ALHAMBRA-gold catalogue published

2013-06-24 13:46
ALHAMBRA regions

ALHAMBRA regions

As the ALHAMBRA project maps in detail eight deep separate regions of the universe, it is the best available tool to study the recent history of the universe.

This first release of the data, which is called ALHAMBRA-gold, contains one hundred thousand galaxies, twenty thousand stars and one thousand possible active galactic nuclei.

Several researchers of CEFCA have participated in the development of this catalogue, which has been conducted by the Calar Alto Observatory.

The first data of ALHAMBRA survey have been published recently. This is the best catalogue to study the evolution of the cosmos so far. These data have been made publicly available in the article led by the researchers Txitxo Molino and Alberto Benitez of the Instituto de Astrofísica de Andalucía (IAA-CSIC). The evolution of the universe over the last ten billion years could be analyze with unprecedented statistical reliability by examining the data of one hundred thousand galaxies, twenty thousand stars in the galactic halo and one thousand possible active galactic nuclei in eight regions of the sky.

“The great strength of ALHAMBRA, which is the most complete survey so far, lies in the detailed study of eight deep regions of the sky. As we have a representative sample, any conclusions that we could draw may be applied to the entire universe” says Alberto Molino, IAA researcher who led the publication of the data.

Astronomers have currently large area surveys but shallow, or deep samples but grouped in a small region, which does not take into account what is known as cosmic variance, resulting from the fact that the density of the galaxies in the universe is variable.

"In this sense, the ALHAMBRA project has confirmed that the COSMOS mapping, which is widely-used in the cosmological studies, is not representative of how galaxies are distributed in the universe. This is due to the fact that this study limits to an area with over-density of galaxies (in comparison to the mean). This proximity causes galaxies evolve faster, so the evolutionary studies generated with COSMOS have a local scope," says Alberto Molino (IAA-CSIC).

The ALHAMBRA project

The ALHAMBRA project, whose name comes from the acronym for Advanced Large Homogeneous Area Medium Band Redshift Astronomical survey, has twenty filters covering all wavelengths and three infrared filters. This allows determining the energy emitted by the galaxies and the distance of half a million galaxies with unprecedented sample size depth.

This first publication of the data is around a fifth of the total data that ALHAMBRA will supply to the international community. Thus, ALHAMBRA will be not only a reference project in the study of the properties of the galaxies, but will also promote future generations of photometric mappings like J-PAS, which is a project that will extend the work of ALHAMBRA to the whole sky. This project will be conducted in Observatorio Astrofísico de Javalambre with the JST / T250 telescope.

The ALHAMBRA project is led by the Director of Centro de Estudios de Física del Cosmos de Aragón (CEFCA), Dr. Mariano Moles. It involves more than seventy scientists from sixteen different institutions.

“The improvements in the ability to increase the accuracy and reliability of the data and the calibration techniques represent a significant advance in the use of intermediate-narrow filters and support other future projects derived from ALHAMBRA” says Dr. Mariano Moles.

ALHAMBRA has been developed entirely from the Calar Alto Observatory during three hundred and fifty nights using the 3.5 meters telescope between 2005 and 2012. Calar Alto has proved to be a facility with privileged characteristics to perform first-line studies like this. “It is mandatory to acknowledge and recognize the effort and ability of Calar Alto staff. They have made it possible to record the data of ALHAMBRA project in the best possible conditions” highlights Dr. Moles.