XXIVth IAP Colloquium

Far away : light in the young universe at redshift beyond three

Monday July 7 to Friday July 11, 2008

List of TEPLITZ's Presentation(s) ( Updated 20/01/2011 15:16:39 )

Precise if your presentation is oral or a poster : oral
Title of your presentation : The Lyman Continuum Escape Fraction at Moderate Redshift

Massive starbursts may have played a dominant role in the reionization
of the Universe. Their contribution depends in part upon the fraction
of ionizing radiation that escapes from the intrinsic opacity of
galaxies below the Lyman limit. Current surveys suggest that the
escape fraction is low in all but 15-25% of galaxies, even among young
starbursts. Direct measurement of the escape fraction, f_esc, is
impossible at the epoch of reionization, because intervening absorbers
make the IGM opaque to Lyman continuum photons. Instead, f_esc must
be measured at lower redshifts in objects that are analogous to the
galaxies responsible for reionization. Targeting redshifts near unity
provides a substantial population of such sources, and allows
extremely strong constraints to be placed on f_esc.

We present the most recent results of a comprehensive HST survey to
measure or limit the value of f_esc in starbursts near z=1. We have
obtained far-ultraviolet imaging of the Hubble Deep Field, the
Ultradeep Field, and a target sample of z=1.3 starburts, using the
Solar Blind Channel (SBC) of the ACS onboard HST. The data constrains the
value of relative escape fraction (f_750/f_1500) to be at most 5% in
luminous starbursts at z=1.3. The wider survey also shows that the
escape fraction does not rise significantly in less luminous objects.
Our latest survey uses SBC spectroscopy of z=0.7 galaxies to search
for rare, high f_esc objects, and we will present the intial
results for observations obtained in February 2008.

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