Strong Lyman continuum emitting galaxies show intense C IV <i>λ</i>1550 emission

Schaerer, D.; Izotov, Y. I.; Worseck, G.; Berg, Danielle A.; Chisholm, John; Jaskot, Anne; Nakajima, Kengo; Ravindranath, Swara; Thuan, T. X.; Verhamme, Anne

doi:10.1051/0004-6361/202243149

Cited by 60 publications

(65 citation statements)

References 46 publications

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“…At low redshift, Jaskot & Oey (2013) have examined how hard ionizing radiation can influence emission line diagnostics of the optical depth of LyC radiation in green pea galaxies, a class of strong emission line galaxies now known to contain LyC emitters. Schaerer et al (2022) have recently discovered intense C iv and He ii λ1640 emission lines in three low-z strong LyC emitters, ( f esc > 0.1), with UV properties similar to the high-z galaxies mentioned above. They proposed that strong C iv λ1550 emission indicates high LyC escape fractions.…”

Section: Introductionmentioning

confidence: 71%

“…They proposed that strong C iv λ1550 emission indicates high LyC escape fractions. Furthermore, they also estimated that strong LyC leakers do not have harder ioniz-ing spectra than nonleakers, and that the presence of strong C iv and He ii in the spectra of LyC leakers could be primarily due to a high ionizing photon production (Schaerer et al 2022).…”

Section: Introductionmentioning

confidence: 99%

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No correlation of the Lyman continuum escape fraction with spectral hardness

Marques-Chaves

Amorín

Atek

et al. 2022

A&A

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The properties that govern the production and escape of hydrogen-ionizing photons (Lyman continuum, LyC; with energies >13.6 eV) in starforming galaxies are still poorly understood, but they are key to identifying and characterizing the sources that reionized the Universe. Here we empirically explore the relation between the hardness of ionizing radiation and the LyC leakage in a large sample of low-z star-forming galaxies from the recent Hubble Space Telescope Low-z Lyman Continuum Survey. Using Sloan Digital Sky Survey stacks and deep XShooter observations, we investigate the hardness of the ionizing spectra (Q He + /Q H ) between 54.4 eV (He + ) and 13.6 eV (H) from the optical recombination lines He ii 4686Å and Hβ 4861Å for galaxies with LyC escape fractions spanning a wide range, f esc (LyC) 0 − 90%. We find that the observed intensity of He ii/Hβ is primarily driven by variations in the metallicity, but is not correlated with LyC leakage. Both very strong (< f esc (LyC)> 0.5) and nonleakers (< f esc (LyC)> 0) present similar observed intensities of He ii and Hβ at comparable metallicity, between 0.01 and 0.02 for 12 + log(O/H) > 8.0 and < 8.0, respectively. Our results demonstrate that Q He + /Q H does not correlate with f esc (LyC), which implies that strong LyC emitters do not show harder ionizing spectra than nonleakers at similar metallicity.

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Section: Introductionmentioning

confidence: 71%

Section: Introductionmentioning

confidence: 99%

No correlation of the Lyman continuum escape fraction with spectral hardness

Marques-Chaves

Amorín

Atek

et al. 2022

A&A

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“…Interestingly, rest-frame UV spectroscopy of LyC leakers at 𝑧 < 0.7 has also resulted in the detection of strong C emission in all galaxies with 𝑓 esc > 0.1 (Schaerer et al 2022), with some of the highest EW 0 (C ) seen in low-𝑧 star-forming galaxies. The EW 0 (C ) for a majority of their LyC leaking sources are comparable to that of our stacked spectrum.…”

Section: Comparison With Literaturementioning

confidence: 99%

“…Vanzella et al 2016). Schaerer et al (2022) interpreted their results with an elevated level of 𝜉 ion and the presence of densitybound H regions. At low gas-phase metallicities, these conditions increase both the C luminosity as well as the C /C ] line ratio.…”

Section: Introductionmentioning

confidence: 98%

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Strong C IV emission from star-forming galaxies: a case for high Lyman continuum photon escape

Saxena,

Cryer,

Ellis

et al. 2022

Preprint

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Finding reliable indicators of Lyman continuum (LyC) photon leakage from galaxies is essential in order to infer their escape fraction in the epoch of reionisation, where direct measurements of LyC flux are impossible. To this end, here we investigate whether strong C 𝜆𝜆1548, 1550 emission in the rest-frame UV spectra of galaxies traces conditions ripe for ample production and escape of LyC photons. We compile a sample of 19 star-forming galaxies in the redshift range 𝑧 = 3.1 − 4.6 from the VANDELS survey that exhibit strong C emission, producing a stacked spectrum where all major rest-UV emission lines are clearly detected. Best-fitting spectral energy distribution models containing both stellar and nebular emission suggest the need for low stellar metallicities (𝑍 = 0.1−0.2 𝑍 ), young stellar ages (log(age/yr) = 6.1−6.5), a high ionisation parameter (log 𝑈 = −2) and little to no dust attenuation (𝐸 (𝐵 − 𝑉) = 0.00 − 0.01). However, these models are unable to fully reproduce the observed C and He line strengths. We find that the Ly𝛼 line in the stacked spectrum is strong and peaks close to the systemic velocity, features that are indicative of significant LyC photon leakage along the line-of-sight. The covering fractions of low-ionisation interstellar absorption lines are also low implying LyC escape fraction in the range ≈ 0.05 − 0.30, with signatures of outflowing gas. Finally, C /C ] ratios of > 0.75 for a subset of individual galaxies with reliable detections of both lines are also consistent with physical conditions that enable significant LyC leakage. Overall, we report that multiple spectroscopic indicators of LyC leakage are present in the stacked spectrum of strong C emitting galaxies, potentially making C an important tracer of LyC photon escape at 𝑧 > 6.

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The MAGPI Survey: Insights into the Lyα line widths and the size of ionised bubbles at the edge of cosmic reionisation

Mukherjee,

Zafar,

Nanayakkara

et al. 2024

Publ. Astron. Soc. Aust.

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We present spectroscopic properties of 22 Ly $\alpha$ emitters (LAEs) at $z = 5.5 - 6.6$ with Ly $\alpha$ luminosity $\mathrm{log}( L_{\mathrm{Ly}\alpha} \, [\mathrm{erg} \, \mathrm{s}^{-1}]) = 42.4 - 43.5 $ , obtained using VLT/MUSE as part of the Middle Ages Galaxy Properties with Integral Field Spectroscopy (MAGPI) survey. Additionally, we incorporate broad-band photometric data from the Subaru Hyper Suprime-Cam (HSC) Wide layer for 17 LAEs in our sample. The HSC-y band magnitudes show that our LAEs are UV-bright, with rest-frame absolute UV magnitudes $ -19.74 \leq \mathrm{M}_{\mathrm{UV}} \leq -23.27$ . We find that the Ly $\alpha$ line width increases with Ly $\alpha$ luminosity, and this trend becomes more prominent at $z \gt 6$ where Ly $\alpha$ lines become significantly broadened ( $\gtrsim+260 \, \mathrm{km}\, \mathrm{s}^{-1}$ ) at luminosities $\mathrm{log}( L_{\mathrm{Ly}\alpha} \, [\mathrm{erg} \, \mathrm{s}^{-1}]) \gt 43 $ . This broadening is consistent with previous studies, suggesting that these sources are located inside larger ionised bubbles. We observe a slightly elevated ionising photon production efficiency estimated for LAEs at $z \gt 6$ , which indicates that younger galaxies could be producing more ionising photons per UV luminosity. A tentative anti-correlation between ionising photon production efficiency and Ly $\alpha$ rest-frame equivalent width is noticed, which could indicate a time delay between production and escape of ionising photon primarily due to supernovae activity. Furthermore, we find a positive correlation between radius of ionised regions and Ly $\alpha$ line width, which again suggests that large ionised bubbles are created around these LAEs, which are allowing them to self-shield from the scattering effects of the intergalactic medium (IGM). We also detect two very closely separated LAEs at $z = 6.046$ (projected spatial distance between the cores is 15.92 kpc). This is the LAE pair with the smallest separation ever discovered in the reionisation epoch. The size of their respective bubbles suggests that they likely sit inside a common large ionised region. Such a closely separated LAE pair increases the size of ionised bubble, potentially allowing a boosted transmission of Ly $\alpha$ through neutral IGM and also supports an accelerated reionisation scenario.

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Strong Lyman continuum emitting galaxies show intense C IV λ1550 emission

Cited by 60 publications

References 46 publications

No correlation of the Lyman continuum escape fraction with spectral hardness

No correlation of the Lyman continuum escape fraction with spectral hardness

Strong C IV emission from star-forming galaxies: a case for high Lyman continuum photon escape

The MAGPI Survey: Insights into the Lyα line widths and the size of ionised bubbles at the edge of cosmic reionisation

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Strong Lyman continuum emitting galaxies show intense C IV λ1550 emission

Cited by 60 publications

References 46 publications

No correlation of the Lyman continuum escape fraction with spectral hardness

No correlation of the Lyman continuum escape fraction with spectral hardness

Strong C IV emission from star-forming galaxies: a case for high Lyman continuum photon escape

The MAGPI Survey: Insights into the Lyα line widths and the size of ionised bubbles at the edge of cosmic reionisation

Contact Info

Product

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Strong Lyman continuum emitting galaxies show intense C IV λ1550 emission