Spectrum of Low-frequency Radio Emission from NGC 1275

Abstract

Two recent communications^1,2 have described an anomalous feature in the spectrum of the radio emission from the Seyfert galaxy NGC 1275 (3C784) (ref. 3) at frequencies above 3,000 Mc/s (Fig. 1). Between 178 Mc/s and 3,000 Mc/s, measured flux densities can be fitted with a constant spectral index. At lower frequencies, measurements by Burke and Franklin⁴ at 22.2 Mc/s and, more recently, by Erickson and Cronyn⁵ at 26.3 Mc/s and by Williams⁶ at 38 Mc/s, have given flux densities greater that would be predicted using this spectral index. This communication describes some preliminary results of observations at 10.03 Mc/s and 22.25 Mc/s made using the new pencil beam T-shaped arrays at the Dominion Radio Astrophysical Observatory. The observations at these frequencies also show excessive flux densities for the source.