@article{13443,
  abstract     = {The ages of solar-like stars have been at the center of many studies such as exoplanet characterization or Galactic-archeology. While ages are usually computed from stellar evolution models, relations linking ages to other stellar properties, such as rotation and magnetic activity, have been investigated. With the large catalog of 55,232 rotation periods, Prot, and photometric magnetic activity index, Sph from Kepler data, we have the opportunity to look for such magneto-gyro-chronology relations. Stellar ages are obtained with two stellar evolution codes that include treatment of angular momentum evolution, hence using Prot as input in addition to classical atmospheric parameters. We explore two different ways of predicting stellar ages on three subsamples with spectroscopic observations: solar analogs, late-F and G dwarfs, and K dwarfs. We first perform a Bayesian analysis to derive relations between Sph and ages between 1 and 5 Gyr, and other stellar properties. For late-F and G dwarfs, and K dwarfs, the multivariate regression favors the model with Prot and Sph with median differences of 0.1% and 0.2%, respectively. We also apply Machine Learning techniques with a Random Forest algorithm to predict ages up to 14 Gyr with the same set of input parameters. For late-F, G and K dwarfs together, predicted ages are on average within 5.3% of the model ages and improve to 3.1% when including Prot. These are very promising results for a quick age estimation for solar-like stars with photometric observations, especially with current and future space missions.},
  author       = {Mathur, Savita and Claytor, Zachary R. and Santos, Ângela R. G. and García, Rafael A. and Amard, Louis and Bugnet, Lisa Annabelle and Corsaro, Enrico and Bonanno, Alfio and Breton, Sylvain N. and Godoy-Rivera, Diego and Pinsonneault, Marc H. and van Saders, Jennifer},
  issn         = {1538-4357},
  journal      = {The Astrophysical Journal},
  keywords     = {Space and Planetary Science, Astronomy and Astrophysics},
  number       = {2},
  publisher    = {American Astronomical Society},
  title        = {{Magnetic activity evolution of solar-like stars. I. Sph–age relation derived from Kepler observations}},
  doi          = {10.3847/1538-4357/acd118},
  volume       = {952},
  year         = {2023},
}

@article{13450,
  abstract     = {In previous work, we identified a population of 38 cool and luminous variable stars in the Magellanic Clouds and examined 11 in detail in order to classify them as either Thorne–Żytkow objects (TŻOs; red supergiants with a neutron star cores) or super-asymptotic giant branch (sAGB) stars (the most massive stars that will not undergo core collapse). This population includes HV 2112, a peculiar star previously considered in other works to be either a TŻO or high-mass asymptotic giant branch (AGB) star. Here we continue this investigation, using the kinematic and radio environments and local star formation history of these stars to place constraints on the age of the progenitor systems and the presence of past supernovae. These stars are not associated with regions of recent star formation, and we find no evidence of past supernovae at their locations. Finally, we also assess the presence of heavy elements and lithium in their spectra compared to red supergiants. We find strong absorption in Li and s-process elements compared to RSGs in most of the sample, consistent with sAGB nucleosynthesis, while HV 2112 shows additional strong lines associated with TŻO nucleosynthesis. Coupled with our previous mass estimates, the results are consistent with the stars being massive (∼4–6.5 M⊙) or sAGB (∼6.5–12 M⊙) stars in the thermally pulsing phase, providing crucial observations of the transition between low- and high-mass stellar populations. HV 2112 is more ambiguous; it could either be a maximally massive sAGB star, or a TŻO if the minimum mass for stability extends down to ≲13 M⊙.},
  author       = {O‘Grady, Anna J. G. and Drout, Maria R. and Gaensler, B. M. and Kochanek, C. S. and Neugent, Kathryn F. and Doherty, Carolyn L. and Speagle, Joshua S. and Shappee, B. J. and Rauch, Michael and Götberg, Ylva Louise Linsdotter and Ludwig, Bethany and Thompson, Todd A.},
  issn         = {1538-4357},
  journal      = {The Astrophysical Journal},
  keywords     = {Space and Planetary Science, Astronomy and Astrophysics},
  number       = {1},
  publisher    = {American Astronomical Society},
  title        = {{Cool, luminous, and highly variable stars in the Magellanic Clouds. II. Spectroscopic and environmental analysis of Thorne–Żytkow object and super-AGB star candidates}},
  doi          = {10.3847/1538-4357/aca655},
  volume       = {943},
  year         = {2023},
}

@article{11509,
  abstract     = {We present Keck/LRIS follow-up spectroscopy for 13 photometric candidates of extremely metal-poor galaxies (EMPGs) selected by a machine-learning technique applied to the deep (∼26 AB mag) optical and wide-area (∼500 deg2) Subaru imaging data in the EMPRESS survey. Nine out of the 13 candidates are EMPGs with an oxygen abundance (O/H) less than ∼10% solar value (O/H)⊙, and four sources are contaminants of moderately metal-rich galaxies or no emission-line objects. Notably, two out of the nine EMPGs have extremely low stellar masses and oxygen abundances of 5 × 10⁴x–7 × -10⁵ M⊙ and 2%–3% (O/H)⊙, respectively. With a sample of five EMPGs with (Fe/O) measurements, two (three) of which are taken from this study (the literature), we confirm that two EMPGs with the lowest (O/H) ratios of ∼2% (O/H)⊙ show high (Fe/O) ratios of ∼0.1, close to the solar abundance ratio. Comparing galaxy chemical enrichment models, we find that the two EMPGs cannot be explained by a scenario of metal-poor gas accretion/episodic star formation history due to their low (N/O) ratios. We conclude that the two EMPGs can be reproduced by the inclusion of bright hypernovae and/or hypothetical pair-instability supernovae (SNe) preferentially produced in a metal-poor environment. This conclusion implies that primordial galaxies at z ∼ 10 could have a high abundance of Fe that did not originate from Type Ia SNe with delays and that Fe may not serve as a cosmic clock for primordial galaxies.},
  author       = {Isobe, Yuki and Ouchi, Masami and Suzuki, Akihiro and Moriya, Takashi J. and Nakajima, Kimihiko and Nomoto, Ken’ichi and Rauch, Michael and Harikane, Yuichi and Kojima, Takashi and Ono, Yoshiaki and Fujimoto, Seiji and Inoue, Akio K. and Kim, Ji Hoon and Komiyama, Yutaka and Kusakabe, Haruka and Lee, Chien-Hsiu and Maseda, Michael and Matthee, Jorryt J and Michel-Dansac, Leo and Nagao, Tohru and Nanayakkara, Themiya and Nishigaki, Moka and Onodera, Masato and Sugahara, Yuma and Xu, Yi},
  issn         = {1538-4357},
  journal      = {The Astrophysical Journal},
  keywords     = {Space and Planetary Science, Astronomy and Astrophysics},
  number       = {2},
  publisher    = {IOP Publishing},
  title        = {{EMPRESS. IV. Extremely metal-poor galaxies including very low-mass primordial systems with M∗= 10⁴-10⁵⊙ and 2%–3% (O/H): High (Fe/O) suggestive of metal enrichment by hypernovae/pair-instability supernovae}},
  doi          = {10.3847/1538-4357/ac3509},
  volume       = {925},
  year         = {2022},
}

@article{11510,
  abstract     = {Galaxy evolution is driven by a variety of physical processes that are predicted to proceed at different rates for different dark matter haloes and environments across cosmic times. A record of this evolution is preserved in galaxy stellar populations, which we can access using absorption-line spectroscopy. Here we explore the large LEGA-C survey (DR3) to investigate the role of the environment and stellar mass on stellar populations at z ∼ 0.6–1 in the COSMOS field. Leveraging the statistical power and depth of LEGA-C, we reveal significant gradients in Dn4000 and Hδ equivalent widths (EWs) distributions over the stellar mass versus environment 2D spaces for the massive galaxy population (M > 1010 M⊙) at z ∼ 0.6–1.0. Dn4000 and Hδ EWs primarily depend on stellar mass, but they also depend on environment at fixed stellar mass. By splitting the sample into centrals and satellites, and in terms of star-forming galaxies and quiescent galaxies, we reveal that the significant environmental trends of Dn4000 and Hδ EW, when controlling for stellar mass, are driven by quiescent galaxies. Regardless of being centrals or satellites, star-forming galaxies reveal Dn4000 and Hδ EWs, which depend strongly on their stellar mass and are completely independent of the environment at 0.6 < z < 1.0. The environmental trends seen for satellite galaxies are fully driven by the trends that hold only for quiescent galaxies, combined with the strong environmental dependency of the quiescent fraction at fixed stellar mass. Our results are consistent with recent predictions from simulations that point toward massive galaxies forming first in overdensities or the most compact dark matter haloes.},
  author       = {Sobral, David and van der Wel, Arjen and Bezanson, Rachel and Bell, Eric and Muzzin, Adam and D’Eugenio, Francesco and Darvish, Behnam and Gallazzi, Anna and Wu, Po-Feng and Maseda, Michael and Matthee, Jorryt J and Paulino-Afonso, Ana and Straatman, Caroline and van Dokkum, Pieter G.},
  issn         = {1538-4357},
  journal      = {The Astrophysical Journal},
  keywords     = {Space and Planetary Science, Astronomy and Astrophysics},
  number       = {2},
  publisher    = {IOP Publishing},
  title        = {{The LEGA-C of nature and nurture in stellar populations at z ∼ 0.6–1.0: Dn4000 and Hδ reveal different assembly histories for quiescent galaxies in different environments}},
  doi          = {10.3847/1538-4357/ac4419},
  volume       = {926},
  year         = {2022},
}

@article{11511,
  abstract     = {The ratio of α-elements to iron in galaxies holds valuable information about the star formation history (SFH) since their enrichment occurs on different timescales. The fossil record of stars in galaxies has mostly been excavated for passive galaxies, since the light of star-forming galaxies is dominated by young stars, which have much weaker atmospheric absorption features. Here we use the largest reference cosmological simulation of the EAGLE project to investigate the origin of variations in stellar α-enhancement among star-forming galaxies at z = 0, and their impact on integrated spectra. The definition of α-enhancement in a composite stellar population is ambiguous. We elucidate two definitions—termed “mean” and “galactic” α-enhancement—in more detail. While a star-forming galaxy has a high “mean” α-enhancement when its stars formed rapidly, a galaxy with a large “galactic” α-enhancement generally had a delayed SFH. We find that absorption-line strengths of Mg and Fe correlate with variations in α-enhancement. These correlations are strongest for the “galactic” α-enhancement. However, we show that these are mostly caused by other effects that are cross-correlated with α-enhancement, such as variations in the light-weighted age. This severely complicates the retrieval of α-enhancements in star-forming galaxies. The ambiguity is not severe for passive galaxies, and we confirm that spectral variations in these galaxies are caused by measurable variations in α-enhancements. We suggest that this more complex coupling between α-enhancement and SFHs can guide the interpretation of new observations of star-forming galaxies.},
  author       = {Gebek, Andrea and Matthee, Jorryt J},
  issn         = {1538-4357},
  journal      = {The Astrophysical Journal},
  keywords     = {Space and Planetary Science, Astronomy and Astrophysics},
  number       = {2},
  publisher    = {IOP Publishing},
  title        = {{On the variation in stellar α-enhancements of star-forming galaxies in the EAGLE simulation}},
  doi          = {10.3847/1538-4357/ac350b},
  volume       = {924},
  year         = {2022},
}

@article{11601,
  abstract     = {We present the third and final data release of the K2 Galactic Archaeology Program (K2 GAP) for Campaigns C1–C8 and C10–C18. We provide asteroseismic radius and mass coefficients, κR and κM, for ∼19,000 red giant stars, which translate directly to radius and mass given a temperature. As such, K2 GAP DR3 represents the largest asteroseismic sample in the literature to date. K2 GAP DR3 stellar parameters are calibrated to be on an absolute parallactic scale based on Gaia DR2, with red giant branch and red clump evolutionary state classifications provided via a machine-learning approach. Combining these stellar parameters with GALAH DR3 spectroscopy, we determine asteroseismic ages with precisions of ∼20%–30% and compare age-abundance relations to Galactic chemical evolution models among both low- and high-α populations for α, light, iron-peak, and neutron-capture elements. We confirm recent indications in the literature of both increased Ba production at late Galactic times as well as significant contributions to r-process enrichment from prompt sources associated with, e.g., core-collapse supernovae. With an eye toward other Galactic archeology applications, we characterize K2 GAP DR3 uncertainties and completeness using injection tests, suggesting that K2 GAP DR3 is largely unbiased in mass/age, with uncertainties of 2.9% (stat.) ± 0.1% (syst.) and 6.7% (stat.) ± 0.3% (syst.) in κR and κM for red giant branch stars and 4.7% (stat.) ± 0.3% (syst.) and 11% (stat.) ± 0.9% (syst.) for red clump stars. We also identify percent-level asteroseismic systematics, which are likely related to the time baseline of the underlying data, and which therefore should be considered in TESS asteroseismic analysis.},
  author       = {Zinn, Joel C. and Stello, Dennis and Elsworth, Yvonne and García, Rafael A. and Kallinger, Thomas and Mathur, Savita and Mosser, Benoît and Hon, Marc and Bugnet, Lisa Annabelle and Jones, Caitlin and Reyes, Claudia and Sharma, Sanjib and Schönrich, Ralph and Warfield, Jack T. and Luger, Rodrigo and Vanderburg, Andrew and Kobayashi, Chiaki and Pinsonneault, Marc H. and Johnson, Jennifer A. and Huber, Daniel and Buder, Sven and Joyce, Meridith and Bland-Hawthorn, Joss and Casagrande, Luca and Lewis, Geraint F. and Miglio, Andrea and Nordlander, Thomas and Davies, Guy R. and Silva, Gayandhi De and Chaplin, William J. and Silva Aguirre, Victor},
  issn         = {1538-4357},
  journal      = {The Astrophysical Journal},
  keywords     = {Space and Planetary Science, Astronomy and Astrophysics},
  number       = {2},
  publisher    = {IOP Publishing},
  title        = {{The K2 Galactic Archaeology Program data release 3: Age-abundance patterns in C1–C8 and C10–C18}},
  doi          = {10.3847/1538-4357/ac2c83},
  volume       = {926},
  year         = {2022},
}

@article{13445,
  abstract     = {Rotation is typically assumed to induce strictly symmetric rotational splitting into the rotational multiplets of pure p- and g-modes. However, for evolved stars exhibiting mixed modes, avoided crossings between different multiplet components are known to yield asymmetric rotational splitting, in particular for near-degenerate mixed-mode pairs, where notional pure p-modes are fortuitously in resonance with pure g-modes. These near-degeneracy effects have been described in subgiants, but their consequences for the characterization of internal rotation in red giants have not previously been investigated in detail, in part owing to theoretical intractability. We employ new developments in the analytic theory of mixed-mode coupling to study these near-resonance phenomena. In the vicinity of the most p-dominated mixed modes, the near-degenerate intrinsic asymmetry from pure rotational splitting increases dramatically over the course of stellar evolution, and it depends strongly on the mode-mixing fraction ζ. We also find that a linear treatment of rotation remains viable for describing the underlying p- and g-modes, even when it does not for the resulting mixed modes undergoing these avoided crossings. We explore observational consequences for potential measurements of asymmetric mixed-mode splitting, which has been proposed as a magnetic-field diagnostic. Finally, we propose improved measurement techniques for rotational characterization, exploiting the linearity of rotational effects on the underlying p/g-modes, while still accounting for these mixed-mode coupling effects.},
  author       = {Ong, J. M. Joel and Bugnet, Lisa Annabelle and Basu, Sarbani},
  issn         = {1538-4357},
  journal      = {The Astrophysical Journal},
  keywords     = {Space and Planetary Science, Astronomy and Astrophysics},
  number       = {1},
  publisher    = {American Astronomical Society},
  title        = {{Mode mixing and rotational splittings. I. Near-degeneracy effects revisited}},
  doi          = {10.3847/1538-4357/ac97e7},
  volume       = {940},
  year         = {2022},
}

@article{13451,
  abstract     = {We characterize massive stars (M > 8 M⊙) in the nearby (D ∼ 0.8 Mpc) extremely metal-poor (Z ∼ 5% Z⊙) galaxy Leo A using Hubble Space Telescope ultraviolet (UV), optical, and near-infrared (NIR) imaging along with Keck/Low-Resolution Imaging Spectrograph and MMT/Binospec optical spectroscopy for 18 main-sequence OB stars. We find that: (a) 12 of our 18 stars show emission lines, despite not being associated with an H ii region, suggestive of stellar activity (e.g., mass loss, accretion, binary star interaction), which is consistent with previous predictions of enhanced activity at low metallicity; (b) six are Be stars, which are the first to be spectroscopically studied at such low metallicity—these Be stars have unusual panchromatic SEDs; (c) for stars well fit by the TLUSTY nonlocal thermodynamic equilibrium models, the photometric and spectroscopic values of $\mathrm{log}({T}_{\mathrm{eff}})$ and $\mathrm{log}(g)$ agree to within ∼0.01 dex and ∼0.18 dex, respectively, indicating that near-UV/optical/NIR imaging can be used to reliably characterize massive (M ∼ 8–30 M⊙) main-sequence star properties relative to optical spectroscopy; (d) the properties of the most-massive stars in H II regions are consistent with constraints from previous nebular emission line studies; and (e) 13 stars with M > 8M⊙ are >40 pc from a known star cluster or H II region. Our sample comprises ∼50% of all known massive stars at Z ≲ 10% Z⊙with derived stellar parameters, high-quality optical spectra, and panchromatic photometry.},
  author       = {Gull, Maude and Weisz, Daniel R. and Senchyna, Peter and Sandford, Nathan R. and Choi, Yumi and McLeod, Anna F. and El-Badry, Kareem and Götberg, Ylva Louise Linsdotter and Gilbert, Karoline M. and Boyer, Martha and Dalcanton, Julianne J. and GuhaThakurta, Puragra and Goldman, Steven and Marigo, Paola and McQuinn, Kristen B. W. and Pastorelli, Giada and Stark, Daniel P. and Skillman, Evan and Ting, Yuan-sen and Williams, Benjamin F.},
  issn         = {1538-4357},
  journal      = {The Astrophysical Journal},
  keywords     = {Space and Planetary Science, Astronomy and Astrophysics},
  number       = {2},
  publisher    = {American Astronomical Society},
  title        = {{A panchromatic study of massive stars in the extremely metal-poor local group dwarf galaxy Leo A}},
  doi          = {10.3847/1538-4357/aca295},
  volume       = {941},
  year         = {2022},
}

@article{11512,
  abstract     = {We study the molecular gas content of 24 star-forming galaxies at z = 3–4, with a median stellar mass of 109.1 M⊙, from the MUSE Hubble Ultra Deep Field (HUDF) Survey. Selected by their Lyα λ1216 emission and HF160W-band magnitude, the galaxies show an average $\langle {\mathrm{EW}}_{\mathrm{Ly}\alpha }^{0}\rangle \approx 20$ Å, below the typical selection threshold for Lyα emitters (${\mathrm{EW}}_{\mathrm{Ly}\alpha }^{0}\gt 25$ Å), and a rest-frame UV spectrum similar to Lyman-break galaxies. We use rest-frame optical spectroscopy from KMOS and MOSFIRE, and the UV features observed with MUSE, to determine the systemic redshifts, which are offset from Lyα by 〈Δv(Lyα)〉 = 346 km s−1, with a 100 to 600 km s−1 range. Stacking 12CO J = 4 → 3 and [C i]3P1 → 3P0 (and higher-J CO lines) from the ALMA Spectroscopic Survey of the HUDF, we determine 3σ upper limits on the line luminosities of 4.0 × 108 K km s−1pc2 and 5.6 × 108 K km s−1pc2, respectively (for a 300 km s−1 line width). Stacking the 1.2 mm and 3 mm dust-continuum flux densities, we find a 3σ upper limits of 9 μJy and 1.2 μJy, respectively. The inferred gas fractions, under the assumption of a "Galactic" CO-to-H2 conversion factor and gas-to-dust ratio, are in tension with previously determined scaling relations. This implies a substantially higher αCO ≥ 10 and δGDR ≥ 1200, consistent with the subsolar metallicity estimated for these galaxies ($12+\mathrm{log}({\rm{O}}/{\rm{H}})\approx 7.8\pm 0.2$). The low metallicity of z ≥ 3 star-forming galaxies may thus make it very challenging to unveil their cold gas through CO or dust emission, warranting further exploration of alternative tracers, such as [C ii].},
  author       = {Boogaard, Leindert A. and Bouwens, Rychard J. and Riechers, Dominik and van der Werf, Paul and Bacon, Roland and Matthee, Jorryt J and Stefanon, Mauro and Feltre, Anna and Maseda, Michael and Inami, Hanae and Aravena, Manuel and Brinchmann, Jarle and Carilli, Chris and Contini, Thierry and Decarli, Roberto and González-López, Jorge and Nanayakkara, Themiya and Walter, Fabian},
  issn         = {1538-4357},
  journal      = {The Astrophysical Journal},
  keywords     = {Space and Planetary Science, Astronomy and Astrophysics},
  number       = {1},
  publisher    = {IOP Publishing},
  title        = {{Measuring the average molecular gas content of star-forming galaxies at z = 3–4}},
  doi          = {10.3847/1538-4357/ac01d7},
  volume       = {916},
  year         = {2021},
}

@article{13453,
  abstract     = {Most massive stars are born in binaries close enough for mass transfer episodes. These modify the appearance, structure, and future evolution of both stars. We compute the evolution of a 100-day-period binary, consisting initially of a 25 M⊙ star and a 17 M⊙ star, which experiences stable mass transfer. We focus on the impact of mass accretion on the surface composition, internal rotation, and structure of the accretor. To anchor our models, we show that our accretor broadly reproduces the properties of ζ Ophiuchi, which has long been proposed to have accreted mass before being ejected as a runaway star when the companion exploded. We compare our accretor to models of single rotating stars and find that the later and stronger spin-up provided by mass accretion produces significant differences. Specifically, the core of the accretor retains higher spin at the end of the main sequence, and a convective layer develops that changes its density profile. Moreover, the surface of the accretor star is polluted by CNO-processed material donated by the companion. Our models show effects of mass accretion in binaries that are not captured in single rotating stellar models. This possibly impacts the further evolution (either in a binary or as single stars), the final collapse, and the resulting spin of the compact object.},
  author       = {Renzo, M. and Götberg, Ylva Louise Linsdotter},
  issn         = {1538-4357},
  journal      = {The Astrophysical Journal},
  keywords     = {Space and Planetary Science, Astronomy and Astrophysics},
  number       = {2},
  publisher    = {American Astronomical Society},
  title        = {{Evolution of accretor stars in massive binaries: Broader implications from modeling ζ Ophiuchi}},
  doi          = {10.3847/1538-4357/ac29c5},
  volume       = {923},
  year         = {2021},
}

@article{13454,
  abstract     = {Helium star–carbon-oxygen white dwarf (CO WD) binaries are potential single-degenerate progenitor systems of thermonuclear supernovae. Revisiting a set of binary evolution calculations using the stellar evolution code MESA, we refine our previous predictions about which systems can lead to a thermonuclear supernova and then characterize the properties of the helium star donor at the time of explosion. We convert these model properties to near-UV/optical magnitudes assuming a blackbody spectrum and support this approach using a matched stellar atmosphere model. These models will be valuable to compare with pre-explosion imaging for future supernovae, though we emphasize the observational difficulty of detecting extremely blue companions. The pre-explosion source detected in association with SN 2012Z has been interpreted as a helium star binary containing an initially ultra-massive WD in a multiday orbit. However, extending our binary models to initial CO WD masses of up to 1.2 M⊙, we find that these systems undergo off-center carbon ignitions and thus are not expected to produce thermonuclear supernovae. This tension suggests that, if SN 2012Z is associated with a helium star–WD binary, then the pre-explosion optical light from the system must be significantly modified by the binary environment and/or the WD does not have a carbon-rich interior composition.},
  author       = {Wong, Tin Long Sunny and Schwab, Josiah and Götberg, Ylva Louise Linsdotter},
  issn         = {1538-4357},
  journal      = {The Astrophysical Journal},
  keywords     = {Space and Planetary Science, Astronomy and Astrophysics},
  number       = {2},
  publisher    = {American Astronomical Society},
  title        = {{Pre-explosion properties of Helium star donors to thermonuclear supernovae}},
  doi          = {10.3847/1538-4357/ac27ae},
  volume       = {922},
  year         = {2021},
}

@article{13456,
  abstract     = {While most simulations of the epoch of reionization have focused on single-stellar populations in star-forming dwarf galaxies, products of binary evolution are expected to significantly contribute to emissions of hydrogen-ionizing photons. Among these products are stripped stars (or helium stars), which have their envelopes stripped from interactions with binary companions, leaving an exposed helium core. Previous work has suggested these stripped stars can dominate the Lyman Continuum (LyC) photon output of high-redshift, low-luminosity galaxies post-starburst. Other sources of hard radiation in the early universe include zero-metallicity Population iii stars, which may have similar spectral energy distribution (SED) properties to galaxies with radiation dominated by stripped-star emissions. Here, we use four metrics (the power-law exponent over wavelength intervals 240–500 Å, 600–900 Å, and 1200–2000 Å, and the ratio of total luminosity in FUV wavelengths to LyC wavelengths) to compare the SEDs of simulated galaxies with only single-stellar evolution, galaxies containing stripped stars, and galaxies containing Population iii stars, with four different initial mass functions (IMFs). We find that stripped stars significantly alter SEDs in the LyC range of galaxies at the epoch of reionization. SEDs in galaxies with stripped stars have lower power-law indices in the LyC range and lower FUV to LyC luminosity ratios. These differences in SEDs are present at all considered luminosities (${M}_{\mathrm{UV}}\gt -15$, AB system), and are most pronounced for lower-luminosity galaxies. Intrinsic SEDs as well as those with interstellar medium absorption of galaxies with stripped stars and Population iii stars are found to be distinct for all tested Population iii IMFs.},
  author       = {Berzin, Elizabeth and Secunda, Amy and Cen, Renyue and Menegas, Alexander and Götberg, Ylva Louise Linsdotter},
  issn         = {1538-4357},
  journal      = {The Astrophysical Journal},
  keywords     = {Space and Planetary Science, Astronomy and Astrophysics},
  number       = {1},
  publisher    = {American Astronomical Society},
  title        = {{Spectral signatures of population III and envelope-stripped stars in galaxies at the epoch of reionization}},
  doi          = {10.3847/1538-4357/ac0af6},
  volume       = {918},
  year         = {2021},
}

@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{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{11514,
  abstract     = {We discuss the nature and physical properties of gas-mass selected galaxies in the ALMA spectroscopic survey (ASPECS) of the Hubble Ultra Deep Field (HUDF). We capitalize on the deep optical integral-field spectroscopy from the Multi Unit Spectroscopic Explorer (MUSE) HUDF Survey and multiwavelength data to uniquely associate all 16 line emitters, detected in the ALMA data without preselection, with rotational transitions of carbon monoxide (CO). We identify 10 as CO(2–1) at 1 < z < 2, 5 as CO(3–2) at 2 < z < 3, and 1 as CO(4–3) at z = 3.6. Using the MUSE data as a prior, we identify two additional CO(2–1) emitters, increasing the total sample size to 18. We infer metallicities consistent with (super-)solar for the CO-detected galaxies at z ≤ 1.5, motivating our choice of a Galactic conversion factor between CO luminosity and molecular gas mass for these galaxies. Using deep Chandra imaging of the HUDF, we determine an X-ray AGN fraction of 20% and 60% among the CO emitters at z ∼ 1.4 and z ∼ 2.6, respectively. Being a CO-flux-limited survey, ASPECS-LP detects molecular gas in galaxies on, above, and below the main sequence (MS) at z ∼ 1.4. For stellar masses ≥1010 (1010.5) ${M}_{\odot }$, we detect about 40% (50%) of all galaxies in the HUDF at 1 < z < 2 (2 < z < 3). The combination of ALMA and MUSE integral-field spectroscopy thus enables an unprecedented view of MS galaxies during the peak of galaxy formation.},
  author       = {Boogaard, Leindert A. and Decarli, Roberto and González-López, Jorge and van der Werf, Paul and Walter, Fabian and Bouwens, Rychard and Aravena, Manuel and Carilli, Chris and Bauer, Franz Erik and Brinchmann, Jarle and Contini, Thierry and Cox, Pierre and da Cunha, Elisabete and Daddi, Emanuele and Díaz-Santos, Tanio and Hodge, Jacqueline and Inami, Hanae and Ivison, Rob and Maseda, Michael and Matthee, Jorryt J and Oesch, Pascal and Popping, Gergö and Riechers, Dominik and Schaye, Joop and Schouws, Sander and Smail, Ian and Weiss, Axel and Wisotzki, Lutz and Bacon, Roland and Cortes, Paulo C. and Rix, Hans-Walter and Somerville, Rachel S. and Swinbank, Mark and Wagg, Jeff},
  issn         = {1538-4357},
  journal      = {The Astrophysical Journal},
  keywords     = {Space and Planetary Science, Astronomy and Astrophysics},
  number       = {2},
  publisher    = {IOP Publishing},
  title        = {{The ALMA spectroscopic survey in the HUDF: Nature and physical properties of gas-mass selected galaxies using MUSE spectroscopy}},
  doi          = {10.3847/1538-4357/ab3102},
  volume       = {882},
  year         = {2019},
}

@article{11515,
  abstract     = {We present new deep ALMA and Hubble Space Telescope (HST)/WFC3 observations of MASOSA and VR7, two luminous Lyα emitters (LAEs) at z = 6.5, for which the UV continuum levels differ by a factor of four. No IR dust continuum emission is detected in either, indicating little amounts of obscured star formation and/or high dust temperatures. MASOSA, with a UV luminosity M1500 = −20.9, compact size, and very high Lyα ${\mathrm{EW}}_{0}\approx 145\,\mathring{\rm A} $, is undetected in [C ii] to a limit of L[C ii] < 2.2 × 107 L⊙, implying a metallicity Z ≲ 0.07 Z⊙. Intriguingly, our HST data indicate a red UV slope β = −1.1 ± 0.7, at odds with the low dust content. VR7, which is a bright (M1500 = −22.4) galaxy with moderate color (β = −1.4 ± 0.3) and Lyα EW0 = 34 Å, is clearly detected in [C ii] emission (S/N = 15). VR7's rest-frame UV morphology can be described by two components separated by ≈1.5 kpc and is globally more compact than the [C ii] emission. The global [C ii]/UV ratio indicates Z ≈ 0.2 Z⊙, but there are large variations in the UV/[C ii] ratio on kiloparsec scales. We also identify diffuse, possibly outflowing, [C ii]-emitting gas at ≈100 km s−1 with respect to the peak. VR7 appears to be assembling its components at a slightly more evolved stage than other luminous LAEs, with outflows already shaping its direct environment at z ∼ 7. Our results further indicate that the global [C ii]−UV relation steepens at SFR < 30 M⊙ yr−1, naturally explaining why the [C ii]/UV ratio is anticorrelated with Lyα EW in many, but not all, observed LAEs.},
  author       = {Matthee, Jorryt J and Sobral, D. and Boogaard, L. A. and Röttgering, H. and Vallini, L. and Ferrara, A. and Paulino-Afonso, A. and Boone, F. and Schaerer, D. and Mobasher, B.},
  issn         = {1538-4357},
  journal      = {The Astrophysical Journal},
  keywords     = {Space and Planetary Science, Astronomy and Astrophysics},
  number       = {2},
  publisher    = {IOP Publishing},
  title        = {{Resolved UV and [C ii] structures of luminous galaxies within the epoch of reionization}},
  doi          = {10.3847/1538-4357/ab2f81},
  volume       = {881},
  year         = {2019},
}

@article{11516,
  abstract     = {The well-known quasar SDSS J095253.83+011421.9 (J0952+0114) at z = 3.02 has one of the most peculiar spectra discovered so far, showing the presence of narrow Lyα and broad metal emission lines. Although recent studies have suggested that a proximate damped Lyα absorption (PDLA) system causes this peculiar spectrum, the origin of the gas associated with the PDLA is unknown. Here we report the results of observations with the Multi Unit Spectroscopic Explorer (MUSE) that reveal a new giant (≈100 physical kpc) Lyα nebula. The detailed analysis of the Lyα velocity, velocity dispersion, and surface brightness profiles suggests that the J0952+0114 Lyα nebula shares similar properties with other QSO nebulae previously detected with MUSE, implying that the PDLA in J0952+0144 is covering only a small fraction of the solid angle of the QSO emission. We also detected bright and spectrally narrow C iv λ1550 and He ii λ1640 extended emission around J0952+0114 with velocity centroids similar to the peak of the extended and central narrow Lyα emission. The presence of a peculiarly bright, unresolved, and relatively broad He ii λ1640 emission in the central region at exactly the same PDLA redshift hints at the possibility that the PDLA originates in a clumpy outflow with a bulk velocity of about 500 km s−1. The smaller velocity dispersion of the large-scale Lyα emission suggests that the high-speed outflow is confined to the central region. Lastly, the derived spatially resolved He ii/Lyα and C iv/Lyα maps show a positive gradient with the distance to the QSO, hinting at a non-homogeneous distribution of the ionization parameter.},
  author       = {Marino, Raffaella Anna and Cantalupo, Sebastiano and Pezzulli, Gabriele and Lilly, Simon J. and Gallego, Sofia and Mackenzie, Ruari and Matthee, Jorryt J and Brinchmann, Jarle and Bouché, Nicolas and Feltre, Anna and Muzahid, Sowgat and Schroetter, Ilane and Johnson, Sean D. and Nanayakkara, Themiya},
  issn         = {1538-4357},
  journal      = {The Astrophysical Journal},
  keywords     = {Space and Planetary Science, Astronomy and Astrophysics},
  number       = {1},
  publisher    = {IOP Publishing},
  title        = {{A giant Lyα nebula and a small-scale clumpy outflow in the system of the exotic quasar J0952+0114 unveiled by MUSE}},
  doi          = {10.3847/1538-4357/ab2881},
  volume       = {880},
  year         = {2019},
}

@article{11517,
  abstract     = {To understand star formation in galaxies, we investigate the star formation rate (SFR) surface density (ΣSFR) profiles for galaxies, based on a well-defined sample of 976 star-forming MaNGA galaxies. We find that the typical ΣSFR profiles within 1.5Re of normal SF galaxies can be well described by an exponential function for different stellar mass intervals, while the sSFR profile shows positive gradients, especially for more massive SF galaxies. This is due to the more pronounced central cores or bulges rather than the onset of a `quenching' process. While galaxies that lie significantly above (or below) the star formation main sequence (SFMS) show overall an elevation (or suppression) of ΣSFR at all radii, this central elevation (or suppression) is more pronounced in more massive galaxies. The degree of central enhancement and suppression is quite symmetric, suggesting that both the elevation and suppression of star formation are following the same physical processes. Furthermore, we find that the dispersion in ΣSFR within and across the population is found to be tightly correlated with the inferred gas depletion time, whether based on the stellar surface mass density or the orbital dynamical time. This suggests that we are seeing the response of a simple gas-regulator system to variations in the accretion rate. This is explored using a heuristic model that can quantitatively explain the dependence of σ(ΣSFR) on gas depletion timescale. Variations in accretion rate are progressively more damped out in regions of low star-formation efficiency leading to a reduced amplitude of variations in star-formation.},
  author       = {Wang, Enci and Lilly, Simon J. and Pezzulli, Gabriele and Matthee, Jorryt J},
  issn         = {1538-4357},
  journal      = {The Astrophysical Journal},
  keywords     = {Space and Planetary Science, Astronomy and Astrophysics},
  number       = {2},
  publisher    = {IOP Publishing},
  title        = {{On the elevation and suppression of star formation within galaxies}},
  doi          = {10.3847/1538-4357/ab1c5b},
  volume       = {877},
  year         = {2019},
}