---
title: 'GAMA Survey: Galaxy Assembly Overview'
url: https://www.emergentmind.com/topics/galaxy-and-mass-assembly-gama-survey
type: topic
---

# GAMA Survey: Galaxy Assembly Overview

The Galaxy and Mass Assembly (GAMA) Survey is a large-scale spectroscopic and multiwavelength imaging program, originally conceived to provide a highly complete, uniform, and panchromatic census of galaxy populations in the low-to-intermediate redshift universe ($z \lesssim 0.5$). Leveraging extensive observational campaigns with the Anglo-Australian Telescope, sophisticated survey tiling algorithms, and coordinated imaging from the ultraviolet to the far-infrared, GAMA delivers precise redshifts, robust structural, dynamical, and environmental measurements, and extensive value-added data products. The survey stands as a primary empirical reference for galaxy evolution studies, benchmarking semi-analytic and hydrodynamical models, and enabling precision analyses of baryonic and dark matter assembly.

## 1. Survey Design, Scope, and Spectroscopic Methodology

GAMA's footprint encompasses five contiguous sky regions: three equatorial strips (G09, G12, G15, each ~60 deg²), the southern G23 field (50.6 deg²), and the G02 field (55.7 deg²) overlapping deep X-ray (XXL) and redshift surveys (VIPERS). The main sample imposes a simple $r_{\rm Petrosian} < 19.8$ mag flux limit, ensuring effective volume-limited selection with a sharp, magnitude-driven selection function [1507.00665, 1711.09139, 1506.08222, 1009.0614].

Spectroscopy is conducted with the 2dF/AAOmega system on the 3.9 m AAT. The dual-arm spectrograph yields spectral coverage from 3700 Å to 8850 Å at $R\simeq1300$–1700. Each observing tile can allocate up to 400 fibres, with $2''$ apertures, and repeated tiling ensures >98% redshift completeness even in high-density regions and for close pairs [1212.6491, 1301.7127]. The automatic redshifting pipeline employs both template cross-correlation (e.g., autoz) and manual curation, delivering redshift accuracy $\sigma_v\approx 27$–50 km s$^{-1}$ and incorrectness rates <1% for high-quality (nQ≥3) spectra [1506.08222].

Multiwavelength imaging is assembled from GALEX (FUV, NUV), VST/KiDS (ugri), VISTA/VIKING (ZYJHK$_s$), WISE (W1–W4), Herschel-ATLAS (PACS, SPIRE), and radio surveys, homogenized via PSF-matching, mosaicking (SWARP), and robust background subtraction [2005.11215, 1711.09139].

## 2. Value-Added Catalogues: Stellar Masses, Star Formation, and Structural Measurements

GAMA’s value-added products include:

- **Stellar Masses:** Bayesian SED modeling using u–K photometry and Bruzual & Charlot (2003) populations with a Chabrier IMF, and consistent mass-to-light ratio calibration across ugrizYJHK [1212.6491, 1506.08222].
- **Star Formation Rates:** H$\alpha$-derived SFRs utilize robust emission-line fitting, aperture corrections, and dust attenuation correction via the Balmer decrement. SFR calibration assumes
  $$
  \mathrm{SFR}~[M_\odot~\rm{yr}^{-1}] = 4.4\times10^{-42}~L_\mathrm{H\alpha}~[\mathrm{erg~s^{-1}}]
  $$
  [1301.7127, 1506.08222].
- **Two-Dimensional Structural Parameters:** Using the SIGMA pipeline (Source Extractor, PSFEx, GALFIT3), galaxies are modeled with 2D Sérsic profiles out to $10R_e$ in $ugrizYJHK$. High-n systems gain $\Delta m\sim0.5$ mag over Petrosian photometry, enabling accurate total-flux and size measurements. The dataset allows separation of early- and late-type galaxies via K-band $n$ versus $u{-}r$ color [1112.1956].

## 3. Panchromatic Data and Matched-Aperture Photometry

The panchromatic coverage is a defining feature of GAMA. Systematic assembly of photometry across UV–optical–NIR–MIR–FIR bands, using rigorous aperture-matching and common astrometric/PSF frames, enables precise energy-distribution and SED fits. The ProFound package is now adopted for matched-segment photometry across $FUV\,NUV\,ugriZYJHK_s\,W1\ldots S500$ (DR4), yielding pseudo-total fluxes robust to background fluctuations and deblending [2005.11215].

WISE–Herschel bands, unresolved at GAMA depths, are measured via PSF-convolved modeling (ProFit+EM) at all catalog positions and supplemented with residual source detection. The pipeline achieves detection fractions up to 62% (WISE W3) for $r<20.5$ galaxies. All photometry is Galactic-extinction corrected [2005.11215].

## 4. Environmental, Large-Scale Structure, and Group Catalogues

GAMA provides a suite of environment measures:
- **Local Densities:** $\Sigma_5$, $N_\mathrm{cyl}$, adaptive ellipsoidal metrics [1506.08222].
- **FoF Group Finder:** Friends-of-Friends algorithms deliver group catalogues ($\sim$14,000 groups), including group-centric properties (velocity dispersion, radius, total luminosity, brightest group galaxy) and dynamical/stellar/luminosity-based halo mass estimates [1212.6491, 1404.6828].
- **Large-Scale Structure:** Alpaslan et al. (2013) employ MST-based algorithms to decompose the GAMA volume into filaments (643 detected in G09–G15), tendrils, and voids, with quantitative agreement with Millennium+GALFORM mocks [1311.1211].

Cluster detection using the Delaunay Tessellation Field Estimator and caustic analysis yields 113 clusters with masses $10^{12}$–$10^{16}~M_\odot$, with spatial clustering (correlation length $r_0 = 21.5\pm2.3$ Mpc) in line with tSZ and X-ray cluster surveys [1410.0748].

## 5. Statistical Analyses, Empirical Relations, and Model Confrontation

The GAMA sample's completeness supports detailed measurement of luminosity and stellar mass functions, environmental dependencies, and scaling relations:
- **Luminosity Functions:** SWML and Schechter fitting reveal dependence on overdensity $\delta_8$, with smooth trends in $\phi^*$ and $M^*$ across $-1 < \delta_8 < 7$. Semi-analytic models qualitatively match these trends but show over-quenching of faint satellites and under-efficient AGN feedback in low-mass halos [1409.4681].
- **Mass–Metallicity–SFR Plane:** Joint GAMA+SDSS analyses confirm non-evolving mass–metallicity–SFR “fundamental planes” for star-forming galaxies, with modest metallicity decline ($\lesssim$0.1 dex) and $\sim$0.4 dex SFR increase to $z\sim0.3$ [1306.1583].
- **Mid-IR Scaling Laws:** Matched GAMA–WISE catalogs enable empirical determinations of stellar mass vs. $3.4\,\mu$m luminosity, and SFR vs. $12\,\mu$m, $22\,\mu$m luminosity, extending star-forming “main sequence” studies to $z\sim0.5$ [1401.0837].

Model comparison is systematic: GAMA’s completeness and uniformity facilitate robust confrontation of empirical LFs, group/cluster abundances, and LSS topology against semi-analytic predictions (GALFORM, Millennium), with environmental scaling relations, mass function shapes, and group mass proxies tightly constrained [1507.00665, 1409.4681, 1404.6828].

## 6. Scientific Legacy and Data Releases

GAMA’s multi-release model ensures public access to core data products, enhanced catalogues, value-added data management units (DMUs), and user APIs. DR2 delivered $\sim$72,225 objects (spectra, redshifts, photometry, stellar masses, environment, group properties), DR3 added G02, H-ATLAS filler targets, and deeper Herschel follow-up, while DR4 leverages KiDS/VIKING imaging over ~210 deg², unified ProFound photometry, and improved WISE–Herschel fluxes [1711.09139, 1506.08222, 2005.11215].

Data access is via SQL databases, FITS servers, direct HTTP downloads, and Python Astroquery modules, maximizing inter-operability [1506.08222, 1711.09139]. The GAMA consortium maintains continual public engagement and supports integration with ongoing radio, far-IR, and future 4MOST surveys.

## 7. Impact, Recent Science, and Future Prospects

GAMA’s influence is extensive:

- **Strong lens/occulting pair identification:** Blended fibre spectra flagged by autoz yield samples of 104 strong-lens and 71 ideal occulting pairs, nearly doubling SLACS-class lenses, and augmenting dust-extinction studies [1503.04813].
- **Low-mass AGN census:** The depth and multi-diagnostic approach of GAMA DR4 enables the largest optically selected sample of active black holes in $M_\star\lesssim10^{10}~M_\odot$ hosts, probing AGN populations to higher $z$ than SDSS and placing empirical lower bounds on BH seeding and feedback mechanisms [2208.04960].
- **Baryonic census and future HI integration:** GAMA fields are targeted for deep HI mapping with ASKAP DINGO, promising full baryonic mass inventories (stellar+dust+gas) for $\sim10^5$ galaxies at $z<0.3$ [1507.00665].

As a result of its completeness, multiwavelength depth, and meticulous calibration, the GAMA survey is now the benchmark low-redshift resource for empirical validation of galaxy evolution models, hierarchical structure analysis, and multi-phase baryonic studies. Its legacy datasets continue to underpin advances in extragalactic astrophysics, structure formation, and the cosmic baryon cycle.

Source: https://www.emergentmind.com/topics/galaxy-and-mass-assembly-gama-survey