Images at 20cm and the Spectrum Index of NGC2997

Abstract

We present total intensity maps of the galaxy NGC 2997 at frequencies 1435.1 MHz ( λ 21 cm) and 1652.4 MHz ( λ 18 cm) observed with the Very Large Array (VLA). The high spatial resolution allows us to distinguish two dominant arms. Using multi-frequency data, we separate the thermal and non-thermal contributions to the radio emission. The thermal emission is about 35% of the total emission at λ 3 cm. We use it to estimate a space-averaged thermal electron density, n e ~0.049 cm −3 . The spectral index map shows that the optical arms and the central part of the galaxy have flatter spectra. We also determine the flux densities of 22 radio sources in the field-of-view of 25' .