Observations of Interstellar H and k, Molecular Lines, and Radial Velocities in the Spectra of 300 O and B Stars.

Adams, W. S.

doi:10.1086/145142

Cited by 134 publications

(44 citation statements)

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“…A good example follows observations of the Ca II H and K absorption lines in clouds around hot OB stars that resolve into several radial velocity components (Adams 1949). Moreover, Heckman et al (2011) found that all four local Lyman break analogs with high residual intensities in the low-ionization absorption lines are a better match to the picket fence model compared to a uniform shell model.…”

Section: Methods 1: Low-ionization Covering Fractionsupporting

confidence: 52%

Absorption-Line Spectroscopy of Gravitationally Lensed Galaxies: Further Constraints on the Escape Fraction of Ionizing Photons at High Redshift

Leethochawalit

Jones

Ellis

et al. 2016

ApJ

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The fraction of ionizing photons escaping from high-redshift star-forming galaxies is a key obstacle in evaluating whether galaxies were the primary agents of cosmic reionization. We previously proposed using the covering fraction of low-ionization gas, measured via deep absorption-line spectroscopy, as a proxy. We now present a significant update, sampling seven gravitationally lensed sources at 4<z<5. We show that the absorbing gas in our sources is spatially inhomogeneous, with a median covering fraction of 66%. Correcting for reddening according to a dust-in-cloud model, this implies an estimated absolute escape fraction of ;19%±6%. With possible biases and uncertainties, collectively we find that the average escape fraction could be reduced to no less than 11%, excluding the effect of spatial variations. For one of our lensed sources, we have sufficient signal-tonoise ratio to demonstrate the presence of such spatial variations and scatter in its dependence on the Lyα equivalent width, consistent with recent simulations. If this source is typical, our lower limit to the escape fraction could be reduced by a further factor ;2. Across our sample, we find a modest anticorrelation between the inferred escape fraction and the local star formation rate, consistent with a time delay between a burst and leaking Lyman continuum photons. Our analysis demonstrates considerable variations in the escape fraction, consistent with being governed by the small-scale behavior of star-forming regions, whose activities fluctuate over short timescales. This supports the suggestion that the escape fraction may increase toward the reionization era when star formation becomes more energetic and burst-like.

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Section: Methods 1: Low-ionization Covering Fractionsupporting

confidence: 52%

Absorption-Line Spectroscopy of Gravitationally Lensed Galaxies: Further Constraints on the Escape Fraction of Ionizing Photons at High Redshift

Leethochawalit

Jones

Ellis

et al. 2016

ApJ

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“…Galazutdinov & F. A. Musaev (at Terskol Observatory: K97a,K97b) and G. Herbig (at the Keck telescope: H98) who kindly provided their data, so that we could analyze them in the same way as our own and search for variations by direct comparison of the spectra. Note that in his study, Herbig (1999) searched for changes in line position with respect to the spectrum obtained by Adams (1949) and thus investigated the velocity structure of the foreground gas; no significant variation was observed. Table A.1 summarises all these observations and gives the date, resolution and signal-to-noise ratio.…”

Section: The Available Spectramentioning

confidence: 99%

Small scale structure in molecular gas from multi-epoch observations of HD 34078

Rollinde

Boissé

Federman

et al. 2003

A&A

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Abstract. We present spectroscopic observations of the runaway reddened star HD 34078 acquired during the last three years at Observatoire de Haute Provence and McDonald Observatory as well as other spectra obtained since 1990. The drift of the line of sight through the foreground cloud due to the large transverse velocity of HD 34078 allows us to probe the spatial distribution of CH, CH + , CN and DIBs carriers at scales ranging from about 1 AU up to 150 AU. In particular, time variations in the equivalent width of absorption lines are examined. A few past and recent high resolution observations of CH and CH + absorption are used to search for line profile variations and to convert equivalent widths into column densities. The data set reveals a 20% increase in CH column density over the past 10 years with no corresponding variation in the column density of CH + or in the strengths of the 5780 and 5797 Å DIBs. CN observations indicate that its excitation temperature has significantly increased from <3.1 K in 1993 to 3.6 ± 0.17 K in 1998 while the CN column shows only a modest rise of ≈12±6%. The data also strongly suggest the existence of weak correlated variations in CH and CH + columns over periods of 6-12 months (or ≈10 AU). These results are discussed in relation to CH + production mechanisms. A dense newly intervening clump is considered in order to explain the long-term increase in the column density of CH, but such a scenario does not account for all observational constraints. Instead, the observations are best described by CH + production in a photodissociation region, like that suggested for the Pleiades and IC 348.

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“…The first spectral data of Lyα emission from interstellar gas inside of the heliosphere, obtained by Copernicus, showed the similarity of ISM velocities inside of the heliosphere and towards nearby stars (Adams andFrisch, 1977, McClintock et al, 1978).…”

Section: Neighborhood Ism: Cluster Of Local Interstellar Cloudsmentioning

confidence: 98%

Short-term Variations in the Galactic Environment of the Sun

Frisch

Slavin

Solar Journey: The Significance of Our Galactic Environment for the Heliosphere and Earth

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The galactic environment of the Sun varies over short timescales as the Sun and interstellar clouds travel through space. Small variations in the dynamics, ionization, density, and magnetic field strength in the interstellar medium (ISM) surrounding the Sun can lead to pronounced changes in the properties of the heliosphere. The ISM within ∼30 pc consists of a group of cloudlets that flow through the local standard of rest with a bulk velocity of ∼17-19 km s −1 , and an upwind direction suggesting an origin associated with stellar activity in the Scorpius-Centaurus association. The Sun is situated in the leading edge of this flow, in a partially ionized warm cloud with a density of ∼0.3 cm −3 . Radiative transfer models of this tenuous ISM show that the fractional ionization of the

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Observations of Interstellar H and k, Molecular Lines, and Radial Velocities in the Spectra of 300 O and B Stars.

Cited by 134 publications

References 0 publications

Absorption-Line Spectroscopy of Gravitationally Lensed Galaxies: Further Constraints on the Escape Fraction of Ionizing Photons at High Redshift

Absorption-Line Spectroscopy of Gravitationally Lensed Galaxies: Further Constraints on the Escape Fraction of Ionizing Photons at High Redshift

Small scale structure in molecular gas from multi-epoch observations of HD 34078

Short-term Variations in the Galactic Environment of the Sun

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