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We present results from Monte Carlo simulations describing the radiation transfer of $H\alpha$ line emission, produced both by HII regions in the disk and in the diffuse ionized gas (DIG), through the dust layer of the galaxy NGC891. This…

Astrophysics · Physics 2009-10-28 Andrea Ferrara , Simone Bianchi , Ralf-Juergen Dettmar , Carlo Giovanardi

We investigate the kinematic properties of Galactic HII regions using radio recombination line (RRL) emission detected by the Australia Telescope Compact Array (ATCA) at 4-10 GHz and the Jansky Very Large Array (VLA) at 8-10 GHz. Our HII…

Astrophysics of Galaxies · Physics 2021-11-24 Dana S. Balser , Trey V. Wenger , L. D. Anderson , W. P. Armentrout , T. M. Bania , J. R. Dawson , John M. Dickey

The [NII] 122 and 205 \mu m transitions are powerful tracers of the ionized gas in the interstellar medium. By combining data from 21 galaxies selected from the Herschel KINGFISH and Beyond the Peak surveys, we have compiled 141 spatially…

We use cosmological simulations of reionization to predict the effect of large HII regions around individual high-redshift quasars on the possible signal from the redshifted 21cm line of neutral hydrogen in the pre-reionization era. We show…

Astrophysics · Physics 2009-11-10 Katharina Kohler , Nickolay Y. Gnedin , Jordi Miralda-Escude , Peter A. Shaver

Fragmentation and evolution for the molecular shells of the compact HII regions are less explored compared to their evolved counterparts. We map nine compact HII regions with a typical diameter of 0.4 pc that are surrounded by molecular…

We resolve the kinematic distance ambiguity for 266 inner Galaxy HII regions out of a sample of 291 using existing HI and 13CO sky surveys. Our sample contains all HII regions with measured radio recombination line (RRL) emission over the…

Astrophysics · Physics 2008-12-18 L. D. Anderson , T. M. Bania

The emission line ratios [OIII]5007/H-beta and [NII]6584/H-alpha have been adopted as an empirical way to distinguish between the fundamentally different mechanisms of ionization in emission-line galaxies. However, detailed interpretation…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-15 Sherry C. C. Yeh , Silvia Verdolini , Mark R. Krumholz , Christopher D. Matzner , Alexander G. G. M. Tielens

We present a new catalog of HII regions based on the integral field spectroscopy (IFS) data of the extended CALIFA and PISCO samples. The selection of HII regions was based on two assumptions: a clumpy structure with high contrast of…

Using three-dimensional non-equilibrium ionization (NEI) hydrodynamical simulation of the interstellar medium (ISM), we study the electron density, $n_{e}$, in the Galactic disk and compare it with the values derived from dispersion…

Astrophysics of Galaxies · Physics 2015-06-04 M. A. de Avillez , A. Asgekar , D. Breitschwerdt , E. Spitoni

We report the discovery of nineteen new HI shells in the Southern Galactic Plane Survey (SGPS). These shells, which range in radius from 40 pc to 1 kpc, were found in the low resolution Parkes portion of the SGPS dataset, covering Galactic…

Astrophysics · Physics 2009-11-07 N. M. McClure-Griffiths , John M. Dickey , B. M. Gaensler , A. J. Green

We analyze deterministic and random temporal variations in dispersion measure (DM) from the full three-dimensional velocities of pulsars with respect to the solar system, combined with electron-density variations on a wide range of length…

High Energy Astrophysical Phenomena · Physics 2016-09-29 Michael T. Lam , James M. Cordes , Shami Chatterjee , Megan L. Jones , Maura A. McLaughlin , John W. Armstrong

A set of diffuse interstellar clouds in the inner Galaxy within a few hundred pc of the Galactic plane has been observed at an angular resolution of ~1 arcmin combining data from the NRAO Green Bank Telescope and the Very Large Array. At…

Astrophysics of Galaxies · Physics 2015-06-15 Yurii Pidopryhora , Felix J. Lockman , John M. Dickey , Michael P. Rupen

Observations of H3+ in the Galactic diffuse interstellar medium (ISM) have led to various surprising results, including the conclusion that the cosmic-ray ionization rate (zeta_2) is about 1 order of magnitude larger than previously…

Astrophysics of Galaxies · Physics 2015-06-03 Nick Indriolo , Benjamin J. McCall

We present a study of diffuse extended ionised gas toward three clouds located in the Galactic Centre (GC). One line of sight (LOS) is toward the 20 km s$^{-1}$ cloud (LOS$-$0.11) in the Sgr A region, another LOS is toward the 50 km…

Short-pulse intense lasers have the potential to model extreme astrophysical environments in laboratories. Although there are diagnostics for energetic electrons and ions resulting from laser-plasma interactions, the diagnostics to measure…

We have compiled the most complete compact and ultracompact HII region catalogue to date via multi-wavelength inspection of survey data. We utilise data from the recently available SASSy 850$\mu$m survey to identify massive star forming…

Astrophysics of Galaxies · Physics 2019-07-24 J. O. Djordjevic , M. A. Thompson , J. S. Urquhart , J. Forbrich

We use radio-wave scattering data to constrain the distribution of ionized gas in the outer Galaxy. Like previous models, our model for the H II disk includes parameters for the radial scale length and scale height of the H II, but we allow…

Astrophysics · Physics 2009-10-30 T. Joseph W. Lazio , James M. Cordes

We have studied the radial distribution and luminosity function of normal pulsars in the Galaxy, on the basis of the ATNF Pulsar Catalogue where the distances are calculated according to the new electron density model NE2001. We show that…

Astrophysics · Physics 2007-05-23 I. Yusifov , I. Kucuk

Hypercompact HII regions (HC) are regions of ionized gas associated with the early stages of high-mass star formation. With the aim of better understanding their characteristics, we studied five candidate HC HII regions. Here, we present…

Astrophysics of Galaxies · Physics 2026-05-12 I. T. Rodríguez-Esnard , S. Kurtz , J. D. Pandian , J. Franco , A. Sánchez-Monge , M. A. Trinidad , V. Migenes
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