DEEP2

DEEP2
Name	DEEP2 Redshift Survey
Organization	University of California, Berkeley; California Institute of Technology; W. M. Keck Observatory
Country	United States
Established	2002
Telescope	Keck Observatory Keck I and Keck II
Instrument	DEIMOS
Wavelength	Optical
Area	3 square degrees
Objects	Galaxies at z ~ 0.7–1.5

DEEP2 is a major extragalactic redshift survey conducted in the early 2000s that measured spectra for tens of thousands of galaxies at intermediate to high redshift using the Keck Observatory's DEIMOS instrument. The project involved teams from institutions such as University of California, Berkeley, California Institute of Technology, and the Harvard & Smithsonian Center for Astrophysics and produced catalogues widely used by researchers working on dark energy, structure formation, and galaxy evolution. DEEP2 observations were taken in fields overlapping with surveys like COSMOS, GOODS, and the Sloan Digital Sky Survey footprints, enabling multiwavelength cross-correlation with space missions including Hubble Space Telescope, Spitzer Space Telescope, and Chandra X-ray Observatory.

Overview

DEEP2 targeted galaxies in several well-studied fields including patches near Extended Groth Strip, CFHT Legacy Survey regions, and fields chosen for overlap with the AEGIS collaboration. The survey used photometric preselection from imaging provided by facilities such as Canada–France–Hawaii Telescope and the Palomar Observatory before spectroscopic follow-up with W. M. Keck Observatory. Principal investigators and collaborators came from groups associated with University of California, Santa Cruz, University of Hawaii, Lawrence Berkeley National Laboratory, and University of Toronto. DEEP2's design emphasized high spectral resolution and high redshift completeness to probe clustering and environment dependencies relevant to studies initiated by teams at Santa Cruz Institute for Particle Physics and linked to theoretical work at Princeton University and Institute for Advanced Study.

Survey design and instrumentation

The survey used the DEIMOS multi-object spectrograph mounted on Keck II, employing slitmasks patterned using targets selected from imaging by Subaru Telescope and Canada–France–Hawaii Telescope. DEEP2 exploited custom-built slitmasks and the Keck Observatory Archive scheduling coordinated with observing runs allocated through committees at National Science Foundation-funded observatories and programs directed by California Institute of Technology astronomers. Instrumental choices were guided by prior work with instruments like LRIS and informed by detector technologies developed at Lawrence Berkeley National Laboratory and NASA Jet Propulsion Laboratory. The high resolution mode allowed velocity dispersion and emission-line studies comparable in spectral quality to work done with VLT (Very Large Telescope) instruments such as FORS and VIMOS.

Data reduction and analysis

Raw spectra were processed with pipelines influenced by software from Space Telescope Science Institute and analysis techniques used in the Sloan Digital Sky Survey and 2dF Galaxy Redshift Survey. The team used redshift measurement procedures related to algorithms developed at Max Planck Institute for Astronomy and statistical frameworks akin to methods from Harvard University and Yale University groups. Calibration employed spectrophotometric standards tied to catalogs from Two Micron All Sky Survey and photometric catalogs assembled by collaborators at University of California, Berkeley and University of Washington. Quality assessment and error modeling borrowed approaches from surveys like DEEP1 and the CNOC2 Redshift Survey, while cosmological parameter inference used likelihood tools popularized by teams at University of Chicago and Stanford University.

Scientific results

DEEP2 produced measurements of the galaxy two-point correlation function at z ~ 1, building on clustering analyses pioneered by groups at Max Planck Institute for Astrophysics and confirming trends explored in VIMOS VLT Deep Survey. Results on galaxy color bimodality, star-formation quenching, and mass assembly were cross-referenced with imaging from Hubble Space Telescope programs like COSMOS and GOODS. DEEP2 delivered constraints on dark energy and matter clustering complementary to probes from WMAP, Planck, and Type Ia supernova programs led by teams at Lawrence Berkeley National Laboratory and Carnegie Observatories. Studies using DEEP2 informed theoretical models developed at Princeton University, Harvard–Smithsonian Center for Astrophysics, and Institute for Advanced Study and were cited alongside work from SDSS and 2dFGRS in discussions of halo occupation distribution models originating from University of Zurich and University of Durham research groups.

Catalogue and data products

The public DEEP2 catalogues included redshifts, spectral classifications, and derived quantities such as stellar masses and star-formation rates using spectral energy distribution techniques comparable to pipelines at Max Planck Institute for Extraterrestrial Physics and University of Oxford. Data products were archived alongside imaging from Palomar Observatory and infrared measurements from Spitzer Space Telescope, enabling multiwavelength studies with inputs from teams at Johns Hopkins University, University of Michigan, and Columbia University. Metadata and slitmask designs were documented for reuse by projects at Carnegie Mellon University and University of Arizona, and catalogue versions were distributed to analysis groups at European Southern Observatory for comparative studies with VIMOS-based surveys.

Legacy and impact on cosmology

DEEP2's legacy includes precision measurements of galaxy evolution at z ~ 1 that informed subsequent surveys such as DEEP3, PRIMUS, zCOSMOS, and preparatory work for projects like Dark Energy Survey, Euclid, and Nancy Grace Roman Space Telescope. The survey's methodology influenced instrument designs and observing strategies at W. M. Keck Observatory and inspired theoretical synthesis at institutions including Caltech, Stanford University, and Princeton University. DEEP2 data continue to be used in cross-survey analyses with cosmic microwave background results from Planck and lensing measurements from CFHTLenS, contributing to constraints on structure growth discussed in collaborations involving Kavli Institute for the Physics and Mathematics of the Universe and Perimeter Institute for Theoretical Physics.

Category:Galaxy surveys