Related papers: Interstellar reddening correction using He I lines
Of the light element abundances capable of testing standard big bang nucleosynthesis, only He4 is measured with an accuracy of a few percent. Thus, it is imperative to establish a comprehensive technique for determining He4 abundances and…
Determinations of the primordial helium abundance are used in precision cosmological tests. These require highly accurate He I recombination rate coefficients. Here we reconsider the formation of He I recombination lines in the low-density…
We present near-infrared spectroscopic observations of the high-intensity HeI 10830 emission line in 45 low-metallicity HII regions. We combined these NIR data with spectroscopic data in the optical range to derive the primordial He…
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…
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…
We consider from a general point of view the problem of determining the extinction in dense molecular clouds. We use a rigorous statistical approach to characterize the properties of the most widely used optical and infrared techniques,…
By employing two different spectroscopic techniques we have mapped out the variable ISM dust extinction endemic to globular cluster M4. We derive an average E(B-V) reddening of 0.33 +/- 0.01 and R = 3.4 +/- 0.4, both in good agreement with…
We present coefficients for the calculation of the continuous emission spectra of HI, HeI and HeII due to electron-ion recombination. Coefficients are given for photon energies from the first ionization threshold for each ion to the n=20…
We present long slit spectrophotometry of two HII regions: TOL2146-391 and TOL0357-3915. We performed a detailed analysis that involves abundance determinations relaxing the assumption of homogeneous temperature. The temperature…
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…
Aims: We systematically explore a plausible subset of the parameter space involving effective temperatures and metallicities of the ionizing stellar sources, the effects of the hardening of their radiation by surrounding leaky HII regions…
We are engaged in a comprehensive program to find reliable elemental abundances in and to probe the physical structure of the Orion Nebula, the brightest and best-resolved H II region. In the course of developing a robust extinction…
Collinear laser spectroscopy has been performed on He-like C$^{4+}$ ions extracted from an electron beam ion source (EBIS). In order to determine the transition frequency with the highest-possible accuracy, the lineshape of the fluorescence…
Both the Galactic 21-cm line flux from neutral hydrogen (HI) in interstellar medium and the far-infrared (FIR) emission from Galactic dust grains have been used to estimate the strength of Galactic reddening of distant sources. In this work…
The analysis of metal-rich HII regions has a profound impact on the calibration of abundance diagnostics widely used to measure the chemical content of star-forming galaxies, both locally and at high redshift. I review the main difficulties…
The band-width effect on interstellar reddening lines in the J-H vs. H-K_s diagram of the 2MASS survey is investigated using synthetic color indices and color excesses based on the Kurucz model atmospheres. At large interstellar reddenings…
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…
The purpose of line-intensity mapping (IM), an emerging tool for extragalactic astronomy and cosmology, is to measure the integrated emission along the line of sight from spectral lines emitted from galaxies and the intergalactic medium.…
In this paper we show how a self-consistent treatment of hydrogen and helium emission line fluxes of the hosts of long gamma-ray bursts can result in improved understanding of the dust properties in these galaxies. In particular, we find…
The high spatial and spectral resolution offered by the new generation of infrared spectrometers at ESO is optimally suited for the observational study of outflows from young stellar objects. Models of interstellar shock waves would benefit…