Passive spiral galaxies deeply captured by Subaru Hyper Suprime-Cam

Abstract

This paper presents a thousand passive spiral galaxy samples at z = 0.01-0.3 based on a combined analysis of the Third Public Data Release of the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP PDR3) and the GALEX-SDSS-WISE Legacy Catalog (GSWLC-2). Among 54871 gri galaxy cutouts taken from the HSC-SSP PDR3 over 1072 deg 2 , we conducted a search with deep-learning morphological classification for candidates of passive spirals below the star-forming main sequence derived by UV to mid-IR SED fitting in the GSWLC-2. We then classified the candidates into 1100 passive spirals and 1141 secondary samples based on visual inspections. Most of the latter cases are considered to be passive ringed S0 or pseudo-ringed galaxies. The remainder of these secondary samples has ambiguous morphologies, including two peculiar objects with diamond-shaped stellar wings. The selected passive spirals have a similar distribution to the general quiescent galaxies on the EW Hδ -D n 4000 diagram and concentration indices. Moreover, we detected an enhanced passive fraction of spiral galaxies in X-ray clusters. Passive spirals in galaxy clusters are preferentially located in the midterm or late infall phase on the phase-space diagram, supporting the ram pressure scenario, which has been widely advocated in previous studies. The source catalog and gri-composite images are available on the HSC-SSP PDR3 website (https://hsc.mtk.nao.ac.jp/ssp/data-release/). Future updates, including integration with a citizen science project dedicated to the HSC data, will achieve more effective and comprehensive classifications.

Star-forming early-type galaxies and quiescent late-type galaxies in the local Universe

“…After visual inspection, as can be seen in Fig. 1, these galaxies are spirals with a redder view and smoother spiral arms, in agreement with the findings by Shimakawa et al (2022). Goto et al (2003) refers to the red spirals as a population in transition between red E/S0 galaxies in low-redshift clusters and blue spirals frequent in higher redshift clusters.…”

“…These galaxies were found to be dominated by old stellar populations, while their SFR is lower compared to the main population of the same morphology bin. In a more recent study by Shimakawa et al (2022) investigating a sample of 1,100 spiral galaxies with 0.01 < z < 0.3 from the Hyper Suprime-Cam Subaru Strategic Program (HSC SSP; Aihara et al 2018) found that 5% are passive, with identical characteristics (in stellar populations) to the typical Q galaxies, despite the different morphologies. These results are in quite good agreement with the corresponding Q late-type population (8%) of the LTGs we find in the GAMA sample (see bottom left panel of Fig.…”