Astronomical instrumentation

Abstract:

As a prerequisite for cosmological studies using adaptive optics techniques, we have begun to identify and characterize faint sources in the vicinity of bright stars at high Galactic latitudes. The initial phase of this work has been a program of Ks imaging conducted with SOFI at the ESO NTT. From observations of 42 southern fields evenly divided between the spring and autumn skies, we have identified 391 additional stars and 1589 galaxies lying at separations Δθ ≤ 60″ from candidate guide stars in the magnitude range 9.0 ≤ R ≤ 12.4. When analyzed as a "discrete deep field" with 131 arcmin² area, our dataset gives galaxy number counts that agree with those derived previously over the range 16 ≤ Ks < 20.5. This consistency indicates that in the aggregate, our fields should be suitable for future statistical studies. We provide our source catalogue as a resource for users of large telescopes in the southern hemisphere.

Abstract:

We present 7-180μm photometry of a sample of hyperluminous infrared galaxies (HyLIGs) obtained with the photometer and camera mounted on the Infrared Space Observatory (ISO). We have used state-of-the-art' radiative transfer models of obscured starbursts and dusty tori to model their broadband spectral energy distributions (SEDs). We find that IRAS F00235+1024, IRAS F14218+3845 and IRAS F15307+3252 require a combination of starburst and AGN components to explain their mid to far-infrared emission, while for TXS0052+471 a dust torus model alone is sufficient. For IRAS F00235+1024 and IRAS F14218+3845 the starburst component is the predominant contributor whereas for IRAS F15307+3252 the dust torus component dominates. The implied star formation rates (SFR) estimated from the starburst infrared luminosities are dM*,all/dt > 1000M⊙yr^-1h50^-2 and are amongst the highest SFRs estimated to date. We also demonstrate that the well-known radio-FIR correlation observed for extragalactic sources extends into both higher radio and infrared power than previously investigated. The relation for HyLIGs has a mean q value of 1.94. The results of this study imply that better sampling of the IR SEDs of HyLIGs may reveal that both AGN and starburst components are required to explain their emission from the NIR to the sub-millimetre.

Abstract:

We present a system for the exchange and handling of cold field masks in LUCIFER, the near infrared camera and spectrograph for the LBT. Inside the LUCIFER cryostat, 10 field-stop and long-slit masks, and 23 multi-slit masks are stored in a stationary and an exchangeable cabinet respectively. With LUCIFER at operating temperature, the exchangeable cabinet with its multi-slit masks can be transferred from the LUCIFER cryostat to an auxiliary cryostat, and a second cabinet harboring the newly made, pre-cooled masks can be transferred back to LUCIFER from. a second auxiliary cryostat. Inside LUCIFER, a robot transports the individual masks from their storage position in the cabinet to the focal plane, and inserts them in a mask mount where they are centered on two pins. The position accuracy of the masks in the focal plane is anticipated to be better than +/-10 mum. A mechanism which locks the masks in their cabinets and releases only the one connected to the transport robot permits mask exchange in arbitrary orientation of the cryostat.

Abstract:

We describe the UK participation in the FMOS project to provide multi-object IR spectroscopy for the Subaru telescope. The UK is working on the design of an OH suppression IR spectrograph, this work comprises the optical design, the opto-mechanical layout, spectrograph thermal environment and cryogenics and detector control system. We give a progress report on the current design work.