Integral Field Spectroscopy of Faint Haloes of Planetary Nebulae

Abstract

We present the first integral field spectroscopy observations of the two planetary nebulae NGC3242 and NGC4361 with the VIMOS instrument attached to VLT-UT3. By co-adding a large number of spaxels we reach an emission line detection limit of 5.E-18 erg cm^{-2} s^{-1} arcsec^{-2}. In the case of NGC3242, we succeed in determining some properties of the halo. The radial surface brightness profile in [OIII] implies increasing mass loss before the formation of the PN. Traces of the mysterious 'rings' are clearly visible. We find for the first time an apparent temperature gradient across a halo: from about 16000 K close to the shell/halo transition to 20000 K at the halo's outer edge. No line emission is seen in the suspected halo region of NGC4361 down to the sensitivity limit.

8 pages, 5 figures, accepted for publication in The Astrophysical Journal Letters