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A direct numerical simulation has been carried out for turbulent flow around a periodically deforming film. The film deformation is sinusoidal in the streamwise direction, whose nodes are fixed in space. The maximum amplitude of the deformation is limited within the linear sublayer. An unsteady generalized curvilinear coordinate and the collocated grid system are applied to the finite differencing of the NS equation. The computational results show that the turbulence intensities, the Reynolds shear stress and the wall-shear stress increase, in the case where the period of wall deformation is longer than the ratio of the wavelength of deformation to the fluid velocity in the buffer region. In contrast to this, these statistical quantities do not increase, in the case where the period of wall deformation is slightly shorter than the ratio. This difference is caused by the enhancement of mixing in the wall-normal direction and the modifications of the Q4 event due to the deformation. [ABSTRACT FROM AUTHOR]

We perform a stacking analysis of the H i spectra from the Arecibo Legacy Fast ALFA survey for optically selected local galaxies from the Sloan Digital Sky Survey to study the average gas fraction of galaxies at fixed stellar mass (M*) and star formation rate (SFR). We first confirm that the average gas fraction strongly depends on the stellar mass and SFR of host galaxies; massive galaxies tend to have a lower gas fraction, and actively star-forming galaxies show a higher gas fraction, which is consistent with many previous studies. Then we investigate the morphological dependence of the H i gas mass fraction at fixed M* and SFR to minimize the effects of these parameters. We use three morphological classifications based on parametric indicator (Sérsic index), nonparametric indicator (C-index), and visual inspection (smoothness from the Galaxy Zoo 2 project) on the optical image. We find that there is no significant morphological dependence of the H i gas mass fraction at fixed M* and SFR when we use the C-index. In comparison, there exists a hint of diminishment in the H i gas mass fraction for "smooth" galaxies compared with "nonsmooth" galaxies. We find that the visual smoothness is sensitive to the existence of small-scale structures in a galaxy. Our result suggests that even at fixed M* and SFR, the presence of such small-scale structures (seen in the optical image) is linked to their total H i gas content. [ABSTRACT FROM AUTHOR]

Active galactic nuclei (AGNs) are key in understanding the coevolution of galaxies and supermassive black holes (SMBHs). AGN activity is thought to affect the properties of their host galaxies via a process called "AGN feedback," which drives the coevolution. From a parent sample of 1151 z < 1 type-1 quasars from the Sloan Digital Sky Survey quasar catalog, we detected the host galaxies of 862 of them in the high-quality grizy images of the Subaru Hyper Suprime-Cam survey. The unprecedented combination of the survey area and depth allowed us to perform a statistical analysis of the quasar host galaxies, with small sample variance. We fitted the radial image profile of each quasar as a linear combination of the point spread function and the Sérsic function, decomposing the images into the quasar nucleus and the host galaxy components. We found that the host galaxies are massive, with stellar mass M star ≳ 1010  |$M_\odot$|⁠ , and are mainly located on the green valley. This trend is consistent with a scenario in which star formation in the host galaxies is suppressed by AGN feedback, that is, AGN activity may be responsible for the transition of these galaxies from the blue cloud to the red sequence. We also investigated the SMBH mass to stellar mass relation of the z < 1 quasars, and found a consistent slope with the local relation, while the SMBHs may be slightly undermassive. However, the above results are subject to our sample selection, which biases against host galaxies with low masses and/or large quasar-to-host flux ratios. [ABSTRACT FROM AUTHOR]

One of the key questions on active galactic nuclei (AGN) in galaxy clusters is how AGN could affect the formation and evolution of member galaxies and galaxy clusters in the history of the Universe. To address this issue, we investigate the dependence of AGN number fraction (f AGN) on cluster redshift (z cl) and distance from the cluster center (R |$/$| R 200). We focus on more than 27000 galaxy groups and clusters at 0.1 < z cl < 1.4 with more than 1 million member galaxies selected from the Subaru Hyper Suprime-Cam. By combining various AGN selection methods based on infrared (IR), radio, and X-ray data, we identify 2688 AGN. We find that (i) f AGN increases with z cl and (ii) f AGN decreases with R |$/$| R 200. The main contributors to the rapid increase of f AGN towards high- z and cluster center are IR- and radio-selected AGN, respectively. These results indicate that the emergence of the AGN population depends on the environment and redshift, and galaxy groups and clusters at high z play an important role in AGN evolution. We also find that cluster–cluster mergers may not drive AGN activity in at least the cluster center, while we have tentative evidence that cluster–cluster mergers could enhance AGN activity in the outskirts of (particularly massive) galaxy clusters. [ABSTRACT FROM AUTHOR]

We present ionized gas properties of nine local ultra/luminous infrared galaxies (U/LIRGs) at z < 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. [ABSTRACT FROM AUTHOR]

We investigate the cold-gas properties of massive Virgo galaxies (>109M⊙) at <3R200 (R200 is the radius where the mean interior density is 200 times the critical density) on the projected phase-space diagram with the largest archival data set to date to understand the environmental effects on galaxy evolution in the Virgo cluster. We find lower H i and H2 mass fractions and higher star formation efficiencies (SFEs) from H i and H2 in the Virgo galaxies than in the field galaxies for matched stellar masses; the Virgo galaxies generally follow the field relationships between the offset from the main sequence of the star-forming galaxies [Δ(MS)] and the gas fractions and SFEs, to the slight offset to lower gas fractions or higher SFEs compared to field galaxies at Δ(MS) < 0; lower gas fractions in galaxies with smaller clustocentric distance and velocity; and lower gas fractions in the galaxies in the W cloud, a substructure of the Virgo cluster. Our results suggest the cold-gas properties of some Virgo galaxies are affected by their environment at least at 3R200 maybe via strangulation and/or preprocesses, and H i and H2 in some galaxies are removed by ram pressure at <1.5R200. Our data cannot rule out the possibility of other processes such as strangulation and galaxy harassment accounting for gas reduction in some galaxies at <1.5R200. Future dedicated observations of a mass-limited complete sample are required for definitive conclusions. [ABSTRACT FROM AUTHOR]

We present the first discovery of dust-reddened quasars (red quasars) in the high- z universe (z > 5.6). This is a result from the Subaru High- z Exploration of Low-Luminosity Quasars (SHELLQs) project, which is based on the sensitive multi-band optical imaging data produced by the Hyper Suprime-Cam (HSC) Subaru Strategic Program survey. We identified four red quasar candidates from the 93 spectroscopically confirmed high- z quasars in the SHELLQs sample, based on detections in the Wide-field Infrared Survey Explorer (WISE) data at 3.4 and 4.6 μm (rest-frame ∼5000–6500 Å). The amount of dust reddening was estimated with spectral energy distribution (SED) fits over optical and mid-infrared wavelengths. Two of the four candidates were found to be red quasars with dust reddening of E (B − V) > 0.1. The remaining SHELLQs quasars without individual WISE detections are significantly fainter in the WISE bands and bluer than the red quasars, although we did detect them in the W1 band in a stacked image. We also conducted the same SED fits for high- z optically-luminous quasars, but no red quasar was found. This demonstrates the power of Subaru HSC to discover high- z red quasars, which are fainter than the limiting magnitudes of past surveys in the rest-frame ultraviolet, due to dust extinction. [ABSTRACT FROM AUTHOR]