Uncovering the stellar structure of the dusty star-forming galaxy GN20 at z=4.055 with MIRI/JWST

Abstract

Luminous infrared galaxies at high redshifts ($z$>4) include extreme starbursts that build their stellar mass over short periods of time (>100 Myr). These galaxies are considered to be the progenitors of massive quiescent galaxies at intermediate redshifts ($z\sim$2) but their stellar structure and buildup is unknown. Here, we present the first spatially resolved near-infrared imaging of GN20, one of the most luminous dusty star-forming galaxies known to date, observed at an epoch when the Universe was only 1.5 Gyr old. The 5.6$\mu$m image taken with the JWST Mid-Infrared Instrument (MIRI/JWST) shows that GN20 is a very luminous galaxy (M${}_{1.1\mu \mathrm{m},\mathrm{AB}}$=$-$25.01), with a stellar structure composed of a conspicuous central source and an extended envelope. The central source is an unresolved nucleus that carries 9% of the total flux. The nucleus is co-aligned with the peak of the cold dust emission, and offset by 3.9 kpc from the ultraviolet stellar emission. The diffuse stellar envelope is similar in size to the clumpy CO molecular gas distribution. The centroid of the stellar envelope is offset by 1 kpc from the unresolved nucleus, suggesting GN20 is involved in an interaction or merger event supported by its location as the brightest galaxy in a proto-cluster. The stellar size of GN20 is larger by a factor of about 3-5 than known spheroids, disks, and irregulars at $z\sim$4, while its size and low Sérsic index are similar to those measured in dusty, infrared luminous galaxies at $z\sim$2 of the same mass. GN20 has all the ingredients necessary for evolving into a massive spheroidal quiescent galaxy at intermediate $z$: it is a large, luminous galaxy at $z$=4.05 involved in a short and massive starburst centred in the stellar nucleus and extended over the entire galaxy, out to radii of 4 kpc, and likely induced by the interaction or merger with a member of the proto-cluster.

7 pages, 4 figures

References in corpus (15)

• Gaia Data Release 3: Summary of the content and survey properties
• 3D-HST+CANDELS: The Evolution of the Galaxy Size-Mass Distribution since $z=3$
• The Science Performance of JWST as Characterized in Commissioning
• Kiloparsec-scale dust disks in high-redshift luminous submillimeter galaxies
• The ALPINE-ALMA [CII] Survey: The nature, luminosity function and star formation history of dusty galaxies up to z~6
• The Evolution of the IR Luminosity Function and Dust-obscured Star Formation in the Last 13 Billion Years
• The kiloparsec-scale star formation law at redshift 4: wide-spread, highly efficient star formation in the dust-obscured starburst galaxy GN20
• CEERS Key Paper III: The Diversity of Galaxy Structure and Morphology at z=3-9 with JWST
• z~2-9 Galaxies Magnified by the Hubble Frontier Field Clusters II: Luminosity Functions and Constraints on a Faint-End Turnover
• The ALMA REBELS Survey: The Dust-obscured Cosmic Star Formation Rate Density at Redshift 7
• Far-infrared surveys of galaxy evolution
• Expectations of the size evolution of massive galaxies at $3\le z\le 6$ from the TNG50 simulation: the CEERS/JWST view
• ALMA 200 pc imaging of a z~7 quasar reveals a compact, disk-like host galaxy
• Observation of S4716 -- a Star with a 4 yr Orbit around Sgr A*
• MIRI/JWST observations reveal an extremely obscured starburst in the z=6.9 system SPT0311-58

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• JWST/CEERS sheds light on dusty star-forming galaxies: forming bulges, lopsidedness and outside-in quenching at cosmic noon
• MIRI Deep Imaging Survey (MIDIS) of the Hubble Ultra Deep Field
• JWST's PEARLS: resolved study of the stellar and dust components in starburst galaxies at cosmic noon
• Dynamical modelling and origin of gas turbulence in z $\sim$ 4.5 galaxies
• Clumpy star formation and an obscured nuclear starburst in the luminous dusty z=4 galaxy GN20 seen by MIRI/JWST
• JWST/MIRI unveils the stellar component of the GN20 dusty galaxy overdensity at $z$=4.05
• New JWST redshifts for the host galaxies of CDF-S XT1 and XT2: understanding their nature
• The [NII] 205 $\mu$m line emission from high-z SMGs and QSOs
• JWST reveals extended stellar disks for ALMA-bright dusty star-forming galaxies in the Spiderweb protocluster
• Formation of Substructure in Luminous Submillimeter Galaxies (FOSSILS): Evidence of Multiple Pathways to Trigger Starbursts in Luminous Submillimeter Galaxies