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Nearby supernova rates from the Lick Observatory Supernova Search – I. The methods and data base

Authors

  • Jesse Leaman,

    Corresponding author
    1. Department of Astronomy, University of California, Berkeley, CA 94720-3411, USA
    2. NASA Ames Research Center, Mountain View, CA 94043, USA
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  • Weidong Li,

    Corresponding author
    1. Department of Astronomy, University of California, Berkeley, CA 94720-3411, USA
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  • Ryan Chornock,

    Corresponding author
    1. Department of Astronomy, University of California, Berkeley, CA 94720-3411, USA
    2. Harvard–Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
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  • Alexei V. Filippenko

    Corresponding author
    1. Department of Astronomy, University of California, Berkeley, CA 94720-3411, USA
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E-mail: jleaman@astro.berkeley.edu (JL); wli@astro.berkeley.edu (WL); rchornock@cfa.harvard.edu (RC); alex@astro.berkeley.edu (AVF)

ABSTRACT

This is the first paper of a series in which we present new measurements of the observed rates of supernovae (SNe) in the local Universe, determined from the Lick Observatory Supernova Search. We have obtained 2.3 million observations of 14 882 sample galaxies over an interval of 11 years (1998 March to 2008 December). We considered 1036 SNe detected in our sample and used an optimal subsample of 726 SNe (274 Type Ia SNe, 116 Type Ibc SNe and Type II 324 SNe) to determine our SN rates. This is the largest and most homogeneous set of nearby SNe ever assembled for this purpose, and ours is the first local SN rate analysis based on CCD imaging and modern image-subtraction techniques. In this paper, we lay the foundation of the study. We derive the recipe for the control-time calculation for SNe with a known luminosity function and provide details on the construction of the galaxy and SN samples used in the calculations. Compared with a complete volume-limited galaxy sample, our sample has a deficit of low-luminosity galaxies but still provides enough statistics for a reliable rate calculation. There is a strong Malmquist bias, so the average size (luminosity or mass) of the galaxies increases monotonically with distance, and this trend is used to showcase a correlation between SN rates and galaxy sizes. Very few core-collapse SNe are found in early-type galaxies, providing strong constraints on the amount of recent star formation within these galaxies. The small average observation interval (9 d) of our survey ensures that our control-time calculations can tolerate a reasonable amount of uncertainty in the luminosity functions of SNe. We perform Monte Carlo simulations to determine the limiting magnitude of each image and the SN detection efficiency as a function of galaxy Hubble type. The limiting magnitude and the detection efficiency, together with the luminosity function derived from a complete sample of very nearby SNe in Paper II, will be used to calculate the control time and the SN rates in Paper III.

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