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Home > Public Information > ING Annual Reports > 2002-2003 > Chapter 1. Scientific Highlights |
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Chapter 1
SCIENTIFIC HIGHLIGHTS
NAOMI FOCUSES ON A NEAR EARTH ASTEROID
WHT+NAOMI
The adaptive optics system NAOMI on the WHT was used to
take a remarkable image of a Near-Earth Asteroid (NEA). On the night
of August 17 to 18 NAOMI imaged the NEA 2002 NY40 just before its closest
approach to the Earth. These are the first images of a NEA obtained
with an Adaptive Optics system.
The asteroid was observed when it was only 750,000 kilometres
away, twice the distance to the Moon, and moving rapidly across the
sky at 65,000 kilometres per hour. Despite the technical difficulties
this rapid movement caused, the astronomers using the WHT obtained very
high quality images in the near-infrared with a resolution of 0.11 arcseconds.
This resolution is close to the theoretical limit of the telescope,
and sets an upper limit of 400 meters to the size of the asteroid.
Near-Earth asteroids are those that periodically approach
or cross the orbit of our planet, and there is a very small probability
that one could collide with the Earth. Measuring the size of asteroids
helps astronomers understand their nature and how they were formed,
as well as the potential threat they pose. Variations in the brightness
of 2002 NY40 suggest that it is highly elongated and is tumbling.
Further monitoring of these variations will tell the astronomers whether
the asteroid was viewed end-on or side-on, thus allowing them to determine
the size and shape more precisely.
NAOMI was built by a team from the University of Durham
and the UK Astronomy Technology Centre in Edinburgh. In good conditions,
it can deliver images as sharp as those from the Hubble Space Telescope.
Figure 1. H-band (1.63 microns)
NAOMI image of asteroid 2002 NY40 taken on the night of August 17,
2002. [ JPEG | TIFF
] |
Figure 2. An impression of what
a quiescent stellar black hole may look like. Gas is fed from the
companion star into an accretion disc around the black hole. Some X-rays
are produced as the hot gas falls into the black hole but these are
much fainter than when an outburst occurs. In these quiescent black
hole binary stars the companion star is actually brighter than the
gas falling into the black hole. During the flares the X-rays fall upon
the accretion disc and cause it to light up and become much brighter.
[ JPEG | TIFF ] |
Figure 3. An image of the s Ori
region. The multiple star s Ori, which is visible with the naked
eye, is at the centre. A box indicates the position of the planet candidate,
which is only 8.7 arcminutes from the star. The image was taken from
the Digital Sky Survey and has a size of 23 × 22 square
arcminutes. The inset shows the infrared image obtained using INGRID at
the William Herschel Telescope. [ JPEG
| TIFF ] |
Figure 4. Observed versus literature
redshifts. Symbol sizes correspond to χ2 smaller symbols
indicate a poorer fit. QSO 0127+059 has an incorrect literature redshift
of 2.30; follow-up spectroscopy has yielded z=3.04, moving the point
to the position shown in grey. The dashed line shows the 1:1 correlation.
[ JPEG | TIFF ] |
Figure 5. TiO band at 7069.2 Å,
observed during the outburst of r Cas on 2000 July 19 in the top
panel, best fitted (dotted line) for a model atmosphere with Teff
= 3750 K and log g=0 in the bottom panel. The spectrum of 2002 January
with higher Teff does not show the TiO bands. A microturbulence
velocity of 11 kms-1 and macrobroadening of 21 kms-1
are required to broaden the synthetic spectrum (dotted line) of
r Cas to the observed shape of the TiO band. The best fit yields a radial
velocity of -82kms-1, or an expansion velocity of 35 kms-1.
The strongest TiO lines for the synthesis, with log g values greater than
-1, are marked (vertical lines). The synthetic spectrum for Betelgeuse
(lower dotted line) and the fit parameters are also shown. [ JPEG | TIFF ] |
Figure 6. The Crab pulse profile showing
the optical light curve (o), the average radio light curve at 1380 MHz
(r), and a single giant pulse at 1357.5 MHz (gr). τ, time. Two periods
are shown for clarity. Various pulse parameters have been identified.
Also shown is the location of the precursor observed at lower frequencies
and the bridge emission seen particularly at higher frequencies. On this
scale, the GRP width corresponds to 0.00035 units of phase (12µs),
the radio pulse to 0.009 (300µs), and the optical pulse to 0.045
(1500µs). The avalanche photodiode (APD) band pass for these observations
was from 6000 to 7500 Å. Phase 0 corresponds to the arrival at
the solar system barycenter of the peak radio pulse. The optical light
curve for this plot was divided into 5000 phase bins. [ JPEG | TIFF ] |
Figure 7. This schematic figure illustrates
the geometry of the newly discovered ring, in relation to the spiral structure
of the Milky-Way. It has long been supposed that the disk of the Milky
Way galaxy slowly declines in brightness, vanishing into darkness at its
edge 50,000 light years from its centre. This startling new discovery
shows the outer regions of the disk are considerably more complicated
than previously thought, and sheds new light on the evolutionary history
of our Galaxy. [ JPEG | TIFF ] |
Figure 8 (left). The colour-magnitude
diagram of the Elais field N1 (l= 85°, b=+44°), which it is used
as a control field. This comparison region shows the usual Galactic components.
[ JPEG | TIFF ] Figure 9 (middle). The colour-magnitude diagram of a field WFS-0801 at l=150°, b=+20°. An additional colour-magnitude feature is present here over the expected disc, thick disc and halo components, and is seen as a narrow colour-magnitude diagram structure, similar to a main sequence with turn-off at (g–r)0~0.5, g0~19.5 (in the Vega system). The right-hand panel shows this ridge-line overlaid on the colour-magnitude diagram. The similarity in the turn-off colour of this feature and that of the Galactic thick disc and halo shows that its stellar population is of comparable age to those ancient Galactic components. [ JPEG | TIFF ]
Figure 10 (right). The left-hand panel shows the Hess diagram of
the INT WFS-0801 field and the right-hand panel displays the result
of subtracting the Elais-N1 comparison region from the data in the left-hand
panel. The excess population stands out very clearly. This excess is detected
at signal-to-noise ratio >30. [ JPEG
| TIFF ] |
Figure 11 (left). NGC3379 (M
105) with 109 PN line-of-sight velocities relative to the systemic velocity,
as measured with the PN.S instrument on the William Herschel Telescope.
The symbol sizes are proportional to the velocity magnitudes. Red crosses
indicate receding velocities, and blue boxes, approaching velocities.
Field of view is 8.4×8.4 arcmin=26×26 kpc=14×14 Reff.
[ JPEG | TIFF ] Figure 12 (right). Line-of-sight velocity dispersion profiles for three elliptical galaxies, as a function of projected radius in units of Reff. Open points show planetary nebula data (from the PN.S); solid points show diffuse stellar data. The vertical error bars show 1 uncertainties in the dispersion, and the horizontal error bars show the radial range covered by 68% of the points in each bin. Predictions of simple isotropic models are also shown for comparison: a singular isothermal halo (dashes) and a constant mass-to-light–ratio galaxy (dots). [ JPEG | TIFF ] |
Figure 13. Mosaic CCD Camera II (MCCDII).
Forty CCDs are seen aligned in 5×8 array. A liquid nitrogen tank
is attached backside of the Dewar to cool the CCDs down to appropriate
temperature. [ JPEG | TIFF
] |
Figure 14. The data are illustrated in these
colour figures; in each image green is the [OIII] emission, red the Hα
one, while blue corresponds to the broad band Sloan-g images, mainly dominated
by continuum stellar emission. In these images, planetary nebulae stand
out as green or yellow dots (a striking example is the green luminous object
on the upper-left side of the image of Leo A). [ JPEG
| TIFF ] |
Figure 15. Left panel: Large-scale image of
NGC 2950 showing the primary bar and disk with I-band contours and slit
positions overlaid. Right panel: Zoom into the central region of NGC 2950
showing its secondary bar. [ JPEG | TIFF ] |
Figure 16. Constraints on the joint distribution of Ωm and σ8 for the combination of Keck and WHT measurements. [ JPEG | TIFF ] |