Browsing by Author "Umehata, Hideki"

Now showing 1 - 6 of 6
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    A variable active galactic nucleus at z=2.06 triply-imaged by the galaxy cluster MACS J0035.4-2015
    (2023) Furtak, Lukas J.; Mainali, Ramesh; Zitrin, Adi; Plat, Adele; Fujimoto, Seiji; Donahue, Megan; Nelson, Erica J.; Bauer, Franz E.; Uematsu, Ryosuke; Caminha, Gabriel B.; Andrade-Santos, Felipe; Bradley, Larry D.; Caputi, Karina, I; Charlot, Stephane; Chevallard, Jacopo; Coe, Dan; Curtis-Lake, Emma; Espada, Daniel; Frye, Brenda L.; Knudsen, Kirsten K.; Koekemoer, Anton M.; Kohno, Kotaro; Kokorev, Vasily; Laporte, Nicolas; Lee, Minju M.; Lemaux, Brian C.; Magdis, Georgios E.; Sharon, Keren; Stark, Daniel P.; Su, Yuanyuan; Suess, Katherine A.; Ueda, Yoshihiro; Umehata, Hideki; Vidal-Garcia, Alba; Wu, John F.
    We report the discovery of a triply imaged active galactic nucleus (AGN), lensed by the galaxy cluster MACS J0035.4-2015 (z(d) = 0.352). The object is detected in Hubble Space Telescope imaging taken for the RELICS program. It appears to have a quasi-stellar nucleus consistent with a point-source, with a de-magnified radius of r(e) less than or similar to 100 pc. The object is spectroscopically confirmed to be an AGN at z spec = 2.063 +/- 0.005 showing broad rest-frame UV emission lines, and detected in both X-ray observations with Chandra and in ALCS ALMA band 6 (1.2 mm) imaging. It has a relatively faint rest-frame UV luminosity for a quasar-like object, M (UV, 1450) = -19.7 +/- 0.2. The object adds to just a few quasars or other X-ray sources known to be multiply lensed by a galaxy cluster. Some diffuse emission from the host galaxy is faintly seen around the nucleus, and there is a faint object nearby sharing the same multiple-imaging symmetry and geometric redshift, possibly an interacting galaxy or a star-forming knot in the host. We present an accompanying lens model, calculate the magnifications and time delays, and infer the physical properties of the source. We find the rest-frame UV continuum and emission lines to be dominated by the AGN, and the optical emission to be dominated by the host galaxy of modest stellar mass M-* similar or equal to 10(9.2) M-circle dot. We also observe some variation in the AGN emission with time, which may suggest that the AGN used to be more active. This object adds a low-redshift counterpart to several relatively faint AGN recently uncovered at high redshifts with HST and JWST.
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    ALMA Lensing Cluster Survey: Bright [C ii] 158 μm Lines from a Multiply Imaged Sub-L* Galaxy at z=6.0719
    (2021) Fujimoto, Seiji; Oguri, Masamune; Brammer, Gabriel; Yoshimura, Yuki; Laporte, Nicolas; Gonzalez-Lopez, Jorge; Caminha, Gabriel B.; Kohno, Kotaro; Zitrin, Adi; Richard, Johan; Ouchi, Masami; Bauer, Franz E.; Smail, Ian; Hatsukade, Bunyo; Ono, Yoshiaki; Kokorev, Vasily; Umehata, Hideki; Schaerer, Daniel; Knudsen, Kirsten; Sun, Fengwu; Magdis, Georgios; Valentino, Francesco; Ao, Yiping; Toft, Sune; Dessauges-Zavadsky, Miroslava; Shimasaku, Kazuhiro; Caputi, Karina; Kusakabe, Haruka; Morokuma-Matsui, Kana; Shotaro, Kikuchihara; Egami, Eiichi; Lee, Minju M.; Rawle, Timothy; Espada, Daniel
    We present bright [C ii] 158 mu m line detections from a strongly magnified and multiply imaged (mu similar to 20-160) sub-L* (MUV=-19.75-0.44+0.55) Lyman-break galaxy (LBG) at z = 6.0719 +/- 0.0004, drawn from the ALMA Lensing Cluster Survey (ALCS). Emission lines are identified at 268.7 GHz at >= 8 sigma exactly at the positions of two multiple images of the LBG, behind the massive galaxy cluster RXCJ0600-2007. Our lens models, updated with the latest spectroscopy from VLT/MUSE, indicate that a sub region of the LBG crosses the caustic, and is lensed into a long (similar to 6 '') arc with a local magnification of mu similar to 160, for which the [C ii] line is also significantly detected. The source plane reconstruction resolves the interstellar medium (ISM) structure, showing that the [C ii] line is co-spatial with the rest-frame UV continuum at a scale of similar to 300 pc. The [C ii] line properties suggest that the LBG is a rotation-dominated system, whose velocity gradient explains a slight difference in redshifts between the whole LBG and its sub-region. The star formation rate (SFR)-L-[CII] relations, for whole and sub-regions of the LBG, are consistent with those of local galaxies. We evaluate the lower limit of the faint-end of the [C ii] luminosity function at z = 6, finding it to be consistent with predictions from semi-analytical models and from the local SFR-L-[CII] relation with a SFR function at z = 6. These results imply that the local SFR-L-[CII] relation is universal for a wide range of scales, including the spatially resolved ISM, the whole region of the galaxy, and the cosmic scale, even in the epoch of reionization.
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    ALMA Lensing Cluster Survey: Full Spectral Energy Distribution Analysis of z ∼ 0.5-6 Lensed Galaxies Detected with millimeter Observations
    (2024) Uematsu, Ryosuke; Ueda, Yoshihiro; Kohno, Kotaro; Toba, Yoshiki; Yamada, Satoshi; Smail, Ian; Umehata, Hideki; Fujimoto, Seiji; Hatsukade, Bunyo; Ao, Yiping; Bauer, Franz Erik; Brammer, Gabriel; Dessauges-Zavadsky, Miroslava; Espada, Daniel; Jolly, Jean-Baptiste; Koekemoer, Anton M.; Kokorev, Vasily; Magdis, Georgios E.; Oguri, Masamune; Sun, Fengwu
    Sub/millimeter galaxies are a key population for the study of galaxy evolution because the majority of star formation at high redshifts occurred in galaxies deeply embedded in dust. To search for this population, we have performed an extensive survey with Atacama Large Millimeter/submillimeter Array (ALMA), called the ALMA Lensing Cluster Survey (ALCS). This survey covers 133 arcmin(2) area and securely detects 180 sources at z similar to 0.5-6 with a flux limit of similar to 0.2 mJy at 1.2 mm. Here, we report the results of multiwavelength spectral energy distribution analysis of the whole ALCS sample, utilizing the observed-frame UV to millimeter photometry. We find that the majority of the ALCS sources lie on the star-forming main sequence, with a smaller fraction showing intense starburst activities. The ALCS sample contains high infrared-excess sources ( IRX = log ( L dust / L UV ) > 1 ), including two extremely dust-obscured galaxies (IRX > 5). We also confirm that the ALCS sample probes a broader range in lower dust mass than conventional submillimeter galaxy samples in the same redshift range. We identify six heavily obscured active galactic nucleus (AGN) candidates that are not detected in the archival Chandra data in addition to the three X-ray AGNs reported by Uematsu et al. (2023). The inferred AGN luminosity density shows a possible excess at z = 2-3 compared with that determined from X-ray surveys below 10 keV.
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    JWST and ALMA Multiple-line Study in and around a Galaxy at z=8.496: Optical to Far-Infrared Line Ratios and the Onset of an Outflow Promoting Ionizing Photon Escape
    (2024) Fujimoto, Seiji; Ouchi, Masami; Nakajima, Kimihiko; Harikane, Yuichi; Isobe, Yuki; Brammer, Gabriel; Oguri, Masamune; Gimenez-Arteaga, Clara; Heintz, Kasper E.; Kokorev, Vasily; Bauer, Franz E.; Ferrara, Andrea; Kojima, Takashi; Lagos, Claudia del P.; Laura, Sommovigo; Schaerer, Daniel; Shimasaku, Kazuhiro; Hatsukade, Bunyo; Kohno, Kotaro; Sun, Fengwu; Valentino, Francesco; Watson, Darach; Fudamoto, Yoshinobu; Inoue, Akio K.; Gonzalez-Lopez, Jorge; Koekemoer, Anton M.; Knudsen, Kirsten; Lee, Minju M.; Magdis, Georgios E.; Richard, Johan; Strait, Victoria B.; Sugahara, Yuma; Tamura, Yoichi; Toft, Sune; Umehata, Hideki; Walth, Gregory
    We present Atacama Large Millimeter/submillimeter Array (ALMA) deep spectroscopy for a lensed galaxy at z(spec) = 8.496 with log(M-star/M-circle dot) similar to 7.8 whose optical nebular lines and stellar continuum are detected by JWST/NIRSpec and NIRCam Early Release Observations in the field of SMACS J0723.3-7327. Our ALMA spectrum shows [O III] 88 mu m and [C II] 158 mu m line detections at 4.0 sigma and 4.5 sigma, respectively. The redshift and position of the [O III] line coincide with those of the JWST source, while the [C II] line is blueshifted by 90 km s(-1) with a spatial offset of 0.'' 5 (approximate to 0.5 kpc in the source plane) from the centroid of the JWST source. The NIRCam F444W image, including [O III] lambda 5007 and H beta line emission, spatially extends beyond the stellar components by a factor of >8. This indicates that the z = 8.5 galaxy has already experienced strong outflows as traced by extended [O III] lambda 5007 and offset [C II] emission, which would promote ionizing photon escape and facilitate reionization. With careful slit-loss corrections and the removal of emission spatially outside the galaxy, we evaluate the [O III] 88 mu m/lambda 5007 line ratio, and derive the electron density n (e) by photoionization modeling to be 220(-130)(+230) cm(-3), which is comparable with those of z similar to 2-3 galaxies. We estimate an [O III] 88 mu m/[C II] 158 mu m line ratio in the galaxy of >4, as high as those of known z similar to 6-9 galaxies. This high [O III] 88 mu m/[C II] 158 mu m line ratio is generally explained by the high n(e) as well as the low metallicity (Z(gas)/Z(circle dot)=0.04(-0.02)(+0.02)), high ionization parameter (log U > -2.27), and low carbon-to-oxygen abundance ratio (log(C/O) = [-0.52: -0.24]) obtained from the JWST/NIRSpec data; further [C II] follow-up observations will constrain the covering fraction of photodissociation regions.
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    SERENADE. II. An ALMA Multiband Dust Continuum Analysis of 28 Galaxies at 5<z<8 and the Physical Origin of the Dust Temperature Evolution
    (2024) Mitsuhashi, Ikki; Harikane, Yuichi; Bauer, Franz E.; Bakx, Tom J. L. C.; Ferrara, Andrea; Fujimoto, Seiji; Hashimoto, Takuya; Inoue, Akio K.; Iwasawa, Kazushi; Nishimura, Yuri; Imanishi, Masatoshi; Ono, Yoshiaki; Saito, Toshiki; Sugahara, Yuma; Umehata, Hideki; Vallini, Livia; Wang, Tao; Zavala, Jorge A.
    We present an analysis of the Atacama Large Millimeter-submillimeter Array (ALMA) multiband dust continuum observations for 28 spectroscopically confirmed bright Lyman break galaxies at 5 < z < 8. Our sample consists of 11 galaxies at z similar to 6 newly observed in our ALMA program, which substantially increases the number of 5 < z < 8 galaxies with both rest-frame 88 and 158 mu m continuum observations, allowing us to simultaneously measure the IR luminosity and dust temperature for a statistical sample of z greater than or similar to 5 galaxies for the first time. We derive the relationship between the ultraviolet (UV) slope (beta(UV)) and infrared excess (IRX) for the z similar to 6 galaxies, and find a shallower IRX-beta(UV) relation compared to the previous results at z similar to 2-4. Based on the IRX-beta(UV) relation consistent with our results and the beta(UV)-M-UV relation including fainter galaxies in the literature, we find a limited contribution of the dust-obscured star formation to the total star formation rate density, similar to 30% at z similar to 6. Our measurements of the dust temperature at z similar to 6-7, T-dust = 40.9(-9.1)(+10.0) K on average, support a gentle increase of T-dust from z = 0 to z similar to 6-7. Using an analytic model with parameters consistent with recent James Webb Space Telescope results, we discuss that the observed redshift evolution of the dust temperature can be reproduced by an similar to 0.6 dex decrease in the gas depletion timescale and similar to 0.4 dex decrease in the metallicity. The variety of T-dust observed at high redshifts can also be naturally explained by scatters around the star formation main sequence and average mass-metallicity relation including an extremely high dust temperature of T-dust > 80 K observed in a galaxy at z = 8.3.
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    The onset of star formation 250 million years after the Big Bang
    (2018) Hashimoto, Takuya; Laporte, Nicolás; Mawatari, Ken; Ellis, Richard S.; Inoue, Akio K.; Zackrisson, Erik; Roberts-Borsani, Guido; Zheng, Wei; Tamura, Yoichi; Bauer, Franz Erik; Fletcher, Thomas; Harikane, Yuichi; Hatsukade, Bunyo; Hayatsu, Natsuki H.; Matsuda, Yuichi; Matsuo, Hiroshi; Okamoto, Takashi; Ouchi, Masami; Pello, Roser; Rydberg, Claes-Erik; Shimizu, Ikkoh; Taniguchi, Yoshiaki; Umehata, Hideki; Yoshida, Naoki