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J/MNRAS/461/3663       Galaxy Zoo 2: new classification            (Hart+, 2016)
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	table1.dat
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Query from: http://vizier.cds.unistra.fr/viz-bin/VizieR?-source=J/MNRAS/461/3663
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Beginning of ReadMe : J/MNRAS/461/3663 Galaxy Zoo 2: new classification (Hart+, 2016) ================================================================================ Galaxy Zoo: comparing the demographics of spiral arm number and a new method for correcting redshift bias. Hart R.E., Bamford S.P., Willett K.W., Masters K.L., Cardamone C., Lintott C.J., Mackay R.J., Nichol R.C., Rosslowe C.K., Simmons B.D., Smethurst R.J. <Mon. Not. R. Astron. Soc., 461, 3663-3682 (2016)> =2016MNRAS.461.3663H (SIMBAD/NED BibCode) ================================================================================ ADC_Keywords: Surveys ; Galaxies, photometry ; Photometry, SDSS ; Morphology Keywords: methods: data analysis - galaxies: formation - galaxies: general - galaxies: spiral - galaxies: structure 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  18000 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. Description: We make use of morphological information from the public data release of Galaxy Zoo 2. The galaxies classified by GZ2 were taken from the SDSS Data Release 7 (DR7; Abazajian et al. 2009ApJS..182..543A). The SDSS main galaxy sample is an r-band selected sample of galaxies in the legacy imaging area targeted for spectroscopic follow-up (Strauss et al., 2002AJ....124.1810S) The GZ2 sample contains essentially all well-resolved galaxies in DR7 down to a limiting absolute magnitude of m_r_<=17, supplemented by additional sets of galaxies in Stripe 82 for which deeper, co-added imaging exists (see W13 (Willett et al., 2013MNRAS.435.2835W, Cat. J/MNRAS/435/2835) for details). In this paper, we only consider galaxies with m_r_<=17 that were classified in normal-depth SDSS imaging and which have DR7 spectroscopic redshifts. We refer to this as our full sample, containing 228201 galaxies, to which the debiasing procedure described in Section 3.3 is applied.