The ALHAMBRA survey: Estimation of the clustering signal encoded in the cosmic variance^⋆

¹ Centro de Estudios de Física del Cosmos de Aragón, Plaza San Juan 1, 44001 Teruel, Spain
e-mail: clsj@cefca.es
² Observatori Astronòmic, Universitat de València, C/ Catedràtic José Beltrán 2, 46980 Paterna, Spain
³ Instituto de Física de Cantabria (CSIC-UC), 39005 Santander, Spain
⁴ Unidad Asociada Observatorio Astronómico (IFCA-UV), 46980 Paterna, Spain
⁵ Departament d’Astronomia i Astrofísica, Universitat de València, 46100 Burjassot, Spain
⁶ IAA-CSIC, Glorieta de la Astronomía s/n, 18008 Granada, Spain
⁷ GEPI, Observatoire de Paris, CNRS, Université Paris Diderot, 61 avenue de l’Observatoire, 75014 Paris, France
⁸ Instituto de Astronomía, Geofísica e Ciéncias Atmosféricas, Universidade de São Paulo, 05508-090 São Paulo, Brazil
⁹ Instituto de Astrofísica de Canarias, Vía Láctea s/n, 38200 La Laguna, Tenerife, Spain
¹⁰ Departamento de Astrofísica, Facultad de Física, Universidad de La Laguna, 38206 La Laguna, Spain
¹¹ Observatório Nacional-MCT, Rua José Cristino 77, CEP 20921-400, Rio de Janeiro - RJ, Brazil
¹² Department of Theoretical Physics, University of the Basque Country UPV/EHU, 48080 Bilbao, Spain
¹³ IKERBASQUE, Basque Foundation for Science, 48013 Bilbao, Spain
¹⁴ Departamento de Física Atómica, Molecular y Nuclear, Facultad de Física, Universidad de Sevilla, 41012 Sevilla, Spain
¹⁵ Institut de Ciències de l’Espai (IEEC-CSIC), Facultat de Ciències, Campus UAB, 08193 Bellaterra, Spain
¹⁶ Departamento de Astronomía, Pontificia Universidad Católica. 782-0436 Santiago, Chile
¹⁷ Instituto de Física Teórica, UAM/CSIC, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain
¹⁸ Campus of International Excellence UAM+CSIC, Cantoblanco, 28049 Madrid, Spain

Received: 12 June 2015
Accepted: 1 August 2015

Abstract

Aims. The relative cosmic variance (σ_v) is a fundamental source of uncertainty in pencil-beam surveys and, as a particular case of count-in-cell statistics, can be used to estimate the bias between galaxies and their underlying dark-matter distribution. Our goal is to test the significance of the clustering information encoded in the σ_v measured in the ALHAMBRA survey.

Methods. We measure the cosmic variance of several galaxy populations selected with B-band luminosity at 0.35 ≤ z< 1.05 as the intrinsic dispersion in the number density distribution derived from the 48 ALHAMBRA subfields. We compare the observational σ_v with the cosmic variance of the dark matter expected from the theory, σ_v,dm. This provides an estimation of the galaxy bias b.

Results. The galaxy bias from the cosmic variance is in excellent agreement with the bias estimated by two-point correlation function analysis in ALHAMBRA. This holds for different redshift bins, for red and blue subsamples, and for several B-band luminosity selections. We find that b increases with the B-band luminosity and the redshift, as expected from previous work. Moreover, red galaxies have a larger bias than blue galaxies, with a relative bias of b_rel = 1.4 ± 0.2.

Conclusions. Our results demonstrate that the cosmic variance measured in ALHAMBRA is due to the clustering of galaxies and can be used to characterise the σ_v affecting pencil-beam surveys. In addition, it can also be used to estimate the galaxy bias b from a method independent of correlation functions.