@article{11488,
  abstract     = {Hydrogen Lyα 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 Lyα haloes around individual UV-selected galaxies, rather than around Lyα emitters (LAEs), at high redshifts. Our sample was continuum-selected with F775W ≤ 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 F775W-magnitude selected within the redshift range z ≈ 2.9 − 4.4 and within a UV magnitude range −20 ≤ M1500 ≤ −18, thus avoiding any bias toward LAEs. We tested whether galaxy’s Lyα 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 Lyα emission around non-LAEs. The Lyα 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 Lyα emission extends to 5.4 arcsec (≃40 physical kpc at the midpoint redshift z = 3.6) above the typical 1σ SB limit. The incidence rate of surrounding gas detected in Lyα per one-dimensional line of sight per unit redshift, dn/dz, is estimated to be 0.76−0.09+0.09 for galaxies with M1500 ≤ −18 mag at z ≃ 3.7. Assuming that Lyα emission and absorption arise in the same gas, this suggests, based on abundance matching, that LAHs trace the same gas as damped Lyα systems (DLAs) and sub-DLAs.},
  author       = {Kusakabe, Haruka and Verhamme, Anne and Blaizot, Jérémy and Garel, Thibault and Wisotzki, Lutz and Leclercq, Floriane and Bacon, Roland and Schaye, Joop and Gallego, Sofia G. and Kerutt, Josephine and Matthee, Jorryt J and Maseda, Michael and Nanayakkara, Themiya and Pelló, Roser and Richard, Johan and Tresse, Laurence and Urrutia, Tanya and Vitte, Eloïse},
  issn         = {1432-0746},
  journal      = {Astronomy & Astrophysics},
  keywords     = {Space and Planetary Science, Astronomy and Astrophysics, galaxies: high-redshift / galaxies: formation / galaxies: evolution / cosmology: observations},
  publisher    = {EDP Sciences},
  title        = {{The MUSE eXtremely Deep Field: Individual detections of Ly<i>α</i> haloes around rest-frame UV-selected galaxies at <i>z</i> ≃ 2.9–4.4}},
  doi          = {10.1051/0004-6361/202142302},
  volume       = {660},
  year         = {2022},
}

@article{11497,
  abstract     = {Context. The hydrogen Lyman α line is often the only measurable feature in optical spectra of high-redshift galaxies. Its shape and strength are influenced by radiative transfer processes and the properties of the underlying stellar population. High equivalent widths of several hundred Å are especially hard to explain by models and could point towards unusual stellar populations, for example with low metallicities, young stellar ages, and a top-heavy initial mass function. Other aspects influencing equivalent widths are the morphology of the galaxy and its gas properties.
Aims. The aim of this study is to better understand the connection between the Lyman α rest-frame equivalent width (EW0) and spectral properties as well as ultraviolet (UV) continuum morphology by obtaining reliable EW0 histograms for a statistical sample of galaxies and by assessing the fraction of objects with large equivalent widths.
Methods. We used integral field spectroscopy from the Multi Unit Spectroscopic Explorer (MUSE) combined with broad-band data from the Hubble Space Telescope (HST) to measure EW0. We analysed the emission lines of 1920 Lyman α emitters (LAEs) detected in the full MUSE-Wide (one hour exposure time) and MUSE-Deep (ten hour exposure time) surveys and found UV continuum counterparts in archival HST data. We fitted the UV continuum photometric images using the Galfit software to gain morphological information on the rest-UV emission and fitted the spectra obtained from MUSE to determine the double peak fraction, asymmetry, full-width at half maximum, and flux of the Lyman α line.
Results. The two surveys show different histograms of Lyman α EW0. In MUSE-Wide, 20% of objects have EW0 > 240 Å, while this fraction is only 11% in MUSE-Deep and ≈16% for the full sample. This includes objects without HST continuum counterparts (one-third of our sample), for which we give lower limits for EW0. The object with the highest securely measured EW0 has EW0 = 589 ± 193 Å (the highest lower limit being EW0 = 4464 Å). We investigate the connection between EW0 and Lyman α spectral or UV continuum morphological properties.
Conclusions. The survey depth has to be taken into account when studying EW0 distributions. We find that in general, high EW0 objects can have a wide range of spectral and UV morphological properties, which might reflect that the underlying causes for high EW0 values are equally varied.},
  author       = {Kerutt, J. and Wisotzki, L. and Verhamme, A. and Schmidt, K. B. and Leclercq, F. and Herenz, E. C. and Urrutia, T. and Garel, T. and Hashimoto, T. and Maseda, M. and Matthee, Jorryt J and Kusakabe, H. and Schaye, J. and Richard, J. and Guiderdoni, B. and Mauerhofer, V. and Nanayakkara, T. and Vitte, E.},
  issn         = {1432-0746},
  journal      = {Astronomy & Astrophysics},
  keywords     = {Space and Planetary Science, Astronomy and Astrophysics, galaxies: high-redshift / galaxies: formation / galaxies: evolution / cosmology: observations},
  publisher    = {EDP Sciences},
  title        = {{Equivalent widths of Lyman α emitters in MUSE-Wide and MUSE-Deep}},
  doi          = {10.1051/0004-6361/202141900},
  volume       = {659},
  year         = {2022},
}

@article{11585,
  abstract     = {Observations show that star-forming galaxies reside on a tight three-dimensional plane between mass, gas-phase metallicity and star formation rate (SFR), which can be explained by the interplay between metal-poor gas inflows, SFR and outflows. However, different metals are released on different time-scales, which may affect the slope of this relation. Here, we use central, star-forming galaxies with Mstar = 109.0−10.5 M from the EAGLE hydrodynamical simulation to examine three-dimensional relations between mass, SFR and chemical enrichment using absolute and relative C, N, O and Fe abundances. We show that the scatter is smaller when gas-phase α-enhancement is used rather than metallicity. A similar plane also exists for stellar α-enhancement, implying that present-day specific SFRs are correlated with long time-scale star formation histories. Between z = 0 and 1, the α-enhancement plane is even more insensitive to redshift than the plane using metallicity. However, it evolves at z > 1 due to lagging iron yields. At fixed mass, galaxies with higher SFRs have star formation histories shifted toward late times, are more α-enhanced and this α-enhancement increases with redshift as observed. These findings suggest that relations between physical properties inferred from observations may be affected by systematic variations in α-enhancements.},
  author       = {Matthee, Jorryt J},
  issn         = {2397-3366},
  journal      = {Nature Astronomy},
  keywords     = {Astronomy and Astrophysics, galaxies, formation - galaxies, evolution - galaxies, star formation - galaxies, abundances},
  pages        = {984--985},
  publisher    = {Springer Nature},
  title        = {{Differences in galaxy colours are not just about the mass}},
  doi          = {10.1038/s41550-021-01415-y},
  volume       = {5},
  year         = {2021},
}

@article{11504,
  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 (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.},
  author       = {Leclercq, Floriane and Bacon, Roland and Verhamme, Anne and Garel, Thibault and Blaizot, Jérémy and Brinchmann, Jarle and Cantalupo, Sebastiano and Claeyssens, Adélaïde and Conseil, Simon and Contini, Thierry and Hashimoto, Takuya and Herenz, Edmund Christian and Kusakabe, Haruka and Marino, Raffaella Anna and Maseda, Michael and Matthee, Jorryt J and Mitchell, Peter and Pezzulli, Gabriele and Richard, Johan and Schmidt, Kasper Borello and Wisotzki, Lutz},
  issn         = {1432-0746},
  journal      = {Astronomy & Astrophysics},
  keywords     = {Space and Planetary Science, Astronomy and Astrophysics galaxies: high-redshift / galaxies: formation / galaxies: evolution / cosmology: observations},
  publisher    = {EDP Sciences},
  title        = {{The MUSE Hubble Ultra Deep field survey: XIII. Spatially resolved spectral properties of Lyman α haloes around star-forming galaxies at z > 3}},
  doi          = {10.1051/0004-6361/201937339},
  volume       = {635},
  year         = {2020},
}

@article{11499,
  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 λ1640 emitters at z ≳ 2. The deepest areas of our MUSE pointings reach a 3σ 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 λ1640 detections from MUSE with a median MUV = −20.1 and 21 tentative He II λ1640 detections from other public surveys. Excluding Lyα, all except two galaxies in our sample show at least one other rest-UV emission line, with C III] λ1907, λ1909 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 λ1640 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 λ1640 equivalent widths (∼0.2 − 10 Å), thus additional mechanisms are necessary in models to match the observed He II λ1640 properties.},
  author       = {Nanayakkara, Themiya and Brinchmann, Jarle and Boogaard, Leindert and Bouwens, Rychard and Cantalupo, Sebastiano and Feltre, Anna and Kollatschny, Wolfram and Marino, Raffaella Anna and Maseda, Michael and Matthee, Jorryt J and Paalvast, Mieke and Richard, Johan and Verhamme, Anne},
  issn         = {1432-0746},
  journal      = {Astronomy & Astrophysics},
  keywords     = {Space and Planetary Science, Astronomy and Astrophysics, galaxies: ISM / galaxies: star formation / galaxies: evolution / galaxies: high-redshift},
  publisher    = {EDP Sciences},
  title        = {{Exploring He II λ1640 emission line properties at z ∼2−4}},
  doi          = {10.1051/0004-6361/201834565},
  volume       = {648},
  year         = {2019},
}

@article{11507,
  abstract     = {Lyman-α (Lyα) is intrinsically the brightest line emitted from active galaxies. While it originates from many physical processes, for star-forming galaxies the intrinsic Lyα luminosity is a direct tracer of the Lyman-continuum (LyC) radiation produced by the most massive O- and early-type B-stars (M⋆ ≳ 10 M⊙) with lifetimes of a few Myrs. As such, Lyα luminosity should be an excellent instantaneous star formation rate (SFR) indicator. However, its resonant nature and susceptibility to dust as a rest-frame UV photon makes Lyα very hard to interpret due to the uncertain Lyα escape fraction, fesc, Lyα. Here we explore results from the CAlibrating LYMan-α with Hα (CALYMHA) survey at z = 2.2, follow-up of Lyα emitters (LAEs) at z = 2.2 − 2.6 and a z ∼ 0−0.3 compilation of LAEs to directly measure fesc, Lyα with Hα. We derive a simple empirical relation that robustly retrieves fesc, Lyα as a function of Lyα rest-frame EW (EW0): fesc,Lyα = 0.0048 EW0[Å] ± 0.05 and we show that it constrains a well-defined anti-correlation between ionisation efficiency (ξion) and dust extinction in LAEs. Observed Lyα luminosities and EW0 are easy measurable quantities at high redshift, thus making our relation a practical tool to estimate intrinsic Lyα and LyC luminosities under well controlled and simple assumptions. Our results allow observed Lyα luminosities to be used to compute SFRs for LAEs at z ∼ 0−2.6 within ±0.2 dex of the Hα dust corrected SFRs. We apply our empirical SFR(Lyα,EW0) calibration to several sources at z ≥ 2.6 to find that star-forming LAEs have SFRs typically ranging from 0.1 to 20 M⊙ yr−1 and that our calibration might be even applicable for the most luminous LAEs within the epoch of re-ionisation. Our results imply high ionisation efficiencies (log10[ξion/Hz erg−1] = 25.4−25.6) and low dust content in LAEs across cosmic time, and will be easily tested with future observations with JWST which can obtain Hα and Hβ measurements for high-redshift LAEs.},
  author       = {Sobral, David and Matthee, Jorryt J},
  issn         = {1432-0746},
  journal      = {Astronomy & Astrophysics},
  keywords     = {Space and Planetary Science, Astronomy and Astrophysics, galaxies: high-redshift / galaxies: star formation / galaxies: statistics / galaxies: evolution / galaxies: formation / galaxies: ISM},
  publisher    = {EDP Sciences},
  title        = {{Predicting Lyα escape fractions with a simple observable: Lyα in emission as an empirically calibrated star formation rate indicator}},
  doi          = {10.1051/0004-6361/201833075},
  volume       = {623},
  year         = {2019},
}

@article{11518,
  abstract     = {We present spectroscopic follow-up observations of CR7 with ALMA, targeted at constraining the infrared (IR) continuum and [C II]158 mm line-emission at high spatial resolution matched to the HST/WFC3 imaging. CR7 is a luminous Lyα emitting galaxy at z = 6.6 that consists of three separated UV-continuum components. Our observations reveal several well-separated components of [C II] emission. The two most luminous components in [C II] coincide with the brightest UV components (A and B), blueshifted by »150 km s−1 with respect to the
peak of Lyα emission. Other [C II] components are observed close to UV clumps B and C and are blueshifted by »300 and ≈80 km s−1 with respect to the systemic redshift. We do not detect FIR continuum emission due to dust with a 3σ limiting luminosity LIR T L d 35 K 3.1 10 = <´ 10 ( ) . This allows us to mitigate uncertainties in the dust-corrected SFR and derive SFRs for the three UV clumps A, B, and C of 28, 5, and 7 M yr−1. All clumps have [C II] luminosities consistent within the scatter observed in the local relation between SFR and L[ ] C II , implying that strong Lyα emission does not necessarily anti-correlate with [C II] luminosity. Combining
our measurements with the literature, we show that galaxies with blue UV slopes have weaker [C II] emission at fixed SFR, potentially due to their lower metallicities and/or higher photoionization. Comparison with hydrodynamical simulations suggests that CR7ʼs clumps have metallicities of 0.1 Z Z 0.2 < < . The observed ISM structure of CR7 indicates that we are likely witnessing the build up of a central galaxy in the early universe through complex accretion of satellites.},
  author       = {Matthee, Jorryt J and Sobral, D. and Boone, F. and Röttgering, H. and Schaerer, D. and Girard, M. and Pallottini, A. and Vallini, L. and Ferrara, A. and Darvish, B. and Mobasher, B.},
  issn         = {1538-4357},
  journal      = {The Astrophysical Journal},
  keywords     = {Space and Planetary Science, Astronomy and Astrophysics, dark ages, reionization, first stars – galaxies: formation – galaxies: high-redshift – galaxies: ISM – galaxies: kinematics and dynamics},
  number       = {2},
  publisher    = {IOP Publishing},
  title        = {{ALMA reveals metals yet no dust within multiple components in CR7}},
  doi          = {10.3847/1538-4357/aa9931},
  volume       = {851},
  year         = {2017},
}