ELLIPTICAL GALAXIES
 An
extensive campaign to obtain surface photometry of a complete magnitude-limited
sample of 56 elliptical galaxies from the Revised Shapley-Ames catalogue
was completed by researchers. CCD photometry in B, V, and I was obtained
from the JKT (for the northern sample) and various telescopes at ESO (for
the south). Radial profiles of surface brightness, B-V, V-I and ellipticity
were determined, together with third and fourth-order Fourier coefficients
that quantify the deviations of these profiles from perfect ellipses. These
coefficients prove to be sensitive diagnostics of the presence of dust.
Narrow-band interference-filter photometry was also obtained in H alpha
+ [N II] to map the amount and morphology of dust and ionised gas. Optical
long-slit spectroscopy was performed on the WHT, the INT and at ESO to
determine the ratio of [N II] to H alpha. Dust lanes or patches were detected
in 23 of the galaxies: allowing for selection effects the true fraction
of elliptical galaxies containing dust is estimated to be about 80%. Ionised
gas was detected in 32 galaxies, with emission line intensity ratios typical
of LINER nuclei. The amounts of dust and gas detected are small: about
104 or 105
solar masses of ionised gas. The dust and ionised gas show a wide variety
of distributions which are consistent with the gas and dust being physically
associated, including some cases of patchy or filamentary structure suggestive
of a recent interaction event.
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ING facilities involved:
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William Herschel Telescope,
using ISIS
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Isaac Newton Telescope,
using IDS
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Jacobus Kapteyn Telescope,
using prime focus CCD camera
Some references:
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Goudfrooij, P. et al,
1994, "Interstellar matter in Shapley-Ames elliptical galaxies. I. Multicolour
CCD surface photometry", A&AS, 104, 179
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Goudfrooij, P. et al,
1994, "Interstellar matter in Shapley-Ames elliptical galaxies. II. The
distribution of dust and ionised gas", A&AS, 105, 341
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