arXiv subjects

Laurence P. David

Publications and source records attributed to Laurence P. David.

At least 37 records · Page 2Linked to original sources

arXiv2017

The fraction of cool-core clusters in X-ray vs. SZ samples using Chandra observations

We derive and compare the fractions of cool-core clusters in the {\em Planck} Early Sunyaev-Zel'dovich sample of 164 clusters with $z \leq 0.35$ and in a flux-limited X-ray sample of 100 clusters with $z \leq 0.30$, using {\em Chandra} observations. We use four metrics to identify cool-core clusters: 1) the concentration parameter: the ratio of the integrated emissivity profile within 0.15 $r_{500}$ to that within $r_{500}$, and 2) the ratio of the integrated emissivity profile within 40 kpc to that within 400 kpc, 3) the cuspiness of the gas density profile: the negative of the logarithmic derivative of the gas density with respect to the radius, measured at 0.04 $r_{500}$, and 4) the central gas density, measured at 0.01 $r_{500}$. We find that the sample of X-ray selected clusters, as characterized by each of these metrics, contains a significantly larger fraction of cool-core clusters compared to the sample of SZ selected clusters (44$\pm$7\% vs. 28$\pm$4\% using the concentration parameter in the 0.15--1.0 $r_{500}$ range, 61$\pm$8\% vs. 36$\pm$5\% using the concentration parameter in the 40--400 kpc range, 64$\pm$8\% vs. 38$\pm$5\% using the cuspiness, and 53$\pm$7\% vs. 39$\pm$5\% using the central gas density). Qualitatively, cool-core clusters are more X-ray luminous at fixed mass. Hence, our X-ray flux-limited sample, compared to the approximately mass-limited SZ sample, is over-represented with cool-core clusters. We describe a simple quantitative model that uses the excess luminosity of cool-core clusters compared to non-cool-core clusters at fixed mass to successfully predict the observed fraction of cool-core clusters in X-ray selected samples.

astro-ph.CO↗

arXiv2015

Chandra and XMM-Newton Observations of the Bimodal Planck SZ-detected Cluster PLCKG345.40-39.34 (A3716) with High and Low Entropy Subcluster Cores

We present results from Chandra, XMM-Newton, and ROSAT observations of the Planck SZ-detected cluster A3716 (PLCKG345.40-39.34 - G345). We show that G345 is, in fact, two subclusters separated on the sky by 400 kpc. We measure the subclusters' gas temperatures (~ 2-3 keV), total (~ 1-2 x 10^14 solar masses) and gas (~ 1-2 x 10^13 solar masses) masses, gas mass fraction within r500, entropy profiles, and X-ray luminosities (~ 10^43 erg/s). Using the gas density and temperature profiles for both subclusters, we show that there is good (0.8 sigma) agreement between the expected Sunyaev-Zel'dovich signal predicted from the X-ray data and that measured from the Planck mission, and better agreement within 0.6 sigma when we re-computed the Planck value assuming a two component cluster model, with relative amplitudes fixed based on the X-ray data. Dynamical analysis shows that the two galaxy subclusters are very likely (> 97% probability) gravitationally bound, and in the most likely scenario, the subclusters will undergo core passage in 500 +- 200 Myr. The northern subcluster is centrally peaked and has a low entropy core, while the southern subcluster has a high central entropy. The high central entropy in the southern subcluster can be explained either by the mergers of several groups, as suggested by the presence of five giant ellipticals or by AGN energy injection, as suggested by the presence of a strong radio source in one of its massive elliptical galaxies, or by a combination of both processes.

astro-ph.CO↗

arXiv2014

Molecular Gas in the X-ray Bright Group NGC 5044 as Revealed by ALMA

A short 30 minute ALMA observation of the early-type galaxy NGC 5044, which resides at the center of an X-ray bright group with a moderate cooling flow, has detected 24 molecular structures within the central 2.5 kpc. The masses of the molecular structures vary from 3e5 to 1e7 Mo3 and the CO(2-1) linewidths vary from 15 to 65 km/s. Given the large CO(2-1) linewidths, the observed structures are likely giant molecular associations (GMAs) and not individual molecular clouds (GMCs). Only a few of the GMAs are spatially resolved with the cycle 0 ALMA beam and the average density of these GMAs yields a GMC volume filling factor of about 15%. The observed masses of the resolved GMAs are insufficient for them to be gravitationally bound, however, the most massive GMA does contain a less massive component with a linewidth of 5.5 km/s (typical of an individual virialized GMC). We also show that the GMAs cannot be pressure confined by the hot gas. Given the observed CO(2-1) linewidths of the GMAs (i.e., the velocity dispersion of the embedded GMCs) they will likely disperse on a timescale of about 12 Myr, which is less than the central cooling time of the hot gas, so the embedded GMCs within a GMA must condense out of the hot gas at the same time and arise from local concentrations of thermally unstable parcels of hot gas. There are no indications of any disk-like molecular structures and all indications suggest that the molecular gas follows ballistic trajectories after condensing out of the thermally unstable hot gas. The 230 GHz luminosity of the central continuum source is 500 times greater than its low frequency radio luminosity and probably reflects a recent accretion event by the central supermassive black hole. The spectrum of the central continuum source also exhibits an absorption feature.

astro-ph.GA↗

arXiv2013

A Merger Shock in Abell 2034

We present a $250\,$ks Chandra observation of the cluster merger A2034 with the aim of understanding the nature of a sharp edge previously characterized as a cold front. The new data reveal that the edge is coherent over a larger opening angle and is significantly more bow-shock-shaped than previously thought. Within $\sim 27\,$degrees about the axis of symmetry of the edge the density, temperature and pressure drop abruptly by factors of $1.83^{+0.09}_{-0.08}$, $1.85^{+0.41}_{-0.41}$ and $3.4^{+0.8}_{-0.7}$, respectively. This is inconsistent with the pressure equilibrium expected of a cold front and we conclude that the edge is a shock front. We measure a Mach number $M = 1.59^{+0.06}_{-0.07}$ and corresponding shock velocity $v_{\rm shock}\simeq 2057\,$km/s. Using spectra collected at the MMT with the Hectospec multi-object spectrograph we identify 328 spectroscopically confirmed cluster members. Significantly, we find a local peak in the projected galaxy density associated with a bright cluster galaxy which is located just ahead of the nose of the shock. The data are consistent with a merger viewed within $\sim 23\,$degrees of the plane of the sky. The merging subclusters are now moving apart along a north-south axis approximately $0.3\,$Gyr after a small impact parameter core passage. The gas core of the secondary subcluster, which was driving the shock, appears to have been disrupted by the merger. Without a driving 'piston' we speculate that the shock is dying. Finally, we propose that the diffuse radio emission near the shock is due to the revival of pre-existing radio plasma which has been overrun by the shock.

astro-ph.CO↗

arXiv2013

The impact of sloshing on the intra-group medium and old radio lobe of NGC 5044

We present temperature and abundance maps of the central 125 kpc of the NGC 5044 galaxy group, based an a deep XMM-Newton observation. The abundance map reveals an asymmetrical abundance structure, with the centroid of the highest abundance gas offset ~22 kpc northwest of the galaxy centre, and moderate abundances extending almost twice as far to the southeast than in any other direction. The abundance distribution is closely correlated with two previously-identified cold fronts and an arc--shaped region of surface brightness excess, and it appears that sloshing, induced by a previous tidal encounter, has produced both the abundance and surface brightness features. Sloshing dominates the uplift of heavy elements from the group core on large scales, and we estimate that the southeast extension (the tail of the sloshing spiral) contains at least 1.2x10^5 solar masses more iron than would be expected of gas at its radius. Placing limits on the age of the encounter we find that if, as previously suggested, the disturbed spiral galaxy NGC 5054 was the perturber, it must have been moving supersonically when it transited the group core. We also examine the spectral properties of emission from the old, detached radio lobe southeast of NGC 5044, and find that they are consistent with a purely thermal origin, ruling out this structure as a significant source of spectrally hard inverse-Compton emission.

astro-ph.CO↗

arXiv2013

Hot X-ray coronae around massive spiral galaxies: a unique probe of structure formation models

Luminous X-ray gas coronae in the dark matter halos of massive spiral galaxies are a fundamental prediction of structure formation models, yet only a few such coronae have been detected so far. In this paper, we study the hot X-ray coronae beyond the optical disks of two normal massive spirals, NGC1961 and NGC6753. Based on XMM-Newton X-ray observations, hot gaseous emission is detected to ~60 kpc - well beyond their optical radii. The hot gas has a best-fit temperature of kT~0.6 keV and an abundance of ~0.1 Solar, and exhibits a fairly uniform distribution, suggesting that the quasi-static gas resides in hydrostatic equilibrium in the potential well of the galaxies. The bolometric luminosity of the gas in the (0.05-0.15)r_200 region (r_200 is the virial radius) is ~6e40 erg/s for both galaxies. The baryon mass fractions of NGC1961 and NGC6753 are f_b~0.1, which fall short of the cosmic baryon fraction. The hot coronae around NGC1961 and NGC6753 offer an excellent basis to probe structure formation simulations. To this end, the observations are confronted with the moving mesh code Arepo and the smoothed particle hydrodynamics code Gadget. Although neither model gives a perfect description, the observed luminosities, gas masses, and abundances favor the Arepo code. Moreover, the shape and the normalization of the observed density profiles are better reproduced by Arepo within ~0.5r_200. However, neither model incorporates efficient feedback from supermassive black holes or supernovae, which could alter the simulated properties of the X-ray coronae. With the further advance of numerical models, the present observations will be essential in constraining the feedback effects in structure formation simulations.

astro-ph.CO↗

arXiv2012

The diverse hot gas content and dynamics of optically similar low-mass elliptical galaxies

The presence of hot X-ray emitting gas is ubiquitous in massive early-type galaxies. However, much less is known about the content and physical status of the hot X-ray gas in low-mass ellipticals. In the present paper we study the X-ray gas content of four low-mass elliptical galaxies using archival Chandra X-ray observations. The sample galaxies, NGC821, NGC3379, NGC4278, and NGC4697, have approximately identical K-band luminosities, and hence stellar masses, yet their X-ray appearance is strikingly different. We conclude that the unresolved emission in NGC821 and NGC3379 is built up from a multitude of faint compact objects, such as coronally active binaries and cataclysmic variables. Despite the non-detection of X-ray gas, these galaxies may host low density, and hence low luminosity, X-ray gas components, which undergo a Type Ia supernova (SN Ia) driven outflow. We detect hot X-ray gas with a temperature of kT ~ 0.35 keV in NGC4278, the component of which has a steeper surface brightness distribution than the stellar light. Within the central 50 arcsec (~3.9 kpc) the estimated gas mass is ~3 x 10^7 M_sun, implying a gas mass fraction of ~0.06%. We demonstrate that the X-ray gas exhibits a bipolar morphology in the northeast-southwest direction, indicating that it may be outflowing from the galaxy. The mass and energy budget of the outflow can be maintained by evolved stars and SNe Ia, respectively. The X-ray gas in NGC4697 has an average temperature of kT ~ 0.3 keV, and a significantly broader distribution than the stellar light. The total gas mass within 90 arcsec (~5.1 kpc) is ~2.1 x 10^8 M_sun, hence the gas mass fraction is ~0.4%. Based on the distribution and physical parameters of the X-ray gas, we conclude that it is most likely in hydrostatic equilibrium, although a subsonic outflow may be present.

astro-ph.HE↗

arXiv2012

Recurrent radio outbursts at the center of the NGC1407 galaxy group

We present deep Giant Metrewave Radio Telescope (GMRT) radio observations at 240, 330 and 610 MHz of the complex radio source at the center of the NGC1407 galaxy group. Previous GMRT observations at 240 MHz revealed faint, diffuse emission enclosing the central twin-jet radio galaxy. This has been interpreted as an indication of two possible radio outbursts occurring at different times. Both the inner double and diffuse component are detected in the new GMRT images at high levels of significance. Combining the GMRT observations with archival Very Large Array data at 1.4 and 4.9 GHz, we derive the total spectrum of both components. The inner double has a spectral index α=0.7, typical for active, extended radio galaxies, whereas the spectrum of the large-scale emission is very steep, with α=1.8 between 240 MHz and 1.4 GHz. The radiative age of the large-scale component is very long, ~300 Myr, compared to ~30 Myr estimated for the central double, confirming that the diffuse component was generated during a former cycle of activity of the central galaxy. The current activity have so far released an energy which is nearly one order of magnitude lower than that associated with the former outburst. The group X-ray emission in the Chandra and XMM-Newton images and extended radio emission show a similar swept-back morphology. We speculate that the two structures are both affected by the motion of the group core, perhaps due to the core sloshing in response to a recent encounter with the nearby elliptical galaxy NGC1400.

astro-ph.CO↗

arXiv2012

The Universal Gas Mass Fraction in Clusters of Galaxies

We obtained a deep 150ksec Chandra observation of the optically selected cluster of galaxies, RCS 2318+0034, to investigate the gas mass fraction in this system. Combining our deep {\it Chandra} observation with an archival 50ksec observation, we derive gas mass fractions of fgas=0.06 +- 0.02 and 0.10 +- 0.02 within r2500 and r500, respectively. The gas mass fraction in RCS 2318+0034 within r500 is typical of X-ray selected clusters. Further study shows that the large scale properties of RCS 2318+0034, including the relations between gas mass, X-ray luminosity and gas temperature are also consistent with the observed correlations of X-ray selected clusters. However, the gas mass fraction within r2500 is less than most X-ray selected clusters, as previously reported. The deep Chandra image of RCS 2318+0034 shows that this system is presently undergoing a major merger which may have an impact on the inferred gas mass fraction within r2500.

astro-ph.CO↗

arXiv2011

Heating the hot atmospheres of galaxy groups and clusters with cavities: the relationship between jet power and low-frequency radio emission

We present scaling relations between jet power and radio power measured using the Giant Metrewave Radio Telescope (GMRT), Chandra and XMM-Newton, for a sample of 9 galaxy groups combined with the Birzan et al. sample of clusters. Cavity power is used as a proxy for mechanical jet power. Radio power is measured at 235 MHz and 1.4 GHz, and the integrated 10 MHz-10 GHz radio luminosity is estimated from the GMRT 610-235 MHz spectral index. The use of consistently analysed, high resolution low-frequency radio data from a single observatory makes the radio powers for the groups more reliable than those used by previous studies, and the combined sample covers 6-7 decades in radio power and 5 decades in cavity power. We find a relation of the form Pjet proportional to Lradio^~0.7 for integrated radio luminosity, with a total scatter of sigma_Lrad=0.63 and an intrinsic scatter of sigma_i,Lrad=0.59. A similar relation is found for 235 MHz power, but a slightly flatter relation with greater scatter is found for 1.4 GHz power, suggesting that low-frequency or broad band radio measurements are superior jet power indicators. We find our low-frequency relations to be in good agreement with previous observational results. Comparison with jet models shows reasonable agreement, which may be improved if radio sources have a significant low-energy electron population. We consider possible factors which could bias our results or render them more uncertain, and find that correcting for such factors in those groups we are able to study in detail leads to a flattening of the Pjet:Lradio relation.

astro-ph.CO↗

arXiv2011

A combined low-radio frequency/X-ray study of galaxy groups I. Giant Metrewave Radio Telescope observations at 235 MHz and 610 MHz

We present new Giant Metrewave Radio Telescope observations at 235 MHz and 610 MHz of 18 X-ray bright galaxy groups. These observations are part of an extended project, presented here and in future papers, which combines low-frequency radio and X-ray data to investigate the interaction between central active galactic nuclei (AGN) and the intra-group medium (IGM). The radio images show a very diverse population of group-central radio sources, varying widely in size, power, morphology and spectral index. Comparison of the radio images with Chandra and XMM-Newton X-ray images shows that groups with significant substructure in the X-ray band and marginal radio emission at >= 1 GHz host low-frequency radio structures that correlate with substructures in IGM. Radio-filled X-ray cavities, the most evident form of AGN/IGM interaction in our sample, are found in half of the systems, and are typically associated with small, low- or mid-power double radio sources. Two systems, NGC5044 and NGC4636, possess multiple cavities, which are isotropically distributed around the group center, possibly due to group weather. In other systems the radio/X-ray correlations are less evident. However, the AGN/IGM interaction can manifest itself through the effects of the high-pressure medium on the morphology, spectral properties and evolution of the radio-emitting plasma. In particular, the IGM can confine fading radio lobes in old/dying radio galaxies and prevent them from dissipating quickly. Evidence for radio emission produced by former outbursts that coexist with current activity is found in six groups of the sample.

astro-ph.CO↗

arXiv2011

A Chandra study of the large-scale shock and cool filaments in Hydra A: Evidence for substantial gas dredge-up by the central outburst

We present the results of a Chandra study of the Hydra A galaxy cluster, where a powerful AGN outburst created a large-scale cocoon shock. We investigated possible azimuthal variations in shock strength and shape, finding indications for a weak shock with a Mach number in the range ~1.2-1.3. We measured the temperature change across the shock front. However, the detection of a temperature rise in the regions immediately inside of the front is complicated by the underlying temperature profile of the cluster atmosphere. We measured the global temperature profile of the cluster up to 700 kpc, which represents the farthest measurement obtained with Chandra for this cluster. A "plateau" in the temperature profile in the range ~70-150 kpc indicates the presence of cool gas, which is likely the result of uplift of material by the AGN outburst. After masking the cool filaments visible in the hardness ratio map, the plateau disappears and the temperature profile recovers a typical shape with a peak around 190 kpc, just inside the shock front. However, it is unlikely that such a temperature feature is produced by the shock as it is consistent with the general shape of the temperature profiles observed for relaxed galaxy clusters. We studied the spectral properties of the cool filaments finding evidence that ~10^11 M_sun of low-entropy material has been dredged up by the rising lobes from the central 30 kpc to the observed current position of 75-150 kpc. The energy required to lift the cool gas is >~2.2 x 10^60 erg, which is comparable to the work required to inflate the cavities and is ~25% of the total energy of the large-scale shock. Our results show that the AGN feedback in Hydra A is acting not only by directly heating the gas, but also by removing a substantial amount of potential fuel for the SMBH.

astro-ph.CO↗

arXiv2010

The Dissection of Abell 2744: A Rich Cluster Growing Through Major and Minor Mergers

New Chandra X-ray data and extensive optical spectroscopy, obtained with AAOmega on the 3.9 m Anglo-Australian Telescope, are used to study the complex merger taking place in the galaxy cluster Abell 2744. Combining our spectra with data from the literature provides a catalog of 1237 redshifts for extragalactic objects lying within 15' of the cluster center. From these, we confirm 343 cluster members projected within 3 Mpc of the cluster center. Combining positions and velocities, we identify two major substructures, corresponding to the remnants of two major subclusters. The new data are consistent with a post core passage, major merger taking place along an axis that is tilted well out of the plane of the sky, together with an interloping minor merger. Supporting this interpretation, the new X-ray data reveal enriched, low entropy gas from the core of the approaching, major subcluster, lying ~2' north of the cluster center, and a shock front to the southeast of the previously known bright, compact core associated with the receding subcluster. The X-ray morphology of the compact core is consistent with a Bullet-like cluster viewed from within ~45 degrees of the merger axis. An X-ray peak ~3' northwest of the cluster center, with an associated cold front to the northeast and a trail of low entropy gas to the south, is interpreted as the remnant of an interloping minor merger taking place roughly in the plane of the sky. We infer approximate paths for the three merging components.

astro-ph.CO↗

arXiv2010

AGN Driven Weather and Multiphase Gas in the Core of the NGC 5044 Galaxy Group

A deep Chandra observation of the X-ray bright group, NGC 5044, shows that the central region of this group has been strongly perturbed by repeated AGN outbursts. These recent AGN outbursts have produced many small X-ray cavities, cool filaments and cold fronts. We find a correlation between the coolest X-ray emitting gas and the morphology of the Ha filaments. The Ha filaments are oriented in the direction of the X-ray cavities, suggesting that the warm gas responsible for the Halpha emission originated near the center of NGC 5044 and was dredged up behind the buoyant, AGN-inflated X-ray cavities. A detailed spectroscopic analysis shows that the central region of NGC 5044 contains spatially varying amounts of multiphase gas. The regions with the most inhomogeneous gas temperature distribution tend to correlate with the extended 235 MHz and 610 MHz radio emission detected by the GMRT. This may result from gas entrainment within the radio emitting plasma or mixing of different temperature gas in the regions surrounding the radio emitting plasma by AGN induced turbulence. Accounting for the effects of multiphase gas, we find that the abundance of heavy elements is fairly uniform within the central 100 kpc, with abundances of 60-80% solar for all elements except oxygen, which has a significantly sub-solar abundance. In the absence of continued AGN outbursts, the gas in the center of NGC 5044 should attain a more homogeneous distribution of gas temperature through the dissipation of turbulent kinetic energy and heat conduction in approximately 10e8 yr. The presence of multiphase gas in NGC 5044 indicates that the time between recent AGN outbursts has been less than approximately 10e8 yr.

astro-ph.CO↗

arXiv2010

A deep Chandra observation of the poor cluster AWM4 - II. The role of the radio jets in enriching the intra-cluster medium

We use a Chandra observation of the poor cluster AWM4 to map the temperature and abundance of the intra-cluster medium, so as to examine the influence of the central radio galaxy on its environment. While the cluster core is generally enriched to near-solar abundances, we find evidence of super-solar abundances correlated with the radio jets, extending ~35 kpc from the core of the central dominant galaxy NGC 6051 along its minor axis. We conclude that the enriched gas has been transported out of the central galaxy through the action of the radio source. We estimate the excess mass of iron in the entrained gas to be ~1.4x10^6 Msol, and find that this can be produced in the core of NGC 6051 within the timescale of the AGN outburst. The energy required to transport this gas to its current location is ~4.5x10^57 erg, a significant fraction of the estimated total mechanical energy output of the AGN, though this estimate is dependent on the degree of enrichment of the uplifted gas. The larger near-solar abundance region is also compatible with enrichment by metals mixed outward from NGC 6051 over a much longer timescale.

astro-ph.CO↗

arXiv2010

A deep Chandra observation of the poor cluster AWM 4 - I. Properties of the central radio galaxy and its effects on the intracluster medium

Using observations from the Chandra X-ray Observatory and Giant Metrewave Radio Telescope, we examine the interaction between the intracluster medium and central radio source in the poor cluster AWM 4. In the Chandra observation a small cool core or galactic corona is resolved coincident with the radio core. This corona is capable of fuelling the active nucleus, but must be inefficiently heated by jet interactions or conduction, possibly precluding a feedback relationship between the radio source and cluster. A lack of clearly detected X-ray cavities suggests that the radio lobes are only partially filled by relativistic plasma. We estimate a filling factor of phi=0.21 (3 sigma upper limit phi<0.42) for the better constrained east lobe. We consider the particle population in the jets and lobes, and find that the standard equipartition assumptions predict pressures and ages which agree poorly with X-ray estimates. Including an electron population extending to low Lorentz factors either reduces (gamma_min=100) or removes (gamma_min=10) the pressure imbalance between the lobes and their environment. Pressure balance can also be achieved by entrainment of thermal gas, probably in the first few kiloparsecs of the radio jets. We estimate the mechanical power output of the radio galaxy, and find it to be marginally capable of balancing radiative cooling.

astro-ph.CO↗

arXiv2010

Cavities and shocks in the galaxy group HCG 62 as revealed by Chandra, XMM and GMRT data

We report on the results of an analysis of Chandra, XMM-Newton and new GMRT data of the X-ray bright compact group of galaxies HCG 62, which is one of the few groups known to possess clear, small X-ray cavities in the inner regions. This is part of an ongoing X-ray/low-frequency radio study of 18 groups, initially chosen for the availability of good-quality X-ray data and evidence for AGN/hot gas interaction. At higher frequency (1.4 GHz), the HCG 62 cavity system shows minimal if any radio emission, but the new GMRT observations at 235 MHz and 610 MHz clearly detect extended low-frequency emission from radio lobes corresponding to the cavities. By means of the synergy of X-ray and low-frequency radio observations, we compare and discuss the morphology, luminosity and pressure of the gas and of the radio source. We find that the radio source is radiatively inefficient, with a ratio of radio luminosity to mechanical cavity power of $\sim 10^{-4}$, and that the radio pressure of the lobes is about one order of magnitude lower than the X-ray pressure of the surrounding thermal gas. Thanks to the high spatial resolution of the Chandra surface brightness and temperature profiles, we also identify a shock front located at 36 kpc to the south-west of the group center, close to the southern radio lobe, with a Mach number $\sim 1.5$ and a total power which is about one order of magnitude higher than the cavity power. Such a shock may have heated the gas in the southern region, as indicated by the temperature map. The shock may also explain the arc-like region of enriched gas seen in the iron abundance map, as this may be produced by a non-Maxwellian electron distribution near its front.

astro-ph.CO↗

arXiv2008

The Extended Fe distribution in the intracluster medium and the implications regarding AGN Heating

We present a systematic analysis of XMM-Newton observations of 8 cool-core clusters of galaxies and determine the Fe distribution in the intracluster medium relative to the stellar distribution in the central dominant galaxy (CDG). Our analysis shows that the Fe is significantly more extended than the stellar mass in the CDG in all of the clusters in our sample, with a slight trend of increasing extent with increasing central cooling time. The excess Fe within the central 100 kpc in these clusters can be produced by Type Ia supernovae from the CDG over the past 3-7 Gyr. Since the excess Fe primarily originates from the CDG, it is a useful probe for determining the motion of the gas and the mechanical energy deposited by AGN outbursts over the past $\sim$ 5 Gyr in the centers of clusters. We explore two possible mechanisms for producing the greater extent of the Fe relative to the stars in the CDG, including: bulk expansion of the gas and turbulent diffusion of Fe. Assuming the gas and Fe expand together, we find that a total energy of $10^{60} - 10^{61}$~erg~s$^{-1}$ must have been deposited into the central 100 kpc of these clusters to produce the presently observed Fe distributions. Since the required enrichment time for the excess Fe is approximately 5 Gyr in these clusters, this gives an average AGN mechanical power over this time of $10^{43} - 10^{44}$~erg~s$^{-1}$. The extended Fe distribution in cluster cores can also arise from turbulent diffusion. Assuming steady-state (i.e., the outward mass flux of Fe across a given surface is equal to the mass injection rate of Fe within that surface) we find that diffusion coefficients of $10^{29} - 10^{30}$ cm$^2$~s$^{-1}$ are required to maintain the presently observed Fe profiles (abridged).

astro-ph↗