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Proposal Number: 09800046

Title: Chandra Observations of SZ-selected Galaxy Clusters Detected by the South Pole Telescope

PI Name: Gordon Garmire

We propose a 200 ks program to for Chandra follow-up of some of the first massive galaxy clusters detected in the forthcoming South Pole Telescope (SPT) cluster survey. Our program (in conjunction with companion GTO observations by the HRC team) will provide a pathfinder for future much larger investments of Chandra time to follow-up the 200 most massive clusters detected in the SPT survey. This larger program will provide significant constraints on dark energy in its own right, and will greatly amplify the the cosmological power and reliability of the SPT survey.

Proposal Number: 09800120

Title: South Pole Telescope (SPT) - Chandra Cluster Cosmology

PI Name: Stephen Murray

We propose Chandra ACIS-I observations of a mass limited set of clusters detected by the South Pole Telescope using the redshift-independent Sunyaev-Zeldovich effect (SZE). This exploration will find the first clusters detected through their SZE signature on the cosmic microwave background. Ultimately, we expect to observe a sample of 200 clusters at z>0.5 with masses greater than 3x10^14 Msun. We will measure gas temperatures to an accuracy of better than 15% and gas masses to an accuracy of 8%. We will 1) combine the X-ray and SZE data to test d(z) 2) use the X-ray Y parameter (Y=M_gas * T_gas) to derive the cluster mass function which is a sensitive probe of cosmological parameters and 3) improve the reliability of cluster mass estimates using the X-ray mass proxies.

Proposal Number: 09800154

Title: Characterisation of the most distant cluster of galaxies, JKCS041 at z=1.91

PI Name: Stefano Andreon

The number of high-redshift galaxy clusters is scarce, with only few systems known at z>1 and the highest cluster scoring z=1.45. We propose a 80 ks Chandra observation in order to characterise the most distant X-ray detected cluster of galaxies known thus far, JKCS041, at z=1.9, recently discovered by us and for which we have extensive imaging (radio, optical, near-infrared, mid-infrared, UV) data already in hand and spectroscopy in progress. These observations will ensure the first measure of X-ray properties of clusters at this distance and significantly enlarge the redshift baseline of the scaling relations.

Proposal Number: 09800310

Title: Probing Dark Energy with Relaxed Galaxy Clusters

PI Name: Steven Allen

We seek to constrain dark energy using studies of the apparent evolution of the X-ray gas mass fraction in the most X-ray luminous, dynamically relaxed galaxy clusters. The proposed observations will improve the detection of the effects of dark energy from the X-ray data alone to > 5 sigma. More importantly, they will allow us to measure the level of intrinsic (systematic) scatter in distance measurements from this technique and establish whether this is smaller than from type Ia supernovae measurements. Used in combination with supernovae and CMB data, the new Chandra observations will allow the most precise search to date for evolution in the dark energy equation of state - our best approach in trying to understand the origin of cosmic acceleration.

Proposal Number: 09800313

Title: Bubble heating in Extreme Cooling Clusters

PI Name: Steven Allen

Our proposal targets `extreme cooling' clusters: those systems with the largest, fastest cooling rates that most severely challenge the AGN-heating paradigm for cluster cores. By targeting two X-ray bright `extreme cooling cluters' with the clearest radio bubbles in their cores, we seek to establish whether it is possible for AGN heating to balance cooling in such systems. If cooling is not balanced by some heat source, then large residual cooling rates should be detectable in the spectral X-ray data. We will measure the bubble properties precisely and map the spatial-spectral structure of the surrounding X-ray gas, searching for ghost bubbles, shocks, ripples, fronts and non-thermal emission.

Proposal Number: 09800349

Title: SCALING RELATIONS FOR LOW-MASS GALAXY CLUSTERS AND GROUPS

PI Name: Alexey Vikhlinin

Detailed measurements of the cluster scaling relations (e.g., L-T) require 1) large, objectively selected, statistically complete samples, and 2) observations that cover a large fraction of the system's virial radius. Such data are now available in the Chandra archive for a large number of high-M clusters, but not for the systems with T ~ 2 keV and below. We propose to fill this gap by observing a sample of 22 low-L objects from a new, sensitive X-ray survey. These observations will quadruple the statistics for low-T clusters and extend the reliable determination

Proposal Number: 09800363

Title: The X-ray Luminous Cluster underlying the Radio-Quiet Quasar H1821+643

PI Name: Andrew Fabian

We propose to make a direct imaging study of the only low redshift galaxy cluster to contain a highly luminous quasar, H1821+643. Existing Chandra observations of the X-ray bright cluster are only noisy snapshots, having been performed using gratings, which much reduce the effective area, do not decrease the background, and produce diffraction spikes. Even these observations strongly hint at an interaction between the jets and outflows of the quasar on its surroundings, in terms of rings of brighter emission possibly indicating shocks. In addition the northern FRI lobe of the quasar also appears to be detected in emission. We expect to learn much about cluster-quasar interaction from this unique object.

Proposal Number: 09800379

Title: The Filamentary Structure of the Hot Gas in the NGC5044 Group

PI Name: Laurence David

An early 20~ksec Chandra observation of the X-ray bright NGC 5044 group revealed an extensive system of cool X-ray filaments and cavities in the central region of the group. The similarity of these structures with those observed in other cooling flows suggests that they were produced AGN outbursts. We recently obtained GMRT data on NGC 5044 and detected 40 mJ of unresolved emission. NGC 5044 has also been extensively observed in the optical and IR (including a recent Spitzer observation). There is a strong spatial correlation between the $H_{\alpha}$ filaments, dust, and cool x-ray filaments in NGC 5044. We propose a 80~ksec Chandra observation of NGC5044 to determine the relationships between the radio emitting plasma, molecular gas, ionized gas, dust, and x-ray emitting gas.

Proposal Number: 09800437

Title: The Link between optical nebulae and feedback in cluster cores

PI Name: Roderick Johnstone

The presence of luminous optical emission-line nebulae in brightest cluster galaxies is a dramatic marker for the presence of feedback or heating from the central active nucleus to the intracluster medium. Here we propose ACIS-S observations of the five brightest REFLEX clusters selected to have the most luminous optical emission-line nebulae. We shall confirm the link between emission-line gas and feedback and search for clues to the details of the heating mechanism by correlating the spatial distribution of feedback power with other cluster properties, for example, radio power or merger activity.

Proposal Number: 09800484

Title: The Active Galaxy Population in a Supercluster at z = 0.7

PI Name: Lori Lubin

We propose to use Chandra and the VLA to map the active galaxy population in a supercluster at z = 0.7. The structure contains seven massive clusters and covers a 11 Mpc x 22 Mpc region. Combined with our extensive supporting data, the Chandra and VLA observations will allow us to measure the properties of X-ray and radio sources over a wide range of local densities, study AGN/starburst host galaxies to determine what causes gas-fueling events, and quantify the effect of large scale structure on the nuclear activity and gas content of galaxies. The proposed observations will be used to constrain how large-scale processes influence galaxy-scale events and are a natural continuation of our approved Cycle 7 & 8 programs to study superclusters and dynamically-active systems at high redshift.

Proposal Number: 09800576

Title: Chandra/HST Coverage of Compact Galaxy Group Evolution

PI Name: Sarah Gallagher

The first galaxies and their environments differed substantially from those locally, with multiple interactions influencing their histories. Compared to all other nearby environments, present-day compact galaxy groups most closely reproduce conditions in the earlier universe (z~4) when galaxies assembled through hierarchical formation, and galaxy groups combined to form proto-clusters (in dense regions) or massive ellipticals (in the field). We propose senstitive Chandra observations of two nearby compact galaxy groups, HCGs 31 and 59, to complete a sample of six with joint Chandra/HST coverage. In addition to Spitzer mid-IR and Swift UV imaging already in hand, these data will enable a penetrating multiwavelength investigation into this important environment.

Proposal Number: 09800652

Title: The cluster around the powerful radio-loud quasar 3C186 at z=1.1

PI Name: Aneta Siemiginowska

We request a 200~ksec deep Chandra ACIS-S observation of the high redshift, z=1.1 X-ray cluster associated with the radio-loud quasar 3C~186. We will detect the X-ray cluster emission up to ~0.5~Mpc away from the quasar, study its morphology, and look for an excess temperature as a signature of interaction or a merging process in this high redshift cluster. This cluster is associated with a powerful young quasar (L_bol ~ 10^47 erg/sec) and it gives us a rare opportunity to study an early phase of the interaction between a quasar and its surrounding intracluster medium.

Proposal Number: 09800732

Title: LoCuSS: Cluster Mass Comparison with Chandra and HST -- Observational Discrepancy or Agreement in the New Millennium?

PI Name: Graham Smith

We propose ACIS-I observations of 15 (Lx>1E44erg/s) galaxy clusters at z=0.2 that we have recently imaged with HST. With existing data on 11 clusters, these new data will form a unique high quality Chandra/HST dataset because the sample of 26 is completely unbiased with respect to their X-ray properties. Within the Local Cluster Substructure Survey (LoCuSS) we propose to use these data to characterise the systematic uncertainties in X-ray and lensing mass measurements within cluster cores - essential ground-work for cluster cosmology experiments which rely on precise cluster mass measurements. We will use mock cluster observations based on the Millennium Simulations to calibrate our observational measurements and new constraints on cluster physics to further improve the simulations.

Proposal Number: 09800842

Title: AWM 4: a sharp look at the core of a poor cluster stirred by AGN activity

PI Name: JAN VRTILEK

The central regions of galaxy clusters, frequently occupied by massive elliptical galaxies with strong radio sources interacting with dense, X-ray emitting gas, are among the most interesting and physically active regions in the Universe. We here propose a deep observation of AWM 4, a poor cluster of relaxed appearance without a cooling core but with strong evidence of AGN-driven heating and gas mixing. In this unusual object we will examine the interaction between cluster gas and radio source at high resolution, measure the properties of the gas and constrain the energy budget of the radio source, and clarify the nature of the observed abundance irregularities.

Proposal Number: 09800847

Title: BOW SHOCK, ELECTRON-ION EQUILIBRIUM, BREAKUP OF COOL CORE, AND DARK SUBCLUSTER IN ABELL 520

PI Name: Maxim Markevitch

Shock fronts provide a unique tool to study the cluster plasma. Only two have been found, those in 1E0657 and A520. Using a long observation of 1E0657, we have determined, for the first time in any astrophysical plasma, that electron-proton equilibration time is shorter than Coulomb - a tantalizing result but based on one object. A520 gives the only chance to confirm it. Its shock also coincides with an edge of the radio halo, enabling tests of the origin of the intracluster relativistic electrons. A520 also exhibits a remnant of a cool core broken up by merger-induced instabilities, providing data on plasma viscosity. Finally, weak lensing map of A520 reveals an intriguing dark subcluster almost devoid of galaxies. We propose a long observation of this exceptionally interesting cluster.

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