The filament of ionized gas in the outskirt of M87

We report on the filament of ionized gas found at the NE periphery of M87, the second brightest elliptical galaxy in the Virgo cluster. The object lie s at 3.16 arcmin (15.7 kpc) projected distance of the nucleus of M87, and i t coincides in position with the Eastern radio lobe of M87. Long slit spect roscopy confirmed the gaseous nature of this object, showing H-beta, [OIII] , [OI], [NII], H-alpha and [SII] lines, without any underlying continuum. T he redshift of the object, V = 1170 +/- 25 km s(-1), agrees with the veloci ty of M87 itself (V = 1280 km s(-1)), and with the bulk of the ionized mate rial found near the center of M87. The H-alpha flux of this filament corres ponds to 1% of the ionized material in M87. The radio-optical coincidence t ogether with the spectral characteristics suggest that the filament is ioni zed by a shock.