Related papers: Interstellar extinction correction in ionised regi…
We present very deep spectrophotometry of 14 bright extragalactic HII regions belonging to spiral, irregular, and blue compact galaxies. The data for 13 objects were taken with the HIRES echelle spectrograph on the Keck I telescope. We have…
Once thought to be devoid of warm and cold interstellar matter, elliptical galaxies are now commonly observed to host extended regions of neutral and ionized gas. Outside of the innermost nuclear regions of these galaxies, the favoured…
Using star-forming galaxies sample in the nearby Universe (0.02<z<0.10) selected from the SDSS (DR7) and GALEX all-sky survey (GR5), we present a new empirical calibration for predicting dust extinction of galaxies from H-alpha-to-FUV flux…
We have introduced a new method of estimating the electron temperature and density of H II regions by using single dish observations. In this method, multiple hydrogen radio recombination lines of different bands are computed under the…
The determination of the heavy element abundances from giant extragalactic H II regions is based on collisionally excited lines. We argue that in the presence of temperature variations the abundances determined are lower limits to the real…
I present a new indirect search for dark matter (DM) using Hydrogen-$\alpha$ (H$\alpha$) recombination emission. DM annihilation or decay products can ionize neutral gas; subsequent recombination cascades generate H$\alpha$ photons through…
We determine and tabulate A(lambda)/A(K), the wavelength dependence of interstellar extinction, in the Galactic plane for 1.25um<lambda<8.0um along two lines of sight: l~42 and l~284. The first is a relatively quiescent and unremarkable…
He II Ly-alpha 304/H-alpha 1640 emission lines are mainly produced by recombination, and their canonical ratio of about 10 may be a sensitive reddening indicator. We obtain the high S/N optical spectra of two quasars and combine them with…
Context. The radiation field consisting of hydrogen recombination lines and continuum emission might significantly affect the hydrogen-level populations in ultra- and hypercompact (U/HC) H II regions. The escape probability approximation…
It has been suggested that the ratio of total-to-selective extinction RV in dust in the interstellar medium differs in the Galactic bulge from its value in the local neighborhood. We attempt to test this suggestion. The mid-infrared…
We examine Lyman continuum extinction (LCE) in H II regions by comparing infrared fluxes of 49 H II regions in the Galaxy, M31, M33, and the LMC with estimated production rates of Lyman continuum photons. A typical fraction of Lyman…
Based on high quality observations of multiplet V1 of OII and the NLTE atomic computations of OII we study the density and temperature of a sample of HII regions. We find that the signature for oxygen rich clumps of high density and low…
Hydrogen recombination lines (RRLs) are one of the major diagnostics of the physical properties of H{\sc ii} regions. We use RRL H40$\alpha$, He40$\alpha$ and 3 mm continuum emission to investigate the properties of a large sample of…
We have studied the interstellar extinction in a field of 3' x 3' located about 6' SW of 30 Doradus in the Large Magellanic Cloud (LMC). Hubble Space Telescope observations in the U, B, V, I and Halpha bands reveal patchy extinction in this…
Accurately determining the elemental abundances of a low metallicity nebula strongly depends on measuring the density (n$_e$) and temperature (T$_e$) of the gas. Because these two parameters are inherently degenerate when derived solely…
We compare the H-beta line strengths of 1.90 < z < 2.35 star-forming galaxies observed with the near-IR grism of the Hubble Space Telescope with ground-based measurements of Ly-alpha from the HETDEX Pilot Survey and narrow-band imaging. By…
We present complete, low resolution IJHK spectroscopy of the ultracompact HII region, G45.12+0.13. From the observed HI line strengths, we derive a near infrared extinction law that is slightly steeper than the average. After correction…
We propose to use HII galaxies (HIIG) to trace the redshift-distance relation, by means of their $L(\mathrm{H}\beta) - \sigma$ correlation, in an attempt to constrain the dark energy equation of state parameter solution space, as an…
We investigate the effect of a global change in the ionizing continuum level on the behavior of the strong optical broad emission-lines seen in spectra of the nuclear emission-line regions of active galactic nuclei (AGN), including the…
Radio recombination lines (RRLs) can be used to determine the emission measure unambiguously along the Galactic plane. We use the deep (2100s per beam) HI Parkes Zone of Avoidance survey which includes 3 RRLs (H$166\alpha$, H$167\alpha$ and…