TY - JOUR

T1 - The Keck Lyman Continuum Spectroscopic Survey (KLCS)

T2 - The Emergent Ionizing Spectrum of Galaxies at z ∼ 3

AU - Steidel, Charles C.

AU - Bogosavljević, Milan

AU - Shapley, Alice E.

AU - Reddy, Naveen A.

AU - Rudie, Gwen C.

AU - Pettini, Max

AU - Trainor, Ryan F.

AU - Strom, Allison L.

PY - 2018/12/20

Y1 - 2018/12/20

N2 - 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 , where f 900 is the mean flux density evaluated over the range [880, 910] A. 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 , including a full-sample average = 0.057 ± 0.006. We show that increases monotonically with , 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 f c of the stellar continuum is covered by gas with column density . We show that the composite spectra simultaneously constrain the intrinsic properties of the stars (L 900/L 1500)int along with f c, and f esc,abs, the absolute escape fraction of ionizing photons. We find a sample-averaged f esc,abs = 0.09 - 0.01, with subsamples falling along a linear relation . Using the far-UV luminosity function, the distribution function n(W(Lyα)), and the relationship between and , we estimate the total ionizing emissivity of z ∼ 3 star-forming galaxies with M uv ≤ -19.5, which exceeds the contribution of quasi-stellar objects by a factor of ∼3, and accounts for ∼50% of the total LyC at z ∼ 3 estimated using indirect methods.

AB - 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 , where f 900 is the mean flux density evaluated over the range [880, 910] A. 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 , including a full-sample average = 0.057 ± 0.006. We show that increases monotonically with , 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 f c of the stellar continuum is covered by gas with column density . We show that the composite spectra simultaneously constrain the intrinsic properties of the stars (L 900/L 1500)int along with f c, and f esc,abs, the absolute escape fraction of ionizing photons. We find a sample-averaged f esc,abs = 0.09 - 0.01, with subsamples falling along a linear relation . Using the far-UV luminosity function, the distribution function n(W(Lyα)), and the relationship between and , we estimate the total ionizing emissivity of z ∼ 3 star-forming galaxies with M uv ≤ -19.5, which exceeds the contribution of quasi-stellar objects by a factor of ∼3, and accounts for ∼50% of the total LyC at z ∼ 3 estimated using indirect methods.

KW - cosmology: observations

KW - galaxies: evolution

KW - galaxies: high-redshift

KW - intergalactic medium

KW - ultraviolet: galaxies

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UR - http://www.scopus.com/inward/citedby.url?scp=85059837662&partnerID=8YFLogxK

U2 - 10.3847/1538-4357/aaed28

DO - 10.3847/1538-4357/aaed28

M3 - Article

AN - SCOPUS:85059837662

VL - 869

JO - Astrophysical Journal

JF - Astrophysical Journal

SN - 0004-637X

IS - 2

M1 - 123

ER -