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Related papers: HI column density statistics of the cold neutral m…

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We examine the statistics of the low-redshift Ly-alpha forest in an adaptive mesh refinement hydrodynamic cosmological simulation of sufficient volume to include distinct large-scale environments. We compare our HI column density…

Cosmology and Nongalactic Astrophysics · Physics 2017-08-23 Stephanie Tonnesen , Britton D. Smith , Juna Kollmeier , Renyue Cen

We report on the detection of low-column density neutral hydrogen clumps in the halo of the Milky Way. Using high-resolution (FWHM~7 km/s) optical spectra obtained with the VLT/UVES spectrograph we detect narrow interstellar absorption by…

Astrophysics · Physics 2009-11-11 Philipp Richter , Tobias Westmeier , Christian Bruens

Context. The earliest phases of high-mass star formation are poorly understood. Aims. Our goal is to determine the physical conditions and kinematic structure of massive star-forming cloud clumps. Methods. We analyze H$_2$O 557 GHz line…

Solar and Stellar Astrophysics · Physics 2014-10-15 Russell F. Shipman , Floris F. S van der Tak , Friedrich Wyrowski , Fabrice Herpin , Wilfred Frieswijk

The observed star formation rates of galaxies in the Local Universe suggests that they are replenishing their gas reservoir across cosmic time. Cosmological simulations predict that this accretion of fresh gas can occur in a hot or a cold…

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 present an automated routine to search for HI self-absorption features within the Southern Galactic Plane Survey (SGPS). The data were taken with the Australia Telescope Compact Array (ATCA) and the Parkes Radio Telescope and encompass 3…

Astrophysics · Physics 2009-11-10 D. W. Kavars , J. M. Dickey , N. M. McClure-Griffiths , B. M. Gaensler , A. J. Green

Several different methods are regularly used to infer the properties of the neutral interstellar medium (ISM) using atomic hydrogen (H I) 21cm absorption and emission spectra. In this work, we study various techniques used for inferring ISM…

Astrophysics of Galaxies · Physics 2023-11-27 Soumyadeep Bhattacharjee , Nirupam Roy , Prateek Sharma , Amit Seta , Christoph Federrath

We have complemented existing observations of HI absorption with new observations of HCO$^+$, C$_2$H, HCN, and HNC absorption from the Atacama Large Millimeter/submillimeter Array (ALMA) and the Northern Extended Millimeter Array (NOEMA) in…

The opacity of spiral galaxy disks, from counts of distant galaxies, is compared to HI column densities. The opacity measurements are calibrated using the ``Synthetic Field Method'' from Gonzalez et al (1998) and Holwerda et al. (2005a).…

Astrophysics · Physics 2009-11-11 B. W. Holwerda , R. A. González , Ronald J. Allen , P. C. van der Kruit

The physical state of cold cloud clumps has a great impact on the process and efficiency of star formation and the masses of the forming stars inside these objects. The sub-millimetre survey of the Planck space observatory and the…

Astrophysics of Galaxies · Physics 2017-10-25 O. Fehér , M. Juvela , T. Lunttila , J. Montillaud , I. Ristorcelli , S. Zahorecz , L. V. Tóth

The origins and generation mechanisms of the slow solar wind are still unclear. Part of the slow solar wind is populated by "number density structures", discrete patches of increased number density that are frozen in to and move with the…

Space Physics · Physics 2018-06-06 D. Stansby , T. S. Horbury

With the aim of evaluating the roles of the cold neutral medium (CNM) in the cloud-scale baryon cycle, we perform a high-resolution study of the CNM in and around the extreme star-forming region 30 Doradus (30 Dor). For our study, we use…

We present a 21cm line HI self-absorption (HISA) survey of cold atomic gas within Galactic longitudes 75 to 146 degrees and latitudes -3 to +5 degrees. We identify HISA as spatially and spectrally confined dark HI features and extract it…

Using a Fourier-plane technique, we have merged HI ATCA and Parkes data sets providing an accurate set of images of the LMC sensitive to structure on scales of 15 pc (for an LMC distance of 55 kpc) upwards. The spatial dynamic range (2.8…

Astrophysics · Physics 2008-11-26 S. Kim , L. Staveley-Smith , M. A. Dopita , R. J. Sault , K. C. Freeman , Y. Lee , Y. -H. Chu

We present hydrostatic equilibrium models of spherical, self-gravitating clouds of helium and molecular hydrogen, focusing on the cold, high-density regime where solid- or liquid-hydrogen can form. The resulting structures have masses from…

Astrophysics of Galaxies · Physics 2019-08-21 Mark Walker , Mark Wardle

The neutral interstellar medium (ISM) inside the Local Bubble (LB) has been known to have properties typical of the warm neutral medium (WNM). However, several recent neutral hydrogen (HI) absorption experiments show evidence for the…

Astrophysics · Physics 2009-06-23 Snezana Stanimirovic

A major challenge in CGM studies is determining the three-dimensional (3D) properties from the observed projected observations. Here, we decompose the 3D gas density and spatial distribution of cool clouds by fitting a cool CGM model with…

Astrophysics of Galaxies · Physics 2025-03-04 Hang Yang , Zhijie Qu , Joel N. Bregman , Li Ji

This paper presents a statistical explanation of filament formation in the galactic atomic hydrogen. Recently developed technique allows to determine the 3D spectrum of random HI density. We claim that even in the absence of dynamical…

Astrophysics · Physics 2009-10-28 Alex Lazarian , Dmitri Pogosyan

Galaxy disks are shown to contain a significant population of atomic clouds of 100pc linear size which are self-opaque in the 21cm transition. These objects have HI column densities as high as 10^23 and contribute to a global opacity…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-04 Robert Braun

This paper reports dual-epoch, Very Long Baseline Array observations of H I absorption toward 3C 147. One of these epochs (2005) represents new observations while one (1998) represents the reprocessing of previous observations to obtain…

Astrophysics of Galaxies · Physics 2009-11-13 T. Joseph W. Lazio , C. L. Brogan , W. M. Goss , S. Stanimirovic