Identification of Grand-design and Flocculent spirals from SDSS using deep convolutional neural network. Issue 1 (27th October 2022)

• Record Type: Journal Article
• Authors: Sarkar, Suman; Narayanan, Ganesh; Banerjee, Arunima; Prakash, Prem
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 518:Issue 1(2023)
• Page Start: 1022
• Page End: 1040
• Publication Date: 2022-10-27
• Subjects: galaxies: spiral -- disc -- structure -- formation -- cosmology: observations -- methods: data analysis; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stac3096
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: Spiral galaxies can be classified into the Grand-designs and Flocculents based on the nature of their spiral arms. The Grand-designs exhibit almost continuous and high contrast spiral arms and are believed to be driven by stationary density waves, while the Flocculents have patchy and low-contrast spiral features and are primarily stochastic in origin. We train a deep convolutional neural network model to classify spirals into Grand-designs and Flocculents, with a testing accuracy of $\mathrm{97.2{{\ \rm per\ cent}}}$ . We then use the above model for classifying 1354 spirals from the SDSS. Out of these, 721 were identified as Flocculents, and the rest as Grand-designs . Interestingly, we find the mean asymptotic rotational velocities of our newly classified Grand-designs and Flocculents are 218 ± 86 and 146 ± 67 km s −1, respectively, indicating that the Grand-designs are mostly the high-mass and the Flocculents the intermediate-mass spirals. This is further corroborated by the observation that the mean morphological indices of the Grand-designs and Flocculents are 2.6 ± 1.8 and 4.7 ± 1.9, respectively, implying that the Flocculents primarily consist of a late-type galaxy population in contrast to the Grand-designs . Finally, an almost equal fraction of bars ∼0.3 in both the classes of spiral galaxies reveals that the presence of a bar component does not regulate the type of spiral arm hosted by a galaxy. Our results may have important implications for formation and evolution of spiral arms in galaxies.