R. Cabanac

The NASA Orbital Debris Observatory (NODO) astronomical survey uses a transit 3 m liquid mirror telescope to observe a strip of sky in 20 narrowband 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 narrowband filters ranging from 500 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 astronomical research with a radically new type of mirror.

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.

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.