| 1. |
- Bakx, Tom J. L. C., et al.
(författare)
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ALMA uncovers the [C II] emission and warm dust continuum in a z=8.31 Lyman break galaxy
- 2020
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 493:3, s. 4294-4307
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Tidskriftsartikel (refereegranskat)abstract
- We report on the detection of the [C II] 157.7 mu m emission from the Lyman break galaxy (LBG) MACS0416_Y1 at z = 8.3113, by using the Atacama Large Millimeter/submillimeter Array (ALMA). The luminosity ratio of [O III] 88 mu m (from previous campaigns) to [CII] is 9.3 +/- 2.6, indicative of hard interstellar radiation fields and/or a low covering fraction of photodissociation regions. The emission of [C II] is cospatial to the 850 mu m dust emission (90 mu m rest frame, from previous campaigns), however the peak [C II] emission does not agree with the peak [O III] emission, suggesting that the lines originate from different conditions in the interstellar medium. We fail to detect continuum emission at 1.5 mm (160 mu m rest frame) down to 18 mu Jy (3 sigma). This non-detection places a strong limits on the dust spectrum, considering the 137 +/- 26 mu Jy continuum emission at 850 mu m. This suggests an unusually warm dust component (T > 80 K, 90 per cent confidence limit), and/or a steep dust-emissivity index (beta(dust) > 2), compared to galaxy-wide dust emission found at lower redshifts (typically T similar to 30-50 K, beta(dust) similar to 1-2). If such temperatures are common, thiswould reduce the required dust mass and relax the dust production problem at the highest redshifts. We therefore warn against the use of only single-wavelength information to derive physical properties, recommend a more thorough examination of dust temperatures in the early Universe, and stress the need for instrumentation that probes the peak of warm dust in the Epoch of Reionization.
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| 2. |
- Hashimoto, Takuya, et al.
(författare)
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The onset of star formation 250 million years after the Big Bang
- 2018
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Ingår i: Nature. - : NATURE PUBLISHING GROUP. - 0028-0836 .- 1476-4687. ; 557:7705, s. 392-395
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Tidskriftsartikel (refereegranskat)abstract
- A fundamental quest of modern astronomy is to locate the earliest galaxies and study how they influenced the intergalactic medium a few hundred million years after the Big Bang(1-3). The abundance of star-forming galaxies is known to decline(4,5) from redshifts of about 6 to 10, but a key question is the extent of star formation at even earlier times, corresponding to the period when the first galaxies might have emerged. Here we report spectroscopic observations of MACS1149-JD1(6), a gravitationally lensed galaxy observed when the Universe was less than four per cent of its present age. We detect an emission line of doubly ionized oxygen at a redshift of 9.1096 +/- 0.0006, with an uncertainty of one standard deviation. This precisely determined redshift indicates that the red rest-frame optical colour arises from a dominant stellar component that formed about 250 million years after the Big Bang, corresponding to a redshift of about 15. Our results indicate that it may be possible to detect such early episodes of star formation in similar galaxies with future telescopes.
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| 3. |
- Tamura, Yoichi, et al.
(författare)
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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
- 2019
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Ingår i: Astrophysical Journal. - : IOP PUBLISHING LTD. - 0004-637X .- 1538-4357. ; 874:1
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Tidskriftsartikel (refereegranskat)abstract
- We present the Atacama Large Millimeter/submillimeter Array 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 +/- 0.0003, making this object one of the farthest galaxies ever identified spectroscopically. The observed 850 mu m flux density of 137 +/- 26 mu Jy corresponds to a de-lensed total infrared (IR) luminosity of L-IR = (1.7 +/- 0.3) x 10(11) L-circle dot if assuming a dust temperature of T-dust = 50 K and an emissivity index of beta = 1.5, yielding a large dust mass of 4 x 10(6) M-circle dot. The ultraviolet-to-far-IR spectral energy distribution modeling where the [O III] emissivity model is incorporated suggests the presence of a young (tau(age) approximate to 4 Myr), star-forming (SFR approximate to 60 M-circle dot yr(-1)), moderately metal-polluted (Z approximate to 0.2 Z(circle dot)) stellar component with a mass of M-star = 3 x 10(8) M-circle dot. An analytic dust mass evolution model with a single episode of star formation does not reproduce the metallicity and dust mass in tau(age) approximate to 4 Myr, suggesting a pre-existing evolved stellar component with M-star similar to 3 x 10(9) M-circle dot and tau(age) similar to 0.3 Gyr as the origin of the dust mass.
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| 4. |
- Tamura, Yoichi, et al.
(författare)
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The 300 pc Resolution Imaging of a z=8.31 Galaxy : Turbulent Ionized Gas and Potential Stellar Feedback 600 Million Years after the Big Bang
- 2023
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Ingår i: Astrophysical Journal. - : Institute of Physics (IOP). - 0004-637X .- 1538-4357. ; 952:1
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Tidskriftsartikel (refereegranskat)abstract
- We present the results of 300 pc resolution Atacama Large Millimeter/submillimeter Array imaging of the [O iii] 88 & mu;m line and dust continuum emission from a z = 8.312 Lyman-break galaxy MACS0416_Y1. The velocity-integrated [O iii] emission has three peaks that are likely associated with three young stellar clumps of MACS0416_Y1, while the channel map shows a complicated velocity structure with little indication of a global velocity gradient unlike what was found in [C ii] 158 & mu;m at a larger scale, suggesting random bulk motion of ionized gas clouds inside the galaxy. In contrast, dust emission appears as two individual clumps apparently separating or bridging the [O iii]/stellar clumps. The cross-correlation coefficient between dust and ultraviolet-related emission (i.e., [O iii] and ultraviolet continuum) is unity on a galactic scale, while it drops at <1 kpc, suggesting well-mixed geometry of multiphase interstellar media on subkiloparsec scales. If the cutoff scale characterizes different stages of star formation, the cutoff scale can be explained by gravitational instability of turbulent gas. We also report on a kiloparsec-scale off-center cavity embedded in the dust continuum image. This could be a superbubble producing galactic-scale outflows, since the energy injection from the 4 Myr starburst suggested by a spectral energy distribution analysis is large enough to push the surrounding media creating a kiloparsec-scale cavity.
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