arXiv subjects

R. Cabanac

Publications and source records attributed to R. Cabanac.

39 records · Page 3Linked to original sources

arXiv1998

A Search for Peculiar Objects with the NASA Orbital Debris Observatory 3-m Liquid Mirror Telescope

The NASA Orbital Debris Observatory (NODO) astronomical survey uses a transit 3-m liquid mirror telescope to observe a strip of sky in 20 narrow-band filters. In this article, we analyze a subset of data from the 1996 observing season. The catalog consists of 18,000 objects with 10<V<19 observed in 10 narrow-band filters ranging from 500 nm to 950 nm. We first demonstrate the reliability of the data by fitting the Bahcall-Soneira model of the Galaxy to the NODO magnitude counts and color counts at various galactic latitudes. We then perform a hierarchical clustering analysis on the sample to extract 206 objects, out of a total of 18,000, showing peculiar spectral energy distributions. It is a measure of the reliability of the instrument that we extract so few peculiar objects. Although the data and results, per se, may not seem otherwise particularly remarkable, this work constitutes a milestone in optical astronomy since this is the first article that demonstrates astromomical research with a radically new type of mirror.

astro-ph↗

arXiv1996

A Study of Cross-Correlation and Breakfinding Algorithms Applied to the Measurements of Redshifts in Very Low Resolution Spectra

In this article we compare the cross-correlation and breakfinder techniques applied to the measurements of redshifts from low-resolution spectra. We assume spectra obtained from multinarrowband imagery, a technique for multi-object spectrophotometry. Comparing the cross-correlation with the breakfinder, we find that neither is intrinsically superior to the other. They have comparable precision for early type galaxies but the cross-correlation is clearly superior for later type galaxies. On the other hand, unlike the breakfinder, the cross-correlation is sensitive to instrumental errors as well as the shape of the templates used. We carried out simulations with two types of global spectral errors: a slope error and sinusoidal errors. They can introduce serious systematic errors in redshifts measured with the cross-correlation. The breakfinder is a spectrally local test and does not suffer from this type of error. We therefore conclude that the two techniques are complementary and that they should both be used to help flag objects for which they give abnormally discrepant redshifts.

astro-ph↗

arXiv1994

Ubc/Laval 2.7-Meter Liquid Mirror Telescope

We report the successful development and operation of a large astronomical liquid-mirror telescope. Employing a rotating 2.7-meter diameter mirror with a surface of liquid mercury, the telescope images a half-degree diameter field centered at the zenith. Located near Vancouver, British Columbia, it is equipped with a low-noise 2048x2048-pixel CCD detector, operating in TDI mode, which produces continuous imaging of a 20 arcminute-widestrip of sky with 2 minute integration time. Images with FWHM of 2 arcseconds or less are regularly obtained. This image quality is limited only by atmospheric seeing and star-trail curvature. The telescope is equipped with a series of narrow-band filters, designed to produce 40-point spectral energy distributions from 0.4 to 1.0 microns of all detected objects. These will allow classification and redshift estimation of approximately 25,000 galaxies and 1,000 quasars to a limiting magnitude of R~21.

astro-ph↗