Ly
                    <i>α</i>
                    EMISSION FROM A LUMINOUS
                    <i>z</i>
                    = 8.68 GALAXY: IMPLICATIONS FOR GALAXIES AS TRACERS OF COSMIC REIONIZATION

Zitrin, Adi; Labbé, Ivo; Belli, Sirio; Bouwens, Rychard; Ellis, Richard S.; Roberts-Borsani, Guido; Stark, Daniel P.; Oesch, Pascal; Smit, Renske

doi:10.1088/2041-8205/810/1/l12

Cited by 273 publications

(367 citation statements)

References 46 publications

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“…-a new analysis of the UV spectrum shows a signal consistent with a direct detection of ionizing photons with S /N > 5 and a relative Lyman continuum escape fraction f esc,rel = 0.64 +1.10 −0.10 ; -the Lyα emission at the systemic redshift, the high Lyα escape fraction, and the non-detection of low-ionization absorption lines are consistent with a low neutral hydrogen column density, while velocity separation of the two Lyα peaks goes againts expectation (e.g., Verhamme et al 2015); -we find a low metallicity (∼1/6 Z ), a strongly subsolar C/O ratio, and a high ionization parameter (log U = −2.25) using a T e -consistent method, in good agreement with previous results at z ∼ 2−3; Zitrin et al 2015;Roberts-Borsani et al 2015;Smit et al 2015), we can speculate that these galaxies have a leakage of ionizing photons. The direct detection of Lyman continuum emission leave little doubt that Ion2 emits ionizing flux.…”

Section: Discussionsupporting

confidence: 91%

An extreme [O III] emitter atz= 3.2: a low metallicity Lyman continuum source

Barros

Vanzella

Amorín

et al. 2015

A&A

188

158

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Aims. Cosmic reionization is an important process occurring in the early epochs of the Universe. However, because of observational limitations due to the opacity of the intergalactic medium to Lyman continuum photons, the nature of ionizing sources is still not well constrained. While high-redshift star-forming galaxies are thought to be the main contributors to the ionizing background at z > 6, it is impossible to directly detect their ionizing emission. Therefore, looking at intermediate redshift analogues (z ∼ 2−4) can provide useful hints about cosmic reionization. Methods. We investigate the physical properties of one of the best Lyman continuum emitter candidate at z = 3.212 found in the GOODS-S/CANDELS field with photometric coverage from the U to the MIPS 24 μm band and VIMOS/VLT and MOSFIRE/Keck spectroscopy. These observations allow us to derive physical properties such as stellar mass, star formation rate, age of the stellar population, dust attenuation, metallicity, and ionization parameter, and to determine how these parameters are related to the Lyman continuum emission. Results. Investigation of the UV spectrum confirms a direct spectroscopic detection of the Lyman continuum emission with S /N > 5.Non-zero Lyα flux at the systemic redshift and high Lyman-α escape fraction ( f esc (Lyα) ≥ 0.78) suggest a low H i column density.The weak C and Si low-ionization absorption lines are also consistent with a low covering fraction along the line of sight. The subsolar abundances are consistent with a young and extreme starburst. The [O iii]λλ4959, 5007+Hβ equivalent width (EW) is one of the largest reported for a galaxy at z > 3 (EW([O iii]λλ4959, 5007 + Hβ) 1600 Å, rest-frame; 6700 Å observed-frame) and the near-infrared spectrum shows that this is mainly due to an extremely strong [O (>10) and high ionization parameter are consistent with prediction from photoionization models in the case of a density-bounded nebula scenario. Furthermore, the EW([O iii]λλ4959, 5007+Hβ) is comparable to recent measurements reported at z ∼ 7−9, in the reionization epoch. We also investigate the possibility of an AGN contribution to explain the ionizing emission but most of the AGN identification diagnostics suggest that stellar emission dominates instead. Conclusions. This source is currently the first high-z example of a Lyman continuum emitter exhibiting indirect and direct evidences of a Lyman continuum leakage and having physical properties consistent with theoretical expectation from Lyman continuum emission from a density-bounded nebula. A low H i column density, low covering fraction, compact star formation activity, and a possible interaction/merging of two systems may contribute to the Lyman continuum photon leakage.

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Section: Discussionsupporting

confidence: 91%

An extreme [O III] emitter atz= 3.2: a low metallicity Lyman continuum source

Barros

Vanzella

Amorín

et al. 2015

A&A

188

158

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“…Indeed, spectroscopic confirmation has recently been obtained for three UV-luminous (M 22 UV~-mag) galaxies at z 7.5 8.7 -with H 25.1 AB selected from CANDELS fields (Roberts-Borsani et al 2016), one at z 8.7 (Zitrin et al 2015) and one at z 11 (GN-z11; Oesch et al 2016). Furthermore, the lower spatial resolution of ground-based observations, compared to HST data, can blend the signal from mergers or from physically unrelated objects and hence make them appear as single sources (e.g., Bowler et al 2017), resulting in an over-estimate of the bright end of the LF and an underestimate of the LF at lower luminosities.…”

Section: = -+mentioning

confidence: 88%

HST Imaging of the Brightest z ∼ 8–9 Galaxies from UltraVISTA: The Extreme Bright End of the UV Luminosity Function

Stefanon

Labbé

Bouwens

et al. 2017

ApJ

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We report on the discovery of three especially bright candidate z 8 phot  galaxies. Five sources were targeted for follow-up with the mag, 5s) NIR data from the UltraVISTA DR3 release, deep ground-based optical imaging from the CFHTLS and Suprime-Cam programs, and Spitzer/IRAC mosaics combining observations from the SMUVS and SPLASH programs. Through the refined spectral energy distributions, which now also include new HyperSuprimeCam g-, r-, i-, z-, and Y-band data, we confirm that 3/5 galaxies have robust z 8.0 8.7phot~-, consistent with the initial selection. The remaining 2/5 galaxies have a nominal z 2 phot~. However, with HST data alone, these objects have increased probability of being at z 9 . We measure mean UV continuum slopes 1.74 0.35 b = - for the three z 8 9 -galaxies, marginally bluer than similarly luminous z 4 6 -in CANDELS but consistent with previous measurements of similarly luminous galaxies at z 7 . The circularized effective radius for our brightest source is 0.9±0.3kpc, similar to previous measurements for a bright z 11 galaxy and bright z 7 galaxies. Finally, enlarging our sample to include the six brightest z 8 LBGs identified over UltraVISTA (i.e., including three other sources from Labbé et al.) we estimate for the first time the volume density of galaxies at the extreme bright end (M 22 UV~-mag) of the z 8 UV luminosity function. Despite this exceptional result, the still large statistical uncertainties do not allow us to discriminate between a Schechter and a double-power-law form.

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“…It is because this ratio has been shown above to be a good discriminant between photoionization by an AGN and star formation, and hence, it will allow a straightforward identification of other line ratios sensitive to the nature of the ionizing source. We favour C iii]λ1908/He ii λ1640 over C iv λ1550/He ii λ1640 in this exercise, because observations of C iv λ1550 can be contaminated by the P-Cygni profile of photospheric stellar emission in young galaxies, while strong C iii]λ1908 emission is now commonly detected in high-redshift galaxies (e.g., Stark et al 2015a;Zitrin et al 2015).…”

Section: Diagnostics Based On the C Iv λ1550 He Ii λ1640 And C Iii]λmentioning

confidence: 99%

“…Pioneering detections of rest-frame ultraviolet and optical emission lines at higher redshift, out to z 6, are also mainly limited to few gravitationally lensed sources (e.g. Fosbury et al 2003;Bayliss et al 2014;Stark et al 2015a,b;Zitrin et al 2015). In the near future, new facilities, such as the James Webb Space Telescope (JWST ) and extremely large ground-based telescopes (ELT), will collect high-quality, rest-frame ultraviolet and optical spectra of thousands of high-redshift galaxies, allowing extensive investigations of early galaxy evolution and of the relation between star formation and black-hole growth.…”

Section: Introductionmentioning

confidence: 99%

Nuclear activity versus star formation: emission-line diagnostics at ultraviolet and optical wavelengths

Feltre¹,

Charlot²,

Gutkin³

2016

Mon. Not. R. Astron. Soc.

285

461

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In the context of observations of the rest-frame ultraviolet and optical emission from distant galaxies, we explore the emission-line properties of photoionization models of active and inactive galaxies. Our aim is to identify new line-ratio diagnostics to discriminate between gas photoionization by active galactic nuclei (AGN) and star formation. We use a standard photoionization code to compute the emission from AGN narrow-line regions and compare this with calculations of the nebular emission from star-forming galaxies achieved using the same code. We confirm the appropriateness of widely used optical spectral diagnostics of nuclear activity versus star formation and explore new diagnostics at ultraviolet wavelengths. We find that combinations of a collisionally excited metal line or line multiplet, such as C iv λλ1548, 1551,iii]λ1892 and [C iii]λ1907+C iii]λ1909, with the He ii λ1640 recombination line are individually good discriminants of the nature of the ionizing source. Diagrams involving at least 3 of these lines allow an even more stringent distinction between active and inactive galaxies, as well as valuable constraints on interstellar gas parameters and the shape of the ionizing radiation. Several line ratios involving Ne-based emission lines, such as [Ne iv]λ2424, [Ne iii]λ3343 and [Ne v]λ3426, are also good diagnostics of nuclear activity. Our results provide a comprehensive framework to identify the sources of photoionization and physical conditions of the ionized gas from the ultraviolet and optical nebular emission from galaxies. This will be particularly useful to interpret observations of high-redshift galaxies with future facilities, such as the James Webb Space Telescope and extremely large ground-based telescopes.

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Ly α EMISSION FROM A LUMINOUS z = 8.68 GALAXY: IMPLICATIONS FOR GALAXIES AS TRACERS OF COSMIC REIONIZATION

Cited by 273 publications

References 46 publications

An extreme [O III] emitter atz= 3.2: a low metallicity Lyman continuum source

An extreme [O III] emitter atz= 3.2: a low metallicity Lyman continuum source

HST Imaging of the Brightest z ∼ 8–9 Galaxies from UltraVISTA: The Extreme Bright End of the UV Luminosity Function

Nuclear activity versus star formation: emission-line diagnostics at ultraviolet and optical wavelengths

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