Lyman-Continuum Emission from Galaxies at z ≃ 3.4

By C. Steidel, M. Pettini, K. Adelberger. 2000

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We report the detection of significant Lyman-continuum flux in the composite spectrum of 29 Lyman-break galaxies (LBGs) with redshifts ⟨z⟩ = 3.40 ± 0.09. After correction for opacity due to intervening absorption using a new composite QSO spectrum evaluated at the same redshift, the ratio of emergent flux density at 1500 Å in the rest frame to that in the Lyman continuum is L(1500 )/L(900 ) = 4.6 ± 1.0. If the relative intensity of the inferred escaping Lyman-continuum radiation is typical of LBGs at z ~ 3 (the galaxies in this sample are drawn from the bluest quartile of LBG spectral energy distributions due to known selection effects), then observed LBGs produce about 5 times more H-ionizing photons per unit comoving volume than QSOs at z ~ 3. The associated contribution to the metagalactic ionizing radiation field is Jν(912 Å) ≈ 1.2 ± 0.3 × 10-21 ergs s-1 cm-2 Hz-1 sr-1 at z ~ 3, very close to most estimates of the radiation field background based on the "proximity effect." A preliminary analysis of the density of faint QSOs in our Lyman-break galaxy survey indicates that the standard extrapolated QSO luminosity function may slightly overpredict the QSO contribution to Jν(912 ) at z ~ 3. We briefly discuss the implications of a galaxy-dominated UV background at high redshifts.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/3e11eb72efb027b2f0416442abe0f19ec2908155

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Citations in the corpus

CONTRASTING GALAXY FORMATION FROM QUANTUM WAVE DARK MATTER, ψDM, WITH ΛCDM, USING PLANCK AND HUBBLE DATA (2015, background): “…since the observed rest-frame UV luminosity (at ∼1500 Å) will also be extinguished by dust, fesc in Equation (17) is the relative escape fraction (Steidel et al. 2001) defined as the absolute escape fraction (the fraction of “ionizing photons” that escapes the galaxy without being absorbed by…”
Escape of Ionizing Radiation from High-Redshift Galaxies (2007, result): “This correction factor is also consistent with other observed estimates of reddening at 1500 (Pettini et al. 1998; Steidel et al. 2001; Shapley et al. 2006).”
Concordance models of reionization: implications for faint galaxies and escape fraction evolution (2012, background): “…from faint galaxies during the epoch of reionization, deep searches for escaping Lyman continuum radiation at lower redshifts do show some evidence for redshift evolution (Steidel et al. 2001; Inoue et al. 2006; Shapley et al. 2006; Cowie et al. 2009; Siana et al. 2010; Nestor et al. 2011).”
The difficulty of getting high escape fractions of ionizing photons from high-redshift galaxies: A view from the FIRE cosmological simulations (2015, background): “Indeed, high escape fractions from 10% up to unity have been found in various samples of Lyman break galaxies (LBGs) and Lyα emitters (LAEs) around z ∼ 3 (e.g. Steidel et al. 2001; Shapley et al. 2006; Vanzella et al. 2012; Nestor et al. 2013).”
Escape of Lyman continuum radiation from local galaxies - Detection of leakage from the young starburst Tol 1247-232 (2013, background): “Also, a few stacked samples at the same redshift show LyC leakage (e.g. Steidel et al. 2001; Nestor et al. 2011), while still others seems to contradict an evolving escape fraction scenario by only yielding upper limits of a few percent at z ∼ 3−4 (Vanzella et al. 2010; Boutsia et al. 2011).”
The transition from Population III to normal galaxies: Lyα and He II emission and the ionising properties of high redshift starburst galaxies (2002, background): “Such measurements are possible in relatively nearby (z >∼ 0.015) and high redshift galaxies (e.g. Leitherer et al. 1995, Deharveng et al. 1997, 2001, Steidel et al. 2001).”
The Direct Detection of Lyman Continuum Emission from Star-forming Galaxies at z~3 (2006, methodology): “Assuming an intrinsic UV-to-Lyman continuum ratio of (L1500/L900)int = 3.0, as in Steidel et al. (2001), we find 〈fesc,rel〉 = 14% for the deep sample – a factor of ∼ 4.5 lower than the value of fesc,rel reported in Steidel et al. (2001).”
ON THE STELLAR POPULATIONS AND EVOLUTION OF STAR-FORMING GALAXIES AT 6.3 < z ⩽ 8.6 (2009, background): “The escape fraction of ionizing photons has been measured at lower redshifts, with fesc< 0.1 atz= 0, fesc= 0.08 atz∼ 1 (Siana et al. 2007), Galaxy Evolution at 6.3< z≤ 8.6 23 and measurements offesc = 0.15–0.6 atz∼ 3 (Steidel et al. 2001; Shapley et al. 2006).”
A DEEP HUBBLE SPACE TELESCOPE SEARCH FOR ESCAPING LYMAN CONTINUUM FLUX AT z ∼ 1.3: EVIDENCE FOR AN EVOLVING IONIZING EMISSIVITY (2010, background): “Steidel et al. (2001) reported the first detection of Lyman continuum (LyC) photons in a stack of 29 z ∼ 3.4 LBG spectra.”
Feedback-regulated star formation and escape of LyC photons from mini-haloes during reionization (2016, methodology): “In observations, the leakage of LyC photons is measured via the relative flux density ratio (FUV/FLyC) between the ionising part of the spectrum at 900 Å and the non-ionising part at 1500Å (Steidel et al. 2001).”
Constraining the Evolution of the Ionizing Background and the Epoch of Reionization with z ∼ 6 Quasars. II. A Sample of 19 Quasars (2005, background): “(15), assuming that the duration of star formation is t∗ = 10 7 yr and the escape fraction is fe = 0.1 (Steidel et al. 2001).”
Detection of high Lyman continuum leakage from four low-redshift compact star-forming galaxies (2016, background): “Over the past, deep imaging studies at z ∼ 3 have produced several candidate leaking galaxies (e.g. Steidel et al. 2001; Iwata et al. 2009; Nestor et al. 2011; Mostardi et al. 2013), whereas other teams have only obtained stringent upper limits (e.g. Vanzella et al. 2010a; Boutsia et al. 2011).”