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Table · dataset · 2022

Galaxies at 0.02<z<0.1 morphological catalog

Listed in IVOA Registry (Virtual Observatory)

We applied the image-based approach with a convolutional neural network model to the sample of low-redshifts galaxies with absolute magnitudes -24<M_r_<19.4 mag from the SDSS DR9.

Description

We divided it into two subsamples, SDSS DR9 galaxy dataset and Galaxy Zoo 2 (GZ2) dataset, considering them as the inference and training datasets, respectively. When training the CNN classifier for a more accurate result, we took into consideration only those galaxies for which GZ2's volunteers gave the most votes.

As a result, we created the morphological catalog of 315776 galaxies at 0.02<z<0.1. The CNN classifier shows the promising performance of morphological classification attaining >93 % of accuracy for five classes morphology prediction except the cigar-shaped (~75 %) and completely rounded (~83 %) galaxies. The catalog includes 27378 completely rounded, 59 194 rounded in-between, 18862 cigar-shaped, 7831 edge-on, and 23119 spiral galaxies of the inference dataset, which were first defined, as well as the galaxies from the GZ2 training sample with reassigned types and corrected types in case of the low volunteer votes (Vavilova et al., 2022KNIT...28....3V).

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As for the classification of galaxies by their detailed structural morphological features, our CNN model gives the accuracy in the range of 83.3-99.4% depending on features, a number of galaxies with the given feature in the inference dataset, and the galaxy image quality. This allowed us, for the first time, to assign the detailed morphological classification for more than 140K low-redshift galaxies. We describe in detail the adversarial validation technique as well as how we managed the optimal train-test split of galaxies from the training data set.

We have also found optimal galaxy image transformations to increase the classifier generalization ability. It can be considered as another way to improve the human bias for those galaxy images that had a poor vote classification in the GZ project. Such an approach, likely auto- immunization, when the CNN classifier trained on very good images is able to retrain bad images from the same homogeneous sample, can be considered co-planar to other methods of combating the human bias (Khramtsov et al., 2022KNIT...28....3V).

We demonstrate that implication of the CNN model with adversarial validation and adversarial image data augmentation improves classification of smaller and fainter SDSS galaxies with mr<17.7. The proposed CNN model allows solving a bunch of galaxy classification problems, for example, such as a quick selection of galaxies with a bar, bulge, ring, and other morphological features for their subsequent analysis. Galaxies at 0.02<z<0.1 morphological catalog v.2 (Vavilova et al., 2022KNIT...28....3V) is available in CSV format at ftp://ftp.mao.kiev.ua/pub/astro/cats/galaxies /galSDSSDR9zto0.1morph_classification.csv.

This Catalog is supplemented with the VizieR Online Data Catalog: SDSS galaxies morphological classification (Vavilova et al., 2021A&A...648A.122V, Cat. J/A+A/648/A122). This Catalog is also supplemented with the papers: - Machine learning technique for morphological classification of galaxies from SDSS.

II. The image-based morphological catalogs of galaxies at 0.02<z<0.1. Vavilova, I. B. ; Khramtsov, V. ; Dobrycheva, D. V. ; Vasylenko, M. Yu. ; Elyiv, A. A. ; Melnyk, O. V. Space Science and Technology, Vol. 28, No. 1, pp.03-22 (2022KNIT...28....3V). - Machine learning technique for morphological classification of galaxies from the SDSS.

III. The CNN image-based inference of detailed features. Khramtsov, V., Vavilova, I.B., Dobrycheva, D.V., Vasylenko, M.Yu., Melnyk, O.V., Elyiv, A.A., Akhmetov, V.S., Dmytrenko, A.M. Space Science and Technology, Vol. 28, No. 5, pp. 27-55 (2022KNIT...28....3V). doi.org/10.15407/knit2022.05.027

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