| 1. |
- Hashimoto, Takuya, et al.
(författare)
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Big Three Dragons: A z=7.15 Lyman-break galaxy detected in [Oiii] 88 mu m, [Cii] 158 mu m, and dust continuum with ALMA
- 2019
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Ingår i: Publication of the Astronomical Society of Japan. - : Oxford University Press (OUP). - 2053-051X .- 0004-6264. ; 71:4
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Tidskriftsartikel (refereegranskat)abstract
- We present new ALMA observations and physical properties of a Lyman break galaxy at z = 7.15. Our target, B14-65666, has a bright ultra-violet (UV) absolute magnitude, M-UV approximate to -22.4, and has been spectroscopically identified in Ly alpha with a small rest-frame equivalent width of approximate to 4 angstrom. A previous Hubble Space TElescope (HST) image has shown that the target is composed of two spatially separated clumps in the rest-frame UV. With ALMA, we have newly detected spatially resolved [Oiii] 88 mu m, [Cii] 158 mu m, and their underlying dust continuum emission. In the whole system of B14-65666, the [Oiii] and [Cii] lines have consistent redshifts of 7.1520 +/- 0.0003, and the [Oiii] luminosity, (34.4 +/- 4.1)x 10(8)L(circle dot), is about three times higher than the [Cii] luminosity, (11.0 +/- 1.4) x 10(8)L(circle dot). With our two continuum flux densities, the dust temperature is constrained to be T-d approximate to 50-60K under the assumption of a dust emissivity index of beta(d) = 2.0-1.5, leading to a large total infrared luminosity of L-TIR approximate to 1 x 10(12)L(circle dot). Owing to our high spatial resolution data, we show that the [Oiii] and [Cii] emission can be spatially decomposed into two clumps associated with the two rest-frame UV clumps whose spectra are kinematically separated by approximate to 200kms(-1). We also find these two clumps have comparable UV, infrared, [Oiii], and [Cii] luminosities. Based on these results, we argue that B14-65666 is a starburst galaxy induced by a major merger. The merger interpretation is also supported by the large specific star formation rate (defined as the star formation rate per unit stellar mass), sSFR Gyr(-1), inferred from our SED fitting. Probably, a strong UV radiation field caused by intense star formation contributes to its high dust temperature and the [Oiii]-to-[Cii] luminosity ratio.
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| 2. |
- Steiner, Oskar, et al.
(författare)
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Properties of small-scale magnetism of stellar atmospheres
- 2014
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Ingår i: Nippon Tenmon Gakkai obun kenkyu hokoku. - : Oxford University Press (OUP). - 0004-6264. ; 66:SI1, s. S5-
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Tidskriftsartikel (refereegranskat)abstract
- The magnetic field outside of sunspots is concentrated in the intergranular space, where it forms a delicate filigree of bright ribbons and dots as seen on broad band images of the Sun. We expect this small-scale magnetic field to exhibit a similar behavior in stellar atmospheres. In order to find out more about it, we perform numerical simulations of the surface layers of stellar atmospheres. Here, we report on preliminary results from simulations in the range between 4000 K and 6500 K effective temperature with an initial vertical, homogeneous magnetic field of 50 G strength. We find that the field strength of the strongest magnetic flux concentrations increases with decreasing effective temperature at the height level where the average Rosseland optical depth is one. On the other hand, at the same level, the field is less strong than the thermal equipartition value in the coolest model but assumes superequipartition in the models hotter than 5000 K. While the Wilson depression of the strongest field concentrations is about one pressure scale height in the coolest model, it is more than four times the pressure scale height in the hottest one. We also find that the relative contribution of the bright filigree to the bolometric, vertically directed radiative intensity is most significant for the T-eff = 5000 K model (0.6%-0.79%) and least significant for the hottest and coolest models (0.1%-0.46% and 0.14%-0.32%, respectively). This behavior suggests that the effect of the small-scale magnetic field on the photometric variability is more significant for K dwarf stars than for F-type and also M-type stars.
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