A High-Resolution Study of the Hydra A Cluster with Chandra: Comparison of the Core Mass Distribution with Theoretical Predictions and Evidence for Feedback in the Cooling Flow

By L. David, P. Nulsen, B. McNamara, W. Forman, C. Jones, Trevor J. Ponman, Brant Robertson, M. Wise. 2000

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The cooling flow cluster Hydra A was observed during the orbital activation and calibration phase of the Chandra Observatory. While the X-ray image of the cluster exhibits complex structure in the central region as reported in McNamara et al., the large-scale X-ray morphology of the cluster is fairly smooth. A spectroscopic analysis of the ACIS data shows that the gas temperature in Hydra A increases outward, reaches a maximum temperature of 4 keV at 200 kpc, and then decreases slightly at larger radii. The distribution of heavy elements is nonuniform, with a factor of 2 increase in the Fe and Si abundances within the central 100 kpc. Beyond the central 100 kpc the Si-to-Fe abundance ratio is twice solar, while the Si-to-Fe ratio of the central excess is consistent with the solar value. One of the more surprising results is the lack of spectroscopic evidence for multiphase gas within the bulk of the cooling flow. Beyond the central 30 kpc, the ACIS spectra are adequately fitted with a single-temperature model. The addition of a cooling flow component does not significantly improve the fit. Only within the central 30 kpc (where the cooling time is less than 1 Gyr) is there spectroscopic evidence for multiphase gas. However, the spectroscopic mass deposition rate is more than a factor of 10 less than the morphologically derived mass accretion rate at 30 kpc. We propose that the cooling flow region is convectively unstable owing to heating by the central radio source, which significantly reduces the net accretion rate. In addition, we show that the mass distribution within the central 30-200 kpc region scales as ρd ∝ r-1.3, intermediate between an NFW and a Moore profile, but with a best-fit NFW concentration parameter (cNFW = 12) approximately 3 times greater than that found in numerical simulations. However, given the limited photon statistics, we cannot rule out the presence of a flat-density core with a core radius less than 30 kpc.

Subfields: Astronomy and Astrophysics

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The structural and scaling properties of nearby galaxy clusters. I. The universal mass profile (2005, background): “…is slowly accumulating that CDM numerical simulations predict the correct shape of the Dark Matter distribution, not only in massive cluster (e.g. David et al. 2001; Allen et al. 2001; Arabadjis et al. 200 ; Buote & Lewis 2004; Buote 2004; Allen et al. 2003), but also in low mass clusters (Pratt…”
Models of Galaxy Clusters with Thermal Conduction (2002, background): “The observations place an upper limit on the mass accretion rate in a few clusters of about 10%–20% of the nominal value needed to explain the observed X-ray flux (e.g., David et al. 2001; Schmidt, Allen, & Fabian 2001; Johnstone et al. 2002).”
Thermal Conduction in Clusters of Galaxies (2001, background): “The mass deposition rate is estimated to be as much as several hundred M⊙ yr −1 in some clusters (e.g., David et al. 2001; Allen et al. 2001).”
X-ray spectroscopy of galaxy clusters: studying astrophysical processes in the largest celestial laboratories (2009, background): “…high angular resolutionChandra images showed signs of strong interaction of the central AGN with the ambient ICM in many cool core regions (e.g. David et al. 2001; Nulsen et al. 2002; Fabian et al. 2005), the most probable solution to the absence of strong cooling was soon believed to be the…”
Reflections of Active Galactic Nucleus Outbursts in the Gaseous Atmosphere of M87 (2003, background): “…from galaxies with very modest gaseous atmospheres, such as Cen A (Kraft et al. 2003) and M84 (Finoguenov & Jones 2001), to those with rich luminous clusters, including Hydra A (McNamara et al. 2000; David et al. 2001; Nulsen et al. 2002) and Perseus (Böhringer et al. 1993; Fabian et al. 2002).”
Chandra Observations of A2029: The Dark Matter Profile Down to below 0.01rvir in an Unusually Relaxed Cluster (2002, background): “…groups have now obtained X-ray constraints on the DM profiles of clusters of galaxies, which are apparently consistent with the CDM paradigm (e.g., David et al. 2001; Pratt & Arnaud 2002; Ettori et al. 2002b; Schmidt, Allen, & Fabian 2001; Allen, Schmidt, & Fabian 2001; Matsushita et al. 2002;…”
The hydrodynamics of dead radio galaxies (2002, background): “Heating models based upon simple hydrodynamic shocks (such as presented in this work or that of David et al. 2001) do not possess such temperature dependent targeting.”
X-Ray Emission from the Hot Interstellar Medium and Southwest Radio Lobe of the Nearby Radio Galaxy Centaurus A (2003, background): “Since the launch of Chandra, many additional examples of the interactions between the ICM and the jets of radio galaxies have been detected (Churazov et al. 2001; Finoguenov & Jones 2001; McNamara et al. 2000; David et al. 2001; Fabian et al. 2000; Blanton et al. 2001b).”
Buoyant radio lobes in a viscous intracluster medium (2004, background): “…may be responsible for the temperature floor; however, such a scenario only postpones rather than prevents radiative cooling, and is hard to reconcile with the strong metallicity gradients observed in the cores of some clusters (David et al. 2001, Matsushita et al. 2002; Sanders & Fabian 2002).”
Cold molecular gas in cooling flow clusters of galaxies (2003, background): “It seems that the radio source and jets could heat the gas with shocks and significantly decrease the cooling rates (David et al. 2001; Brüggen et al. 2002).”
The Birmingham-CfA cluster scaling Project – I. Gas fraction and the M-Tx relation (2003, methodology): “At the same time, ASCA temperatures in the regions immediately adjacent to the central bins in the cooling flow clusters appear to be systematically too high, although within their uncertainties (e.g. David et al. 2001; Arnaud et al. 2001; De Grandi & Molendi 2002).”
X-ray Spectroscopy of Cooling Clusters (2005, background): “…obtained at high spectral resolution have been augmented with further studies at low resolution that attempt to study the spatial distribution in greater detail (David et al. 2001; Böhringer et al. 2001; Molendi & Pizzolato 2001; Schmidt et al. 2001; Ettori et al. 2002; Johnstone et al. 2001).”
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Heating cooling flows with jets (2003, background): “The background that is disturbed by the jets is based on Chandra observations of the Hydra cluster by David et al. (2001).”
Heating Hot Atmospheres with Active Galactic Nuclei (2007, background): “For weak shocks, the entropy jump per unit mass, ∆S, is proportional to the cube of the shock strength (e.g., Landau & Lifshitz 1987; David et al. 2001; measured here by the fractional pressure increase, δp/p, where p is the preshock pressure and δp is the pressure increase across the shock).”
The Coevolution of Galaxies and Supermassive Black Holes: Insights from Surveys of the Contemporary Universe (2014, background): “In reality, however, observations show that the gas temperatures in the cluster cores are at most a factor 3 below the value at large radii, and the amount of cooling gas is only about 10% of the cooling flow prediction (e.g. Peterson et al. 2001, 2003, David et al. 2001, Tamura et al. 2001).”