COSMOS (survey)

COSMOS (survey)
Name	COSMOS (survey)
Caption	Hubble Space Telescope mosaic of the COSMOS field
Type	Multiwavelength extragalactic survey
Durataion	2000s–present
Telescopes	Hubble Space Telescope, Subaru Telescope, Very Large Array, Spitzer Space Telescope, Chandra X-ray Observatory, XMM-Newton
Principal investigators	Nick Scoville
Country	International

COSMOS (survey) The COSMOS (Cosmic Evolution Survey) is a deep, wide-field, multiwavelength survey centered on a two-square-degree equatorial field designed to study galaxy evolution, large-scale structure, and active galactic nuclei across cosmic time. Initiated as a coordinated program using the Hubble Space Telescope, Subaru Telescope, Spitzer Space Telescope, Chandra X-ray Observatory, XMM-Newton, and the Very Large Array, the project integrates data from space- and ground-based observatories to produce contiguous imaging and spectroscopy for cosmological and extragalactic research. The survey has been led by an international team associated with institutions such as the California Institute of Technology, National Radio Astronomy Observatory, Space Telescope Science Institute, and Institute for Astronomy, University of Hawaii.

Overview

The survey field was selected to be accessible from both northern and southern facilities and was observed with instruments including the Advanced Camera for Surveys, the FOCAS spectrograph, the Suprime-Cam, the Hyper Suprime-Cam, the DEIMOS spectrograph, the VIMOS spectrograph, the ALMA array, and the IRAM facilities. COSMOS combines imaging from ultraviolet to radio wavelengths provided by missions like GALEX, Herschel Space Observatory, and WISE, enabling studies of populations such as Lyman-break galaxies, quasars, Seyfert galaxies, radio galaxies, and submillimetre galaxies. The field overlaps legacy survey regions and complements programs like the Sloan Digital Sky Survey, the CANDELS survey, the GOODS fields, and the CFHT Legacy Survey.

Scientific Goals

COSMOS was designed to address key questions linking galaxy properties to environment, halo mass, and cosmic web structure. Primary goals include mapping the evolution of the galaxy stellar mass function, tracing the growth of supermassive black holes through active galactic nuclei demographics, quantifying the role of mergers versus secular processes in star formation history, and measuring weak lensing signals to constrain dark matter distribution and cosmological parameters such as the Hubble constant and the matter density parameter. The survey aims to connect observed properties of elliptical galaxy and spiral galaxy populations with theoretical frameworks developed in simulations like the Millennium Simulation, the Illustris Project, and the EAGLE simulation.

Survey Design and Observations

The observing strategy combined high-resolution optical imaging from the Hubble Space Telescope's Advanced Camera for Surveys with deep ground-based photometry from facilities including the Subaru Telescope's Suprime-Cam, the Canada–France–Hawaii Telescope, and the Very Large Telescope instrumentation. Radio continuum mapping used the Very Large Array and later the Atacama Large Millimeter/submillimeter Array, while X-ray coverage was obtained with Chandra and XMM-Newton. Spectroscopic campaigns were undertaken with the VLT, the Keck Observatory, the Magellan telescopes, and the Gemini Observatory employing instruments like DEIMOS, VIMOS, and IMACS to secure redshifts for star-forming galaxies, Type Ia supernovae, and active galactic nuclei. Photometric redshifts were calibrated against spectroscopic samples and cross-validated using data from the COSMOS2015 catalogue and catalogs based on UltraVISTA imaging.

Data Processing and Products

Data reduction pipelines adapted methods from teams at the Space Telescope Science Institute, IPAC, and the European Southern Observatory to perform astrometric alignment, point-spread-function homogenization, and multi-band photometry extraction. Products include high-resolution mosaics, multiwavelength catalogs, photometric redshift estimates, stellar mass and star-formation rate measurements, X-ray source catalogs, radio source catalogs, weak lensing shear catalogs, and spectral line measurements. Public releases were hosted through portals linked to the NASA/IPAC Infrared Science Archive, the Canadian Astronomy Data Centre, and institutional repositories at the University of California, Los Angeles and the National Astronomical Observatory of Japan. Data products have been incorporated into meta-analyses alongside results from Planck, WMAP, and surveys like the Dark Energy Survey.

Key Results and Discoveries

COSMOS has produced results across galaxy evolution, large-scale structure, and black hole growth. Notable findings include precise measurements of the evolution of the galaxy stellar mass function, constraints on the relationship between galaxy morphology and environment consistent with hierarchical assembly predicted by Lambda-CDM cosmology, identification of proto-clusters and large-scale filaments, and statistics of obscured versus unobscured quasar populations. Weak lensing measurements from COSMOS provided tests of matter clustering and comparisons with results from CFHTLenS and KiDS, while X-ray and radio datasets improved census of active galactic nucleus feedback and starburst-driven winds linked to galactic outflows. The survey enabled targeted follow-ups that discovered high-redshift Lyman-alpha emitters, characterized submillimetre galaxies with ALMA, and constrained scaling relations between black hole mass and host galaxy properties akin to studies referencing the M–sigma relation.

Collaborations and Legacy Projects

COSMOS is a collaboration involving universities, space agencies, and observatories including NASA, the European Space Agency, the National Science Foundation, NAOJ, and consortia associated with the Hubble Space Telescope and ground-based observatories. Legacy projects and extensions built on COSMOS data include deeper programs like COSMOS-Deep, synergy with surveys such as LSST at the Vera C. Rubin Observatory, cross-calibration with Euclid and Roman Space Telescope missions, and incorporation into theoretical studies using cosmological hydrodynamic simulations like IllustrisTNG. The dataset continues to serve as a training and validation benchmark for machine-learning applications in astronomy spearheaded by groups at institutions such as Harvard University, Princeton University, Stanford University, and University of Cambridge.

Category:Astronomical surveys