@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{11605, abstract = {Context. The discovery of moderate differential rotation between the core and the envelope of evolved solar-like stars could be the signature of a strong magnetic field trapped inside the radiative interior. The population of intermediate-mass red giants presenting surprisingly low-amplitude mixed modes (i.e. oscillation modes that behave as acoustic modes in their external envelope and as gravity modes in their core) could also arise from the effect of an internal magnetic field. Indeed, stars more massive than about 1.1 solar masses are known to develop a convective core during their main sequence. The field generated by the dynamo triggered by this convection could be the progenitor of a strong fossil magnetic field trapped inside the core of the star for the remainder of its evolution. Aims. Observations of mixed modes can constitute an excellent probe of the deepest layers of evolved solar-like stars, and magnetic fields in those regions can impact their propagation. The magnetic perturbation on mixed modes may therefore be visible in asteroseismic data. To unravel which constraints can be obtained from observations, we theoretically investigate the effects of a plausible mixed axisymmetric magnetic field with various amplitudes on the mixed-mode frequencies of evolved solar-like stars. Methods. First-order frequency perturbations due to an axisymmetric magnetic field were computed for dipolar and quadrupolar mixed modes. These computations were carried out for a range of stellar ages, masses, and metallicities. Conclusions. We show that typical fossil-field strengths of 0.1 − 1 MG, consistent with the presence of a dynamo in the convective core during the main sequence, provoke significant asymmetries on mixed-mode frequency multiplets during the red giant branch. We provide constraints and methods for the detectability of such magnetic signatures. We show that these signatures may be detectable in asteroseismic data for field amplitudes small enough for the amplitude of the modes not to be affected by the conversion of gravity into Alfvén waves inside the magnetised interior. Finally, we infer an upper limit for the strength of the field and the associated lower limit for the timescale of its action in order to redistribute angular momentum in stellar interiors.}, author = {Bugnet, Lisa Annabelle and Prat, V. and Mathis, S. and Astoul, A. and Augustson, K. and García, R. A. and Mathur, S. and Amard, L. and Neiner, C.}, issn = {1432-0746}, journal = {Astronomy & Astrophysics}, keywords = {Space and Planetary Science, Astronomy and Astrophysics, stars, oscillations / stars, magnetic field / stars, interiors / stars, evolution / stars, rotation}, publisher = {EDP Sciences}, title = {{Magnetic signatures on mixed-mode frequencies: I. An axisymmetric fossil field inside the core of red giants}}, doi = {10.1051/0004-6361/202039159}, volume = {650}, year = {2021}, } @article{11609, abstract = {Context. Stellar interiors are the seat of efficient transport of angular momentum all along their evolution. In this context, understanding the dependence of the turbulent transport triggered by the instabilities of the vertical and horizontal shears of the differential rotation in stellar radiation zones as a function of their rotation, stratification, and thermal diffusivity is mandatory. Indeed, it constitutes one of the cornerstones of the rotational transport and mixing theory, which is implemented in stellar evolution codes to predict the rotational and chemical evolutions of stars. Aims. We investigate horizontal shear instabilities in rotating stellar radiation zones by considering the full Coriolis acceleration with both the dimensionless horizontal Coriolis component f̃ and the vertical component f. Methods. We performed a linear stability analysis using linearized equations derived from the Navier-Stokes and heat transport equations in the rotating nontraditional f-plane. We considered a horizontal shear flow with a hyperbolic tangent profile as the base flow. The linear stability was analyzed numerically in wide ranges of parameters, and we performed an asymptotic analysis for large vertical wavenumbers using the Wentzel-Kramers-Brillouin-Jeffreys (WKBJ) approximation for nondiffusive and highly-diffusive fluids. Results. As in the traditional f-plane approximation, we identify two types of instabilities: the inflectional and inertial instabilities. The inflectional instability is destabilized as f̃ increases and its maximum growth rate increases significantly, while the thermal diffusivity stabilizes the inflectional instability similarly to the traditional case. The inertial instability is also strongly affected; for instance, the inertially unstable regime is also extended in the nondiffusive limit as 0 < f < 1 + f̃ 2/N2, where N is the dimensionless Brunt-Väisälä frequency. More strikingly, in the high thermal diffusivity limit, it is always inertially unstable at any colatitude θ except at the poles (i.e., 0° < θ <  180°). We also derived the critical Reynolds numbers for the inertial instability using the asymptotic dispersion relations obtained from the WKBJ analysis. Using the asymptotic and numerical results, we propose a prescription for the effective turbulent viscosities induced by the inertial and inflectional instabilities that can be possibly used in stellar evolution models. The characteristic time of this turbulence is short enough so that it is efficient to redistribute angular momentum and to mix chemicals in stellar radiation zones.}, author = {Park, J. and Prat, V. and Mathis, S. and Bugnet, Lisa Annabelle}, issn = {1432-0746}, journal = {Astronomy & Astrophysics}, keywords = {Space and Planetary Science, Astronomy and Astrophysics, hydrodynamics / turbulence / stars, rotation / stars, evolution}, publisher = {EDP Sciences}, title = {{Horizontal shear instabilities in rotating stellar radiation zones: II. Effects of the full Coriolis acceleration}}, doi = {10.1051/0004-6361/202038654}, volume = {646}, year = {2021}, } @article{9252, abstract = {This paper analyses the conditions for local adaptation in a metapopulation with infinitely many islands under a model of hard selection, where population size depends on local fitness. Each island belongs to one of two distinct ecological niches or habitats. Fitness is influenced by an additive trait which is under habitat‐dependent directional selection. Our analysis is based on the diffusion approximation and accounts for both genetic drift and demographic stochasticity. By neglecting linkage disequilibria, it yields the joint distribution of allele frequencies and population size on each island. We find that under hard selection, the conditions for local adaptation in a rare habitat are more restrictive for more polygenic traits: even moderate migration load per locus at very many loci is sufficient for population sizes to decline. This further reduces the efficacy of selection at individual loci due to increased drift and because smaller populations are more prone to swamping due to migration, causing a positive feedback between increasing maladaptation and declining population sizes. Our analysis also highlights the importance of demographic stochasticity, which exacerbates the decline in numbers of maladapted populations, leading to population collapse in the rare habitat at significantly lower migration than predicted by deterministic arguments.}, author = {Szep, Eniko and Sachdeva, Himani and Barton, Nicholas H}, issn = {1558-5646}, journal = {Evolution}, keywords = {Genetics, Ecology, Evolution, Behavior and Systematics, General Agricultural and Biological Sciences}, number = {5}, pages = {1030--1045}, publisher = {Wiley}, title = {{Polygenic local adaptation in metapopulations: A stochastic eco‐evolutionary model}}, doi = {10.1111/evo.14210}, volume = {75}, year = {2021}, } @article{9374, abstract = {If there are no constraints on the process of speciation, then the number of species might be expected to match the number of available niches and this number might be indefinitely large. One possible constraint is the opportunity for allopatric divergence. In 1981, Felsenstein used a simple and elegant model to ask if there might also be genetic constraints. He showed that progress towards speciation could be described by the build‐up of linkage disequilibrium among divergently selected loci and between these loci and those contributing to other forms of reproductive isolation. Therefore, speciation is opposed by recombination, because it tends to break down linkage disequilibria. Felsenstein then introduced a crucial distinction between “two‐allele” models, which are subject to this effect, and “one‐allele” models, which are free from the recombination constraint. These fundamentally important insights have been the foundation for both empirical and theoretical studies of speciation ever since.}, author = {Butlin, Roger K. and Servedio, Maria R. and Smadja, Carole M. and Bank, Claudia and Barton, Nicholas H and Flaxman, Samuel M. and Giraud, Tatiana and Hopkins, Robin and Larson, Erica L. and Maan, Martine E. and Meier, Joana and Merrill, Richard and Noor, Mohamed A. F. and Ortiz‐Barrientos, Daniel and Qvarnström, Anna}, issn = {1558-5646}, journal = {Evolution}, keywords = {Genetics, Ecology, Evolution, Behavior and Systematics, General Agricultural and Biological Sciences}, number = {5}, pages = {978--988}, publisher = {Wiley}, title = {{Homage to Felsenstein 1981, or why are there so few/many species?}}, doi = {10.1111/evo.14235}, volume = {75}, year = {2021}, } @article{10568, abstract = {Genetic adaptation and phenotypic plasticity facilitate the migration into new habitats and enable organisms to cope with a rapidly changing environment. In contrast to genetic adaptation that spans multiple generations as an evolutionary process, phenotypic plasticity allows acclimation within the life-time of an organism. Genetic adaptation and phenotypic plasticity are usually studied in isolation, however, only by including their interactive impact, we can understand acclimation and adaptation in nature. We aimed to explore the contribution of adaptation and plasticity in coping with an abiotic (salinity) and a biotic (Vibrio bacteria) stressor using six different populations of the broad-nosed pipefish Syngnathus typhle that originated from either high [14–17 Practical Salinity Unit (PSU)] or low (7–11 PSU) saline environments along the German coastline of the Baltic Sea. We exposed wild caught animals, to either high (15 PSU) or low (7 PSU) salinity, representing native and novel salinity conditions and allowed animals to mate. After male pregnancy, offspring was split and each half was exposed to one of the two salinities and infected with Vibrio alginolyticus bacteria that were evolved at either of the two salinities in a fully reciprocal design. We investigated life-history traits of fathers and expression of 47 target genes in mothers and offspring. Pregnant males originating from high salinity exposed to low salinity were highly susceptible to opportunistic fungi infections resulting in decreased offspring size and number. In contrast, no signs of fungal infection were identified in fathers originating from low saline conditions suggesting that genetic adaptation has the potential to overcome the challenges encountered at low salinity. Offspring from parents with low saline origin survived better at low salinity suggesting genetic adaptation to low salinity. In addition, gene expression analyses of juveniles indicated patterns of local adaptation, trans-generational plasticity and developmental plasticity. In conclusion, our study suggests that pipefish are locally adapted to the low salinity in their environment, however, they are retaining phenotypic plasticity, which allows them to also cope with ancestral salinity levels and prevailing pathogens.}, author = {Goehlich, Henry and Sartoris, Linda and Wagner, Kim-Sara and Wendling, Carolin C. and Roth, Olivia}, issn = {2296-701X}, journal = {Frontiers in Ecology and Evolution}, keywords = {ecology, evolution, behavior and systematics, trans-generational plasticity, genetic adaptation, local adaptation, phenotypic plasticity, Baltic Sea, climate change, salinity, syngnathids}, publisher = {Frontiers Media}, title = {{Pipefish locally adapted to low salinity in the Baltic Sea retain phenotypic plasticity to cope with ancestral salinity levels}}, doi = {10.3389/fevo.2021.626442}, volume = {9}, year = {2021}, } @article{11501, 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 MUV of −18 and down to MUV of −16), low stellar mass (median value of 108.4 M⊙ and down to 107 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 star-formation 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, 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.}, author = {Feltre, Anna and Maseda, Michael V. and Bacon, Roland and Pradeep, Jayadev and Leclercq, Floriane and Kusakabe, Haruka and Wisotzki, Lutz and Hashimoto, Takuya and Schmidt, Kasper B. and Blaizot, Jeremy and Brinchmann, Jarle and Boogaard, Leindert and Cantalupo, Sebastiano and Carton, David and Inami, Hanae and Kollatschny, Wolfram and Marino, Raffaella A. and Matthee, Jorryt J and Nanayakkara, Themiya and Richard, Johan and Schaye, Joop and Tresse, Laurence and Urrutia, Tanya and Verhamme, Anne and Weilbacher, Peter M.}, issn = {1432-0746}, journal = {Astronomy & Astrophysics}, keywords = {Space and Planetary Science, Astronomy and Astrophysics, galaxies: evolution / galaxies: high-redshift / ISM: lines and bands / ultraviolet: ISM / ultraviolet: galaxies}, publisher = {EDP Sciences}, title = {{The MUSE Hubble Ultra Deep Field Survey: XV. The mean rest-UV spectra of Lyα emitters at z > 3}}, doi = {10.1051/0004-6361/202038133}, volume = {641}, year = {2020}, } @article{11503, abstract = {Context. The Lyα emitter (LAE) fraction, XLAE, is a potentially powerful probe of the evolution of the intergalactic neutral hydrogen gas fraction. However, uncertainties in the measurement of XLAE 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 M1500 ≈ −17.75). This is a significantly fainter range than in former studies (M1500 ≤ −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 Lyα emission with MUSE using the latest (second) data release from the MUSE Hubble Ultra Deep Field Survey. Results. We derived the redshift evolution of XLAE for M1500 ∈ [ − 21.75; −17.75] for the first time with a equivalent width range EW(Lyα) ≥ 65 Å and found low values of XLAE ≲ 30% at z ≲ 6. The best-fit linear relation is XLAE = 0.07+0.06−0.03z − 0.22+0.12−0.24. For M1500 ∈ [ − 20.25; −18.75] and EW(Lyα) ≥ 25 Å, our XLAE 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 XLAE on M1500 for EW(Lyα) ≥ 50 Å at z ≈ 3–4, in contrast with previous work. The differences in XLAE 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 XLAE is biased towards higher values when those samples are used. Conclusions. Our results suggest either a lower increase of XLAE towards z ≈ 6 than previously suggested, or even a turnover of XLAE 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.}, author = {Kusakabe, Haruka and Blaizot, Jérémy and Garel, Thibault and Verhamme, Anne and Bacon, Roland and Richard, Johan and Hashimoto, Takuya and Inami, Hanae and Conseil, Simon and Guiderdoni, Bruno and Drake, Alyssa B. and Christian Herenz, Edmund and Schaye, Joop and Oesch, Pascal and Matthee, Jorryt J and Anna Marino, Raffaella and Borello Schmidt, Kasper and Pelló, Roser and Maseda, Michael and Leclercq, Floriane and Kerutt, Josephine and Mahler, Guillaume}, issn = {1432-0746}, journal = {Astronomy & Astrophysics}, keywords = {Space and Planetary Science, Astronomy and Astrophysics, dark ages / reionization / first stars / early Universe / cosmology: observations / galaxies: evolution / galaxies: high-redshift / intergalactic medium}, publisher = {EDP Sciences}, title = {{The MUSE Hubble Ultra Deep Field Survey: XIV. Evolution of the Lyα emitter fraction from z = 3 to z = 6}}, doi = {10.1051/0004-6361/201937340}, volume = {638}, year = {2020}, } @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{11529, 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.}, author = {Matthee, Jorryt J and Pezzulli, Gabriele and Mackenzie, Ruari and Cantalupo, Sebastiano and Kusakabe, Haruka and Leclercq, Floriane and Sobral, David and Richard, Johan and Wisotzki, Lutz and Lilly, Simon and Boogaard, Leindert and Marino, Raffaella and Maseda, Michael and Nanayakkara, Themiya}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, keywords = {Space and Planetary Science, Astronomy and Astrophysics, galaxies: evolution, galaxies: high-redshift, dark ages, reionization, first stars, cosmology: observations}, number = {2}, pages = {3043--3059}, publisher = {Oxford University Press}, title = {{The nature of CR7 revealed with MUSE: A young starburst powering extended Ly α emission at z = 6.6}}, doi = {10.1093/mnras/staa2550}, volume = {498}, year = {2020}, } @article{11531, 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.}, author = {Maseda, Michael V and Bacon, Roland and Lam, Daniel and Matthee, Jorryt J and Brinchmann, Jarle and Schaye, Joop and Labbe, Ivo and Schmidt, Kasper B and Boogaard, Leindert and Bouwens, Rychard and Cantalupo, Sebastiano and Franx, Marijn and Hashimoto, Takuya and Inami, Hanae and Kusakabe, Haruka and Mahler, Guillaume and Nanayakkara, Themiya and Richard, Johan and Wisotzki, Lutz}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, keywords = {Space and Planetary Science, Astronomy and Astrophysics, Galaxies: evolution, Galaxies: high-redshift, Galaxies: ISM}, number = {4}, pages = {5120--5130}, publisher = {Oxford University Press}, title = {{Elevated ionizing photon production efficiency in faint high-equivalent-width Lyman-α emitters}}, doi = {10.1093/mnras/staa622}, volume = {493}, year = {2020}, } @article{11533, abstract = {We explore deep rest-frame UV to FIR data in the COSMOS field to measure the individual spectral energy distributions (SED) of the ∼4000 SC4K (Sobral et al.) Lyman α (Ly α) emitters (LAEs) at z ∼ 2–6. We find typical stellar masses of 109.3 ± 0.6 M⊙ and star formation rates (SFR) of SFRSED=4.4+10.5−2.4 M⊙ yr−1 and SFRLyα=5.9+6.3−2.6 M⊙ yr−1, combined with very blue UV slopes of β=−2.1+0.5−0.4⁠, but with significant variations within the population. MUV and β are correlated in a similar way to UV-selected sources, but LAEs are consistently bluer. This suggests that LAEs are the youngest and/or most dust-poor subset of the UV-selected population. We also study the Ly α rest-frame equivalent width (EW0) and find 45 ‘extreme’ LAEs with EW0 > 240 Å (3σ), implying a low number density of (7 ± 1) × 10−7 Mpc−3. Overall, we measure little to no evolution of the Ly α EW0 and scale length parameter (w0), which are consistently high (EW0=140+280−70 Å, w0=129+11−11 Å) from z ∼ 6 to z ∼ 2 and below. However, w0 is anticorrelated with MUV and stellar mass. Our results imply that sources selected as LAEs have a high Ly α escape fraction (fesc,Ly α) irrespective of cosmic time, but fesc,Ly α is still higher for UV-fainter and lower mass LAEs. The least massive LAEs (<109.5 M⊙) are typically located above the star formation ‘main sequence’ (MS), but the offset from the MS decreases towards z ∼ 6 and towards 1010 M⊙. Our results imply a lack of evolution in the properties of LAEs across time and reveals the increasing overlap in properties of LAEs and UV-continuum selected galaxies as typical star-forming galaxies at high redshift effectively become LAEs.}, author = {Santos, S and Sobral, D and Matthee, Jorryt J and Calhau, J and da Cunha, E and Ribeiro, B and Paulino-Afonso, A and Arrabal Haro, P and Butterworth, J}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, keywords = {Space and Planetary Science, Astronomy and Astrophysics, galaxies: evolution, galaxies: formation, galaxies: high-redshift, galaxies: star formation}, number = {1}, pages = {141--160}, publisher = {Oxford University Press}, title = {{The evolution of rest-frame UV properties, Ly α EWs, and the SFR–stellar mass relation at z ∼ 2–6 for SC4K LAEs}}, doi = {10.1093/mnras/staa093}, volume = {493}, year = {2020}, } @article{11534, abstract = {The observed properties of the Lyman-α (Ly α) emission line are a powerful probe of neutral gas in and around galaxies. We present spatially resolved Ly α spectroscopy with VLT/MUSE targeting VR7, a UV-luminous galaxy at z = 6.532 with moderate Ly α equivalent width (EW0 ≈ 38 Å). These data are combined with deep resolved [CII]158μm spectroscopy obtained with ALMA and UV imaging from HST and we also detect UV continuum with MUSE. Ly α emission is clearly detected with S/N ≈ 40 and FWHM of 374 km s−1. Ly α and [C II] are similarly extended beyond the UV, with effective radius reff = 2.1 ± 0.2 kpc for a single exponential model or reff,Lyα,halo=3.45+1.08−0.87 kpc when measured jointly with the UV continuum. The Ly α profile is broader and redshifted with respect to the [C II] line (by 213 km s−1), but there are spatial variations that are qualitatively similar in both lines and coincide with resolved UV components. This suggests that the emission originates from two components with plausibly different H I column densities. We place VR7 in the context of other galaxies at similar and lower redshift. The Ly α halo scale length is similar at different redshifts and velocity shifts with respect to the systemic are typically smaller. Overall, we find little indications of a more neutral vicinity at higher redshift. This means that the local (∼10 kpc) neutral gas conditions that determine the observed Ly α properties in VR7 resemble the conditions in post-reionization galaxies.}, author = {Matthee, Jorryt J and Sobral, David and Gronke, Max and Pezzulli, Gabriele and Cantalupo, Sebastiano and Röttgering, Huub and Darvish, Behnam and Santos, Sérgio}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, keywords = {Space and Planetary Science, Astronomy and Astrophysics, galaxies: evolution, galaxies: high-redshift, dark ages, reionization, first stars, cosmology: observations}, number = {2}, pages = {1778--1790}, publisher = {Oxford University Press}, title = {{Resolved Lyman-α properties of a luminous Lyman-break galaxy in a large ionized bubble at z = 6.53 }}, doi = {10.1093/mnras/stz3554}, volume = {492}, year = {2020}, } @article{11539, abstract = {Despite recent progress in understanding Ly α emitters (LAEs), relatively little is known regarding their typical black hole activity across cosmic time. Here, we study the X-ray and radio properties of ∼4000 LAEs at 2.2 < z < 6 from the SC4K survey in the COSMOS field. We detect 254 (⁠6.8per cent±0.4per cent⁠) LAEs individually in the X-rays (S/N > 3) with an average luminosity of 1044.31±0.01ergs−1 and average black hole accretion rate (BHAR) of 0.72±0.01 M⊙ yr−1, consistent with moderate to high accreting active galactic neuclei (AGNs). We detect 120 sources in deep radio data (radio AGN fraction of 3.2per cent±0.3per cent⁠). The global AGN fraction (⁠8.6per cent±0.4per cent⁠) rises with Ly α luminosity and declines with increasing redshift. For X-ray-detected LAEs, Ly α luminosities correlate with the BHARs, suggesting that Ly α luminosity becomes a BHAR indicator. Most LAEs (⁠93.1per cent±0.6per cent⁠) at 2 < z < 6 have no detectable X-ray emission (BHARs < 0.017 M⊙ yr−1). The median star formation rate (SFR) of star-forming LAEs from Ly α and radio luminosities is 7.6+6.6−2.8 M⊙ yr−1. The black hole to galaxy growth ratio (BHAR/SFR) for LAEs is <0.0022, consistent with typical star-forming galaxies and the local BHAR/SFR relation. We conclude that LAEs at 2 < z < 6 include two different populations: an AGN population, where Ly α luminosity traces BHAR, and another with low SFRs which remain undetected in even the deepest X-ray stacks but is detected in the radio stacks.}, author = {Calhau, João and Sobral, David and Santos, Sérgio and Matthee, Jorryt J and Paulino-Afonso, Ana and Stroe, Andra and Simmons, Brooke and Barlow-Hall, Cassandra and Adams, Benjamin}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, keywords = {Space and Planetary Science, Astronomy and Astrophysics, galaxies: active, galaxies: evolution, galaxies: high-redshift, quasars: supermassive black holes, galaxies: star formation, cosmology: observations, X-rays: galaxies}, number = {3}, pages = {3341--3362}, publisher = {Oxford University Press}, title = {{The X-ray and radio activity of typical and luminous Ly α emitters from z ∼ 2 to z ∼ 6: Evidence for a diverse, evolving population}}, doi = {10.1093/mnras/staa476}, volume = {493}, year = {2020}, } @inproceedings{11586, abstract = {Distant luminous Lyman-α emitters are excellent targets for detailed observations of galaxies in the epoch of reionisation. Spatially resolved observations of these galaxies allow us to simultaneously probe the emission from young stars, partially ionised gas in the interstellar medium and to constrain the properties of the surrounding hydrogen in the circumgalactic medium. We review recent results from (spectroscopic) follow-up studies of the rest-frame UV, Lyman-α and [CII] emission in luminous galaxies observed ∼500 Myr after the Big Bang with ALMA, HST/WFC3 and VLT/X-SHOOTER. These galaxies likely reside in early ionised bubbles and are complex systems, consisting of multiple well separated and resolved components where traces of metals are already present.}, author = {Matthee, Jorryt J and Sobral, David}, booktitle = {Proceedings of the International Astronomical Union}, issn = {1743-9221}, keywords = {Astronomy and Astrophysics, Space and Planetary Science, galaxies: formation, galaxies: evolution, galaxies: high-redshift}, number = {S352}, pages = {21--25}, publisher = {Cambridge University Press}, title = {{Unveiling the most luminous Lyman-α emitters in the epoch of reionisation}}, doi = {10.1017/s1743921319009451}, volume = {15}, year = {2020}, } @article{8402, abstract = {Background: The mitochondrial pyruvate carrier (MPC) plays a central role in energy metabolism by transporting pyruvate across the inner mitochondrial membrane. Its heterodimeric composition and homology to SWEET and semiSWEET transporters set the MPC apart from the canonical mitochondrial carrier family (named MCF or SLC25). The import of the canonical carriers is mediated by the carrier translocase of the inner membrane (TIM22) pathway and is dependent on their structure, which features an even number of transmembrane segments and both termini in the intermembrane space. The import pathway of MPC proteins has not been elucidated. The odd number of transmembrane segments and positioning of the N-terminus in the matrix argues against an import via the TIM22 carrier pathway but favors an import via the flexible presequence pathway. Results: Here, we systematically analyzed the import pathways of Mpc2 and Mpc3 and report that, contrary to an expected import via the flexible presequence pathway, yeast MPC proteins with an odd number of transmembrane segments and matrix-exposed N-terminus are imported by the carrier pathway, using the receptor Tom70, small TIM chaperones, and the TIM22 complex. The TIM9·10 complex chaperones MPC proteins through the mitochondrial intermembrane space using conserved hydrophobic motifs that are also required for the interaction with canonical carrier proteins. Conclusions: The carrier pathway can import paired and non-paired transmembrane helices and translocate N-termini to either side of the mitochondrial inner membrane, revealing an unexpected versatility of the mitochondrial import pathway for non-cleavable inner membrane proteins.}, author = {Rampelt, Heike and Sucec, Iva and Bersch, Beate and Horten, Patrick and Perschil, Inge and Martinou, Jean-Claude and van der Laan, Martin and Wiedemann, Nils and Schanda, Paul and Pfanner, Nikolaus}, issn = {1741-7007}, journal = {BMC Biology}, keywords = {Biotechnology, Plant Science, General Biochemistry, Genetics and Molecular Biology, Developmental Biology, Cell Biology, Physiology, Ecology, Evolution, Behavior and Systematics, Structural Biology, General Agricultural and Biological Sciences}, publisher = {Springer Nature}, title = {{The mitochondrial carrier pathway transports non-canonical substrates with an odd number of transmembrane segments}}, doi = {10.1186/s12915-019-0733-6}, volume = {18}, year = {2020}, } @phdthesis{8653, abstract = {Mutations are the raw material of evolution and come in many different flavors. Point mutations change a single letter in the DNA sequence, while copy number mutations like duplications or deletions add or remove many letters of the DNA sequence simultaneously. Each type of mutation exhibits specific properties like its rate of formation and reversal. Gene expression is a fundamental phenotype that can be altered by both, point and copy number mutations. The following thesis is concerned with the dynamics of gene expression evolution and how it is affected by the properties exhibited by point and copy number mutations. Specifically, we are considering i) copy number mutations during adaptation to fluctuating environments and ii) the interaction of copy number and point mutations during adaptation to constant environments.  }, author = {Tomanek, Isabella}, issn = {2663-337X}, keywords = {duplication, amplification, promoter, CNV, AMGET, experimental evolution, Escherichia coli}, pages = {117}, publisher = {Institute of Science and Technology Austria}, title = {{The evolution of gene expression by copy number and point mutations}}, doi = {10.15479/AT:ISTA:8653}, year = {2020}, } @article{8767, abstract = {Resources are rarely distributed uniformly within a population. Heterogeneity in the concentration of a drug, the quality of breeding sites, or wealth can all affect evolutionary dynamics. In this study, we represent a collection of properties affecting the fitness at a given location using a color. A green node is rich in resources while a red node is poorer. More colors can represent a broader spectrum of resource qualities. For a population evolving according to the birth-death Moran model, the first question we address is which structures, identified by graph connectivity and graph coloring, are evolutionarily equivalent. We prove that all properly two-colored, undirected, regular graphs are evolutionarily equivalent (where “properly colored” means that no two neighbors have the same color). We then compare the effects of background heterogeneity on properly two-colored graphs to those with alternative schemes in which the colors are permuted. Finally, we discuss dynamic coloring as a model for spatiotemporal resource fluctuations, and we illustrate that random dynamic colorings often diminish the effects of background heterogeneity relative to a proper two-coloring.}, author = {Kaveh, Kamran and McAvoy, Alex and Chatterjee, Krishnendu and Nowak, Martin A.}, issn = {1553-7358}, journal = {PLOS Computational Biology}, keywords = {Ecology, Modelling and Simulation, Computational Theory and Mathematics, Genetics, Ecology, Evolution, Behavior and Systematics, Molecular Biology, Cellular and Molecular Neuroscience}, number = {11}, publisher = {Public Library of Science}, title = {{The Moran process on 2-chromatic graphs}}, doi = {10.1371/journal.pcbi.1008402}, volume = {16}, year = {2020}, } @article{12189, abstract = {Meiotic crossovers (COs) are important for reshuffling genetic information between homologous chromosomes and they are essential for their correct segregation. COs are unevenly distributed along chromosomes and the underlying mechanisms controlling CO localization are not well understood. We previously showed that meiotic COs are mis-localized in the absence of AXR1, an enzyme involved in the neddylation/rubylation protein modification pathway in Arabidopsis thaliana. Here, we report that in axr1-/-, male meiocytes show a strong defect in chromosome pairing whereas the formation of the telomere bouquet is not affected. COs are also redistributed towards subtelomeric chromosomal ends where they frequently form clusters, in contrast to large central regions depleted in recombination. The CO suppressed regions correlate with DNA hypermethylation of transposable elements (TEs) in the CHH context in axr1-/- meiocytes. Through examining somatic methylomes, we found axr1-/- affects DNA methylation in a plant, causing hypermethylation in all sequence contexts (CG, CHG and CHH) in TEs. Impairment of the main pathways involved in DNA methylation is epistatic over axr1-/- for DNA methylation in somatic cells but does not restore regular chromosome segregation during meiosis. Collectively, our findings reveal that the neddylation pathway not only regulates hormonal perception and CO distribution but is also, directly or indirectly, a major limiting pathway of TE DNA methylation in somatic cells.}, author = {Christophorou, Nicolas and She, Wenjing and Long, Jincheng and Hurel, Aurélie and Beaubiat, Sébastien and Idir, Yassir and Tagliaro-Jahns, Marina and Chambon, Aurélie and Solier, Victor and Vezon, Daniel and Grelon, Mathilde and Feng, Xiaoqi and Bouché, Nicolas and Mézard, Christine}, issn = {1553-7404}, journal = {PLOS Genetics}, keywords = {Cancer Research, Genetics (clinical), Genetics, Molecular Biology, Ecology, Evolution, Behavior and Systematics}, number = {6}, publisher = {Public Library of Science (PLoS)}, title = {{AXR1 affects DNA methylation independently of its role in regulating meiotic crossover localization}}, doi = {10.1371/journal.pgen.1008894}, volume = {16}, 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}, }