• Title/Summary/Keyword: redshift

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On the Global and Local Environmental Dependence of Type Ia Supernova Luminosity from the Analysis of SALT2 and MLCS2k2 Light-Curve Fitters

  • Kim, Young-Lo;Lee, Young-Wook
    • The Bulletin of The Korean Astronomical Society
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    • v.44 no.1
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    • pp.40.3-40.3
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    • 2019

  • There is growing evidence for the dependence of Type Ia supernova (SN Ia) luminosities on the environments. The origin of this correlation, however, is under debate. In order to explore the physical origin of the trend in detail, we analyze SN Ia light-curves by combining a sample of 1231 SNe Ia over a wide redshift range (0.01 < z < 1.37) in various SN surveys and employing two independent light-curve fitters of SALT2 and MLCS2k2. Although SALT2 is the most widely used fitter in the SN community, MLCS2k2 has a novelty in the context of an investigation of the luminosity evolution of SNe Ia. For this reason we use both fitters and analyze them separately. We also determine a stellar mass and a star formation rate (SFR) for a sample of ~600 host galaxies. In addition, because recent low-redshift studies suggest that this dependence manifests itself most strongly when using the local SFR at the SN location, we introduce a new method to infer the local environments by restricting the SN Ia sample in globally star-forming host galaxies to a low-mass host galaxy subset (${\leq}10^{10}M_{\odot}$). We find that SNe Ia in low-mass and star-forming host galaxies are fainter than those in high-mass and passive hosts, after light-curve corrections. Especially, for the first time in host studies, we show that SNe Ia in locally star-forming environments are $0.081{\pm}0.018$ mag fainter ($4.5{\sigma}$) than those in locally passive environments from the sample including SNe at the high-redshift range. Considering the significant difference in the mean stellar population age between these environments, the result would suggest that the origin of the environmental dependence is the luminosity evolution of SNe Ia.

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Lightwave ordering and applications of photonic quantum ring lasers (광양자테 레이저의 광파 질서와 응용)

  • 권오대;안정착;곽규섭;박병훈;박동훈;김준연
    • Proceedings of the IEEK Conference
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    • 1999.06a
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    • pp.309-314
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    • 1999

  • We report dimension-reduced and photon-induced quantum rings naturally formed in a vertical-cavity-like active microdisk plane due to Rayleigh＇s band of whispering gallery modes. The √T- dependent redshift, microampere-range threshold currents, λ/2 lightwave ordering, and chaotic properties are also discussed.

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Model-independent test of gravity

  • L'Huillier, Benjamin
    • The Bulletin of The Korean Astronomical Society
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    • v.45 no.1
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    • pp.48.3-48.3
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    • 2020

  • Using redshift-space distortion, I reconstruct the growth history as a smooth function using model independent methods. Assuming general relativity, I obtain the expansion history independently of the dark energy model, and test it to the supernovae data. The results are consistent with general relativity as gravity and the cosmological constant as dark energy, although interestingly negative dark energy densities are not ruled out by the data at z~0.7 to 1.

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Distant Quasars: Black hole mass growth and dust emission

  • Jun, Hyunsung D.
    • The Bulletin of The Korean Astronomical Society
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    • v.40 no.1
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    • pp.43.2-43.2
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    • 2015

  • The massive limit of black holes (BHs) is observed as present day ten billion solar masses. We search for observational signatures of BHs that become extremely massive (EMBHs, 1-10 billion solar masses). I will report on the evolution of active galactic nuclei (AGNs) through the growth of BH mass and their dust emission strength. First, we measured 26 EMBH masses of quasars at 1

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