Browsing by Author "Hashimoto, Takuya"

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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 Extended [C ii] under Construction? Observation of the Brightest High-z Lensed Star-forming Galaxy at z=6.2
    (2024) Fudamoto, Yoshinobu; Inoue, Akio K.; Coe, Dan; Welch, Brian; Acebron, Ana; Ricotti, Massimo; Mandelker, Nir; Windhorst, Rogier A.; Xu, Xinfeng; Sugahara, Yuma; Bauer, Franz E.; Bradac, Marusa; Bradley, Larry D.; Diego, Jose M.; Florian, Michael; Frye, Brenda; Fujimoto, Seiji; Hashimoto, Takuya; Henry, Alaina; Mahler, Guillaume; Oesch, Pascal A.; Ravindranath, Swara; Rigby, Jane; Sharon, Keren; Strait, Victoria; Tamura, Yoichi; Trenti, Michele; Vanzella, Eros; Zackrisson, Erik; Zitrin, Adi
    We present results of [C ii] 158 mu m emission line observations, and report the spectroscopic redshift confirmation of a strongly lensed (mu similar to 20) star-forming galaxy, MACS0308-zD1 at z = 6.2078 +/- 0.0002. The [C ii] emission line is detected with a signal-to-noise ratio >6 within the rest-frame UV-bright clump of the lensed galaxy (zD1.1) and exhibits multiple velocity components; the narrow [C ii] has a velocity full width half maximum (FWHM) of 110 +/- 20 km s(-1), while broader [C ii] is seen with an FWHM of 230 +/- 50 km s(-1). The broader [C ii] component is blueshifted (-80 +/- 20 km s(-1)) with respect to the narrow [C ii] component, and has a morphology that extends beyond the UV-bright clump. We find that, while the narrow [C ii] emission is most likely associated with zD1.1, the broader component is possibly associated with a physically distinct gas component from zD1.1 (e.g., outflowing or inflowing gas). Based on the nondetection of lambda(158 mu m) dust continuum, we find that MACS0308-zD1's star formation activity occurs in a dust-free environment indicated by a strong upper limit of infrared luminosity less than or similar to 9 x 10(8)L(circle dot). Targeting this strongly lensed faint galaxy for follow-up Atacama Large Millimeter/submillimeter Array and JWST observations will be crucial to characterize the details of typical galaxy growth in the early Universe.
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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