Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Stellar populations and Lya emission in two lensed z>~6 galaxies   We present an analysis of two strongly lensed galaxies at z=6.56 and z ~ 7
for which multi-band photometric and spectroscopic observations are available.
For one source the data include recent HST and Spitzer observations. Using an
SED fitting technique considering a number of parameters we attempt to
constrain the properties of their stellar populations and their intrinsic Lya
emission. The following main results are obtained for the individual galaxies:
* Triple arc in Abell 2218: The most likely redshift of this source is z ~
6.0-7.2. SED fits indicate generally a low extinction but do not strongly
constrain the star formation (SF) history. Best fits have typical ages of ~3 to
400 Myr. The apparent 4000Ang break observed recently from combination of
IRAC/Spitzer and HST observations, can also equally well be reproduced with the
template of a young (~3-5 Myr). The estimated SFR is typically ~1 Msun/yr, in
agreement with previous estimates. The unknowns on the age and star formation
history could easily explain the apparent absence of Lya in this galaxy. *
Abell 370 HCM 6A: The available Lya and continuum observations indicate two
possible solutions: 1) a young burst or ongoing constant SF with non-negligible
extinction or 2) a composite young+"old" stellar population. In the first case
one obtains a best fit A_V ~ 0.5-1.8 at a 1 sigma level. In consequence we
obtain SFR ~ 11-41 Msun/yr, higher than earlier estimates, and we estimate a
fairly high total luminosity (L ~ (1-4)*10^{11} Lsun) for this galaxy, in the
range LIRG. A Lya transmission of ~23-90% is estimated from our best fit
models. Other properties remain largely unconstrained. In case of composite
stellar populations the SFR, mass, and luminosity estimate is lower. The two
scenarios may be distinguishable with IRAC/Spitzer observations at 3.6 and 4.5
micron.

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The categories of this paper are: cs
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The categories of this paper are: supr-con
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The categories of this paper are: math
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The categories of this paper are: gr-qc
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The categories of this paper are: alg-geom
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The categories of this paper are: q-alg
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The categories of this paper are: comp-gas
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The categories of this paper are: bayes-an
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The categories of this paper are: q-bio
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The categories of this paper are: acc-phys
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The categories of this paper are: hep-ph
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The categories of this paper are: nlin
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The categories of this paper are: mtrl-th
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The categories of this paper are: eess
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The categories of this paper are: hep-th
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The categories of this paper are: nucl-th