Issue |
A&A
Volume 491, Number 1, November III 2008
Diagnostics of interstellar hydrogen in the heliosphere
|
|
---|---|---|
Page(s) | 89 - 111 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361:200809648 | |
Published online | 09 July 2008 |
3D Lyα radiation transfer
III. Constraints on gas and stellar properties of z ~ 3 Lyman break galaxies (LBG) and implications for high-z LBGs and Lyα emitters
1
Geneva Observatory, University of Geneva, 51 Ch. des Maillettes, 1290 Versoix, Switzerland e-mail: anne.verhamme@unige.ch
2
Laboratoire d'Astrophysique de Toulouse-Tarbes, Université de Toulouse, CNRS, 14 Avenue E. Belin, 31400 Toulouse, France
3
Institut d'Astrophysique de Paris, 98bis boulevard Arago, 75014 Paris, France
4
Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
Received:
25
February
2008
Accepted:
22
May
2008
Aims. The aim of our study is to understand the variety of observed Lyα line profiles and strengths in Lyman Break Galaxies (LBGs) and Lyα emitters (LAEs), the physical parameters governing them, and hence derive constraints on the gas and dust content and stellar populations of these objects.
Methods. Using our 3D Lyα radiation transfer code including gas and dust, MCLya, we fit 11 LBGs from the FORS Deep Field with redshifts between 2.8 and 5. A simple geometry of a spherically expanding shell of H I is adopted.
Results. The variety of observed Lyα profiles is successfully reproduced.
Most objects show outflow velocities of Vexp ~ 150-200 km s-1;
two objects are most likely quasi-static.
The radial H I column density ranges from NHI ~ 2 1019 to
7
1020 cm-2.
Our Lyα profile fits yield values of
~ 0.05-0.2 for the
gas extinction.
We find indications for a dust-to-gas ratio higher than the Galactic value,
and for a substantial scatter.
The escape fraction of Lyα photons is found to be determined
primarily by the extinction, and a simple fit formula is proposed. In
this case a measurement of EW(Lyα)obs can yield
, if the
intrinsic Lyα equivalent width is known (or assumed).
Intrinsic EW(Lyα)int ~ 50-100 Å are found for 8/11 objects,
as expected for stellar populations forming constantly over long
periods (
10-100 Myr).
In three cases we found indications of younger populations.
Our model results also allow us to understand observed correlations
between EW(Lyα)obs and other observables such as FWHM(Lyα),
,
SFR(UV) etc. We suggest that most observed trends of Lyα, both in LBGs and LAEs,
are driven by variations of NHI and the accompanying variation of the
dust content. Ultimately, the main parameter responsible for these
variations may be the galaxy mass.
We also show that there is a clear overlap between LBGs and LAEs: at
z ~ 3 approximately 20-25% of the LBGs of Shapley et al. (2003, ApJ, 588, 65) overlap with ~23% of the LAEs of Gronwal
et al. (2007, ApJ, 667, 79).
Radiation transfer and dust effects explain the
increase of the LAE/LBG ratio, and a higher percentage of LBGs with
strong Lyα emission with increasing redshift.
Key words: line: profiles / radiative transfer / galaxies: starburst / galaxies: ISM / galaxies: high-redshift / ultraviolet: galaxies
© ESO, 2008
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.