arXiv subjects

Kazuharu G. Himoto

Publications and source records attributed to Kazuharu G. Himoto.

3 recordsLinked to original sources

arXiv2022

Central Concentration of Asymmetric Features in Post-starburst Galaxies at $z \sim 0.8$

We present morphological analyses of Post-starburst galaxies (PSBs) at $0.7 0.8$, while only 16% (2%) of quiescent (star-forming) galaxies show such high $C_{A}$ values. Those PSBs with high $C_{A}$ have relatively low overall asymmetry of $A \sim 0.1$, but show remarkable asymmetric features near the centre. The fraction of those PSBs with high $C_{A}$ 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.

astro-ph.GA↗

arXiv2022

Optical IFU Observations of GOALS Sample with KOOLS-IFU on Seimei Telescope: Initial results of 9 U/LIRGs at $z <$ 0.04

We present ionized gas properties of 9 local ultra/luminous infrared galaxies (U/LIRGs) at $z <$ 0.04 through IFU observations with KOOLS-IFU on 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 H$β$, [OIII]$λ$5007, H$α$, [NII]$λλ$6549,6583, and [SII]$λλ$6717,6731 with a spectral resolution of $R$ = 1500-2000, which provides (i) spatially-resolved ($\sim$200-700 pc) moment map of ionized gas and (ii) diagnostics for active galactic nucleus (AGN) within the central $\sim$3--11 kpc in diameter for our sample. We find that [OIII] outflow that is expected to be driven by AGN tends to be stronger (i) towards the galactic center and (ii) as a sequence of 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.

astro-ph.GA↗

arXiv2019

Evolution of 3-dimensional Shape of Passively Evolving and Star-forming Galaxies at $z<1$

Using the HST/ACS $I_{\rm F814W}$-band data, we investigated distribution of apparent axial ratios of $\sim21000$ galaxies with $M_{V}<-20$ at $0.2 10^{11}M_{\odot}$ have $C/A\sim0.5$ irrespective of redshift. On the other hand, star-forming galaxies on the main sequence with $10^{9.5}$--$10^{11}M_{\odot}$ 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 $z\sim1$, 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 $M_{\rm star}<10^{11}M_{\odot}$ at $z<1$.

astro-ph.GA↗