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An accurate estimate of the interstellar gas density distribution is crucial to understanding the interstellar medium (ISM) and Galactic cosmic rays (CRs). To comprehend the ISM and CRs in a local environment, a study of the diffuse…

High Energy Astrophysical Phenomena · Physics 2020-02-26 T. Mizuno , S. Abdollahi , Y. Fukui , K. Hayashi , T. Koyama , A. Okumura , H. Tajima , H. Yamamoto

The absorption by neutral hydrogen in the intergalactic medium (IGM) produces the Ly$\alpha$ forest in the spectra of quasars. The Ly$\alpha$ forest absorbers have a broad distribution of neutral hydrogen column density $N_{\rm HI}$ and…

Astrophysics of Galaxies · Physics 2023-04-05 Li Yang , Zheng Zheng , T. -S. Kim

One of the keys to interpreting the character and evolution of interstellar matter in the galaxy is understanding the distribution of the low density hot (10^5 K -10^6 K) phase of the interstellar medium (ISM). This phase is much more…

Astrophysics · Physics 2009-10-30 Eric J. Korpela , Stuart Bowyer , Jerry Edelstein

We perform the first measurement of the thermal and ionization state of the intergalactic medium (IGM) across 0.9 < z < 1.5 using 301 \lya absorption lines fitted from 12 HST STIS quasar spectra, with a total pathlength of \Delta z=2.1. We…

Cosmology and Nongalactic Astrophysics · Physics 2024-02-06 Teng Hu , Vikram Khaire , Joseph F. Hennawi , Todd M. Tripp , Jose Oñorbe , Michael Walther , Zarija Lukic

Context. Multi-wavelength studies of galaxies and galactic nuclei allow us to build a relatively more complete picture of the interstellar medium (ISM), especially in the dusty regions of starburst galaxies. An understanding of the physical…

We use Gamma-ray burst (GRB) spectra total continuum absorption to estimate the key intergalactic medium (IGM) properties of hydrogen column density ($\mathit{N}\textsc{hxigm}$), metallicity, temperature and ionisation parameter over a…

Cosmology and Nongalactic Astrophysics · Physics 2021-02-17 Tony Dalton , Simon L. Morris , Michele Fumagalli

The radio frequency 1.4 GHz transition of the atomic hydrogen is one of the important tracers of the diffuse neutral interstellar medium. Radio astronomical observations of this transition, using either a single dish telescope or an array…

Astrophysics of Galaxies · Physics 2016-08-29 Nirupam Roy

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 explore the multiphase structure of the circumgalactic medium (CGM) probed by synthetic spectra through a cosmological zoom-in galaxy formation simulation. We employ a Bayesian method for modelling a combination of absorption lines to…

Astrophysics of Galaxies · Physics 2018-07-11 Cameron Liang , Andrey Kravtsov , Oscar Agertz

We present a novel framework to self-consistently model the effects of radiation fields, dust physics and molecular chemistry (H$_2$) in the interstellar medium (ISM) of galaxies. The model combines a state-of-the-art radiation…

Dark gas in the interstellar medium (ISM) is believed to not be detectable either in CO or Hi radio emission, but it is detected by other means including gamma-rays, dust emission and extinction traced outside the Galactic plane at |b|>5…

Astrophysics of Galaxies · Physics 2015-06-19 Y. Fukui , K. Torii , T. Onishi , H. Yamamoto , R. Okamoto , T. Hayakawa , K. Tachihara , H. Sano

We continue our series of papers on intergalactic medium (IGM) tracers using quasi-stellar objects (QSOs), having examined gamma-ray bursts (GRBs) and blazars in earlier studies. We have estimated the IGM properties of hydrogen column…

Cosmology and Nongalactic Astrophysics · Physics 2022-03-30 Tony Dalton , Simon L. Morris , Michele Fumagalli , Efrain Gatuzz

We have developed a complete model of the hydrogen molecule as part of the spectral simulation code Cloudy. Our goal is to apply this to spectra of high-redshift star-forming regions where H2 absorption is seen, but where few other details…

Astrophysics · Physics 2009-11-13 Gargi Shaw , G. J. Ferland , R. Srianand , N. P. Abel

We investigate the 21-cm signature that may arise from the intergalactic medium (IGM) prior to the epoch of full reionization (z>5). In scenarios in which the IGM is reionized by discrete sources of photoionizing radiation, the neutral gas…

Astrophysics · Physics 2009-10-28 Piero Madau , Avery Meiksin , Martin J. Rees

We use Swift blazar spectra to estimate the key intergalactic medium (IGM) properties of hydrogen column density(Nhxigm), metallicity and temperature over a redshift range of 0.03 leq z leq 4.7, using a collisional ionisation…

High Energy Astrophysical Phenomena · Physics 2021-09-22 Tony Dalton , Simon L. Morris , Michele Fumagalli , Efrain Gatuzz

An accurate treatment of the multiphase interstellar medium (ISM) in hydrodynamic galaxy simulations requires that we follow not only the thermal evolution of the gas, but also the evolution of its chemical state, including its molecular…

Astrophysics of Galaxies · Physics 2015-06-18 Alexander J. Richings , Joop Schaye , Benjamin D. Oppenheimer

Following Bi & Davidsen (1997), we perform one dimensional semi analytic simulations along the lines of sight to model the intergalactic medium (IGM). Since this procedure is computationally efficient in probing the parameter space -- and…

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

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 present a detailed study of an estimator of the HI column density, based on a combination of HI 21cm absorption and HI 21cm emission spectroscopy. This "isothermal" estimate is given by $N_{\rm HI,ISO} = 1.823 \times 10^{18} \int \left[…

Astrophysics of Galaxies · Physics 2014-07-30 Jayaram N. Chengalur , Nissim Kanekar , Nirupam Roy

The interstellar medium (ISM) is a fundamental component of the Milky Way. Studying its chemical composition and the level of its chemical diversity gives us insight into the evolution of the Milky Way and the role of gas in the Galactic…