What Is the Accretion Rate in NGC 4258?

Gammie, Charles F.; Narayan, Ramesh; Blandford, R. D.

doi:10.1086/307089

Cited by 101 publications

(124 citation statements)

References 61 publications

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“…If one believes that at low enough M BH (say, less than 0.1), the accretion Ñow in quasars is made m 5 of an inner ADAF and an outer thin disk, then the increase of for smaller could be due, at least in lL l (X)/lL l (B) M BH part, to an increase of the transition radius, between the R tr , ADAF and the disk, which would result in a reduced optical emission from the disk. This trend seems consistent with the rather large values of in X-ray binaries containing R tr stellar-mass BHs (e.g., Narayan, Barret, & McClintock 1997) and the smaller value in, for example, the active galactic nucleus NGC 4258 (Gammie, Narayan, & Blandford 1999). However, the problem is complicated by the fact that the value of also depends on (see, e.g., Narayan et al R tr m 5 1998 for a discussion).…”

Section: X-ray Versus Optical Datasupporting

confidence: 63%

On the Cosmological Evolution of the Luminosity Function and the Accretion Rate of Quasars

Haiman

Menou

2000

ApJ

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We consider a class of models for the redshift evolution (between of the observed optical 0 [ z [ 4) and X-ray quasar luminosity functions (LFs), with the following assumptions : (1) the mass function of dark matter halos follows the Press-Schechter theory, (2) the black hole (BH) mass scales linearly with the halo mass, (3) quasars have a constant universal lifetime, and (4) a thin accretion disk provides the optical luminosity of quasars, while the X-ray/optical Ñux ratio is calibrated from a sample of observed quasars. The mass accretion rate, onto quasar BHs is a free parameter of the models, which we M 0 , constrain using the observed LFs. The accretion rate inferred from either the optical or X-ray data M 0 under these assumptions generally decreases as a function of cosmic time from z^4 to z^0. We Ðnd that a comparable accretion rate is inferred from the X-ray and optical LF only if the X-ray/optical Ñux ratio decreases with BH mass. Near z^0, drops to substantially sub-Eddington values at which M 0 advection-dominated accretion Ñows (ADAFs) exist. Such a decline of possibly followed by a tran-M 0 , sition to radiatively inefficient ADAFs, could explain both the absence of bright quasars in the local universe and the faintness of accreting BHs at the centers of nearby galaxies. We argue that a decline of the accretion rate of the quasar population is indeed expected in cosmological structure formation models.

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Section: X-ray Versus Optical Datasupporting

confidence: 63%

On the Cosmological Evolution of the Luminosity Function and the Accretion Rate of Quasars

Haiman

Menou

2000

ApJ

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“…In new investigations of the low luminosity galactic nuclei of M 81 and NGC 4579 evidence was found for thin disks truncated at about 100 Schwarzschild radii, similar to the result for NGC 4258 (Gammie et al 1999). The low luminosity in the elliptical galaxy M 87 (NGC 4486) was pointed out by Reynolds et al (1996), illustrating the problem of a "quiescent" black hole.…”

Section: Introductionmentioning

confidence: 62%

“…1) with results from fits of observed spectra. Mass accretion rates and radii from various investigations: elliptical galaxies from Di Matteo et al (2000) (best and second-best fit), low-luminosity AGN M81 and NGC 4579 from , NGC 4258 from Gammie et al (1999), Sgr A * , NGC 4649 and the same value for V404 Cyg from , value for M87 (without wind) from Reynolds et al (1996). Filled symbols correspond to fits without wind loss, open symbols with wind loss.…”

Section: Discussionmentioning

confidence: 99%

Truncation of geometrically thin disks around massive black holes in galactic nuclei

Liu

Meyer-Hofmeister

2001

A&A

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Abstract. The concept of an advection-dominated accretion flow (ADAF), with or without wind loss, was used to describe the spectra of the galactic center source SgrA * , low-luminosity AGN and nuclei of elliptical galaxies (including M 87). The spectral fits of various authors show that the transition from the geometrically thin disk to the hot flow occurs at quite different distances, apparently not uniquely related to the mass flow rate in the disk. We compare these results with the results of theoretical modeling where we determine the truncation of the thin outer disk from the efficiency of mass evaporation. The physics is the same as in the case of galactic black holes systems (Meyer et al. 2000b). For the observationally indicated mass flow rates our model predicts a truncation at 10 3 to 10 4 Schwarzschild radii. We discuss whether far inside this truncation an innermost cool thin disk could exist and affect the spectrum.

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“…A RIAF model has been suggested as a solution for the low luminosity observed in a number of LINERsI/LLAGN; M 81 and NGC 4579 (Quataert et al 1999), NGC 4258 (Gammie et al 1999), NGC 3998 (Ptak et al 2004), NGC 1097 (Nemmen et al 2006), and, more recently, for a sample of 24 LINER sources (Nemmen et al 2010). Authors of these papers emphasize the fact that SEDs of LLAGN in general are in fact different than normal Seyfert SEDs.…”

Section: Ngc 4278 Sed Comparison To Other Llagnmentioning

confidence: 99%

X-ray and multiwavelength view of NGC 4278

Younes

Porquet

Sabra

et al. 2010

A&A

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Context. The emission mechanism responsible for the bulk of energy from radio to X-rays in low ionization emission line regions (LINERs) and low luminosity active galactic nuclei (LLAGN) has been long debated. Based on UV to X-ray and radio to UV flux ratios, some argue that LINERs/LLAGN are a scaled-down version of their more luminous predecessors Seyfert galaxies. Others, based on the lack of X-ray short (hours) time-scale variability, the non detection of an iron line at 6.4 keV, and the faint UV emission compared to typical AGNs, suggest the truncation of the classical thin accretion disk in the inner regions of the AGN where a radiatively inefficient accretion flow (RIAF) structure forms. Aims. We investigate the LINER-Seyfert connection by studying the unabsorbed LINER galaxy NGC 4278 that accretes at a low rate (L bol/Edd ∼ 7 × 10 −6 ) but exhibits a broad Hα line, and a point-like nucleus in radio, optical, UV and X-rays. Methods. We analyzed one XMM-Newton and seven Chandra X-ray observations of NGC 4278 spread over a three year period, allowing the study of the X-ray variability at different time-scales (hours, months, years). We also examined the radio to X-ray spectral energy distribution to constrain the accretion mode in the nucleus of NGC 4278. Results. Long time-scale (months) variability is observed where the flux increased by a factor of ∼3 on a time-scale of a few months and by a factor of 5 between the faintest and the brightest observation separated by ∼3 years. During the XMM-Newton observation, where the highest flux level is detected, we found a 10% flux increase on a short time-scale of a few hours, while the light curves for the different Chandra observations do not show short time-scale (minutes to hours) variability. A combination of an absorbed power law (N H ≈ 10 20 cm −2 , Γ = 2.2 +0.1 −0.2 ) plus a thermal component (kT ≈ 0.6 keV) were able to fit the Chandra spectra. The XMM-Newton spectra, where the highest X-ray flux is detected, are well fitted with an absorbed power-law with no need for a thermal component as the emission from the power-law component is dominant. The power-law photon index is ∼2.1 and the hydrogen column density is of the order of 10 20 cm −2 . Neither a narrow nor a broad Fe Kα emission line at 6.4 keV are detected with a 22 eV and 118 eV upper limits derived on their equivalent widths. We derive optical fluxes from archival HST ACS observations and detected optical variability on time-scales of years. For the first time for this source, thanks to the optical/UV monitor on board XMM-Newton, we obtained simultaneous UV and X-ray flux measurements. We constructed SEDs based on simultaneous or quasi simultaneous observations and compared them to LINER, radio-loud, and radio-quiet quasar SEDs. We find that at a low X-ray flux the NGC 4278 SED resembles that of typical LINER sources where the radio to X-ray emission can be considered as originating from a jet and/or RIAF, whereas at a high X-ray flux, NGC 4278 SED is more like a low luminosity Seyfert SED...

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What Is the Accretion Rate in NGC 4258?

Cited by 101 publications

References 61 publications

On the Cosmological Evolution of the Luminosity Function and the Accretion Rate of Quasars

On the Cosmological Evolution of the Luminosity Function and the Accretion Rate of Quasars

Truncation of geometrically thin disks around massive black holes in galactic nuclei

X-ray and multiwavelength view of NGC 4278

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