RELICS: Small-scale Star Formation in Lensed Galaxies at z = 6–10

Welch, Brian; Coe, Dan; Zitrin, Adi; Diego, J. M.; Windhorst, Rogier A.; Mandelker, Nir; Vanzella, E.; Ravindranath, Swara; Zackrisson, Erik; Florian, Michael; Bradley, Larry; Sharon, Keren; Bradač, Maruša; Rigby, J. Keith; Frye, Brenda; Fujimoto, Seiji

doi:10.3847/1538-4357/aca8a8

Cited by 15 publications

(19 citation statements)

References 97 publications

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“…Appendix A presents the spectral energy distribution (SED) fitting of the host multiband photometry (see Section 4.1), which results in a redshift probability distribution narrowly peaked at z = 6.0 ± 0.2 (95% CL), with no significant likelihood at other redshifts. This is fully consistent with previous estimates based on HST imaging (Salmon et al 2020;Welch et al 2023). In the following, we adopt the fiducial value of z = 6.0 as the current best solution for the Sunrise arc (upcoming NIRSpec spectroscopy will provide definitive estimates).…”

Section: 1supporting

confidence: 93%

“…The presence of barely resolved and unresolved sources despite the very large magnification implies that their intrinsic sizes are very small (as observed in other systems; e.g., Johnson et al 2017;Rigby et al 2017;Vanzella et al 2019;Bouwens et al 2021). Small effective radii of the sources were already estimated based on HST imaging with upper limits as small as 3 pc for unresolved sources (Welch et al 2023). The unmatched angular resolution (<80 mas at λ < 2 μm) and unique wavelength coverage (up to 5 μm) provided by JWST/NIRCam allow us to spatially resolve all of the previously identified clumps and measure radii as small as ∼1 pc.…”

Section: 1mentioning

confidence: 87%

“…In this work, we report on JWST/NIRCam observations of the Sunrise arc, the most highly magnified galaxy known at z ∼ 6 (Salmon et al 2020;Welch et al 2023) and host to the lensed star Earendel (Welch et al 2022a(Welch et al , 2022b. Welch et al (2023) analyzed the star-forming regions of the galaxy based on HST imaging. Here we use JWST to further characterize the same regions which-despite the very large lensing amplification-appear rather nucleated and/or barely resolved, making them some of the best candidates for GCPs.…”

Section: Introductionmentioning

confidence: 99%

“…Pioneering works in the pre-James Webb Space Telescope (JWST) era have already reported on the detection of tiny starforming regions at cosmological distances by combining Hubble Space Telescope (HST) imaging and gravitational lensing (e.g., Ellis et al 2001) that have only recently been recognized as globular cluster precursor (GCP) candidates (Vanzella et al 2017(Vanzella et al , 2019; see also Elmegreen et al 2021;Welch et al 2023), along with the use of deep Very Large Telescope (VLT) Multi Unit Spectroscopic Explorer (MUSE) spectroscopy performed on the Hubble Frontier Fields (e.g., Vanzella et al 2021) or exploiting superlensed arcs like the Sunburst (Rigby et al 2017;Rivera-Thorsen et al 2019;Sharon et al 2022;Vanzella et al 2022a).…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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JWST/NIRCam Probes Young Star Clusters in the Reionization Era Sunrise Arc

Vanzella¹,

Claeyssens

Welch

et al. 2023

ApJ

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Star cluster formation in the early universe and its contribution to reionization remains largely unconstrained to date. Here we present JWST/NIRCam imaging of the most highly magnified galaxy known at z ∼ 6, the Sunrise arc. We identify six young massive star clusters (YMCs) with measured radii spanning from ∼20 down to ∼1 pc (corrected for lensing magnification), estimated stellar masses of ∼106–7 M ⊙, and ages of 1–30 Myr based on SED fitting to photometry measured in eight filters extending to rest frame 7000 Å. The resulting stellar mass surface densities are higher than 1000 M ⊙ pc−2 (up to a few 105 M ⊙ pc−2), and their inferred dynamical ages qualify the majority of these systems as gravitationally bound stellar clusters. The star cluster ages map the progression of star formation along the arc, with two evolved systems (≳10 Myr old) followed by very young clusters. The youngest stellar clusters (<5 Myr) show evidence of prominent Hβ+[O iii] emission based on photometry with equivalent widths larger than >1000 Å rest frame and are hosted in a 200 pc sized star-forming complex. Such a region dominates the ionizing photon production with a high efficiency log ( ξ ion [ Hz erg − 1 ] ) ∼ 25.7 . A significant fraction of the recently formed stellar mass of the galaxy (10%–30%) occurred in these YMCs. We speculate that such sources of ionizing radiation boost the ionizing photon production efficiency, which eventually carves ionized channels that might favor the escape of Lyman continuum radiation. The survival of some of the clusters would make them the progenitors of massive and relatively metal-poor globular clusters in the local universe.

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Section: 1supporting

confidence: 93%

Section: 1mentioning

confidence: 87%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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JWST/NIRCam Probes Young Star Clusters in the Reionization Era Sunrise Arc

Vanzella¹,

Claeyssens

Welch

et al. 2023

ApJ

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Bound star clusters observed in a lensed galaxy 460 Myr after the Big Bang

Adamo,

Bradley,

Vanzella

et al. 2024

Nature

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The Cosmic Gems arc is among the brightest and highly magnified galaxies observed at redshift z ≈ 10.2 (ref. 1). However, it is an intrinsically ultraviolet faint galaxy, in the range of those now thought to drive the reionization of the Universe2–4. Hitherto the smallest features resolved in a galaxy at a comparable redshift are between a few hundreds and a few tens of parsecs (pc)5,6. Here we report JWST observations of the Cosmic Gems. The light of the galaxy is resolved into five star clusters located in a region smaller than 70 pc. They exhibit minimal dust attenuation and low metallicity, ages younger than 50 Myr and intrinsic masses of about 106M⊙. Their lensing-corrected sizes are approximately 1 pc, resulting in stellar surface densities near 105M⊙ pc−2, three orders of magnitude higher than typical young star clusters in the local Universe7. Despite the uncertainties inherent to the lensing model, they are consistent with being gravitationally bound stellar systems, that is, proto-globular clusters. We conclude that star cluster formation and feedback likely contributed to shaping the properties of galaxies during the epoch of reionization.

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[C ii] 158 μm emission as an indicator of galaxy star formation rate

Liang,

Feldmann,

Murray

et al. 2023

Monthly Notices of the Royal Astronomical Society

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Observations of local star-forming galaxies (SFGs) show a tight correlation between their singly ionized carbon line luminosity ($L_{\rm [C\, \small {II}]}$) and star formation rate (SFR), suggesting that $L_{\rm [C\, \small {II}]}$ may be a useful SFR tracer for galaxies. Some other galaxy populations, however, are found to have lower $L_{\rm [C\, \small {II}]}{}/{}\rm SFR$ than local SFGs, including the infrared-luminous, starburst galaxies at low and high redshifts as well as some moderately star-forming galaxies at the epoch of re-ionization (EoR). The origins of this ‘$\rm [C\, \small {II}]$ deficit’ is unclear. In this work, we study the $L_{\rm [C\, \small {II}]}$-SFR relation of galaxies using a sample of z = 0 − 8 galaxies with M* ≈ 107 − 5 × 1011 M⊙ extracted from cosmological volume and zoom-in simulations from the Feedback in Realistic Environments (fire) project. We find a simple analytic expression for $L_{\rm [C\, \small {II}]}$/SFR of galaxies in terms of the following parameters: mass fraction of $\rm [C\, \small {II}]$-emitting gas ($f_{\rm [C\, \small {II}]}$), gas metallicity (Zgas), gas density (ngas) and gas depletion time ($t_{\rm dep}{}={}M_{\rm gas}{}/{}\rm SFR$). We find two distinct physical regimes: $\rm H_2$-rich galaxies where tdep is the main driver of the $\rm [C\, \small {II}]$ deficit and $\rm H_2$-poor galaxies where Zgas is the main driver. The observed $\rm [C\, \small {II}]$ deficit of IR-luminous galaxies and early EoR galaxies, corresponding to the two different regimes, is due to short gas depletion time and low gas metallicity, respectively. Our result indicates that the $\rm [C\, \small {II}]$ deficit is a common phenomenon of galaxies, and caution needs to be taken when applying a constant $L_{\rm [C\, \small {II}]}$-to-SFR conversion factor derived from local SFGs to estimate cosmic SFR density at high redshifts and interpret data from upcoming $\rm [C\, \small {II}]$ line intensity mapping experiments.

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RELICS: Small-scale Star Formation in Lensed Galaxies at z = 6–10

Cited by 15 publications

References 97 publications

JWST/NIRCam Probes Young Star Clusters in the Reionization Era Sunrise Arc

JWST/NIRCam Probes Young Star Clusters in the Reionization Era Sunrise Arc

Bound star clusters observed in a lensed galaxy 460 Myr after the Big Bang

[C ii] 158 μm emission as an indicator of galaxy star formation rate

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