Astrophys. J., 869, 123-123 (2018/December-3)
The Keck Lyman Continuum Spectroscopic survey (KLCS): the emergent ionizing spectrum of galaxies at z ∼ 3.
STEIDEL C.C., BOGOSAVLJEVIC M., SHAPLEY A.E., REDDY N.A., RUDIE G.C., PETTINI M., TRAINOR R.F. and STROM A.L.
Abstract (from CDS):
We present results of a deep spectroscopic survey quantifying the statistics of the escape of ionizing radiation from star-forming galaxies at z ∼ 3. We measure the ratio of ionizing to non-ionizing UV flux density <f900/f1500>obs, where f900 is the mean flux density evaluated over the range [880, 910] Å. We quantify the emergent ratio of ionizing to non-ionizing UV flux density by analyzing high signal-to-noise ratio composite spectra formed from subsamples with common observed properties and numbers sufficient to reduce the statistical uncertainty in the modeled IGM+CGM correction to obtain precise values of <f900/f1500>out, including a full-sample average <f900/f1500>out = 0.057 ± 0.006. We show that <f900/f1500>out increases monotonically with Wλ(Lyα), inducing an inverse correlation with UV luminosity as a by-product. We fit the composite spectra using stellar spectral synthesis together with models of the ISM in which a fraction fc of the stellar continuum is covered by gas with column density NHI. We show that the composite spectra simultaneously constrain the intrinsic properties of the stars (L900/L1500)int along with fc, NHI, E(B-V), and fesc,abs, the absolute escape fraction of ionizing photons. We find a sample-averaged fesc,abs = 0.09 ± 0.01, with subsamples falling along a linear relation <fesc,abs>≃0.75[Wλ(Lyα)/110Å]. Using the far-UV luminosity function, the distribution function n(W(Lyα)), and the relationship between Wλ(Lyα) and <f900/f1500>out, we estimate the total ionizing emissivity of z ∼ 3 star-forming galaxies with Muv <= -19.5, which exceeds the contribution of quasi-stellar objects by a factor of ∼3, and accounts for ∼50% of the total εLyC at z ∼ 3 estimated using indirect methods.
© 2018. The American Astronomical Society.
cosmology: observations - galaxies: evolution - galaxies: high-redshift - intergalactic medium - ultraviolet: galaxies
VizieR on-line data:
<Available at CDS (J/ApJ/869/123): table2.dat table3.dat>
Table 2: SAS-LBG Q0100-ANN N=9, SAS-LBG Q0100-AANN N=3, SAS-LBG Q1009-ANN N=9, SAS-LBG Q1009-AANN N=2.
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