We present deep Giant Metrewave Radio Telescope ( GMRT ) radio observations at 240 , 330 and 610 MHz of the complex radio source at the center of the NGC1407 galaxy group .
Previous GMRT observations at 240 MHz revealed faint , diffuse emission enclosing the central twin-jet radio galaxy .
This has been interpreted as an indication of two possible radio outbursts occurring at different times .
Both the inner double and diffuse component are detected in the new GMRT images at high levels of significance .
Combining the GMRT observations with archival Very Large Array data at 1.4 and 4.9 GHz , we derive the total spectrum of both components .
The inner double has a spectral index \alpha = 0.7 , typical for active , extended radio galaxies , whereas the spectrum of the large-scale emission is very steep , with \alpha = 1.8 between 240 MHz and 1.4 GHz .
The radiative age of the large-scale component is very long , \sim 300 Myr , compared to \sim 30 Myr estimated for the central double , confirming that the diffuse component was generated during a former cycle of activity of the central galaxy .
The current activity have so far released an energy which is nearly one order of magnitude lower than that associated with the former outburst .
The group X-ray emission in the Chandra and XMM -Newton images and extended radio emission show a similar swept-back morphology .
We speculate that the two structures are both affected by the motion of the group core , perhaps due to the core sloshing in response to a recent encounter with the nearby elliptical galaxy NGC 1400 .