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Session 19 - Source Surveys, Galaxy Surveys, Distance Scale II.
Display session, Wednesday, January 07
Exhibit Hall,
Most pulsar population models have been constructed using samples of pulsars primarily found in period-dispersion searches whose detection limits are heavily dependent on those quantities. Such samples are biased against pulsars with low modulation due to small period, wide beams, high interstellar dispersion and scattering, or a combination of these effects.
Using the results of new large-scale radio surveys, we can study the intrinsic luminosity, spectral index, and spatial distributions of the galactic pulsar population free from modulation bias. Our model data consist of 71 known pulsars rediscovered in the 1.4 GHz NRAO VLA Sky Survey (NVSS) and a complete sample of 71 steep-spectrum (\alpha \geq 1.5, where S_\nu \propto \nu^-\alpha) point sources in both the NVSS and the Texas 360 MHz sky survey. Although the original pulsar catalog is incomplete, our redetection method is complete and unbiased, yielding known pulsars stronger than 2.5 mJy at 1.4 GHz. The steep-spectrum sources are likely to be either pulsars or radio galaxies with exceptionally steep spectra, whose identities we will establish with planned reobservations. The steep-spectrum sample contains all point sources with \alpha\geq 1.5, stronger than 2.5 mJy at 1.4 GHz and 200 mJy at 360 MHz, and it is \approx 90% complete at those limits.
For our likelihood analysis we adopt limited power-law distributions for the luminosity and spectral index parameters, and a plane-parallel exponential or Gaussian distribution for the spatial density parameters. The results of this model may be used to optimize future pulsar searches by estimating the expected number of detectable pulsars for various search schemes. Since this model is independent of period and interstellar dispersion, it may yield new populations of objects which are difficult to detect using traditional pulsar search methods.
