ALMA 0.5 kpc Resolution Spatially Resolved Investigations of Nuclear Dense Molecular Gas Properties in Nearby Ultraluminous Infrared Galaxies Based on HCN and HCO+^{+} Three Transition Line Data

We present the results of our ALMA $\lesssim$0.5 kpc-resolution dense molecular line (HCN and HCO$^{+}$ J=2-1, J=3-2, and J=4-3) observations of 12 nearby (ultra)luminous infrared galaxies ([U]LIRGs). After matching beam sizes of all molecular line data to the same values in all (U)LIRGs, we derive molecular line flux ratios, by extracting spectra in the central 0.5, 1, 2 kpc circular regions, and 0.5-1 and 1-2 kpc annular regions. Based on non-LTE model calculations, we quantitatively confirm that the innermost ($\lesssim$0.5 kpc) molecular gas is very dense ($\gtrsim$10$^{5}$ cm$^{-3}$) and warm ($\gtrsim$300 K) in ULIRGs, and that in one LIRG is also modestly dense (10$^{4-5}$ cm$^{-3}$) and warm ($\sim$100 K). We then investigate the spatial variation of the HCN-to-HCO$^{+}$ flux ratios and high-J to low-J flux ratios of HCN and HCO$^{+}$. A subtle sign of decreasing trend of these ratios from the innermost ($\lesssim$0.5 kpc) to outer nuclear (0.5-2 kpc) region is discernible in a significant fraction of the observed ULIRGs. For two AGN-hosting ULIRGs which display the trend most clearly, we find based on a Bayesian approach that the HCN-to-HCO$^{+}$ abundance ratio and gas kinetic temperature systematically increase from the outer nuclear to the innermost region. We suggest that this trend comes from potential AGN effects, because no such spatial variation is found in a starburst-dominated LIRG.Comment: 62 pages, 29 figures. ApJ accepted. Higher resolution version is available at http://www2.nao.ac.jp/~masaimanishi/Aph/ImanishiULIRG500pcH.pd

Dense Molecular Gas Properties of the Central Kpc of Nearby Ultraluminous Infrared Galaxies Constrained by ALMA Three Transition-line Observations

We report the results of ALMA 1-2 kpc-resolution, three rotational transition line (J=2-1, J=3-2, and J=4-3) observations of multiple dense molecular gas tracers (HCN, HCO$^{+}$, and HNC) for ten nearby (ultra)luminous infrared galaxies ([U]LIRGs). Following the matching of beam sizes to 1-2 kpc for each (U)LIRG, the high-J to low-J transition-line flux ratios of each molecule and the emission line flux ratios of different molecules at each J transition are derived. We conduct RADEX non-LTE model calculations and find that, under a wide range of gas density and kinetic temperature, the observed HCN-to-HCO$^{+}$ flux ratios in the overall (U)LIRGs are naturally reproduced with enhanced HCN abundance compared to HCO$^{+}$. Thereafter, molecular gas properties are constrained primarily through the use of HCN and HCO$^{+}$ data and the adoption of fiducial values for the HCO$^{+}$ column density and HCN-to-HCO$^{+}$ abundance ratio. We quantitatively confirm the following: (1) Molecular gas at the (U)LIRGs' nuclei is dense ($\gtrsim$10$^{3-4}$ cm$^{-3}$) and warm ($\gtrsim$100 K). (2) Molecular gas density and temperature in nine ULIRGs' nuclei are significantly higher than that of one LIRG's nucleus. (3) Molecular gas in starburst-dominated sources tends to be less dense and cooler than ULIRGs with luminous AGN signatures. For six selected sources, we also apply a Bayesian approach by freeing all parameters and support the above main results. Our ALMA 1-2 kpc resolution, multiple transition-line data of multiple molecules are a very powerful tool for scrutinizing the properties of molecular gas concentrated around luminous energy sources in nearby (U)LIRGs' nuclei.Comment: 42 pages, 13 figures. ApJ accepte

Synthesizing sea surface height change including seismic waves and tsunami using a dynamic rupture scenario of anticipated Nankai trough earthquakes

The development of offshore observation technology will provide researchers with tsunami records from within an earthquake focal area, but this will create new problems. Because seismic waves coexist with tsunami inside a focal area, the seismic waves could act as noise for the tsunami signal. This study shows an efficient method to calculate sea surface height change caused by an earthquake including both seismic waves and tsunami. Simulation results indicate that seismic waves overlap with tsunami; both affect the change in sea surface height although most previous tsunami studies have neglected the contribution of seismic waves. We also numerically simulated the sea-surface displacement wavefield and hypothesized results for an anticipated rupture scenario of a huge earthquake that may possibly occur in the Nankai Trough, Japan. The synthesized record could be used to evaluate the performance of a real-time tsunami prediction method. Additionally, we discussed the similarity and difference between two kinds of tsunami waveforms: the displacement of the sea surface and the pressure change at the sea bottom. Although seismic waves appeared in both waveforms, the contribution of seismic waves was lower in the displacement at the sea surface than in the pressure change at the sea bottom

An Accurate Separation of Floating-Body and Self-Heating Effects for High-Frequency Characterization of SOI MOSFET's

Abstract -In this paper, we present an accurate highfrequency characterization of AC output conductance method to separate SOI specific floating-body effects (FBE) and self-heating effects (SHE) from DC I-V data. In DC measurement, the transistor TEG pattern dependence is essential in view of the SOI body potential, which is confirmed by 3-dimensional device simulation. In AC measurement, the power of smallsignal is the most critical issue for removing the FBE and SHE components

一酸化炭素近赤外線吸収バンドを用いた活動銀河核近傍の高温分子ガスの研究

学位の種別: 課程博士審査委員会委員 : （主査）東京大学准教授 馬場 彩, 東京大学教授 海老沢 研, 東京大学教授 河野 孝太郎, 東京大学教授 吉田 直紀, 東京大学教授 満田 和久University of Tokyo(東京大学

SARS-CoV-2 genome clusters analyzed by Deep Learning

We report on a method for analyzing the variant of coronavirus genes using autoencoder. Since coronaviruses have mutated rapidly and generated a large number of genotypes, an appropriate method for understanding the entire population is required. The method using autoencoder meets this requirement and is suitable for understanding how and when the variants emarge and disappear. For the over 30,000 SARS-CoV-2 ORF1ab gene sequences sampled globally from December 2019 to February 2021, we were able to represent a summary of their characteristics in a 3D plot and show the expansion, decline, and transformation of the virus types over time and by region. Based on ORF1ab genes, the SARS-CoV-2 viruses were classified into five major types (A, B, C, D, and E in the order of appearance): the virus type that originated in China at the end of 2019 (type A) practically disappeared in June 2020; two virus types (types B and C) have emerged in the United States and Europe since February 2020, and type B has become a global phenomenon. Type C is only prevalent in the U.S. and is suspected to be associated with high mortality, but this type also disappeared at the end of June. Type D is only found in Australia. Currently, the epidemic is dominated by types B and E

AGN X-ray irradiation of CO gas in NGC 2110 revealed by ChandraChandra and ALMA

We report spatial distributions of the Fe-K$\alpha$ line at 6.4 keV and the CO($J$ = 2--1) line at 230.538 GHz in NGC 2110, which are respectively revealed by $Chandra$ and ALMA at $\approx$ 0.5 arcsec. A $Chandra$ 6.2--6.5 keV-to-3.0--6.0 keV image suggests that the Fe-K$\alpha$ emission extends preferentially in a northwest-to-southeast direction out to $\sim$ 3 arcsec, or 500 pc, on each side. Spatially-resolved spectral analyses support this by finding significant Fe-K$\alpha$ emission lines only in northwest and southeast regions. Moreover, their equivalent widths are found $\sim$ 1.5 keV, indicative for the fluorescence by nuclear X-ray irradiation as the physical origin. By contrast, CO($J$ = 2--1) emission is weak therein. For quantitative discussion, we derive ionization parameters by following an X-ray dominated region (XDR) model. We then find them high enough to interpret the weakness as the result of X-ray dissociation of CO and/or H$_2$. Another possibility also remains that CO molecules follow a super-thermal distribution, resulting in brighter emission in higher-$J$ lines. Further follow-up observations are encouraged to draw a conclusion on what predominantly changes the inter-stellar matter properties, and whether the X-ray irradiation eventually affects the surrounding star formation as an AGN feedback.Comment: 15 pages, 11 figures, 3 tables. Accepted for publication in Ap