The origin of the optical emission lines associated with extragalactic radio sources
1992; IOP Publishing; Volume: 384; Linguagem: Inglês
10.1086/170888
ISSN1538-4357
AutoresS. M. Viegas, E. M. de Gouveia Dal Pino,
Tópico(s)Radio Astronomy Observations and Technology
Resumoview Abstract Citations (22) References (47) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Origin of the Optical Emission Lines Associated with Extragalactic Radio Sources Viegas, S. M. ; de Gouveia dal Pino, E. M. Abstract We investigate the observed extended emission-line regions (EELRs) associated with the jets and lobes of low-redshift extragalactic radio sources with moderate power (3C 227, 3C 277.3, 3C 305, Cen A [NGC 5128], NGC 7385, PKS 0349-27, PKS 2152-69, and Minkowski's Object). Using hybrid models which take into account the coupled effect of both the photoionization by a nonthermal radiation and the thermal collisions due to shocks, we calculated the line intensity ratio diagrams that best fit the observations. We found that the main energy sources of the EELR are: (1) a power-law radiation, with a flux at 1 Ryd F_H_~(10^8^-10^10^) cm^-2^ s^-1^ eV^-1^ and a spectral index α = 2.2-2.8 (equivalent to 1.2-1.8 for a flux given in units of ergs cm^-2^ s^-1^ eV^-1^), which probably originates at the central region of the galaxy, and (2) shocks with velocities V_0_~ 300-10000 km s^-1^ and preshock densities n_0_~5-100 cm^-3^, resulting from the interaction of the relativistic plasma flow with the ambient medium. In all cases investigated, a [N/O] underabundance by a factor 4 relative to the cosmic value is required in order to explain the observed [NII]/[O II] line ratios. The ability of radio jets to interact with the ambient medium and stimulate star formation has been suggested by a number of observational works and demonstrated by a number of authors. Considering both the estimated lifetimes of the radio sources and the stellar evolution time scales, the [N/O] underabundance could be explained by a burst of star formation where only the more massive stars (M >= 8 M_sun_) have already evolved. Publication: The Astrophysical Journal Pub Date: January 1992 DOI: 10.1086/170888 Bibcode: 1992ApJ...384..467V Keywords: Emission Spectra; Extragalactic Radio Sources; Line Spectra; Radio Jets (Astronomy); Star Formation; Abundance; Astronomical Models; Photoionization; Radio Astronomy; Astrophysics; GALAXIES: JETS; LINE: FORMATION; RADIO CONTINUUM: GALAXIES; STARS: FORMATION full text sources ADS | data products NED (8) SIMBAD (6)
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