Browsing by Author "Tamura, Yoichi"

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    ANIR: Atacama near-infrared camera for the 1.0 m miniTAO telescope
    (2015) Konishi, Masahiro; Motohara, Kentaro; Tateuchi, Ken; Takahashi, Hidenori; Kitagawa, Yutaro; Kato, Natsuko; Sako, Shigeyuki; Uchimoto, Yuka K.; Toshikawa, Koji; Ohsawa, Ryou; Yamamuro, Tomoyasu; Asano, Kentaro; Ita, Yoshifusa; Kamizuka, Takafumi; Komugi, Shinya; Koshida, Shintaro; Manabe, Sho; Matsunaga, Noriyuki; Minezaki, Takeo; Morokuma, Tomoki; Nakashima, Asami; Takagi, Toshinobu; Tanabe, Toshihiko; Uchiyama, Mizuho; Aoki, Tsutomu; Doi, Mamoru; Handa, Toshihiro; Kato, Daisuke; Kawara, Kimiaki; Kohno, Kotaro; Miyata, Takashi; Nakamura, Tomohiko; Okada, Kazushi; Soyano, Takao; Tamura, Yoichi; Tanaka, Masuo; Tarusawa, Ken'ichi; Yoshii, Yuzuru
    We have developed a near-infrared camera called ANIR (Atacama Near-InfraRed camera) for the University of Tokyo Atacama Observatory 1.0 m telescope (miniTAO) installed at the summit of Cerro Chajnantor (5640 m above sea level) in the north of Chile. The camera provides a field of view of 5'.1 x 5'.1 with a spatial resolution of 0 ''.298 pixel(-1) in the wavelength range of 0.95 to 2.4 mu m, using Offner relay optics and a PACE HAWAII-2 focal plane array. Taking advantage of the dry site, the camera is capable of narrow-band imaging observations at the hydrogen Paschen-alpha (Pa alpha, lambda = 1.8751 mu m in air) wavelength ground-based observations of which have been quite difficult due to deep atmospheric absorption, mainly from water vapor. We have been successfully obtaining Pa alpha images of Galactic objects and nearby galaxies since the first-light observation in 2009 with ANIR. The throughputs at the narrow-band filters (N1875, N191) including the atmospheric absorption show larger dispersion (similar to 10%) than those at broad-band filters (a few percent), indicating that they are affected by temporal fluctuations in precipitable water vapor (PWV) above the site. We evaluate the PWV content via the atmospheric transmittance at the narrow-band filters, and deduce that the median and the dispersion of the distribution of the PWV are 0.40 +/- 0.30 and 0.37 +/- 0.21mm, for the N1875 and N191 data respectively, which are remarkably smaller (49% +/- 38% for N1875 and 59% +/- 26% for N191) than radiometry measurements at the base of Cerro Chajnantor (an altitude of 5100 m). The decrease in PWV can be explained by the altitude of the site when we assume that the vertical distribution of the water vapor is approximated at an exponential profile with scale heights within 0.3-1.9 km (previously observed values at night). We thus conclude that miniTAO/ANIR at the summit of Cerro Chajnantor indeed provides us an excellent capability for a ground-based Paa observation.
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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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    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