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Arrigoni Battaia, F.,Chen, Chian-Chou,Fumagalli, M.,Cai, Zheng,Calistro Rivera, G.,Xu, Jiachuan,Smail, I.,Prochaska, J. X.,Yang, Yujin,De Breuck, C. Springer-Verlag 2018 Astronomy and astrophysics Vol.620 No.-
<P>In the hierarchical model of structure formation, giant elliptical galaxies form through merging processes within the highest density peaks known as protoclusters. While high-redshift radio galaxies usually pinpoint the location of these environments, we have recently discovered at <I>z</I> ∼ 2−3 three enormous (> 200 kpc) Lyman-<I>α</I> nebulae (ELANe) that host multiple active galactic nuclei (AGN) and that are surrounded by overdensities of Lyman-<I>α</I> emitters (LAE). These regions are prime candidates for massive protoclusters in the early stages of assembly. To characterize the star-forming activity within these rare structures - both on ELAN and protocluster scales - we have initiated an observational campaign with the <I>James Clerk Maxwell</I> Telescope (JCMT) and the Atacama Pathfinder EXperiment (APEX) telescopes. In this paper we report on sensitive SCUBA-2/JCMT 850 and 450 <I>μ</I>m observations of a ∼128 arcmin<SUP>2</SUP> field comprising the ELAN MAMMOTH-1, together with the peak of the hosting BOSS1441 LAE overdensity at <I>z</I> = 2.32. These observations unveil 4.0 ± 1.3 times higher source counts at 850 <I>μ</I>m with respect to blank fields, likely confirming the presence of an overdensity also in obscured tracers. We find a strong detection at 850 <I>μ</I>m associated with the continuum source embedded within the ELAN MAMMOTH-1, which - together with the available data from the literature - allow us to constrain the spectral energy distribution of this source to be of an ultra-luminous infrared galaxy (ULIRG) with a far-infrared luminosity of LFIR<SUP>SF</SUP> = 2.4−2.1<SUP>+7.4</SUP>×10<SUP>12</SUP><I>L</I>⊙, and hosting an obscured AGN. Such a source is thus able to power a hard photoionization plus outflow scenario to explain the extended Lyman-<I>α</I>, He II<I>λ</I>1640, and C IV<I>λ</I>1549 emission, and their kinematics. In addition, the two brightest detections at 850 <I>μ</I>m (<I>f</I>850 > 18 mJy) sit at the density peak of the LAEs’ overdensity, likely pinpointing the core of the protocluster. Future multiwavelength and spectroscopic datasets targeting the full extent of the BOSS1441 overdensity have the potential to firmly characterize a cosmic nursery of giant elliptical galaxies, and ultimately of a massive cluster.</P>
Optical Properties of Two Different Metallic NaxCoO₂ : x = 0.35 and 0.75
J. Hwang,J. Yang,T. Timusk,F. C. Chou 한국자기학회 2005 Journal of Magnetics Vol.10 No.3
We report optical ab-plane properties of the layered sodium cobaltate, Na_xCoO₂ for x = 0.35 and 0.75. Two samples show metallic behaviors according to dc resistivity transport. Overall temperature dependent optical conductivities of both samples are very similar to those of the high temperature superconducting underdoped cuprates. We found that the optical scattering rate of x = 0.75 sample, which is in a Curie-Weiss metallic phase, varies linearly (non-Fermi liquid) with frequency and temperature while that of x = 0.35 sample, which is in a paramagnetic metallic phase, varies quadratically (Fermi liquid) with frequency and temperature. Both x = 0.35 and 0.75 samples have an onset of scattering around 600 ㎝-¹ which can be attributed to the interaction of charge carriers with a bosonic collective mode in a system.
C. S. Yang,K. F. Chien,J. Y. Lai,C. W. Luo,W. C. Chou,Y. T. Shih,J. S. Wang,S. R. Jian 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.5
Self-assembled CdTe/ZnSe Stranski-Krastanow quantum-dot (QD) structures, which have a CdSe-like precursor-layer (PCL) between CdTe quantum dots and ZnSe matrix, were grown by molecular beam epitaxy. The carrier dynamics of the structures was studied by photoluminescence (PL) and time-resolved photoluminescence (TRPL) measurements. The temperature-dependent PL spectra revealed that there is a carrier transformation from small dots to larger dots via the precursor layer. Temperature-dependent PL measurements verify the existence of the QD excited excitonic state in 5.0 mono-layer (ML) coverage. In 0.6 ML coverage, the TRPL spectra exhibited a double-exponential decay process, as the detection energy at PCL emission energy. The faster decay time is corresponded to the carrier lifetime in PCL, the slower decay time exhibits the carrier in small QD. However, in 5.0 ML coverage, a faster and slower decay time represents the carrier lifetime in QD excited state for larger QD and the carrier lifetime in QD ground state for smaller QD.