Broad spectral line and continuum variabilities in QSO spectra induced by microlensing of diffusive massive substructure

We investigate the variability of the continuum and broad lines in QSO spectra (particularly in the Hβ line and continuum at λ 5100 Å) caused by microlensing of a diffuse massive structure (like an open star cluster). We modeled the continuum and line emitting region and simulate a lensing event by a star cluster located in an intervening galaxy. Such a type of microlensing event can have a significant influence on magnification and centroid shift of the broad lines and continuum source. We explore relationships between the continuum and broad line flux variability during the microlensing event.     

The evolution of globular clusters

Taking a wide range of the initial conditions, including spatial density distribution and mass function etc, the dynamical evolution of globular clusters in the Milky Way is investigated in detail by means of Monte Carlo simulations. Four dynamic mechanisms are considered: stellar evaporation, stellar evolution, tidal shocks due to both the disk and bulge, and dynamical friction. It is found that stellar evaporation dominates the evolution of low-mass clusters and all four are important for massive ones. For both the power-law and lognormal initial clusters mass functions, we can find the best-fit models which can match the present-day observations with their main features of the mass function almost unchanged after evolution of several Gyr. This implies that it is not possible to determine the initial mass function only based on the observed ones today. Moreover, the dispersion of the modelled mass functions mainly depends on the potential wells of host galaxies with the almost constant peaks, which is consistent with current observations.     

Clusters of Galaxies: Setting the Stage

Clusters of galaxies are self-gravitating systems of mass ∼10¹⁴–10¹⁵ h ⁻¹ M_⊙ and size ∼1–3h ⁻¹ Mpc. Their mass budget consists of dark matter (∼80%, on average), hot diffuse intracluster plasma (≲20%) and a small fraction of stars, dust, and cold gas, mostly locked in galaxies. In most clusters, scaling relations between their properties, like mass, galaxy velocity dispersion, X-ray luminosity and temperature, testify that the cluster components are in approximate dynamical equilibrium within the cluster gravitational potential well. However, spatially inhomogeneous thermal and non-thermal emission of the intracluster medium (ICM), observed in some clusters in the X-ray and radio bands, and the kinematic and morphological segregation of galaxies are a signature of non-gravitational processes, ongoing cluster merging and interactions. Both the fraction of clusters with these features, and the correlation between the dynamical and morphological properties of irregular clusters and the surrounding large-scale structure increase with redshift. In the current bottom-up scenario for the formation of cosmic structure, where tiny fluctuations of the otherwise homogeneous primordial density field are amplified by gravity, clusters are the most massive nodes of the filamentary large-scale structure of the cosmic web and form by anisotropic and episodic accretion of mass, in agreement with most of the observational evidence. In this model of the universe dominated by cold dark matter, at the present time most baryons are expected to be in a diffuse component rather than in stars and galaxies; moreover, ∼50% of this diffuse component has temperature ∼0.01–1 keV and permeates the filamentary distribution of the dark matter. The temperature of this Warm-Hot Intergalactic Medium (WHIM) increases with the local density and its search in the outer regions of clusters and lower density regions has been the quest of much recent observational effort. Over the last thirty years, an impressive coherent picture of the formation and evolution of cosmic structures has emerged from the intense interplay between observations, theory and numerical experiments. Future efforts will continue to test whether this picture keeps being valid, needs corrections or suffers dramatic failures in its predictive power.     

Cosmological Shock Waves

Large-scale structure formation, accretion and merging processes, AGN activity produce cosmological gas shocks. The shocks convert a fraction of the energy of gravitationally accelerated flows to internal energy of the gas. Being the main gas-heating agent, cosmological shocks could amplify magnetic fields and accelerate energetic particles via the multi-fluid plasma relaxation processes. We first discuss the basic properties of standard single-fluid shocks. Cosmological plasma shocks are expected to be collisionless. We then review the plasma processes responsible for the microscopic structure of collisionless shocks. A tiny fraction of the particles crossing the shock is injected into the non-thermal energetic component that could get a substantial part of the ram pressure power dissipated at the shock. The energetic particles penetrate deep into the shock upstream producing an extended shock precursor. Scaling relations for postshock ion temperature and entropy as functions of shock velocity in strong collisionless multi-fluid shocks are discussed. We show that the multi-fluid nature of collisionless shocks results in excessive gas compression, energetic particle acceleration, precursor gas heating, magnetic field amplification and non-thermal emission. Multi-fluid shocks provide a reduced gas entropy production and could also modify the observable thermodynamic scaling relations for clusters of galaxies.     

Evaluation of the contribution of different types of galaxies to the cosmic diffuse background based on γ-ray observations

The relative contribution to the γ-ray background of different types of sources, namely Seyfert Galaxies, Quasars, BL Lac objects, radio galaxies and field galaxies is estimated under the hypothesis that the cosmic diffuse flux is the result of a superposition of many unresolved galaxies. The γ-ray data indicate that the Seyfert volume emissivity matches that of the diffuse background at few hundred keV and exceeds it at higher energies by as much as a factor of about 4. Whilst normal galaxies contribute less than 0.1%, BL Lac objects, Quasars and Radio Galaxies may contribute as much as 5–10% each, even without significant evolution. In this paper we explore different ways of reconciling the observational data on active galaxies with the measured diffuse background level.     

XMM-Newton observations of faint X-ray sources in globular clusters

Using the new generation of X-ray observatories, we are now beginning to identify populations of close binaries in globular clusters, previously elusive in the optical domain because of the high stellar density. These binaries are thought to be, at least in part, responsible for delaying the inevitable core collapse of globular clusters and their identification is therefore essential in understanding the evolution of globular clusters, as well as being valuable in the study of the binaries themselves. Here, we present observations made with XMM-Newton of six globular clusters, in which we have identified neutron star low mass X-ray binaries and their descendants (millisecond pulsars), cataclysmic variables and other types of binaries. We discuss not only the characteristics of these binaries, but also their formation and evolution in globular clusters and their use in tracing the dynamical history of these clusters.     

LiHe spectra from brown dwarfs to helium clusters

The detection of Li I lines is the most decisive spectral indicator of substellarity for young brown dwarfs with masses below about 0.06 solar mass. Due to the weakness of the Li resonance lines, it is important to be able to model precisely both their core widths and their wing profiles. This allows an adequate prediction of the mass at which Li lines reappear in the spectra of brown dwarfs for a given age, or reversely an accurate determination of the age of a cluster. We report improved line profiles and the dependence of line width on temperature suitable for modeling substellar atmospheres that were determined from new LiHe molecular potential energies. Over a limited range of density and temperature, comparison with laboratory measurements was used to validate the potential energies which support the spectral line profile theory.     

氨质子化团簇红外振动光谱研究

运用Gaussian03W计算程序,在B3LYP／6—31G（d）方法水平上得到了氨质子化团簇（NH3）nH^＋（n=1～8）的最稳定构型,并对其相应红外振动光谱进行了研究。通过对红外振动光谱中谱峰位置与振动模式之间的关系的分析,发现光谱中的最强峰均来自于NH4^＋核中N—H键的反对称伸缩振动（n=2除外）。