SDSS photometry of Asteroids in Cometary Orbits

Aiming at exploring the relationship between asteroids in cometary orbits and other minor body populations from the observational point of view, I explore the large photometric database of the Sloan Digital Sky Survey - Moving Objects Catalog. The sample of interest was carefully selected analyzing colors and orbital properties within the data in the catalog. I computed the spectral slope for each object and compared with published spectroscopic results of other Asteroids in Cometary Orbits, as well as with other populations of asteroids in the outer region of the Main belt and Trojans. Using this extended database I find that Asteroids in Cometary Orbits with Tisserand parameter below 2.9, and especially below 2.8, are most likely of primitive origin. The population of objects with Tisserand parameter larger than 2.9 is a mixture of populations ranging from the inner to the outer Main belt.Comment: Accepted for publication: 13/11/201

Quasar H II Regions During Cosmic Reionization

Cosmic reionization progresses as HII regions form around sources of ionizing radiation. Their average size grows continuously until they percolate and complete reionization. We demonstrate how this typical growth can be calculated around the largest, biased sources of UV emission, such as quasars, by further developing an analytical model based on the excursion set formalism. This approach allows us to calculate the sizes and growth of the HII regions created by the progenitors of any dark matter halo of given mass and redshift with a minimum of free parameters. Statistical variations in the size of these pre-existing HII regions are an additional source of uncertainty in the determination of very high redshift quasar properties from their observed HII region sizes. We use this model to demonstrate that the transmission gaps seen in very high redshift quasars can be understood from the radiation of only their progenitors and associated clustered small galaxies. The fit sets a lower limit on the redshift of overlap at z = 5.8 +/- 0.1. This interpretation makes the transmission gaps independent of the age of the quasars observed. If this interpretation were correct it would raise the prospects of using radio interferometers currently under construction to detect the epoch of reionization.Comment: 6 pages, 3 figures, accepted by MNRAS, revised to match published versio