arXiv subjects

S. Heinz

Publications and source records attributed to S. Heinz.

At least 91 records · Page 5Linked to original sources

arXiv2007

Shock heating by FR I radio sources in galaxy clusters

Feedback by active galactic nuclei (AGN) is frequently invoked to explain the cut-off of the galaxy luminosity function at the bright end and the absence of cooling flows in galaxy clusters. Meanwhile, there are recent observations of shock fronts around radio-loud AGN. Using realistic 3D simulations of jets in a galaxy cluster, we address the question what fraction of the energy of active galactic nuclei is dissipated in shocks. We find that weak shocks that encompass the AGN have Mach numbers of 1.1-1.2 and dissipate at least 2% of the mechanical luminosity of the AGN. In a realistic cluster medium, even a continuous jet can lead to multiple shock structures, which may lead to an overestimate of the AGN duty cycles inferred from the spatial distribution of waves.

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arXiv2007

Filaments, Bubbles, and Weak Shocks in the Gaseous Atmosphere of M87

We present the first results from a 500 ksec Chandra ACIS-I observation of M87. At soft energies (0.5-1.0 keV), we detect filamentary structures associated with the eastern and southwestern X-ray and radio arms. Many filaments are spatially resolved with widths of ~300 pc. This filamentary structure is particularly striking in the eastern arm where we suggest the filaments are outer edges of a series of plasma-filled, buoyant bubbles whose ages differ by ~6 x 10^6 years. These X-ray structures may be influenced by magnetic filamentation. At hard energies (3.5-7.5 keV), we detect a nearly circular ring of outer radius 2.8' (13 kpc) which provides an unambiguous signature of a weak shock, driven by an outburst from the SMBH. The density rise in the shock is ~1.3 (Mach number, M~1.2). The observed spectral hardening in the ring corresponds to a temperature rise T_shock / T_0 ~ 1.2, or M~1.2, in agreement with the Mach number derived independently from the gas density. Thus, for the first time, we detect gas temperature and density jumps associated with a classical shock in the atmosphere around a supermassive black hole. We also detect two additional surface brightness edges and pressure enhancements at radii of ~0.6' and ~1'. The ~0.6' feature may be over-pressurized thermal gas surrounding the relativistic plasma in the radio cocoon, the ``piston'', produced by the current episode of AGN activity. The over-pressurized gas is surrounded by a cool gas shell. The ~1' feature may be an additional weak shock from a secondary outburst. In an earlier episode, the ``piston'' was responsible for driving the 2.8' shock.

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arXiv2007

Impact of tangled magnetic fields on AGN-blown bubbles

There is growing consensus that feedback from AGN is the main mechanism responsible for stopping cooling flows in clusters of galaxies. AGN are known to inflate buoyant bubbles that supply mechanical power to the intracluster gas (ICM). High Reynolds number hydrodynamical simulations show that such bubbles get entirely disrupted within 100 Myr, as they rise in cluster atmospheres, which is contrary to observations. This artificial mixing has consequences for models trying to quantify the amount of heating and star formation in cool core clusters of galaxies. It has been suggested that magnetic fields can stabilize bubbles against disruption. We perform MHD simulations of fossil bubbles in the presence of tangled magnetic fields using the high order PENCIL code. We focus on the physically-motivated case where thermal pressure dominates over magnetic pressure and consider randomly oriented fields with and without maximum helicity and a case where large scale external fields drape the bubble.We find that helicity has some stabilizing effect. However, unless the coherence length of magnetic fields exceeds the bubble size, the bubbles are quickly shredded. As observations of Hydra A suggest that lengthscale of magnetic fields may be smaller then typical bubble size, this may suggest that other mechanisms, such as viscosity, may be responsible for stabilizing the bubbles. However, since Faraday rotation observations of radio lobes do not constrain large scale ICM fields well if they are aligned with the bubble surface, the draping case may be a viable alternative solution to the problem. A generic feature found in our simulations is the formation of magnetic wakes where fields are ordered and amplified. We suggest that this effect could prevent evaporation by thermal conduction of cold Halpha filaments observed in the Perseus cluster.

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arXiv2006

Cosmological evolution of the AGN Kinetic Luminosity Function

We present a first attempt to derive the cosmological evolution of the kinetic luminosity function of AGN based on the joint evolution of the flat spectrum radio and hard X-ray selected AGN luminosity functions. An empirical correlation between jet power and radio core luminosity is found, which is consistent with the theoretical assumption that, below a certain Eddington ratio, SMBH accrete in a radiatively inefficient way, while most of the energy output is in the form of kinetic energy. We show how the redshift evolution of the kinetic power density from such a low-mdot mode of accretion makes it a good candidate to explain the so-called ``radio mode'' of AGN feedback as postulated in many galaxy formation schemes.

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arXiv2006

The answer is blowing in the wind: Simulating the interaction of jets with dynamic cluster atmospheres

We present numerical simulations investigating the interaction of AGN jets with galaxy clusters, for the first time taking into account the dynamic nature of the cluster gas and detailed cluster physics. The simulations successfully reproduce the observed morphologies of radio sources in clusters. We find that cluster inhomogeneities and large scale flows have significant impact on the morphology of the radio source and cannot be ignored a-priori when investigating radio source dynamics. Morphological comparison suggests that the gas in the centres of clusters like Virgo and Abell 4059 shows significant shear and/or rotation. We find that shear and rotation in the intra-cluster medium move large amounts of cold material back into the path of the jet, ensuring that subsequent jet outbursts encounter a sufficient column density of gas to couple with the inner cluster gas, thus alleviating the problem of evacuated channels discussed in the recent literature. The same effects redistribute the excess energy Delta_E deposited by the jets, making the distribution of Delta_E at late times consistent with being isotropic.

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arXiv2006

A radio-emitting outflow in the quiescent state of A0620-00: implications for modelling low-luminosity black hole binaries

Deep observations with the Very Large Array of A0620-00, performed in 2005 August, resulted in the first detection of radio emission from a black hole binary at X-ray luminosities as low as 10^{-8.5} times the Eddington limit. The measured radio flux density, of 51 \pm 7 microJy at 8.5 GHz, is the lowest reported for an X-ray binary system so far, and is interpreted in terms of partially self-absorbed synchrotron emission from outflowing plasma. Making use of the estimated outer accretion rate of A0620-00 in quiescence, we demonstrate that the outflow kinetic power must be energetically comparable to the total accretion power associated with such rate, if it was to reach the black hole with the standard radiative efficiency of 10 per cent. This favours a model for quiescence in which a radiatively inefficient outflow accounts for a sizable fraction of the missing energy, and, in turn, substantially affects the overall dynamics of the accretion flow. Simultaneous observations in the X-ray band, with Chandra, confirm the validity of a non-linear radio/X-ray correlation for hard state black hole binaries down to low quiescent luminosities, thereby contradicting some theoretical expectations. Taking the mass term into account, the A0620-00 data lie on the extrapolation of the so called Fundamental Plane of black hole activity, which has thus been extended by more than 2 orders of magnitude in radio and X-ray luminosity. With the addition of the A0620-00 point, the plane relation provides an empirical proof for the scale-invariance of the jet-accretion coupling in accreting black holes over the entire parameter space observable with current instrumentation.

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arXiv2006

Why the fundamental plane of black hole activity is not simply a distance driven artifact

The fundamental plane of black hole activity is a non-linear correlation among radio core luminosity, X-ray luminosity and mass of all accreting black holes, both of stellar mass and supermassive, found by Merloni, Heinz and Di Matteo (2003) and, independently, by Falcke, Koerding and Markoff (2004). Here we further examine a number of statistical issues related to this correlation. In particular, we discuss the issue of sample selection and quantify the bias introduced by the effect of distance in two of the correlated quantities. We demonstrate that the fundamental plane relation cannot be a distance artifact, and that its non-linearity must represent an intrinsic characteristic of accreting black holes. We also discuss possible future observational strategies to improve our understanding of this correlation.

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arXiv2005

Heating the bubbly gas of galaxy clusters with weak shocks and sound waves

Using hydrodynamic simulations and a technique to extract the rotational component of the velocity field, we show how bubbles of relativistic gas inflated by AGN jets in galaxy clusters act as a catalyst, transforming the energy carried by sound and shock waves to heat. The energy is stored in a vortex field around the bubbles which can subsequently be dissipated. The efficiency of this process is set mainly by the fraction of the cluster volume filled by (sub-)kpc scale filaments and bubbles of relativistic plasma.

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arXiv2005

Estimating the kinetic luminosity function of jets from Galactic X-ray binaries

By combining the recently derived X-ray luminosity function for Galactic X-ray binaries (XRBs) by Grimm et al. (2002) and the radio-X-ray-mass relation of accreting black holes found by Merloni et al. (2003), we derive predictions for the radio luminosity function and radio flux distribution (logN/logS) for XRBs. Based on the interpretation that the radio-X-ray-mass relation is an expression of an underlying relation between jet power and nuclear radio luminosity, we derive the kinetic luminosity function for Galactic black hole jets, up to a normalization constant in jet power. We present estimates for this constant on the basis of known ratios of jet power to core flux for AGN jets and available limits for individual XRBs. We find that, if XRB jets do indeed fall on the same radio flux--kinetic power relation as AGN jets, the estimated mean kinetic luminosity of typical low/hard state jets is of the order of ~ 2x10^37 ergs/s, with a total integrated power output of W \~ 5.5x10^38 ergs/s. We find that the power carried in transient jets should be of comparable magnitude to that carried in low/hard state jets. Including neutron star systems increases this estimate to W ~ 9x10^38 ergs/s. We estimate the total kinetic energy output from low/hard state jets over the history of the Galaxy to be E_{XRB} ~ 7x10^56 ergs.

astro-ph↗

arXiv2005

A dark jet dominates the power output of the stellar black hole Cygnus X-1

Accreting black holes are thought to emit the bulk of their power in the X-ray band by releasing the gravitational potential energy of the infalling matter. At the same time, they are capable of producing highly collimated jets of energy and particles flowing out of the system with relativistic velocities. Here we show that the 10 solar mass black hole in the X-ray binary Cygnus X-1 is surrounded by a large-scale (about 5 pc in diameter) ring-like structure that appears to be inflated by the inner radio jet. We estimate that in order to sustain the observed emission of the ring, the jet of Cygnus X-1 has to carry a kinetic power that can be as high as the bolometric X-ray luminosity of the binary system. This result may imply that low-luminosity stellar mass black holes as a whole dissipate the bulk of the liberated accretion power in the form of `dark', radiatively inefficient relativistic outflows, rather than locally in the X-ray emitting inflow.

astro-ph↗

arXiv2004

The Halo, Hot Spots and Jet/Cloud Interaction of PKS 2153--69

We report Chandra X-ray Observatory and 1.4 GHz Australian Long Baseline Array (LBA) observations of the radio galaxy PKS 2153--69 and its environment. The Chandra image reveals a roughly spherical halo of hot gas extending out to 30 kpc around PKS 2153--69. Two depressions in the surface brightness of the X-ray halo correspond to the large scale radio lobes, and interpreting these as cavities inflated with radio plasma we infer a jet power of 4x10^42 erg/s. Both radio lobes contain hot spots that are detected by Chandra. In addition, the southern hot spot is detected in the 1.4 GHz LBA observation, providing the highest linear resolution image of a radio lobe hot spot to date. The northern hot spot was not detected in the LBA observation. The radio to X-ray spectra of the hot spots are consistent with a simple power law emission model. The nucleus has an X-ray spectrum typical of a type 1 active galactic nucleus, and the LBA observation shows a one-sided nuclear jet on 0.1" scales. Approximately 10" northeast of the nucleus, X-ray emission is associated with an extra-nuclear cloud. The X-ray emission from the cloud can be divided into two regions, an unresolved western component associated with a knot of radio emission (in a low resolution map), and a spatially extended eastern component aligned with the pc-scale jet and associated with highly ionized optical line-emitting clouds. The X-ray spectrum of the eastern component is very soft (Gamma > 4.0 for a power law model or kT ~0.22 keV for a thermal plasma). The LBA observation did not detect compact radio emission from the extra-nuclear cloud. (Abstract truncated).

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arXiv2004

Constraints on relativistic beaming from estimators of the unbeamed flux

We review the statistical properties of relativistic Doppler boosting relevant for studies of relativistic jets from compact objects based on radio--X-ray(--mass) correlations, such as that found in black-hole X-ray binaries in the low/hard state, or the ``fundamental plane'' of Merloni, Heinz, & DiMatteo. We show that the presence of only moderate scatter in such relations does not necessarily imply low Lorentz factors of the jets producing the radio emission in the samples under consideration. Applying Doppler beaming statistics to a large sample of XRBs and AGN, we derive a limit on the width of the Lorentz factor distribution of black holes with relativistic jets: If the X-rays are unbeamed (e.g., if they originate in the accretion disk or in the slower, innermost part of the jet), the width of the βΓdistribution should be about one order of magnitude or less. If the scatter about the ``fundamental plane'' is entirely dominated by relativistic beaming, a lower limit on the mean Lorentz factor <βΓ> > 5 can be derived. On the other hand, if the X-rays are boosted by the same factor as the radio emission, we show that the observed scatter cannot be reasonably explained by Doppler boosting alone.

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arXiv2004

Constraints on the role of synchrotron X-rays from jets of accreting black holes

We present an extension of the scale invariance formalism by Heinz & Sunyaev (2003) which includes the effects of radiative cooling on the X-ray synchrotron emission from core dominated jets and outflows. We derive the scaling relations between the radio luminosity L_r, the synchrotron X-ray luminosity L_x, the mass M, and the accretion rate of an accreting black hole. We argue that the inclusion of synchrotron losses into the scaling relations is required by the data used in Merloni, Heinz, & DiMatteo (2003) to define the "fundamental plane'' correlation between L_r, L_x, and M in AGNs and Galactic X-ray binaries. We then fit the new scaling relations to the "fundamental plane" correlation. This allows us to derive statistical constraints on the contribution from jet synchrotron emission to the X-rays from black holes, or, alternatively, on the particle acceleration scheme at work in these jets. We find that, in order for jet synchrotron X-rays to be consistent with the observed "fundamental plane" correlation, the global particle spectrum must be both steep: f(gamma) ~ gamma^(-(3.4 (+0.6-0.5)), and unbroken down to energies well below the radio synchrotron regime. Such a steep particle distribution would imply steeper X-ray spectra than observed in most sources contributing to the correlation with avalailable X-ray spectral index measurements. We suggest that, unless some assumptions of the scale invariance hypothesis are broken, another emission mechanism (likely either disk radiation and/or inverse Compton scattering in the jet) contributes significantly to the X-rays of a sizeable fraction of the sources.

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arXiv2004

Long term variability of Cygnus X-1, III. Radio-X-ray correlations

Long time scale radio-X-ray correlations in black holes during the hard state have been found in many sources and there seems to emerge a universal underlying relationship which quantitatively describes this behavior. Although it would appear only natural to detect short term emission patterns in the X-ray and - with a certain time lag - in the radio, there has been little evidence for this up to now. The most prominent source for radio-X-ray correlations on short time scales (minutes) so far remains GRS 1915+105 where a single mass ejection could be detected successively in the X-ray, IR, and radio wavebands. We analyze a database of more than 4 years of simultaneous radio-X-ray data for Cygnus X-1 from the Ryle Telescope and RXTE PCA/HEXTE. We confirm the existence of a radio-X-ray correlation on long time scales, especially at hard energies. We show that apparent correlations on short time scales in the lightcurves of Cygnus X-1 are most likely the coincidental outcome of white noise statistics. Interpreting this result as a breakdown of radio-X-ray correlations on shorter time scales, this sets a limit to the speed of the jet.

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arXiv2004

Reflections of AGN Outbursts in the Gaseous Atmosphere of M87

We combined deep Chandra, ROSAT HRI, and XMM-Newton observations of M87 to study the impact of AGN outbursts on its gaseous atmosphere. Many X-ray features appear to be a direct result of repetitive AGN outbursts. In particular, the X-ray cavities around the jet and counter jet are likely due to the expansion of radio plasma, while rings of enhanced emission at 14 and 17 kpc are probably shock fronts associated with outbursts that began 1-2\times10^7 years ago. The effects of these shocks are also seen in brightenings within the prominent X-ray arms. On larger scales, ~50 kpc from the nucleus, depressions in the surface brightness may be remnants of earlier outbursts. As suggested for the Perseus cluster (Fabian et al.), our analysis of the energetics of the M87 outbursts argues that shocks may be the most significant channel for AGN energy input into the cooling flow atmospheres of galaxies, groups, and clusters. For M87, the mean power driving the shock outburst, 2.4\times 10^{43} ergs/sec, is three times greater than the radiative losses from the entire ``cooling flow''. Thus, even in the absence of other energy inputs, outbursts every 3\times10^7 years are sufficient to quench the flow.

astro-ph↗

arXiv2003

Ram pressure stripping and the formation of cold fronts

Chandra and XMM-Newton observations of many clusters reveal sharp discontinuities in the surface brightness, which, unlike shocks, have lower gas temperature on the X-ray brighter side of the discontinuity. For that reason these features are called ``cold fronts''. It is believed that some cold fronts are formed when a subcluster merges with another cluster and the ram pressure of gas flowing outside the subcluster gives the contact discontinuity the characteristic curved shape. While some edges may not arise directly from mergers (e.g., A496, Dupke & White, 2003), this paper focuses on those which arise as contact discontinuities between a merging subcluster and the ambient cluster gas. We argue that the flow of gas past the merging subcluster induces slow motions inside the cloud. These motions transport gas from the central parts of the subcluster towards the interface. Since in a typical cluster or group (even an isothermal one) the entropy of the gas in the central regions is significantly lower than in the outer regions, the transport of the low entropy gas towards the interface and the associated adiabatic expansion makes the gas temperature immediately inside the interface lower than in any other place in the system, thus enhancing the temperature jump across the interface and making the ``tip'' of the contact discontinuity cool. We illustrate this picture with the XMM-Newton gas temperature map of the A3667 cluster.

astro-ph↗

arXiv2003

The Non-Linear Dependence of Flux on Black Hole Mass and Accretion Rate in Core Dominated Jets

We derive the non-linear relation between the core flux F_{nu} of accretion powered jets at a given frequency and the mass M of the central compact object. For scale invariant jet models, the mathematical structure of the equations describing the synchrotron emission from jets enables us to cancel out the model dependent complications of jet dynamics, retaining only a simple, model independent algebraic relation between F_{nu} and M. This approach allows us to derive the F_{nu}-M relation for any accretion disk scenario that provides a set of input boundary conditions for the magnetic field and the relativistic particle pressure in the jet, such as standard and advection dominated accretion flow (ADAF) disk solutions. Surprisingly, the mass dependence of F_{nu} is very similar in different accretion scenarios. For typical flat-spectrum core dominated radio jets and standard accretion scenarios we find F_{nu}~M^{17/12}. The 7-9 orders of magnitude difference in black hole mass between microquasars and AGN jets imply that AGN jets must be about 3-4 orders of magnitude more radio loud than microquasars, i.e., the ratio of radio to bolometric luminosity is much smaller in microquasars than in AGN jets. Because of the generality of these results, measurements of this F_{nu}-M dependence are a powerful probe of jet and accretion physics. We show how our analysis can be extended to derive a similar scaling relation between the accretion rate mdot and F_{nu} for different accretion disk models. For radiatively inefficient accretion modes we find that the flat spectrum emission follows F_{nu}~(mdot*M)^{17/12}.

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arXiv2002

Rho^0 meson production in the pp ->pppi+pi- reaction at 3.67 GeV/c

Total and differential cross sections for the exclusive reaction pp->pp rho^0 observed via the pi+pi- decay channel have been measured at beam momentum=3.67 GeV/c. The observed total meson production cross section is determined to be 23.4 +- 0.8 +-8 microb and is significantly lower than typical cross sections used in model calculations for heavy ion collisions. The differential cross sections measured indicate a strong anisotropy cos^2(theta^{CM}) in the rho^0 meson production.

hep-ex↗