The Interstellar Medium in the Far Ultraviolet

2009 ◽  
Author(s):  
J. Christopher Howk ◽  
Michael E. Van Steenberg ◽  
George Sonneborn ◽  
H. Warren Moos ◽  
William P. Blair
Keyword(s):  
Interstellar Medium ◽  
Far Ultraviolet

scholarly journals Polyaromatic disordered carbon grains as carriers of the UV bump: Far-UV to mid-IR spectroscopy of laboratory analogs

2017 ◽  
Vol 607 ◽  
pp. A73 ◽  
Author(s):  
L. Gavilan ◽  
K. C. Le ◽  
T. Pino ◽  
I. Alata ◽  
A. Giuliani ◽  
...  
Keyword(s):  
Interstellar Medium ◽  
Interstellar Dust ◽  
Vacuum Ultraviolet ◽  
Interstellar Extinction ◽  
Electronic Transitions ◽  
Mid Infrared ◽  
Pressure Experiment ◽  
Circumstellar Extinction ◽  
Integrated Intensities ◽  
Far Ultraviolet

Context. A multiwavelength study of laboratory carbons with varying degrees of hydrogenation and sp2 hybridization is required to characterize the structure of the carbonaceous carriers of interstellar and circumstellar extinction. Aims. We study the spectral properties of carbonaceous dust analogs from the far-ultraviolet to the mid-infrared and correlate features in both spectral ranges to the aromatic/aliphatic degree. Methods. Analogs to carbonaceous interstellar dust encountered in various phases of the interstellar medium have been prepared in the laboratory. These are amorphous hydrogenated carbons (a-C:H), analogs to the diffuse interstellar medium component, and soot particles, analogs to the polyaromatic component. Thin films (d < 100 nm) have been measured in transmission in the vacuum-ultraviolet (VUV; 120–210 nm) within the atmospheric pressure experiment (APEX) chamber of the DISCO beam line at the SOLEIL synchrotron radiation facility. Spectra of these films were further measured through the UV-Vis (210 nm–1 μm) and in the mid-infrared (3–15 μm). Results. Tauc optical gaps, Eg, are derived from the visible spectra. The major spectral features are fitted through the VUV to the mid-infrared to obtain positions, full-widths at half maximum (FWHM), and integrated intensities. These are plotted against the position of the π-π∗ electronic transitions peak. Unidentified or overlapping features in the UV are identified by correlations with complementary infrared data. A correlation between the optical gap and position of the π-π∗ electronic transitions peak is found. The latter is also correlated to the position of the sp3 carbon defect band at ~8 μm, the aromatic C=C stretching mode position at ~6 μm, and the H/C ratio. Conclusions. Ultraviolet and infrared spectroscopy of structurally diverse carbon samples are used to constrain the nanostructural properties of carbon carriers of both circumstellar and interstellar extinction, such as the associated coherent lengths and the size of polyaromatic units. Our study suggests that carriers of the interstellar UV bump should exhibit infrared bands akin to the A/B classes of the aromatic infrared bands, while the circumstellar bump carriers should exhibit bands corresponding to the B/C classes.

scholarly journals Detection of Escaping Lyman Continuum Radiation in Two Local Starbursts Using FUSE

2006 ◽  
Vol 2 (S235) ◽  
pp. 316-316
Author(s):  
E. Leitet ◽  
N. Bergvall ◽  
B-G Andersson ◽  
E. Zackrisson
Keyword(s):  
Interstellar Medium ◽  
Starburst Galaxies ◽  
Compact Galaxy ◽  
Archival Data ◽  
Continuum Radiation ◽  
Neutral Gas ◽  
Lyman Continuum ◽  
Profile Fitting ◽  
First Results ◽  
Far Ultraviolet

AbstractWe present the detection of escaping Lyman Continuum (LyC) radiation from two local starburst galaxies, Tol 1247-232 and Tol 0440-381, using archival data from the Far Ultraviolet Spectroscopic Explorer (FUSE). From profile fitting of metal lines, high densities of neutral gas were derived for both galaxies, implying that the LyC radiation is escaping from holes in the interstellar medium. The first results for one of the galaxies, Tol 1247-232, give an escape fraction (fesc) of 17–35%. These new detections, together with that of the blue compact galaxy Haro 11 in Bergvall et al. (2006) where fesc between 4–10% was found, will have a feedback on cosmic reionization models.

Spectral Observations of the Extreme Ultraviolet Astronomical Background Radiation

1988 ◽  
Vol 102 ◽  
pp. 63-66
Author(s):  
S. Labov ◽  
S. Bowyer
Keyword(s):  
Interstellar Medium ◽  
Background Radiation ◽  
Extreme Ultraviolet ◽  
Grazing Incidence ◽  
Sounding Rocket ◽  
Interstellar Space ◽  
Spectral Measurements ◽  
Interstellar Gas ◽  
Hot Plasma ◽  
Far Ultraviolet

AbstractObservations in the far ultraviolet and soft x-ray bands suggest that the interstellar medium contains several components of high temperature gas (105to 106K). If large volumes of local interstellar space are filled with this hot plasma, emission lines will be produced in the extreme ultraviolet (EUV). Diffuse EUV radiation, however, has only been detected with photometric instruments; no spectral measurements exist below 520Å. We have designed a unique grazing incidence spectrometer to study the diffuse emission between 80 and 650Å with 10 to 30Å resolution. This instrument was successfully flown on a sounding rocket in April of 1986 and a preliminary analysis reveals several features. In addition to the expected interplanetary He I 584Å emission and the geocoronal He II 304Å emission, other features appear which may originate in the hot ionized interstellar gas. These features are discussed along with the possible implications to the hot phase of the interstellar medium.

scholarly journals The efficiency of grain growth in the diffuse interstellar medium

2021 ◽  
Vol 502 (2) ◽  
pp. 2438-2445
Author(s):  
F D Priestley ◽  
I De Looze ◽  
M J Barlow
Keyword(s):  
Interstellar Medium ◽  
Size Distribution ◽  
Gas Phase ◽  
Grain Growth ◽  
Common Assumption ◽  
Small Grains ◽  
Far Ultraviolet ◽  
Dust Evolution ◽  
Charged Ions ◽  
Positively Charged

ABSTRACT Grain growth by accretion of gas-phase metals is a common assumption in models of dust evolution, but in dense gas, where the time-scale is short enough for accretion to be effective, material is accreted in the form of ice mantles rather than adding to the refractory grain mass. It has been suggested that negatively charged small grains in the diffuse interstellar medium (ISM) can accrete efficiently due to the Coulomb attraction of positively-charged ions, avoiding this issue. We show that this inevitably results in the growth of the small-grain radii until they become positively charged, at which point further growth is effectively halted. The resulting gas-phase depletions under diffuse ISM conditions are significantly overestimated when a constant grain size distribution is assumed. While observed depletions can be reproduced by changing the initial size distribution or assuming highly efficient grain shattering, both options result in unrealistic levels of far-ultraviolet extinction. We suggest that the observed elemental depletions in the diffuse ISM are better explained by higher initial depletions, combined with inefficient dust destruction by supernovae at moderate ($n_{\rm H}\sim 30 \, {\rm cm}^{-3}$) densities, rather than by higher accretion efficiences.

scholarly journals Observations of Local ISM Emission With the Berkeley EUV/FUV Shuttle Telescope

1984 ◽  
Vol 81 ◽  
pp. 344-347
Author(s):  
Christopher Martin ◽  
Stuart Bowyer
Keyword(s):  
Interstellar Medium ◽  
Spectral Resolution ◽  
Space Shuttle ◽  
Extreme Ultraviolet ◽  
Diffuse Background ◽  
Far Ultraviolet

AbstractThe Berkeley Extreme Ultraviolet/Far Ultraviolet Shuttle Telescope (BEST) will be launched on the Space Shuttle in November, 1984, as part of the NASA UVX project. The Berkeley spectrometer will make observations of the cosmic diffuse background in the 600-1900 Å band, with a spectral resolution of 10 Å. The sensitivity and spectral resolution of the instrument make it ideal for the study of components of the interstellar medium in the 104 - 106K range.

Far‐Ultraviolet Observations of Molecular Hydrogen in the Diffuse Interstellar Medium of Starburst Galaxies

2004 ◽  
Vol 612 (2) ◽  
pp. 825-836 ◽  
Author(s):  
Charles G. Hoopes ◽  
Kenneth R. Sembach ◽  
Timothy M. Heckman ◽  
Gerhardt R. Meurer ◽  
Alessandra Aloisi ◽  
...  
Keyword(s):  
Interstellar Medium ◽  
Molecular Hydrogen ◽  
Starburst Galaxies ◽  
Far Ultraviolet ◽  
Ultraviolet Observations

scholarly journals The FUSE Mission: Atomic Data Needs in the 900–1200 Å Spectral Region

2002 ◽  
Vol 12 ◽  
pp. 79-81
Author(s):  
Kenneth R. Sembach
Keyword(s):  
High Resolution ◽  
Solar System ◽  
Interstellar Medium ◽  
Absorption Line ◽  
Ground State ◽  
Spectral Region ◽  
Theoretical Calculations ◽  
Oscillator Strengths ◽  
Atomic Data ◽  
Far Ultraviolet

AbstractThe Far Ultraviolet Spectroscopic Explorer (FUSE) is presently producing high resolution (R ∼ 20,000) absorption-line spectra of astronomical objects ranging from Solar System planets to quasars. The 900-1200 Å spectral region observed by FUSE is exceedingly rich in atomic and molecular transitions arising out of the ground state. It is already clear from early FUSE observations that the atomic data (e.g., oscillator strengths) for some transitions are considerably different than those predicted by theoretical calculations. I briefly describe the most pressing oscillator strength needs in this wavelength range for studies of the interstellar medium.

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