Early Science Results
UIST was commissioned during August to December of 2002. ‘First light’ (the first observations of the night sky) was achieved on the 24th September 2002 and UIST was first used by UK astronomers on the 6th December 2002.During the twenty nights that UIST was tested on astronomical sources, data were taken for many different scientific programmes suggested by UK astronomers. The results of some of these programmes are presented here. A couple of observations have been the subject of press releases.
A large team of engineers and scientists at the UK Astronomy Technology Centre and the Joint Astronomy Centre designed, built, tested and commissioned UIST over a period of six years. It is through their efforts and those of the scientists responsible for the astronomical programmes shown that the results produced here were made possible. We would especially like to thank the principal investigators for allowing us to reproduce their results on these pages.
For information about the ongoing use and performance of UIST, please refer to the Joint Astronomy Centre web pages.
Images from the commissioning period
The 'first light' image of the star formation region Messier 17.
The bright Trapezium cluster in Orion shines brilliantly in blue. The red emission is from jets of molecular hydrogen.
The Eagle nebula. An infrared image of the 'pillars of creation' imaged by the Hubble Space Telescope. In this infrared image, the stars are seen through the dusty columns seen in the HST image.
The Episodic Dust Maker, WR140
The thermal imaging capabilities of UIST have been used by Varricatt et al. to further studies of WR140, the prototype of the Colliding Wind Episodic Dust making WC Binary Stars.
WR140 has a WC7 type Wolf-Rayet star and an O4-5 type star, in a highly eccentric orbit (e=0.84) with a period of 7.94 years. Both these stars suffer from mass loss due to stellar wind with wind terminal velocity ~3000 km/s. During epochs close to periastron passage, the winds of both stars collide, get compressed and form dust. The dust is understood to be composed of amorphous carbon. The latest periastron passage of the system was in Feb. 2001.The dust formed at that time expanded and cooled. At the time the UIST observations were made, 28months later, the dust emits mostly in the thermal IR.
The UIST images left were observed using the 0.06arcsec plate scale camera and two narrow band filters centred at 3.6um and 3.99um. With the 0.06arcsec plate scale, the 4um diffraction limit of the telescope (0.26arcsecs) is sampled by four pixels. On nights of best seeing, full advantage is taken of the telescope image quality. The dust is seen like an arc or bar with a tail at both wavelengths. The dust is highly clumped and in the deconvolved images, the dust clumps are well resolved. These thermal images show features in common with those seen earlier in this phase at 2.2um by Monnier et al (2002) using the Keck interferometer. From this comparison, an expansion velocity of 2850km/s has been obtained.
3.6um raw image
3.6um deconvolved image
3.99um raw image
3.99um deconvolved image
Further details of the campaign to monitor WR140 can be found here.
The complex environment of the ultra-compact HII region G25.65-1.05
Todd et al have used the dual capabilities of UIST to explore similarities and differences between high and low mass star formation.
Jets and outflows associated with low mass young stellar objects have been the source of considerable amounts of study. Jets are often highly collimated and are thought to be driven by interactions of the expelled material with disks around the young stars. In contrast, high mass young stellar objects (HMYSOs) are comparatively rare and poorly studied. Outflows that have been observed have appeared different in nature, in particular, poorly collimated. Many of these observations have been made with large beams and low velocity resolution. Thus the question remains whether jets from HMYSOs are fundamentally different from low mass YSOs. Near-infrared observations with higher angular resolution are an excellent tool for probing these embedded objects. The H2 v=1-0 S(1) line at 2.12um is an excellent diagnostic of the shock fronts created by a jet.
The narrow band discovery image for candidate jets from G25.65-1.05.
G25.65-1.05 is one of a number of sources identified by Shepherd and Churchwell (1996) et al as likely to have a bipolar outflow, based on CO maps. Todd et al search for the shocked H2 which is a signature of the impact of outflows on the circumstellar environment by comparing narrow band filter images with continuum images. Knots and features appearing in the H2 ‘finding charts’ are followed up in the spectroscopic mode. In the image right, a number of features appear in H2 only. Once the H2 features are identified, follow-up spectroscopy with either the IFU or long slit allows the excitation to be measured, and the nature of the feature confirmed. From the G25.65 image, one particular feature stands out as having the appearance of a pair of bow shocks. This was followed up with the IFU. The reconstructed IFU image is shown here.
The integral field unit was used with the HK grism, to maximise the wavelength coverage and the number of diagnostic lines detected. The spectrum is shown below. When binned to a spatial resolution of 0.48"x0.48", the HK-band spectra of these objects contain good detections of 12 H2 lines.
The reconstructed H2 v=1-0 S(1) image of the twin bow shocks.
The spectrum of the bow shocks.
The intensity of the lines unaffected by telluric absorption were used to determine the column densities in the excited states of the H2 and from them to measure the temperature change across the bow shocks (assuming LTE). The temperature rises from 1800K to 2800K across the shock front. UKIRT with UIST’s capabilities provides a comprehensive suite of tools for the efficient study of such complex regions as these.
Mapping the Planetary Nebula NGC7027
As a demonstration of the potential for mapping more extended objects with the integral field unit, observations of the well-studied planetary nebula, NGC7027, were carried out. The map right shows the combined frames from six IFUs positions, obtained by scanning the telescope. In the Brackett gamma and H2 v=1-0 S(1) frames we see the morphological differences that have been observed previously (see e.g. Cox et al 2002) . Using the UIST HK grism, moderate resolution spectra of a wealth of emission lines from the ionised and molecular regions are obtained simultaneously with the images.
IFU spectroscopy of NGC1068
The first target for the UIST integral field unit was the well-studied galaxy, NGC1068. Previous observations (e.g. Alloin et al. 2001, Rotaciuc et al 1991) showed a torus of molecular gas emitting in the v=1-0 S(1) line of H2 and extending over several arcseconds, a scale well matched to the 3.3x6arcsec of the UIST IFU. With the field oriented at a position angle of 70ºEast of North, broad H2 emission can be seen over much of the IFU field. A map of the continuum with H2 contours superimposed is shown here. The observations were made with one of the high resolution UIST grisms which gives a velocity resolution of 80kms-1. This velocity resolution, compelled with the 0.5arcsec spatial resolution from the IFU, allows the complex dynamics of the gas near the AGN to be observed in great detail. Galliano and Alloin (2002) modeled ISAAC observations of 1-0 S(1) from this source as being from a combination of a molecular torus and an outflow.
Our data are in good agreement with their observations. Example spectra, obtained by integrating over 0.24 x 0.24arcsec are shown below.
The 3.4mm dust feature in NGC1068.
NGC1068 was also the target for one of the service mode observations carried out during the UIST commissioning. In this case, L band spectroscopy of the nucleus was performed using the long slit mode. NGC1068 is one of the few extragalactic sources in which this feature has been detected. Mason et al required observations of the shape of the 3.4um feature in NGC1068 to compare with previous spectropolarimetry measurements which suggested that the absorption feature was due to substantially larger dust grains that observed in the Galactic ISM (Mason,Wright & Pendleton 2003). The new UIST results show that, at least in this extragalactic nucleus, the feature is the same as in our galaxy (Mason, 2003).
From the first year of use
Willott and McClure.
Bailey et al images of Mars