC 4879 with the Advanced Camera for Surveys on the Hubble Space Telescope confirm that it is a nearby isolated dwarf irregular galaxy. We measure a distance of 1.36 ± 0.03 Mpc using the Tip of the Red Giant Branch method. This distance puts UGC 4879 beyond the radius of first turnaround of the Local Group and ~700 kpc from its nearest neighbor Leo A. This isolation makes this galaxy an ideal laboratory for studying pristine star formation uncomplicated by interactions with other galaxies. We present the star formation history of UGC 4879 derived from simulated color-magnitude diagrams.

BOOTES-1B and BOOTES-2 were first to follow-up the Swift GRB 080605.Observations started 44 s after the GRB trigger, discovering the optical afterglow withthe brightness of R = 14.7. A power-law decay with anα = 1.27 ± 0.04 was observed during the first ~600 s after thetrigger.

We model the cosmic medium as the mixture of a generalized Chaplygin gas and a pressureless matter component. Within a neo-Newtonian approach we compute the matter power spectrum. The 2dFGRS data are used to discriminate between unified models of the dark sector and different models, for which there is separate dark matter, in addition to that accounted for by the generalized Chaplygin gas. Leaving the corresponding density parameters free, we find that the unified models are strongly disfavored. On the other hand, using unified model priors, the observational data are also well described, in particular for small and large values of the generalized Chaplygin gas parameter α.

Hydrogenated amorphous carbons (HACs) are considered as laboratory analogues to cosmic carbonaceous nanoparticles in the interstellar medium (ISM). The optical properties of nano-sized HACs may be influenced by the UV processing. The variation of the internal structure leads to dramatic changes in the spectral properties in the FUV-VIS range. This scenario can explain some astronomical features such as the interstellar UV bump at 4.6 μm-1. The spectrum of HACs, irradiated by a dose of UV irradiation that corresponds to 21–33% of the average dose of the UV radiation in diffuse ISM, exhibits a new band centered at 4.6 μm-1. This result confirms, for the first time, the suggestion by Mennella et al. (1996) that irradiated HACs might be considered as the carriers of the interstellar UV bump at 4.6 μm-1. However, the amount of carbon needed to reproduce this band is higher than that available for interstellar carbon dust grains. So the ideal structure of irradiated HACs that would produce a band of sufficient strength has still to be searched for.

Spectral analysis is the main tool of astrophysical research.Current instrumental technology offers very sensitive CCD detectorswith enough spectral resolution for many purposes.This introductory text is aimed at graduate students starting a thesisin X-ray astronomy, and at non-specialists who wish to analyseX-ray data themselves. It gives the basic tools and explains the basicissues often implicit in specialised papers. X-ray spectroscopy differs from spectroscopy at longer wavelengths because it is photon based with relatively small numbers ofphotons. As a result the Poisson process is at the core of thestatistical description of X-ray spectra. The classicalmodel-fitting procedure is described and illustrated on a detailedexample. It is applicable to any parametric model and anyinstrumental data. High resolution X-ray spectroscopy, now applicable to many sourcesthanks to sensitive grating instruments, allows to measure individuallines accurately. The diagnostics that it offers are very similarto those offered by mid-resolution optical spectroscopy:line ratios, line broadening, absorption lines.