E. Carrasco, A. Gil de Paz, J. Gallego, J. Iglesias-Páramo, R. Cedazo, M. L. García Vargas, X. Arrillaga, J. L. Avilés, A. Bouquin, J. Carbajo, N. Cardiel, M. A. Carrera, A. Castillo Morales, E. Castillo-Domínguez, S. Esteban San Román, D. Ferrusca, P. Gómez-Álvarez, R. Izazaga-Pérez, B. Lefort, J. A. López Orozco, M. Maldonado, I. Martínez Delgado, I. Morales Durán, E. Mújica, R. Ortiz, G. Páez, S. Pascual, A. Pérez-Calpena, P. Picazo, A. Sánchez-Penim, E. Sánchez-Blanco, S. Tulloch, M. Velázquez, J. Vílchez, J. Zamorano, A. Aguerri, D. Barrado, E. Bertone, A. Cava, C. Catalán-Torrecilla, J. Cenarro, M. Chávez, B. Dullo, C. Eliche, Mi. García, J. García-Rojas, J. Guichard, R. González-Delgado, R. Guzmán, A. Herrero, N. Huélamo, D. Hughes, J. Jiménez-Vicente, C. Kehrig, R. Marino, I. Márquez, J. Masegosa, D. Mayya, J. Méndez-Abreu, M. Mollá, C. Muñoz-Tuñón, M. Peimbert, P. Pérez-González, E. Pérez-Montero, S. Roca-Fàbrega, M. Rodríguez, J. M. Rodríguez-Espinosa, L. Rodríguez-Merino, L. Rodríguez-Muñoz, D. Rosa-González, J. Sánchez-Almeida, C. Sánchez Contreras, P. Sánchez-Blázquez, S. Sánchez, A. Sarajedini, S. Silich, S. Simón-Díaz, G. Tenorio-Tagle , E. Terlevich, R. Terlevich, S. Torres-Peimbert, I. Trujillo, Y. Tsamis, O. Vega
MEGARA is the new generation IFU and MOS optical spectrograph built for the 10.4m Gran Telescopio CANARIAS (GTC). The project was developed by a consortium led by UCM (Spain) that also includes INAOE (Mexico), IAA-CSIC (Spain) and UPM (Spain). The instrument arrived to GTC on March 28th 2017 and was successfully integrated and commissioned at the telescope from May to August 2017. During the on-sky commissioning we demonstrated that MEGARA is a powerful and robust instrument that provides on-sky intermediate-to-high spectral resolutions RFWHM ~ 6,000, 12,000 and 20,000 at an unprecedented efficiency for these resolving powers in both its IFU and MOS modes. The IFU covers 12.5 x 11.3 arcsec2 while the MOS mode allows observing up to 92 objects in a region of 3.5 x 3.5 arcmin2. In this paper we describe the instrument main subsystems, including the Folded-Cassegrain unit, the fiber link, the spectrograph, the cryostat, the detector and the control subsystems, and its performance numbers obtained during commissioning where the fulfillment of the instrument requirements is demonstrated.
A. Gil de Paz, E. Carrasco, J. Gallego, J. Iglesias-Páramo, R. Cedazo, M. L. García-Vargas, X. Arrillaga, J. Avilés, A. Bouquin, J. Carbajo, N. Cardiel, M. Carrera, A. Castillo-Morales, E. Castillo-Domínguez, S. Esteban San Román, D. Ferrusca, P. Gómez-Álvarez, R. Izazaga-Pérez, B. Lefort, J. López-Orozco, M. Maldonado, I. Martínez-Delgado, I. Morales-Durán, E. Mujica, G. Páez, S. Pascual, A. Pérez-Calpena, P. Picazo, A. Sánchez-Penim, E. Sánchez-Blanco, S. Tulloch, M. Velázquez, J. Vílchez, J. Zamorano, A. Aguerri, D. Barrado y Navascues, S. Berlanas, E. Bertone, A. Cava, C. Catalán-Torrecilla, J. Cenarro, M. Chávez, B. Dullo, M. García, J. García-Rojas, J. Guichard, R. González-Delgado, R. Guzmán, A. Herrero, N. Huélamo, D. Hughes, J. Jiménez-Vicente, C. Kehrig, R. Marino, I. Márquez, J. Masegosa, D. Mayya, J. Méndez-Abreu, M. Mollá, C. Muñoz-Tuñón, M. Peimbert, P. Pérez-González, E. Pérez-Montero, M. Rodríguez, J. Rodríguez-Espinosa, L. Rodríguez Merino, L. Rodríguez-Muñoz, D. Rosa-González, J. Sánchez-Almeida, C. Sánchez-Contreras, P. Sánchez-Blázquez, S. Sánchez, A. Sarajedini, S. Silich, S. Simón-Díaz, G. Tenorio-Tagle, E. Terlevich, R. Terlevich, S. Torres-Peimbert, I. Trujillo, Y. Tsamis, O. Vega
On June 25th 2017, the new intermediate-resolution optical IFU and MOS of the 10.4-m GTC had its first light. As part of the tests carried out to verify the performance of the instrument in its two modes (IFU and MOS) and 18 spectral setups (identical number of VPHs with resolutions R=6000-20000 from 0.36 to 1 micron) a number of astronomical objects were observed. These observations show that MEGARA@GTC is called to fill a niche of high-throughput, intermediateresolution IFU and MOS observations of extremely-faint narrow-lined objects. Lyman-α absorbers, star-forming dwarfs or even weak absorptions in stellar spectra in our Galaxy or in the Local Group can now be explored to a new level. Thus, the versatility of MEGARA in terms of observing modes and spectral resolution and coverage will allow GTC to go beyond current observational limits in either depth or precision for all these objects. The results to be presented in this talk clearly demonstrate the potential of MEGARA in this regard.
A. Gil de Paz, E. Carrasco, J. Gallego, J. Iglesias-Páramo, R. Cedazo, M. L. García Vargas, X. Arrillaga, J. L. Avilés, N. Cardiel, M. A. Carrera, A. Castillo-Morales, E. Castillo-Domínguez, J. de la Cruz García, S. Esteban San Román, D. Ferrusca, P. Gómez-Álvarez, R. Izazaga-Pérez, B. Lefort, J. A. López-Orozco, M. Maldonado, I. Martínez-Delgado, I. Morales Durán, E. Mujica, G. Páez, S. Pascual, A. Pérez-Calpena, P. Picazo, A. Sánchez-Penim, E. Sánchez-Blanco, S. Tulloch, M. Velázquez, J. Vílchez, J. Zamorano, A. Aguerri, D. Barrado y Naváscues, E. Bertone, A. Cava, J. Cenarro, M. Chávez, M. García, J. García-Rojas, J. Guichard, R. González-Delgado, R. Guzmán, A. Herrero, N. Huélamo, D. Hughes, J. Jiménez-Vicente, C. Kehrig, R. Marino, I. Márquez, J. Masegosa, Y. Mayya, J. Méndez-Abreu, M. Mollá, C. Muñoz-Tuñón, M. Peimbert, P. Pérez-González, E. Pérez Montero, M. Rodríguez, J. Rodríguez-Espinosa, L. Rodríguez-Merino, L. Rodríguez-Muñoz, D. Rosa-González, J. Sánchez-Almeida, C. Sánchez Contreras, P. Sánchez-Blázquez, F. M. Sánchez Moreno, S. Sánchez, A. Sarajedini, S. Silich, S. Simón-Díaz, G. Tenorio-Tagle, E. Terlevich, R. Terlevich, S. Torres-Peimbert, I. Trujillo, Y. Tsamis, O. Vega
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 that is being built by a Consortium led by UCM (Spain) that also includes INAOE (Mexico), IAA-CSIC (Spain), and UPM (Spain). The instrument is currently finishing AIV and will be sent to GTC on November 2016 for its on-sky commissioning on April 2017. The MEGARA IFU fiber bundle (LCB) covers 12.5x11.3 arcsec2 with a spaxel size of 0.62 arcsec while the MEGARA MOS mode allows observing up to 92 objects in a region of 3.5x3.5 arcmin2 around the IFU. The IFU and MOS modes of MEGARA will provide identical intermediate-to-high spectral resolutions (RFWHM~6,000, 12,000 and 18,700, respectively for the low-, mid- and high-resolution Volume Phase Holographic gratings) in the range 3700-9800ÅÅ. An x-y mechanism placed at the pseudo-slit position allows (1) exchanging between the two observing modes and (2) focusing the spectrograph for each VPH setup. The spectrograph is a collimator-camera system that has a total of 11 VPHs simultaneously available (out of the 18 VPHs designed and being built) that are placed in the pupil by means of a wheel and an insertion mechanism. The custom-made cryostat hosts a 4kx4k 15-μm CCD. The unique characteristics of MEGARA in terms of throughput and versatility and the unsurpassed collecting are of GTC make of this instrument the most efficient tool to date to analyze astrophysical objects at intermediate spectral resolutions. In these proceedings we present a summary of the instrument characteristics and the results from the AIV phase. All subsystems have been successfully integrated and the system-level AIV phase is progressing as expected.
MEGARA is the future integral-field and multi-object spectrograph for the GTC 10.4m telescope located in the
Observatorio del Roque de los Muchachos in La Palma. INAOE is a member of the MEGARA Consortium and it is
in charge of the Optics Manufacturing work package. In addition to the manufacturing of 73 elements, the work
package includes the opto-mechanics i.e. the opto-mechanical design, manufacture, tests and integration of the
complete assembly of the main optics composed by the collimator and camera subsystems. MEGARA passed the
Optics Detailed Design Review in May 2013 and will have the Detailed Design Review of the complete instrument
early 2014. Here we describe the detailed design of the collimator and camera barrels. We also present the finite
elements models developed to simulate the behavior of the barrel, sub-cells and other mechanical elements. These
models verify that the expected stress fields and the gravitational displacements on the lenses are compatible with
the optical quality tolerances. The design is finished and ready for fabrication.
MEGARA is the future visible integral-field and multi-object spectrograph for the GTC 10.4-m telescope
located in La Palma. INAOE is a member of the MEGARA Consortium and it is in charge of the Optics
Manufacturing work package. MEGARA passed the Optics Detailed Design Review in May 2013, and the
blanks of the main optics have been already ordered and their manufacturing is in progress. Except for
the optical fibers and microlenses, the complete MEGARA optical system will be manufactured in
Mexico, shared between the workshops of INAOE and CIO. This includes a field lens, a 5-lenses collimator, a
7-lenses camera and a complete set of volume phase holographic gratings with 36 flat windows and 24 prisms,
being all these elements very large and complex. Additionally, the optical tests and the complete assembly of
the camera and collimator subsystems will be carried out in Mexico. Here we describe the current status of the
optics manufacturing process.
We have made high order (32x32 subaperture) Shack-Hartmann wavefront sensor observations of binary stars
with separations of approximately 20 arcseconds using the University of Hawaii 2.2 m telescope. We present
preliminary results of a Slope Detection and Ranging (SLODAR) analysis of the data yielding measurements of
turbulence strength, wind velocity and velocity dispersion as a function of altitude, with approximately 500 m
vertical resolution. The aim of the investigation is to explore the validity of the Taylor frozen flow approximation
and the implications for layer-oriented predictive AO reconstruction algorithms.
We describe the current status of the SLODAR optical turbulence monitors, developed at Durham University, for support
of adaptive optics for astronomy. SLODAR systems have been installed and operated at the Cerro Paranal and Mauna
Kea observatories, and a third will be deployed at the South African Astronomical Observatory in 2008. The instruments
provide real-time measurements of the atmospheric turbulence strength, altitude and velocity. We summarize the
capabilities of the systems and describe recent enhancements. Comparisons of contemporaneous data obtained with
SLODAR, MASS and DIMM monitors at the ESO Paranal site are presented.
We present observations of the high-speed variations of the altitude of the telluric sodium layer. In this experiment we observed the Gemini-North sodium laser guide star from approximately 80 meters
off-axis using the UH-2.2m telescope on Mauna Kea, Hawaii. Observations were made using an electron-multiplying camera at a rate of about 100Hz. The temporal power spectrum of the layer centroid follows a power law between 0.001 and 1Hz and we find that the exponent of the power law (α=-1.8) is similar to that found at lower temporal frequencies from lidar experiments. This data set taken with the lidar results shows that the power spectrum of the sodium layer mean altitude follows a simple power law over 5 orders of magnitude from 10-4.5 Hz to 1Hz. The approach taken in this experiment is difficult due to telescope jitter in any of the three telescopes (Gemini-N, Gemini-N LGS launch telescope, or from the observing UH2.2m) and atmospheric tip/tilt wave front aberrations. We circumvented these problems by analyzing the differential motion between two distinct features that appeared in the sodium layer during that night.
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