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Physical properties of the tiny scale structures in the cold neutral medium (CNM) of galaxies is a long-standing puzzle. Only a few lines of sights in our Galaxy have been studies with mixed results on the scale-invariant properties of such…

Astrophysics of Galaxies · Physics 2020-01-08 P. K. Vishwakarma , P. Dutta

We have developed a new X-ray absorption model, called {\tt IONeq}, which computes the optical depth $\tau(E)$ simultaneously for ions of all abundant elements, assuming ionization equilibrium and taking into account turbulent broadening.…

High Energy Astrophysical Phenomena · Physics 2017-12-20 Efrain Gatuzz , Eugene Churazov

We present a new catalogue of Damped Lyman-$\alpha$ absorbers from SDSS DR16Q, as well as new estimates of their statistical properties. Our estimates are computed with the Gaussian process models presented in Garnett et al. (2017); Ho et…

Astrophysics of Galaxies · Physics 2021-08-24 Ming-Feng Ho , Simeon Bird , Roman Garnett

We study the column densities of neutral atomic, molecular, and warm ionized Galactic gas through their continuous absorption of extragalactic X-ray spectra at |b| > 25 degrees. For N(H,21cm) < 5x10^20 cm^-2 there is an extremely tight…

Astrophysics · Physics 2014-10-13 John S. Arabadjis , Joel N. Bregman

Aims: Our aim is to identify the dominant molecular cooling lines and characteristic emission features in the 1.3 mm window of distinct regions in the northern part of the Orion A molecular cloud. By defining and analysing template regions,…

Astrophysics of Galaxies · Physics 2020-04-15 N. Brinkmann , F. Wyrowski , J. Kauffmann , D. Colombo , K. M. Menten , X. D. Tang , R. Güsten

Analytic derivations of the correlation function and the column density distribution for neutral hydrogen in the IGM are presented, assuming that the non-linear baryonic mass density distribution in the IGM is lognormal. This ansatz was…

Astrophysics · Physics 2009-10-31 T. Roy Choudhury , T. Padmanabhan , R. Srianand

In a previous paper we presented the results of applying machine learning to classify whether an HI 21-cm absorption spectrum arises in a source intervening the sight-line to a more distant radio source or within the host of the radio…

Instrumentation and Methods for Astrophysics · Physics 2021-07-14 S. J. Curran

We present new estimates for the statistical properties of damped Lyman-$\alpha$ absorbers (DLAs). We compute the column density distribution function at $z>2$, the line density, $\mathrm{d}N/\mathrm{d}X$, and the neutral hydrogen density,…

Astrophysics of Galaxies · Physics 2017-01-25 Simeon Bird , Roman Garnett , Shirley Ho

Damped Ly\alpha\ systems (DLAs) observed in the quasar spectra are characterized by a high neutral hydrogen column density $N_{HI}>2\times 10^{20}{\rm\ cm^{-2}}$. The absorption wing profiles are often fitted using the Voigt function due to…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-16 Hee-Won Lee

We carried out synthetic observations of interstellar atomic hydrogen at 21cm wavelength by utilizing the magneto-hydrodynamical numerical simulations of the inhomogeneous turbulent interstellar medium (ISM) Inoue and Inutsuka (2012). The…

We combine cosmological, hydrodynamical simulations with accurate radiative transfer corrections to investigate the relation between strong HI absorbers (N_HI >~ 10^17 /cm^2) and galaxies at redshift z = 3. We find a strong anti-correlation…

Cosmology and Nongalactic Astrophysics · Physics 2019-08-19 Alireza Rahmati , Joop Schaye

We analyzed a sample of 26 background X-ray sources in a ~60 square degree field of the Large Magellanic Cloud observed with the ROSAT PSPC. The sample has been selected from previously classified and optically identified X-ray sources. In…

Astrophysics · Physics 2009-11-06 P. Kahabka , K. S. de Boer , C. Bruens

We have performed high-resolution hydrodynamic simulations of the Lyman-alpha forest in a variety of popular cold dark matter dominated cosmologies, including a low density and a vacuum-dominated model. The fluctuation amplitude of these…

Astrophysics · Physics 2009-10-31 Tom Theuns , Anthony Leonard , Joop Schaye , George Efstathiou

We present a theoretical model, using density matrix approach, to study the effect of weak as well as strong probe field on the optical properties of an inhomogeneously broadened multilevel V-system of the $^{87}$Rb D2 line. We consider the…

Atomic Physics · Physics 2015-12-04 Paramjit Kaur , Vineet Bharti , Ajay Wasan

We report on the highly variable SiIV and CIV broad absorption lines in SDSS J113831.4+351725.2 across four observational epochs. Using the SiIV doublet components, we find that the blue component is usually saturated and non-black, with…

Astrophysics of Galaxies · Physics 2015-03-03 Conor Wildy , Michael R. Goad , James T. Allen

We present an analysis of high resolution HST Space Telescope Imaging Spectrograph (STIS) observations of O I 1356 and H I Lyman-alpha absorption in 36 sight lines that probe a variety of Galactic disk environments and include paths that…

Astrophysics · Physics 2009-11-10 Stefan I. B. Cartledge , J. T. Lauroesch , David M. Meyer , Ulysses J. Sofia

A detailed theoretical study of the optical absorption in self-assembled quantum dots is presented in this paper. A rigorous atomistic strain model as well as a sophisticated electronic band structure model are used to ensure accurate…

We present a comprehensive examination of interstellar P and Cl abundances based on an analysis of archival spectra acquired with the Space Telescope Imaging Spectrograph of the Hubble Space Telescope and the Far Ultraviolet Spectroscopic…

Astrophysics of Galaxies · Physics 2023-05-30 Adam M. Ritchey , J. M. Brown , S. R. Federman , Paule Sonnentrucker

Using high resolution infrared spectroscopy we have surveyed twenty sightlines for H3+ absorption. H3+ is detected in eight diffuse cloud sightlines with column densities varying from 0.6x10^14 cm^-2 to 3.9x10^14 cm^-2. This brings to…

Astrophysics · Physics 2009-11-13 Nick Indriolo , Thomas R. Geballe , Takeshi Oka , Benjamin J. McCall