New Insights into the Evolution of Massive Stars and Their Effects on Our Understanding of Early Galaxies

Eldridge, J. J.; Stanway, Elizabeth R.

doi:10.1146/annurev-astro-052920-100646

“…The slope of the upper IMF affects the UV-optical color and mass-to-light ratio for a given star formation history. The evolution of high-mass stars at low metallicity is important to the UV and ionizing continuum of galaxies, but is not well constrained from observations in the local universe (Eldridge & Stanway 2022). Binary stellar evolution and stellar rotation may increase the lifetimes of massive UV bright stars, leading to lower mass-tolight ratios for a given star formation history (e.g., Choi et al 2017).…”

Section: Methodsmentioning

confidence: 99%

JADES Imaging of GN-z11: Revealing the Morphology and Environment of a Luminous Galaxy 430 Myr after the Big Bang

Tacchella

¹

,

Eisenstein

²

,

Hainline

³

et al. 2023

ApJ

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We present JWST NIRCam nine-band near-infrared imaging of the luminous z = 10.6 galaxy GN-z11 from the JWST Advanced Deep Extragalactic Survey of the GOODS-N field. We find a spectral energy distribution (SED) entirely consistent with the expected form of a high-redshift galaxy: a clear blue continuum from 1.5 to 4 μm with a complete dropout in F115W. The core of GN-z11 is extremely compact in JWST imaging. We analyze the image with a two-component model, using a point source and a Sérsic profile that fits to a half-light radius of 200 pc and an index n = 0.9. We find a low-surface-brightness haze about 0.″4 to the northeast of the galaxy, which is most likely a foreground object but might be a more extended component of GN-z11. At a spectroscopic redshift of 10.60 (Bunker et al. 2023), the comparison of the NIRCam F410M and F444W images spans the Balmer jump. From population-synthesis modeling, here assuming no light from an active galactic nucleus, we reproduce the SED of GN-z11, finding a stellar mass of ∼109 M ⊙, a star formation rate of ∼20 M ⊙ yr−1, and a young stellar age of ∼20 Myr. Since massive galaxies at high redshift are likely to be highly clustered, we search for faint neighbors of GN-z11, finding nine galaxies out to ∼5 comoving Mpc transverse with photometric redshifts consistent with z = 10.6, and a tenth more tentative dropout only 3″ away. This is consistent with GN-z11 being hosted by a massive dark-matter halo (≈8 × 1010 M ⊙), though lower halo masses cannot be ruled out.

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“…BHeB stars provide important constraints on stellar evolution and serve as excellent tracers of recent star formation (Langer & Maeder 1995;Dohm-Palmer et al 2002;Dolphin et al 2003;Larsen et al 2011;Leščinskaitė et al 2022). In particular, the extent of the blue loop and the ratio of blue to red core helium burning stars are sensitive to several poorly constrained aspects of massive stars physics (e.g., rotation, convective overshoot; Alongi et al 1991;Ritossa 1996;McQuinn et al 2011;Jie et al 2015;Georgy et al 2021;Eldridge & Stanway 2022;Farrell et al 2022). The luminosities and spatial positions of BHeBs in nearby galaxies have been used to construct spatially resolved maps of star formation over the past few hundred megayears (Dohm- Palmer et al 2002;McQuinn et al 2012;Leščinskaitė et al 2022).…”

Section: Purity Of the Blue Core Helium Burning Sequencementioning

confidence: 99%

“…Metal-poor (Z  10% Z e ) massive stars (M  8 M e ) are central to a wide variety of astrophysics. In low-mass galaxies, their feedback (i.e., stellar winds, supernovae) regulates star formation, enriches the interstellar medium, and may drive the formation of dark matter cores (e.g., Mac Low & Ferrara 1999;Stinson et al 2007;Governato et al 2010;El-Badry et al 2016;Emerick et al 2018;Eldridge & Stanway 2022). At low metallicity, those processes are expected to change significantly in comparison to higher-metallicity environments (e.g., decreased line-driven winds, properties of supernovae; Heger et al 2003;Eldridge & Tout 2004;Young et al 2008;Smartt 2009;Vink & Sander 2021) due to changes in stellar properties (e.g., rotation, opacity, internal mixing; Maeder et al 2005;Meynet et al 2008Meynet et al , 2017Sanyal et al 2017;Groh et al 2019).…”

Section: Introductionmentioning

confidence: 99%

A Panchromatic Study of Massive Stars in the Extremely Metal-poor Local Group Dwarf Galaxy Leo A*

Gull

¹

,

Weisz

²

,

Senchyna

³

et al. 2022

ApJ

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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 log ( T eff ) and 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.

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“…Possible systematic uncertainty from different assumed SFH is shown in a dotted line. Binary stars are important to include in SED modeling as in BPASS, especially for such blue galaxies (Eldridge 2020;Eldridge & Stanway 2022). Binary interactions produce more Wolf-Rayet/helium stars at later ages, generating more energetic photons.…”

Section: Components a And B: Ages Dust And Massmentioning

confidence: 99%

JWST Reveals a Possible z ∼ 11 Galaxy Merger in Triply Lensed MACS0647–JD

Hsiao¹,

Coe

²

,

Abdurrouf

³

et al. 2023

ApJL

Self Cite

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MACS0647–JD is a triply lensed z ∼ 11 galaxy originally discovered with the Hubble Space Telescope. The three lensed images are magnified by factors of ∼8, 5, and 2 to AB mag 25.1, 25.6, and 26.6 at 3.5 μm. The brightest is over a magnitude brighter than other galaxies recently discovered at similar redshifts z > 10 with JWST. Here, we report new JWST imaging that clearly resolves MACS0647–JD as having two components that are either merging galaxies or stellar complexes within a single galaxy. The brighter larger component “A” is intrinsically very blue (β ∼ −2.6 ± 0.1), likely due to very recent star formation and no dust, and is spatially extended with an effective radius ∼70 ± 24 pc. The smaller component “B” (r ∼ 20 − 5 + 8 pc) appears redder (β ∼ −2 ± 0.2), likely because it is older (100–200 Myr) with mild dust extinction (A V ∼ 0.1 mag). With an estimated stellar mass ratio of roughly 2:1 and physical projected separation ∼400 pc, we may be witnessing a galaxy merger 430 million years after the Big Bang. We identify galaxies with similar colors in a high-redshift simulation, finding their star formation histories to be dissimilar, which is also suggested by the spectral energy distribution fitting, suggesting they formed further apart. We also identify a candidate companion galaxy “C” ∼3 kpc away, likely destined to merge with A and B. Upcoming JWST Near Infrared Spectrograph observations planned for 2023 January will deliver spectroscopic redshifts and more physical properties for these tiny magnified distant galaxies observed in the early universe.

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New Insights into the Evolution of Massive Stars and Their Effects on Our Understanding of Early Galaxies

Cited by 37 publications

References 223 publications

JADES Imaging of GN-z11: Revealing the Morphology and Environment of a Luminous Galaxy 430 Myr after the Big Bang

JADES Imaging of GN-z11: Revealing the Morphology and Environment of a Luminous Galaxy 430 Myr after the Big Bang

A Panchromatic Study of Massive Stars in the Extremely Metal-poor Local Group Dwarf Galaxy Leo A*

JWST Reveals a Possible z ∼ 11 Galaxy Merger in Triply Lensed MACS0647–JD

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