Lyman-break galaxies

Lyman-break galaxies
Name	Lyman-break galaxy
Type	High-redshift star-forming galaxy
Epoch	Reionization and post-reionization epochs
Redshift	z ≳ 2
Mass	10^8–10^11 M☉ (stellar)
Notable	Steidel et al. 1996 selection technique

Lyman-break galaxies

Lyman-break galaxies are high-redshift, ultraviolet-bright star-forming galaxies identified by a strong spectral discontinuity at the Lyman limit. First systematically isolated in the 1990s, they serve as tracers of early galaxy formation, star formation rates, and cosmic structure during epochs probed by instruments and surveys such as the Keck Observatory, Hubble Space Telescope, and Subaru Telescope. Studies of these objects intersect work by teams and programs including Steidel, Adelberger, Shapley, the GOODS survey, and the Hubble Ultra Deep Field.

Introduction

Lyman-break galaxies were popularized by the dropout selection pioneered by Charles C. Steidel, linking photometric techniques to spectroscopic follow-up at facilities like the W. M. Keck Observatory and the Hubble Space Telescope. Early programs conducted by groups associated with Caltech and Carnegie Observatories established connections to contemporaneous surveys such as Sloan Digital Sky Survey and to theory from groups at Princeton University and Cambridge University. Subsequent work involved collaborations with teams at Space Telescope Science Institute, National Optical Astronomy Observatory, and the Subaru Telescope consortium.

Physical properties

These galaxies typically have stellar masses in the range estimated by population-synthesis modeling used by groups at Max Planck Institute for Astronomy and Harvard–Smithsonian Center for Astrophysics, and ultraviolet luminosities constrained by measurements from Hubble Space Telescope instruments such as Wide Field Camera 3 and Advanced Camera for Surveys. Spectroscopy with instruments on Keck I, Very Large Telescope, and Gemini Observatory reveals strong rest-frame ultraviolet absorption and emission lines associated with massive stars and stellar winds studied by researchers at University of California, Santa Cruz and Yale University. Dust attenuation laws applied by teams at Johns Hopkins University and University of Arizona are used to infer intrinsic star-formation rates comparable to those in submillimeter-selected samples from facilities such as Atacama Large Millimeter/submillimeter Array. Kinematic studies using integral-field units developed at European Southern Observatory and National Astronomical Observatory of Japan probe velocity dispersions and rotation that link to dark-matter halo masses predicted in simulations by groups at Institute for Advanced Study and Lawrence Berkeley National Laboratory.

Detection and selection techniques

The dropout technique exploits the break at 912 Å first characterized in early ultraviolet surveys by teams at Goddard Space Flight Center and applied in deep imaging by the Hubble Deep Field and the Hubble Ultra Deep Field programs. Photometric color cuts employed by survey consortia such as CANDELS and COSMOS use filter sets on telescopes including Subaru Telescope, VLT, and CFHT to isolate candidates for spectroscopic confirmation with facilities like Keck Observatory and Magellan Observatory. Selection strategies developed by Steidel et al. were refined by catalogs from the Great Observatories Origins Deep Survey and follow-up campaigns by collaborations at Carnegie Mellon University and University of California, Berkeley. Machine-learning classifiers implemented in projects at Stanford University and University of Toronto have been used alongside photometric-redshift codes from teams at University of Oxford and Institut d'Astrophysique de Paris.

Formation and evolution

Models of star formation and feedback calibrated by research groups at MIT and Princeton University place these galaxies within hierarchical structure formation frameworks advanced by teams at Kavli Institute for Cosmology and Max Planck Institut für Astrophysik. Cosmological simulations such as those run by collaborations at Illustris and EAGLE consortia have been compared to observed luminosity functions measured by the Keck and HST teams. Chemical-enrichment histories inferred by spectroscopic analyses performed at University of Cambridge and University of Chicago link early stellar populations to later descendants studied in surveys like DEEP2 and zCOSMOS. Feedback processes examined by researchers at Carnegie Institution and Flatiron Institute mediate gas inflows and outflows observed with instruments on ALMA and Chandra X-ray Observatory.

Role in cosmic reionization and large-scale structure

Lyman-break galaxy populations at z ≳ 6 identified by the Hubble Space Telescope and ground-based observatories contribute to constraints on the timing of cosmic reionization studied alongside results from the Planck satellite and reionization models from groups at Harvard University and Rutgers University. Clustering measurements using samples from surveys including COSMOS and GOODS inform halo-occupation models developed by teams at University of Pennsylvania and Ohio State University, linking these galaxies to the cosmic web mapped by projects like BOSS and eBOSS. Cross-correlation studies with 21-cm experiments involving collaborations at Square Kilometre Array precursor facilities probe the interplay between ultraviolet sources and neutral hydrogen, a topic of active work at University of Cambridge and University of Melbourne.

Observational surveys and instruments

Key instruments and surveys include the Hubble Space Telescope programs (HDF, HUDF, CANDELS), ground-based campaigns with Keck Observatory and Subaru Telescope, and millimeter follow-up with ALMA and JCMT. Spectroscopic confirmation has relied on spectrographs at Keck II and Very Large Telescope as part of follow-up programs run by groups at Caltech, UC Berkeley, and European Southern Observatory. Future prospects involve observations with the James Webb Space Telescope and planned facilities associated with the Thirty Meter Telescope and Extremely Large Telescope, with survey planning undertaken by consortia including STScI and international partners.

Category:High-redshift galaxies