k-corrections and spectroscopic diversity of SNe Ia

k-corrections and spectroscopic diversity of SNe Ia

Eric Y. HsiaoUniversity of Victoria

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k-corrections of SNe Ia

converts an observed magnitude to that which would be observed in the rest frame in another filter

usually depends on an assumed spectral distribution (spectral template)

spectroscopic diversity causes k-correction errors

Eric Y. Hsiao

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broadband colors

Eric Y. Hsiao

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spectral templateprocedures

quantify the feature strengths of the library spectra

determine the weighted mean feature strength at each epoch and wavelength

adjust a base spectral template to the weighted mean feature strengths

Eric Y. Hsiao

Hsiao et al. 2007 ApJ, 663, 1187

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spectral templatemeasurement of spectral features

Eric Y. Hsiao

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reduction of systematic errors

Eric Y. Hsiao

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principal component analysis

PCA reduces multi-dimensional data into principal components

first component is the vector pointing toward the direction of the highest variance in the multi-dimensional data space

rest of the components are orthogonal vectors ranked by their variances

Eric Y. Hsiao

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spectroscopic sequence (V band)

Eric Y. Hsiao

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spectroscopic sequence (I band)

Eric Y. Hsiao

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spectroscopic sequence (I band)

Eric Y. Hsiao

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spectroscopic sequence (I band)

Eric Y. Hsiao

2000cx

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spectroscopic sequence (I band)

Eric Y. Hsiao

1999aa

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effect of epoch and stretch

Eric Y. Hsiao

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k-correction errors

Eric Y. Hsiao

k-correction errors Dmag Dflux

broadband color 10-1 10-1

spectral features 10-2 10-2

spectroscopic sequence 10-3 10-3

bandpass uncertainty 10-2~10-3 10-2~10-3

evolution small?