Galaxy Zoo: the fraction of merging galaxies in the SDSS and their morphologies

D.W. Darg; S. Kaviraj; C.J. Lintott; J. Silk; K. Schawinski; M. Sarzi; S. Bamford; R. Proctor; D. Andreescu; P. Murray; R.C. Nichol; D. Thomas; M.J. Raddick; A.S. Szalay; J. Vandenberg; A. Slosar

doi:10.1111/j.1365-2966.2009.15686.x

Galaxy Zoo: the fraction of merging galaxies in the SDSS and their morphologies

D.W. Darg, S. Kaviraj, C.J. Lintott, J. Silk, K. Schawinski, M. Sarzi, S. Bamford, R. Proctor, D. Andreescu, P. Murray, R.C. Nichol, D. Thomas, M.J. Raddick, A.S. Szalay, J. Vandenberg, A. Slosar

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Abstract

We present the largest, most homogeneous catalogue of merging galaxies in the nearby Universe obtained through the Galaxy Zoo project – an interface on the World Wide Web enabling large-scale morphological classification of galaxies through visual inspection of images from the Sloan Digital Sky Survey (SDSS). The method converts a set of visually inspected classifications for each galaxy into a single parameter (the 'weighted-merger-vote fraction,'fm) which describes our confidence that the system is part of an ongoing merger. We describe how fm is used to create a catalogue of 3003 visually selected pairs of merging galaxies from the SDSS in the redshift range 0.005 < z < 0.1 . We use our merger sample and values of fm applied to the SDSS Main Galaxy Spectral sample to estimate that the fraction of volume-limited (Mr < −20.55) major mergers (1/3 < M*1/M*2 < 3) in the nearby Universe is 1–3 ×C per cent, where C∼ 1.5 is a correction factor for spectroscopic incompleteness. Having visually classified the morphologies of the constituent galaxies in our mergers, we find that the spiral-to-elliptical ratio of galaxies in mergers is higher by a factor of ∼2 relative to the global population. In a companion paper, we examine the internal properties of these merging galaxies and conclude that this high spiral-to-elliptical ratio in mergers is due to a longer time-scale over which mergers with spirals are detectable compared to mergers with ellipticals.

Original language	English
Pages (from-to)	1043-1056
Number of pages	14
Journal	Monthly Notices of the Royal Astronomical Society
Volume	401
Issue number	2
DOIs	https://doi.org/10.1111/j.1365-2966.2009.15686.x
Publication status	Published - 2010

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Darg, D. W., Kaviraj, S., Lintott, C. J., Silk, J., Schawinski, K., Sarzi, M., Bamford, S., Proctor, R., Andreescu, D., Murray, P., Nichol, R. C., Thomas, D., Raddick, M. J., Szalay, A. S., Vandenberg, J., & Slosar, A. (2010). Galaxy Zoo: the fraction of merging galaxies in the SDSS and their morphologies. Monthly Notices of the Royal Astronomical Society, 401(2), 1043-1056. https://doi.org/10.1111/j.1365-2966.2009.15686.x

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title = "Galaxy Zoo: the fraction of merging galaxies in the SDSS and their morphologies",

abstract = "We present the largest, most homogeneous catalogue of merging galaxies in the nearby Universe obtained through the Galaxy Zoo project – an interface on the World Wide Web enabling large-scale morphological classification of galaxies through visual inspection of images from the Sloan Digital Sky Survey (SDSS). The method converts a set of visually inspected classifications for each galaxy into a single parameter (the 'weighted-merger-vote fraction,'fm) which describes our confidence that the system is part of an ongoing merger. We describe how fm is used to create a catalogue of 3003 visually selected pairs of merging galaxies from the SDSS in the redshift range 0.005 < z < 0.1 . We use our merger sample and values of fm applied to the SDSS Main Galaxy Spectral sample to estimate that the fraction of volume-limited (Mr < −20.55) major mergers (1/3 < M*1/M*2 < 3) in the nearby Universe is 1–3 ×C per cent, where C∼ 1.5 is a correction factor for spectroscopic incompleteness. Having visually classified the morphologies of the constituent galaxies in our mergers, we find that the spiral-to-elliptical ratio of galaxies in mergers is higher by a factor of ∼2 relative to the global population. In a companion paper, we examine the internal properties of these merging galaxies and conclude that this high spiral-to-elliptical ratio in mergers is due to a longer time-scale over which mergers with spirals are detectable compared to mergers with ellipticals.",

author = "D.W. Darg and S. Kaviraj and C.J. Lintott and J. Silk and K. Schawinski and M. Sarzi and S. Bamford and R. Proctor and D. Andreescu and P. Murray and R.C. Nichol and D. Thomas and M.J. Raddick and A.S. Szalay and J. Vandenberg and A. Slosar",

note = "{\textquoteleft}The definitive version is available at www3.interscience.wiley.com '. Copyright Royal Astronomical Society. DOI: 10.1111/j.1365-2966.2009.15686.x",

year = "2010",

doi = "10.1111/j.1365-2966.2009.15686.x",

language = "English",

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Darg, DW, Kaviraj, S, Lintott, CJ, Silk, J, Schawinski, K, Sarzi, M, Bamford, S, Proctor, R, Andreescu, D, Murray, P, Nichol, RC, Thomas, D, Raddick, MJ, Szalay, AS, Vandenberg, J & Slosar, A 2010, 'Galaxy Zoo: the fraction of merging galaxies in the SDSS and their morphologies', Monthly Notices of the Royal Astronomical Society, vol. 401, no. 2, pp. 1043-1056. https://doi.org/10.1111/j.1365-2966.2009.15686.x

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T1 - Galaxy Zoo: the fraction of merging galaxies in the SDSS and their morphologies

AU - Darg, D.W.

AU - Kaviraj, S.

AU - Lintott, C.J.

AU - Silk, J.

AU - Schawinski, K.

AU - Sarzi, M.

AU - Bamford, S.

AU - Proctor, R.

AU - Andreescu, D.

AU - Murray, P.

AU - Nichol, R.C.

AU - Thomas, D.

AU - Raddick, M.J.

AU - Szalay, A.S.

AU - Vandenberg, J.

AU - Slosar, A.

N1 - ‘The definitive version is available at www3.interscience.wiley.com '. Copyright Royal Astronomical Society. DOI: 10.1111/j.1365-2966.2009.15686.x

PY - 2010

Y1 - 2010

N2 - We present the largest, most homogeneous catalogue of merging galaxies in the nearby Universe obtained through the Galaxy Zoo project – an interface on the World Wide Web enabling large-scale morphological classification of galaxies through visual inspection of images from the Sloan Digital Sky Survey (SDSS). The method converts a set of visually inspected classifications for each galaxy into a single parameter (the 'weighted-merger-vote fraction,'fm) which describes our confidence that the system is part of an ongoing merger. We describe how fm is used to create a catalogue of 3003 visually selected pairs of merging galaxies from the SDSS in the redshift range 0.005 < z < 0.1 . We use our merger sample and values of fm applied to the SDSS Main Galaxy Spectral sample to estimate that the fraction of volume-limited (Mr < −20.55) major mergers (1/3 < M*1/M*2 < 3) in the nearby Universe is 1–3 ×C per cent, where C∼ 1.5 is a correction factor for spectroscopic incompleteness. Having visually classified the morphologies of the constituent galaxies in our mergers, we find that the spiral-to-elliptical ratio of galaxies in mergers is higher by a factor of ∼2 relative to the global population. In a companion paper, we examine the internal properties of these merging galaxies and conclude that this high spiral-to-elliptical ratio in mergers is due to a longer time-scale over which mergers with spirals are detectable compared to mergers with ellipticals.

AB - We present the largest, most homogeneous catalogue of merging galaxies in the nearby Universe obtained through the Galaxy Zoo project – an interface on the World Wide Web enabling large-scale morphological classification of galaxies through visual inspection of images from the Sloan Digital Sky Survey (SDSS). The method converts a set of visually inspected classifications for each galaxy into a single parameter (the 'weighted-merger-vote fraction,'fm) which describes our confidence that the system is part of an ongoing merger. We describe how fm is used to create a catalogue of 3003 visually selected pairs of merging galaxies from the SDSS in the redshift range 0.005 < z < 0.1 . We use our merger sample and values of fm applied to the SDSS Main Galaxy Spectral sample to estimate that the fraction of volume-limited (Mr < −20.55) major mergers (1/3 < M*1/M*2 < 3) in the nearby Universe is 1–3 ×C per cent, where C∼ 1.5 is a correction factor for spectroscopic incompleteness. Having visually classified the morphologies of the constituent galaxies in our mergers, we find that the spiral-to-elliptical ratio of galaxies in mergers is higher by a factor of ∼2 relative to the global population. In a companion paper, we examine the internal properties of these merging galaxies and conclude that this high spiral-to-elliptical ratio in mergers is due to a longer time-scale over which mergers with spirals are detectable compared to mergers with ellipticals.

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DO - 10.1111/j.1365-2966.2009.15686.x

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JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

SN - 0035-8711

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ER -

Galaxy Zoo: the fraction of merging galaxies in the SDSS and their morphologies

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