We have detected 535 planetary nebulae ( PNs ) in the flattened elliptical galaxy NGC 4697 , using the classic on-band , off-band filter technique with the Focal Reducer and Spectrograph ( FORS ) at the Cassegrain focus of the first 8-meter telescope unit of the ESO Very Large Telescope .
From our photometry we have built the [ O III ] \lambda 5007 planetary nebula luminosity function ( PNLF ) of NGC 4697 .
It indicates a distance of ( 10.5 \pm 1 ) Mpc to this galaxy , in good agreement with the distance obtained from surface brightness fluctuations and substantially smaller than a previous estimate of 24 Mpc used in earlier dynamical studies .
The PNLF also provides an estimate of the specific PN formation rate : ( 6 \pm 2 ) \times 10 ^ { -12 } PNs per year per solar luminosity .
Combining the information from on-band images with PN positions on dispersed , slitless grism images , we have obtained radial velocities for 531 of the 535 PNs .
We describe the slitless velocity method , and the calibration procedures we have followed .
The radial velocities have errors of about 40 km s ^ { -1 } and provide kinematic information up to a distance of almost three effective radii from the nucleus .
Some rotation is detected in the outer regions , but the rotation curve of this galaxy appears to drop beyond one effective radius .
Assuming an isotropic velocity distribution , the velocity dispersion profile is consistent with no dark matter within three effective radii of the nucleus ( however , some dark matter can be present if the velocity distribution is anisotropic ) .
We obtain a blue mass-to-light ratio of 11 .
Earlier M / L ratios for NGC 4697 were too small , because of the too large distance used for their derivation .