Measurement of Spectral Breaks in Pulsar Wind Nebulae with Millimeter-wave Interferometry

We have observed pulsar wind nebulae in the three supernova remnants G11.2−0.3, G16.7+0.1, and G29.7−0.3 at 89 GHz with the Berkeley-Illinois-Maryland Association Array, measuring total flux densities of two of them for comparison with archival data at other frequencies. In G16.7+0.1, we find a break in the spectrum of the PWN at ∼ 26 GHz. In G29.7−0.3, our data suggest a break in the integrated spectrum of the central nebula at ∼ 55 GHz, lower than previously estimated. However, we have found spatial structure in the spectrum of this nebula. The emission to the north of pulsar J1846−0258 has a broken spectrum, with break frequency . 100 GHz, consistent with a conventional pulsar-powered nebula. The emission to the south of the pulsar has a near-power-law spectrum from radio to X-rays: this component may be unrelated to the PWN, or may be evidence of asymmetries and/or time evolution in the pulsar’s energy output. We present 89 GHz images of each remnant. Subject headings: pulsars: individual (J1846 − 0258)—radio continuum: ISM—SNR: individual (G11.2−0.3, G16.7+0.1, G29.7−0.3)—supernova remnants