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- Bergvall, Nils, et al.
(author)
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First detection of Lyman continuum escape from a local starburst galaxy. I. Observations of the luminous blue compact galaxy Haro 11 with the Far Ultraviolet Spectroscopic Explorer (FUSE)
- 2006
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In: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 448:513
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Journal article (peer-reviewed)abstract
- Context: The dominating reionization source in the young universe has not yet been identified. Possible candidates include metal poor dwarf galaxies with starburst properties.Aims. We selected an extreme starburst dwarf, the Blue Compact Galaxy Haro 11, with the aim of determining the Lyman continuum escape fraction from UV spectroscopy.Methods. Spectra of Haro 11 were obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE). A weak signal shortwards of the Lyman break is identified as Lyman continuum (LyC) emission escaping from the ongoing starburst. From profile fitting to weak metal lines we derive column densities of the low ionization species. Adopting a metallicity typical of the H II regions of Haro 11, these data correspond to a hydrogen column density of ~10^19cm^-2. This relatively high value indicates that most of the LyC photons escape through transparent holes in the interstellar medium. We then use spectral evolutionary models to constrain the escape fraction of the produced LyC photons.Results. Assuming a normal Salpeter initial mass function we obtain a Lyman continuum escape fraction of f_esc˜ 4-10%. We argue that in a hierarchical galaxy formation scenario, the upper limit we derive for the escape rate allows for a substantial contribution to cosmic reionization by starburst dwarf galaxies at high redshifts.
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| 2. |
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| 3. |
- Bergvall, Nils
(author)
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Universums medvetande
- 2005
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In: Hjärnstrom.
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Journal article (pop. science, debate, etc.)
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| 6. |
- Cumming, Robert, et al.
(author)
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Stellar kinematics in blue compact galaxies
- 2009
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Reports (other academic/artistic)abstract
- In a programme of observations of local luminous blue compact galaxies (BCGs), we are investigating kinematics by using tracers of both stars and ionized gas. Here we summarise our program and present new data on the local Lyman break galaxy analogue Haro 11. From spatially-resolved spectroscopy around the near-infrared Ca II triplet, we find that its stars and ionized gas have similar velocity fields. Our programme so far indicates however that emission line velocities can differ locally by a few tens of km/s from the Ca II values. Comparing our data to simple stellar population models, we assess which stellar population the Ca II triplet traces and its potential beyond the local universe.
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| 8. |
- Marquart, Thomas, et al.
(author)
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Star-gas decoupling and a non-rotating stellar core in He 2-10. : Integral field spectroscopy with FLAMES/ARGUS
- 2007
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 474:L9
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Journal article (peer-reviewed)abstract
- Aims: We study the two-dimensional distribution and kinematics of the stellar and gaseous components in the centre of the blue compact dwarf galaxy He 2-10. The aim is to compare the kinematics of gas and stars in order to determine whether they are consistent with one another, or if stars and gas can be decoupled due to gravitational perturbations and feedback from star formation. Methods: We have used the integral field unit ARGUS, part of FLAMES on the European Southern Observatory's Very Large Telescope, to target the Ca ii λλ8498,8542,8662 Å triplet in the central 300 × 480 parsecs of He 2-10. The selected wavelength regime includes several prominent spectral features, including the Paschen series and the [S iii] emission-line, which we have used to derive the kinematics of the ionised interstellar medium. Results: We find no systematic trend in the velocities of the stars over the observed field of view and conclude that the stellar kinematics is governed by random motions. This is in contrast to the motions the ionised interstellar medium, where we find spatial velocity variations up to 60 km s-1. Our gas velocity field is consistent with previous studies of both the molecular gas and the feedback-driven outflow in He 2-10. We interpret the kinematic decoupling between the stars and the gas as He 2-10 being in the process of transformation to a dwarf elliptical galaxy.
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| 10. |
- Marquart, Thomas, et al.
(author)
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The Kinematics of Extended Hα Emission in Blue Compact Galaxies
- 2007
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In: Galaxy Evolution Across the Hubble Time. - Cambridge : Cambridge University Press. ; , s. 321-321
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Conference paper (peer-reviewed)abstract
- Blue Compact Galaxies are gas-rich systems with strong star formation and spectra that are dominated by young stars and emission lines. Many are true starburts in the sense that the gas consumption timescales are short. The trigger of the starburst is poorly understood, although mergers are likely to play a role. We have observed a large sample (∼50) of low-z emission-line galaxies with a Fabry-Perot instrument, targeting the H-alpha line at high spectral and spatial resolution. Here, we present a small subsample of objects where we detect emission to large radii in the objects. The near-spherical outer isophotes indicate a central ionising source. In addition, the kinematics of the extended emission is different from that of the central starburst, strengthening the hypothesis of a merging event, triggering the central burst while the surrounding gas is still rather undisturbed. We use additional data from own observations and from the literature to quantify the ionising radiation, as well as to estimate the mass in gas and stars that is compared to the dynamical mass.
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