Extended Groth Strip

Extended Groth Strip
Name	Extended Groth Strip
Caption	Deep multiwavelength view of a high-redshift field
Epoch	J2000
Type	Deep extragalactic survey field
Discovery	1990s
Survey	All-wavelength programs including Hubble Space Telescope, Spitzer Space Telescope, Chandra X-ray Observatory

Extended Groth Strip The Extended Groth Strip is a deep extragalactic survey field located in the northern celestial hemisphere designed to study galaxy evolution, large-scale structure, and active galactic nuclei across cosmic time. Initiated with imaging from the Hubble Space Telescope and reinforced by follow-up from facilities such as the Keck Observatory, Subaru Telescope, Spitzer Space Telescope, and the Chandra X-ray Observatory, the field has become a multiwavelength benchmark for extragalactic astronomy. The survey has enabled coordinated programs by institutions including NASA, the European Space Agency, and numerous university consortia.

Introduction

The project began as an extension of the original Groth Strip survey led by teams using the Hubble Space Telescope's Wide Field Camera 2 and later the Advanced Camera for Surveys, expanding the footprint to improve statistics on faint galaxies, active galactic nuclei seen by Chandra X-ray Observatory, and infrared sources detected by Spitzer Space Telescope. Observing strategies incorporated spectroscopy from the Keck Observatory's DEIMOS instrument and photometry from the Canada–France–Hawaii Telescope, enabling redshift measurements comparable to those from the Sloan Digital Sky Survey for complementary populations. The field overlaps with follow-up programs by the Herschel Space Observatory and ground-based millimeter arrays like the Atacama Large Millimeter/submillimeter Array.

Observations and Surveys

Deep optical imaging came from the Hubble Space Telescope surveys using Advanced Camera for Surveys and catalogs tied to photometric systems from the Sloan Digital Sky Survey and the Pan-STARRS project. Infrared mapping was provided by the Spitzer Space Telescope's Infrared Array Camera and Multiband Imaging Photometer for Spitzer, augmented by far-infrared data from the Herschel Space Observatory's PACS and SPIRE instruments. X-ray coverage was secured with the Chandra X-ray Observatory and supplemented by the XMM-Newton mission. Spectroscopic campaigns used the Keck Observatory's DEIMOS and LRIS spectrographs, the MMT Observatory, and the Subaru Telescope's instruments, while radio observations came from the Very Large Array and the Giant Metrewave Radio Telescope.

Galaxy Populations and Morphology

Analysis of galaxy populations in the field has classified large samples into star-forming systems observed with Spitzer Space Telescope mid-infrared colors and quiescent galaxies identified by rest-frame colors akin to those studied in the COSMOS survey. Morphological studies used high-resolution imaging from the Hubble Space Telescope to quantify bulge–disk decompositions similar to techniques developed for the Hubble Deep Field and CANDELS programs. The field provided samples of luminous infrared galaxies comparable to Ultraluminous infrared galaxy studies and revealed compact quiescent galaxies analogous to those reported by surveys using the Keck Observatory. Surveys also identified populations of AGNs related to X-ray selected samples from Chandra X-ray Observatory and optically selected quasars comparable to catalogs from the Sloan Digital Sky Survey.

Large-scale Structure and Environment

Redshift surveys in the field mapped filamentary large-scale structure and galaxy overdensities resembling protocluster candidates studied in the DEEP2 Galaxy Redshift Survey and the zCOSMOS project. Environmental analyses compared galaxy properties in dense regions to those in void-like environments, referencing comparison datasets from the Sloan Digital Sky Survey and the 2dF Galaxy Redshift Survey. Measurements of galaxy clustering used techniques similar to those applied in the VIPERS and BOSS surveys to constrain bias and halo occupation distributions. The field's footprint enabled cross-correlation studies with cosmic shear measurements from programs like CFHTLenS.

Multiwavelength Data and Instrumentation

The Extended Groth Strip assembled datasets across the electromagnetic spectrum: ultraviolet imaging from the Galaxy Evolution Explorer, optical from Hubble Space Telescope and ground-based observatories including Subaru Telescope and Keck Observatory, infrared from Spitzer Space Telescope and Herschel Space Observatory, X-ray from Chandra X-ray Observatory and XMM-Newton, and radio from the Very Large Array. Millimeter and submillimeter follow-up utilized the Atacama Large Millimeter/submillimeter Array and the James Clerk Maxwell Telescope. Instrumental calibration and photometric redshift estimation leveraged techniques refined in the COSMOS and GOODS surveys, while spectroscopic redshifts tied into legacy catalogs like those from the DEEP2 Galaxy Redshift Survey.

Scientific Results and Impact

Key results include measurements of the evolution of the stellar mass function connected to findings from the CANDELS and UltraVISTA surveys, constraints on the growth of supermassive black holes consistent with results from the Chandra Deep Field and SDSS quasar studies, and characterization of dust-obscured star formation paralleling work from the Herschel Space Observatory. Morphological transformation pathways inferred from the field complemented theoretical predictions from simulations such as Illustris and EAGLE, and comparisons to predictions from the Lambda-CDM model informed galaxy-halo connection studies akin to those in BOSS analyses. The field has been widely used for training machine-learning classifiers in astronomy, following applications demonstrated in COSMOS and CANDELS.

Future Work and Ongoing Studies

Ongoing studies plan deeper spectroscopy with next-generation instruments on Keck Observatory and surveys with the James Webb Space Telescope to probe high-redshift galaxy assembly similar to programs in the Hubble Ultra Deep Field. Planned radio and millimeter improvements include observations with the Square Kilometre Array pathfinders and expanded Atacama Large Millimeter/submillimeter Array programs to study cold gas reservoirs, complementing upcoming wide-area surveys by the Vera C. Rubin Observatory and spectroscopic campaigns aligned with the Dark Energy Spectroscopic Instrument. Continued multiwavelength synergy will connect the field to legacy science from missions like Hubble Space Telescope, Spitzer Space Telescope, and Chandra X-ray Observatory while enabling comparisons to simulations from the IllustrisTNG project.

Category:Extragalactic astronomy