Carlos Dominguez-Tagle

Characterization of the scientific grade Hawaii detector for LIRIS

The instrument LIRIS is a near IR spectrograph to be installed at the WHT telescope. Currently it is being assembled at the Instituto de Astrofisica de Canarias. The instrument will have a Hawaii 1Kx1K array as the detector. Here we report the laboratory characterization of the scientific grade unit. We give the relevant parameters such as linearity range, gain and readout noise. These results confirm that the science grade detector will fulfil the astronomical requirements for making LIRIS a front line IR instrument. We also discuss some peculiar effects which need to be taken into account in order to guarantee a correct astronomical performance. Among these effects we consider: variation of the dark signal with integration time, cross-talk, and persistance. We also discuss the variation of the bias level with detector temperature and the need to establish an extremely stable control of the temperature.

LIRIS (long-slit intermediate-resolution infrared spectrograph): project status

LIRIS is a near-IR intermediate resolution spectrograph with added capabilities for multi-object, imaging, coronography, and polarimetry. This instrument is now being constructed at the IAC, and upon complexion will be installed on the 4.2m William Herschel Telescope at the Observatorio del Roque de Los Muchachos. The optical system uses lenses and is based on a classical collimator/camera design. Grisms are used as the dispersion elements. The plate scale matches the median seeing at the ORM. The detector is a Hawaii 1024 X 1024 HgCdTe array operating at 60K.

High-resolution telescope encoder

We describe a speckle-based, telescope-position encoder that overcomes the need the ruled scales and gratings. Using the natural surface markings to produce a speckle pattern, the system is noncontacting and simply aligned. Imaging with a CCD and computing displacements with binary correlation, sub-pixel resolution can be achieved by parabolic approximation. Results of test on the 2-meter telescope at San Pedro Martir are presented.

Commissioning tests of an Integral Field Unit (IFU) at GREGOR solar telescope

We present the commissioning of an IFU based on image-slicers and a 2D-Field-of-View Scanning System (FoV-SS) for the GREGOR Infrared Spectrograph (GRIS). The prototype of the image-slicer has eight slices of 1.8 mm x 0.1 mm in Zerodur, covering an area of 20 arcsec2. The FoV-SS, equipped with three Degrees of Freedom (DoF), allows to scan a region of 1 arcmin2, feeding the image-slicer with different portions of the field of view. A batch of tests was done during the Assembly, Integration and Verification (AIV) at GREGOR telescope.

LIRIS (Long-slit Intermediate Resolution Infrared Spectrograph): Assembly Integration and verification

LIRIS is a near-infrared (0.9 - 2.4 microns) intermediate resolution spectrograph (R = 1000-3000) conceived as a common user instrument for the (WHT) at the Observatorio del Roque de los Muchachos (ORM) La Palma. LIRIS is now being assembled, integrated and virified at the Instituto Astrofisico de Canarias (IAC). LIRIS will have imaging, long-slit and multi-object spectroscopy working modes. Coronography and polarimetry capabilities will eventually be added. Image capability will allow easy target acquisition.

Molecular Hydrogen Around Post-AGB Stars

Near-infrared spectroscopy was conducted to search for molecular material around 40 post-AGB stars. We present the detection of molecular emission lines of H2, 1-0S(1) at 2.122 μm and 2-1S(1) at 2.248 μm in 11 of the post-AGB observed. In addition, Brγ lines at 2.166 μm also were detected in these objects. To investigate the excitation mechanism of molecular hydrogen, we have calculated the H2 1-0S(1)/2-1S(1) ratio and vibrational temperature. Here we present the first results of a study to investigate the relation between the excitation mechanism of H2 and the morphology / evolutionary stage for a sample of 11 post-AGB candidates that exhibit H2 emission.

LIRIS (Long-Slit Intermediate Resolution Infrared Spectrograph)

LIRIS is a near-infrared (0.9–2.4 microns) intermediate resolution spectrograph (R = 1000 – 8000) with added capabilities for multi-object, imaging, coronography, and polarimetry. This instrument is now being constructed at the IAC, and upon complexion will be installed on the 4.2 m William Herschel Telescope (WHT) at the Observatorio del Roque de Los Muchachos (ORM, La Palma).