The Direct Detection of Lyman Continuum Emission from Star-forming Galaxies at z~3

By A. Shapley, C. Steidel, M. Pettini, K. Adelberger, D. Erb. 2006

275 citations recorded by the source corpus.

We present the results of rest-frame UV spectroscopic observations of a sample of 14 z ~ 3 star-forming galaxies in the SSA 22a field. These spectra are characterized by unprecedented depth in the Lyman continuum region. For the first time, we have detected escaping ionizing radiation from individual galaxies at high redshift, with 2 of the 14 objects showing significant emission below the Lyman limit. We also measured the ratio of emergent flux density at 1500 Å to that in the Lyman continuum region, for the individual detections (C49 and D3) and the sample average. If a correction for the average IGM opacity is applied to the spectra of the objects C49 and D3, we find f1500/f900,corr,C49 = 4.5 and f1500/f900,corr,D3 = 2.9. The average emergent flux density ratio in our sample is ⟨f1500/f900,corr⟩ = 22, implying an escape fraction ~4.5 times lower than inferred from the composite spectrum from Steidel and coworkers. If this new estimate is representative of LBGs, their contribution to the metagalactic ionizing radiation field is Jν(900) ~ 2.6 × 10-22 ergs s-1 cm-2 Hz-1 sr-1, comparable to the contribution of optically selected quasars at the same redshift. The sum of the contributions from galaxies and quasars is consistent with recent estimates of the level of the ionizing background at z ~ 3, inferred from the H I Lyα forest optical depth. There is significant variance among the emergent far-UV spectra in our sample, yet the factors controlling the detection or nondetection of Lyman continuum emission from galaxies are not well determined. Because we do not yet understand the source of this variance, significantly larger samples will be required to obtain robust constraints on the galaxy contribution to the ionizing background at z ~ 3 and beyond.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/c4c4a5068555bd9ec3c17498e1ba0e11aee2ad93

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

1. P. Hopkins
2. L. Hernquist
3. R. Dav'e
4. R. Somerville
5. Richard S. Ellis
6. P. V. van Dokkum
7. C. Conroy
8. M. Franx

In Instrumentation

1. P. Hopkins
2. L. Hernquist
3. R. Dav'e
4. P. V. van Dokkum
5. M. Franx
6. Richard S. Ellis
7. R. Somerville
8. C. Conroy

Citations in the corpus

• Fluctuating feedback-regulated escape fraction of ionizing radiation in low-mass, high-redshift galaxies (2017, background): “At higher z, analysis of individual detections or stacked observational samples shows in general a higher fesc (Shapley et al. 2006; Iwata et al. 2009; Vanzella et al. 2010, 2015; Nestor et al. 2013; Mostardi et al. 2013, 2015), sometimes above 50% (Vanzella et al. 2016), even though some studies…”
• Measurements of the UV background at 4.6 < z < 6.4 using the quasar proximity effect (2010, methodology): “Let us then calculateLν0 for each LBG from theirzR band magnitude, assuming they radiate isotropically, are are all at the sameredshift as the quasar, and have a ratio of far-UV to extreme-UV flux, f1500/f900 = 22 (Shapley et al. 2006), as measured forz ∼ 3 LBGs.”
• EXTREME FEEDBACK AND THE EPOCH OF REIONIZATION: CLUES IN THE LOCAL UNIVERSE (2011, background): “…have only yielded upper limits, although significant escaping Lyman continuum emission has been detected in 17 out of a sample of 198 Lyman Break and Lyman α galaxies at z > 3 (Iwata et al. 2009), consistent with earlier results for a smaller sample of Lyman Break galaxies (Shapley et al. 2006).”
• Stellar population effects on the inferred photon density at reionization (2015, background): “Shapley et al. (2006) detected two sources, with a sample-averaged fesc ∼ 14 per cent, while most studies (e.g. Mostardi et al. 2013; Nestor et al. 2013) suggest that LBGs at z ∼ 2 − 4 have a relatively modest fesc of 0.05 to 0.07.”
• Full-data Results of Hubble Frontier Fields: UV Luminosity Functions at z ∼ 6–10 and a Consistent Picture of Cosmic Reionization (2017, background): “Steidel et al. (2001) estimated that the average value of fesc is ∼ 0.1 at z ∼ 3 (see also Shapley et al. 2006; Iwata et al. 2009; Nestor et al. 2011; Japelj et al. 2017).”
• UV Luminosity Functions at z~4, 5, and 6 from the Hubble Ultra Deep Field and Other Deep Hubble Space Telescope ACS Fields: Evolution and Star Formation History (2007, background): “…et al. 1995; Hurwitz et al. 1997; Deharveng et al. 2001; Giallongo et al. 2002; Fernández-Soto et al. 2003; Malkan et al. 2003; Inoue et al. 2005; Shapley et al. 2006; cf. Steidel et al. 2001), and therefore while high-mass stars in galaxies may be efficient producers of…”
• The VIMOS Ultra-Deep Survey: ~10 000 galaxies with spectroscopic redshifts to study galaxy assembly at early epochs 2 < z ≃ 6 (2014, result): “Although these measurements are bs d on a much larger sample covering a larger redshift range, these values are comparable to the observed value of 58± 1 reported by Shapley et al. (2006) atz ∼ 3.”
• OBSERVATIONS OF STARBURST GALAXIES WITH FAR-ULTRAVIOLET SPECTROGRAPHIC EXPLORER: GALACTIC FEEDBACK IN THE LOCAL UNIVERSE (2009, methodology): “We follow the work of Shapley et al. (2006) in estimating both the absolute- and relative-escape fractions.”
• An extreme [O III] emitter at z = 3.2: a low metallicity Lyman continuum source (2015, methodology): “While several systematics can affect the derivation of the LyC signal (e.g., background substraction Shapley et al. 2006), we use different methods of sky subtraction (ABBA method and polynomial fitting with different orders) and they all provide consistent results.”
• Stellar black holes at the dawn of the universe (2011, background): “The escape fraction of ionizing photons emitted by stars was taken to be fesc,∗ = 0.1, which is consistent with the mean observed escape fraction of ionizing photons from starforming galaxies (Shapley et al. 2006) at z = 2−3.”
• The physics of the intergalactic medium (2007, background): “Shapley et al. (2006) report the detection of UV radiation shortward of the Lyman edge in a sample of Lyman Break Galaxies at z ≈ 3 with a corresponding escape fraction of 14%, although the estimate is sensitive to the assumed calibrating population synthesis models and corrections for the IGM…”
• Rest-frame ultraviolet-to-optical spectral characteristics of extremely metal-poor and metal-free galaxies (2011, background): “In fact, the line has been detected from z = 2–3 LBGs but its origin is attributed to the stellar winds of these stars (Shapley et al. 2006; Erb et al. 2010).”
• Magnetized gas clouds can survive acceleration by a hot wind (2014, background): “(ii) Absorption-line spectroscopy of rapidly star-forming galaxies shows ubiquitous evidence for multiphase galactic winds (e.g. Martin 2006; Shapley et al. 2006; Weiner et al. 2009).”
• Using Lyman-α to detect galaxies that leak Lyman continuum (2014, methodology): “LyC emission has been reported in large samples of Lyman break galaxies (LBGs) and Lyα-emitters (LAEs), using both spectroscopic (Steidel et al. 2001; Shapley et al. 2006) techniques and narrowband imaging bluewards of the restframe Lyman limit (Iwata et al. 2009; Nestor et al. 2011, 2013; Mostardi…”
• THE STRUCTURE AND KINEMATICS OF THE CIRCUMGALACTIC MEDIUM FROM FAR-ULTRAVIOLET SPECTRA OF z ≃ 2–3 GALAXIES (2010, background): “It is possible with current generation telescopes and instruments to obtain spectra of relatively high S/N and moderate resolution (e.g., Shapley et al. 2006) in 10-20 hours integration time (i.e.,∼ 10 times longer than most in the current samples).”
• Evolution of the Intergalactic Opacity: Implications for the Ionizing Background, Cosmic Star Formation, and Quasar Activity (2008, methodology): “We have verified that our calculations are numerically consistent with those of Steidel et al. (2001) and Shapley et al. (2006) when the same mean free path, spectral indexes, and completeness are assumed.”
• New Constraints on the Lyman Continuum Escape Fraction at z ~ 1.3 (2007, methodology): “The best limits on the relative escape fraction at z ∼ 1 (Section 5.4) are significantly lower than the average detections at z ∼ 3 (Steidel et al. 2001; Shapley et al. 2006), and yet we find no detections in the present survey.”
• THE ORIGIN AND OPTICAL DEPTH OF IONIZING RADIATION IN THE “GREEN PEA” GALAXIES (2013, background): “This uncertainty translates directly to uncertainties in H ii region and galactic escape fractions (e.g., Shapley et al. 2006; Voges et al. 2008), nebular conditions, and star formation rates.”