2000A&A...361....1G

We report on the filament of ionized gas found at the NE periphery of M 87, the second brightest elliptical galaxy in the Virgo cluster. The object lies at 3.16arcmin (15.7 kpc) projected distance of the nucleus of M 87, and it coincides in position with the Eastern radio lobe of M 87. Long slit spectroscopy confirmed the gaseous nature of this object, showing H_β, [OIII], [OI], [NII], H_α and [SII] lines, without any underlying continuum. The redshift of the object, V=1170±25km/s, agrees with the velocity of M 87 itself (V=1280km/s), and with the bulk of the ionized material found near the center of M 87. The H_α flux of this filament corresponds to 1% of the ionized material in M 87. The radio-optical coincidence together with the spectral characteristics suggest that the filament is ionized by a shock.