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Anomalies in the abundance measurements of short lived radionuclides in meteorites indicate that the protosolar nebulae was irradiated by a large number of energetic particles ($E\gtrsim10\,$MeV), often called solar cosmic rays. The…

Solar and Stellar Astrophysics · Physics 2020-01-22 Ch. Rab , M. Padovani , M. Güdel , I. Kamp , W. -F. Thi , P. Woitke

(abridged)The focus of this work is to study mid-infrared point sources and the diffuse interstellar medium (ISM) in the low-metallicity (~0.2 solar) giant HII region N66 using the Spitzer Space Telescope's Infrared Spectrograph. We study…

We present three-dimensional radiation-hydrodynamical simulations of the impact of stellar winds, photoelectric heating, photodissociating and photoionising radiation, and supernovae on the chemical composition and star formation in a…

During reionization, a fraction of galactic Ly$\alpha$ emission is scattered in the intergalactic medium (IGM) and appears as a diffuse light extending megaparsecs from the source. We investigate how to probe the properties of the early…

Cosmology and Nongalactic Astrophysics · Physics 2022-06-08 Hyunbae Park , Hyo Jeong Kim , Kyungjin Ahn , Hyunmi Song , Intae Jung , Pierre Ocvirk , Paul R. Shapiro , Taha Dawoodbhoy , Jenny G. Sorce , Ilian T. Iliev

Upcoming 21 cm intensity mapping experiments like the Square Kilometer Array (SKA) hold significant potential to constrain the properties of dark matter. In this work, we model neutral hydrogen (HI) distributions using high-resolution…

Cosmology and Nongalactic Astrophysics · Physics 2024-01-02 Tibor Dome , Rumail Azhar , Anastasia Fialkov

If enough of their Lyman limit continuum escapes, star-forming galaxies could be significant contributors to the cosmic background of ionizing photons. To investigate this possibility, we obtained the first deep imaging in the far…

Astrophysics · Physics 2009-11-10 Matthew Malkan , Wayne Webb , Quinn Konopacky

The processes allowing the escape of ionizing photons from galaxies into the intergalactic medium are poorly known. To understand how Lyman continuum (LyC) photons escape galaxies, we constrain the HI covering fractions and column densities…

Astrophysics of Galaxies · Physics 2018-08-08 Simon Gazagnes , John Chisholm , Daniel Schaerer , Anne Verhamme , Jane R. Rigby , Matthew Bayliss

We present a study of the cold atomic hydrogen (HI) content of molecular clouds simulated within the SILCC-Zoom project. We produce synthetic observations of HI at 21 cm including HI self-absorption (HISA) and observational effects. We find…

Astrophysics of Galaxies · Physics 2022-03-14 D. Seifried , H. Beuther , S. Walch , J. Syed , J. D. Soler , P. Girichidis , R. Wünsch

We use the Galaxies-Intergalactic Medium Interaction Calculation (GIMIC) cosmological hydrodynamic simulation at z=0 to study the distribution and environmental dependence of neutral hydrogen (HI) gas in the outskirts of simulated galaxies.…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-18 D. Cunnama , S. Andrianomena , C. M. Cress , A. Faltenbacher , B. K. Gibson , T. Theuns

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 21-cm signal in the vicinity of the first stars is expected to reflect properties of the first stars. In this study we pay special attention to tracing the time evolution of the ionizing photons' escape fraction, which affects the…

Astrophysics of Galaxies · Physics 2018-08-08 Toshiyuki Tanaka , Kenji Hasegawa , Hidenobu Yajima , Masato I. N. Kobayashi , Naoshi Sugiyama

Using Green Bank Telescope radio recombination line (RRL) data, we analyze the role of leaking radiation from HII regions in maintaining the ionization of the interstellar medium. We observed a sample of eight Galactic HII regions of…

Astrophysics of Galaxies · Physics 2019-02-27 Matteo Luisi , L. D. Anderson , Bin Liu , D. Anish Roshi , Ed Churchwell

O VI absorption is observed in a wide range of astrophysical environments, including the Local ISM, the disk and halo of the Milky Way, high-velocity clouds, the Magellanic clouds, starburst galaxies, the intergalactic medium, damped…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-27 Andrew J. Fox

We calculate the column density distribution of damped Lyman alpha systems, modeled as spherical isothermal gaseous halos ionized by the external cosmic background. The effects of self-shielding introduce a hump in this distribution, at a…

Astrophysics · Physics 2009-11-07 Zheng Zheng , Jordi Miralda-Escude

The observed high covering fractions of neutral hydrogen (HI) with column densities above $\sim 10^{17} \rm{cm}^{-2}$ around Lyman-Break Galaxies (LBGs) and bright quasars at redshifts z ~ 2-3 has been identified as a challenge for…

Cosmology and Nongalactic Astrophysics · Physics 2016-02-25 Alireza Rahmati , Joop Schaye , Richard G. Bower , Robert A. Crain , Michelle Furlong , Matthieu Schaller , Tom Theuns

This work is the continuation of a series attempting to characterize the local warm ionized medium through both static and time dependent simulations. We build upon our three dimensional, observationally-derived simulation of the local…

Astrophysics of Galaxies · Physics 2025-06-24 Lewis McCallum , Kenneth Wood , Robert Benjamin , Dhanesh Krishnarao , Anna F. McLeod

For the low density filamentary and sheet-like structures in the warm ($\sim 10^4$ to $\sim 10^6$ K) IGM predicted by numerical simulations the resonant line scattering of X-ray background (XRB) photons by He and H-like ions of heavy…

Astrophysics · Physics 2009-10-31 E. Churazov , M. Haehnelt , O. Kotov , R. Sunyaev

Motivated by recent evidence that the epoch of reionization of hydrogen may have ended at a redshift as low as z~6 we consider the detectability of the sources responsible for this reionization. The main idea is that reionization places…

Astrophysics · Physics 2009-11-10 M. Stiavelli , S. M. Fall , N. Panagia

The boundary conditions of the heliosphere are set by the ionization, density and composition of inflowing interstellar matter. Constraining the properties of the Local Interstellar Cloud (LIC) at the heliosphere requires radiative transfer…

Astrophysics · Physics 2009-11-13 Jonathan D. Slavin , Priscilla C. Frisch

The HI and CO components of the interstellar medium (ISM) are usually used to derive the dynamical mass M_dyn of nearby galaxies. Both components become too faint to be used as a tracer in observations of high-redshift galaxies. In those…