赤方偏移3の原始銀河団における大質量爆発的星形成銀河及び超大質量ブラックホールの形成

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 嶋作 一大, 東京大学教授 小林 秀行, 東京大学准教授 大内 正己, 国立天文台准教授 兒玉 忠恭, 東北大学准教授 秋山 正幸University of Tokyo(東京大学

Characterizing CO Emitters in the SSA22-AzTEC26 Field

We report the physical characterization of four CO emitters detected near the bright submillimeter galaxy (SMG) SSA22-AzTEC26. We analyze the data from Atacama Large Millimeter/submillileter Array band 3, 4, and 7 observations of the SSA22-AzTEC26 field. In addition to the targeted SMG, we detect four line emitters with a signal-to-noise ratio $>5.2$ in the cube smoothed with 300 km s$^{-1}$ FWHM Gaussian filter. All four sources have NIR counterparts within 1\arcsec. We perform UV-to-FIR spectral energy distribution modeling to derive the photometric redshifts and physical properties. Based on the photometric redshifts, we reveal that two of them are CO(2-1) at redshifts of 1.113 and 1.146 and one is CO(3-2) at $z=2.124$. The three sources are massive galaxies with a stellar mass $\gtrsim10^{10.5}M_\odot$, but have different levels of star formation. Two lie within the scatter of the main sequence (MS) of star-forming galaxies at $z\sim1-2$, and the most massive galaxy lies significantly below the MS. However, all three sources have a gas fraction within the scatter of the MS scaling relation. This shows that a blind CO line search can detect massive galaxies with low specific star formation rates that still host large gas reservoirs and that it also complements targeted surveys, suggesting later gas acquisition and the need for other mechanisms in addition to gas consumption to suppress star formation.Comment: accepted for publication in the Astrophysical Journa

Central concentration of warm and dense molecular gas in a strongly lensed submillimeter galaxy at z=6

We report the detection of the CO(12-11) line emission toward G09-83808 (or H-ATLAS J090045.4+004125), a strongly-lensed submillimeter galaxy at $z = 6.02$, with Atacama Large Millimeter/submillimeter Array observations. Combining previously detected [O III]$\,88\:\mathrm{\mu m}$, [N II]$\,205\:\mathrm{\mu m}$, and dust continuum at 0.6$\:$mm and 1.5$\:$mm, we investigate the physical properties of the multi-phase interstellar medium in G09-83808. A source-plane reconstruction reveals that the region of the CO(12-11) emission is compact ($R_\mathrm{{e, CO}}=0.49^{+0.29}_{-0.19}\,\mathrm{kpc}$) and roughly coincides with that of the dust continuum. Non-local thermodynamic equilibrium radiative transfer modeling of CO spectral-line energy distribution reveals that most of the CO(12-11) emission comes from a warm (kinetic temperature of $T_{\mathrm{kin}}=320\pm170\:$K) and dense ($\log(n_{\mathrm{H2}}/\mathrm{cm^{-3}})=5.4\pm0.6$) gas, indicating that the warm and dense molecular gas is concentrated in the central 0.5-kpc region. The luminosity ratio in G09-83808 is estimated to be $L_\mathrm{{CO(12-11)}} / L_\mathrm{{CO(6-5)}}=1.1\pm0.2$. The high ratio is consistent with those in local active galactic nuclei (AGNs) and $6<z<7$ quasars, the fact of which implies that G09-83808 would be a good target to explore dust-obscured AGNs in the epoch of reionization. In the reconstructed [O III]$\,88\:\mathrm{\mu m}$ and [N II]$\,205\:\mathrm{\mu m}$ cubes, we also find that a monotonic velocity gradient is extending over the central starburst region by a factor of two and that star-forming sub-components exist. High-resolution observations of bright [C II]$\,158\:\mathrm{\mu m}$ line emissions will enable us to characterize the kinematics of a possible rotating disk and the nature of the sub-components.Comment: 13 pages, 11 figures, accepted for publication in PAS

ALMA Lensing Cluster Survey: Properties of Millimeter Galaxies Hosting X-ray Detected Active Galactic Nuclei

We report the multi-wavelength properties of millimeter galaxies hosting X-ray detected active galactic nuclei (AGNs) from the ALMA Lensing Cluster Survey (ALCS). ALCS is an extensive survey of well-studied lensing clusters with ALMA, covering an area of 133 arcmin$^2$ over 33 clusters with a 1.2 mm flux-density limit of ${\sim}$60 $\mathrm{\mu Jy}$ ($1\sigma$). Utilizing the archival data of Chandra, we identify three AGNs at $z=$1.06, 2.09, and 2.84 among the 180 millimeter sources securely detected in the ALCS (of which 155 are inside the coverage of Chandra). The X-ray spectral analysis shows that two AGNs are not significantly absorbed ($\log N_{\mathrm{H}}/\mathrm{cm}^{-2} < 23$), while the other shows signs of moderate absorption ($\log N_{\mathrm{H}}/\mathrm{cm}^{-2}\sim 23.5$). We also perform spectral energy distribution (SED) modelling of X-ray to millimeter photometry. We find that our X-ray AGN sample shows both high mass accretion rates (intrinsic 0.5--8 keV X-ray luminosities of ${\sim}10^{\text{44--45}}\,\mathrm{erg\ s^{-1}}$) and star-formation rates (${\gtrsim}100\,M_{\odot}\,\mathrm{yr}^{-1}$). This demonstrates that a wide-area survey with ALMA and Chandra can selectively detect intense growth of both galaxies and supermassive black holes (SMBHs) in the high-redshift universe.Comment: 14 pages, 3 figures, 2 table

Detection of the Far-infrared [O III] and Dust Emission in a Galaxy at Redshift 8.312: Early Metal Enrichment in the Heart of the Reionization Era

We present the Atacama Large Millimeter/submillimeter Array (ALMA) detection of the [O III] 88 $\mu$m line and rest-frame 90 $\mu$m dust continuum emission in a Y-dropout Lyman break galaxy (LBG), MACS0416_Y1, lying behind the Frontier Field cluster MACS J0416.1-2403. This [O III] detection confirms the LBG with a spectroscopic redshift of $z = 8.3118 \pm 0.0003$, making this object one of the furthest galaxies ever identified spectroscopically. The observed 850 $\mu$m flux density of $137 \pm 26$ $\mu$Jy corresponds to a de-lensed total infrared (IR) luminosity of $L_{\rm IR} = (1.7 \pm 0.3) \times 10^{11} L_{\odot}$ if assuming a dust temperature of $T_{\rm dust} = 50$ K and an emissivity index of $\beta = 1.5$, yielding a large dust mass of $4 \times 10^6 M_{\odot}$. The ultraviolet-to-far IR spectral energy distribution modeling where the [O III] emissivity model is incorporated suggests the presence of a young ($\tau_{\rm age} \approx 4$ Myr), star-forming (SFR $\approx 60 M_{\odot}$ yr$^{-1}$), moderately metal-polluted ($Z \approx 0.2 Z_{\odot}$) stellar component with a mass of $M_{\rm star} = 3 \times 10^8 M_{\odot}$. An analytic dust mass evolution model with a single episode of star-formation does not reproduce the metallicity and dust mass in $\tau_{\rm age} \approx 4$ Myr, suggesting a pre-existing evolved stellar component with $M_{\rm star} \sim 3 \times 10^9 M_{\odot}$ and $\tau_{\rm age} \sim 0.3$ Gyr as the origin of the dust mass.Comment: Accepted by ApJ. 18 pages, 10 figures, 5 table