Prof Gavin Dalton

Abstract:

We present near-infrared spectroscopic observations of star-forming galaxies at z ∼ 1.4 with FMOS on the Subaru Telescope. We observed K-band selected galaxies in the SXDS/UDS fields with K ≤ 23.9mag, 1.2 ≤ zph ≤ 1.6,M ≥ 109.5M, and expected F(Hα) ≥ 10-16 erg s-1cm-2; 71 objects in the sample have significant detections of H?. For these objects, excluding possible AGNs, identified from the BPT diagram, gas-phase metallicities were obtained from the [N II] /Hα line ratio. The sample is split into three stellar-mass bins, and the spectra are stacked in each stellar-mass bin. The mass-metallicity relation obtained at z ∼ 1.4 is located between those at z ∼ 0.8 and z ∼ 2.2. We constrain the intrinsic scatter to be ∼0.1 dex, or larger in the mass-metallicity relation at z ∼ 1.4; the scatter may be larger at higher redshifts. We found trends that the deviation from the mass-metallicity relation depends on the SFR (Star-formation rate) and the half light radius: Galaxies with higher SFR and larger half light radii show lower metallicities at a given stellar mass. One possible scenario for the trends is the infall of pristine gas accreted from IGM, or through merger events. Our data points show larger scatter than the fundamental metallicity relation (FMR) at z ∼ 0.1, and the averagemetallicities slightly deviate fromthe FMR. The compilation of themass- metallicity relations at z ∼ 3 to z ∼ 0.1 shows that they evolve smoothly from z ∼ 3 to z ∼ 0 without changing the shape so much, except for the massive part at z ∼ 0. © 2012 Astronomical Society of Japan.

Abstract:

The 4MOST consortium is currently halfway through a Conceptual Design study for ESO with the aim to develop a wide-field (>3 square degree, goal >5 square degree), high-multiplex (>1500 fibres, goal 3000 fibres) spectroscopic survey facility for an ESO 4m-class telescope (VISTA). 4MOST will run permanently on the telescope to perform a 5 year public survey yielding more than 20 million spectra at resolution R∼5000 (λ=390-1000 nm) and more than 2 million spectra at R∼20,000 (395-456.5 nm & 587-673 nm). The 4MOST design is especially intended to complement three key all-sky, space-based observatories of prime European interest: Gaia, eROSITA and Euclid. Initial design and performance estimates for the wide-field corrector concepts are presented. Two fibre positioner concepts are being considered for 4MOST. The first one is a Phi-Theta system similar to ones used on existing and planned facilities. The second one is a new R-Theta concept with large patrol area. Both positioner concepts effectively address the issues of fibre focus and pupil pointing. The 4MOST spectrographs are fixed configuration two-arm spectrographs, with dedicated spectrographs for the high- and low-resolution fibres. A full facility simulator is being developed to guide trade-off decisions regarding the optimal field-of-view, number of fibres needed, and the relative fraction of high-to-low resolution fibres. The simulator takes mock catalogues with template spectra from Design Reference Surveys as starting point, calculates the output spectra based on a throughput simulator, assigns targets to fibres based on the capabilities of the fibre positioner designs, and calculates the required survey time by tiling the fields on the sky. The 4MOST consortium aims to deliver the full 4MOST facility by the end of 2018 and start delivering high-level data products for both consortium and ESO community targets a year later with yearly increments. © 2012 SPIE.

Abstract:

The Polar Large Telescope (PLT) aims at performing a new generation of astronomical Infrared Synoptic Survey from Antarctica (ISSA). It would carry out for the first time large scale periodic imaging surveys at ˜ 0.3 arcsec angular resolution in the short thermal infrared (2-5 micron) range benefiting from the extremely dry, cold, and stable polar atmosphere. The PLT consists of a 2.5 m class telescope equipped with a 250-Mpixel infrared camera. The survey would produce diffraction limited images at 2 micron covering a total of ˜ 5000 square degrees, explore the time domain from seconds to years down to mab =25.5 in Kd, generate alerts of transients and react quickly to alerts from other ground based or space borne facilities.