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WSRT observations have been used to investigate the presence of neutral hydrogen in extremely young radio galaxies. These objects were selected from a sample of High-Frequency Peakers (HFPs). We detect 2 of the 6 observed galaxies…

Astrophysics · Physics 2009-11-11 M. Orienti , R. Morganti , D. Dallacasa

Parkes neutral hydrogen 21 cm line (HI) observations of the surroundings of 9 early-type Local Group dwarfs are presented. We detected numerous HI clouds in the general direction of those dwarfs and these clouds are often offset from the…

Astrophysics · Physics 2008-11-26 A. Bouchard , C. Carignan , L. Staveley-Smith

The extended environment of galaxies contains a wealth of information about the formation and life cycle of galaxies which are regulated by accretion and feedback processes. Observations of neutral hydrogen are routinely used to image the…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-27 Attila Popping , Robert Braun

We present neutral hydrogen (HI) observations using the Robert C. Byrd Green Bank Telescope (GBT) of 70 optically-detected UDG candidates in the Coma region from the Systematically Measuring Ultra-Diffuse Galaxies survey (SMUDGes). We…

We use spectroscopic data from HST and FUSE to study the wide range of ionization states of the "highly ionized high-velocity clouds". Studied extensively in OVI absorption, these clouds are usually assumed to be infalling gas in the…

Astrophysics · Physics 2009-11-10 J. A. Collins , J. M. Shull , M. L. Giroux

We study the properties of low-column density gas clumps in the halo of the Milky Way based on high-resolution 21-cm observations. Using interferometric data from the WSRT and the VLA we study HI emission at low-, intermediate- and high…

Astrophysics of Galaxies · Physics 2015-05-13 N. Ben Bekhti , P. Richter , B. Winkel , F. Kenn , T. Westmeier

The nature of Dark Matter (DM) is one of the most outstanding mysteries of modern astrophysics. While the standard Cold DM (CDM) model successfully explains observations on most astrophysical scales, DM particles have not yet been detected,…

Astrophysics of Galaxies · Physics 2026-01-27 Chi Zhang , Enrico Garaldi , Giulia Despali , Matteo Viel , Lauro Moscardini , Mark Vogelsberger

We present a catalog of 3D Galactic HI filaments over 1/3 of the sky using Galactic Arecibo L-band Feed Array HI (GALFA-HI) data. The 3D filaments are defined to be linear HI features that are continuous in position-position-velocity (PPV)…

Astrophysics of Galaxies · Physics 2025-11-25 M. E. Putman , D. A. Kim , S. E. Clark , L. Li , C. Holm-Hansen , J. E. G. Peek

We conduct spectral observations of 138 superthin galaxies (STGs) with high radial-to-vertical stellar disk scales ratio with the Dual Imaging Spectrograph (DIS) on the 3.5m telescope at the Apache Point Observatory (APO) to obtain the…

Astrophysics of Galaxies · Physics 2021-06-30 Dmitry Bizyaev , D. I. Makarov , V. P. Reshetnikov , A. V. Mosenkov , S. J. Kautsch , A. V. Antipova

Based on sensitive CO measurements from HERACLES and HI data from THINGS, we show that the azimuthally averaged radial distribution of the neutral gas surface density (Sigma_HI + Sigma_H2) in 33 nearby spiral galaxies exhibits a…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-11 F. Bigiel , L. Blitz

Very sensitive 21cm HI measurements have been made at several locations around the Local Group galaxy M31 using the Green Bank Telescope (GBT) at an angular resolution of 9.1', with a 5$\sigma$ detection level of $\rm{N_{HI} = 3.9 \times…

Astrophysics of Galaxies · Physics 2016-01-27 Spencer A. Wolfe , Felix J. Lockman , D. J. Pisano

The large-scale distribution of neutral hydrogen in the Universe will be luminous through its 21 cm emission. Here, for the first time, we use the auto-power spectrum of 21 cm intensity fluctuations to constrain neutral hydrogen…

Cosmology and Nongalactic Astrophysics · Physics 2013-07-01 E. R. Switzer , K. W. Masui , K. Bandura , L. -M. Calin , T. -C. Chang , X. -L. Chen , Y. -C. Li , Y. -W. Liao , A. Natarajan , U. -L. Pen , J. B. Peterson , J. R. Shaw , T. C. Voytek

Atomic Hydrogen-21 cm transition (HI) is an excellent tracer to study and understand the properties of the atomic gas in the Galaxy. Using the Westerbork Synthesis Radio Telescope (WSRT), we observed 12 quasar sightlines to detect galactic…

Astrophysics of Galaxies · Physics 2024-03-19 Narendra Nath Patra , Nirupam Roy

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…

Gas velocity dispersions provide important diagnostics of the forces counteracting gravity to prevent collapse of the gas. We use the 21 cm line of neutral atomic hydrogen (HI) to study HI velocity dispersion and HI phases as a function of…

Astrophysics of Galaxies · Physics 2015-08-06 R. Ianjamasimanana , W. J. G. de Blok , Fabian Walter , George H. Heald , Anahi Caldu-Primo , Thomas H. Jarrett

The emission in the hyperfine structure 21 cm line of atomic hydrogen arising in the halos with masses $\sim10^6-10^{10}$ M$_\odot$ from the Dark Ages in the models with Warm Dark Matter (WDM) is analysed. The halos are assumed to be formed…

Cosmology and Nongalactic Astrophysics · Physics 2020-02-25 B. Novosyadlyj , V. Shulga , Yu. Kulinich , W. Han

The first detailed VLA mapping of the neutral hydrogen distribution in the isolated, edge-on spiral galaxy NGC 3044 is presented. Physical parameters determined for this galaxy are typical for galaxies of its morphological class (SBc). We…

Astrophysics · Physics 2009-10-30 Siow-Wang Lee , Judith A. Irwin

Various scenarios have been proposed to explain the origin of the Galactic high-velocity clouds, predicting different distances and implying widely varying properties for the Galaxy's gaseous halo. To eliminate the difficulties of studying…

Astrophysics · Physics 2007-05-23 Eric D. Miller , Joel N. Bregman

The Arecibo HI Strip Survey probed the halos of ~300 cataloged galaxies and the environments of ~14 groups with sensitivity to neutral hydrogen masses > 10^7 M_sun. The survey detected no objects with properties resembling the High Velocity…

Astrophysics · Physics 2009-10-31 M. A. Zwaan , F. H. Briggs

We use observations from the Giant Metrewave Radio Telescope (GMRT) to measure the atomic hydrogen gas content of star-forming galaxies at z = 0.24 (i.e. a look-backtime of ~3 Gyr). The sample of galaxies studied were selected from…