相关论文: Direct Measurement of Interstellar Extinction Towa…
Line-of-sight extinction estimates to well-studied young T Tauri and Herbig Ae/Be stars are based on many different measurements and analysis methods. This has resulted in wide scatter among the published $A_V$ values for the same star. In…
We present high S/N measurements of the H I Ly alpha absorption line toward 16 Galactic targets which are at distances between approximately 190 and 2200 pc, all beyond the wall of the Local Bubble. We describe the models used to remove…
We present a comprehensive study of interstellar X-ray extinction using the extensive Chandra supernova remnant archive and use our results to refine the empirical relation between the hydrogen column density and optical extinction. In our…
We explore the relationship between dust-emission derived reddening \EBV\ and atomic hydrogen column density N(H I) derived from 21 cm emission surveys. We consider measurements at galactic latitude $|b| \ga 20$\degr\ and \EBV\ $\la$ 0.1…
The environment around protoplanetary disks (PPDs) regulates processes which drive the chemical and structural evolution of circumstellar material. We perform a detailed empirical survey of warm molecular hydrogen (H$_2$) absorption…
Obtaining a complete census of gas in the local interstellar medium (<100 pc) is challenging given the limited available tracers of the warm, partially-ionized medium. Medium-to-high resolution UV absorption spectroscopy toward individual…
The ability to robustly determine galaxy properties such as masses, ages and star-formation rates is critically limited by the ability to accurately measure dust attenuation. Dust reddening is often characterized by comparing observations…
We present a new map of interstellar reddening, covering the 39\% of the sky with low {\rm HI} column densities ($N_{\rm HI} < 4\times10^{20}\,\rm cm^{-2}$ or $E(B-V)\approx 45\rm\, mmag$) at $16\overset{'}{.}1$ resolution, based on all-sky…
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…
We search the Hubble Space Telescope (HST) archive for previously unanalyzed observations of stellar H I Lyman-alpha emission lines, our primary purpose being to look for new detections of Lyman-alpha absorption from the outer heliosphere,…
We aim to compare variations in the full-UV dust extinction curve (912-3000 Angstrom), with the HI/H$_2$/total H content along diffuse Milky Way sightlines, to investigate possible connections between ISM conditions and dust properties. We…
The processes allowing the escape of ionizing photons from galaxies into the intergalactic medium are poorly known. To understand how Lyman continuum (LyC) photons escape galaxies, we constrain the HI covering fractions and column densities…
The near-infrared emission lines of Fe$^{+}$ at 1.257, 1.321, and 1.644 $\mu$m share the same upper level; their ratios can then be exploited to derive the extinction to a line emitting region once the relevant spontaneous emission…
Hydrogen column densities inferred from X-ray absorption are typically 5 - 30 times larger than the neutral atomic hydrogen column densities derived from 21cm HI absorption toward radio-loud active galactic nuclei. Some part of the…
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…
Understanding the interstellar and potentially circumstellar extinction in the sight lines of classical T Tauri stars is an important ingredient for constructing reliable spectral energy distributions, which catalyze protoplanetary disk…
We present high-resolution (FWHM ~ 0.3-1.5 km/s) spectra of interstellar Ca I absorption toward 30 Galactic stars. Comparisons of the column densities of Ca I, Ca II, K I, and other species -- for individual components identified in the…
Cold, neutral interstellar gas, the reservoir for star formation, is traced through the absorption of the 21-centimetre continuum radiation by neutral hydrogen (HI). Although detected in one hundred cases in the host galaxies of distant…
The logarithmic extinction coefficient, c(H$\beta$), is usually derived using the H$\alpha$/H$\beta$ ratio for case B recombination and assuming standard values of electron density and temperature. However, the use of strong Balmer lines…
We have determined column densities of H I and/or H_2 for sight lines in the Magellanic Clouds from archival HST and FUSE spectra of H I Lyman-alpha and H_2 Lyman-band absorption. Together with some similar data from the literature, we now…