Radio Sources in Low-Luminosity Active Galactic Nuclei. II. Very Long Baseline Interferometry Detections of Compact Radio Cores and Jets in a Sample of LINERs
By Heino Falcke, N. Wilson, J. Ulvestad. 2000
138 citations recorded by the source corpus.
We have used the VLBA at 5 GHz to observe all galaxies with nuclear radio flux densities above 3.5 mJy found in a VLA survey at 15 GHz of a sample of nearby LINER galaxies. All galaxies were detected revealing high brightness temperature (Tb ≳ 108 K) radio sources. Free-free emission is unlikely since it greatly overpredicts the soft X-ray luminosities. We infer the presence of active galactic nucleus (AGN)-like, nonthermal radio emission most likely powered by underfed black holes. Together with our VLA sample we estimate from our observations that at least one-half of LINER galaxies host genuine AGNs. We find no evidence for highly inverted radio cores as predicted in the advection-dominated accretion flow model: the (nonsimultaneous) spectral indices are on average around α = 0.0. In the two brightest sources we detect some extended emission, which appears to originate in jets in at least one of these galaxies. Together with the spectral indices this suggests that the nuclear emission at centimeter radio waves is largely dominated by emission from radio jets, very similar to the situation in more luminous AGNs. The energy released in these jets could be a significant fraction of the energy budget in the accretion flow.
Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics
View Paper: https://www.semanticscholar.org/paper/dd22fca5612f92c34c4c1104374f928ba678d5e6
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Citations in the corpus
- Hot Accretion Flows Around Black Holes (2014, background): “…such an association has accumulated in recent years with the recognition that essentially all low-luminosity AGNs are radio loud (Nagar et al. 2000, Falcke et al. 2000, Ho 2002) and the parallel discovery that virtually every BHB in the hard state has radio emission (Corbel et al. 2000; Fender…”
- X-Ray Properties of LINERs and Low-Luminosity Seyfert Galaxies Observed with ASCA. I. Observations and Results (2002, background): “Finally, the radio properties further support the AGN interpretation: the nucle s contains a compact radio core which has a flat spectrum (Nagar et al. 2000; Falcke et al. 2000) and is variable (Falcke et al. 2001; Ho & Ulvestad 2001).”
- Coronal outflow dominated accretion discs: a new possibility for low-luminosity black holes? (2001, background): “In addition, VLA (Nagar et al. 2000) and VLBA (Falcke et al. 2000) radio observationsf LLAGN have revealed flat or inverted compact radio cores, with an incidence higher than in the case of normal Seyfert galaxies, and, for the sources observed at higher spatial resolution with VLBA, very high…”
- The host galaxies and classification of active galactic nuclei (2006, background): “…& Halpern 2001; Storchi-Bergmann et al. ⋆ Hubble Fellow; kewley@ifa.hawaii.edu 1997; Bower et al. 1996), while others have compact radio cores (Falcke et al. 2000; Ulvestad & Ho 2001; Filho et al. 2002, 2004; Anderson et al. 2004), evidence for hard Xray spectra (Terashima et al. 2000; Ho…”
- Nuclear Activity in Nearby Galaxies (2008, background): “…structures akin to subparsec-scale jets, but most of the power is concentrated in a compact, high-brightness temperature core (Bietenholz, Bartel & Rupen 2000; Falcke et al. 2000; Ulvestad & Ho 2001b; Filho, Barthel & Ho 2002b; Anderson, Ulvestad & Ho 2004; Filho et al. 2004; Krips et al. 2007).”
- Black hole accretion discs in the canonical low‐hard state (2009, methodology): “However, an alternative, jet-dominated accretion flow explanation has also been successfully applied to these sources (Sgr A∗: Falcke & Biermann 1999; Falcke & Markoff 2000; LLAGNs: Falcke et al. 2000).”
- Radio sources in low-luminosity active galactic nuclei IV. Radio luminosity function, importance of jet power, and radio properties of the complete Palomar sample (2005, methodology): “The implied brightness temperatures were calculated using the formula given in Falcke et al. (2000); the results are in the range >106.3 K to >∼1010.8 K.”
- Radio Sources in Low-Luminosity Active Galactic Nuclei. III (2002, methodology): “The implied brightness temperatures were calculated using the formula given in Falcke et al. (2000); the results are in the range 106.8 to 109.5 K.”
- The Murmur of the Sleeping Black Hole: Detection of Nuclear Ultraviolet Variability in LINER Galaxies (2005, background): “Anderson et al. (2004) have obtainedmultifrequencyVLBA spectra for the unresolved milliarcsecond core in six low-luminosity AGNs (including three LINERs, two of which, NGC 4203 and NGC 4579, are in our sample).”