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July 2011
Subject: Kick-off for the MEGARA instrument

On July 12 at the GRANTECAN offices in Breña Baja the kick-off meeting for the MEGARA instrument was held, marking the start of the design and construction of a new common-user instrument for the GTC.

MEGARA will be one of the third-generation instruments for the telescope and is led by Dr Armando Gil de Paz from the Universidad Complutense de Madrid. The instrument will combine the very large light gathering power of the telescope with the massive multiplexing capability of the instrument. This combination will open up new and important scientific opportunities. The science team that has defined the capabilities of the instrument foresees the use of MEGARA for a wide range of projects, such as the detailed study of the velocities and chemical composition of nearby galaxies and of the stars and stellar groups within them, studies of the kinematics of Planetary Nebulae, dark matter in dwarf elliptical galaxies, and the study of star formation in intermediate-redshift galaxies as well as studies of the integrated light of clusters of galaxies at very high redshifts.

The instrument will consist of an integral-field fibre unit with two bundles (SCB & LCB) covering the central part of the available field. The perimeter of the field will be filled with a network of fibres that each can be positioned on a specific object. The fibre unit will be mounted in the folded-Cassegrain focal station. The fibres will then translate the light to a dedicated spectrograph that will sit close to one of the Nasmyth platforms. The spectrograph will cover spectral resolutions from R ∼ 6000 to 25000 in the optical wavelength range.

Although the kick-off meeting marks the formal start of the project, it is worth emphasizing that the MEGARA team have already invested a very large amount of time in preparing for this project, which gives MEGARA a flying start and an excellent outlook for the future.

A detail of the MEGARA conceptual design, on the left showing the focal plane layout the with central fibre integral field unit and the robot-driven grid of fibre bundles. On the right is shown how the fibre unit will be attached to the folded Cassegrain acquisition and guiding unit.

Summary of Features

MEGARA (Multi-Espectrógrafo en GTC de Alta Resolución para Astronomía) is an optical Integral-Field Unit (IFU) and Multi-Object Spectrograph (MOS) designed for the GTC 10.4m telescope in La Palma. The MEGARA IFU mode will offer two different bundles, one covering 14 arcsec x 12 arcsec with a spaxel size of 0.685 arcsec (Large Compact Bundle; LCB, which makes use of 100μm-core optical fibers) and another one covering 10 arcsec x 8 arcsec with a spaxel size of 0.480 arcsec (Small Compact Bundle; SCB, with 70μm-core fibers). The MEGARA MOS will allow observing up to 100 objects in a region of 3.5 arcmin x 3.5 arcmin around the two IFU bundles. Eight of these bundles will be devoted to the determination of the sky during the observation with the LCB IFU. Both the LCB IFU and MOS capabilities of MEGARA will provide intermediate-to-high spectral resolutions (R~6,000, 11,000 and 19,000). When the SCB is used the resolving powers provided by MEGARA are R=8,100, 14,400 and 24,700. In the table below we provide a summary of the characteristics of the three MEGARA modes (LCB, SCB and MOS) and the corresponding spectral resolutions yield for each set of VPHs.

Details of the design and available resolutions are subject to change as the instrument design evolves.

The scientific interests of the MEGARA Science Team can be grouped in two categories:

• 1. the study of Galactic and extragalactic nebulae.
• 2. the study of (or close to) point-sources with intermediate-to-high surface densities.

Among the former their interests include the study of nearby galaxies and Planetary Nebulae and among the latter Galactic open stellar clusters, stellar populations in Local Group galaxies, GC systems in nearby galaxies, intermediate-redshift dwarf and starburst galaxies, and high-redshift galaxy clusters are the main subject of their research activities.

Support Astronomer in charge of MEGARA in GTC

• (Contact person)

More Information:

• URL: http://guaix.fis.ucm.es/megara/index.html

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