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A nuclear disc at Cosmic Noon: evidence of early bar-driven galaxy evolution

Zoe A. Le Conte, Dimitri A. Gadotti, Thomas Harvey, Leonardo Ferreira, Christopher J. Conselice, Taehyun Kim, Camila de Sá-Freitas, Francesca Fragkoudi, Justus Neumann, E. Athanassoula

TL;DR

This study leverages JWST CEERS data to address whether bar-driven processes and nuclear disc formation occur during Cosmic Noon. By applying unsharp masking, three-component photometric decomposition, isophotal analysis, and resolved SED fitting, the authors identify a bar-built, star-forming nuclear disc in CEERS-4031 at $z = 1.461$, with $R_{ND} \approx 1.3$ kpc and a long bar of $L_{bar} \approx 5.33$ kpc (and a nuclear bar of $L_{NB} \approx 1.05$ kpc), accompanied by elevated SFR density and younger ages within the nucleus. These results extend the ND–bar size relation to Cosmic Noon and support early bar-driven gas inflow and disc maturation, challenging models that confine such processes to lower redshifts. The findings underscore the need for population studies of high-redshift nuclear discs and future JWST IFU tasks to age-date bars and quantify their impact on galaxy evolution and AGN fueling.

Abstract

Recent studies have revealed that bars can form as early as a few billion years after the Big Bang, already displaying similar characteristics of evolved bars in the Local Universe. Bars redistribute angular momentum across the galaxy, regulating star formation, AGN activity, and building new stellar structures such as nuclear discs. However, the effects of bar-driven evolution on young galaxies are not yet known, as no evidence of bar-built stellar structures has ever been found beyond $z = 1$, until now. In this work, we show evidence of a bar-built, star-forming nuclear disc, already present at redshift $z = 1.5$. This is the first evidence of a bar-built stellar structure at Cosmic Noon. We find that this nuclear disc is actively forming stars and has the same size as some nuclear discs in nearby galaxies. This evidence solidifies the now emerging picture in which bars are fundamental not only in the late evolution of galaxies, but also in their early evolutionary stages. It changes the current paradigm by urging a revision of our picture of galaxy evolution beyond redshift one, to include new considerations on the role played by bars as early as a few billion years after the Big Bang.

A nuclear disc at Cosmic Noon: evidence of early bar-driven galaxy evolution

TL;DR

This study leverages JWST CEERS data to address whether bar-driven processes and nuclear disc formation occur during Cosmic Noon. By applying unsharp masking, three-component photometric decomposition, isophotal analysis, and resolved SED fitting, the authors identify a bar-built, star-forming nuclear disc in CEERS-4031 at , with kpc and a long bar of kpc (and a nuclear bar of kpc), accompanied by elevated SFR density and younger ages within the nucleus. These results extend the ND–bar size relation to Cosmic Noon and support early bar-driven gas inflow and disc maturation, challenging models that confine such processes to lower redshifts. The findings underscore the need for population studies of high-redshift nuclear discs and future JWST IFU tasks to age-date bars and quantify their impact on galaxy evolution and AGN fueling.

Abstract

Recent studies have revealed that bars can form as early as a few billion years after the Big Bang, already displaying similar characteristics of evolved bars in the Local Universe. Bars redistribute angular momentum across the galaxy, regulating star formation, AGN activity, and building new stellar structures such as nuclear discs. However, the effects of bar-driven evolution on young galaxies are not yet known, as no evidence of bar-built stellar structures has ever been found beyond , until now. In this work, we show evidence of a bar-built, star-forming nuclear disc, already present at redshift . This is the first evidence of a bar-built stellar structure at Cosmic Noon. We find that this nuclear disc is actively forming stars and has the same size as some nuclear discs in nearby galaxies. This evidence solidifies the now emerging picture in which bars are fundamental not only in the late evolution of galaxies, but also in their early evolutionary stages. It changes the current paradigm by urging a revision of our picture of galaxy evolution beyond redshift one, to include new considerations on the role played by bars as early as a few billion years after the Big Bang.
Paper Structure (10 sections, 2 equations, 3 figures, 1 table)

This paper contains 10 sections, 2 equations, 3 figures, 1 table.

Table of Contents

  1. Introduction
  2. Data analysis
  3. Data
  4. Unsharp masking
  5. Photometric decompositions
  6. Isophotal analysis
  7. SED fitting
  8. Results
  9. Discussion
  10. Conclusions

Figures (3)

  • Figure 1: The galaxy images from seven NIRCam filters, annotated in the top-left corner of each image with the filter name and rest-frame wavelength for a redshift of $z = 1.461$. A circle depicting 2×FWHM of the PSF is shown in the lower-left corner of each image. The lower-right panel is an RGB image obtained from the filters F115W, F150W and F200W.
  • Figure 2: Image analysis of the galaxy in the F150W (top row) and F200W (bottom row) NIRCam filters. From left to right: NIRCam image; unsharp masked image; IMFIT residual image for a multi-component fit; isophotal ellipse fitting of the NIRCam image; ellipticity radial profile from ellipse fitting, showing the peak in ellipticity of the nuclear bar in the nuclear disc as a dashed line and of the main bar as a dotted line. The nuclear disc size, measured with visual inspection of the images, is shown as a dot-dashed circle in the unsharp masked and residual images.
  • Figure 3: Resolved property maps from NIRCam SED fitting. Left to right: stellar mass density, SFR density, and the strength of the 4000Å break.