相关论文: Absorption variability as a probe of the multiphas…

We provide an in-depth analysis of the He II and H I absorption in the intergalactic medium (IGM) at redshifts z = 2.3-2.9 toward HE 2347-4342, using spectra from the Far Ultraviolet Spectroscopic Explorer (FUSE) and the Ultraviolet-Visual…

Recent modeling of the warm absorber in active galactic nuclei has proved the usefulness of constant total (gas plus radiation) pressure models, which are highly stratified in temperature and density. We explore the consistency of those…

We present a detailed study of X-ray absorption in the local interstellar medium by analyzing the X-ray spectra of 24 galactic sources obtained with the {\it Chandra} High Energy Transmission Grating Spectrometer and the {\it XMM-Newton}…

Warm absorber spectra contain bound-bound and bound-free absorption features seen in the X-ray and UV spectra from many active galactic nuclei (AGN). The widths and centroid energies of these features indicate they occur in outflowing gas,…

We present a physically-based absorption-line model for the spectroscopic study of the intergalactic medium (IGM). This model adopts results from Cloudy simulations and theoretical calculations by Gnat and Sternberg (2007) to examine the…

Small-scale fluctuations of different tracers of the interstellar the medium can be used to study the nature of turbulence in astrophysical scales. Of these, the `continuum' emission traces the fluctuations integrated along the line of…

Quantitative description of the statistics of intensity fluctuations within spectral line data cubes introduced in our earlier work is extended to the absorbing media. A possibility of extracting 3D velocity and density statistics from both…

We report multi-epoch GMRT HI observations of the z = 0.3127 damped absorber towards the quasar PKS 1127-145, which reveal variability in both the absorption profile and the flux of the background source, over a time-scale of a few days.…

A numerical calculation of properties of finite absorbers and of intergalactic medium based on photoionization equilibrium is performed to confront alternative UV sources in addition to quasars. It is seen that a spectrum including a large…

We have conducted an extensive X-ray spectral variability study of a sample of 20 Compton-thin type II galaxies using broad band spectra from XMM-Newton, Chandra, and Suzaku. The aim is to study the variability of the neutral intrinsic…

We present a wide grid of models for the structure and transmission properties of warm absorbers in active galactic nuclei (AGN). Contrary to commonly used constant density models, our absorbing cloud is assumed to be under constant total…

The power spectrum of HI intensity fluctuation of the interstellar medium carries information of the turbulence dynamics therein. We present a method to estimate the power spectrum of HI intensity fluctuation using radio interferometric…

We study the variability of major atmospheric absorption features in the disk-integrated spectra of the Earth with future application to Earth-analogs in mind, concentrating on the diurnal timescale. We first analyze observations of the…

The low density hydrogen and helium in the IGM probed by QSO absorption lines is sensitive to the amplitude and spectral shape of the metagalactic UV background. We use realistic HI and HeII Ly-alpha forest spectra, constructed from…

We study fluctuations of particle absorption by a three-dimensional domain with multiple absorbing patches. The domain is in contact with a gas of interacting diffusing particles. This problem is motivated by living cell sensing via…

We investigate the dependence of gas kinematics and column densities in the MgII-absorbing circumgalactic medium on galaxy color, azimuthal angle, and inclination to trace baryon cycle processes. Our sample of 30 foreground isolated…

Ionized carbon is the main gas-phase reservoir of carbon in the neutral diffuse interstellar medium and its 158 micron fine structure transition [CII] is the most important cooling line of the diffuse interstellar medium (ISM). We combine…

Spectra obtained with the Hubble Space Telescope GHRS are combined with high-resolution optical spectra and UV spectra from Copernicus to study the abundances and physical conditions in the diffuse interstellar clouds seen along the line of…

We have carried out a sensitive high-latitude (|b| > 15deg.) HI 21cm-line absorption survey towards 102 sources using the GMRT. With a 3-sigma detection limit in optical depth of ~0.01, this is the most sensitive HI absorption survey. We…

The free energetics of water density fluctuations near a surface, and the rare low-density fluctuations in particular, serve as reliable indicators of surface hydrophobicity; the easier it is to displace the interfacial waters, the more…