Related papers: Luminosity indicators in dusty photoionized enviro…
{We explored the {softness parameter} in the infrared, whose main purpose is the characterisation of the hardness of the incident ionising radiation in emission-line nebulae. This parameter is obtained from the combination of mid-infrared…
We exploit ionization-parameter mapping as a powerful tool to measure the optical depth of star-forming HII regions. Our simulations using the photoionization code CLOUDY and our new, SURFBRIGHT surface brightness simulator demonstrate that…
A numerical calculation of properties of finite absorbers and of intergalactic medium based on photoionization equilibrium is performed to confront alternative UV sources in addition to quasars. It is seen that a spectrum including a large…
By radiation transfer models with a realistic power spectra of the projected density distributions, we show that the optical properties of grains are poorly constrained by observations of reflection nebulae. The ISM is known to be…
As soon as the first particles emerge from an ion source, the source characteristics need to be determined. The total beam intensity, the transverse particle distributions, the beam divergence and emittance as well as the longitudinal…
Lyman-$\alpha$ absorption systems at $z \sim 3$ with $N_{HI} \ga 3 \times 10^{14}$ cm$^{-2}$ have been found to be enriched with a mean metallicity of $Z/Z_{\odot} \sim 10^{-2.5}$, and a large scatter in the metallicity. It is reasonable to…
Spectroscopic observations of the low luminosity Seyfert 1 nucleus in NGC 3516 obtained with the Hubble Space Telescope show that the visible spectrum is dominated by the Balmer emission lines of Hydrogen (H) and a continuum luminosity that…
The motion of diamagnetic dust particles in interstellar magnetic fields is studied numerically with several different sets of parameters. Two types of behavior are observed, depending on the value of the critical number $R$, which is a…
Radiation pressure acting on gas and dust causes HII regions to have central densities that are lower than the density near the ionized boundary. HII regions in static equilibrium comprise a family of similarity solutions, parametrized by 3…
In this paper we study new infrared spectra of the evolved planetary nebula NGC 6445 obtained with ISO. These data show that the thermal emission from the grains is very cool and has a low flux compared to H beta. A model of the ionized…
Counting the number and brightness of ionizing radiation sources out to a redshift of z ~ 1.2 will revolutionize our understanding of how the ionizing background is created and sustained by the embedded growth of meta-galactic structures.…
We present model simulations of time-variable infrared (IR) emission from dust as a consequence of variability of the incident radiation. For that we introduce a generalized treatment for temperature variations in a dusty environment, which…
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…
The accepted explanation of the observed dichotomy of two orders of magnitude between in situ measurements of electron density in HII regions, derived from emission line ratios, and average measurements based on integrated emission measure,…
The interaction of a radiation field with a dusty medium is a relevant issue in several astrophysical contexts. We use the time-dependent photoionization code in a dusty medium developed by Perna & Lazzati (2002), to study the modifications…
We investigated the infrared (IR) dust emission from PN IC 418, using a detailed model controlled by a previous determination of the stellar properties and the characteristics of the photoionized nebula, keeping as free parameters the dust…
We present new measurements of the intensity of the ionizing ultraviolet background and the global emissivity of ionizing photons over 2 < z < 5. Our results are based on a suite of updated measurements of physical properties of the…
We present ionization structures of IC 2003, a planetary nebula with [WR] central star, using a 1-D dusty photo-ionization code: "CLOUDY 17.03". The photo-ionization model is constrained by archival UV emission line fluxes,…
We have analysed the infrared hydrogen recombination lines of a sample of well studied hot massive stars observed with the Infrared Space Observatory. Our sample contains stars from several classes of objects, whose circumstellar…
Interstellar polarization from aligned dust grains can be measured both in transmission at visible and near-infrared wavelengths and in emission at far-infrared and sub-mm wavelengths. These observations can help predict the behavior of…