Quantifying cosmic variance

By S. Driver, A. Robotham. 2010

135 citations recorded by the source corpus.

We determine an expression for the cosmic variance of any ‘normal’ galaxy survey based on examination of M*± 1 mag galaxies in the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7) data cube. We find that cosmic variance will depend on a number of factors principally: total survey volume, survey aspect ratio and whether the area surveyed is contiguous or comprising independent sightlines. As a rule of thumb cosmic variance falls below 10 per cent once a volume of 107 h−30.7 Mpc3 is surveyed for a single contiguous region with a 1:1 aspect ratio. Cosmic variance will be lower for higher aspect ratios and/or non-contiguous surveys. Extrapolating outside our test region we infer that cosmic variance in the entire SDSS DR7 main survey region is ∼7 per cent to z < 0.1. The equation obtained from the SDSS DR7 region can be generalized to estimate the cosmic variance for any density measurement determined from normal galaxies (e.g. luminosity densities, stellar mass densities and cosmic star formation rates) within the volume range 103–107 h−30.7 Mpc3. We apply our equation to show that two sightlines are required to ensure that cosmic variance is 6 HST studies currently underway.

Subfields: Astronomy and Astrophysics, Instrumentation, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/69887d140cd89ff9296bc61133b5336a28824b43

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Citations in the corpus

A DIRECT MEASUREMENT OF THE BARYONIC MASS FUNCTION OF GALAXIES AND IMPLICATIONS FOR THE GALACTIC BARYON FRACTION (2012, background): “However, the difference is too large to be explained by counting statistics or cosmic variance (e.g. according to the estimates of Somerville et al. 2004 or Driver & Robotham 2010).”
Galaxy and Mass Assembly (GAMA): survey diagnostics and core data release (2010, methodology): “The k- and e-corrections adopted and the methodology, including the SDSS sample construction, are described in Driver & Robotham (2010), but are not particularly important as we are not exploring trends with z but rather the variance at fixed z.”
Herschel-ATLAS: rapid evolution of dust in galaxies over the last 5 billion years (2010, methodology): “Cos. var. is the cosmic variance estimated using the calculator from Driver & Robotham (2010).”
The Star Formation Rate Density and Dust Attenuation Evolution over 12 Gyr with the VVDS Surveys (2011, methodology): “We decided to use the more conservative values found with the recipe in Driver & Robotham (2010).”