Table of Contents Messenger No. 131 (March 2008)
Telescopes and Instrumentation
Advanced Calibration Techniques for Astronomical Spectrographs
ESO’s Calibration and Model Support Group is involved in a variety of activities related to the calibration and physical description of instruments, with the objective of supporting the reduction of science data and facilitating operations. Here we describe the construction, optimisation and application to scientific data reduction of physical instrument models. Such models have been implemented for the HST STIS spectrograph and form an integral part of the data reduction pipelines for CRIRES and X-shooter. These models are supported by validated physical data of the instrumental components and calibration reference data.
Laser Guide Star Adaptive Optics without Tip-tilt
Adaptive optics (AO) systems allow a telescope to reach its diffraction limit at near-infrared wavelengths, but a bright natural guide star (NGS) is needed for the wavefront sensing, severely limiting the fraction of the sky over which AO can be used. To some extent this can be overcome with a laser guide star (LGS). While the laser can be pointed anywhere in the sky, one still needs to have a natural star, albeit fainter, reasonably close to correct the image mo-tion (tip-tilt) to which laser guide stars are insensitive. There are in fact many astronomical targets without suitable tip-tilt stars, but for which the enhanced resolution obtained with the Laser Guide Star Facility (LGSF) would still be very beneficial. This article explores what adaptive optics performance one might expect if one dispenses with the tip-tilt star, and in what situations this mode of observing might be needed.
DAZLE on the VLT
We report on the commissioning and first observing run of the VLT visitor instrument DAZLE. DAZLE (Dark Ages ‘Z’ Lyman Explorer), is an innovative near-infrared narrowband imager optimised to detect faint emission lines between the intense hydroxyl (OH) airglow emission lines that dominate the terrestrial night sky in the wavelength range 0.8–1.8 microns. The scientific goal is to detect redshifted Lyman-alpha line emission from hydrogen gas ionised by the young stars in galaxies at redshifts greater than 7.5.
Phase Correction for ALMA: Adaptive Optics in the Submillimetre
Inhomogeneities in the Earth’s atmosphere corrupt the wavefront of incoming submillimetre radiation and, similarly to the seeing at optical wavelengths, this limits the resolution and sensitivity of submillimetre aperture synthesis arrays. ALMA will correct for these wavefront errors by a combination of frequent observations of known nearby point sources (predominately quasars) and by measuring the properties of the atmosphere along the line of sight of each telescope using dedicated 183 GHz radiometers. These techniques are critical for enabling ALMA’s goal of resolution as fine as 0.005 arcseconds.
A Multi-Wavelength Study of the 2003–2006 Outburst of V1647 Orionis
The birth of a star is accompanied by the formation of a circumstellar disc which interacts with the star, but most young stars accrete matter at rates that do not influence the mass of the disc on short timescales. However, in so-called FU Orionis stars, a significant fraction of the total disc mass is accreted onto the central star within a short time. During these FU Orionis events, the light generated by accretion outshines the star by up to 6 magnitudes for a period of several years to decades. The star, V1647 Orionis, underwent such an event. We have used FORS2 and NACO on the VLT and TIMMI2 at the ESO 3.6-m telescope to monitor V1647 Orionis from four months after outburst until the system returned to its pre-outburst brightness level, nearly three years later. Our optical photometry and spectroscopy confirm that V1647 Orionis has indeed undergone an outburst whose characteristics resemble those of the FU Orionis stars.
The VLT-FLAMES Survey of Massive Stars
The VLT-FLAMES Survey of Massive Stars was an ESO Large Programme to understand rotational mixing and stellar mass loss in different metallicity environments, in order to better constrain massive star evolution. We gathered high-quality spectra of over 800 stars in the Galaxy and in the Magellanic Clouds. A sample of this size is unprecedented, enabled by the first high-resolution, wide-field, multi-object spectrograph on an 8-m telescope. We developed spectral analysis techniques that, in combination with non-LTE, line-blanketed model atmospheres, were used to quantitatively characterise every star. The large sample, combined with the theoretical developments, has produced exciting new insights into the evolution of the most massive stars.
Seeking for the Progenitors of Type Ia Supernovae
Type Ia supernovae are thought to be thermonuclear explosions of accreting white dwarfs that reach a critical mass limit. Despite their importance as cosmological distance indicators, the nature of their progenitors has remained controversial. Observations carried out by our team with VLT-UVES led us to the detection of circumstellar material in a normal Type Ia supernova. The expansion velocities, densities and dimensions of the circumstellar envelope indicate that this material was ejected from the system prior to the explosion. The relatively low expansion velocities appear to favour a progenitor system where a white dwarf accretes material from a companion star which is in the red-giant phase at the time of the explosion.
The 2007 Users Feedback Campaign
In a service organisation like ESO, user feedback is a vital component of its success, but receiving feedback on a regular basis is a rather challenging task. This article focuses on the main findings of the Feedback Campaign launched in early 2007, which targeted all Principal Investigators of Service Mode programmes approved over the last five years. Feedback collected from visiting astronomers about operational issues is also presented.
ESO Reflex: A Graphical Workflow Engine for Astronomical Data Reduction
ESO Reflex is a software tool that provides a novel approach to astronomical data reduction. The reduction sequence is rendered and controlled as a graphical workflow. Users can follow and interact with the processing in an intuitive manner, without the need for complex scripting. The graphical interface also allows the modification of existing workflows and the creation of new ones. ESO Reflex can invoke standard ESO data reduction recipes in a flexible way. Python scripts, IDL procedures and shell commands can also be easily brought into workflows and a variety of visualisation and display options, including custom product inspection and validation steps, are available. ESO Reflex was developed in the context of the Sampo project, a three-year effort led by ESO and conducted by a software development team from Finland as an in-kind contribution to joining ESO. It is planned that the software will be released to the community in late 2008.
News from the ESO Science Archive Facility
The latest developments of the ESO archive are presented. Information is provided to the astronomical community on new data releases, services and policies.
ALMA Science: the ESO-Garching Astronomers View
At the Garching Science Day 2007, proposals for observations with ALMA were presented. A comparison is presented with the ALMA Design Reference Science Plan. The comparison shows that ALMA can be exploited by the wider community for a variety of different science projects, many of which are beyond the expectations of the current community of millimetre astronomers.
News from the ALMA Test Facility
Report on the 2007 ESO Fellowship Symposium
The third ESO Fellowship Symposium took place in Santiago from 12–14 November 2007. These symposia, held every two years, bring together ESO Fellows from Chile and Germany for several days of scientific discussion and camaraderie. This year’s symposium was framed by an earthquake and visits to the ESO observatories.
Report on the ESO Chile Science Days
Science Days in Santiago are an annual gathering of ESO’s geographically dispersed team in Chile to learn more about each other’s research, to celebrate scientific achievements of the past year and to encourage new collaborations.
Astronomical Observatories and the Republic of Chile Pave the Way for Future Projects
Report on the ELSA School on the Science of Gaia
Fellows at ESO
New Staff at ESO
Announcement of ESO Large Programmes on the Gran Telescopio Canarias
Announcement of the ASTRONET Infrastructure Roadmap Symposium: An Opportunity to Contribute to the European Astrophysical Strategy for the Next 20 Years
Announcement of the MPA/ESO/MPE/USM 2008 Joint Astronomy Conference on Chemical Evolution of Dwarf Galaxies and Stellar Clusters
Announcement of the Joint ESO/INAF-Arcetri Workshop on Future Ground-based Solar System Research: Synergies with Space Probes and Space Telescopes
Annual Index 2007 (Nos. 127–130)