Recovering the systemic redshift of galaxies from their Lyman alpha line profile

Verhamme, Anne; Garel, Thibault; Ventou, E.; Contini, T.; Bouché, Nicolas; Herenz, Edmund Christian; Richard, Johan; Bacon, Roland; Schmidt, Kasper B.; Maseda, Michael V.; Marino, R. A.; Brinchmann, Jarle; Cantalupo, Sebastiano; Caruana, Joseph; Clément, Benjamin; Diener, C.; Drake, Alyssa B.; Hashimoto, T.; Inami, Hanae; Kerutt, J.; Kollatschny, W.; Leclercq, Floriane; Patrício, Vera; Schaye, Joop; Wisotzki, L.; Zabl, Johannes

doi:10.1093/mnrasl/sly058

Cited by 128 publications

(178 citation statements)

References 48 publications

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“…Our BELLS GALLERY LAEs show Lyα escape fraction ranging between 0.11 and 0.37 (see Table 2), with a mean value and scatter f esc (Lyα)= 0.21 ± 0.11, in between the range of values found for z = 2 − 4 UV-selected galaxies ( f esc (Lyα) ≈ 0.05; e.g., Kornei et al 2010;Cassata et al 2015) and other strong Lyα emitters ( f esc (Lyα) ≈ 0.30; e.g., Nakajima et al 2012;Hashimoto et al 2013;Wardlow et al 2014;Trainor et al 2015;Matthee et al 2016). We recover previous findings that large Lyα escape fraction is associated with small ∆v (Lyα) Verhamme et al 2015;Yang et al 2017;Verhamme et al 2018) and strong EW 0 's (Lyα) (e.g., Trainor et al 2015;Matthee et al 2016;Sobral et al 2017;Yang et al 2017;Izotov et al 2019;McKinney et al 2019), in line with the empirical relation derived by Sobral & Matthee (2019).…”

Section: Other Nebular Linessupporting

confidence: 87%

“…For three LAEs (BG0742+3341, BG0755+3445, and BG1429+1202), however, the Lyα line has its maximum intensity very close to, or even consistent with the systemic velocity (see Section 5.1). These are the ones that show narrower Lyα profiles (230-330 km s −1 FWHM) suggestive of less scatter from low H i column densities and/or that Lyα photons freely escape through a clumpy ISM (e.g., Zheng & Wallace 2014;Verhamme et al 2015Verhamme et al , 2018Claeyssens et al 2019). On the other hand, in addition to the prominent Lyα emission line, BG0201+3228 shows also an underlying broad Lyα absorption (see Figure 2).…”

Section: Lyα Linementioning

confidence: 99%

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Rest-frame UV properties of luminous strong gravitationally lensed Lyα emitters from the BELLS GALLERY Survey

Marques-Chaves

Pérez-Fournón

Shu

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We present deep rest-frame UV spectroscopic observations using the Gran Telescopio Canarias of six gravitationally lensed Lyα emitters (LAEs) at 2.36 < z < 2.82 selected from the BELLS GALLERY survey. By taking the magnifications into account, we show that LAEs can be as luminous as L Lyα 30 × 10 42 erg s −1 and M UV −23 (AB) without invoking an AGN component, in contrast with previous findings. We measure Lyα rest-frame equivalent widths, EW 0 (Lyα), ranging from 16Å to 50Å and Lyα escape fractions, f esc (Lyα), from 10% to 40%. Large EW 0 (Lyα) and f esc (Lyα) are found predominantly in LAEs showing weak low-ionization ISM absorption (EW 0 1Å) and narrow Lyα profiles ( 300 km s −1 FWHM) with their peak close ( 80 km s −1 ) to their systemic redshifts, suggestive of less scatter from low H i column densities that favours the escape of Lyα photons. We infer stellar metallicities of Z/Z 0.2 in almost all LAEs by comparing the P-Cygni profiles of the wind lines N v1240Å and C iv1549Å with those from stellar synthesis models. We also find a trend between M UV and the velocity offset of ISM absorption lines, such as the most luminous LAEs experience stronger outflows. The most luminous LAEs show star formation rates up to 180 M yr −1 , yet they appear relatively blue (β UV −1.8 to −2.0) showing evidence of little dust attenuation (E(B − V) = 0.10 − 0.14). These luminous LAEs may be particular cases of young starburst galaxies that have had no time to form large amounts of dust. If so, they are ideal laboratories to study the early phase of massive star formation, stellar and dust mass growth, and chemical enrichment histories of starburst galaxies at high-z.

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Section: Other Nebular Linessupporting

confidence: 87%

Section: Lyα Linementioning

confidence: 99%

Rest-frame UV properties of luminous strong gravitationally lensed Lyα emitters from the BELLS GALLERY Survey

Marques-Chaves

Pérez-Fournón

Shu

et al. 2019

Monthly Notices of the Royal Astronomical Society

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“…We note that the MACS0940 regions are located below the empirical relation but very close to the 1 σ error so are marginally consistent. We find for both objects a linear slope (Table 1) close to the Verhamme et al (2018) relation (a = 0.9). The linear fit of the two datapoints series was also performed with the emcee package accounting for measurement errors along both directions.…”

Section: Summary and Discussionsupporting

confidence: 72%

“…In Fig. 3 we overplot the empirical relation defined in Verhamme et al (2018) between Lyman-α peak shift and FWHM (not corrected for the line spread function) obtained with large samples on an object-by-object basis. Due to the uncertainties in the systemic redshift, the values of peak shift could be biased by ±13 km s −1 and ±33 km s −1 for SMACS2031 and MACS0940, respectively; but this does not affect our results on variations within the halo and the slope of the correlation.. We can see that the correlation between peak shift and FWHM within each object follows the same empirical relation (in particular the same slope) as the one established on an object-by-object basis.…”

Section: Summary and Discussionmentioning

confidence: 99%

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Spectral variations of Lyman $\alpha$ emission within strongly lensed sources observed with MUSE

Claeyssens

Richard

Blaizot

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We present an analysis of H I Lyman-α emission in deep VLT/MUSE observations of two highly magnified and extended galaxies at z = 3.5 and 4.03, including a newly discovered, almost complete Einstein ring. While these Lyman-α haloes are intrinsically similar to the ones typically seen in other MUSE deep fields, the benefits of gravitational lensing allows us to construct exceptionally detailed maps of Lyman-α line properties at sub-kpc scales. By combining all multiple images, we are able to observe complex structures in the Lyman-α emission and uncover small (∼ 120 km s −1 in Lyman-α peak shift), but significant at > 4 σ, systematic variations in the shape of the Lyman-α line profile within each halo. Indeed, we observe a global trend for the line peak shift to become redder at large radii, together with a strong correlation between the peak wavelength and line width. This systematic intrahalo variation is markedly similar to the object-to-object variations obtained from the integrated properties of recent large samples. Regions of high surface brightness correspond to relatively small line shifts, which could indicate that Lyman-α emission escapes preferentially from regions where the line profile has been less severely affected by scattering of Lyman-α photons.

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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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Recovering the systemic redshift of galaxies from their Lyman alpha line profile

Cited by 128 publications

References 48 publications

Rest-frame UV properties of luminous strong gravitationally lensed Lyα emitters from the BELLS GALLERY Survey

Rest-frame UV properties of luminous strong gravitationally lensed Lyα emitters from the BELLS GALLERY Survey

Spectral variations of Lyman $\alpha$ emission within strongly lensed sources observed with MUSE

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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