The redshift evolution of rest-UV spectroscopic properties to <i>z</i> ∼ 5

Pahl, Anthony; Shapley, Alice E.; Faisst, Andreas L.; Capak, P.; Du, Xinnan; Reddy, Naveen A.; Laursen, Peter; Topping, Michael W.

doi:10.1093/mnras/staa355

Cited by 40 publications

(43 citation statements)

References 85 publications

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“…Accordingly, f c varies between zero and one and the 'holes' are free of both H I and dust. This model is consistent with correlations found between Lyα emission strength and lowionization interstellar absorption strength in star-forming galaxies at intermediate redshifts (Shapley et al 2003;Steidel et al 2010;Du et al 2018;Pahl et al 2020). S18 defines the attenuated observed spectrum as…”

Section: F Esc Abssupporting

confidence: 91%

An uncontaminated measurement of the escaping Lyman continuum at z ∼ 3

Pahl

Shapley

Steidel

et al. 2021

Monthly Notices of the Royal Astronomical Society

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104

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Observations of reionization-era analogs at z ∼ 3 are a powerful tool for constraining reionization. Rest-ultraviolet observations are particularly useful, in which both direct and indirect tracers of ionizing-photon production and escape can be observed. We analyse a sample of 124 z ∼ 3 galaxies from the Keck Lyman Continuum Spectroscopic Survey, with sensitive spectroscopic measurements of the Lyman continuum region. We present a method of removing foreground contamination from our sample using high-resolution, multi-band Hubble Space Telescope imaging. We re-measure the global properties of the cleaned sample of 13 individually-detected Lyman continuum sources and 107 individually-undetected sources, including a sample-averaged absolute escape fraction of fesc, abs = 0.06 ± 0.01 and a sample-averaged ratio of ionizing to non-ionizing ultraviolet flux density of 〈f900/f1500〉out = 0.040 ± 0.006, corrected for attenuation from the intergalactic and circumgalactic media. Based on composite spectra, we also recover a strong positive correlation between 〈f900/f1500〉out and Lyα equivalent width (Wλ(Ly$\rm \alpha$)) and a negative correlation between 〈f900/f1500〉out and UV luminosity. As in previous work, we interpret the relationship between 〈f900/f1500〉out and Wλ(Ly$\rm \alpha$) in terms of the modulation of the escape of ionizing radiation from star-forming galaxies based on the covering fraction of neutral gas. We also use a Wλ(Ly$\rm \alpha$)-weighted 〈f900/f1500〉out to estimate an ionizing emissivity from star-forming galaxies at z ∼ 3 as εLyC ≃ 5.5 × 1024 erg s−1 Hz−1 Mpc−3. This estimate, evaluated using the uncontaminated sample of this work, affirms that the contribution of galaxies to the ionizing background at z ∼ 3 is comparable to that of active galactic nuclei.

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Section: F Esc Abssupporting

confidence: 91%

An uncontaminated measurement of the escaping Lyman continuum at z ∼ 3

Pahl

Shapley

Steidel

et al. 2021

Monthly Notices of the Royal Astronomical Society

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104

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“…Most importantly, all the samples that we used as comparison at lower redshift (Shapley et al 2003;Steidel et al 2010;Talia et al 2017;Marchi et al 2019) also mainly include mainsequence galaxies that largely overlap in stellar mass with our sample, with differences in SFR and M FUV that are compatible with the evolving main-sequence from z ∼ 2 to z ∼ 5. In particular, at z ∼ 2.3, the sample in Steidel et al (2010) covers masses 10 9 < M * < 10 11 M , 10 < SFR < 100 M yr −1 , and far-UV absolute magnitudes −22.5 < M FUV < −19.7 (see Erb et al 2006a,b), with ranges that are very similar to those reported by Du et al (2018) and Pahl et al (2020). The 800 galaxies at z ∼ 3 that are stacked in Shapley et al (2003) have −22.6 < M FUV < −20.3, with an average M FUV ∼ −21.4, and have SFRs 25 < SFR < 50 M yr −1 .…”

Section: Associated Optical/nir and Other Multiwavelength Datasupporting

confidence: 66%

“…However, we note that only in galaxies with the smallest ∆v Lyα might the red peak be appreciably reduced (and possibly shifted by the ISM absorption to redder wavelengths): in these 20% of the cases, it is possible in principle that we underestimate the Lyα flux and overestimate the ∆v Lyα (although it is unlikely that this is a systematic effect: these galaxies are already the galaxies with the largest f esc (Lyα) and the smallest ∆v Lyα ). Pahl et al (2020) have shown that the red peak in a composite of ∼200 z ∼ 5 galaxies is only marginally affected by the IGM absorption.…”

Section: Spectroscopic Data and Measurementsmentioning

confidence: 99%

The ALPINE-ALMA [CII] survey

Cassata

Morselli

Faisst

et al. 2020

A&A

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Context. The Lyman-α line in the ultraviolet (UV) and the [CII] line in the far-infrared (FIR) are widely used tools to identify galaxies in the early Universe and to obtain insights into interstellar medium (ISM) properties in high-redshift galaxies. By combining data obtained with ALMA in band 7 at ∼320 GHz as part of the ALMA Large Program to INvestigate [CII] at Early Times (ALPINE) with spectroscopic data from DEIMOS at the Keck Observatory, VIMOS and FORS2 at the Very Large Telescope, we assembled a unique sample of 53 main-sequence star-forming galaxies at 4.4 < z < 6 in which we detect both the Lyman-α line in the UV and the [CII] line in the FIR. Aims. The goal of this paper is to constrain the properties of the Lyα emission in these galaxies in relation to other properties of the ISM. Methods. We used [CII], observed with ALMA, as a tracer of the systemic velocity of the galaxies, and we exploited the available optical spectroscopy to obtain the Lyα-[CII] and ISM-[CII] velocity offsets. Results. We find that 90% of the selected objects have Lyα-[CII] velocity offsets in the range 0 < ΔvLyα − [CII] < 400 km s−1, in line with the few measurements available so far in the early Universe, and significantly smaller than those observed at lower redshifts. At the same time, we observe ISM-[CII] offsets in the range −500 < ΔvISM−[CII] < 0 km s−1, in line with values at all redshifts, which we interpret as evidence for outflows in these galaxies. We find significant anticorrelations between ΔvLyα−[CII] and the Lyα rest-frame equivalent width EW0(Lyα) (or equivalently, the Lyα escape fraction fesc(Lyα)): galaxies that show smaller ΔvLyα−[CII] have larger EW0(Lyα) and fesc(Lyα). Conclusions. We interpret these results in the framework of available models for the radiative transfer of Lyα photons. According to the models, the escape of Lyα photons would be favored in galaxies with high outflow velocities, producing large EW0(Lyα) and small ΔvLyα-[CII], in agreement with our observations. The uniform shell model would also predict that the Lyα escape in galaxies with slow outflows (0 < vout < 300 km s−1) is mainly determined by the neutral hydrogen column density (NHI) along the line of sight, while the alternative model by Steidel et al. (2010, ApJ, 717, 289) would more highly favor a combination of NHI at the systemic velocity and covering fraction as driver of the Lyα escape. We suggest that the increase in Lyα escape that is observed in the literature between z ∼ 2 and z ∼ 6 is not due to a higher incidence of fast outflows at high redshift, but rather to a decrease in average NHI along the line of sight, or alternatively, a decrease in HI covering fraction.

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“…Other sources can have a very bright Lyman α line, which has a lot of weight in the determination of the redshift. While [CII] traces the gas in the galaxy and is very close to the systemic velocity, Lyman α radiative transfer is complex and can produce significant offsets (e.g., Steidel et al 2010;Faisst et al 2016;Matthee et al 2017Matthee et al , 2019Carniani et al 2018b;Verhamme et al 2018;Pahl et al 2020;Behrens et al 2019). A complete analysis of the origins of these offsets is presented in Faisst et al (2020).…”

Section: Offsets Between Optical and [Cii] Redshiftsmentioning

confidence: 99%

The ALPINE-ALMA [CII] survey: Data processing, catalogs, and statistical source properties

Béthermin

Fudamoto

Ginolfi

et al. 2020

A&A

199

154

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The Atacama Large Millimeter Array (ALMA) Large Program to INvestigate [CII] at Early times (ALPINE) targets the [CII] 158 μm line and the far-infrared continuum in 118 spectroscopically confirmed star-forming galaxies between z = 4.4 and z = 5.9. It represents the first large [CII] statistical sample built in this redshift range. We present details regarding the data processing and the construction of the catalogs. We detected 23 of our targets in the continuum. To derive accurate infrared luminosities and obscured star formation rates (SFRs), we measured the conversion factor from the ALMA 158 μm rest-frame dust continuum luminosity to the total infrared luminosity (LIR) after constraining the dust spectral energy distribution by stacking a photometric sample similar to ALPINE in ancillary single-dish far-infrared data. We found that our continuum detections have a median LIR of 4.4 × 1011 L⊙. We also detected 57 additional continuum sources in our ALMA pointings. They are at a lower redshift than the ALPINE targets, with a mean photometric redshift of 2.5 ± 0.2. We measured the 850 μm number counts between 0.35 and 3.5 mJy, thus improving the current interferometric constraints in this flux density range. We found a slope break in the number counts around 3 mJy with a shallower slope below this value. More than 40% of the cosmic infrared background is emitted by sources brighter than 0.35 mJy. Finally, we detected the [CII] line in 75 of our targets. Their median [CII] luminosity is 4.8 × 108 L⊙ and their median full width at half maximum is 252 km s−1. After measuring the mean obscured SFR in various [CII] luminosity bins by stacking ALPINE continuum data, we find a good agreement between our data and the local and predicted SFR–L[CII] relations.

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The redshift evolution of rest-UV spectroscopic properties to z ∼ 5

Cited by 40 publications

References 85 publications

An uncontaminated measurement of the escaping Lyman continuum at z ∼ 3

An uncontaminated measurement of the escaping Lyman continuum at z ∼ 3

The ALPINE-ALMA [CII] survey

The ALPINE-ALMA [CII] survey: Data processing, catalogs, and statistical source properties

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