Related papers: The Relation Between Optical Extinction and Hydrog…
We measure reddenings to HII regions in NGC 2903, NGC 1512, M51, NGC 4449 and NGC 6946 from Hubble Space Telescope Pa alpha and H alpha images. Extinctions range from A_V ~ 5 - 0 depending upon the galaxy. For the galaxies with HST images…
Dust plays a central role in the unification theory of active galactic nuclei (AGNs). Whether the dust that forms the torus around an AGN is tenth-$\mu$m-sized like interstellar grains or much larger has a profound impact on correcting for…
We combine emission line and X-ray luminosities for 45 sources from the Chandra Deep Field South (CDF-S), and seven HELLAS sources, to obtain a new sample of 52 X-ray selected type-II active galactic nuclei (AGNs). Eighteen of our sources…
We present column density measurements of the HD molecule in the interstellar gas toward 17 Galactic stars. The values for the seven most heavily reddened sightlines, with E(B-V) = 0.38-0.72, are derived from observations with the Far…
Obscuration in active galactic nuclei (AGN) provides insights into the material surrounding the central engine. Compton-thick AGN (CTAGN), characterized by a column density of $N_{\mathrm{H}} \geq 1.5 \times 10^{24} \ \mathrm{cm}^{-2}$, are…
We analyze mutual relations between interstellar extinction E(B-V) and column densities of diatomic molecules such as CN, CH and CH cation observed along translucent sightlines. Observational material acquired using five echelle…
We present a dust-column--dependent extinction curve parameters for ultraviolet wavelengths at high Galactic latitudes. This extinction function diverges from previous work in that it takes into account the results of Peek & Schiminovich…
In Khadka et al. (2023), a sample of X-ray-detected reverberation-mapped quasars was presented and applied for the comparison of cosmological constraints inferred using two well-established relations in AGN -- the X-ray/UV luminosity…
We study the relation between the star formation intensity of galaxies and the extinction by dust of their emitted light. We employ a detailed statistical analysis of Hubble Deep Field North data to show a clear positive correlation between…
New results from the search for H2 absorption in the damped Ly-alpha galaxy at redshift z = 3.4 toward QSO 0000-2620 (z_em = 4.1) are reported. The high-resolution (lambda/Delta lambda = 48,000) spectra of Q0000-2620 were obtained using the…
We develop a method for estimating the host galaxy dust extinction for type Ia supernovae based on an observational coincidence first noted by Lira (1995), who found that the B-V evolution during the period from 30-90 days after V maximum…
We derive radial and vertical distributions of HI and H2 gas densities in our Galaxy by using the terminal velocity method. We calculate the molecular fraction (f_mol) defined as the ratio of the molecular hydrogen to total hydrogen gas…
The optical afterglow spectrum of GRB050401 (at z=2.8992+/-0.0004) shows the presence of a DLA, with log(nHI)=22.6+/-0.3. This is the highest column density ever observed in a DLA, and is about five times larger than the strongest DLA…
We report on the abundance of interstellar neutral nitrogen (NI) for 30 sightlines, using data from the Far Ultraviolet Spectroscopic Explorer (FUSE) and the Hubble Space Telescope (HST). NI column densities are derived by measuring the…
The presence of the dust in the circumnuclear region strongly affects our view of the nucleus itself. The effect is strong in type 2 objects but weaker effect is likely to be present in type 1 objects as well. In these objects a correction…
Estimates made in the 1970's indicated that a supernova occurring within tens of parsecs of Earth could have significant effects on the ozone layer. Since that time, improved tools for detailed modeling of atmospheric chemistry have been…
The detection of circumstellar atomic hydrogen (\ion{H}{1}) via the 21\,cm line remains a persistent challenge in planetary nebula (PN) studies, primarily due to contamination from ubiquitous interstellar \ion{H}{1} 21\,cm emission. In this…
The atomic hydrogen (HI) properties of star-forming galaxies in the local Universe are known to correlate with other galaxy properties via the ``HI scaling relations''. The redshift evolution of these relations serves as an important…
This paper addresses the issue of how best to correct astronomical data for the wavelength-dependent effects of Galactic interstellar extinction. The main general features of extinction from the IR through the UV are reviewed, along with…
The 21 cm hyperfine transition of the atomic hydrogen (HI) in ground state is a powerful probe of the neutral gas content of the universe. This radio frequency transition has been used routinely for decades to observe, both in emission and…