JWST/NIRCam Observations of Stars and HII Regions in $z\simeq 6-8$ Galaxies: Properties of Star Forming Complexes on 150 pc Scales

Abstract

The onset of the {\it JWST}-era provides a much-improved opportunity to characterize the resolved structure of early star forming systems. Previous {\it Spitzer} observations of $z\gtrsim 6$ galaxies revealed the presence of old stars and luminous HII regions (via [OIII]+H$\beta$ emission), but the poor resolution stunted our ability to map their locations with respect to the star forming regions identified in the rest-UV. In this paper, we investigate the internal structure of 12 of the most luminous $z\simeq 6-8$ galaxies in the EGS field observed with recent {\it JWST}/NIRCam imaging. The systems appear clumpy in the rest-UV, with more than half of the light coming from $\simeq 10^7$ to 10${}^9$ M${}_{\odot }$ star forming complexes that are $\simeq 150$ - 480 pc in size. The clumps tend to be dominated by young stars (median = 36 Myr), but we also find large variations in clump ages within individual galaxies. The [OIII]+H$\beta$ EW varies significantly across individual galaxies (reflecting differences in stellar and gas properties), but the HII regions largely track the UV-bright complexes. Perhaps surprisingly, the rest-optical continuum is just as clumpy as the UV, and we do not find older (and redder) nuclear stellar components that were previously undetected or faint in the UV. The majority of the stellar mass in bright $6<z<8$ galaxies appears to be contained in the $\gtrsim 150$ pc-scale clumpy star forming complexes, reflecting the very active phase of assembly that is common in reionization-era galaxies.

arXiv commentmain text 12 pages, 7 figures; accepted for publication by MNRAS

References in corpus (68)

• Stellar population synthesis at the resolution of 2003
• Galactic Stellar and Substellar Initial Mass Function
• PARSEC: stellar tracks and isochrones with the PAdova and TRieste Stellar Evolution Code
• CANDELS: The Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey
• CANDELS: The Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey - The Hubble Space Telescope Observations, Imaging Data Products and Mosaics
• UV Luminosity Functions at redshifts z~4 to z~10: 10000 Galaxies from HST Legacy Fields
• The Evolution of the Galaxy Rest-Frame Ultraviolet Luminosity Function Over the First Two Billion Years
• Stellar Population Inference with Prospector
• Formation and Dynamical Evolution of Multiple Stellar Generations in Globular Clusters
• PARSEC evolutionary tracks of massive stars up to $350M_{\odot }$ at metallicities 0.0001$\le Z\le$0.04
• The All-wavelength Extended Groth Strip International Survey (AEGIS) Data Sets
• Wet Disc Contraction to Galactic Blue Nuggets and Quenching to Red Nuggets
• The Evolution of Galaxy Structure over Cosmic Time
• An updated analytic model for the attenuation by the intergalactic medium
• Modelling and interpreting spectral energy distributions of galaxies with BEAGLE
• Smooth(er) Stellar Mass Maps in CANDELS: Constraints on the Longevity of Clumps in High-redshift Star-forming Galaxies
• Lyman-alpha and CIII] Emission in z=7-9 Galaxies: Accelerated Reionization Around Luminous Star Forming Systems?
• Modelling the nebular emission from primeval to present-day star-forming galaxies
• Evidence for PopIII-like stellar populations in the most luminous Lyman-$\alpha$ emitters at the epoch of re-ionisation: spectroscopic confirmation
• Imfit: A Fast, Flexible New Program for Astronomical Image Fitting
• Galaxy growth in a massive halo in the first billion years of cosmic history
• Clumpy Galaxies in CANDELS. I. The Definition of UV Clumps and the Fraction of Clumpy Galaxies at 0.5<z<3
• The z = 9-10 galaxy population in the Hubble Frontier Fields and CLASH surveys: The z=9 LF and further evidence for a smooth decline in UV luminosity at z >= 8
• Galaxy Formation and Reionization: Key Unknowns and Expected Breakthroughs by the James Webb Space Telescope
• Z > 7 galaxies with red Spitzer/IRAC [3.6]-[4.5] colors in the full CANDELS data set: the brightest-known galaxies at Z ~ 7-9 and a probable spectroscopic confirmation at Z=7.48
• Rotation in [CII]-emitting gas in two galaxies at a redshift of 6.8
• On the Stellar Populations of Galaxies at z=9-11: The Growth of Metals and Stellar Mass at Early Times
• Reionization Era Bright Emission Line Survey: Selection and Characterization of Luminous Interstellar Medium Reservoirs in the z>6.5 Universe
• An Intensely Star-Forming Galaxy at z~7 with Low Dust and Metal Content Revealed by Deep ALMA and HST Observations
• Paving the way for the JWST: witnessing globular cluster formation at z>3
• Observational constraints on the merger history of galaxies since $z\approx 6$: Probabilistic galaxy pair counts in the CANDELS fields
• MMT/MMIRS spectroscopy of $z=1.3-2.4$ extreme [OIII] emitters: Implications for galaxies in the reionization-era
• Size--luminosity relations and UV luminosity functions at $z=6-9$ simultaneously derived from the complete Hubble Frontier Fields data
• Resolved spectroscopy of gravitationally lensed galaxies: global dynamics and star-forming clumps on ~100pc scales
• Unveiling the nature of bright z ~ 7 galaxies with the Hubble Space Telescope
• The [OIII]$+$H$\beta$ Equivalent Width Distribution at z$\simeq$7: Implications for the Contribution of Galaxies to Reionization
• I Zw 18 revisited with HST/ACS and Cepheids: New Distance and Age
• The Bright End of the z~9 and z~10 UV Luminosity Functions using all five CANDELS Fields
• The GREATS H$\beta$+[OIII] Luminosity Function and Galaxy Properties at $\mathbf{z}\sim 8$: Walking the Way of JWST
• Massive Star cluster formation under the microscope at z=6
• The sizes of $z\sim 6-8$ lensed galaxies from the Hubble Frontier Fields Abell 2744 data
• ALMA reveals metals yet no dust within multiple components in CR7
• Young Star Cluster Complexes in NGC 4038/39: Integral field spectroscopy using VIMOS-VLT
• The ALMA REBELS Survey: Specific Star-Formation Rates in the Reionization Era
• Resolved UV and [CII] structures of luminous galaxies within the epoch of reionisation
• Magnifying the early episodes of star formation: super star clusters at cosmological distances
• Dual constraints with ALMA: new [O III] 88 $\mu$m and dust-continuum observations reveal the ISM conditions of luminous LBGs at $z\sim 7$
• CANDELS: The correlation between galaxy morphology and star formation activity at z~2
• Probing Cosmic Dawn : Ages and Star Formation Histories of Candidate $z\ge$9 Galaxies
• Early results from GLASS-JWST. V: the first rest-frame optical size-luminosity relation of galaxies at $z>7$
• A contribution of star-forming clumps and accreting satellites to the mass assembly of z ~ 2 galaxies
• Newly Discovered Bright z~9-10 Galaxies and Improved Constraints on Their Prevalence Using the Full CANDELS Area
• Early Low-Mass Galaxies and Star-Cluster Candidates at z~6-9 Identified by the Gravitational Lensing Technique and Deep Optical/Near-Infrared Imaging
• Near-Infrared Spectroscopy of Galaxies During Reionization: Measuring CIII] in a Galaxy at $\mathbf{z}=7.5$
• Hubble Space Telescope Photometry of Hodge 301: An "Old" Star Cluster in 30 Doradus
• The discovery of rest-frame UV colour gradients and a diversity of dust morphologies in bright z ~ 7 Lyman-break galaxies
• ALMA reveals extended cool gas and hot ionized outflows in a typical star-forming galaxy at $z=7.13$
• Candidate Population III stellar complex at z=6.629 in the MUSE Deep Lensed Field
• High Equivalent Width of Hα+[N II] Emission in z~8 Lyman-break Galaxies from IRAC 5.8μm Observations: Evidence for Efficient Lyman-continuum Photon production in the Epoch of Re-ionization
• Sizes of Lensed Lower-luminosity z=4-8 Galaxies from the Hubble Frontier Field Program
• Rest-frame UV spectroscopy of extreme [OIII] emitters at $1.3<z<3.7$: Toward a high-redshift UV reference sample for JWST
• The Prevalence of Galaxy Overdensities Around UV-Luminous Lyman $\alpha$ Emitters in the Epoch of Reionization
• Searching for z > 6.5 Analogs Near the Peak of Cosmic Star Formation
• Sub-parsec resolution cosmological simulations of star-forming clumps at high redshift with feedback of individual stars
• Star-forming clumps in the Lyman Alpha Reference Sample of galaxies -- I. Photometric analysis and clumpiness
• Globular Clusters in High-Redshift Dwarf Galaxies: A Case Study from the Local Group
• Stellar populations and star formation histories of the most extreme [OIII] emitters at $z=1.3-3.7$
• The Nearby and Extremely Metal-Poor Galaxy CGCG 269-049

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