Browsing by Author "Uematsu, Ryosuke"

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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: 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.