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Date and Time of the Query: 2019-08-17 T11:36:08 PDT
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For refcode 1995ApJ...448..548C:
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1995ApJ...448..548C COLLISIONS OF ELLIPTICALS AND THE ONSET OF FANAROFF-RILEY TYPE I RADIO SOURCES LUIS COLINA Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD21218 AND LOURDES DE JUAN Departamento de Fisica Teorica, Modulo C-XI, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid, Spain Received 1994 October 11; accepted 1995 February 13 ABSTRACT This paper presents the first detailed quantitative study on the morphological characterization of Fanaroff-Riley type I radio source (FR I) host galaxies. The study is based on a two-dimensional isophote analysis of the largest sample (44) available so far of FR I host galaxies. FR I host galaxies are luminous ellipticals following the same {mu}_e_ - r_e_ relation as nonradio ellipticals. However, a large fraction (60%) of FR I host galaxies in the sample show at least two of the following morphological peculiarities: (1) isophote twists which are larger than 15^deg^, (2) isophote displacements which are larger than 3.5%, (3) excesses over a de Vaucouleurs law which exceeds 0.10 mag arcsec^-2^ at radii beyond r_e_, and (4) one companion galaxy at a distance of less than 50 kpc. These morphological peculiarities are the signature of a recent strong gravitational collision. The collision, involving a pair of ellipticals, is characterized by (1) a median mass ratio (companion to FR I host galaxy) of ~0.2, (2) a median projected distance of ~23 kpc, (3) a median relative velocity of ~492 km s^-1^, (4) a median age of ~4.0 x 10^7^ years, and (5) a median interaction strength parameter of 0.19. Collisions between ellipticals which share the above mentioned mean properties appear. to be very efficient in generating a FR I radio source. Therefore, the scenario of the onset of an active nucleus by galaxy collisions, well established for very luminous starbursts and radio galaxies, can also be extended to FR I radio sources. In a broader scenario, the conclusions of this paper also reinforce the idea that collisions between different type of galaxies give rise to different type of activity in their nuclei: collisions involving two spirals produce luminous circumnuclear starbursts, collisions involving one elliptical and one spiral generate powerful Fanaroff-Riley type II sources (FR II), which collisions between two ellipticals ignite FR I radio sources. Subject headings: galaxies: active - galaxies: elliptical and lenticular, cD - galaxies: interactions - galaxies: photometry - radio continuum: galaxies
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