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  • 1
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    The MUSE Hubble Ultra Deep Field Survey : XIV. Evolution of the Ly α emitter fraction from z = 3 to z = 6
    EDP Sciences ; 2020
    In:  Astronomy & Astrophysics Vol. 638 ( 2020-06), p. A12-
    Details
    In: Astronomy & Astrophysics, EDP Sciences, Vol. 638 ( 2020-06), p. A12-
    Abstract: Context. The Ly α 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 under debate. Aims. Thanks to deep data obtained with the integral field spectrograph Multi Unit Spectroscopic Explorer (MUSE), 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 a significantly fainter range than in former studies ( M 1500  ≤ −18.75) and it allows us to probe the bulk of the population of high-redshift star-forming galaxies. Methods. We constructed a UV-complete photometric-redshift sample following UV luminosity functions and measured the Ly α emission with MUSE using the latest (second) data release from the MUSE Hubble Ultra Deep Field Survey. Results. We derived the redshift evolution of X LAE for M 1500  ∈ [ − 21.75; −17.75] for the first time with a equivalent width range EW (Ly α ) ≥ 65 Å and found 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 (Ly α ) ≥ 25 Å, our X LAE values are consistent with those in the literature within 1 σ 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 (Ly α ) ≥ 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 Ly α 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.
    Type of Medium: Online Resource
    ISSN: 0004-6361 , 1432-0746
    URL: Article
    DOI: 10.1051/0004-6361/201937340
    RVK:
    UA 1000
    RVK:
    US 1090
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2020
    detail.hit.zdb_id: 1458466-9
    SSG: 16,12
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  • 2
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    The MUSE Hubble Ultra Deep Field Survey : XV. The mean rest-UV spectra of Ly α emitters at z 〉 3
    EDP Sciences ; 2020
    In:  Astronomy & Astrophysics Vol. 641 ( 2020-09), p. A118-
    Details
    In: Astronomy & Astrophysics, EDP Sciences, Vol. 641 ( 2020-09), p. A118-
    Abstract: 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., Ly α strength, UV magnitude and spectral slope) and physical (e.g., stellar mass and star-formation rate) properties. We searched for UV spectral features other than Ly α , such as higher ionization nebular emission lines and absorption features. We successfully observed the O  III ] λ 1666 and [C  III ] λ 1907+C  III ] λ 1909 collisionally excited emission lines and the He  II λ 1640 recombination feature, as well as the resonant C  IV λ λ 1548,1551 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 Ly α 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 , low-mass, 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.
    Type of Medium: Online Resource
    ISSN: 0004-6361 , 1432-0746
    URL: Article
    DOI: 10.1051/0004-6361/202038133
    RVK:
    UA 1000
    RVK:
    US 1090
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2020
    detail.hit.zdb_id: 1458466-9
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  • 3
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    Exploring He II  λ 1640 emission line properties at z ∼2−4
    EDP Sciences ; 2019
    In:  Astronomy & Astrophysics Vol. 624 ( 2019-04), p. A89-
    Details
    In: Astronomy & Astrophysics, EDP Sciences, Vol. 624 ( 2019-04), p. A89-
    Abstract: Deep optical spectroscopic surveys of galaxies provide a unique opportunity to investigate rest-frame ultra-violet (UV) emission line properties of galaxies at z  ∼ 2 − 4.5. Here we combine VLT/MUSE Guaranteed Time Observations of the Hubble Deep Field South, Ultra Deep Field, COSMOS, and several quasar fields with other publicly available data from VLT/VIMOS and VLT/FORS2 to construct a catalogue of He  II   λ 1640 emitters at z  ≳ 2. The deepest areas of our MUSE pointings reach a 3 σ line flux limit of 3.1 × 10 −19 erg s −1 cm −2 . After discarding broad-line active galactic nuclei, we find 13 He  II   λ 1640 detections from MUSE with a median M UV  = −20.1 and 21 tentative He  II   λ 1640 detections from other public surveys. Excluding Ly α , all except two galaxies in our sample show at least one other rest-UV emission line, with C  III ] λ 1907, λ 1909 being the most prominent. We use multi-wavelength data available in the Hubble legacy fields to derive basic galaxy properties of our sample through spectral energy distribution fitting techniques. Taking advantage of the high-quality spectra obtained by MUSE (∼10 − 30 h of exposure time per pointing), we use photo-ionisation models to study the rest-UV emission line diagnostics of the He  II   λ 1640 emitters. Line ratios of our sample can be reproduced by moderately sub-solar photo-ionisation models, however, we find that including effects of binary stars lead to degeneracies in most free parameters. Even after considering extra ionising photons produced by extreme sub-solar metallicity binary stellar models, photo-ionisation models are unable to reproduce rest-frame He  II   λ 1640 equivalent widths (∼0.2 − 10 Å), thus additional mechanisms are necessary in models to match the observed He  II   λ 1640 properties.
    Type of Medium: Online Resource
    ISSN: 0004-6361 , 1432-0746
    URL: Article
    DOI: 10.1051/0004-6361/201834565
    RVK:
    UA 1000
    RVK:
    US 1090
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2019
    detail.hit.zdb_id: 1458466-9
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  • 4
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    The MUSE eXtremely deep field: first panoramic view of an Mg II emitting intragroup medium
    EDP Sciences ; 2022
    In:  Astronomy & Astrophysics Vol. 663 ( 2022-07), p. A11-
    Details
    In: Astronomy & Astrophysics, EDP Sciences, Vol. 663 ( 2022-07), p. A11-
    Abstract: Using the exquisite data from the MUSE eXtremely Deep Field (MXDF), we report the discovery of an Mg  II emission nebula with an area above a 2 σ significance level of 1000 proper kpc 2 . This provides the first panoramic view of the spatial distribution of magnesium in the intragroup medium of a low-mass group of five star-forming galaxies at z  = 1.31. The galaxy group members are separated by less than 50 physical kpc in projection and ≈120 km s −1 in velocity space. The most massive galaxy has a stellar mass of 10 9.35   M ⊙ and shows an Mg  II P-Cygni line profile, indicating the presence of an outflow, which is consistent with the spatially resolved spectral analysis showing ≈+120 km s −1 shift of the Mg  II emission lines with respect to the systemic redshift. The other galaxies are less massive and only show Mg  II in emission. The detected Mg  II nebula has a maximal projected extent of ≈70 kpc, including a low-surface-brightness (≈2 × 10 −19 erg s −1 cm −2 arcsec −2 ) gaseous bridge between two subgroups of galaxies. The presence of absorption features in the spectrum of a background galaxy located at an impact parameter of 19 kpc from the closest galaxy of the group indicates the presence of gas enriched in magnesium even beyond the detected nebula seen in emission, which suggests that we are observing the tip of a larger intragroup medium. The observed Mg  II velocity gradient suggests an overall rotation of the structure along the major axis of the most massive galaxy. Our MUSE data also reveal extended Fe  II * emission in the vicinity of the most massive galaxy, aligned with its minor axis and pointing towards a neighboring galaxy. Extended [O  II ] emission is found around the galaxy group members and at the location of the Mg  II bridge. Our results suggest that both tidal stripping effects from galaxy interactions and outflows are enriching the intragroup medium of this system.
    Type of Medium: Online Resource
    ISSN: 0004-6361 , 1432-0746
    URL: Article
    DOI: 10.1051/0004-6361/202142179
    RVK:
    UA 1000
    RVK:
    US 1090
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2022
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  • 5
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    Elevated ionizing photon production efficiency in faint high-equivalent-width Lyman-α emitters
    Oxford University Press (OUP) ; 2020
    In:  Monthly Notices of the Royal Astronomical Society Vol. 493, No. 4 ( 2020-04-21), p. 5120-5130
    Details
    In: Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP), Vol. 493, No. 4 ( 2020-04-21), p. 5120-5130
    Abstract: While low-luminosity galaxies dominate number counts at all redshifts, their contribution to cosmic reionization is poorly understood due to a lack of knowledge of their physical properties. We isolate a sample of 35 z ≈ 4–5 continuum-faint Lyman-α emitters from deep VLT/MUSE spectroscopy and directly measure their H α emission using stacked Spitzer/IRAC Ch. 1 photometry. Based on Hubble Space Telescope imaging, we determine that the average UV continuum magnitude is fainter than −16 (≈ 0.01 L⋆), implying a median Lyman-α equivalent width of 259 Å. By combining the H α measurement with the UV magnitude, we determine the ionizing photon production efficiency, ξion, a first for such faint galaxies. The measurement of log10 (ξion [Hz erg−1]) = 26.28 ($^{+0.28}_{-0.40}$) is in excess of literature measurements of both continuum- and emission line-selected samples, implying a more efficient production of ionizing photons in these lower luminosity, Lyman-α-selected systems. We conclude that this elevated efficiency can be explained by stellar populations with metallicities between 4 × 10−4 and 0.008, with light-weighted ages less than 3 Myr.
    Type of Medium: Online Resource
    ISSN: 0035-8711 , 1365-2966
    URL: Article
    DOI: 10.1093/mnras/staa622
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2020
    detail.hit.zdb_id: 2016084-7
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  • 6
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    The nature of CR7 revealed with MUSE: a young starburst powering extended Ly α emission at z = 6.6
    Oxford University Press (OUP) ; 2020
    In:  Monthly Notices of the Royal Astronomical Society Vol. 498, No. 2 ( 2020-09-26), p. 3043-3059
    Details
    In: Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP), Vol. 498, No. 2 ( 2020-09-26), p. 3043-3059
    Abstract: CR7 is among the most luminous Ly α emitters (LAEs) known at z = 6.6 and consists of at least three UV components that are surrounded by Ly α emission. Previous studies have suggested that it may host an extreme ionizing source. Here, we present deep integral field spectroscopy of CR7 with VLT/Multi Unit Spectroscopic Explorer (MUSE). We measure extended emission with a similar halo scale length as typical LAEs at z ≈ 5. CR7’s Ly α halo is clearly elongated along the direction connecting the multiple components, likely tracing the underlying gas distribution. The Ly α emission originates almost exclusively from the brightest UV component, but we also identify a faint kinematically distinct Ly α emitting region nearby a fainter component. Combined with new near-infrared data, the MUSE data show that the rest-frame Ly α equivalent width (EW) is ≈100 Å. This is a factor 4 higher than the EW measured in low-redshift analogues with carefully matched Ly α profiles (and thus arguably H i column density), but this EW can plausibly be explained by star formation. Alternative scenarios requiring active galactic nucleus (AGN) powering are also disfavoured by the narrower and steeper Ly α spectrum and much smaller IR to UV ratio compared to obscured AGN in other Ly α blobs. CR7’s Ly α emission, while extremely luminous, resembles the emission in more common LAEs at lower redshifts very well and is likely powered by a young metal-poor starburst.
    Type of Medium: Online Resource
    ISSN: 0035-8711 , 1365-2966
    URL: Article
    DOI: 10.1093/mnras/staa2550
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2020
    detail.hit.zdb_id: 2016084-7
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  • 7
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    Constraining the cosmic UV background at z 〉 3 with MUSE Lyman-α emission observations
    Oxford University Press (OUP) ; 2021
    In:  Monthly Notices of the Royal Astronomical Society Vol. 504, No. 1 ( 2021-04-15), p. 16-32
    Details
    In: Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP), Vol. 504, No. 1 ( 2021-04-15), p. 16-32
    Abstract: The intensity of the Cosmic UV background (UVB), coming from all sources of ionizing photons such as star-forming galaxies and quasars, determines the thermal evolution and ionization state of the intergalactic medium (IGM) and is, therefore, a critical ingredient for models of cosmic structure formation. Most of the previous estimates are based on the comparison between observed and simulated Lyman-α forest. We present the results of an independent method to constrain the product of the UVB photoionization rate and the covering fraction of Lyman limit systems (LLSs) by searching for the fluorescent Lyman-α emission produced by self-shielded clouds. Because the expected surface brightness is well below current sensitivity limits for direct imaging, we developed a new method based on 3D stacking of the IGM around Lyman-α emitting galaxies (LAEs) between 2.9 & lt; z & lt; 6.6 using deep MUSE observations. Combining our results with covering fractions of LLSs obtained from mock cubes extracted from the EAGLE simulation, we obtain new and independent constraints on the UVB at z & gt; 3 that are consistent with previous measurements, with a preference for relatively low UVB intensities at z = 3, and which suggest a non-monotonic decrease of ΓH i with increasing redshift between 3 & lt; z & lt; 5. This could suggest a possible tension between some UVB models and current observations which however require deeper and wider observations in Lyman-α emission and absorption to be confirmed. Assuming instead a value of UVB from current models, our results constrain the covering fraction of LLSs at 3 & lt; z & lt; 4.5 to be less than 25 per cent within 150 kpc from LAEs.
    Type of Medium: Online Resource
    ISSN: 0035-8711 , 1365-2966
    URL: Article
    DOI: 10.1093/mnras/stab796
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2021
    detail.hit.zdb_id: 2016084-7
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  • 8
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    Exploring He II  λ 1640 emission line properties at z   ∼  2−4 ( Corrigendum )
    EDP Sciences ; 2021
    In:  Astronomy & Astrophysics Vol. 648 ( 2021-04), p. C2-
    Details
    In: Astronomy & Astrophysics, EDP Sciences, Vol. 648 ( 2021-04), p. C2-
    Type of Medium: Online Resource
    ISSN: 0004-6361 , 1432-0746
    URL: Article
    DOI: 10.1051/0004-6361/201834565e
    RVK:
    UA 1000
    RVK:
    US 1090
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2021
    detail.hit.zdb_id: 1458466-9
    SSG: 16,12
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  • 9
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    The MUSE Hubble Ultra Deep Field Survey : XIII. Spatially resolved spectral properties of Lyman α haloes around star-forming galaxies at z 〉 3
    EDP Sciences ; 2020
    In:  Astronomy & Astrophysics Vol. 635 ( 2020-03), p. A82-
    Details
    In: Astronomy & Astrophysics, EDP Sciences, Vol. 635 ( 2020-03), p. A82-
    Abstract: We present spatially resolved maps of six individually-detected Lyman α haloes (LAHs) as well as a first statistical analysis of the Lyman α (Ly α ) spectral signature in the circum-galactic medium of high-redshift star-forming galaxies (−17.5  〉   M UV   〉  −21.5) using the Multi-Unit Spectroscopic Explorer. Our resolved spectroscopic analysis of the LAHs reveals significant intrahalo variations of the Ly α line profile. Using a three-dimensional two-component model for the Ly α emission, we measured the full width at half maximum (FWHM), the peak velocity shift, and the asymmetry of the Ly α line in the core and in the halo of 19 galaxies. We find that the Ly α 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 Ly α 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 ( M UV   〈  −20) show broader, more redshifted, and less asymmetric Ly α 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 Ly α lines. The generally broad and red line shapes found in the halo component suggest that the Ly α 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 Ly α 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.
    Type of Medium: Online Resource
    ISSN: 0004-6361 , 1432-0746
    URL: Article
    DOI: 10.1051/0004-6361/201937339
    RVK:
    UA 1000
    RVK:
    US 1090
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2020
    detail.hit.zdb_id: 1458466-9
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  • 10
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    The MUSE eXtremely Deep Field: Individual detections of Ly α haloes around rest-frame UV-selected galaxies at z ≃ 2.9–4.4
    EDP Sciences ; 2022
    In:  Astronomy & Astrophysics Vol. 660 ( 2022-04), p. A44-
    Details
    In: Astronomy & Astrophysics, EDP Sciences, Vol. 660 ( 2022-04), p. A44-
    Abstract: Hydrogen Ly α haloes (LAHs) are commonly used as a tracer of the circumgalactic medium (CGM) at high redshifts. In this work, we aim to explore the existence of Ly α haloes around individual UV-selected galaxies, rather than around Ly α emitters (LAEs), at high redshifts. Our sample was continuum-selected with F 775 W  ≤ 27.5, and spectroscopic redshifts were assigned or constrained for all the sources thanks to the deepest (100- to 140-h) existing Very Large Telescope (VLT)/Multi-Unit Spectroscopic Explorer (MUSE) data with adaptive optics. The final sample includes 21 galaxies that are purely F 775 W -magnitude selected within the redshift range z  ≈ 2.9 − 4.4 and within a UV magnitude range −20 ≤  M 1500  ≤ −18, thus avoiding any bias toward LAEs. We tested whether galaxy’s Ly α emission is significantly more extended than the MUSE PSF-convolved continuum component. We find 17 LAHs and four non-LAHs. We report the first individual detections of extended Ly α emission around non-LAEs. The Ly α halo fraction is thus as high as 81.0 −11.2 +10.3 %, which is close to that for LAEs at z  = 3 − 6 in the literature. This implies that UV-selected galaxies generally have a large amount of hydrogen in their CGM. We derived the mean surface brightness (SB) profile for our LAHs with cosmic dimming corrections and find that Ly α emission extends to 5.4 arcsec (≃40 physical kpc at the midpoint redshift z  = 3.6) above the typical 1 σ SB limit. The incidence rate of surrounding gas detected in Ly α per one-dimensional line of sight per unit redshift, d n /d z , is estimated to be 0.76 −0.09 +0.09 for galaxies with M 1500  ≤ −18 mag at z  ≃ 3.7. Assuming that Ly α emission and absorption arise in the same gas, this suggests, based on abundance matching, that LAHs trace the same gas as damped Ly α systems (DLAs) and sub-DLAs.
    Type of Medium: Online Resource
    ISSN: 0004-6361 , 1432-0746
    URL: Article
    DOI: 10.1051/0004-6361/202142302
    RVK:
    UA 1000
    RVK:
    US 1090
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2022
    detail.hit.zdb_id: 1458466-9
    SSG: 16,12
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