DeepChandraobservation of the galaxy cluster WARPJ1415.1+3612 atz=1

Abstract

Aims. Using the deepest (370 ks) Chandra observation of a high-redshift galaxy cluster, we perform a detailed characterization of the intra-cluster medium (ICM) of WARPJ1415.1+3612 at z = 1.03, particularly its core region. We also explore the connection between the ICM core properties and the radio/optical properties of the brightest cluster galaxy (BCG). Methods. We perform a spatially resolved analysis of the ICM to obtain temperature, metallicity and surface brightness profiles over the 8-400 kpc radial range. We measure the following cool-core diagnostics: central temperature drop, central metallicity excess, central cooling time, and central entropy. Using the deprojected temperature and density profiles, we accurately derive the cluster hydrostatic mass at different overdensities. In addition to the X-ray data, we use archival radio VLA imaging and optical GMOS spectroscopy of the central galaxy to investigate the feedback between the central galaxy and the ICM. Results. Our spatially resolved spectral analysis shows a significant temperature drop from a maximum of 8.0 keV to a projected core value T c = 4.6 ± 0.4 keV, and a remarkably high central iron abundance peak, Z Fe,c = 3.60 +1.50 −0.85 Z , measured within a radius of 12 kpc. We measure M 500 = M(r < R 500 ) = 2.4 ± 0.4 M and a corresponding gas fraction f gas = 0.10 ± 0.02. The central cooling time is shorter than 0.1 Gyr and the entropy K c is equal to 9.9 keV cm 2 . We detect a strong [OII] emission line in the optical spectra of the BCG with an equivalent width of -25 Å, for which we derive a star formation rate within the range 2-8 M yr −1 . The VLA data reveals a central radio source coincident with the BCG with a luminosity L 1.4 GHz = 2.0 × 10 25 W Hz −1 , and a faint one-sided jet-like feature with an extent of ∼80 kpc. We do not find clear evidence for cavities associated to the radio AGN activity. Conclusions. Our analysis shows that WARPJ1415 has a well developed cool-core with ICM properties similar to those found in the local Universe. Its properties and the clear sign of feedback activity found in the central galaxy in the optical and radio bands, show that feedback processes are already established at z ∼ 1 (a lookback time of 7.8 Gyr). In addition, the presence of a strong metallicity peak shows that the central regions have been promptly enriched by star formation processes in the central galaxy already at z > 1. Our results significantly constrain the timescale for the formation and self-stabilization of cool-cores.

IDCS J1426.5+3508: THE MOST MASSIVE GALAXY CLUSTER AT z > 1.5

“…As Figure 2 illustrates, there is no obvious detection of the Fe Kα emission line, such that, within r 2500 , these data are consistent with anywhere from "typical" to a complete absence of metals. Over larger radii we may be observing a marked lack of metals, with the typical average metallicity of low-redshift clusters being Z 500 ∼0.3±0.1 Z e (De Grandi & Molendi 2001), a level of enrichment also seen in some z>1 clusters (Rosati et al 2009;Santos et al 2012;De Grandi et al 2014). However, deeper Upper panel: X-ray surface brightness profile for IDCSJ1426.5 +3508, derived using the large-scale X-ray centroid as the center.…”

“…Indeed, Vikhlinin et al (2007) found no such systems at z>0.5 in their 400 deg 2 survey. Two similar systems, albeit at much lower redshift (z ∼ 1.1), have been identified-one by McDonald et al (2013) in a sample of 83 SPT clusters and one by Santos et al (2012) in the WARPS survey.…”

High-Redshift Cool-Core Galaxy Clusters Detected via the Sunyaev-Zel'dovich Effect in the South Pole Telescope Survey

“…The other half is comprised of clusters in the CCCP high-z set (V09) with z 0.5 (20 clusters) 34 et al 1998) and the WARPS 36 (Horner et al 2008) samples that have Chandra observations (15 Clusters). One of these clusters, WARP J1415.1+3612, has an updated c SB in Santos et al (2012). Due to the low number of counts and similar selection properties in the RDCS and WARPS surveys, Santos et al (2010) group them together in their analysis as RDCS+WARPS.…”

The dynamics ofz~ 1 clusters of galaxies from the GCLASS survey

“…The compilation of Sereno & Covone (2013) includes all known z > 0.8 clusters for which M(r) has been derived so far, except for "El Gordo", whose mass profile has been determined via gravitational lensing by Jee et al (2014). The mass profiles of some clusters in the compilation of Sereno & Covone (2013) have been determined in more than one study, generally by gravitational lensing techniques (Clowe et al 2000;Jee et al 2005aJee et al ,b, 2006Lombardi et al 2005;Jee & Tyson 2009), and in some cases by using hydrostatic equilibrium equations based on X-ray data (Huo et al 2004;Santos et al 2012) and/or the thermal Sunyaev-Zel'dovich effect (Adam et al 2015). In none of these studies have β(r), Q(r), or Q r (r) been determined.…”