Astronomical instrumentation

Abstract:

A search for resonant production of high-mass top-quark pairs is performed on 2.05 fb^-1 of proton-proton collisions at sqrt(s) = 7 TeV collected in 2011 with the ATLAS experiment at the Large Hadron Collider. This analysis of the lepton+jets final state is specifically designed for the particular topology that arises from the decay of highly boosted top quarks. The observed ttbar invariant mass spectrum is found to be compatible with the Standard Model prediction and 95% credibility level upper limits are derived on the ttbar production rate through new massive states. An upper limit of 0.7 pb is set on the production cross section times branching fraction of a narrow 1 TeV resonance. A Kaluza-Klein gluon with a mass smaller than 1.5 TeV is excluded.

Abstract:

The EAGLE and EVE Phase A studies for instruments for the European Extremely Large Telescope (E-ELT) originated from related top-level scientific questions, but employed different (yet complementary) methods to deliver the required observations. We re-examine the motivations for a multi-object spectrograph (MOS) on the E-ELT and present a unified set of requirements for a versatile instrument. Such a MOS would exploit the excellent spatial resolution in the near-infrared envisaged for EAGLE, combined with aspects of the spectral coverage and large multiplex of EVE. We briefly discuss the top-level systems which could satisfy these requirements in a single instrument at one of the Nasmyth foci of the E-ELT.

Abstract:

Fiber Multi Object Spectrograph “FMOS” on Subaru Telescope is capable of configuring 400 fibers on the 30- arcmin diameter field of view at the prime focus for near-infrared (0.9–1.8 μm) spectroscopy, and this instrument has been open as a common-use instrument since May 2010. In this article, an overview of the instrument is given first, and then the typical operational sequence in science observation and a few notable features of the instrument are explained. In (see manuscript) 5, the instrument performance in terms of fiber positioning, auto guiding, and sensitivity to emission lines are highlighted. Recently (since March 2012) a Subaru Strategic Program (SSP) has started with FMOS to conduct a wide-field galaxy survey for a cosmological experiment. Upgrading fiber configuration by using a “metrology camera” has also been under discussion, which will enable to measure the positions of the 400 fibers quickly and shorten the fiber configuration time significantly. We will also report the status of these recent activities.

Abstract:

The Visible Integral-field Replicable Unit Spectrograph (VIRUS) consists of a baseline build of 150 identical spectrographs (arrayed as 75 units, each with a pair of spectrographs) fed by 33,600 fibers, each 1.5 arcsec diameter, deployed over the 22 arcminute field of the upgraded 10 m Hobby-Eberly Telescope (HET). The goal is to deploy 82 units. VIRUS has a fixed bandpass of 350-550 nm and resolving power R~700. VIRUS is the first example of industrial-scale replication applied to optical astronomy and is capable of spectral surveys of large areas of sky. This approach, in which a relatively simple, inexpensive, unit spectrograph is copied in large numbers, offers significant savings of engineering effort, cost, and schedule when compared to traditional instruments. The main motivator for VIRUS is to map the evolution of dark energy for the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) using 0.8M Lyman-α emitting galaxies as tracers. The full VIRUS array is due to be deployed by early 2014 and will provide a powerful new facility instrument for the HET, well suited to the survey niche of the telescope. VIRUS and HET will open up wide-field surveys of the emission-line universe for the first time. We present the production design and current status of VIRUS.