Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Predicting Lyman-alpha escape fractions with a simple observable:
  Lyman-alpha in emission as an empirically calibrated star formation rate
  indicator   Lyman-alpha (Lya) is intrinsically the brightest line emitted from active
galaxies. While it originates from many physical processes, for star-forming
galaxies the intrinsic Lya luminosity is a direct tracer of the Lyman-continuum
(LyC) radiation produced by the most massive O- and early-type B-stars with
lifetimes of a few Myrs. As such, Lya luminosity should be an excellent
instantaneous star formation rate (SFR) indicator. However, its resonant nature
and susceptibility to dust as a rest-frame UV photon makes Lya very hard to
interpret due to the uncertain Lya escape fraction, f$_{esc,Ly\alpha}$. Here we
explore results from the CALYMHA survey at z=2.2, follow-up of Lya emitters
(LAEs) at z=2.2-2.6 and a z~0-0.3 compilation of LAEs to directly measure
f$_{esc,Ly\alpha}$ with H-alpha (Ha). We derive a simple empirical relation
that robustly retrieves f$_{esc,Ly\alpha}$ as a function of Lya rest-frame EW
(EW$_0$): f$_{esc,Ly\alpha}$= 0.0048 EW$_0$[A]$\pm0.05$ and we show that it
constrains a well-defined anti-correlation between ionisation efficiency and
dust extinction in LAEs. Observed Lya luminosities and EW$_0$ are easy
measurable quantities at high redshift, thus making our relation a practical
tool to estimate intrinsic Lya and LyC luminosities under well controlled and
simple assumptions. Our results allow observed Lya luminosities to be used to
compute SFRs for LAEs at z~0-2.6 within 0.2 dex of the Ha dust corrected SFRs.
We apply our empirical SFR(Lya,EW$_0$) calibration to several sources at z>2.6
to find that star-forming LAEs have SFRs typically ranging from 0.1 to 20
M$_{\odot}$/yr and that our calibration might be even applicable for the most
luminous LAEs within the epoch of re-ionisation. Our results imply high
ionisation efficiencies and low dust content in LAEs across cosmic time, and
will be easily tested with future observations with JWST.

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The categories of this paper are: chem-ph
5
The categories of this paper are: gr-qc
9
The categories of this paper are: nlin
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The categories of this paper are: atom-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: funct-an
7
The categories of this paper are: hep-th
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The categories of this paper are: eess
4
The categories of this paper are: cond-mat
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The categories of this paper are: nucl-th
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The categories of this paper are: stat
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The categories of this paper are: mtrl-th
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The categories of this paper are: hep-ex
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The categories of this paper are: cmp-lg
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The categories of this paper are: econ
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The categories of this paper are: adap-org