@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{11513, abstract = {We report the spectroscopic confirmation of a new protocluster in the COSMOS field at z ∼ 2.2, COSMOS Cluster 2.2 (CC2.2), originally identified as an overdensity of narrowband selected Hα emitting candidates. With only two masks of Keck/MOSFIRE near-IR spectroscopy in both H (∼1.47–1.81 μm) and K (∼1.92–2.40 μm) bands (∼1.5 hr each), we confirm 35 unique protocluster members with at least two emission lines detected with S/N > 3. Combined with 12 extra members from the zCOSMOS-deep spectroscopic survey (47 in total), we estimate a mean redshift and a line-of-sight velocity dispersion of zmean = 2.23224 ± 0.00101 and σlos = 645 ± 69 km s−1 for this protocluster, respectively. Assuming virialization and spherical symmetry for the system, we estimate a total mass of Mvir ∼ (1–2) ×1014M⊙ for the structure. We evaluate a number density enhancement of δg ∼ 7 for this system and we argue that the structure is likely not fully virialized at z ∼ 2.2. However, in a spherical collapse model, δg is expected to grow to a linear matter enhancement of ∼1.9 by z = 0, exceeding the collapse threshold of 1.69, and leading to a fully collapsed and virialized Coma-type structure with a total mass of Mdyn(z = 0) ∼ 9.2 × 1014M⊙ by now. This observationally efficient confirmation suggests that large narrowband emission-line galaxy surveys, when combined with ancillary photometric data, can be used to effectively trace the large-scale structure and protoclusters at a time when they are mostly dominated by star-forming galaxies.}, author = {Darvish, Behnam and Scoville, Nick Z. and Martin, Christopher and Sobral, David and Mobasher, Bahram and Rettura, Alessandro and Matthee, Jorryt J and Capak, Peter and Chartab, Nima and Hemmati, Shoubaneh and Masters, Daniel and Nayyeri, Hooshang and O’Sullivan, Donal and Paulino-Afonso, Ana and Sattari, Zahra and Shahidi, Abtin and Salvato, Mara and Lemaux, Brian C. and Fèvre, Olivier Le and Cucciati, Olga}, issn = {1538-4357}, journal = {The Astrophysical Journal}, keywords = {Space and Planetary Science, Astronomy and Astrophysics}, number = {1}, publisher = {IOP Publishing}, title = {{Spectroscopic confirmation of a coma cluster progenitor at z ∼ 2.2}}, doi = {10.3847/1538-4357/ab75c3}, volume = {892}, year = {2020}, } @article{11528, abstract = {Ly α emission lines are typically found to be redshifted with respect to the systemic redshifts of galaxies, likely due to resonant scattering of Ly α photons. Here, we measure the average velocity offset for a sample of 96 z ≈ 3.3 Ly α emitters (LAEs) with a median Ly α flux (luminosity) of ≈10−17 erg cm−2 s−1 (⁠≈1042 erg s−1⁠) and a median star formation rate (SFR) of ≈1.3 M⊙ yr−1 (not corrected for possible dust extinction), detected by the Multi-Unit Spectroscopic Explorer as part of our MUSEQuBES circumgalactic medium (CGM) survey. By postulating that the stacked CGM absorption profiles of these LAEs, probed by eight background quasars, must be centred on the systemic redshift, we measure an average velocity offset, Voffset = 171\pm 8 km s−1, between the Ly α emission peak and the systemic redshift. The observed Voffset is lower by factors of ≈1.4 and ≈2.6 compared to the velocity offsets measured for narrow-band-selected LAEs and Lyman break galaxies, respectively, which probe galaxies with higher masses and SFRs. Consistent with earlier studies based on direct measurements for individual objects, we find that the Voffset is correlated with the full width at half-maximum of the red peak of the Ly α line, and anticorrelated with the rest-frame equivalent width. Moreover, we find that Voffset is correlated with SFR with a sub-linear scaling relation, Voffset∝SFR0.16±0.03⁠. Adopting the mass scaling for main-sequence galaxies, such a relation suggests that Voffset scales with the circular velocity of the dark matter haloes hosting the LAEs.}, author = {Muzahid, Sowgat and Schaye, Joop and Marino, Raffaella Anna and Cantalupo, Sebastiano and Brinchmann, Jarle and Contini, Thierry and Wendt, Martin and Wisotzki, Lutz and Zabl, Johannes and Bouché, Nicolas and Akhlaghi, Mohammad and Chen, Hsiao-Wen and Claeyssens, Adélaîde and Johnson, Sean and Leclercq, Floriane and Maseda, Michael and Matthee, Jorryt J and Richard, Johan and Urrutia, Tanya and Verhamme, Anne}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, keywords = {Space and Planetary Science, Astronomy and Astrophysics, galaxies: haloes, galaxies: high-redshift, quasars: absorption lines}, number = {2}, pages = {1013--1022}, publisher = {Oxford University Press}, title = {{MUSEQuBES: Calibrating the redshifts of Lyα emitters using stacked circumgalactic medium absorption profiles}}, doi = {10.1093/mnras/staa1347}, volume = {496}, 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{11530, abstract = {A prediction of the classic active galactic nucleus (AGN) unification model is the presence of ionization cones with different orientations depending on the AGN type. Confirmations of this model exist for present times, but it is less clear in the early Universe. Here, we use the morphology of giant Ly α nebulae around AGNs at redshift z ∼ 3 to probe AGN emission and therefore the validity of the AGN unification model at this redshift. We compare the spatial morphology of 19 nebulae previously found around type I AGNs with a new sample of four Ly α nebulae detected around type II AGNs. Using two independent techniques, we find that nebulae around type II AGNs are more asymmetric than around type I, at least at radial distances r > 30 physical kpc (pkpc) from the ionizing source. We conclude that the type I and type II AGNs in our sample show evidence of different surrounding ionizing geometries. This suggests that the classical AGN unification model is also valid for high-redshift sources. Finally, we discuss how the lack of asymmetry in the inner parts (r ≲ 30 pkpc) and the associated high values of the He II to Ly α ratios in these regions could indicate additional sources of (hard) ionizing radiation originating within or in proximity of the AGN host galaxies. This work demonstrates that the morphologies of giant Ly α nebulae can be used to understand and study the geometry of high-redshift AGNs on circumnuclear scales and it lays the foundation for future studies using much larger statistical samples.}, author = {den Brok, J S and Cantalupo, S and Mackenzie, R and Marino, R A and Pezzulli, G and Matthee, Jorryt J and Johnson, S D and Krumpe, M and Urrutia, T and Kollatschny, W}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, keywords = {Space and Planetary Science, Astronomy and Astrophysics, galaxies: active, galaxies: high-redshift, intergalactic medium, quasars: emission lines, quasars: general}, number = {2}, pages = {1874--1887}, publisher = {Oxford University Press}, title = {{Probing the AGN unification model at redshift z ∼ 3 with MUSE observations of giant Lyα nebulae}}, doi = {10.1093/mnras/staa1269}, volume = {495}, 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{11610, abstract = {Studies of Galactic structure and evolution have benefited enormously from Gaia kinematic information, though additional, intrinsic stellar parameters like age are required to best constrain Galactic models. Asteroseismology is the most precise method of providing such information for field star populations en masse, but existing samples for the most part have been limited to a few narrow fields of view by the CoRoT and Kepler missions. In an effort to provide well-characterized stellar parameters across a wide range in Galactic position, we present the second data release of red giant asteroseismic parameters for the K2 Galactic Archaeology Program (GAP). We provide ${\nu }_{\max }$ and ${\rm{\Delta }}\nu $ based on six independent pipeline analyses; first-ascent red giant branch (RGB) and red clump (RC) evolutionary state classifications from machine learning; and ready-to-use radius and mass coefficients, κR and κM, which, when appropriately multiplied by a solar-scaled effective temperature factor, yield physical stellar radii and masses. In total, we report 4395 radius and mass coefficients, with typical uncertainties of 3.3% (stat.) ± 1% (syst.) for κR and 7.7% (stat.) ± 2% (syst.) for κM among RGB stars, and 5.0% (stat.) ± 1% (syst.) for κR and 10.5% (stat.) ± 2% (syst.) for κM among RC stars. We verify that the sample is nearly complete—except for a dearth of stars with ${\nu }_{\max }\lesssim 10\mbox{--}20\,\mu \mathrm{Hz}$—by comparing to Galactic models and visual inspection. Our asteroseismic radii agree with radii derived from Gaia Data Release 2 parallaxes to within 2.2% ± 0.3% for RGB stars and 2.0% ± 0.6% for RC stars.}, author = {Zinn, Joel C. and Stello, Dennis and Elsworth, Yvonne and García, Rafael A. and Kallinger, Thomas and Mathur, Savita and Mosser, Benoît and Bugnet, Lisa Annabelle and Jones, Caitlin and Hon, Marc and Sharma, Sanjib and Schönrich, Ralph and Warfield, Jack T. and Luger, Rodrigo and Pinsonneault, Marc H. and Johnson, Jennifer A. and Huber, Daniel and Aguirre, Victor Silva and Chaplin, William J. and Davies, Guy R. and Miglio, Andrea}, issn = {1538-4365}, journal = {The Astrophysical Journal Supplement Series}, keywords = {Space and Planetary Science, Astronomy and Astrophysics}, number = {2}, publisher = {IOP Publishing}, title = {{The K2 galactic archaeology program data release 2: Asteroseismic results from campaigns 4, 6, and 7}}, doi = {10.3847/1538-4365/abbee3}, volume = {251}, year = {2020}, } @article{11612, abstract = {Since the onset of the "space revolution" of high-precision high-cadence photometry, asteroseismology has been demonstrated as a powerful tool for informing Galactic archeology investigations. The launch of the NASA Transiting Exoplanet Survey Satellite (TESS) mission has enabled seismic-based inferences to go full sky—providing a clear advantage for large ensemble studies of the different Milky Way components. Here we demonstrate its potential for investigating the Galaxy by carrying out the first asteroseismic ensemble study of red giant stars observed by TESS. We use a sample of 25 stars for which we measure their global asteroseimic observables and estimate their fundamental stellar properties, such as radius, mass, and age. Significant improvements are seen in the uncertainties of our estimates when combining seismic observables from TESS with astrometric measurements from the Gaia mission compared to when the seismology and astrometry are applied separately. Specifically, when combined we show that stellar radii can be determined to a precision of a few percent, masses to 5%–10%, and ages to the 20% level. This is comparable to the precision typically obtained using end-of-mission Kepler data.}, author = {Aguirre, Víctor Silva and Stello, Dennis and Stokholm, Amalie and Mosumgaard, Jakob R. and Ball, Warrick H. and Basu, Sarbani and Bossini, Diego and Bugnet, Lisa Annabelle and Buzasi, Derek and Campante, Tiago L. and Carboneau, Lindsey and Chaplin, William J. and Corsaro, Enrico and Davies, Guy R. and Elsworth, Yvonne and García, Rafael A. and Gaulme, Patrick and Hall, Oliver J. and Handberg, Rasmus and Hon, Marc and Kallinger, Thomas and Kang, Liu and Lund, Mikkel N. and Mathur, Savita and Mints, Alexey and Mosser, Benoit and Çelik Orhan, Zeynep and Rodrigues, Thaíse S. and Vrard, Mathieu and Yıldız, Mutlu and Zinn, Joel C. and Örtel, Sibel and Beck, Paul G. and Bell, Keaton J. and Guo, Zhao and Jiang, Chen and Kuszlewicz, James S. and Kuehn, Charles A. and Li, Tanda and Lundkvist, Mia S. and Pinsonneault, Marc and Tayar, Jamie and Cunha, Margarida S. and Hekker, Saskia and Huber, Daniel and Miglio, Andrea and F. G. Monteiro, Mario J. P. and Slumstrup, Ditte and Winther, Mark L. and Angelou, George and Benomar, Othman and Bódi, Attila and De Moura, Bruno L. and Deheuvels, Sébastien and Derekas, Aliz and Di Mauro, Maria Pia and Dupret, Marc-Antoine and Jiménez, Antonio and Lebreton, Yveline and Matthews, Jaymie and Nardetto, Nicolas and do Nascimento, Jose D. and Pereira, Filipe and Rodríguez Díaz, Luisa F. and Serenelli, Aldo M. and Spitoni, Emanuele and Stonkutė, Edita and Suárez, Juan Carlos and Szabó, Robert and Van Eylen, Vincent and Ventura, Rita and Verma, Kuldeep and Weiss, Achim and Wu, Tao and Barclay, Thomas and Christensen-Dalsgaard, Jørgen and Jenkins, Jon M. and Kjeldsen, Hans and Ricker, George R. and Seager, Sara and Vanderspek, Roland}, issn = {1538-4357}, journal = {The Astrophysical Journal Letters}, keywords = {Space and Planetary Science, Astronomy and Astrophysics}, number = {2}, publisher = {IOP Publishing}, title = {{Detection and characterization of oscillating red giants: First results from the TESS satellite}}, doi = {10.3847/2041-8213/ab6443}, volume = {889}, year = {2020}, } @article{13460, abstract = {Binary interaction can cause stellar envelopes to be stripped, which significantly reduces the radius of the star. The orbit of a binary composed of a stripped star and a compact object can therefore be so tight that the gravitational radiation the system produces reaches frequencies accessible to the Laser Interferometer Space Antenna (LISA). Two such stripped stars in tight orbits with white dwarfs are known so far (ZTF J2130+4420 and CD−30°11223), but many more are expected to exist. These binaries provide important constraints for binary evolution models and may be used as LISA verification sources. We develop a Monte Carlo code that uses detailed evolutionary models to simulate the Galactic population of stripped stars in tight orbits with either neutron star or white dwarf companions. We predict 0–100 stripped star + white dwarf binaries and 0–4 stripped star + neutron star binaries with a signal-to-noise ratio >5 after 10 yr of observations with LISA. More than 90% of these binaries are expected to show large radial velocity shifts of ≳200 $\,\mathrm{km}\,{{\rm{s}}}^{-1}$, which are spectroscopically detectable. Photometric variability due to tidal deformation of the stripped star is also expected and has been observed in ZTF J2130+4420 and CD−30°11223. In addition, the stripped star + neutron star binaries are expected to be X-ray bright with LX ≳ 1033–1036 $\,\mathrm{erg}\,{{\rm{s}}}^{-1}$. Our results show that stripped star binaries are promising multimessenger sources for the upcoming electromagnetic and gravitational wave facilities.}, author = {Götberg, Ylva Louise Linsdotter and Korol, V. and Lamberts, A. and Kupfer, T. and Breivik, K. and Ludwig, B. and Drout, M. R.}, issn = {1538-4357}, journal = {The Astrophysical Journal}, keywords = {Space and Planetary Science, Astronomy and Astrophysics}, number = {1}, publisher = {American Astronomical Society}, title = {{Stars stripped in binaries: The living gravitational-wave sources}}, doi = {10.3847/1538-4357/abbda5}, volume = {904}, year = {2020}, } @article{13461, abstract = {High-resolution numerical simulations including feedback and aimed at calculating the escape fraction (fesc) of hydrogen-ionizing photons often assume stellar radiation based on single-stellar population synthesis models. However, strong evidence suggests the binary fraction of massive stars is ≳70%. Moreover, simulations so far have yielded values of fesc falling only on the lower end of the ∼10%–20% range, the amount presumed necessary to reionize the universe. Analyzing a high-resolution (4 pc) cosmological radiation-hydrodynamic simulation, we study how fesc changes when we include two different products of binary stellar evolution—stars stripped of their hydrogen envelopes and massive blue stragglers. Both produce significant amounts of ionizing photons 10–200 Myr after each starburst. We find the relative importance of these photons to be amplified with respect to escaped ionizing photons, because peaks in star formation rates (SFRs) and fesc are often out of phase by this 10–200 Myr. Additionally, low-mass, bursty galaxies emit Lyman continuum radiation primarily from binary products when SFRs are low. Observations of these galaxies by the James Webb Space Telescope could provide crucial information on the evolution of binary stars as a function of redshift. Overall, including stripped stars and massive blue stragglers increases our photon-weighted mean escape fraction ($\langle {f}_{\mathrm{esc}}\rangle $) by ∼13% and ∼10%, respectively, resulting in $\langle {f}_{\mathrm{esc}}\rangle =17 \% $. Our results emphasize that using updated stellar population synthesis models with binary stellar evolution provides a more sound physical basis for stellar reionization.}, author = {Secunda, Amy and Cen, Renyue and Kimm, Taysun and Götberg, Ylva Louise Linsdotter and de Mink, Selma E.}, issn = {1538-4357}, journal = {The Astrophysical Journal}, keywords = {Space and Planetary Science, Astronomy and Astrophysics}, number = {1}, publisher = {American Astronomical Society}, title = {{Delayed photons from binary evolution help reionize the universe}}, doi = {10.3847/1538-4357/abaefa}, volume = {901}, year = {2020}, } @article{13463, abstract = {Present and upcoming time-domain astronomy efforts, in part driven by gravitational-wave follow-up campaigns, will unveil a variety of rare explosive transients in the sky. Here, we focus on pulsational pair-instability evolution, which can result in signatures that are observable with electromagnetic and gravitational waves. We simulated grids of bare helium stars to characterize the resulting black hole (BH) masses together with the ejecta composition, velocity, and thermal state. We find that the stars do not react “elastically” to the thermonuclear ignition in the core: there is not a one-to-one correspondence between pair-instability driven ignition and mass ejections, which causes ambiguity as to what is an observable pulse. In agreement with previous studies, we find that for initial helium core masses of 37.5 M⊙ ≲ MHe, init ≲ 41 M⊙, corresponding to carbon-oxygen core masses 27.5 M⊙ ≲ MCO ≲ 30.1 M⊙, the explosions are not strong enough to affect the surface. With increasing initial helium core mass, they become progressively stronger causing first large radial expansion (41 M⊙ ≲ MHe, init ≲ 42 M⊙, corresponding to 30.1 M⊙ ≲ MCO ≲ 30.8 M⊙) and, finally, also mass ejection episodes (for MHe, init ≳ 42 M⊙, or MCO ≳ 30.8 M⊙). The lowest mass helium core to be fully disrupted in a pair-instability supernova is MHe, init ≃ 80 M⊙, corresponding to MCO ≃ 55 M⊙. Models with MHe, init ≳ 200 M⊙ (MCO ≳ 114 M⊙) reach the photodisintegration regime, resulting in BHs with masses of MBH ≳ 125 M⊙. Although this is currently considered unlikely, if BHs from these models form via (weak) explosions, the previously-ejected material might be hit by the blast wave and convert kinetic energy into observable electromagnetic radiation. We characterize the hydrogen-free circumstellar material from the pulsational pair-instability of helium cores by simply assuming that the ejecta maintain a constant velocity after ejection. We find that our models produce helium-rich ejecta with mass of 10−3 M⊙ ≲ MCSM ≲ 40 M⊙, the larger values corresponding to the more massive progenitor stars. These ejecta are typically launched at a few thousand km s−1 and reach distances of ∼1012 − 1015 cm before the core-collapse of the star. The delays between mass ejection events and the final collapse span a wide and mass-dependent range (from subhour to 104 years), and the shells ejected can also collide with each other, powering supernova impostor events before the final core-collapse. The range of properties we find suggests a possible connection with (some) type Ibn supernovae.}, author = {Renzo, M. and Farmer, R. and Justham, S. and Götberg, Ylva Louise Linsdotter and de Mink, S. E. and Zapartas, E. and Marchant, P. and Smith, N.}, issn = {1432-0746}, journal = {Astronomy & Astrophysics}, keywords = {Space and Planetary Science, Astronomy and Astrophysics}, publisher = {EDP Sciences}, title = {{Predictions for the hydrogen-free ejecta of pulsational pair-instability supernovae}}, doi = {10.1051/0004-6361/202037710}, volume = {640}, year = {2020}, } @article{13464, abstract = {Massive binaries that merge as compact objects are the progenitors of gravitational-wave sources. Most of these binaries experience one or more phases of mass transfer, during which one of the stars loses all or part of its outer envelope and becomes a stripped-envelope star. The evolution of the size of these stripped stars is crucial in determining whether they experience further interactions and understanding their ultimate fate. We present new calculations of stripped-envelope stars based on binary evolution models computed with MESA. We use these to investigate their radius evolution as a function of mass and metallicity. We further discuss their pre-supernova observable characteristics and potential consequences of their evolution on the properties of supernovae from stripped stars. At high metallicity, we find that practically all of the hydrogen-rich envelope is removed, which is in agreement with earlier findings. Only progenitors with initial masses below 10 M⊙ expand to large radii (up to 100 R⊙), while more massive progenitors remain compact. At low metallicity, a substantial amount of hydrogen remains and the progenitors can, in principle, expand to giant sizes (> 400 R⊙) for all masses we consider. This implies that they can fill their Roche lobe anew. We show that the prescriptions commonly used in population synthesis models underestimate the stellar radii by up to two orders of magnitude. We expect that this has consequences for the predictions for gravitational-wave sources from double neutron star mergers, particularly with regard to their metallicity dependence.}, author = {Laplace, E. and Götberg, Ylva Louise Linsdotter and de Mink, S. E. and Justham, S. and Farmer, R.}, issn = {1432-0746}, journal = {Astronomy & Astrophysics}, keywords = {Space and Planetary Science, Astronomy and Astrophysics}, publisher = {EDP Sciences}, title = {{The expansion of stripped-envelope stars: Consequences for supernovae and gravitational-wave progenitors}}, doi = {10.1051/0004-6361/201937300}, volume = {637}, year = {2020}, } @article{13465, abstract = {Gravitational-wave detections are now probing the black hole (BH) mass distribution, including the predicted pair-instability mass gap. These data require robust quantitative predictions, which are challenging to obtain. The most massive BH progenitors experience episodic mass ejections on time-scales shorter than the convective turnover time-scale. This invalidates the steady-state assumption on which the classic mixing length theory relies. We compare the final BH masses computed with two different versions of the stellar evolutionary code MESA ⁠: (i) using the default implementation of Paxton et al. (2018) and (ii) solving an additional equation accounting for the time-scale for convective deceleration. In the second grid, where stronger convection develops during the pulses and carries part of the energy, we find weaker pulses. This leads to lower amounts of mass being ejected and thus higher final BH masses of up to ∼5M⊙ ⁠. The differences are much smaller for the progenitors that determine the maximum mass of BHs below the gap. This prediction is robust at MBH,max≃48M⊙ ⁠, at least within the idealized context of this study. This is an encouraging indication that current models are robust enough for comparison with the present-day gravitational-wave detections. However, the large differences between individual models emphasize the importance of improving the treatment of convection in stellar models, especially in the light of the data anticipated from the third generation of gravitational-wave detectors.}, author = {Renzo, M and Farmer, R J and Justham, S and de Mink, S E and Götberg, Ylva Louise Linsdotter and Marchant, P}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, keywords = {Space and Planetary Science, Astronomy and Astrophysics}, number = {3}, pages = {4333--4341}, publisher = {Oxford University Press}, title = {{Sensitivity of the lower edge of the pair-instability black hole mass gap to the treatment of time-dependent convection}}, doi = {10.1093/mnras/staa549}, volume = {493}, year = {2020}, } @article{13467, abstract = {Massive stars are often found in binary systems, and it has been argued that binary products boost the ionizing radiation of stellar populations. Accurate predictions for binary products are needed to understand and quantify their contribution to cosmic reionization. We investigate the contribution of stars stripped in binaries because (1) they are, arguably, the best-understood products of binary evolution, (2) we recently produced the first radiative transfer calculations for the atmospheres of these stripped stars that predict their ionizing spectra, and (3) they are very promising sources because they boost the ionizing emission of stellar populations at late times. This allows stellar feedback to clear the surroundings such that a higher fraction of their photons can escape and ionize the intergalactic medium. Combining our detailed predictions for the ionizing spectra with a simple cosmic reionization model, we estimate that stripped stars contributed tens of percent of the photons that caused cosmic reionization of hydrogen, depending on the assumed escape fractions. More importantly, stripped stars harden the ionizing emission. We estimate that the spectral index for the ionizing part of the spectrum can increase to −1 compared to ≲ − 2 for single stars. At high redshift, stripped stars and massive single stars combined dominate the He II-ionizing emission, but we expect that active galactic nuclei drive cosmic helium reionization. Further observational consequences we expect are (1) high ionization states for the intergalactic gas surrounding stellar systems, such as C IV and Si IV, and (2) additional heating of the intergalactic medium of up to a few thousand Kelvin. Quantifying these warrants the inclusion of accurate models for stripped stars and other binary products in full cosmological simulations.}, author = {Götberg, Ylva Louise Linsdotter and de Mink, S. E. and McQuinn, M. and Zapartas, E. and Groh, J. H. and Norman, C.}, issn = {1432-0746}, journal = {Astronomy & Astrophysics}, keywords = {Space and Planetary Science, Astronomy and Astrophysics}, publisher = {EDP Sciences}, title = {{Contribution from stars stripped in binaries to cosmic reionization of hydrogen and helium}}, doi = {10.1051/0004-6361/201936669}, volume = {634}, 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{11505, abstract = {Contact. This paper presents the results obtained with the Multi-Unit Spectroscopic Explorer (MUSE) at the ESO Very Large Telescope on the faint end of the Lyman-alpha luminosity function (LF) based on deep observations of four lensing clusters. The goal of our project is to set strong constraints on the relative contribution of the Lyman-alpha emitter (LAE) population to cosmic reionization. Aims. The precise aim of the present study is to further constrain the abundance of LAEs by taking advantage of the magnification provided by lensing clusters to build a blindly selected sample of galaxies which is less biased than current blank field samples in redshift and luminosity. By construction, this sample of LAEs is complementary to those built from deep blank fields, whether observed by MUSE or by other facilities, and makes it possible to determine the shape of the LF at fainter levels, as well as its evolution with redshift. Methods. We selected a sample of 156 LAEs with redshifts between 2.9 ≤ z ≤ 6.7 and magnification-corrected luminosities in the range 39 ≲ log LLyα [erg s−1] ≲43. To properly take into account the individual differences in detection conditions between the LAEs when computing the LF, including lensing configurations, and spatial and spectral morphologies, the non-parametric 1/Vmax method was adopted. The price to pay to benefit from magnification is a reduction of the effective volume of the survey, together with a more complex analysis procedure to properly determine the effective volume Vmax for each galaxy. In this paper we present a complete procedure for the determination of the LF based on IFU detections in lensing clusters. This procedure, including some new methods for masking, effective volume integration and (individual) completeness determinations, has been fully automated when possible, and it can be easily generalized to the analysis of IFU observations in blank fields. Results. As a result of this analysis, the Lyman-alpha LF has been obtained in four different redshift bins: 2.9 <  z <  6, 7, 2.9 <  z <  4.0, 4.0 <  z <  5.0, and 5.0 <  z <  6.7 with constraints down to log LLyα = 40.5. From our data only, no significant evolution of LF mean slope can be found. When performing a Schechter analysis also including data from the literature to complete the present sample towards the brightest luminosities, a steep faint end slope was measured varying from α = −1.69−0.08+0.08 to α = −1.87−0.12+0.12 between the lowest and the highest redshift bins. Conclusions. The contribution of the LAE population to the star formation rate density at z ∼ 6 is ≲50% depending on the luminosity limit considered, which is of the same order as the Lyman-break galaxy (LBG) contribution. The evolution of the LAE contribution with redshift depends on the assumed escape fraction of Lyman-alpha photons, and appears to slightly increase with increasing redshift when this fraction is conservatively set to one. Depending on the intersection between the LAE/LBG populations, the contribution of the observed galaxies to the ionizing flux may suffice to keep the universe ionized at z ∼ 6.}, author = {de La Vieuville, G. and Bina, D. and Pello, R. and Mahler, G. and Richard, J. and Drake, A. B. and Herenz, E. C. and Bauer, F. E. and Clément, B. and Lagattuta, D. and Laporte, N. and Martinez, J. and Patrício, V. and Wisotzki, L. and Zabl, J. and Bouwens, R. J. and Contini, T. and Garel, T. and Guiderdoni, B. and Marino, R. A. and Maseda, M. V. and Matthee, Jorryt J and Schaye, J. and Soucail, G.}, issn = {1432-0746}, journal = {Astronomy & Astrophysics}, keywords = {Space and Planetary Science, Astronomy and Astrophysics, gravitational lensing: strong / galaxies: high-redshift / dark ages, reionization, first stars / galaxies: clusters: general / galaxies: luminosity function, mass function}, publisher = {EDP Sciences}, title = {{Faint end of the z ∼ 3–7 luminosity function of Lyman-alpha emitters behind lensing clusters observed with MUSE}}, doi = {10.1051/0004-6361/201834471}, volume = {628}, year = {2019}, }