Low-ionization nuclear emission-line region
A low-ionization nuclear emission-line region (LINER) is a type of
Demographics of LINER galaxies
Galaxies that contain LINERs are often referred to as LINER galaxies. LINER galaxies are very common; approximately one-third of all nearby galaxies (galaxies within approximately 20-40
Scientific debates: energy sources and ionization mechanisms
LINERs have been at the center of two major debates. First, astronomers have debated the source of energy that excites the ionized gas in the centers of these galaxies. Some astronomers have proposed that
These debates are complicated by the fact that LINERs are found in a wide variety of objects with different brightnesses and morphologies. Moreover, the debate over the energy sources for LINERs is entangled with a similar debate over whether the light from star formation regions or the light from AGN produce the high infrared luminosities seen in LIRGs.[4]
Although both the energy sources and the excitation mechanisms for LINER emission are still being studied, many LINERs are frequently referred to as AGN.[1]
Star formation in LINERs
A number of surveys have been performed to explore the connection between star formation and LINER activity. If a connection can be found between star formation activity and LINER activity, then this strengthens the possibility that LINERs are powered by the hot gas found in star formation regions. However, if star formation cannot be found in LINERs, then this definitively excludes star formation as powering LINER emission.
Star formation in LIRGs with LINERs
Recent observations with the
Star formation in normal galaxies with LINERs
Normal nearby galaxies with LINERs, however, appear to be different. A few near-infrared spectroscopic surveys have identified some LINERs in normal galaxies that may be powered by star formation.[9] However, most LINERs in nearby galaxies have low levels of star formation activity.[9][10][11] Moreover, the stellar populations of many LINERs appear to be very old,[12][13][11] and the mid-infrared spectra, as observed by the Spitzer Space Telescope, do not appear similar to the spectra expected from star formation.[8] These results demonstrate that most LINER in nearby normal galaxies may not be powered by star formation, although a few exceptions clearly exist.
Notable LINER galaxies
See also
- Seyfert galaxy - Another class of galaxies that contain AGN
References
- ^ a b c d e f
L. C. Ho; A. V. Filippenko; W. L. W. Sargent (1997). "A Search for "Dwarf" Seyfert Nuclei. III. Spectroscopic Parameters and Properties of the Host Galaxies". Astrophysical Journal Supplement. 112 (2): 315–390. S2CID 17086638.
- ^ a b c d e
T. M. Heckman (1980). "An optical and radio survey of the nuclei of bright galaxies - Activity in normal galactic nuclei". Bibcode:1980A&A....87..152H.
- ^ a b
L. C. Ho; A. V. Filippenko; W. L. W. Sargent (1997). "A Search for "Dwarf" Seyfert Nuclei. V. Demographics of Nuclear Activity in Nearby Galaxies". Astrophysical Journal. 487 (2): 568–578. S2CID 16742031.
- ^ a b
S. Veilleux; D.-C. Kim; D. B. Sanders; J. M. Mazzarella; B. T. Soifer (1995). "Optical Spectroscopy of Luminous Infrared Galaxies. II. Analysis of the Nuclear and Long-Slit Data". Astrophysical Journal Supplement Series. 98: 171–217. doi:10.1086/192158.
- ^ doi:10.1086/173291.
- ^ a b R. Terlevich; J. Melnick (1985). "Warmers - The missing link between Starburst and Seyfert galaxies". .
- ^ a b
J. C. Shields (1992). "Normal O stars in dense media generate LINERs". Astrophysical Journal Letters. 399: L27–L30. doi:10.1086/186598.
- ^ a b
E. Sturm; D. Rupke; A. Contursi; D.-C. Kim; D. Lutz; H. Netzer; S. Veilleux; R. Genzel; M. Lehnert; L. J. Tacconi; D. Maoz; J. Mazzarella; S. Lord; D. Sanders; A. Sternberg (2006). "Mid-Infrared Diagnostics of LINERS". Astrophysical Journal Letters. 653 (1): L13–L16. S2CID 51798661.
- ^ S2CID 15514939.
- S2CID 119506664.
- ^ S2CID 14169689.
- S2CID 119101213.)
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