Photometric Objects around Cosmic Webs (PAC) Delineated in a Spectroscopic Survey. I. Methods

Size of spectroscopic calibration samples for cosmic shear photometric redshifts

Weak gravitational lensing surveys using photometric redshifts can have their cosmological constraints severely degraded by errors in the photo-z scale. We explore the cosmological degradation vs the size of the spectroscopic survey required to calibrate the photo-z probability distribution. Previous work has assumed a simple Gaussian distribution of photo-z errors; here we describe a method fo...

A Survey for Circumstellar Disks around Young Substellar Objects

We have completed the first systematic survey for disks around spectroscopically identified young brown dwarfs and very low mass stars. For a sample of 38 very cool objects in IC 348 and Taurus, we have obtained L-band (3.8 μm) imaging with sufficient sensitivity to detect objects with and without disks. The sample should be free of selection biases for our purposes. Our targets span spectral t...

Spectro-photometric and Weak Lensing Survey of a Supercluster and Typical Field Region – I. Spectroscopic Redshift Measurements

We present results from a spectroscopic study of ∼4000 galaxies in a ∼ 6.2 deg field in the direction of the Aquarius supercluster and a smaller typical field region in Cetus, down to R < 19.5. Galaxy redshifts were measured using the Two Degree Field system on the Anglo-Australian Telescope, and form part of our wider efforts to conduct a spectro-photometric and weak gravitational lensing stud...

Spectroscopic Survey of G and K Dwarfs in the Hipparcos Catalog. I. Comparison between the Hipparcos and Photometric Parallaxes

The tension between the Hipparcos parallax of the Pleiades and other independent distance estimates continues even after the new reduction of the Hipparcos astrometric data and the development of a new geometric distance measurement for the cluster. A short Pleiades distance from the Hipparcos parallax predicts a number of stars in the solar neighborhood that are sub-luminous at a given photosp...

A delineated R-tree indexing method for managing moving objects