[Paper Review] Candidate Primeval Galaxies in the Hubble Deep Field

D. L. Clements, W. J. Couch|arXiv (Cornell University)|May 21, 1996

Galaxies: Formation, Evolution, Phenomena1 references3 citations

TL;DR

This paper identifies 8 candidate primeval galaxies at redshifts 2.6 < z < 3.9 in the Hubble Deep Field using Ly-break selection at 912Å. Despite being significantly brighter than L* galaxies (M_B ≈ -22), they are smaller and morphologically disturbed, suggesting ongoing merging—evidence that galaxy formation may be observed in progress during this epoch.

ABSTRACT

We present the results of colour-selection of candidate high redshift (2.6 $

Motivation & Objective

• To identify high-redshift galaxies in the Hubble Deep Field using Ly-break selection at 912Å.
• To estimate the comoving number density of such high-redshift galaxies.
• To characterize the physical and morphological properties of candidate primeval galaxies.
• To assess whether these objects represent ongoing galaxy formation processes.
• To compare their luminosities and sizes to local L* galaxies.

Proposed method

• Applied colour-selection techniques based on the Lyman break at 912Å to identify high-redshift candidates.
• Used photometric data from the Hubble Deep Field to determine magnitudes and redshifts via SED fitting.
• Assessed morphological features through visual inspection of Hubble images.
• Calculated comoving number density assuming a flat universe with q0 = 0.5 and H0 = 100 km s⁻¹ Mpc⁻¹.
• Compared absolute magnitudes (M_B) and effective radii to local L* galaxies.
• Evaluated merging signatures such as multiple nuclei, tails, and plumes in the images.

Experimental results

Research questions

• RQ1 What is the comoving number density of high-redshift galaxies (2.6 < z < 3.9) selected via the Ly-break at 912Å in the Hubble Deep Field?
• RQ2 How do the luminosities and sizes of these candidate primeval galaxies compare to local L* galaxies?
• RQ3 What morphological features do these high-redshift candidates exhibit, and what do they imply about their formation state?
• RQ4 Can the observed properties of these galaxies be interpreted as evidence for ongoing galaxy formation via merging?
• RQ5 Do theoretical models of hierarchical galaxy formation find support in the observed properties of these objects?

Key findings

• Eight candidate primeval galaxies were identified in the Hubble Deep Field with redshifts between 2.6 and 3.9.
• These galaxies have a comoving number density comparable to that of nearby bright galaxies in a flat universe with q₀ = 0.5 and H₀ = 100 km s⁻¹ Mpc⁻¹.
• Their absolute magnitudes are significantly brighter than L* (typically M_B ≈ -22), indicating high luminosity.
• Despite their high luminosity, they are generally smaller in size than local galaxies of similar luminosity.
• Visual inspection reveals all eight are highly disturbed, with multiple nuclei, tails, and plumes, indicating ongoing merging processes.
• The morphological and luminosity characteristics suggest these galaxies are undergoing formation via hierarchical merging, consistent with theoretical models of galaxy formation.