Reexamining the Lyman Continuum in Starburst Galaxies Observed with the Hopkins Ultraviolet Telescope

Hurwitz, M.; Jelinsky, Patrick; Dixon, W. V.

doi:10.1086/310649

Cited by 106 publications

(123 citation statements)

References 9 publications

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“…The present observation of Mrk 54 adds another significant limit to three other cases with upper limits of 3.2%, 5.2% and 11%, as resulting from the observations of Leitherer et al re-analyzed by Hurwitz et al (1997).…”

Section: Resultssupporting

confidence: 65%

“…The wavelength range of FUSE, down to 905 A, offers again the possibility to observe a few star-forming galaxies with their Ly c radiation redshifted above the limit of HI photoelectric opacity in our Galaxy. The redshifts of these objects have to be large enough to get rid, in combination with the spectral resolution of FUSE, of the (Lyman series) absorption lines from neutral hydrogen in our Galaxy as emphasized by Hurwitz et al (1997). The spectral resolution of FUSE is also expected to allow correction for molecular hydrogen absorption in our Galaxy.…”

Section: Introductionmentioning

confidence: 98%

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First Results from the FUSE Mission

Sonneborn¹,

Moos

2002

Highlights astron.

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Abstract. The Far Ultraviolet Spectroscopic Explorer (FUSE) provides high-resolution spectroscopy at far ultraviolet (FUV) wavelengths (905-1187A) of many astronomical objects in order to address fundamental questions related to the origin of the universe. FUSE, a cooperative project of the United States, Canada, and France, was launched in June 1999 for a three-year primary mission. The instrument sensitivity permits studies of many extragalactic sources at high spectral resolution. The key science drivers for the mission design are absorption-line spectroscopy of the ISM and IGM to investigate D/H, O VI, and molecular hydrogen abundances and distribution in the Galaxy and beyond t o z~ 0.3. Most of the observing time is available to Guest Investigators. This Joint Discussion summarizes some of the scientific results determined primarily from the first several months of FUSE observations.

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Section: Resultssupporting

confidence: 65%

Section: Introductionmentioning

confidence: 98%

First Results from the FUSE Mission

Sonneborn¹,

Moos

2002

Highlights astron.

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“…This has important implications for attempts to estimate the H-ionizing flux due to the first massive stars, which presumably form in the shallow potentials predicted to be present in large numbers well before in standard hiz p 6 erarchical cosmogonies (Madau et al 1999). Note that because of the much smaller dust content, a comparison of the composite spectrum of Steidel et al with the UV spectra of low-redshift starbursts, as observed, e.g., by Leitherer et al (1995) and Hurwitz, Jelinski, & Dixon (1997), is not straightforward.…”

Section: The Uv Escape Fraction Of Galaxies and The Redshift Evolutiomentioning

confidence: 96%

An Ionizing Ultraviolet Background Dominated by Massive Stars

Haehnelt

Madau

Kudritzki

et al. 2001

The Astrophysical Journal

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We discuss the implications of a stellar-dominated UV background at high redshifts for the star formation history of Lyman break galaxies (LBGs) and the thermal and ionization state of the intergalactic medium (IGM). The composite spectrum of 29 LBGs evaluated by Steidel et al. at can be well fitted by a stellar AzS p 3.4 population with ongoing star formation, a Salpeter initial mass function, modest or negligible dust reddening, and no intrinsic H i photoelectric absorption. Fading starbursts in which star formation has ceased for 10 7 yr or more cannot reproduce the observed flux shortward of 1 ryd. The small H i optical depth in LBGs suggests that the neutral gas from which stars form is most likely contained in compact clouds of neutral gas with small covering factor. The escape fraction of H-ionizing photons must be close to 100% for the observed sample of LBGs. The spectrum of ionizing photons produced by a stellar population with ongoing star formation is similar to that of QSOs between 1 and 3 ryd but becomes softer between 3 and 4 ryd and drops sharply shortward of 4 ryd. A galaxy-dominated UV background appears inconsistent with the observed He ii/H i opacity ratio at but might be able to explain the Si iv/C iv abundances measured at in QSO absorption spectra. z p 2.4 z 1 3 A scenario may be emerging where star-forming galaxies reionize intergalactic hydrogen at and dominate z 1 6 the 1 ryd metagalactic flux at , with quasi-stellar sources taking over at lower redshifts. If the large amplitude z 1 3 of the H-ionizing flux estimated by Steidel et al. is correct, hydrodynamical simulations of structure formation in the IGM within the cold dark matter paradigm require a baryon density (to explain the observed opacity of the Lya forest in QSO absorption spectra) that is similar to or larger than that favored by recent cosmic microwave background experiments and is inconsistent with standard nucleosynthesis values.

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“…Attempts to observe the Lyman continuum flux of galaxies in the local Universe yielded null results, thus placing only upper limits on the escape fraction. The escape fraction from five local starburst galaxies that were selected for a high predicted escape fraction were found to be less than 3−10% (Hurwitz et al 1997;Deharveng et al 2001). For the local extreme starburst dwarf galaxy Haro 11, that was selected to be representative for dwarf starbursts at high redshift, Bergvall et al (2006) found the escape to be less than 10%, but reanalysis by Grimes et al (2007) showed that for the same galaxy f esc < 2%.…”

Section: Introductionmentioning

confidence: 98%

The escape of ionising radiation from high-redshift dwarf galaxies

Paardekooper

Pelupessy

Altay³

et al. 2011

A&A

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Context. The UV escape fraction from high-redshift galaxies plays a key role in models of cosmic reionisation. Because it is currently not possible to deduce the escape fractions during the epoch of reionisation from observations, we have to rely on numerical simulations. Aims. We aim to better constrain the escape fraction from high-redshift dwarf galaxies, as these are the most likely sources responsible for reionising the Universe. Methods. We employ a N-body/SPH method that includes realistic prescriptions for the physical processes that are important for the evolution of dwarf galaxies. These models are post-processed with radiative transfer to determine the escape fraction of ionising radiation. We perform a parameter study to assess the influence of the spin parameter, gas fraction and formation redshift of the galaxy and study the importance of numerical parameters as resolution, source distribution and local gas clearing. Results. We find that the UV escape fraction from high-redshift dwarf galaxies that have formed a rotationally supported disc lie between 10 −5 and 0.1. The mass and angular momentum of the galaxy are the most important parameters that determine the escape fraction. We compare our results to previous work and discuss the uncertainties of our models. Conclusions. The low escape fraction we find for high-redshift dwarf galaxies is balanced by their high stellar content, resulting in an efficiency parameter for stars that is only marginally lower than the values found by semi-analytic models of reionisation. We therefore conclude that dwarf galaxies play an important role in cosmic reionisation also after the initial starburst phase, when the gas has settled into a disc.

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Reexamining the Lyman Continuum in Starburst Galaxies Observed with the Hopkins Ultraviolet Telescope

Cited by 106 publications

References 9 publications

First Results from the FUSE Mission

First Results from the FUSE Mission

An Ionizing Ultraviolet Background Dominated by Massive Stars

The escape of ionising radiation from high-redshift dwarf galaxies

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