Revealing the Secrets of Galaxies – Second CALIFA Data Release

October 01, 2014

Today, the second large data release of the CALIFA-Survey has been published to the astronomical community and the public. It contains an unprecedented amount of data on 200 galaxies in the local universe allowing astronomers to study in detail numerous galaxy properties regarding their composition, kinematics, formation history and evolution.

The Calar Alto Legacy Integral Field Area survey (CALIFA) is one of the largest surveys of galaxies which is based on an observing technique called "Integral Field Spectroscopy" (IFS). Already a single spectrum of an astronomical object provides important data beyond pure imaging because the light from the source is split into its wavelength-dependent components and shows characteristic signatures related to physical, chemical and dynamical properties. However, using the PMAS Spectrograph at Calar Alto Observatory, the team of the CALIFA Survey is even able to collect 2000 individual spectra for each galaxy which are covering the whole surface of each object.

The 2^nd CALIFA data release now provides unique data on a representative sample of 200 galaxies in the local Universe. These spectra allow studies of the stellar content, ages, star formation history, as well as gas and dust properties. However, beyond spectral diagnostics the CALIFA data-cubes allow to study the spatial distribution of all these properties. Moreover, as a unique feature of imaging spectroscopy, the kinematic properties, i.e. motions of the stars and gas over the whole face of a galaxy, enable the inference of the structure of the galaxy, the formation history, and even the presence of dark matter.

Compared to the 1^st data release in 2012 this 2^nd release presents a much improved preparation of the material. Data is provided with two spectral setups (in low and high resolution) and for each galaxy the data cube contains about 2000 individual spectra. In total this adds up to about 800,000 spectra released in DR2. The data is freely available for anyone interested.

Figure 1: CALIFA data example: Top row: Poststamp images of five galaxies. Bottom row: Colour coded gas velocity maps of the same galaxies based on CALIFA IFS data. — **Figure 1:** CALIFA data example: Top row: Poststamp images of five galaxies. Bottom row: Colour coded gas velocity maps of the same galaxies based on CALIFA IFS data.

Credit: Top row: SDSS | Bottom row: CALIFA team

**Figure 1:** CALIFA data example: Top row: Poststamp images of five galaxies.
Bottom row: Colour coded gas velocity maps of the same galaxies based on CALIFA IFS data.

Credit: Top row: SDSS | Bottom row: CALIFA team

Important links:

Press Release of Calar Alto Observatory on the Second CALIFA Data release:
http://www.caha.es/an-unprecedented-view-of-two-hundred-galaxies-of-the-
local-universe.html
Webpage of the CALIFA second data release: http://califa.caha.es/DR2/
The data presented in the second data release are described in: http://arxiv.org/abs/1409.8302
Full description of the parent sample of galaxies: http://adsabs.harvard.edu/abs/2014A%26A...569A...1W)
MPIA Press Release on the occasion of the first data release in 2012 with detailed background information about CALIFA, the CALIFA Team and Calar Alto Observatory:
http://www.mpia.de/Public/menu_q2e.php?Aktuelles/PR/2012/PR121031/
PR_121031_en.html