A Large Population of Faint 8 < z < 16 Galaxies Found in the First JWST NIRCam Observations of the NGDEEP Survey

We present an early analysis on the search for high-redshift galaxies using the deepest public JWST imaging to date, the NGDEEP field. These data consist of six-band NIRCam imaging on the Hubble Ultra Deep Field Parallel 2 (HUDF-Par2), covering a total area of 6.3 arcmin(2). Based on our initial reduction of the first half of this survey, we reach 5 sigma depths up to mag = 29.5-29.9 between 1 and 5 mu m. Such depths present an unprecedented opportunity to begin exploring the very early universe with JWST. As such, we find high-redshift galaxies by examining the spectral energy distribution of all F444W detections and present 16 new z > 8.5 galaxies identified using two different photometric redshift codes: LePhare and EAZY combined with other significance criteria. The highest-redshift object in our sample is at = z 15.6(-0.3)(+0.4), which has a blue beta = - 3.02(+0.42) (-0.46) and a very low inferred stellar mass of M* - 10(7.4) M-circle dot We also discover a series of faint, low-mass dwarf galaxies with M* < 10(8.5) Me at z similar to 9 that have blue colors, flat surface brightness profiles, and small sizes <1 kpc. Comparing to previous work in the HUDF-Par2, we find 21 6 < z < 9 candidates including two z = 8 major mergers. One of these merger candidates has an additional two z = 8 sources within 30 '', indicating that it may form part of an overdensity. We also compare our results to theory, finding no significant disagreement with a few cold-dark-matter-based models. The discovery of these objects demonstrates the critical need for deeper, or similar depth but wider-area, JWST surveys to explore the early universe.

Automated summary

This study presents an early analysis of the search for high-redshift galaxies using deep JWST imaging in the NGDEEP field. The data reaches unprecedented depths, allowing for the identification of 16 new galaxies with redshifts greater than 8.5. Additionally, a series of faint, low-mass dwarf galaxies with blue colors and small sizes were discovered.