Low-Luminosity Active Galactic Nuclei: Are They UV-Faint and Radio Loud?
| dc.creator | Maoz, Dan | |
| dc.date | 2007-02-12 | |
| dc.date | 2007-03-14 | |
| dc.date.accessioned | 2026-07-07T11:00:50Z | |
| dc.date.available | 2026-07-07T11:00:50Z | |
| dc.description | Low-luminosity AGNs are perceived to be radio loud and devoid of a ``big blue bump'', indicating a transition from a radiatively efficient, geometrically thin, accretion disc in high-luminosity AGNs, to a geometrically thick, radiatively inefficient accretion flow at low luminosities and accretion rates. I revisit the issue of the spectral energy distributions (SEDs) of low-luminosity AGNs using recently published, high-angular-resolution data at radio, UV, and X-ray wavelengths, for a sample of 13 nearby galaxies with LINER nuclei. I show that, contrary to common wisdom, low-luminosity AGNs have significant nonstellar UV flux, and UV/X-ray luminosity ratios similar, on average, to those of Seyfert 1 nuclei ~10^4 times more luminous. The alpha_ox index that quantifies this ratio is in the range between -0.8 to -1.4, and is below the extrapolation to low luminosities of the relation between alpha_ ox and UV luminosity observed at higher luminosities. In terms of radio loudness, most of the LINERs are indeed radio loud (or sometimes even ``super radio loud'') based on their radio/UV luminosity ratios, when compared to the most luminous quasars. However, the entire distribution of radio loudness has been shown to shift to higher radio/UV ratios at low AGN luminosities. In the context of this global shift, some LINERs (the majority) can be considered radio quiet, and some (from among those with black hole masses >~10^8.5 M_sun) are radio loud. The SEDs of low-luminosity (~10^40 erg/s) AGNs are thus quite similar to those of Seyferts up to luminosities of ~10^44erg/s, and there is no evidence for a sharp change in the SEDs at the lowest luminosities. Thin AGN accretion discs may therefore persist at low accretion rates, in analogy to some recent findings for Galactic stellar-mass accreting black holes. | |
| dc.description | MNRAS, in press | |
| dc.identifier | https://arxiv.org/abs/astro-ph/0702292 | |
| dc.identifier | http://arxiv.org/abs/astro-ph/0702292 | |
| dc.identifier | Mon.Not.Roy.Astron.Soc.377:1696-1710,2007 | |
| dc.identifier | doi:10.1111/j.1365-2966.2007.11735.x | |
| dc.identifier.uri | http://salesiana.dossiersoluciones.com/handle/123456789/187781 | |
| dc.subject | Astrophysics | |
| dc.title | Low-Luminosity Active Galactic Nuclei: Are They UV-Faint and Radio Loud? | |
| dc.type | text |