0000000000390768
AUTHOR
M. Pović
High redshift galaxies in the ALHAMBRA survey
International audience
The ALHAMBRA survey: An empirical estimation of the cosmic variance for merger fraction studies based on close pairs
[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 ALHAMBRA survey: Accurate merger fractions by PDF analysis of photometric close pairs
Our goal is to develop and test a novel methodology to compute accurate close pair fractions with photometric redshifts. We improve the current methodologies to estimate the merger fraction f_m from photometric redshifts by (i) using the full probability distribution functions (PDFs) of the sources in redshift space, (ii) including the variation in the luminosity of the sources with z in both the selection of the samples and in the luminosity ratio constrain, and (iii) splitting individual PDFs into red and blue spectral templates to deal robustly with colour selections. We test the performance of our new methodology with the PDFs provided by the ALHAMBRA photometric survey. The merger frac…