Cosmic Variance in the Great Observatories Origins Deep Survey

By R. Somerville, Kyoung-soo Lee, H. Ferguson, J. Gardner, L. A. Moustakas, M. Giavalisco. 2003

261 citations recorded by the source corpus.

Cosmic variance is the uncertainty in observational estimates of the volume density of extragalactic objects such as galaxies or quasars arising from the underlying large-scale density fluctuations. This is often a significant source of uncertainty, especially in deep galaxy surveys, which tend to cover relatively small areas. We present estimates of the relative cosmic variance for one-point statistics (i.e., number densities) for typical scales and volumes sampled by the Great Observatories Origins Deep Survey (GOODS). We use two approaches: (1) For objects with a known two-point correlation function that is well approximated by a power law, one can use the standard analytic formalism to calculate the cosmic variance (in excess of shot noise). We use this approach to estimate the cosmic variance for several populations that are being studied in the GOODS program (extremely red objects [EROs] at z ~ 1 and Lyman break galaxies [LBGs] at z ~ 3 and z ~ 4) using clustering information for similar populations in the literature. (2) For populations with unknown clustering, one can use predictions from cold dark matter theory to obtain a rough estimate of the variance as a function of number density. We present a convenient plot that allows one to use this approach to read off the cosmic variance for a population with a known mean redshift and estimated number density. We conclude that for the volumes sampled by GOODS, cosmic variance is a significant source of uncertainty for strongly clustered objects (~40%-60% for EROs) and less serious for less clustered objects (~10%-20% for LBGs).

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/a376cfb080e979d45505e91bb6ec5b318ed21823

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Citations in the corpus

Reionization and Galaxy Evolution Probed by z = 7 Lyα Emitters (2007, methodology): “…dark matter halo variances (z, σDM) = (5.7, 0.063), (6.6, 0.053) and (7.0, 0.044) obtained using analytic cold dark matter model (Sheth & Tormen 1999; Somerville et al. 2004) and our SDF survey volumes to b = σv/σDM, we calculate the geometric mean of cosmic variance at z = 5.7–7, which is 8.4–27%.”
The SWIRE-VVDS-CFHTLS surveys: stellar mass assembly over the last 10 Gyr. Evidence for a major build up of the red sequence between z = 2 and z = 1 (2007, methodology): “Following the recipes described by Somerville et al. (2004), we estimate the cosmic variance from large scale structure fluctuations in the ΛCDM paradigm.”
The Hubble Ultra Deep Field (2003, background): “The rela- tive cosmic error, σv, is the root variance corrected for Poisson noise, divided by the average number density (see Somerville et al. 2004, hereafter S04, equation 1).”
Cosmic Variance and Its Effect on the Luminosity Function Determination in Deep High-z Surveys (2007, methodology): “[3]; see alsoNewman & Davis 2002) to obtain the dark matter cosmic variance 2DM. 4.”
Infrared Luminosity Functions from the Chandra Deep Field-South: The Spitzer View on the History of Dusty Star Formation at 0 ≲ z ≲ 1* (2005, background): “This originates from an overdensity characteristic of the CDFS near this redshift (e.g., Wolf et al. 2004) and it is likely related to cosmic variance and largescale structure effects (Somerville et al. 2004).”
UV Luminosity Functions at z~4, 5, and 6 from the Hubble Ultra Deep Field and Other Deep Hubble Space Telescope ACS Fields: Evolution and Star Formation History (2007, methodology): “Since these distances cover ∼ 40 − 100 correlation lengths, typical field-to-field variations of ∼ 16−35% are found in the surface density of dropouts (Somerville et al. 2004; Bunker et al. 2004; B06; Beckwith et al. 2006).”
Galaxies at z ~ 6: The UV Luminosity Function and Luminosity Density from 506 HUDF, HUDF Parallel ACS Field, and GOODS i-Dropouts (2005, background): “An additional ∼ 20%/ √ 2 ∼ 14% uncertainty in φ∗ results from the expected field-to-field variations in the i-dropout surface densities over the two GOODS fields (Somerville et al. 2004; §3.6).”
A Comprehensive Study of Galaxies at z ∼ 9–16 Found in the Early JWST Data: Ultraviolet Luminosity Functions and Cosmic Star Formation History at the Pre-reionization Epoch (2022, methodology): “We estimate the cosmic variance in the number densities using the bias values of the z∼ 7 galaxies obtained in Harikane et al. (2016), following the procedures in Somerville et al. (2004).”
WHAT TURNS GALAXIES OFF? THE DIFFERENT MORPHOLOGIES OF STAR-FORMING AND QUIESCENT GALAXIES SINCE z ∼ 2 FROM CANDELS (2011, methodology): “Diamonds with error bars denote the number of galaxies with stellar masses in excess of 3×1010M⊙ in the UDS, with error bars denoting the expected degree of sample variance in that bin following the method of Somerville et al. (2004).”
Characterizing the Cluster Lens Population (2005, methodology): “Even for the relatively coarse redshift bins we use here ∆z ∼ 1.0, cosmic variance for such a small field can be as large as ∼ 50% (Somerville et al. 2004).”
Lyα blobs as an observational signature of cold accretion streams into galaxies (2009, methodology): “The error bars on the data points were obtained from the relation σ2 = b2σ2M (Vs) + σ 2 P , where σP denotes the Poisson error and b2σ2M (Vs) denotes the cosmic variance for a bias factor b = b(Mhalo, z), which is in turn calculated following Somerville et al. (2004).”
COMPLETING THE CENSUS OF Lyα EMITTERS AT THE REIONIZATION EPOCH (2011, methodology): “Based on Somerville et al. (2004), we evaluated the cosmic variance of our LAE samples.”
The star formation rate of the Universe at z~ 6 from the Hubble Ultra-Deep Field (2004, methodology): “From Somerville et al. (2004) we estimate that the cosmic variance for the UDF is 40 per cent, assuming the z = 6 LBGs are clustered in the same way as the z = 3 LBGs and assuming a volume derived by scaling our UDF area with our wider-area GOODS data (with an effective volume of 1.8 × 105 h−370…”
The Great Observatories Origins Deep Survey: Initial Results from Optical and Near-Infrared Imaging (2003, methodology): “A Letter by Somerville et al. (2004) presents computations of the expected “cosmic variance” for various source populations based on halo statistics in cold dark matter models consistent with theWilkinson Microwave Anistropy Probe cosmological parameters (Spergel et al. 2003).”
The star formation history of K-selected galaxies (2008, unknown): “2 in Somerville et al. (2004).”
SIZES AND SURFACE BRIGHTNESS PROFILES OF QUIESCENT GALAXIES AT z ∼ 2 (2011, result): “We note that our measured number densities are approximately a factor 2 smaller than those in Brammer et al. (2011), consistent with expectations from field-to-field variations (Somerville et al. 2004).”
Lyα-EMITTING GALAXIES AT z = 2.1 IN ECDF-S: BUILDING BLOCKS OF TYPICAL PRESENT-DAY GALAXIES? (2009, background): “…for incompleteness) of 3.1 ± 0.9 × 10−3 Mpc−3 at z ' 2.1, for which the errors are calculated as the sum in quadrature of the uncertainties in the incompleteness factors, the sample variance due to large scale structure for this volume (Somerville et al. 2004) equal to ∼25%, and the Poisson error.”