山田 亨

Abstract We present the study on the relationship between supermassive black holes (SMBHs) and their host galaxies using our variability-selected active galactic nuclei (AGNs) sample (i _AB ≤ 25.9 and z ≤ 4.5) constructed from the Hyper Suprime-Cam Subaru Strategic Program Ultradeep survey in the COSMOS field. We estimated the black hole (BH) mass (M _BH = 10^5.5−10 M _⊙) based on the single-epoch virial method and the total stellar mass (M _star = 10¹⁰⁻¹² M _⊙) by separating the AGN component with spectral energy distribution fitting. We found that the redshift evolution of the BH–stellar mass ratio (M _BH/M _star) depends on the M _BH, which is caused by no significant correlation between M _BH and M _star. Variable AGNs with massive SMBHs (M _BH > 10⁹ M _⊙) at 1.5 < z < 3 show considerably higher BH–stellar mass ratios (> ∼1%) than the BH–bulge ratios (M _BH/M _bulge) observed in the local Universe for the same BH range. This implies that there is a typical growth path of massive SMBHs, which is faster than the formation of the bulge component as final products seen in the present day. For the low-mass SMBHs (M _BH < 10⁸ M _⊙) at 0.5 < z < 3, on the other hand, variable AGNs show similar BH–stellar mass ratios with the local objects (∼0.1%), but smaller than those observed at z > 4. We interpret that host galaxies harboring less massive SMBHs at intermediate redshift have already acquired sufficient stellar mass, although high-z galaxies are still in the early stage of galaxy formation relative to those at the intermediate/local Universe.

Abstract We report the detection of an ionized gas outflow from an X-ray active galactic nucleus hosted in a massive quiescent galaxy in a protocluster at z = 3.09 (J221737.29+001823.4). It is a type-2 QSO with broad (W₈₀ > 1000 km s⁻¹) and strong ($\mathrm{log}({L}_{[\mathrm{OIII}]}$/erg s⁻¹) ≈ 43.4) [O iii]λλ 4959,5007 emission lines detected by slit spectroscopy in three-position angles using Multi-Object Infra-Red Camera and Spectrograph (MOIRCS) on the Subaru telescope and the Multi-Object Spectrometer For Infra-Red Exploration (MOSFIRE) on the Keck-I telescope. In the all slit directions, [O iii] emission is extended to ∼15 physical kpc and indicates a powerful outflow spreading over the host galaxy. The inferred ionized gas mass outflow rate is 22 ± 3 M_⊙ yr⁻¹. Although it is a radio source, according to the line diagnostics using Hβ, [O ii], and [O iii], photoionization by the central QSO is likely the dominant ionization mechanism rather than shocks caused by radio jets. On the other hand, the spectral energy distribution of the host galaxy is well characterized as a quiescent galaxy that has shut down star formation several hundred Myr ago. Our results suggest a scenario that QSOs are powered after the shutdown of the star formation and help complete the quenching of massive quiescent galaxies at high redshift.

<title>Abstract</title> Morphological studies are crucial to investigate the connections between active galactic nucleus (AGN) activities and the evolution of galaxies. Substantial studies have found that radiative-mode AGNs primarily reside in disk galaxies, questioning the merger-driven mechanism of AGN activities. In this study, through Sérsic profile fitting and nonparametric morphological parameter measurements, we investigated the morphology of host galaxies of 485 optical variability-selected low-luminosity AGNs at <italic>z</italic> ≲ 4.26 in the COSMOS field. We analyzed high-resolution images of the Hubble Space Telescope to measure these morphological parameters. We only successfully measured the morphological parameters for 76 objects and most AGN hosts (∼70%) were visually compact point-like sources. We examined the obtained morphological information as a function of redshift and compared them with literature data. We found that these AGN host galaxies showed no clear morphological preference. However, the merger rate increased with higher host star formation rate and AGN luminosity. Interestingly, we found ongoing star formation consistent with the typical star-forming populations in both elliptical and spiral galaxies, while these two types of galaxies were more symmetric than normal star-forming galaxies. These results suggest that optical variability-selected AGNs have higher probabilities to reside in elliptical galaxies than infrared-selected AGNs, whose host galaxies have a strong disk dominance, and support recent findings that the AGN feedback can enhance star-forming activities in host galaxies.

<title>Abstract</title> We use the SPace Infrared telescope for Cosmology and Astrophysics (<italic>SPICA</italic>) project as a template to demonstrate how deep spectrophotometric surveys covering large cosmological volumes over extended fields (1–<inline-formula> <alternatives> <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S1323358021000138_inline1.png" /> <tex-math> $15\, \rm{deg^2}$ </tex-math> </alternatives> </inline-formula>) with a mid-IR imaging spectrometer (17–<inline-formula> <alternatives> <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S1323358021000138_inline2.png" /> <tex-math> $36\, \rm{\rm{\upmu m } }$ </tex-math> </alternatives> </inline-formula>) in conjunction with deep <inline-formula> <alternatives> <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S1323358021000138_inline3.png" /> <tex-math> $70\, \rm{\rm{\upmu m } }$ </tex-math> </alternatives> </inline-formula> photometry with a far-IR camera, at wavelengths which are not affected by dust extinction can answer the most crucial questions in current galaxy evolution studies. A SPICA-like mission will be able for the first time to provide an unobscured three-dimensional (3D, i.e. <italic>x</italic>, <italic>y</italic>, and redshift <italic>z</italic>) view of galaxy evolution back to an age of the universe of less than <inline-formula> <alternatives> <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S1323358021000138_inline4.png" /> <tex-math> $\sim$ </tex-math> </alternatives> </inline-formula> 2 Gyrs, in the mid-IR rest frame. This survey strategy will produce a full census of the Star Formation Rate (SFR) in the universe, using polycyclic aromatic hydrocarbons (PAH) bands and fine-structure ionic lines, reaching the characteristic knee of the galaxy luminosity function, where the bulk of the population is distributed, at any redshift up to <inline-formula> <alternatives> <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S1323358021000138_inline5.png" /> <tex-math> $z \sim 3.5$ </tex-math> </alternatives> </inline-formula>. Deep follow-up pointed spectroscopic observations with grating spectrometers onboard the satellite, across the full IR spectral range (17–<inline-formula> <alternatives> <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S1323358021000138_inline6.png" /> <tex-math> $210\, \rm{\rm{\upmu m } }$ </tex-math> </alternatives> </inline-formula>), would simultaneously measure Black Hole Accretion Rate (BHAR), from high-ionisation fine-structure lines, and SFR, from PAH and low- to mid-ionisation lines in thousands of galaxies from solar to low metallicities, down to the knee of their luminosity functions. The analysis of the resulting atlas of IR spectra will reveal the physical processes at play in evolving galaxies across cosmic time, especially its heavily dust-embedded phase during the <italic>activity peak</italic> at the cosmic noon (<inline-formula> <alternatives> <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S1323358021000138_inline7.png" /> <tex-math> $z \sim 1$ </tex-math> </alternatives> </inline-formula>–3), through IR emission lines and features that are insensitive to the dust obscuration.

<title>Abstract</title>We investigate the stellar population of star-forming galaxies at <italic>z</italic> ∼ 4 by focusing on their slope of rest-frame ultraviolet continuum called UV spectral slope <italic>β</italic>. We analyze the sample of bright Lyman Break Galaxies (LBGs) with Subaru/<italic>i</italic>′≤26.0in the Subaru/XMM-Newton Deep Survey field. Our detailed SED fitting analysis indicates that the LBGs with observed UV slope &gt; −1.7, , Av &gt; 1.0, and intrinsic UV slope &lt; −2.5 are the intrinsically active star-forming galaxies with star formation rates larger than a few × 10² M_⊙yr⁻¹. A significant fraction of the UV-selected LBGs at <italic>z</italic> ∼ 4 is on-going active and dust obscured star-forming galaxies.

Cosmological simulations predict that the Universe contains a network of intergalactic gas filaments, within which galaxies form and evolve. However, the faintness of any emission from these filaments has limited tests of this prediction. We report the detection of rest-frame ultraviolet Lyman-α radiation from multiple filaments extending more than one megaparsec between galaxies within the SSA22 protocluster at a redshift of 3.1. Intense star formation and supermassive black-hole activity is occurring within the galaxies embedded in these structures, which are the likely sources of the elevated ionizing radiation powering the observed Lyman-α emission. Our observations map the gas in filamentary structures of the type thought to fuel the growth of galaxies and black holes in massive protoclusters.

<title>ABSTRACT</title> We present the analysis of stellar binary microlensing event OGLE-2015-BLG-0060 based on observations obtained from 13 different telescopes. Intensive coverage of the anomalous parts of the light curve was achieved by automated follow-up observations from the robotic telescopes of the Las Cumbres Observatory. We show that, for the first time, all main features of an anomalous microlensing event are well covered by follow-up data, allowing us to estimate the physical parameters of the lens. The strong detection of second-order effects in the event light curve necessitates the inclusion of longer-baseline survey data in order to constrain the parallax vector. We find that the event was most likely caused by a stellar binary-lens with masses $M_{\star 1} = 0.87 \pm 0.12 \, \mathrm{M}_{\odot }$ and $M_{\star 2} = 0.77 \pm 0.11 \, \mathrm{M}_{\odot }$. The distance to the lensing system is 6.41 ± 0.14 kpc and the projected separation between the two components is 13.85 ± 0.16 au. Alternative interpretations are also considered.

We present the analysis of the binary-microlensing event OGLE-2014-BLG-0289. The event light curve exhibits very unusual five peaks where four peaks were produced by caustic crossings and the other peak was produced by a cusp approach. It is found that the quintuple-peak features of the light curve provide tight constraints on the source trajectory, enabling us to precisely and accurately measure the microlensing parallax $\pi_{\rm E}$. Furthermore, the three resolved caustics allow us to measure the angular Einstein radius $\thetae$. From the combination of $\pi_{\rm E}$ and $\thetae$, the physical lens parameters are uniquely determined. It is found that the lens is a binary composed of two M dwarfs with masses $M_1 = 0.52 \pm 0.04\ M_\odot$ and $M_2=0.42 \pm 0.03\ M_\odot$ separated in projection by $a_\perp = 6.4 \pm 0.5$ au. The lens is located in the disk with a distance of $D_{\rm L} = 3.3 \pm 0.3$~kpc. It turns out that the reason for the absence of a lensing signal in the {\it Spitzer} data is that the time of observation corresponds to the flat region of the light curve.

We report the discovery of a planet-mass companion to the microlens OGLE-2016-BLG-0263L. Unlike most low-mass companions that were detected through perturbations to the smooth and symmetric light curves produced by the primary, the companion was discovered through the channel of a repeating event, in which the companion itself produced its own single-mass light curve after the event produced by the primary had ended. Thanks to the continuous coverage of the second peak by high-cadence surveys, the possibility of the repeating nature due to source binarity is excluded with a $96\%$ confidence level. The mass of the companion estimated by a Bayesian analysis is $M_{\rm p}=4.1_{-2.5}^{+6.5}\ M_{\rm J}$. The projected primary-companion separation is $a_\perp = 6.5^{+1.3}_{-1.9}$ au. The ratio of the separation to the snow-line distance of $a_\perp/a_{\rm sl}\sim 15.4$ corresponds to the region beyond Neptune, the outermost planet of the solar system. We discuss the importance of high-cadence surveys in expanding the range of microlensing detections of low-mass companions and future space-based microlensing surveys.

We present the analysis of the binary gravitational microlensing event MOA-2015-BLG-020. The event has a fairly long timescale (about 63 days) and thus the light curve deviates significantly from the lensing model that is based on the rectilinear lens-source relative motion. This enables us to measure the microlensing parallax through the annual parallax effect. The microlensing parallax parameters constrained by the ground-based data are confirmed by the Spitzer observations through the satellite parallax method. By additionally measuring the angular Einstein radius from the analysis of the resolved caustic crossing, the physical parameters of the lens are determined. It is found that the binary lens is composed of two dwarf stars with masses $M_1 = 0.606 \pm 0.028M_\odot$ and $M_2 = 0.125 \pm 0.006M_\odot$ in the Galactic disk. Assuming the source star is at the same distance as the bulge red clump stars, we find the lens is at a distance $D_L = 2.44 \pm 0.10 kpc$. In the end, we provide a summary and short discussion of all published microlensing events in which the annual parallax effect is confirmed by other independent observations.

We report the discovery of a binary composed of two brown dwarfs, based on the analysis of the microlensing event OGLE-2016-BLG-1469. Thanks to detection of both finite-source and microlens-parallax effects, we are able to measure both the masses $M_1\sim 0.05\ M_\odot$, $M_2\sim 0.01\ M_\odot$, and distance $D_{\rm L} \sim 4.5$ kpc, as well as the projected separation $a_\perp \sim 0.33$ au. This is the third brown-dwarf binary detected using the microlensing method, demonstrating the usefulness of microlensing in detecting field brown-dwarf binaries with separations less than 1 au.

We report the discovery and the analysis of the planetary microlensing event, OGLE-2013-BLG-1761. There are some degenerate solutions in this event because the planetary anomaly is only sparsely sampled. But the detailed light curve analysis ruled out all stellar binary models and shows that the lens to be a planetary system. There is the so-called close/wide degeneracy in the solutions with the planet/host mass ratio of $q \sim (7.5 \pm 1.5) \times 10^{-3}$ and $q \sim (9.3 \pm 2.9) \times 10^{-3}$ with the projected separation in Einstein radius units of $s = 0.95$ (close) and $s = 1.19$ (wide), respectively. The microlens parallax effect is not detected but the finite source effect is detected. Our Bayesian analysis indicates that the lens system is located at $D_{\rm L}=6.9_{-1.2}^{+1.0} \ {\rm kpc}$ away from us and the host star is an M/K-dwarf with the mass of $M_{\rm L}=0.33_{-0.18}^{+0.32} \ M_{\odot}$ orbited by a super-Jupiter mass planet with the mass of $m_{\rm P}=2.8_{-1.5}^{+2.5} \ M_{\rm Jup}$ at the projected separation of $a_{\perp}=1.8_{-0.5}^{+0.5} \ {\rm AU}$. The preference of the large lens distance in the Bayesian analysis is due to the relatively large observed source star radius. The distance and other physical parameters can be constrained by the future high resolution imaging by ground large telescopes or HST. If the estimated lens distance is correct, this planet provides another sample for testing the claimed deficit of planets in the Galactic bulge.

In the process of analyzing an observed light curve, one often confronts various scenarios that can mimic the planetary signals causing difficulties in the accurate interpretation of the lens system. In this paper, we present the analysis of the microlensing event OGLE-2016-BLG-0733. The light curve of the event shows a long-term asymmetric perturbation that would appear to be due to a planet. From the detailed modeling of the lensing light curve, however, we find that the perturbation originates from the binarity of the source rather than the lens. This result demonstrates that binary sources with roughly equal-luminosity components can mimic long-term perturbations induced by planets with projected separations near the Einstein ring. The result also represents the importance of the consideration of various interpretations in planet-like perturbations and of high-cadence observations for ensuring the unambiguous detection of the planet.