天体物理学
The possibility of detecting proto-galaxies in the UV band is pointed out, assuming that galaxy formation occured at z $\sim 5-6$. It is shown that the diffuse gas in collapsing galaxy sized objects with temperatures $\sim 10^{6\pm0.5}$ K,…
This paper reports on the first results of the Suzaku observation in the Sgr C region. We detected four diffuse clumps with strong line emission at 6.4keV, Ka from neutral or low-ionized Fe. One of them, M359.38-0.00, is newly discovered…
We review the main observational properties of neutron star low mass transients in quiescence. We first survey the discoveries of BeppoSAX. We then focus on recent discoveries by Chandra and XMM-Newton, with special emphsasis on the…
We analyze a new large-scale ($100h^{-1}$Mpc) numerical hydrodynamic simulation of the popular $\Lambda$CDM cosmological model, including in our treatment dark matter, gas and star-formation, on the basis of standard physical processes. The…
We present the luminosity function and color-redshift relation of a magnitude-limited sample of 145 mostly red field E/S0 galaxies at z < 1 from the DEEP Groth Strip Survey (GSS). Most of the E/S0s (86%) form a red envelope in the…
We propose a unified single-field description of the galactic Dark Matter and various uniform scalar fields for the inflation and cosmological constant. The two types of effects could originate from a fluid of both spatially and temporally…
We model the transport of cosmic ray nuclei in the Galaxy by means of a new numerical code. Differently from previous numerical models we account for a generic spatial distribution of the diffusion coefficient. We found that in the case of…
Observational constraints provided by high resolution and high sensitivity observations of external galaxies made in the millimeter and submillimeter range have started to put on a firm ground the study of extragalactic chemistry of…
Very long wavelength universal gravitational waves cannot now produce in clusters of galaxies velocity dispersions greater than that which these systems would possess if they were expanding with the Universe, if the Universe is not younger…
We have extensively mapped a sample of dense molecular clouds (L1512, TMC-1C, L1262, Per 7, L1389, L1251E) in lines of HC3N, CH3OH, SO and C^{18}O. We demonstrate that a high degree of chemical differentiation is present in all of the…
We examine volume-limited samples from the SDSS galaxies to look for relations among internal and collective physical parameters of galaxies as faint as M_r=- 17.5, which include morphology, luminosity, color, color gradient, concentration,…
The ONC appears to be unusual on two grounds: The observed constellation of the OB stars of the entire Orion Nebula cluster and its Trapezium at its centre implies a time-scale problem given the age of the Trapezium, and an IMF problem for…
We present the first tests of a new method, the Correlated Component Analysis (CCA) based on second-order statistics, to estimate the mixing matrix, a key ingredient to separate astrophysical foregrounds superimposed to the Cosmic Microwave…
Doubly-degenerate binary systems consisting of two white dwarfs both composed of carbon and oxygen and close enough that mass is transferred from the less massive to the more massive are possible progenitors of type Ia supernovae. If the…
In the presence of a strong $m=2$ component in a rotating galaxy, the phase space structure near corotation is shaped to a large extent by the {\it invariant manifolds} of the short period family of unstable periodic orbits terminating at…
A commonly used measure to summarize the nature of a photon spectrum is the so-called Hardness Ratio, which compares the number of counts observed in different passbands. The hardness ratio is especially useful to distinguish between and…
We have measured the proper motion (PM) and kinematics of the ansae in NGC 7009 using high dispersion echelle spectra and archive narrow band HST images. Assuming that the ansae are moving at equal and opposite velocities from the central…
We have measured the expansion velocities and proper motion of the ansae in NGC7009 using high dispersion echelle spectra and archive narrow band HST images. Assuming that the ansae are moving at equal and opposite velocities from the…
Within the hierarchical framework for galaxy formation, merging and tidal interactions are expected to shape large galaxies to this day. While major mergers are quite rare at present, minor mergers and satellite disruptions - which result…
We present the far-IR, millimeter, and radio photometry as well as optical and near-IR spectroscopy of a sample of 48 z~1-3 Spitzer-selected ULIRGs with IRS mid-IR spectra. Our goals are to compute their bolometric emission, and to…