2008A&A...491...89V


Query : 2008A&A...491...89V

2008A&A...491...89V - Astronomy and Astrophysics, volume 491, 89-111 (2008/11-3)

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.

VERHAMME A., SCHAERER D., ATEK H. and TAPKEN C.

Abstract (from CDS):

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. 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 HI is adopted. The variety of observed Lyα profiles is successfully reproduced. Most objects show outflow velocities of Vexp∼150-200km/s; two objects are most likely quasi-static. The radial HI column density ranges from NHI∼2x1019 to 7x1020cm–2. Our Lyα profile fits yield values of E(B-V)∼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 E(B-V), if the intrinsic Lyα equivalent width is known (or assumed). Intrinsic EW(Lyα)int∼50-100Å are found for 8/11 objects, as expected for stellar populations forming constantly over long periods (>10-100Myr). 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), E(B-V), 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.

Abstract Copyright:

Journal keyword(s): line: profiles - radiative transfer - galaxies: starburst - galaxies: ISM - galaxies: high-redshift - ultraviolet: galaxies

CDS comments: Fig.1 FDF 550 is a misprint for FDF 5550.

Simbad objects: 18

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Number of rows : 18
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
#notes
1 ESO 350-38 Sy2 00 36 52.489 -33 33 17.23   14.31 14.41 13.49   ~ 391 0
2 FDF 1267 ? 01 05 52.10 -25 48 39.2   27.70       ~ 4 0
3 FDF 1337 G 01 05 52.40 -25 48 33.4   25.89       ~ 6 0
4 FDF 2384 G 01 05 56.33 -25 47 37.1   26.02       ~ 5 0
5 FDF 3389 G 01 05 59.92 -25 44 39.9           ~ 6 0
6 NAME FDF reg 01 06 03.6 -25 45 46           ~ 125 0
7 FDF 4454 G 01 06 03.60 -25 45 28.7   27.37       ~ 5 0
8 FDF 4691 EmG 01 06 04.42 -25 48 34.4   25.79       ~ 11 0
9 FDF 5215 G 01 06 06.25 -25 45 04.1   25.53       ~ 9 0
10 FDF 5550 G 01 06 07.51 -25 47 00.4   25.47       ~ 7 0
11 FDF 5812 G 01 06 08.49 -25 44 16.7           ~ 6 0
12 FDF 6557 G 01 06 11.09 -25 47 32.6           ~ 5 0
13 FDF 7539 G 01 06 14.43 -25 47 08.4   25.48       ~ 8 0
14 NAME GOODS Southern Field reg 03 32 28.0 -27 48 30           ~ 1369 1
15 SBSG 0335-052 bCG 03 37 44.06 -05 02 40.2     16.65     ~ 474 1
16 2MASX J08382309+6507160 SBG 08 38 23.093 +65 07 16.05     14.16     ~ 131 2
17 NAME MS 1512-cB58 AGN 15 14 22.2751 +36 36 25.674     20.64   20.35 ~ 324 0
18 NGC 6090 PaG 16 11 40.3 +52 27 21   14.0       ~ 435 2

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