Lyman continuum escape fraction of faint galaxies at <i>z</i> ~ 3.3  in the CANDELS/GOODS-North, EGS, and COSMOS  fields with LBC

Grazian, A.; Giallongo, E.; Paris, D.; Boutsia, K.; Dickinson, Mark; Santini, P.; Windhorst, Rogier A.; Jansen, Rolf A.; Cohen, Seth H.; Ashcraft, Teresa; Scarlata, Claudia; Rutkowski, Michael J.; Vanzella, E.; Cusano, F.; Cristiani, S.; Giavalisco, Mauro; Ferguson, Henry C.; Koekemoer, Anton M.; Grogin, Norman A.; Castellano, M.; Fiore, F.; Fontana, A.; Marchi, F.; Pedichini, Fernando; Pentericci, L.; Amorín, R.; Barro, Guillermo; Bonchi, Andrea; Bongiorno, A.; Faber, S. M.; Fumana, M.; Galametz, A.; Guaita, L.; Kocevski, Dale D.; Merlin, E.; Nonino, M.; O’Connell, R. W.; Pilo, S.; Ryan, Russell E.; Sani, E.; Speziali, R.; Testa, V.; Weiner, Benjamin J.; Yan, Haojing

doi:10.1051/0004-6361/201730447

Cited by 100 publications

(86 citation statements)

References 148 publications

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“…The stacked U-and R-band images gives a 1σ lower limit of flux ratio (F R /F U ) obs = 660.7, consistent with the limits derived from the similar deep (≈ 30.2 magnitude) UV imaging for z > 3 LBGs obtained by the Large Binocular Camera (LBC) at the Large Binocular Telescope (Boutsia et al 2011;Grazian et al 2016Grazian et al , 2017. In particular, Grazian et al (2017, hereafter G17) stacked 69 star-forming galaxies at z ∼ 3.3 in the COS-MOS, CANDELS/GOODS-N and EGS fields.…”

Section: Similar Tosupporting

confidence: 83%

HST Imaging of the Ionizing Radiation from a Star-forming Galaxy at z = 3.794

Giavalisco

Vanzella³

et al. 2020

ApJ

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We report on the HST detection of the Lyman-continuum (LyC) radiation emitted by a galaxy at redshift z = 3.794, dubbed Ion1 (Vanzella et al. 2012). The LyC from Ion1 is detected at restframe wavelength λλ 820∼890Å with HST WFC3/UVIS in the F410M band (m 410 = 27.60 ± 0.36 m AB , peak SNR = 4.17 in a circular aperture with radius r = 0.12") and at λλ 700∼830Å with the VLT/VIMOS in the U-band (m U = 27.84 ± 0.19 m AB , peak SNR = 6.7 with a r = 0.6" aperture). A 20-hr VLT/VIMOS spectrum shows low-and high-ionization interstellar metal absorption lines, the P-Cygni profile of C IV and Lyα in absorption. The latter spectral feature differs from what observed in known LyC emitters, which show strong Lyα emission. An HST far-UV color map reveals that the LyC emission escapes from a region of the galaxy that is bluer than the rest, presumably because of lower dust obscuration. The F410M image shows that the centroid of the LyC emission is offset from the centroid of the non-ionizing UV emission by 0.12"±0.03", corresponding to 0.85±0.21 kpc (physical), and that its morphology is likely moderately resolved. These morphological characteristics favor a scenario where the LyC photons produced by massive stars escape from low H I columndensity "cavities" in the ISM, possibly carved by stellar wind and/or supernova. We also collect the VIMOS U-band images of a sample of 107 Lyman-break galaxies with spectroscopic redshifts at 3.40 < z < 3.95, i.e. sampling the LyC, and stack them with inverse-variance weights. No LyC emission is detected in the stacked image, resulting in a 32.5 m AB flux limit (1σ) and an upper limit of absolute LyC escape fraction f abs esc ≤ 0.63%. LyC emitters like Ion1 are very likely at the bright-end of the LyC luminosity function.

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Section: Similar Tosupporting

confidence: 83%

HST Imaging of the Ionizing Radiation from a Star-forming Galaxy at z = 3.794

Giavalisco

Vanzella³

et al. 2020

ApJ

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“…In order to keep the Universe reionised at z > 6, early starforming galaxies would require a significant escape fraction of Lyman continuum (LyC) ionising photons ( f LyC esc ) of up to 15-20% (Ouchi et al 2009;Robertson et al 2015;Atek et al 2015). At lower redshift, where LyC leakage can be inferred directly or indirectly, normal star-forming galaxies struggle to achieve these fractions (Grazian et al 2016(Grazian et al , 2017Guaita et al 2016) and only the most extreme star forming low-mass galaxies such as GPs and LBAs, which appear ubiquitous at z > 6, could make the job (e.g. Schaerer et al 2016;Izotov et al 2018b, and references therein).…”

Section: The Role Of Star Formation and Feedback On The Escape Of Ionmentioning

confidence: 99%

Chemodynamics of green pea galaxies – I. Outflows and turbulence driving the escape of ionizing photons and chemical enrichment

Hogarth

Amorín

Vı́lchez

et al. 2020

Monthly Notices of the Royal Astronomical Society

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We investigate the ionised gas kinematics, physical properties and chemical abundances of SDSS J142947, a Green Pea galaxy at redshift z∼ 0.17 with strong, doublepeak Lyα emission and indirect evidence of Lyman continuum (LyC) leakage. Using high-dispersion spectroscopy, we perform a multi-component analysis of emission-line profiles. Our model consistently fits all lines as a narrow component with intrinsic velocity dispersion σ ∼ 40 km s −1 , and two broader blue-shifted components with σ ∼ 90 km s −1 and ∼ 250 km s −1 . We find electron densities and temperatures, ionisation conditions, and direct O/H and N/O abundances for each component. A highly ionised, metal-poor, young and compact starburst dominates narrow emission, showing evidence of hard radiation fields and elevated N/O. The blue-shifted broader components are consistent with highly turbulent, possibly clumpy ionised gas at the base of a strong photoionised outflow, which accounts for 50% of the integrated emission-line fluxes. The outflow is dense and metal-enriched compared to the H ii regions, with expansion velocities larger than those obtained from UV interstellar absorption lines under standard assumptions. Some of these metals may be able to escape, with outflows loading factors comparable to those found in high-z galaxies of similar SFR/Area. Our findings depict a two-stage starburst picture; hard radiation fields from young star clusters illuminate a turbulent and clumpy ISM that has been eroded by SNe feedback. While UV data suggest an extended Lyα halo with high average H i column density, LyC photons could only escape from SDSS J142947 through low H i density channels or filaments in the ISM approaching density-bounded conditions, traced by outflowing gas.

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“…Meanwhile, the bulk of observational constraints on the average LyC f esc have relied on stacking shallow non-detections for individual galaxies to place stringent upper-limits of f esc < 10% out to z ∼ 4 (e.g., Siana et al 2010;Rutkowski et al 2017;Grazian et al 2017;Japelj et al 2017;Naidu et al 2018). Taken at face value, these studies effectively rule out an average f esc > 10% for M UV −20 sources and put the focus on fainter galaxies, for which no LyC constraints exist yet, as the drivers of reionization.…”

Section: Introductionmentioning

confidence: 99%

Rapid Reionization by the Oligarchs: The Case for Massive, UV-bright, Star-forming Galaxies with High Escape Fractions

Naidu

Tacchella

Mason

et al. 2020

ApJ

289

251

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The protagonists of the last great phase transition of the universe -cosmic reionization -remain elusive. Faint star-forming galaxies are leading candidates because they are found to be numerous and may have significant ionizing photon escape fractions (f esc ). Here we update this picture via an empirical model that successfully predicts latest observations (e.g., the rapid drop in star-formation density (ρ SFR ) at z > 8). We generate an ionizing spectrum for each galaxy in our model and constrain f esc by leveraging latest measurements of the reionization timeline (e.g., Lyα damping of quasars and galaxies at z > 7). Assuming a constant f esc across all sources at z > 6, we find M UV < −13.5 galaxies need f esc =0.21 +0.06 −0.04 to complete reionization. The inferred IGM neutral fraction is [0.9, 0.5, 0.1] at z = [8.2, 6.8, 6.2] ± 0.2, i.e., the bulk of reionization transpires rapidly in 300 Myrs, driven by the z > 8 ρ SFR and favored by high neutral fractions (∼60−90%) measured at z ∼ 7 − 8. Inspired by the emergent sample of Lyman Continuum (LyC) leakers spanning z ∼ 0−6.6 that overwhelmingly displays higher-than-average star-formation surface density (Σ SFR ), we propose a physically motivated model relating f esc to Σ SFR and find f esc ∝ Σ 0.4±0.1 SFR . Since Σ SFR falls by ∼ 2.5 dex between z = 8 and z = 0, our model explains the humble upper limits on f esc at lower redshifts and its required evolution to f esc ∼ 0.2 at z > 6. Within this model, strikingly, <5% of galaxies with M UV < −18 and log(M /M ) > 8 (the 'oligarchs') account for 80% of the reionization budget -a stark departure from the canonical 'democratic' reionization led by copious faint sources. In fact, faint sources (M UV >−16) must be relegated to a limited role in order to ensure high neutral fractions at z = 7 − 8. Shallow faint-end slopes of the UV luminosity function (α UV > −2) and/or f esc distributions skewed toward massive galaxies produce the required late and rapid reionization. We predict LyC leakers like COLA1 (z = 6.6, f esc ∼ 30%, M UV = −21.5) become increasingly common towards z ∼ 6 and that the drivers of reionization do not lie hidden across the faint-end of the luminosity function, but are already known to us.

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Lyman continuum escape fraction of faint galaxies at z ~ 3.3 in the CANDELS/GOODS-North, EGS, and COSMOS fields with LBC

Cited by 100 publications

References 148 publications

HST Imaging of the Ionizing Radiation from a Star-forming Galaxy at z = 3.794

HST Imaging of the Ionizing Radiation from a Star-forming Galaxy at z = 3.794

Chemodynamics of green pea galaxies – I. Outflows and turbulence driving the escape of ionizing photons and chemical enrichment

Rapid Reionization by the Oligarchs: The Case for Massive, UV-bright, Star-forming Galaxies with High Escape Fractions

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