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Dimension-reduction techniques can greatly improve statistical inference in astronomy. A standard approach is to use Principal Components Analysis (PCA). In this letter we apply a recently-developed technique, diffusion maps, to astronomical spectra, and develop a robust, eigenmode-based framework for regression and data parameter-ization. We show how our(More)
To further our knowledge of the complex physical process of galaxy formation, it is essential that we characterize the formation and evolution of large databases of galaxies. The spectral synthesis STARLIGHT code of Cid Fernandes et al. (2004) was designed for this purpose. Results of STARLIGHT are highly dependent on the choice of input basis of simple(More)
We present optical (UBVRI) sky brightness measures from 1992 through 2006. The data are based on CCD imagery obtained with the CTIO 0.9-m, 1.3-m, and 1.5-m telescopes. The Band V-band data are in reasonable agreement with measurements previously made at Mauna Kea, though on the basis of a small number of images per year there are discrepancies for the years(More)
Parameter estimation in astrophysics often requires the use of complex physical models. In this paper we study the problem of estimating the parameters that describe star formation history (SFH) in galaxies. Here, high-dimensional spectral data from galaxies are appropriately modeled as linear combinations of physical components, called simple stellar(More)
The changing heavens have played a central role in the scientific effort of astronomers for centuries. Galileo's synoptic observations of the moons of Jupiter and the phases of Venus starting in 1610, provided strong refutation of Ptolemaic cosmology. These observations came soon after the discovery of Kepler's supernova had challenged the notion of an(More)
The development of fast and accurate methods of photometric redshift estimation is a vital step towards being able to fully utilize the data of next-generation surveys within precision cosmology. In this paper we apply a specific approach to spectral connectivity analysis (SCA; Lee & Wasserman 2009) called diffusion map. SCA is a class of non-linear(More)
We introduce a weighted method of clustering the individual units of a segmented image. Specifically, we analyze geologic maps generated from experts' analysis of remote sensing images, and provide geologists with a powerful method to numerically test the consistency of a mapping with the entire multi-dimensional dataset of that region. Our weighted(More)
This paper presents the design, implementation and utilization of a large Mass Storage Subsystem (MSS) at the Numerical Aerodynamics Simulation (NAS) at NASA-Ames Research Center. The MSS supports a large networked, multi-vendor Unix-based supercomputing facility. The MSS at Ames Research Center provides all processors on the Numerical Aerodynamics System(More)
Type Ia supernovae are thought to result from a thermonuclear explosion of an accreting white dwarf in a binary system, but little is known of the precise nature of the companion star and the physical properties of the progenitor system. There are two classes of models: double-degenerate (involving two white dwarfs in a close binary system) and(More)