Astron. Nachr. / AN 330, No. 2/3, 161 – 164 (2009) / DOI 10.1002/asna.200811146 Probing the nature of multiple lobe-like emissions in 3C 84 H. Nagai 1,⋆ , K. Asada 2 , A. Doi 2 , S. Kameno 3 , and M. Inoue 1 1 National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka, Tokyo 181-8588, Japan 2 Institute of Space Astronautical Science, Japan Aerospace Exploration Agency, Yoshinodai, Sagamihara 229-8510, Japan 3 Department of Physics, Faculty of Science, Kagoshima University, Korimoto 1-21-35, Kagoshima 890-0065, Japan Received 2008 Dec 8, accepted 2008 Dec 18 Published online 2009 Feb 15 Key words galaxies: active – galaxies: evolution – galaxies: individual (3C 84, Perseus A, NGC 1275) – galaxies: nuclei – radio continuum: galaxies The bright radio source 3C 84 has a CSO-like feature in the central 10-pc scale with extended emissions on scale up to kpc. Our kinematic and synchrotron age measurements support that the innermost feature is a CSO formed by recent restarted activity before the radio emission that originated in the earlier activities has completely faded. The average rate of the jet power of the innermost feature over the source age is at least ∼ 10 44 erg s −1 . Synchrotron age constraint for an outer lobe-like feature beyond the central CSO indicates that this feature originates in the outburst from ∼ 1.3×10 5 years ago. Inferred duty cycle of the jet ejection is much shorter than the time scale expected from microquasars. c  2009 WILEY-VCH Verlag GmbH& Co. KGaA, Weinheim 1 Introduction Compact symmetric objects (CSOs) are thought to be ra- dio sources at the early stage of their evolution. This view is strengthened by the measurements of separation speeds between hot spots (Owsianik & Conway 1998; Taylor et al. 2000; Conway 2002; Polatidis & Conway 2003; Gugliucci et al. 2005; Nagai et al. 2006) and synchrotron age mea- surements (Murgia et al. 1999; Murgia et al. 2003; Nagai et al. 2006; Orienti, Dallacasa & Stanghellini 2007). Gener- ally, no significant kpc-scale emissions beyond CSOs are found, suggesting that CSOs are “genuine” young or the subsequent bursts of jet activity, in the context of the re- current activity model (e.g., Clarke & Burns 1991), is much longer than the radiative life time of radio emission origi- nating in the earlier activity. However, there are some CSOs with extended emission (Baum et al. 1990; Marecki et al. 2003; Stanghellini et al. 2005). Such CSOs are thought to have been formed by the restarted activity before the radio emissions originating in the previous episode of jet activ- ity have completely faded. These sources are laboratories to probe the physical nature of “re-born” CSOs and the causes and time-scales of the recurrence of the central engine. The bright radio source 3C 84 (Perseus A), which is as- sociated with the giant elliptical galaxy NGC 1275, is an extreme case that exhibits intermittent jet ejections. A pair of jets is observed on scales ranging from sub-pc to 10- kpc scale (Pedlar et al. 1990; Venturi et al. 1993; Dhawan, Kellermann & Romney 1998; Silver, Taylor & Vermeulen 1998). There is a number of prominent features along the ⋆ Corresponding author: hiroshi.nagai@nao.ac.jp jets. The morphology of these prominent features is some- what like radio lobes rather than jets. In the innermost re- gion of 3C 84, there is a pair of radio lobes, one north and one south of the core. The extent of the innermost feature is ∼ 10 pc. The radio morphology is quite similar to that of CSOs. Constraining the kinematic and synchrotron ages of the central feature and outer features is crucial to understanding the nature of 3C 84 and the time scale of recurrence. In this paper, we constrain the age of the innermost feature and an outer feature around ∼ 80 mas from the core. Throughout this paper, we assume H 0 = 71 km s −1 Mpc −1 , Ω M =0.27, and Ω λ =0.73 (1 mas = 0.353 pc, 0.1 mas/yr = 0.113 c). Linear size and velocities have been calculated using E. L. Wright’s cosmology calculator (Wright 2006). 2 Archive data and data analysis In order to determine the synchrotron age, we analyzed mul- tifrequency observation data. The observations were carried out using the Very Long Baseline Array (VLBA) at 5.0, 8.4, 15.4, and 22.2 GHz in October 1995. A single Very Large Array (VLA) antenna also participated in the observations at 15.4 and 22.2 GHz. In addition, we also analyzed the data taken at a different epoch to study the kinematics of the source. This observation was carried out using ten VLBA stations together with a single VLA antenna and the Effels- berg station at 21.8 GHz in January 2000. An outer feature around ∼ 80 mas from the core is visi- ble at frequencies below 5 GHz (Silver et al. 1998; Walker et al. 2000). We analyzed low-frequency observation data c  2009 WILEY-VCH Verlag GmbH& Co. KGaA, Weinheim