ALHAMBRA-gold data made public: the definitive catalogue to study the evolution of the universe
“What gives ALHAMBRA its power, making it an unbeatable survey up to date, is that it implies the detailed study of eight deep sky areas. This allows us to be sure that we count on a representative sample and, thus, that any conclusion drawn from this can be extrapolated to the universe as a whole”, underlines Alberto Molino, IAA scientist that leaded this first public data release.
Up to now we had surveys covering large areas, but no really deep or, alternatively, very deep samples covering only one and very small zone, what does not take into account the so-called cosmic variance, derived from the fact that the cosmos has regions with very different galaxy densities.
“To this respect, the ALHAMBRA Survey allowed us to confirm that the COSMOS Project, one of the most widely used for cosmological studies, is not representative of galaxy distribution in the universe, because it is restricted to an area that shows an over-density of galaxies, compared to the average; their closeness makes galaxies to evolve faster and, thus, cosmological studies based on COSMOS have a local character”, points out Alberto Molino (IAA-CSIC).
The project ALHAMBRA Survey (Advanced Large, Homogeneous Area Medium Band Redshift Astronomical Survey) relays on a system of twenty filters covering all visible wavelengths, and three more for the infrared, what allows a precise determination of the energy emitted by galaxies and, also, the distance to half a million galaxies with an unprecedented precision for such a large sample.
This first data release contains about one fifth of the total that ALHAMBRA will offer to the international community, making it not only a reference project for the study of galaxy properties, but also a booster for the next generation of photometric surveys such as JPAS (a Spanish-Brasilian project that will extend the work done by ALHAMBRA to cover all the sky).
The ALHAMBRA project is leaded by Mariano Moles (Centre for Studies on the Physics of Cosmos of Aragon), and more than seventy scientists from sixteen institutions from different countries are involved, with a very outstanding Spanish participation. It has been fully developed from Calar Alto Observatory, along three hundred and fifty nights with the 3.5 m telescope, equipped with instruments LAICA and Omega-2000 for visible and infrared light, respectively. Calar Alto has shown its privileged conditions for first-line studies such as this.
An example of the deep images taken at Calar Alto for the ALHAMBRA Survey.
The regions of the ALHAMBRA Survey whose date have been made public: those enlarging the information available from other surveys such as COSMOS or SDSS.