Implications of a Temperature-dependent Initial Mass Function. II. An Updated View of the Star-forming Main Sequence

Steinhardt, Charles L.; Sneppen, Albert; Mostafa, Basel; Hensley, Hagan; Jermyn, Adam S.; Lopez, Adrian; Weaver, John R.; Brammer, Gabriel; Clark, Thomas H.; Davidzon, I.; Diaconu, Andrei C.; Mobasher, Bahram; Rusakov, Vadim; Toft, Sune

doi:10.3847/1538-4357/ac62d6

“…Fortunately, for our redshift range of interest, from the perspective of continuum fitting for the stellar population analyses, extreme nebular emission from strong rest-frame optical lines is shifted out of all NIRCam bands and the most important feature for the photo-zs in the bright galaxies we study is the Lyman break. Further, there exists a range of plausible, but hitherto unconstrained physical ingredients that are unaccounted for in our models (e.g., primordial AGN, top-heavy IMFs, superluminous Population III stars; Windhorst et al 2018;Pacucci et al 2022;Steinhardt et al 2022). Some of these ingredients may potentially produce large UV luminosities in the absence of substantial stellar mass.…”

Section: Caveatsmentioning

confidence: 99%

Two Remarkably Luminous Galaxy Candidates at z ≈ 10–12 Revealed by JWST

Naidu

¹

,

Oesch

²

,

Dokkum

³

et al. 2022

ApJL

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The first few 100 Myr at z > 10 mark the last major uncharted epoch in the history of the universe, where only a single galaxy (GN-z11 at z ≈ 11) is currently spectroscopically confirmed. Here we present a search for luminous z > 10 galaxies with JWST/NIRCam photometry spanning ≈1–5 μm and covering 49 arcmin2 from the public JWST Early Release Science programs (CEERS and GLASS). Our most secure candidates are two M UV ≈ −21 systems: GLASS-z12 and GLASS-z10. These galaxies display abrupt ≳1.8 mag breaks in their spectral energy distributions (SEDs), consistent with complete absorption of flux bluewards of Lyα that is redshifted to z = 12.4 − 0.3 + 0.1 and z = 10.4 − 0.5 + 0.4 . Lower redshift interlopers such as quiescent galaxies with strong Balmer breaks would be comfortably detected at >5σ in multiple bands where instead we find no flux. From SED modeling we infer that these galaxies have already built up ∼109 solar masses in stars over the ≲300–400 Myr after the Big Bang. The brightness of these sources enable morphological constraints. Tantalizingly, GLASS-z10 shows a clearly extended exponential light profile, potentially consistent with a disk galaxy of r 50 ≈ 0.7 kpc. These sources, if confirmed, join GN-z11 in defying number density forecasts for luminous galaxies based on Schechter UV luminosity functions, which require a survey area >10× larger than we have studied here to find such luminous sources at such high redshifts. They extend evidence from lower redshifts for little or no evolution in the bright end of the UV luminosity function into the cosmic dawn epoch, with implications for just how early these galaxies began forming. This, in turn, suggests that future deep JWST observations may identify relatively bright galaxies to much earlier epochs than might have been anticipated.

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“…Dust temperatures in starforming galaxies are typically above 20 K, with higher dust temperatures found both toward high redshift and toward higher SFRs at fixed stellar mass and redshift (Magnelli et al 2014;Schreiber et al 2018;Kokorev et al 2021). Although luminosity-averaged dust temperatures are not guaranteed to be reliable indicators of gas temperatures in star-forming regions, the gas temperatures inferred from the methods used in this work lie in a similar range and have similar redshift dependence and SFR dependence (cf., Steinhardt et al 2022 for an extended discussion), although they are measured in entirely different ways. Jermyn et al (2018) developed a theoretical prescription for a one-parameter family of IMFs at some gas temperature T IMF .…”

Section: Introductionmentioning

confidence: 99%

“…Thus, nearly every galaxy is best described with an IMF which is bottom-lighter (or top-heavier) than our own. Paper II (Steinhardt et al 2022) explores the implications of these results for star formation and the star-forming "main sequence." This work describes the effects on SMFs and high-redshift cosmology.…”

Section: Introductionmentioning

confidence: 99%

Implications of a Temperature-dependent Initial Mass Function. III. Mass Growth and Quiescence

Steinhardt

¹

,

Sneppen

²

,

Hensley

³

et al. 2022

ApJ

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The stellar initial mass function (IMF) is predicted to depend upon the temperature of gas in star-forming molecular clouds. The introduction of an additional parameter, T IMF, into photometric template fitting suggests most galaxies obey an IMF top heavier than the Galactic IMF. The implications of the revised fit on mass function, quiescence, and turnoff are discussed. At all redshifts, the highest-mass galaxies become quiescent first with the turnoff mass decreasing toward the present. The synchronous turnoff mass across galaxies suggests quiescence is driven by universal mechanisms rather than by stochastic or environmental processes.

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“…Notably, a comparison between T SF and dust temperatures shows strong agreement (Fig. 1) in not only the broad qualitative trends but even quantitatively (Steinhardt et al 2022c). Thus, T SF proves a reasonable proxy for (cool) dust temperature, and if gas and dust are approximately in equilibrium, T SF should then indicate gas temperature in star-forming regions.…”

Section: Measuring Gas Temperatures From Photometric Surveysmentioning

confidence: 54%

The Earliest Stage of Galactic Star Formation

Steinhardt¹,

Rusakov²,

Clark³

et al. 2023

Preprint

1

0

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Using a recently-developed technique to estimate gas temperatures (T SF ) in star-forming regions from large photometric surveys, we propose a diagram, analogous to the Hertzsprung-Russell diagram for individual stars, to probe the evolution of individual galaxies. On this T SF -sSFR (specific star formation rate) diagram, a small fraction of star-forming galaxies appear to be dominated by different feedback mechanisms than typical star-forming galaxies. These galaxies generically have younger stellar populations, lower stellar masses and increase in relative abundance towards higher redshifts, so we argue that these objects are in an earlier stage of galactic star formation. Further, Hubble observations find that these "core-forming" galaxies also exhibit distinct morphology, and that tracks on the T SF -sSFR diagram are also a morphological sequence. Thus, unlike starburst phases which can be triggered environmentally, these earliest, core-forming galaxies, appear to be a stage that typical galaxies go through early in their star formation history. We therefore argue that most galaxies first go through a core formation stage, then subsequently disk formation, and finally become quiescent.

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Implications of a Temperature-dependent Initial Mass Function. II. An Updated View of the Star-forming Main Sequence

Cited by 16 publications

References 51 publications

Two Remarkably Luminous Galaxy Candidates at z ≈ 10–12 Revealed by JWST

Two Remarkably Luminous Galaxy Candidates at z ≈ 10–12 Revealed by JWST

Implications of a Temperature-dependent Initial Mass Function. III. Mass Growth and Quiescence

The Earliest Stage of Galactic Star Formation

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