• Title/Summary/Keyword: Black Holes

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Weighing the most massive black holes in the Universe

  • Jun, Hyun-Sung;Im, Myung-Shin
    • The Bulletin of The Korean Astronomical Society
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    • v.37 no.1
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    • pp.35.2-35.2
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    • 2012
  • According to the correlations between galaxy and black hole mass, the most massive galaxies harbor the most massive black holes, with a current mass limit of.

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Observational Evidence for the Coevolution between Supermassive Black Holes and Host Galaxies

  • Kim, Minjin
    • The Bulletin of The Korean Astronomical Society
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    • v.41 no.2
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    • pp.29.5-30
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    • 2016
  • (1) The correlation between the mass of supermassive black holes (SMBHs) and the properties of their host galaxies suggests that SMBHs and host galaxies are closely linked in their formation and evolution. While the exact origin of their relationship is still under debate, theoretical models often invoke feedback from active galactic nuclei as a crucial mechanism for establishing the BH-host correlation. In the first part of my talk, I will present our efforts to find observational sign of the AGN feedback in young luminous AGNs. (2) While intermediate-mass black hole (IMBH) is thought be cosmologically important class to understand the link between stellar mass black holes and SMBHs, it is extremely rare in the present-day Universe. In the second part of this talk, I will report a Gemini/GMOS-N IFU study of an ultraluminous X-ray source in NGC 5252, which is a possible candidate of an off-nuclear non-stellar black hole.

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bservational Evidence for the Coevolution between Supermassive Black Holes and Host Galaxies

  • Kim, Minjin
    • The Bulletin of The Korean Astronomical Society
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    • v.42 no.1
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    • pp.27.4-27.4
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    • 2017
  • (1) The correlation between the mass of supermassive black holes (SMBHs) and the properties of their host galaxies suggests that SMBHs and host galaxies are closely linked in their formation and evolution. While the exact origin of their relationship is still under debate, theoretical models often invoke feedback from active galactic nuclei as a crucial mechanism for establishing the BH-host correlation. In the first part of my talk, I will present possible observational biases in the BH-host relation, and methods to overcome these biases. I will also report our efforts to find observational sign of the AGN feedback in high-z young luminous AGNs. (2) While intermediate-mass black hole (IMBH) is thought be cosmologically important class to understand the link between stellar mass black holes and SMBHs, it is extremely rare in the present-day Universe. In the second part of this talk, I will report a Gemini/GMOS-N IFU study of an ultraluminous X-ray source in NGC 5252, which is a possible candidate of an off-nuclear non-stellar black hole.

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THE GALAXY-BLACK HOLE CONNECTION IN THE LOCAL UNIVERSE

  • Schawinski, Kevin;Fellow, Einstein
    • Publications of The Korean Astronomical Society
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    • v.25 no.3
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    • pp.77-82
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    • 2010
  • Recent results from large surveys of the local universe show that the galaxy-black hole connection is linked to host morphology at a fundamental level and that there are two fundamentally different modes of black hole growth. The fraction of early-type galaxies with actively growing black holes, and therefore the AGN duty cycle, declines significantly with increasing black hole mass. Late-type galaxies exhibit the opposite trend: the fraction of actively growing black holes increases with black hole mass. Issues of AGN selection bias and prospects for near-future efforts with high redshift data are discussed.

Tracing the growth of the supermassive black holes with halo mergers

  • Byeon, Woowon;Kim, Juhan;Park, Myeong-Gu
    • The Bulletin of The Korean Astronomical Society
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    • v.40 no.2
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    • pp.47.1-47.1
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    • 2015
  • The formation mechanism of supermassive black holes (SMBHs) at the center of galaxies remains an open fundamental question. Black holes (BHs) are believed to grow by accretion of gas or by merging with other BHs. Motivated by the observation of luminous quasar around redshift z ~ 7 with SMBH mass up to 109 solar mass, we follow the growth of the early assembly of SMBHs that trace the hierarchical evolution of dark matter halos derived from large cosmological simulations. The initial masses of BH seeds in the first halos were set up according to the BH mass - halo mass relation. We assume that mergers of host galaxies cause loss of angular momentum of gas and trigger episodes of gas accretion onto BHs for available durations and at the end of each episode of accretion, BHs merge immediately. We trace the evolution of BH masses for various scenarios for central gas properties in halos. We estimate the BH to halo mass ratio and BH mass function at each redshift.

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The Environments of the Most Massive Galaxies and Black Holes

  • Yoon, Yongmin;Im, Myungshin
    • The Bulletin of The Korean Astronomical Society
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    • v.39 no.2
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    • pp.66.1-66.1
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    • 2014
  • We study the environment of the most massive galaxies and the most massive black holes. We use SDSS DR7 data, the catalog from Simard et al. (2011), Mendel et al. (2014), and KIAS value-added galaxy catalog (Choi et al. 2011). Currently, we investigate the number density as an environment around each galaxy. Number densities are measured by $5^{th}$ and $10^{th}$ nearest photometric galaxies within 7000km/s from the spectroscopic galaxies. The most massive galaxies (M > $10^{12}M_{\odot}$) or black holes ($M{\sim}10^{10}M_{\odot}$) tend to reside in very dense regions in comparison with less massive ones. We also present the research plan and future work.

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Progress Report on Optical Spectroscopy of X-ray selected Intermediate-mass Black Holes

  • Kim, Minjin;Ho, Luis C.
    • The Bulletin of The Korean Astronomical Society
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    • v.39 no.1
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    • pp.42.2-42.2
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    • 2014
  • We present high-resolution optical spectra of newly selected candidates of intermediate-mass black holes. The sample was selected based on the variability and spectral shape in X-ray. The spectra was taken with Magellan 6.5 m Clay Telescope and cover the rest-frame region 3500-10000A. The high spectral resolution (R~4000) of the spectrum allows us to estimate BH masses of the sources. Interestingly, the majority of the sample appears to have broad emission lines. Using this dataset, we will estimate the BH masses and Eddington ratio in order to understand their physical properties.

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Towards the Understanding of the Growth and Evolution of Supermassive Black Holes at Galaxy Centers

  • Kim, Ji-hoon
    • The Bulletin of The Korean Astronomical Society
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    • v.43 no.2
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    • pp.32.2-32.2
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    • 2018
  • As computational resolution of modern cosmological simulations reach ever so close to resolve individual star-forming clumps in a galaxy, a need for "resolution-appropriate" physics for a galaxy-scale simulation has never been greater. To this end, we introduce a self-consistent numerical framework that includes explicit treatments of feedback from star-forming molecular clouds and massive black holes. We perform a state-of-the-art cosmological simulation of a quasar-host galaxy at z~7.5, and demonstrate that previously undiscussed types of interplay between galactic components may hold important clues about the growth and impact of quasar-host galaxies.

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