ING Scientific Highlights in 1988
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ING Scientific Highlights
in 1988*

*Astronomical discoveries following from observations carried out with the ING telescopes

[ 1986-1987 Scientific Highlights | 1989 Scientific Highlights


In 1983 and 1984, the faint high galactic latitude star PG 0832+676 was observed at high spectral dispersion on the 5-m Hale telescope. From these observations PG 0832+676 appeared to be a normal early-type star rather than a hot subdwarf, which is how it had previously been classified.

Although astronomers were disappointed that their observations did not bear on the problem which they were investigating, they decided to take further spectra using the Isaac Newton Telescope. These data were analysed using model atmosphere techniques, and showed that PG 0832+676 is indeed a normal Population I OB-type star abundances for the heavier elements.

The galactic co-ordinates of PG 0832+676 and its apparent magnitude imply that the star lies at a distance of 18 kpc from the plane of the Galaxy. The questions that occurs is: what is a normal B-dwarf doing up in the halo? With their short lifetimes, B stars which form from gas in the galactic low velocity of the star coupled with its laerge z-distance effectively rules out the possibility that it formed in the disc and was then ejected into the halo. PG 0832+676 therefore becomes a member of a rare set of stars that appear to have been formed in the halo itself.

Where did the gas out of which it was formed come from? Was the star formed from the high velocity clouds which provoked the observations in the first place? The model atmospheres fitted to the observations indicate that the abundances in PG 0832+676 are "normal ", and typical of B stars formed from galactic plane material. So astronomers conjectures that the star is evidence for the transportation of gas from the galactic plane into the halo, in a process still occuring at the present time. This is reminiscent of the idea known as the "galactic fountain" in which supernovae energise interstellar material into the galactic halo.

More information

ING facilities involved: 

  • Isaac Newton Telescope using IDS.
Some references: 
  • Keenan, F., Dufton, P., Brown, P., 1989, "B star 18 kpc above the Galactic Plane", Gemini Newsletter, 23, 1. 



NGC1275, the central galaxy of the Perseus cluster, has presented an intriguing puzzle ever since Minkowski (1957) discovered two discrete systems of emission line gas at redshifts of 5300 and 8200 km/s.

The low velocity system is at the same redshift as the galaxy. Narrow-band H-alpha images show that this emission line gas is highly filamentary in nature. The filaments are embedded in an extensive X-ray halo, which may be accreting onto the galaxy, and it has been suggested that the filaments are a result of a thermal instability in this accretion flow. NGC1275 is also associated with one of the brightest extragalactic radio sources (Perseus A = 3C84), and it may be that the formation of optical filaments is related to the ejection of radio-emitting plasma.

The nature of the high velocity system is even less well understood. The high velocity gas is seen in absorption against NGC1275, and so in spite of the much higher redshift must represent foreground material. The available data on the kinematics and excitation of the gast suggest a picture in which the high velocity system is a spiral galaxy falling into the centre of the Perseus cluster with a relative velocity of 3000 km/s.

The ability of TAURUS to obtain simultaneous spectra over a wide field makes this instrument ideal for studying the morphology and kinematics of the high velocity gas. Astronomers therefore observed NGC1275 with TAURUS 2 on the William Herschel Telescope. The observations covered the [OIII] 5007 Å emission line redshifted by 8200 km/s, with a velocity resolution of 30 km/s and a velocity range of 600 km/s. 

These results show that the emission line region has a complex morphology. Most of the emission is concentrated in two fairly compact regions separated by about 30 arcsec in an east-west direction, although weaker more extended emission is also present. Neither of the brightness peaks is coincident with the nucleus of NGC1275. This morphology does not support the standard picture of a disk galaxy viewed edge-on.

In general  the velocity field shows a fairly smooth gradient in an east-west direction, and the line widths are unresolved by TAURUS (FWHM < 30 km/s). This is broadly consistent with normal galactic rotation. However, there is peculiar velocity structure close to the western brightness peak, where the direction of the velocity gradient changes from east-west to north-south.

More information

ING facilities involved:

  • William Herschel Telescope, using TAURUS 2 in Fabry-Perot mode
Some references: 
  • Unger, S., and Taylor, K., 1988, "The high velocity gas in NGC1275", Gemini Newsletter,18, 10.



The importance of lithium observations lies on being a probe of cosmological models and also as a tracer for stellar structure and evolution. New measurements of the lithium abundance in a sample of 37 field dwarfs of low metallicity was corried out. Extremely Metal-Deficient (EMD) dwarfs form a much more homogeneous population with regard to 7Li abundance that stars somewhat more metal-rich. These EMD dwarfs show Li abundances for surface temperatures between 5500K and 6300K, which average log N(Li)=2.08 (±0.10). A trend towards 2.2 is found as Teff approaches 6300K. By comparing the Li-Teff of the EMD stars with the published curve for the Hyades, the astronomers show that it is improbable that the warmer EMD stars have depleted their Li significantly, in spite of their age. They consider that these stars offer the best opportunity to make a reliable measurement of the primordial Li abundance, which they estimate to be log N(Li)=2.2(±0.15).

For somewhat less metal-deficient stars they find a wider scatter in Li abundances. Li depletion appears to set in at higher temperatures for the moderately metal-deficient stars than for the extremely metal-deficient, consistent with metallicity-dependent depletion rates.

Using a recent theoretical curve of Li against the universal baryon to photon ratio from a standard Big Bnag model, and the above cited primordial abundance, n is constrained to the range 1.2×10-10 <= n <= 8×10-10.

9Be has a special place in schemes of nucleosynthesis. It is the lightest stable nuclide not synthesized in the Big Bang and it is destroyed in stellar interiors at temperatures higher than 3×106K. Nevertheless it has been widely observed in nature: in the sun, in meteorites, in the interstellar medium and in a variety of atmospheres of stars of different ages. The currently accepted explanation for its observed existence is spallation of heavy nuclei, mostly CNO nuclei, ny cosmic rays in the interstellar medium.

Recently six highly metal-deficient dwarfs in the spectral range containing the resonance doublet of 9Be II at 3130 Å were observed. Using the method of spectral synthesis astronomers evaluated the abundance of 9Be in these objects. They set upper limits to the 9Be abundance, 9Be/H, below 2.5×10-12. These are the first reported detections of 9Be in stars with such low metalicities. From these results and literature values for 9Be in more metallic stars, they can constrain models for galatic evolution: those with entail an early burst of 9Be production are ruled out. The data are used to predict the spallogenic content of 7Li, 6Li, 10B and 11B in the material from which the sample stars was formed and hence to limit the galactocentric fraction of 7Li in highly metal-deficient stars. A firm upper limit of 0.1 dex can be set to the fraction of measured 7Li in such stars which is either non-primordial, or is due to spectral blending of 6Li, leaving virtually all of the measured 7Li as primordial.

More information

ING facilities involved:

  • Isaac Newton Telescope, using the IDS with either a CCD or a IPCS detector.
Some references: 
  • Rebolo, R., Beckman, J. & Molaro P., 1987, "The lithium abundance in the extremely metal-deficient dwarf G64-12", Astron. & Astrophys. Lett., 172, 17.
  • Rebolo, R., Molaro, P., and Beckman, J.E., 1988, "Lithium abundances in metal-deficient dwarfs", Astron. & Astrophys., 192, 192
  • Rebolo, R., Molaro, P., Abia, C. & Beckman, J.E., 1988, "Abundances of 9Be in a sample of highly metal-deficient dwarfs: implications for early galactic nucleosynthesis and primordial lithium", Astron. & Astrophys., 193, 193.
  • Rebolo, R. & Beckman, J.E., 1988, "Lithium and rotation in the Hyades late F and G stars", Astron. & Astrophys., 201, 267.
  • "El Berilio medido en estrellas muy antigua, nuevo soporte a la producción de litio en el Big Bang", IAC Noticias, May 1987, 3.



During the period 11-16 April first use was made of the GHRIL facility on the William Herschel Telescope. The GHRIL is a permanent facility mounted on one of the Nasmyth platforms, consisting of a large optical table attached to the main telescope yoke, within a room which is coupled to the telescope only at the azimuth bearing. It is intended to have a common-user infrastructure of detectors and data collection hardware/software, and to offer a laboratory in which users may set up many different optical arrangements. This was its first use and the Nasmyth focus was still not fully commissioned.

The equipment on this first occasion was set up and used by the TRANSPUTER project team from the Instituto de Astrofísica de Canarias, Tenerife, and University College Galway, Ireland. This project aims at producing image sharpening on-line using a network of fixed and floating point TRANSPUTERS. The objective of the project is to avoid the data storage problems inherent in recording the addresses and times of individual photons for off-line reduction, and to produce sharp images in time for the astronomer to react while still having access to the telescope.

In this run there was no attempt at on-line processing. The data were collected from an Imaging Photon counting Detector (IPD) behind a collimator/camera system designed to allow the aperture of the telescope to be varied to take account of the seeing conditions - in the event the seeing conditions were such that the largest circular aperture was used throughout the data collection period (a similar technique had been tested at the Cassegrain focus of the Isaac Newton Telescope in previous years, making use of the empty TAURUS box for the optics and an IPCS detector). 

Two bright double systems were selected from the Bright Star Catalogue, namely ADS8148 and ADS8231, having catalogued separations of 1.1 arcsec and 0.5 arcsec respectively. ADS8148 was clearly resolved (both live and on videotape) in spite of a magnitude ratio of 2.8 and a large field of view. ADS8231 was then attempted, and the astronomers again saw  clear separation, and remarkably steady images. They now believe that ADS8231 has a separation of <0.7 arcsec, giving an integrated resolution of <0.4 arcsec for the full 4.2m aperture.

More information

ING facilities involved:

  • William Herschel Telescope, using own instrumentation on the GHRIL
  • Isaac Newton Telescope, using own instrumentation at the Cassegrain focus
Some references: 
  • Campos-Aguilar, A.; Pérez-Fournon, I.; Carranza, J. M., 2011, "Image sharpening observations of active galactic nuclei", in ESA Workshop on Optical Interferometry in Space, 221.
  • "Obtención de imágenes de alta resolución espacial con la técnica de "Image Sharpening", IAC Noticias, January 1987, 4.
  • Redfern, M., et al., 1988, "First Light on the GHRIL", Gemini Newsletter, 20, 1.
  • "Imágenes de alta resolución de galaxias activas", IAC Noticias, January 1988, 3.
  • Pérez-Fournon, I; Campos-Aguilar, A., 1988, "High-resolution imaging of active galactic nuclei", Advances in Space Research, 8, 71.



First stellar seismology observations were obtained with the William Herschel Telescope. The astronomers observed Arcturus star for 9.5 hours making use of 2 spectrophotometres and a magneto-optical filter mounted on the optical bench at the GHRIL (Roca, T., et al., 1988, "Primeras observaciones de sismología estelar con el telescopio William Herschel", IAC Noticias, June 1988, 2).

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Last modified: 21 November 2011