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Using the IRAM 30m telescope two molecular structures have been detected which cover very small areas, FWHM<1'. The clouds have velocities of v_lsr~5kms and linewidth of dv~0.8km/s; thus they belong most likely to the Milky Way. Applying…

Astrophysics · Physics 2009-11-07 Andreas Heithausen

We investigate the thermodynamics of the ISM and the formation of molecular hydrogen through numerical simulations of spiral galaxies. The model follows the chemical, thermal and dynamical response of the disc to an external spiral…

Astrophysics · Physics 2009-11-13 Clare Dobbs , Simon Glover , Paul Clark , Ralf Klessen

UV radiation feedback from young massive stars plays a key role in the evolution of giant molecular clouds (GMCs) by photoevaporating and ejecting the surrounding gas. We conduct a suite of radiation hydrodynamic simulations of star cluster…

Astrophysics of Galaxies · Physics 2018-06-06 Jeong-Gyu Kim , Woong-Tae Kim , Eve C. Ostriker

A 21 cm neutral hydrogen interferometric survey of the Large Magellanic Cloud (LMC) combined with the Parkes multi-beam HI single-dish survey clearly shows that the HI gas is distributed in the form of clumps or clouds. The HI clouds and…

Optical depth variations in the Galactic neutral interstellar medium (ISM) with spatial scales from hundreds to thousands of astronomical units have been observed through HI absorption against pulsars and continuum sources, while extremely…

We present a new scenario in which massive intragroup HI clouds are the high-density parts of large HI rings/arcs formed by dynamical interaction between galaxy groups and gas-rich, low surface brightness (LSB) galaxies with extended gas…

Astrophysics · Physics 2009-11-10 K. Bekki , B. S. Koribalski , S. D. Ryder , W. J. Couch

High ambient interstellar pressure is suggested as a possible factor to explain the ubiquitous observed growth-rate discrepancy for supernova-driven superbubbles and stellar wind bubbles. Pressures of P/k ~ 1e5 cm-3 K are plausible for…

Astrophysics · Physics 2009-11-10 M. S. Oey , G. Garcia-Segura

The density distribution of the inter-galactic medium is an uncertain but highly important issue in the study of cosmic reionization. It is expected that there are abundant gas clouds hosted by low-mass "minihalos" in the early universe,…

Astrophysics of Galaxies · Physics 2021-01-06 Riouhei Nakatani , Anastasia Fialkov , Naoki Yoshida

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 calculate the hydrogen and helium-ionizing radiation escaping star-forming molecular clouds, as a function of the star cluster mass and compactness, using a set of high-resolution radiation-magneto-hydrodynamic simulations of star…

Astrophysics of Galaxies · Physics 2020-01-29 Chong-Chong He , Massimo Ricotti , Sam Geen

We explore the survival of cool clouds in multi-phase circum-galactic media. We revisit the "cloud crushing problem" in a large survey of simulations including radiative cooling, self-shielding, self-gravity, magnetic fields, and…

Astrophysics of Galaxies · Physics 2020-01-08 Zhihui Li , Philip F. Hopkins , Jonathan Squire , Cameron Hummels

We discuss molecular cloud formation by large-scale supersonic compressions in the diffuse warm neutral medium (WNM). Initially, a shocked layer forms, and within it, a thin cold layer. An analytical model and high-resolution 1D simulations…

We study the protoplanetary disk lifetimes using a large sample of young stellar objects in nearby clusters. To investigate the final phase of disk dissipation, we selected 32 clusters, located within 500 pc and aged between 1 and 100 Myr,…

Solar and Stellar Astrophysics · Physics 2025-07-03 Gregory Mathews Ben , Jessy Jose , Jesús Hernández

The nature of ultracompact H II regions (UCHRs) remains poorly determined. In particular, they are about an order of magnitude more common than would be expected if they formed around young massive stars and lasted for one dynamical time,…

Astrophysics · Physics 2009-11-11 Mordecai-Mark Mac Low , Jayashree Toraskar , Jeffrey S. Oishi , Tom Abel

In this paper a cluster is modelled as a smooth potential (due to the cluster stars) plus the steady tidal field of the Galaxy. In this model there is a minimum energy below which stars cannot escape. Above this energy, however, the time…

Astrophysics · Physics 2009-10-31 T. Fukushige , D. C. Heggie

HI 21 cm observations with the NRAO 140 Foot telescope have revealed a giant HI cloud (G28.17+0.05) in the Galactic plane that has unusual properties. The cloud is 150 pc in diameter, is at a distance of 5 kpc, and contains as much as…

Astrophysics · Physics 2007-05-23 Anthony Minter , Felix J. Lockman

We use the EAGLE suite of cosmological hydrodynamical simulations to study how the HI content of present-day galaxies depends on their environment. We show that EAGLE reproduces observed HI mass-environment trends very well, while…

The Galactic Arecibo L-band Feed Array HI (GALFA-HI) survey is mapping the entire Arecibo sky at 21-cm, over a velocity range of -700 to +700 km/s (LSR), at a velocity resolution of 0.18 km/s and a spatial resolution of 3.5 arcmin. The…

We report the discovery of eleven high-velocity HI clouds at Galactic latitudes of 25-30 degrees, likely embedded in the Milky Way's nuclear wind. The clouds are detected with deep Green Bank Telescope 21 cm observations of a $3.2^\circ…

Astrophysics of Galaxies · Physics 2025-07-08 Rongmon Bordoloi , Andrew J. Fox , Felix J. Lockman

An overview is presented of the main properties of the interstellar medium. Evidence is summarized that the interstellar medium is highly turbulent, driven on different length scales by various energetic processes. Large-scale turbulence…

Astrophysics · Physics 2009-11-11 Andreas Burkert