Chandra's First Decade of Discovery

Session 8: Galaxy Clusters - Feedback, Galaxy Surveys, and Current & Future Missions

AGN Feedback in Clusters of Galaxies

Elizabeth Blanton, Boston University

Observations during the last ten years with Chandra have shed much light on the cooling gas in the centers of clusters of galaxies and the role of AGN heating. Cooling of the hot intracluster medium in cluster centers can feed the supermassive black holes found in the cores of the dominant cluster galaxies leading to AGN outbursts which can reheat the gas, stopping cooling and large amounts of star formation. AGN heating can come in the form of shocks, buoyantly rising bubbles that have been inflated by radio lobes, and sound wave propogation. I will review the great progress in this field that has been enabled by the study of Chandra data over the last decade.

[PDF of this talk] [Video of this talk]

AGN feedback in galaxy groups: The case of HCG 62

Myriam Gitti, SAO-CfA
E. O'Sullivan (SAO-CfA, Birmingham Univ.), S. Giacintucci (SAO-CfA), L. David (SAO-CfA), J. Vrtilek (SAO-CfA), S. Raychaudhury (Birmingham Univ.), C. Jones(SAO-CfA), W. Forman(SAO-CfA)

As a part of an ongoing study of 18 groups of galaxies showing evidence for AGN/hot gas interaction, we report on the results of an analysis of Chandra, XMM and GMRT data of the X-ray bright compact group HCG 62. This is one of the few groups known to possess very clear, small X-ray cavities in the inner regions. The ~50 ks Chandra image combined with the new ~100 ks XMM exposure of HCG 62 allow us to derive with unprecedented accuracy the radial profiles and 2-D distribution of temperature, density and metal abundances. At higher frequency (1.4 GHz or above) the cavities show minimal if any radio emission, but the radio is clearly detected in the cavities with the new GMRT data at lower frequency (610 MHz and below). 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 cavities are close to pressure balance, and that the jets have a “light” hadronic content. Thanks to the high spatial resolution of the Chandra surface brightness and temperature profiles, we also identify a shock front located around 35 kpc to the south-west of the group center, with a Mach number ~1.45 and Eshock ~ 3 x Ecavities. Such a shock may have significantly heated the gas close to the southern cavity, as indicated by the temperature map.

[PDF of this talk] [Video of this talk]

A detailed analysis of the cores of HIFLUGCS galaxy clusters: ICM cooling and AGN heating

Rupal Mittal, AIfA (Bonn) / RIT (Rochester)
Thomas Reiprich (AIfA), Paul Nulsen (CfA), Craig Sarazin (U. Virginia), Heinz Andernach (AIfA), Tracy Clarke (NRL), Daniel Hudson (AIfA)

The physics regulating the dense gas at the centers of galaxy clusters is far from being fully understood. Moreover, no comprehensive and systematic census of observed, detailed, properties of cluster cores exists up to now. We aim to put the statistical description of cluster centers on a firm new footing in order to: (1) gain insight into the physical processes governing cluster cores and (2) identify the best parameter for characterizing cool-core clusters and quantify its relation to other parameters. We summarize 16 widely used as well as new cool-core diagnostics and apply them to the largest complete and well-controlled cluster sample with available high quality data (HIghest X-ray FLUx Galaxy Cluster Sample, >4.5 Ms of cleaned Chandra data). We show that the cooling flow discrepancy is very unlikely due to the recent formation of cooling flows, hence demonstrating the need for a heating mechanism. Based on >140 radio flux-density measurements for the entire HIFLUGCS sample, we provide statistical and quantitative evidence supporting the AGN heating scenario. Lastly, we show that both ICM cooling as well as AGN heating are likely to influence the L-T relation but on different scales.

[PDF of this talk] [Video of this talk]

The Chandra ACIS Survey of M33 (ChASeM33): A Chandra Legacy Program

Ralph Tuellmann, Harvard-Smithsoninan Center for Astrophysics
Terrance J. Gaetz (CfA), Paul P. Plucinsky (CfA), Knox S. Long (STSci), William P. Blair (JHU), P. Frank Winkler (Middlebury College), Benjamin Williams (University of Washington), Kip Kuntz (JHU/GSFC), David Helfand (Columbia University), John P. Hughes (Rutgers University), and the ChASeM33 team

ChASeM33, the Chandra ACIS Survey of M33, with a total exposure time of 1.4Ms and a limiting sensitivity of ~2e34erg/s, covers about 70% of the D25 isophote and is the deepest, high angular resolution X-ray survey of the nearest face-on spiral galaxy to date. More than 650 X-ray sources were detected whose positions, nature, and source statistics are reported in the final ChASeM33 source catalog. Among these sources are more than 60 X-ray counterparts to previously identified SNRs, which means that we have more than doubled the number of known X-ray SNRs in M33. In at least two cases the X-ray spectrum seems to be dominated by ejecta from core collapse SNe.We also report the first detections of two eclipsing high-mass X-ray binaries and seven new transient sources in M33. In one of the X-ray binaries, M33 X-7, the compact object seems to be a black hole with a mass >9Msolar. Besides the point source population, extended sources such as the two most luminous giant HII regions, NGC604 and IC131, are also studied.NGC604 shows the typical soft X-ray spectrum expected from such regions, whereas IC131 appears to be extremely different as it contains a diffuse emission region (~200 pc across) with a hard X-ray spectrum. This spectrum is difficult to explain in the context of the standard wind-blown bubble models. Even if some of the emission is non-thermal, it is not clear what mechanism can produce non-thermal X-rays on such large scales.Moreover, results from the ChASeM33 source catalog are used to explore the large-scale distribution of the purely diffuse X-ray emission in M33. Even with these numerous applications the potential of ChASeM33 is far from being exhausted. This survey will be relevant for future M33 studies and certainly form an important part of Chandra's legacy.

[PDF of this talk] [Video of this talk]

Ten Years XMM-Newton: Scientific Achievements and Future Prospects

Norbert Schartel, XMM-Newton SOC, ESA

XMM-Newton will celebrate its 10th anniversary in December 2009. With about 300 refereed papers published each year, XMM-Newton is one of the most successful scientific missions of ESA ever. The talk gives an overview of the scientific highlights and achievements covering all astrophysical areas from charge exchange found in nearby comets up to the most distant clusters of galaxies. Many XMM-Newton observations address directly cosmological questions like WHIM and dark matter. Several exciting scientific perspectives for the mission's future will be discussed as well.

[PDF of this talk] [Video of this talk]

The International X-ray Observatory

Randall Smith, Harvard-Smithsonian Center for Astrophysics
for the IXO team

The International X-ray Observatory (IXO), a joint ESA-JAXA-NASA effort, will address fundamental and timely questions in astrophysics: What happens close to a black hole? How did supermassive black holes grow? How does large scale structure form? What is the connection between these processes? To address these questions IXO will trace orbits close to the event horizon of black holes, measure black hole spin for several hundred active galactic nuclei (AGN), use spectroscopy to characterize outflows and the environment of AGN during their peak activity, search for super-massive black holes out to redshift z = 10, map bulk motions and turbulence in galaxy clusters, find the missing baryons in the cosmic web using background quasars, and observe the process of cosmic feedback where black holes inject energy on galactic and intergalactic scales. IXO will employ optics with 3 sq m collecting area and 5 arc sec angular resolution - 20 times more collecting area at 1 keV than any previous X-ray observatory. Focal plane instruments will deliver a 100-fold increase in effective area for high-resolution spectroscopy, deep spectral imaging over a wide field of view, deep polarimetric sensitivity, microsecond spectroscopic timing, and high count rate capability. The mission is being planned for launch in 2021 to an L2 orbit, with a five-year lifetime and consumables for 10 years. Previous experience assures us that unexpected discoveries will abound - a key feature of great observatories.

[PDF of this talk] [Video of this talk]

NuSTAR: The Nuclear Spectroscopic Telescope Array

Daniel Stern, JPL/Caltech
Fiona Harrison (Caltech), and the NuSTAR Team

NuSTAR, the Nuclear Spectroscopic Telescope Array, is a recently confirmed Small Explorer (SMEX) NASA mission, scheduled for launch in August 2011. NuSTAR will be the high energy NASA mission, and will probe the X-ray sky approximately two orders of magnitude more sensitively than currently achievable. By focusing X-rays from 6 to 79 keV, NuSTAR will answer fundamental questions about the Universe: How are black holes distributed through the cosmos? How were the elements that compose our bodies and the Earth forged in the explosions of massive stars? What powers the most extreme active galaxies? I will discuss the current status of NuSTAR and the baseline, 2-year science program.

[PDF of this talk] [Video of this talk]