• Title/Summary/Keyword: galaxies: jets

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"Maintenance"-mode feedback and the host galaxies of radio-AGN

  • Karouzos, Marios;Im, Myungshin;Trichas, Markos
    • The Bulletin of The Korean Astronomical Society
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    • v.39 no.1
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    • pp.37.1-37.1
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    • 2014
  • There exists strong evidence supporting the co-evolution of central supermassive black holes and their host galaxies; however it is still under debate how such a relation comes about and whether it is relevant for all or only a subset of galaxies. An important mechanism connecting AGN to their host galaxies is AGN feedback, potentially heating up or even expelling gas from galaxies. AGN feedback may hence be responsible for the eventual quenching of star formation and halting of galaxy growth. A rich multi-wavelength dataset ranging from the X-ray regime (Chandra), to far-IR (Herschel), and radio (WSRT) is available for the North Ecliptic Pole field, most notably surveyed by the AKARI infrared space telescope, covering a total area on the sky of 5.4 sq. degrees. We investigate the star-formation properties and possible signatures of radio feedback mechanisms in the host galaxies of 237 radio-AGN below redshift z=2 and at a radio 1.4 GHz flux density limit of 0.1 mJy. Using broadband SED modeling, the nuclear and host galaxy components of these sources are studied simultaneously as a function of their radio luminosity. Here we present results concerning the AGN content of the radio sources in this field, while offering evidence supporting a "maintenance" type of feedback from powerful radio-jets.

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SEDs and Beaming Effect for Fermi Blazars

  • Fan, Jun-Hui;Yang, Jiang-He;Liu, Yi;Yuan, Yu-Hai;Lin, Cao;Xiao, Hu-Bing
    • Journal of Astronomy and Space Sciences
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    • v.33 no.2
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    • pp.105-108
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    • 2016
  • In this work, based on our previous calculations of spectral energy distributions for a sample of Fermi blazars (Fan et al. 2015a), we calculated the radio loudness and performed correlation analyses. Our analysis results show that radio loudness is closely anti-correlated with synchrotron peak frequency and positively correlated with gamma-ray luminosity, suggesting that the gamma-ray emissions are strongly beamed.

APPARENT INWARD MOTION OF THE PARSEC-SCALE JET IN THE BL LAC OBJECT OJ287 DURING THE 2011-2012 γ-ray FLARES

  • SAWADA-SATOH, S.;AKIYAMA, K.;NIINUMA, K.;NAGAI, H.;KINO, M.;D'AMMANDO, F.;KOYAMA, S.;HADA, K.;ORIENTI, M.;HONMA, M.;SHIBATA, K.M.
    • Publications of The Korean Astronomical Society
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    • v.30 no.2
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    • pp.429-432
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    • 2015
  • We present a kinematic study of the parsec-scale radio jet in OJ 287, one of the most studied BL Lac objects, during ${\gamma}$-ray flares, to explore the relation between parsec-scale radio jet activity and ${\gamma}$-ray emission. The 22-GHz light curve of OJ 287 show three obvious flare events around 2011 May, 2011 October, and 2012 March. The second radio flare occurred during the ${\gamma}$-ray flaring period, and the third radio flare seemed to precede the ${\gamma}$-ray flare by one month. One jet component moved outward with respect to the core component with an apparent superluminal speed (~ 11c) from 2010 November to 2011 November. Then it changed direction, moving apparently inward in 2011 November, when the ${\gamma}$-ray flare occurred. The observed apparent inward motion of the jet at 22 GHz could be caused by a new jet component, unresolved at 22 GHz, in the innermost region.

VIMAP: AN INTERACTIVE PROGRAM PROVIDING RADIO SPECTRAL INDEX MAPS OF ACTIVE GALACTIC NUCLEI

  • Kim, Jae-Young;Trippe, Sascha
    • Journal of The Korean Astronomical Society
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    • v.47 no.5
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    • pp.195-199
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    • 2014
  • We present a GUI-based interactive Python program, VIMAP, which generates radio spectral index maps of active galactic nuclei (AGN) from Very Long Baseline Interferometry (VLBI) maps obtained at different frequencies. VIMAP is a handy tool for the spectral analysis of synchrotron emission from AGN jets, specifically of spectral index distributions, turn-over frequencies, and core-shifts. In general, the required accurate image alignment is difficult to achieve because of a loss of absolute spatial coordinate information during VLBI data reduction (self-calibration) and/or intrinsic variations of source structure as function of frequency. These issues are overcome by VIMAP which in turn is based on the two-dimensional cross-correlation algorithm of Croke & Gabuzda (2008). In this paper, we briefly review the problem of aligning VLBI AGN maps, describe the workflow of VIMAP, and present an analysis of archival VLBI maps of the active nucleus 3C 120.

The Development of the Black Hole Magnetosphere Model in the Last Thirty Years (블랙홀 자기권 모델 30년)

  • PARK SEOK JAE
    • Publications of The Korean Astronomical Society
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    • v.15 no.1
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    • pp.1-13
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    • 2000
  • Since Goldreich and Julian's pioneering work in 1969, the pulsar magnetosphere theory has been dramatically developed for theorists to possess an elegant axisymmetric, stationary model. Based on this development the black hole magnetosphere theory has also been established in the last 30 years. Such theoretical developments will be reviewd equation by equation in this paper.

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STATIONARY, AXISYMMETRIC BLACK HOLE MAGNETO SPHERES IN OBLATE SPHEROIDAL COORDINATES (축대칭을 만족하고 시간에 따라 변하지 않는 블랙홀 자기권의 편원 좌표계적 기술)

  • PARK SEOK JAE;FLETCHER ANDRE B.
    • Publications of The Korean Astronomical Society
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    • v.16 no.1
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    • pp.11-14
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    • 2001
  • In this paper, we simplify the equations of the Macdonald-Thome black hole magnetosphere. Our major assumption is that the 3-D electric and magnetic flux isosurfaces respectively form families of confocal oblate spheroids and hyperboloids. As a result, the magnetospheric equations are greatly simplified, and may provide a useful framework for instances when rigorous, theoretical approaches are not necessary.

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NEW EQUATIONS FOR THE ENTROPY INCREASE AND THE ANGULAR MOMENTUM-ENERGY EQUATION OF A BLACK HOLE (새로운 블랙흘 엔트로피 증가, 각운동량-에너지 추출 방정식)

  • Park, Seok-Jae
    • Publications of The Korean Astronomical Society
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    • v.18 no.1
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    • pp.11-14
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    • 2003
  • In the earlier papers we analyzed the axisymmetric, nonstationary electrodynamics of the central black hole and a surrounding thin accretion disk in an active galactic nucleus. Based on those papers we analyze the axisymmetric, nonstationary force-free black hole magnetosphere and the motion of the plasma. We concentrate on deriving the totally new equations for the entropy incrrease and the angular momentum, energy extraction of the black hole.

THE NONSTATIONARY 'GRAD-SHAFRANOV EQUATIONS' IN THE BLACK HOLE MAGNETOSPHERES (시간에 따라 변하는 블랙흘 자기권의 'GRAD-SHAFRANOV 방정식')

  • Park, Seok-Jae;Lee, Tae-Hyeong
    • Publications of The Korean Astronomical Society
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    • v.18 no.1
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    • pp.15-20
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    • 2003
  • In the earlier papers we analyzed the axisymmetric, nonstationary electrodynamics of the central black hole and a surrounding thin accretion disk in an active galactic nucleus. Based on those papers we analyze the axisymmetric, nonstationary black hole magnetosphere in this paper. We concentrate on deriving the ‘Grad-Shafranov equations’; both in the force-free and non-force-free cases. In the time-independent limit our equations naturally coincide with stationary equations as they should.