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Galaxy Zoo: comparing the demographics of spiral arm number and a new method for correcting redshift bias

Hart, Ross E.; Bamford, Steven P.; Willett, Kyle W.; Masters, Karen L.; Cardamone, Carolin; Lintott, Chris J.; Mackay, Robert J.; Nichol, Robert C.; Rosslowe, Christopher K.; Simmons, Brooke D.; Smethurst, Rebecca J.

Authors

Ross E. Hart

Steven P. Bamford

Kyle W. Willett

Karen L. Masters

Carolin Cardamone

Chris J. Lintott

Robert J. Mackay

Robert C. Nichol

Christopher K. Rosslowe

Brooke D. Simmons

Rebecca J. Smethurst



Abstract

The majority of galaxies in the local Universe exhibit spiral structure with a variety of forms. Many galaxies possess two prominent spiral arms, some have more, while others display a many-armed flocculent appearance. Spiral arms are associated with enhanced gas content and star formation in the discs of low-redshift galaxies, so are important in the understanding of star formation in the local universe. As both the visual appearance of spiral structure, and the mechanisms responsible for it vary from galaxy to galaxy, a reliable method for defining spiral samples with different visual morphologies is required. In this paper, we develop a new debiasing method to reliably correct for redshift-dependent bias in Galaxy Zoo 2, and release the new set of debiased classifications. Using these, a luminosity-limited sample of ?18 000 Sloan Digital Sky Survey spiral galaxies is defined, which are then further sub-categorized by spiral arm number. In order to explore how different spiral galaxies form, the demographics of spiral galaxies with different spiral arm numbers are compared. It is found that whilst all spiral galaxies occupy similar ranges of stellar mass and environment, many-armed galaxies display much bluer colours than their two-armed counterparts. We conclude that two-armed structure is ubiquitous in star-forming discs, whereas many-armed spiral structure appears to be a short-lived phase, associated with more recent, stochastic star-formation activity.

Citation

Hart, R. E., Bamford, S. P., Willett, K. W., Masters, K. L., Cardamone, C., Lintott, C. J., …Smethurst, R. J. (2016). Galaxy Zoo: comparing the demographics of spiral arm number and a new method for correcting redshift bias. Monthly Notices of the Royal Astronomical Society, 461(4), https://doi.org/10.1093/mnras/stw1588

Journal Article Type Article
Acceptance Date Jun 29, 2016
Online Publication Date Jul 4, 2016
Publication Date Oct 1, 2016
Deposit Date Jan 6, 2017
Publicly Available Date Mar 29, 2024
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 0035-8711
Publisher Oxford University Press
Peer Reviewed Peer Reviewed
Volume 461
Issue 4
DOI https://doi.org/10.1093/mnras/stw1588
Keywords methods: data analysis ; galaxies: formation ; galaxies: general ; galaxies: spiral ; galaxies: structure.
Public URL https://nottingham-repository.worktribe.com/output/807915
Publisher URL http://mnras.oxfordjournals.org/content/461/4/3663

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