Clumpy star formation and an obscured nuclear starburst in the luminous dusty z=4 galaxy GN20 seen by MIRI/JWST

Abstract

Dusty star-forming galaxies emit most of their light at far-IR to mm wavelengths as their star formation is highly obscured. Far-IR and mm observations have revealed their dust, neutral and molecular gas properties. The sensitivity of JWST at rest-frame optical and near-infrared wavelengths now allows the study of the stellar and ionized gas content. We investigate the spatially resolved distribution and kinematics of the ionized gas in GN20, a dusty star forming galaxy at $z$=4.0548. We present deep MIRI/MRS integral field spectroscopy of the near-infrared rest-frame emission of GN20. We detect spatially resolved \paa, out to a radius of 6 kpc, distributed in a clumpy morphology. The star formation rate derived from \paa\ (144 $\pm$ 9 \msunperyear) is only 7.7 $\pm 0.5$\% of the infrared star formation rate (1860 $\pm$ 90 \msunperyear). We attribute this to very high extinction (A${}_V$ = 17.2 $\pm$ 0.4 mag, or A${}_{V,mixed}$ = 44 $\pm$ 3 mag), especially in the nucleus of GN20, where only faint \paa\ is detected, suggesting a deeply buried starburst. We identify four, spatially unresolved, clumps in the \paa\ emission. Based on the double peaked \paa\ profile we find that each clump consist of at least two sub-clumps. We find mass upper limits consistent with them being formed in a gravitationally unstable gaseous disk. The UV bright region of GN20 does not have any detected \paa\ emission, suggesting an age of more than 10 Myrs for this region of the galaxy. From the rotation profile of \paa\ we conclude that the gas kinematics are rotationally dominated and the $v_{rot}/{\sigma }_m=3.8\pm 1.4$ is similar to low-redshift LIRGs. We speculate that the clumps seen in GN20 could contribute to building up the inner disk and bulge of GN20.

13 pages, 7 figures, accepted for publication in A&A

References in corpus (51)

• Gaia Data Release 3: Summary of the content and survey properties
• Cold streams in early massive hot haloes as the main mode of galaxy formation
• A Highly Consistent Framework for the Evolution of the Star-Forming "Main Sequence" from z~0-6
• Formation of Massive Galaxies at High Redshift: Cold Streams, Clumpy Disks and Compact Spheroids
• From rings to bulges: evidence for rapid secular galaxy evolution at z~2 from integral field spectroscopy in the SINS survey
• New Determinations of the UV Luminosity Functions from z~9 to z~2 show a remarkable consistency with halo growth and a constant star formation efficiency
• Bulge Formation by the Coalescence of Giant Clumps in Primordial Disk Galaxies
• Kiloparsec-scale dust disks in high-redshift luminous submillimeter galaxies
• JWST MIRI flight performance: The Medium-Resolution Spectrometer
• Ionized gas outflows and global kinematics of low-z luminous star forming galaxies
• Clumpy Galaxies in GOODS and GEMS: Massive Analogs of Local Dwarf Irregulars
• Near-Infrared and Star-forming properties of Local Luminous Infrared Galaxies
• The Evolution of the IR Luminosity Function and Dust-obscured Star Formation in the Last 13 Billion Years
• Life beyond 30: probing the -20<M_UV<-17 luminosity function at 8<z<13 with the NIRCam parallel field of the MIRI Deep Survey
• The kiloparsec-scale star formation law at redshift 4: wide-spread, highly efficient star formation in the dust-obscured starburst galaxy GN20
• Dynamical properties of z $\sim 4.5$ dusty star-forming galaxies and their connection with local early type galaxies
• A 3D Drizzle Algorithm for JWST and Practical Application to the MIRI Medium Resolution Spectrometer
• Dusty Starbursts Masquerading as Ultra-high Redshift Galaxies in JWST CEERS Observations
• CEERS Key Paper V: A triality on the nature of HST-dark galaxies
• Cold Molecular Gas in Merger Remnants: I. Formation of Molecular Gas Disks
• The nature of giant clumps in distant galaxies probed by the anatomy of the Cosmic Snake
• z~2-9 Galaxies Magnified by the Hubble Frontier Field Clusters II: Luminosity Functions and Constraints on a Faint-End Turnover
• Unveiling the Nature of Infrared Bright, Optically Dark Galaxies with Early JWST Data
• The ALMA REBELS Survey: The Dust-obscured Cosmic Star Formation Rate Density at Redshift 7
• EPOCHS VI: The Size and Shape Evolution of Galaxies since z ~ 8 with JWST Observations
• Star cluster formation in the most extreme environments: Insights from the HiPEEC survey
• COLDz: A High Space Density of Massive Dusty Starburst Galaxies ~1 Billion Years after the Big Bang
• Exploring the physical properties of lensed star-forming clumps at $2\lesssim z\lesssim 6$
• Spatial variations in aromatic hydrocarbon emission in a dust-rich galaxy
• Larson's scaling laws, and the gravitational instability of clumpy discs at high redshift
• Expectations of the size evolution of massive galaxies at $3\le z\le 6$ from the TNG50 simulation: the CEERS/JWST view
• JWST MIRI/MRS in-flight absolute flux calibration and tailored fringe correction for unresolved sources
• A blue depression in the optical spectra of M dwarfs
• JWST MIRI flight performance: Detector Effects and Data Reduction Algorithms
• 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
• Kinematic classifications of local interacting galaxies: implications for the merger/disk classifications at high-z
• Star-forming Clumps in Local Luminous Infrared Galaxies
• The ALMA REBELS Survey: The First Infrared Luminosity Function Measurement at $\mathbf{z \sim 7}
• GA-NIFS: Early-stage feedback in a heavily obscured AGN at $z=4.76$
• Sub-Millimetre Galaxies with Webb: Near-Infrared Counterparts and Multi-wavelength Morphology
• JWST CEERS probes the role of stellar mass and morphology in obscuring galaxies
• Spatially-resolved H$\alpha$ and ionizing photon production efficiency in the lensed galaxy MACS1149-JD1 at a redshift of 9.11
• Uncovering the stellar structure of the dusty star-forming galaxy GN20 at z=4.055 with MIRI/JWST
• Chaotic and Clumpy Galaxy Formation in an Extremely Massive Reionization-Era Halo
• Multiply lensed star forming clumps in the A521-sys1 galaxy at redshift 1
• Compact molecular gas emission in local LIRGs among low- and high-z galaxies
• Duality in spatially resolved star-formation relations in local LIRGs
• High Resolution HST Imaging Survey of Local Star-Forming Galaxies I: Spatially-Resolved Obscured Star Formation with H$\alpha$ and Paschen-$\beta$ Recombination Lines
• GOALS-JWST: NIRCam and MIRI Imaging of the Circumnuclear Starburst Ring in NGC 7469
• Spatially resolved gas and stellar kinematics in compact starburst galaxies

Cited by in corpus (4)

• GA-NIFS: The core of an extremely massive proto-cluster at the Epoch of Reionization probed with JWST/NIRSpec
• The NIRSpec Wide GTO Survey
• JWST/MIRI unveils the stellar component of the GN20 dusty galaxy overdensity at $z$=4.05
• Physical Processes Behind the Co-Evolution of Halos, Galaxies and Supermassive Black Holes in the IllustrisTNG Simulation