Probing High-Redshift Galaxy Formation at the Highest Luminosities: New Insights from DEIMOS Spectroscopy

TL;DR

This study uses DEIMOS spectroscopy to analyze the properties of the most UV-luminous star-forming galaxies at redshifts 3.2 to 4.6, revealing insights into outflows, feedback, and galaxy evolution at high luminosities.

Contribution

It provides one of the largest spectroscopic samples of UV-luminous galaxies at high redshift, uncovering new details about outflows, feedback mechanisms, and galaxy mergers in the early universe.

Findings

Increased Lya emission fraction at lower UV luminosities.

Detection of large-scale outflows with velocity offsets up to 1140 km/s.

Discovery of a massive galaxy overdensity at z=3.78.

Abstract

We present DEIMOS spectroscopic observations of the most UV-luminous star-forming galaxies at 3.2<z<4.6. Our sample contains galaxies with luminosities of L*<L<7L* and is one of the largest samples to date of the most UV-luminous galaxies at these redshifts. Our data confirm 41 star-forming galaxies at 3.2<z<4.6 and validate the clean selection of the photometric candidates. We find that the fraction of Lya emitting galaxies increases with decreasing UV luminosity. We find strong evidence of large-scale outflows, transporting the neutral/ionized gas in the interstellar medium away from the galaxy. Galaxies exhibiting both interstellar absorption and Lya emission lines show a significant velocity offset between the two features (200-1140 km/s). We find tentative evidence that this measure of the outflow velocity increases with UV luminosity and/or stellar mass. The luminosity- and mass-dependent outflow strengths suggest that the efficiency of feedback and enrichment of the surrounding medium depend on these parameters. We present composite spectra of the absorption-line-only and Lya-emitting subsets of the UV luminous galaxies at z~3.7. The composite spectra are similar to those of lower-z and lower-luminosity LBGs samples, but with some subtle differences. Analyses of the composite spectra suggest that the UV luminous LBGs at z~3.7 may have a higher covering fraction of absorbing gas, and may be older than their lower-z and lower-luminosity counterparts. In addition, we have discovered 5 galaxies that belong to a massive overdensity at z=3.78. Finally, two galaxies each show two distinct sets of interstellar absorption features. The latter may be a sign of a final stage of major merger, or clumpy disk formation. Their presence implies that frequency of such sources among our luminous z~3.7 LBGs may be an order of magnitude higher than in lower redshift and lower luminosity samples.