62,853 research outputs found

    The ALPINE-ALMA [C II] survey: Star-formation-driven outflows and circumgalactic enrichment in the early Universe

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    We study the efficiency of galactic feedback in the early Universe by stacking the [C II] 158 ÎŒm emission in a large sample of normal star-forming galaxies at 4   4. From the stacking analysis of the datacubes, we find that the combined [C II] core emission (|v|< 200 km s⁻Âč) of the higher-SFR galaxies is extended on physical sizes of ∌30 kpc (diameter scale), well beyond the analogous [C II] core emission of lower-SFR galaxies and the stacked far-infrared continuum. The detection of such extended metal-enriched gas, likely tracing circumgalactic gas enriched by past outflows, corroborates previous similar studies, confirming that baryon cycle and gas exchanges with the circumgalactic medium are at work in normal star-forming galaxies already at early epochs

    A More Precise Extraction of |V_{cb}| in HQEFT of QCD

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    The more precise extraction for the CKM matrix element |V_{cb}| in the heavy quark effective field theory (HQEFT) of QCD is studied from both exclusive and inclusive semileptonic B decays. The values of relevant nonperturbative parameters up to order 1/m^2_Q are estimated consistently in HQEFT of QCD. Using the most recent experimental data for B decay rates, |V_{cb}| is updated to be |V_{cb}| = 0.0395 \pm 0.0011_{exp} \pm 0.0019_{th} from B\to D^{\ast} l \nu decay and |V_{cb}| = 0.0434 \pm 0.0041_{exp} \pm 0.0020_{th} from B\to D l \nu decay as well as |V_{cb}| = 0.0394 \pm 0.0010_{exp} \pm 0.0014_{th} from inclusive B\to X_c l \nu decay.Comment: 7 pages, revtex, 4 figure

    Evidence for a Functional Interaction between Integrins and G Protein-activated Inward Rectifier K+ Channels

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    Heteromultimeric G protein-activated inward rectifier K+ (GIRK) channels, abundant in heart and brain, help to determine the cellular membrane potential as well as the frequency and duration of electrical impulses. The sequence arginine-glycine-aspartate (RGD), located extracellularly between the first membrane-spanning region and the pore, is conserved among all identified GIRK subunits but is not found in the extracellular domain of any other cloned K+ channels. Many integrins, which, like channels, are integral membrane proteins, recognize this RGD sequence on other proteins, usually in the extracellular matrix. We therefore asked whether GIRK activity might be regulated by direct interaction with integrin. Here, we present evidence that mutation of the RGD site to RGE, particularly on the GIRK4 subunit, decreases or abolishes GIRK current. Furthermore, wild-type channels can be co-immunoprecipitated with integrin. The total cellular amount of expressed mutant GIRK channel protein is the same as the wild-type protein; however, the amount of mutant channel protein that localizes to the plasma membrane is decreased relative to wild-type, most likely accounting for the diminished GIRK current detected. GIRK channels appear to bind directly to integrin and to require this interaction for proper GIRK channel membrane localization and function

    Lifetime Difference and Endpoint effect in the Inclusive Bottom Hadron Decays

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    The lifetime differences of bottom hadrons are known to be properly explained within the framework of heavy quark effective field theory(HQEFT) of QCD via the inverse expansion of the dressed heavy quark mass. In general, the spectrum around the endpoint region is not well behaved due to the invalidity of 1/mQ1/m_Q expansion near the endpoint. The curve fitting method is adopted to treat the endpoint behavior. It turns out that the endpoint effects are truly small and the explanation on the lifetime differences in the HQEFT of QCD is then well justified. The inclusion of the endpoint effects makes the prediction on the lifetime differences and the extraction on the CKM matrix element ∣Vcb∣|V_{cb}| more reliable.Comment: 11 pages, Revtex, 10 figures, 6 tables, published versio

    On measuring the Tully-Fisher relation at z>1z > 1

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    The evolution of the line width - luminosity relation for spiral galaxies, the Tully-Fisher relation, strongly constrains galaxy formation and evolution models. At this moment, the kinematics of z>1 spiral galaxies can only be measured using rest frame optical emission lines associated with star formation, such as Halpha and [OIII]5007/4959 and [OII]3727. This method has intrinsic difficulties and uncertainties. Moreover, observations of these lines are challenging for present day telescopes and techniques. Here, we present an overview of the intrinsic and observational challenges and some ways way to circumvent them. We illustrate our results with the HST/NICMOS grism sample data of z ~ 1.5 starburst galaxies. The number of galaxies we can use in the final Tully-Fisher analysis is only three. We find a ~2 mag offset from the local rest frame B and R band Tully-Fisher relation for this sample. This offset is partially explained by sample selection effects and sample specifics. Uncertainties in inclination and extinction and the effects of star formation on the luminosity can be accounted for. The largest remaining uncertainty is the line width / rotation curve velocity measurement. We show that high resolution, excellent seeing integral field spectroscopy will improve the situation. However, we note that no flat rotation curves have been observed for galaxies with z>1. This could be due to the described instrumental and observational limitations, but it might also mean that galaxies at z>1 have not reached the organised motions of the present day.Comment: 13 pages, 7 figures, A&A accepte

    Approximation for discrete Fourier transform and application in study of three-dimensional interacting electron gas

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    The discrete Fourier transform is approximated by summing over part of the terms with corresponding weights. The approximation reduces significantly the requirement for computer memory storage and enhances the numerical computation efficiency with several orders without loosing accuracy. As an example, we apply the algorithm to study the three-dimensional interacting electron gas under the renormalized-ring-diagram approximation where the Green's function needs to be self-consistently solved. We present the results for the chemical potential, compressibility, free energy, entropy, and specific heat of the system. The ground-state energy obtained by the present calculation is compared with the existing results of Monte Carlo simulation and random-phase approximation.Comment: 11 pages, 13 figure
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