Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic Star-Formation Rate Density 300 Myr after the Big Bang

TL;DR

This study leverages ultra-deep JWST and ancillary HST data in the JADES Origins Field to identify high-redshift galaxy candidates at z>12 and to constrain the evolving rest-frame UV luminosity function and cosmic star-formation-rate density. It employs a forward-modeling formalism that marginalizes over photometric redshift posteriors and non-detections, avoiding rigid binning in redshift or luminosity. The analysis finds a z≈12 UV LF in agreement with prior measurements and reveals a decline in UV luminosity density by about a factor of 2.5 from z=12 to z=14, with no robust z>15 detections; a spectroscopically confirmed z=14.32 source (183348) reinforces the reality of this early galaxy population. The results imply ongoing, rapid star formation in compact systems within early halos and highlight significant cosmic variance, underlining the need for larger-area, deeper surveys to map the dawn of galaxy formation.

Abstract

We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters spanning $0.4-0.9μ\mathrm{m}$) and novel JWST images with 14 filters spanning $0.8-5μ\mathrm{m}$, including 7 medium-band filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data at $>2.3μ\mathrm{m}$ to construct an ultradeep image, reaching as deep as $\approx31.4$ AB mag in the stack and 30.3-31.0 AB mag ($5σ$, $r=0.1"$ circular aperture) in individual filters. We measure photometric redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts $z=11.5-15$. These objects show compact half-light radii of $R_{1/2}\sim50-200$pc, stellar masses of $M_{\star}\sim10^7-10^8 M_{\odot}$, and star-formation rates of $\mathrm{SFR}\sim0.1-1\,M_{\odot}\,\mathrm{yr}^{-1}$. Our search finds no candidates at $15<z<20$, placing upper limits at these redshifts. We develop a forward modeling approach to infer the properties of the evolving luminosity function without binning in redshift or luminosity that marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the impact of non-detections. We find a $z=12$ luminosity function in good agreement with prior results, and that the luminosity function normalization and UV luminosity density decline by a factor of $\sim2.5$ from $z=12$ to $z=14$. We discuss the possible implications of our results in the context of theoretical models for evolution of the dark matter halo mass function.

Figures (21)

• Figure 1: F444W/F200W/F090W false color red/green/blue image of the JADES Origin Field (background image; 27.5 arcmin$^{2}$), the JOF F162M footprint (jade outline) and F356W+F410M+F444W/F200W+F210M/F090W+F115W false color red/green/blue thumbnail images (each 0.86 arcsec$^2$) for $z\gtrsim12$ high-redshift galaxy candidates. The RGB images of the galaxy candidates typically appear to have a green hue in this color space, as they are all detected in the filters used for both the green and red channels, but not the blue channel. Each inset thumbnail lists the best-fit EAZY photometric redshift and the JADES NIRCam ID, and we indicate the shared angular scale of the thumbnails with a scale bar showing 0.2". Table \ref{['tab:properties']} lists the designations of the objects based on [RA, Dec]. NIRCam ID 183348 was spectroscopically confirmed as JADES-GS-z14-0 by Carniani et al. (submitted) at $z=14.32$.
• Figure 2: SED model, photometric redshift posterior distributions, and JWST NIRCam image thumbnails for galaxy candidate JADES+53.09731-27.84714 (NIRcam ID 74977). The upper left panel shows the aperture-corrected $r=0.1"$ flux density $f_\nu$ in nJy of the NIRCam (purple points with $1\sigma$ uncertainties) and HST/ACS (red points with $1\sigma$ uncertainties) photometry for the object, with median photometric offset corrections applied. The best-fit SED is shown in blue, while the best fit low-redshift solution is shown in gray. The synthetic model photometry for both models are shown as open squares, and the JWST NIRCam filter transmission curves are shown as colored regions. The upper right panel shows the posterior distribution of photometric redshifts for the object (blue), the best-fit redshift (vertical dashed line), the photo-$z$ posterior if only redshifts $z<7$ are considered (light gray), and the best-fit redshifts provided as an annotation, as is the posterior probability density at redshifts below $z\sim7$. The bottom panel shows inverted grayscale thumbnails of the fourteen NIRCam filters in a $0.93\times0.93$ arcsec$^{2}$ region around each object, the stretch applied to each filter scaled with the mean value in the thumbnail. The signal-to-noise ratio of the aperture-corrected $r=0.1"$ circular aperture photometry for each band is noted in the corresponding thumbnail. The JADES NIRCam ID is also provided on the left side of the image.
• Figure 3: Same as Figure \ref{['fig:sed_74977']}, but for galaxy candidate JADES+53.02618-27.88716 (NIRCam ID 16699).
• Figure 4: Same as Figure \ref{['fig:sed_74977']}, but for galaxy candidate JADES+53.04017-27.87603 (NIRCam ID 33309).
• Figure 5: Same as Figure \ref{['fig:sed_74977']}, but for galaxy candidate JADES+53.03547-27.90037 (NIRCam ID 160071).