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Your search keyword '"Yip, C. W."' showing total 4 results
Start Over Author "Yip, C. W." Topic astrophysics
4 results on '"Yip, C. W."'

1. Evidence for the presence of dust in intervening QSO absorbers from the Sloan Digital Sky Survey

Author

Khare, P., York, D. G., Berk, D. Vanden, Kulkarni, V. P., Crotts, A. P. S., Welty, D. E., Lauroesch, J. T., Richards, G. T., Alsayyad, Y., Kumar, A., Lundgren, B., Shanidze, N., Vanlandingha, J., Baugher, B., Hall, P. B., Jenkins, E. B., Menard, B., Rao, S., Turnshek, D., and Yip, C. W.

Subjects
Astrophysics
Abstract

We find evidence for dust in the intervening QSO absorbers from the spectra of QSOs in the Sloan Digital Sky Survey Data Release 1. No evidence is found for the 2175 A feature which is present in the Milky Way dust extinction curve. The extinction curve resembles the SMC extinction curve. The observed Delta(g-i) excess for QSOs with strong absorption systems appears to be a result of the reddening due to dust in the intervening absorbers., Comment: Poster paper presented at the IAU Colloquium #199 on "Probing Galaxies through Quasar Absorption Lines" held in Shanghai, China from March 14th to 18th, 2005

Published
2005
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2. Spectral Classification of Quasars in the Sloan Digital Sky Survey: Eigenspectra; Redshift and Luminosity Effects

Author

Yip, C. W., Connolly, A. J., Berk, D. E. Vanden, Ma, Z., Frieman, J. A., SubbaRao, M., Szalay, A. S., Richards, G. T., Hall, P. B., Schneider, D. P., Hopkins, A. M., Trump, J., and Brinkmann, J.

Subjects
Astrophysics
Abstract

We study 16,707 quasar spectra from the SDSS using the Karhunen-Lo\`eve (KL) transform (or Principal Component Analysis, PCA). The quasar eigenspectra of the full catalog reveal the following: 1st order - the mean spectrum; 2nd order - a host-galaxy component; 3rd order - the UV-optical continuum slope; 4th order - the correlations of Balmer emission lines. We find that the spectral classification of quasars is redshift and luminosity dependent, as such there does not exist a compact set (< 10 modes) of eigenspectra (covering 900 to 8000 angstrom) which can describe most variations (> 95%) of the entire catalog. We therefore construct several sets of eigenspectra in different redshift and luminosity bins. From these eigenspectra we find that quasar spectra can be classified (by the first two eigenspectra) into a sequence that is defined by a simple progression in the steepness of the slope of the continuum. We also find a dependence on redshift and luminosity in the eigencoefficients. The dominant redshift effect is a result of the evolution of the blended FeII emission (optical) and the Balmer continuum (the ``small bump''). A luminosity dependence is also present in the eigencoefficients and is related to the Baldwin effect. The eigenspectra constructed from the wavelength-selected SDSS spectra are found to agree with the principal components by Francis et al. (1992) and the well-known ``Eigenvector-1'' (Boroson and Green 1992). (Abridged), Comment: AJ accepted. 65 pages, 27 figures, 9 tables. Resolutions of some figures are lowered

Published
2004
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3. The Void Galaxy Survey

Author

van de Weygaert, R., Kreckel, K., Platen, E., Beygu, B., van Gorkom, J. H., van der Hulst, J. M., Aragón-Calvo, M. A., Peebles, P. J. E., Jarrett, T., Rhee, G., Kovač, K., Yip, C.-W., Ferreras, Pasquali, A, and Astronomy

Subjects
Physics, Void (astronomy), DWARF GALAXIES, Star formation, UNIVERSE, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, The Void, Redshift survey, Polar-ring galaxy, FIELDS, Accretion (astrophysics), Galaxy, EVOLUTION, COSMIC WEB, BOOTES, Astrophysics::Galaxy Astrophysics
Abstract

The Void Galaxy Survey (VGS) is a multi-wavelength program to study similar to 60 void galaxies. Each has been selected from the deepest interior regions of identified voids in the SDSS redshift survey on the basis of a unique geometric technique, with no a prior selection of intrinsic properties of the void galaxies. The project intends to study in detail the gas content, star formation history and stellar content, as well as kinematics and dynamics of void galaxies and their companions in a broad sample of void environments. It involves the HI imaging of the gas distribution in each of the VGS galaxies. Amongst its most tantalizing findings is the possible evidence for cold gas accretion in some of the most interesting objects, amongst which are a polar ring galaxy and a filamentary configuration of void galaxies. Here we shortly describe the scope of the VGS and the results of the full analysis of the pilot sample of 15 void galaxies.

Published
2011

4. Automated Classification Techniques for Large Spectroscopic Surveys.

Author

Banday, Anthony J., Zaroubi, Saleem, Bartelmann, Matthias, Connolly, A. J., Castander, F., Genovese, C., Hilton, E., Merrelli, A., Moore, A. W., Nichol, R. C., Schneider, J., Snir, Y., Szalay, A. S., Szapudi, I., Wasserman, L., and Yip, C. W.

Abstract

With the onset of large, systematically selected spectroscopic surveys we have the opportunity to understand the distribution and evolution of galaxies in terms of the mix of their spectral population. In this proceedings we describe a series of statistical techniques, ranging from Karhunen-Lo'eve transform to wavelet transforms, that are being applied to the spectra from the Sloan Digital Sky Survey in order to define a statistically robust and objective spectral classification scheme. The approach we describe for the classification of galaxy, stellar and QSO spectra is at the interface of astrophysics, statistics and computer science. To enable these techniques to be applied and interpreted successfully requires both robust statistical inference together with fast and efficient computer algorithms. Combining these three disciplines we can fully exploit the wealth of physical information present within the SDSS spectra. [ABSTRACT FROM AUTHOR]

Published
2001
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