Bibcode
López-Sanjuan, C.; Cenarro, A. J.; Hernández-Monteagudo, C.; Varela, J.; Molino, A.; Arnalte-Mur, P.; Ascaso, B.; Castander, F. J.; Fernández-Soto, A.; Huertas-Company, M.; Márquez, I.; Martínez, V. J.; Masegosa, J.; Moles, M.; Pović, M.; Aguerri, J. A. L.; Alfaro, E.; Aparicio-Villegas, T.; Benítez, N.; Broadhurst, T.; Cabrera-Caño, J.; Cepa, J.; Cerviño, M.; Cristóbal-Hornillos, D.; Del Olmo, A.; González Delgado, R. M.; Husillos, C.; Infante, L.; Perea, J.; Prada, F.; Quintana, J. M.
Bibliographical reference
Astronomy and Astrophysics, Volume 564, id.A127, 17 pp.
Advertised on:
4
2014
Journal
Citations
16
Refereed citations
15
Description
Aims: Our goal is to estimate empirically the cosmic variance
that affects merger fraction studies based on close pairs for the first
time. Methods: We compute the merger fraction from photometric
redshift close pairs with 10 h-1 kpc ≤ rp ≤
50 h-1 kpc and Δv ≤ 500 km s-1 and
measure it in the 48 sub-fields of the ALHAMBRA survey. We study the
distribution of the measured merger fractions that follow a log-normal
function and estimate the cosmic variance σv as the
intrinsic dispersion of the observed distribution. We develop a maximum
likelihood estimator to measure a reliable σv and avoid
the dispersion due to the observational errors (including the Poisson
shot noise term). Results: The cosmic variance
σv of the merger fraction depends mainly on (i) the
number density of the populations under study for both the principal
(n1) and the companion (n2) galaxy in the close
pair and (ii) the probed cosmic volume Vc. We do not find a
significant dependence on either the search radius used to define close
companions, the redshift, or the physical selection (luminosity or
stellar mass) of the samples. Conclusions: We have estimated the
cosmic variance that affects the measurement of the merger fraction by
close pairs from observations. We provide a parametrisation of the
cosmic variance with n1, n2, and Vc,
σv ∝
n1-0.54Vc-0.48
(n_2/n_1)-0.37 . Thanks to this prescription, future merger
fraction studies based on close pairs could properly account for the
cosmic variance on their results.
Based on observations collected at the German-Spanish Astronomical
Center, Calar Alto, jointly operated by the Max-Planck-Institut für
Astronomie (MPIA) at Heidelberg and the Instituto de Astrofísica
de Andalucía (IAA-CSIC).Appendix is available in electronic form
at http://www.aanda.org
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