Black Hole Fundamental Plane Research Articles

X-Ray Properties of Radio-selected Dual Active Galactic Nuclei

Abstract Merger simulations predict that tidally induced gas inflows can trigger kiloparsec-scale dual active galactic nuclei (dAGN) in heavily obscured environments. Previously, with the Very Large Array, we have confirmed four dAGN with redshifts between 0.04 < z < 0.22 and projected separations between 4.3 and 9.2 kpc in the Sloan Digital Sky Survey Stripe 82 field. Here, we present Chandra X-ray observations that spatially resolve these dAGN and compare their multiwavelength properties to those of single AGN from the literature. We detect X-ray emission from six of the individual merger components and obtain upper limits for the remaining two. Combined with previous radio and optical observations, we find that our dAGN have properties similar to nearby low-luminosity AGN, and they agree with the black hole fundamental plane relation well. There are three AGN-dominated X-ray sources, whose X-ray hardness-ratio derived column densities show that two are unobscured and one is obscured. The low obscured fraction suggests these dAGN are no more obscured than single AGN, in contrast to the predictions from simulations. These three sources show an apparent X-ray deficit compared to their mid-infrared continuum and optical [O iii] line luminosities, suggesting higher levels of obscuration, in tension with the hardness-ratio derived column densities. Enhanced mid-infrared and [O iii] luminosities from star formation may explain this deficit. There is ambiguity in the level of obscuration for the remaining five components because their hardness ratios may be affected by nonnuclear X-ray emissions, or are undetected altogether. They require further observations to be fully characterized.

The black hole fundamental plane in low-excitation radio galaxies

ABSTRACT The radio–X-ray slope in the fundamental plane of radio-loud active galactic nuclei (AGNs) has been found to be steeper than that of radio-quiet AGNs in previous studies. In this paper, we reinvestigate the fundamental plane in radio-loud AGNs by compiling a sample of 13 low-excitation radio galaxies (LERGs) from the 3CR radio galaxies, for the reason that the accretion mode in LERGs is believed to be a radiatively inefficient accretion flow. All the sources in our sample have data available both at the 5-GHz core radio luminosity as detected by VLA/VLBI/VLBA and at the core X-ray luminosity as detected by Chandra/XMM–Newton. Surprisingly, we find that the slope in the fundamental plane (logLR = 0.52log LX + 0.84log MBH + 10.84) of LERGs is consistent with that reported by Merloni et al. However, the normalization is found to be shifted by about 0.7 dex, which could be due to the difference in the magnetic field strength in different objects. A shallower slope of the LR−LX relationship ($L_{\rm R}\sim L_{\rm X}^{0.63}$) is also found for our sample, which demonstrates that the X-ray emission in LERGs may come from the accretion disc, rather than jets suggested by previous works.

Determining the radio active galactic nuclei contribution to the radio–far-infrared correlation using the black hole Fundamental Plane relation

We investigate the 1.4 GHz radio properties of 92 nearby (z<0.05) ultra hard X-ray selected Active Galactic Nuclei (AGN) from the Swift Burst Alert Telescope (BAT) sample. Through the ultra hard X-ray selection we minimise the biases against obscured or Compton-thick AGN as well as confusion with emission derived from star formation that typically affect AGN samples selected from the UV, optical and infrared wavelengths. We find that all the objects in our sample of nearby, ultra-hard X-ray selected AGN are radio quiet; 83\% of the objects are classed as high-excitation galaxies (HEGs) and 17\% as low-excitation galaxies (LEGs). While these low-z BAT sources follow the radio--far-infrared correlation in a similar fashion to star forming galaxies, our analysis finds that there is still significant AGN contribution in the observed radio emission from these radio quiet AGN. In fact, the majority of our BAT sample occupy the same X-ray--radio fundamental plane as have been observed in other samples, which include radio loud AGN --- evidence that the observed radio emission (albeit weak) is connected to the AGN accretion mechanism, rather than star formation.

On the radio luminosity distribution of active galactic nuclei and the black hole fundamental plane

We have studied the dependence of the nuclear radio (1.4 GHz) luminosity of active galactic nuclei (AGN) on both 2–10 keV X-ray and host-galaxy K-band luminosities. A complete sample of 1268 X-ray-selected AGN (both type 1 and type 2) has been used, which is the largest catalogue of AGN belonging to statistically well-defined samples where radio, X-ray and K-band information exists. At variance with previous studies, radio upper limits have been taken into account statistically using a Bayesian maximum-likelihood fitting method. A good fit is obtained assuming a plane in 3D LR–LX–LK space, namely log LR = ξX log LX + ξK log LK + ξ0, with a ∼1 dex wide (1σ) spread in radio luminosity. As already shown by La Franca, Melini & Fiore, no evidence of bimodality in the radio luminosity distribution was found and therefore any definition of radio-loudness in AGN is arbitrary. Using scaling relations between the black hole (BH) mass and the host galaxy K-band luminosity, we have also derived a new estimate of the BH fundamental plane (in L5 GHz–LX–MBH space). Our analysis shows that previous measures of the BH fundamental plane are biased by ∼0.8 dex in favour of the most luminous radio sources. Therefore, many AGN studies, where the BH fundamental plane is used to investigate how AGN regulate their radiative and mechanical luminosity as a function of the accretion rate, and many AGN/galaxy co-evolution models, where radio feedback is computed using the AGN fundamental plane, should revise their conclusions.

Growing massive black holes in a Local Group environment: the central supermassive, slowly sinking and ejected populations

We explore the growth of < 10^7 Msun black holes that reside at the centers of spiral and field dwarf galaxies in a Local Group type of environment. We use merger trees from a cosmological N-body simulation known as Via Lactea II (VL-2) as a framework to test two merger-driven semi-analytic recipes for black hole growth that include dynamical friction, tidal stripping, and gravitational wave recoil in over 20,000 merger tree realizations. First, we apply a Fundamental Plane limited (FPL) model to the growth of Sgr A*, which drives the central black hole to a maximum mass limited by the Black Hole Fundamental Plane after every merger. Next, we present a new model that allows for low-level Prolonged Gas Accretion (PGA) during the merger. We find that both models can generate a Sgr A* mass black hole. We predict a population of massive black holes in local field dwarf galaxies - if the VL-2 simulation is representative of the growth of the Local Group, we predict up to 35 massive black holes (< 10^6 Msun) in Local Group field dwarfs. We also predict that hundreds of < 10^5 Msun black holes fail to merge, and instead populate the Milky Way halo, with the most massive of them at roughly the virial radius. In addition, we find that there may be hundreds of massive black holes ejected from their hosts into the nearby intergalactic medium due to gravitational wave recoil. We discuss how the black hole population in the Local Group field dwarfs may help to constrain the growth mechanism for Sgr A*.

RELATION BETWEEN GLOBULAR CLUSTERS AND SUPERMASSIVE BLACK HOLES IN ELLIPTICALS AS A MANIFESTATION OF THE BLACK HOLE FUNDAMENTAL PLANE

We analyze the relation between the mass of the central supermassive black hole (Mbh) and the number of globular clusters (Ngc) in elliptical galaxies and bulges as a ramification of the black hole fundamental plane, the theoretically predicted and observed multi-variable correlation between Mbh and bulge binding energy. Although the tightness of the Mbh-Ngc correlation suggests an unlikely causal link between supermassive black holes and globular clusters, such a correspondence can exhibit small scatter even if the physical relationship is indirect. We show that the relatively small scatter of the Mbh-Ngc relation owes to the mutual residual correlation of Mbh and Ngc with stellar mass when the velocity dispersion is held fixed. Thus, present observations lend evidence for feedback-regulated models in which the bulge binding energy is most important; they do not necessarily imply any `special' connection between globular clusters and Mbh. This raises the question of why Ngc traces the formation of ellipticals and bulges sufficiently well to be correlated with binding energy.

The Black Hole Fundamental Plane: Revisited with a Larger Sample of Radio and X‐Ray–Emitting Broad‐Line AGNs

We use a recently released SDSS catalog of X-ray-emitting AGNs in conjunction with the FIRST radio survey to investigate the black hole (BH) fundamental plane relationship between the 1.4 GHz radio luminosity ( -->Lr), 0.1-2.4 keV X-ray luminosity ( -->LX), and black hole mass ( -->M), namely, -->log Lr = ξRXlog LX + ξRMlog M + constant . For this purpose, we compile a large sample of 725 broad-line AGNs, which consists of 498 radio-loud sources and 227 radio-quiet sources. We confirm that radio-loud objects have a steeper slope ( -->ξRX) with respect to radio-quiet objects and that the dependence of the BH fundamental plane on the BH mass ( -->ξRM) is weak. We also find tight correlation with a similar slope between the soft X-ray luminosity and broad emission-line luminosity for both radio-loud and radio-quiet AGNs, which implies that their soft X-ray emission is unbeamed and probably related to the accretion process. With the current larger sample, we find that there is no clear evidence of evolution for radio-quiet AGNs, while for radio-loud ones there is a weak trend in which -->ξRM decreases as the redshift increases. This may be understood in part as due to the observed evolution of the radio spectral index as a function of redshift. Finally, we discuss the relativistic beaming effect and other uncertainties related to the BH fundamental plane. We conclude that, although it does introduce scatter into the fundamental plane relation, Doppler boosting alone is not enough to explain the observed steeper value of -->ξRX in the radio-loud subsample with respect to the radio-quiet ones.

Measuring supermassive black holes with gas kinematics

We present results from a kinematical study of the gas in the nucleus of a sample of three LINER galaxies, obtained from archival HST/STIS long-slit spectra. We found that, while for the elliptical galaxy NGC 5077, the observed velocity curves are consistent with gas in regular rotation around the galaxy's center, this is not the case for the two remaining objects. By modeling the surface brightness distribution and rotation curve from the emission lines in NGC 5077, we found that the observed kinematics of the circumnuclear gas can be accurately reproduced by adding to the stellar mass component a black hole mass of M BH = 6.8 +4.3 -2.8 x 10 8 M ⊙ (uncertainties at a 1σ level); the radius of its sphere of influence (R sph ∼ 0.34) is well-resolved at the HST resolution. The BH mass estimate in NGC 5077 is in fairly good agreement with both the M BH - M bul (with an upward scatter of ∼0.4 dex) and M BH - σ correlations (with an upward scatter of 0.5 dex in the Tremaine et al. form and essentially no scatter using the Ferrarese et al. form) and provides further support for the presence of a connection between the residuals from the M BH - cr correlation and the bulge effective radius. This indicates the presence of a black hole's fundamental plane in the sense that a combination of at least σ and R e drives the correlations between M BH and host bulge properties.

A Supermassive Black Hole Fundamental Plane for Ellipticals

We obtain the coefficients of a new fundamental plane for supermassive black holes at the centers of elliptical galaxies, involving measured central black hole mass and photometric parameters that define the light distribution. The galaxies are tightly distributed around this mass fundamental plane, with improvement in the rms residual over those obtained from the MBH-σ and MBH-L relations. This implies a strong multidimensional link between central massive black hole formation and global photometric properties of elliptical galaxies, and provides an improved estimate of black hole mass from galaxy data.

The Black Hole Fundamental Plane from a Uniform Sample of Radio and X‐Ray‐emitting Broad‐Line AGNs

We derived the black hole fundamental plane relationship among the 1.4GHz radio luminosity (L_r), 0.1-2.4keV X-ray luminosity (L_X), and black hole mass (M) from a uniform broad line SDSS AGN sample including both radio loud and radio quiet X-ray emitting sources. We found in our sample that the fundamental plane relation has a very weak dependence on the black hole mass, and a tight correlation also exists between the Eddington luminosity scaled X-ray and radio luminosities for the radio quiet subsample. Additionally, we noticed that the radio quiet and radio loud AGNs have different power-law slopes in the radio--X-ray non-linear relationship. The radio loud sample displays a slope of 1.39, which seems consistent with the jet dominated X-ray model. However, it may also be partly due to the relativistic beaming effect. For radio quiet sample the slope of the radio--X-ray relationship is about 0.85, which is possibly consistent with the theoretical prediction from the accretion flow dominated X-ray model. We briefly discuss the reason why our derived relationship is different from some previous works and expect the future spectral studies in radio and X-ray bands on individual sources in our sample to confirm our result.