The dominant origin of diffuse Lyα halos around Lyα emitters explored by spectral energy distribution fitting and clustering analysis

Kusakabe, Haruka; Shimasaku, Kazuhiro; Momose, Rieko; Ouchi, Masami; Nakajima, Kengo; Hashimoto, T.; Harikane, Yuichi; Silverman, John D.; Capak, P.

doi:10.1093/pasj/psz029

Cited by 21 publications

(22 citation statements)

References 181 publications

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“…This succession of events is a possible explanation of the observed Lyα haloes. Kusakabe et al (2019) investigated the origin of the Lyα haloes using the stacking method and argued that this mechanism is dominant in M UV > −20 LAEs at z 2 (see their discussion). The single-peaked and red-asymmetric spectral profile of most observed Lyα lines at z > 3 can be explained by radiative transfer models as a signature of galactic outflows (Dijkstra et al 2006;Verhamme et al 2006).…”

Section: Scattering From a Central Source In An Outflowing Mediummentioning

confidence: 99%

The MUSE Hubble Ultra Deep Field Survey

Leclercq

Bacon

Verhamme

et al. 2020

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We present spatially resolved maps of six individually-detected Lyman α haloes (LAHs) as well as a first statistical analysis of the Lyman α (Lyα) spectral signature in the circum-galactic medium of high-redshift star-forming galaxies (−17.5 > MUV > −21.5) using the Multi-Unit Spectroscopic Explorer. Our resolved spectroscopic analysis of the LAHs reveals significant intrahalo variations of the Lyα line profile. Using a three-dimensional two-component model for the Lyα emission, we measured the full width at half maximum (FWHM), the peak velocity shift, and the asymmetry of the Lyα line in the core and in the halo of 19 galaxies. We find that the Lyα line shape is statistically different in the halo compared to the core (in terms of width, peak wavelength, and asymmetry) for ≈40% of our galaxies. Similarly to object-by-object based studies and a recent resolved study using lensing, we find a correlation between the peak velocity shift and the width of the Lyα line both at the interstellar and circum-galactic scales. This trend has been predicted by radiative transfer simulations of galactic winds as a result of resonant scattering in outflows. While there is a lack of correlation between the spectral properties and the spatial scale lengths of our LAHs, we find a correlation between the width of the line in the LAH and the halo flux fraction. Interestingly, UV bright galaxies (MUV < −20) show broader, more redshifted, and less asymmetric Lyα lines in their haloes. The most significant correlation found is for the FWHM of the line and the UV continuum slope of the galaxy, suggesting that the redder galaxies have broader Lyα lines. The generally broad and red line shapes found in the halo component suggest that the Lyα haloes are powered either by scattering processes through an outflowing medium, fluorescent emission from outflowing cold clumps of gas, or a mix of both. Considering the large diversity of the Lyα line profiles observed in our sample and the lack of strong correlation, the interpretation of our results is still broadly open and underlines the need for realistic spatially resolved models of the LAHs.

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Section: Scattering From a Central Source In An Outflowing Mediummentioning

confidence: 99%

The MUSE Hubble Ultra Deep Field Survey

Leclercq

Bacon

Verhamme

et al. 2020

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“…In particular, it is not clear how they relate to the UV luminosities of their associated galaxies (e.g. Leclercq et al 2017;Kusakabe et al 2019), to what extent they are associated to star formation (e.g. Yajima et al 2012, their Figure 12), or whether the nature of this association could vary with redshift.…”

Section: Extended Lyα Emissionmentioning

confidence: 99%

The MUSEHubbleUltra Deep Field Survey

Kusakabe

Blaizot

Garel

et al. 2020

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Context. The Lyα emitter (LAE) fraction, X LAE , is a potentially powerful probe of the evolution of the intergalactic neutral hydrogen gas fraction. However, uncertainties in the measurement of X LAE are still debated. Aims. Thanks to deep data obtained with the integral field spectrograph MUSE (Multi-Unit Spectroscopic Explorer), we can measure the evolution of the LAE fraction homogeneously over a wide redshift range of z ≈ 3-6 for UV-faint galaxies (down to UV magnitudes of M 1500 ≈ −17.75). This is significantly fainter than in former studies (M 1500 ≤ −18.75), and allows us to probe the bulk of the population of high-redshift star-forming galaxies. Methods. We construct a UV-complete photometric-redshift sample following UV luminosity functions and measure the Lyα emission with MUSE using the latest (second) data release from the MUSE Hubble Ultra Deep Field Survey. Results. We derive the redshift evolution of X LAE for M 1500 ∈ [−21.75; −17.75] for the first time with a equivalent width range EW(Lyα) ≥ 65 Å and find low values of X LAE 30% at z 6. The best fit linear relation is X LAE = 0.07 +0.06 −0.03 z − 0.22 +0.12 −0.24 . For M 1500 ∈ [−20.25; −18.75] and EW(Lyα) ≥ 25 Å, our X LAE values are consistent with those in the literature within 1σ at z 5, but our median values are systematically lower than reported values over the whole redshift range. In addition, we do not find a significant dependence of X LAE on M 1500 for EW(Lyα) ≥ 50 Å at z ≈ 3-4, in contrast with previous work. The differences in X LAE mainly arise from selection biases for Lyman Break Galaxies (LBGs) in the literature: UV-faint LBGs are more easily selected if they have strong Lyα emission, hence X LAE is biased towards higher values when those samples are used. Conclusions. Our results suggest either a lower increase of X LAE towards z ≈ 6 than previously suggested, or even a turnover of X LAE at z ≈ 5.5, which may be the signature of a late or patchy reionization process. We compared our results with predictions from a cosmological galaxy evolution model. We find that a model with a bursty star formation (SF) can reproduce our observed LAE fractions much better than models where SF is a smooth function of time.

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“…To obtain accurate estimates of the total Lyα emission, we used the Lyα fluxes and EWs recomputed by applying the CoG method (e.g., Sect. 5.3 of Leclercq et al 2017) accounting for the likely extended emission whose origin is currently a subject of intense discussion (e.g., Wisotzki et al 2016;Leclercq et al 2017;Kusakabe et al 2019). Given that the other UV lines have higher ionization potential, their emission is expected to be less extended than Lyα.…”

Section: Spectral Extractionsmentioning

confidence: 99%

The MUSE Hubble Ultra Deep Field Survey

Feltre

Maseda

Bacon

et al. 2020

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We investigated the ultraviolet (UV) spectral properties of faint Lyman-α emitters (LAEs) in the redshift range 2.9 ≤ z ≤ 4.6, and we provide material to prepare future observations of the faint Universe. We used data from the MUSE Hubble Ultra Deep Survey to construct mean rest-frame spectra of continuum-faint (median M UV of −18 and down to M UV of −16), low stellar mass (median value of 10 8.4 M and down to 10 7 M) LAEs at redshift z 3. We computed various averaged spectra of LAEs, subsampled on the basis of their observational (e.g., Lyα strength, UV magnitude and spectral slope) and physical (e.g., stellar mass and starformation rate) properties. We searched for UV spectral features other than Lyα, such as higher ionization nebular emission lines and absorption features. We successfully observed the O iii]λ1666 and [C iii]λ1907+C iii]λ1909 collisionally excited emission lines and the He iiλ1640 recombination feature, as well as the resonant C ivλλ1548,1551 doublet either in emission or P-Cygni. We compared the observed spectral properties of the different mean spectra and find the emission lines to vary with the observational and physical properties of the LAEs. In particular, the mean spectra of LAEs with larger Lyα equivalent widths, fainter UV magnitudes, bluer UV spectral slopes, and lower stellar masses show the strongest nebular emission. The line ratios of these lines are similar to those measured in the spectra of local metal-poor galaxies, while their equivalent widths are weaker compared to the handful of extreme values detected in individual spectra of z > 2 galaxies. This suggests that weak UV features are likely ubiquitous in high z, lowmass, and faint LAEs. We publicly released the stacked spectra, as they can serve as empirical templates for the design of future observations, such as those with the James Webb Space Telescope and the Extremely Large Telescope.

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The dominant origin of diffuse Lyα halos around Lyα emitters explored by spectral energy distribution fitting and clustering analysis

Cited by 21 publications

References 181 publications

The MUSE Hubble Ultra Deep Field Survey

The MUSE Hubble Ultra Deep Field Survey

The MUSEHubbleUltra Deep Field Survey

The MUSE Hubble Ultra Deep Field Survey

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