Using the HST/ACS I F814W -band data, we investigated distribution of apparent axial ratios of ∼ 21000 galaxies with M V < −20 at 0.2 < z < 1.0 in the COSMOS field as a function of stellar mass, specific star formation rate (sSFR), and redshift. We statistically estimated intrinsic 3-dimensional shapes of these galaxies by fitting the axial-ratio distribution with triaxial ellipsoid models characterized by face-on (middle-to-long) and edge-on (short-to-long) axial ratios B/A and C/A. We found that the transition from thin disk to thick spheroid occurs at ∆MS ∼ −1 dex, i.e., 10 times lower sSFR than that of the main sequence for galaxies with M star = 10 10 -10 11 M ⊙ at 0.2 < z < 1.0. Furthermore, the intrinsic thickness (C/A) of passively evolving galaxies with M star = 10 10 -10 11 M ⊙ significantly decreases with time from C/A ∼ 0.40 -0.50 at z ∼ 0.8 to C/A ∼ 0.33 -0.37 at z ∼ 0.4, while those galaxies with M star > 10 11 M ⊙ have C/A ∼ 0.5 irrespective of redshift. On the other hand, star-forming galaxies on the main sequence with 10 9.5 -10 11 M ⊙ show no significant evolution in their shape at 0.2 < z < 1.0, but their thickness depends on stellar mass; more massive star-forming galaxies tend to have lower C/A (thinner shape) than low-mass ones. These results suggest that some fraction of star-forming galaxies with a thin disk, which started to appear around z ∼ 1, quench their star formation without violent morphological change, and these newly added quiescent galaxies with a relatively thin shape cause the significant evolution in the axial-ratio distribution of passively evolving galaxies with M star < 10 11 M ⊙ at z < 1.

We present ionized gas properties of nine local ultra/luminous infrared galaxies (U/LIRGs) at z &lt; 0.04 through Integral Field Unit (IFU) observations with KOOLS-IFU on the Seimei Telescope. The observed targets are drawn from the Great Observatories All-sky LIRG Survey (GOALS), covering a wide range of merger stages. We successfully detect emission lines such as Hβ, [O iii]λ5007, Hα, [N ii]λλ6549, 6583, and [S ii]λλ6717, 6731 with a spectral resolution of R = 1500–2000, which provides (i) a spatially resolved (∼200–700 pc) moment map of ionized gas and (ii) diagnostics for an active galactic nucleus (AGN) within the central ∼3–11 kpc in diameter for our sample. We find that the [O iii] outflow that is expected to be driven by an AGN tends to be stronger (i) towards the galactic center and (ii) as a sequence of the merger stage. In particular, the outflow strength in the late-stage (stage D) mergers is about 1.5 times stronger than that in the early-state (stage B) mergers, which indicates that galaxy mergers could induce AGN-driven outflow and play an important role in the co-evolution of galaxies and supermassive black holes.

We present morphological analyses of Post-starburst galaxies (PSBs) at 0.7 &lt; z &lt; 0.9 in the COSMOS field. We fitted ultraviolet to mid-infrared multi-band photometry of objects with i &lt; 24 from COSMOS2020 catalogue with population synthesis models assuming non-parametric, piece-wise constant function of star formation history, and selected 94 those galaxies that have high specific star formation rates (SSFRs) of more than 10−9.5 yr−1 in 321–1000 Myr before observation and an order of magnitude lower SSFRs within recent 321 Myr. We devised a new non-parametric morphological index which quantifies concentration of asymmetric features, CA, and measured it as well as concentration C and asymmetry A on the Hubble Space Telescope /Advanced Camera for Surveys IF814W-band images. While relatively high C and low A values of PSBs are similar with those of quiescent galaxies rather than star-forming galaxies, we found that PSBs show systematically higher values of CA than both quiescent and star-forming galaxies; 36% of PSBs have log CA &gt; 0.8, while only 16% (2%) of quiescent (star-forming) galaxies show such high CA values. Those PSBs with high CA have relatively low overall asymmetry of A ∼ 0.1, but show remarkable asymmetric features near the centre. The fraction of those PSBs with high CA increases with increasing SSFR in 321–1000 Myr before observation rather than residual on-going star formation. These results and their high surface stellar mass densities suggest that those galaxies experienced a nuclear starburst in the recent past, and processes that cause such starbursts could lead to the quenching of star formation through rapid gas consumption, supernova/AGN feedback, and so on.

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