The active elliptical galaxy NGC 1052

Fosbury, R. A. E.; Mebold, U.; Goss, W. M.; Dopita, M. A.

doi:10.1093/mnras/183.4.549

Cited by 104 publications

(90 citation statements)

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“…In this paper we focus on the radio properties of the ∼200 LLAGNs and AGNs (median distance ∼17 Mpc) in the Palomar spectroscopic sample of ∼488 bright northern galaxies (Ho et al 1997a). The weak emissionlines of the Palomar LLAGNs can be modeled in terms of photoionization by hot, young stars (Terlevich & Melnick 1985;Filippenko & Terlevich 1992;Shields 1992), by collisional ionization in shocks (Koski & Osterbrock 1976;Fosbury et al 1978;Heckman 1980;Dopita & Sutherland 1995) or by starbursts (Alonso-Herrero et al 1999). Alternatively, they could trace AGNs accreting either at very low accretion rates (with radiated luminosity as low as ∼10 −2 −10 −7 of the Eddington Luminosity, L Eddington ), or at radiative efficiencies (the ratio of radiated energy to accreted mass) much lower than the typical value of ∼10% (e.g.…”

Section: Accretion Activity: Ubiquity and Scalingmentioning

confidence: 99%

Radio sources in low-luminosity active galactic nuclei

Nagar¹,

Falcke²,

Wilson³

2005

A&A

308

482

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Abstract. We present the completed results of a high resolution radio imaging survey of all (∼200) low-luminosity active galactic nuclei (LLAGNs) and AGNs in the Palomar Spectroscopic Sample of all (∼488) bright northern galaxies. The high incidences of pc-scale radio nuclei, with implied brightness temperatures > ∼ 10 7 K, and sub-parsec jets argue for accreting black holes in > ∼ 50% of all LINERs and low-luminosity Seyferts; there is no evidence against all LLAGNs being mini-AGNs. The detected parsec-scale radio nuclei are preferentially found in massive ellipticals and in type 1 nuclei (i.e. nuclei with broad Hα emission). The radio luminosity function (RLF) of Palomar Sample LLAGNs and AGNs extends three orders of magnitude below, and is continuous with, that of "classical" AGNs. We find marginal evidence for a low-luminosity turnover in the RLF; nevertheless LLAGNs are responsible for a significant fraction of present day mass accretion. Adopting a model of a relativistic jet from Falcke & Biermann, we show that the accretion power output in LLAGNs is dominated by the kinetic power in the observed jets rather than the radiated bolometric luminosity. The Palomar LLAGNs and AGNs follow the same scaling between jet kinetic power and narrow line region (NLR) luminosity as the parsec to kilo-parsec jets in powerful radio galaxies. Eddington ratios l Edd (=L Emitted /L Eddington ) of ≤10 −1 −10 −5 are implied in jet models of the radio emission. We find evidence that, in analogy to Galactic black hole candidates, LINERs are in a "low/hard" state (gas poor nuclei, low Eddington ratio, ability to launch collimated jets) while low-luminosity Seyferts are in a "high" state (gas rich nuclei, higher Eddington ratio, less likely to launch collimated jets). In addition to dominating the radiated bolometric luminosity of the nucleus, the radio jets are energetically more significant than supernovae in the host galaxies, and are potentially able to deposit sufficient energy into the innermost parsecs to significantly slow the gas supply to the accretion disk.

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Section: Accretion Activity: Ubiquity and Scalingmentioning

confidence: 99%

Radio sources in low-luminosity active galactic nuclei

Nagar¹,

Falcke²,

Wilson³

2005

A&A

308

482

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“…Shock heating was initially proposed as a viable excitation mechanism to solve the so-called "temperature problem" of Seyferts and LINERs, in which the electron temperatures observed were found to be systematically higher than predicted by photoionization models. Koski & Osterbrock (1976) and Fosbury et al (1978) argued that shocks are essential for explaining the observed [OIII] line ratios of the prototypical LINER NGC 1052. Dopita & Sutherland (1995) and Allen et al (2008) presented extensive grids of high velocity shock models, and showed that the emission line ratios observed in LINERs can be modeled in terms of fast shocks (150-500 km s −1 ) in a relatively gas poor environment.…”

Section: Comparison With Modelsmentioning

confidence: 99%

Nearby early-type galaxies with ionized gas

Annibali

Bressan

Rampazzo

et al. 2010

A&A

122

162

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Aims. A significant fraction of early-type galaxies (ETGs) exhibit emission lines in their optical spectra. We attempt to identify the producing the emission mechanism and the ionized gas in ETGs, and its connection with the host galaxy evolution. Methods. We analyzed intermediate-resolution optical spectra of 65 ETGs, mostly located in low density environments and exhibiting spectros-copic diagnostic lines of ISM from which we had previously derived stellar population properties. To extract the emission lines from the galaxy spectra, we developed a new fitting procedure that accurately subtracts the underlying stellar continuum, and accounts for the uncertainties caused by the age-metallicity degeneracy. Results. Optical emission lines are detected in 89% of the sample. The incidence and strength of emission correlate with neither the E/S0 classification, nor the fast/slow rotator classification. By means of the classical [OIII]/Hβ versus [NII]/Hα diagnostic diagram, the nuclear galaxy activity is classified such that 72% of the galaxies with emission are LINERs, 9% are Seyferts, 12% are composite/transition objects, and 7% are non-classified. Seyferts have young luminostiy-weighted ages ( 5 Gyr), and appear, on average, significantly younger than LINERs and composites. Excluding the Seyferts from our sample, we find that the spread in the ([OIII], Hα, or [NII]) emission strength increases with the galaxy central velocity dispersion σ c . Furthermore, the [NII]/Hα ratio tends to increase with σ c . The [NII]/Hα ratio decreases with increasing galactocentric distance, indicative of either a decrease in the nebular metallicity, or a progressive "softening" of the ionizing spectrum. The average nebular oxygen abundance is slightly less than solar, and a comparison with the results obtained in Paper III from Lick indices shows that it is ≈0.2 dex lower than that of stars. Conclusions. The nuclear (r < r e /16) emission can be attributed to photoionization by PAGB stars alone only for ≈22% of the LINER/composite sample. On the other hand, we cannot exclude an important role of PAGB star photoionization at larger radii. For the major fraction of the sample, the nuclear emission is consistent with excitation caused by either a low-accretion rate AGN or fast shocks (200-500 km s −1 ) in a relatively gas poor environment (n 100 cm −3 ), or both. The derived [SII]6717/6731 ratios are consistent with the low gas densities required by the shock models. The derived nebular metallicities are indicative of either an external origin of the gas, or an overestimate of the oxygen yields by SN models.

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“…low-luminosity Seyferts, LINERs, and "transition" nuclei [nuclei with spectra intermediate between those of LINERs and H II regions]) is a continuing one. Their low emission-line luminosities (L Hα ≤ 10 40 erg s −1 by definition, Ho et al 1997a, hereafter H97a) can be modeled in terms of photoionization by hot, young stars (Terlevich & Melnick 1985;Filippenko & Terlevich 1992;Shields 1992), by collisional ionization in shocks (Koski & Osterbrock 1976;Fosbury et al 1978;Heckman 1980;Dopita & Sutherland 1995) or by aging starbursts (Alonso-Herrero et al 1999). …”

Section: Introductionmentioning

confidence: 99%

Radio sources in low-luminosity active galactic nuclei

Nagar

Falcke²,

Wilson³

et al. 2002

A&A

200

312

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Abstract. This paper presents the results of a high resolution radio imaging survey of all known (96) low-luminosity active galactic nuclei (LLAGNs) at D ≤ 19 Mpc. We first report new 2 cm (150 mas resolution using the VLA) and 6 cm (2 mas resolution using the VLBA) radio observations of the previously unobserved nuclei in our samples and then present results on the complete survey. We find that almost half of all LINERs and low-luminosity Seyferts have flat-spectrum radio cores when observed at 150 mas resolution. Higher (2 mas) resolution observations of a flux-limited subsample have provided a 100% (16 of 16) detection rate of pc-scale radio cores, with implied brightness temperatures > ∼ 10 8 K. The five LLAGNs with the highest core radio fluxes also have pc-scale "jets". Compact radio cores are almost exclusively found in massive ellipticals and in type 1 nuclei (i.e. nuclei with broad Hα emission). Only a few "transition" nuclei have compact radio cores; those detected in the radio have optical emission-line diagnostic ratios close to those of LINERs/Seyferts. This indicates that some transition nuclei are truly composite Seyfert/LINER+H II region nuclei, with the radio core power depending on the strength of the former component. The core radio power is correlated with the nuclear optical "broad" Hα luminosity, the nuclear optical "narrow" emission-line luminosity and width, and with the galaxy luminosity. In these correlations LLAGNs fall close to the low-luminosity extrapolations of more powerful AGNs. The scalings suggest that many of the radio-non-detected LLAGNs are simply lower power versions of the radio-detected LLAGNs. The ratio of core radio power to nuclear optical emissionline luminosity increases with increasing bulge luminosity for all LLAGNs. Also, there is evidence that the luminosity of the disk component of the galaxy is correlated with the nuclear emission-line luminosity (but not the core radio power). About half of all LLAGNs with multiple epoch data show significant inter-year radio variability. Investigation of a sample of ∼150 nearby bright galaxies, most of them LLAGNs, shows that the nuclear (≤150 mas size) radio power is strongly correlated with both the black hole mass and the galaxy bulge luminosity; linear regression fits to all ∼150 galaxies give: log P 2 cm = 1.31(±0.16) log M MDO + 8.77 and log P 2 cm = 1.89(±0.21) log L B (bulge) − 0.17. Low accretion rates (≤10 −2 −10 −3 of the Eddington rate) are implied in both advection-and jet-type models. In brief, all evidence points towards the presence of accreting massive black holes in a large fraction, perhaps all, of LLAGNs, with the nuclear radio emission originating in either the accretion inflow onto the massive black hole or from jets launched by this black hole-accretion disk system.

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The active elliptical galaxy NGC 1052

Cited by 104 publications

References 0 publications

Radio sources in low-luminosity active galactic nuclei

Radio sources in low-luminosity active galactic nuclei

Nearby early-type galaxies with ionized gas

Radio sources in low-luminosity active galactic nuclei

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