Symposium Proceedings

Normal Galaxies: Diffuse Emission

Chemical Enrichment of the Complex Hot ISM of the Antennae Galaxies

Alessandro Baldi, John Raymond, Giuseppina Fabbiano, Andreas Zezas (SAO), Francois Schweizer (Carnegie Observatories), Andrew King (Theoretical Astrophysics Group, Univ. of Leicester), Trevor Ponman (School of Physics & Astronomy, Univ. of Birmingham), Arnold Rots (SAO)

We present an analysis of the properties of the hot ISM in the merging pair of galaxies known as The Antennae (NGC 4038/39), performed using the deep, coadded 411 ks Chandra ACIS-S data set. These deep X-ray observations and Chandra's high angular resolution allow us to investigate the properties of the hot ISM with unprecedented spatial and spectral resolution. Through a spatially resolved spectral analysis, we find a variety of temperatures (from 0.2 to 0.7 keV) and $N_H$ (from Galactic to $2x10^{21}$ cm$^{-2}$). Metal abundances for Ne, Mg, Si, and Fe vary dramatically throughout the ISM from sub-solar values ($\sim$0.2) up to several times solar. We also investigate in detail the physics of the hot emitting gas, deriving measures for the hot-gas mass ($\sim 10^7$ solar masses), cooling times ($10^7-10^8$ yr), and pressure ( $3.5x10^{-11} - 2.8x10^{-10}$ dyne cm$^{-2}$). At least in one of the two nuclei (NGC 4038) the hot-gas pressure is significantly higher than the CO pressure, implying that shock waves may be driven into the CO clouds. Comparison of the metal abundances with the average stellar yields predicted by theoretical models of SN explosions points to SNe of Type II as the main contributors of metals to the hot ISM. There is no evidence of any correlation between radio-optical star-formation indicators and the measured metal abundances. although due to uncertainties in the average gas density we cannot exclude that mixing may have played an important role, the short time required to produce the observed metal masses ($<$2 Myr) suggests that the correlations are unlikely to have been destroyed by efficient mixing. More likely, a significant fraction of SN II ejecta may be in a cool phase, in grains, or escaping in hot winds.

Outflows, Edges, & Wakes: Probing Galaxy Evolution with Chandra and XMM-Newton

Marie Machacek, Christine Jones, William Forman, Paul Nulsen, Ralph Kraft (SAO)

An array of physical processes, often acting in concert, affect the evolution of galaxies and the intracluster medium (ICM) in groups and clusters. These processes include tidal interactions from galaxy collisions and mergers, ram pressure and turbulent viscous stripping of galaxy gas caused by the galaxy's motion through the ambient group/cluster gas, and outflows induced by star formation and/or AGN activity powered by accretion onto a central black hole within the galaxy. Each process imprints characteristic signatures, such as cavities, surface brightness edges, and wakes, on the hot gas in and near the galaxy. We use Chandra and XMM-Newton X-ray observations of nearby galaxies, spanning a range of galaxy types and environments, including spiral galaxies NGC 6872 in Pavo and NGC 2276 in the NGC 2300 group, and elliptical galaxies NGC 4552 in Virgo, NGC 7619 in Pegasus I, and the interacting pair NGC 4782/3, to investigate the physical processes at work in the evolution of these systems. This work was supported in part by the Smithsonian Institution, Chandra X-ray Center, and NASA grant GO3-4176A.

[PDF of the poster]

Galaxy X-ray Coronae in Nearby Hot Clusters

Ming Sun (Harvard-Smithsonian Center for Astrophysics/MSU), Bill Forman, Christine Jones (SAO)

We present the first systematic investigation of X-ray thermal coronae of both early-type and late-type galaxies in hot clusters. About 130 galaxies in 16 nearby hot clusters were examined, based on the archival Chandra data (46 pointings with a total exposure of 1.5 Msec). small cool X-ray coronae of early-type galaxies (1-4 kpc in radius, 0.5 - 1.5 keV), pressure confined in hot ($>$ 3 keV) clusters, are found to be very common, although their properties have been significantly modified by the dense ICM environment. Despite the effects of gas stripping, ICM evaporation, intense radiative cooling and AGN outbursts of the central SMBH, the common survival of these dense mini cooling cores puts interesting constraints on relevant physics, e.g., cooling, AGN feedbacks and transport processes. The detailed analysis for the $\sim$ 10 brightest coronae (temperature and pressure profiles etc.) will also be presented. Several coronae of late-type galaxies were also detected, with $L_X$ roughly scaled with the SF rate.

Chandra Observations of Circumnuclear Star Formation in NGC 3351

Douglas Swartz (USRA NASA/MSFC), Mihoko Yukita (Univ. of Alabama in Huntsville), Roberto Soria (Harvard-Smithsonian Center for Astrophysics), Allyn Tennant (NASA/MSFC), Kajal Ghosh (USRA NASA/MSFC), Kinwah Wu (MSSL,Univ. College London)

The nearby SB(r)b galaxy NGC 3351 (M95) displays a $\sim$20 arcsec diameter star-forming nuclear ring fueled by gas accreted through a stellar bar. The X-ray emission from this region is composed of numerous point-like sources embedded in hot (kT=0.5 keV) nonuniform diffuse gas. Most of the point-like sources are themselves small ($\sim$50 pc) concentrations of hot gas though some are clearly hard and variable XRBs. The X-ray emission lies near the UV and Halpha hotspots but is, in general, not coincident with these star forming clusters. The X-ray morphology is basically ring-like, in particular the center of the galaxy lacks both large amounts of hot gas and any point-like source above an estimated X-ray luminosity of 1e37 erg/s in the 0.3-8.0 keV band. The X-ray and Halpha morphologies of the ring and surrounding regions can be explained by the evolution of localized star formation combined with outflows from the central regions of NGC 3351.

Chemistry and Cavities in the Atmospheres of Elliptical Galaxies

Raymond White (Univ. of Alabama), David Davis (UMBC / NASA GSFC)

We describe the spatial distribution of chemical abundances in the atmospheres of three elliptical galaxies (NGC 1407, NGC 4125 and NGC 4552) and compare them to the stellar abundances in the same galaxies. The atmospheres of NGC 4125 and 4552 also contain multiple cavities likely caused by intermittent AGN activity, allowing us to constrain the AGN activity duty cycle. The association of low-mass X-ray binaries with globular cluster candidates in these three galaxies will also be described.