X-RAY PROPERTIES OF GROUPS OF GALAXIES

By J. Mulchaey. 2000

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▪ Abstract ROSAT observations indicate that approximately half of all nearby groups of galaxies contain spatially extended X-ray emission. The radial extent of the X-ray emission is typically 50–500 h−1100 kpc or approximately 10–50% of the virial radius of the group. Diffuse X-ray emission is generally restricted to groups that contain at least one early-type galaxy. X-ray spectroscopy suggests the emission mechanism is most likely a combination of thermal bremsstrahlung and line emission. This interpretation requires that the entire volume of groups be filled with a hot, low-density gas known as the intragroup medium. ROSAT and ASCA observations indicate that the temperature of the diffuse gas in groups ranges from approximately 0.3 keV to 2 keV. Higher temperature groups tend to follow the correlations found for rich clusters between X-ray luminosity, temperature, and velocity dispersion. However, groups with temperatures below approximately 1 keV appear to fall off the cluster LX-T relationship (and p...

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

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Citations in the corpus

Mass, metal, and energy feedback in cosmological simulations (2007, background): “Of course, X-ray emission at ∼ 1 keV has a significant contribution from metal lines, and observations can be subject to surface brightness effects (e.g. Mulchaey 2000), so this comparison is only preliminary.”
Physical Implications of the X-ray Properties of Galaxy Groups and Clusters (2001, methodology): “Firstly, it is possible that many, if not most, of the discrepant trends mentioned above are the result of observational biases arising due to the low surface brightnesses of the lower mass systems (Mulchaey 2000); we will discuss this issue in §4.”
Pre-Processing of Galaxies before Entering a Cluster (2003, background): “At least for nearby clusters and groups, observations suggest that such non-gravitational heating did happen (Ponman et al. 1999; Lloyd-Davies et al. 2000; Mulchaey 2000; Mulchaey et al. 2003).”
THE EVOLUTION OF X-RAY CLUSTERS OF GALAXIES (2002, background): “…(1988) and Borgani & Guzzo (2001) for large–scale structure studies of galaxy clusters; Fabian (1994) for the physics of cooling flows in clusters; Mulchaey (2000) for the X-ray properties of galaxy groups; Birkinshaw (1999) and Carlstrom et al. (2001) for cluster studies with the…”
A Wide-Field Survey of Two z ~ 0.5 Galaxy Clusters: Identifying the Physical Processes Responsible for the Observed Transformation of Spirals into S0s (2007, background): “Indeed, X-ray observations of groups in the local universe reveal that they often harbor an intra-group medium (Mulchaey 2000), and simulations by Bekki et al. (2002) suggest that the starvation mechanism can operate similarly within large groups as it would in the overall cluster (see also Hester…”
An X-Ray Atlas of Groups of Galaxies (2003, background): “There is also a trend for the hotter groups to be detected to a larger fraction of the virial radius (Mulchaey 2000).”
Physical properties and environments of nearby galaxies (2009, background): “Most of the baryons in the Universe appear to be in warm or hot gas in the space between galaxies (in groups and clusters, this gas is directly detectable in the X-rays; Mulchaey 2000; Rosati, Borgani & Norman 2002).”
Gas expulsion by quasar-driven winds as a solution to the overcooling problem in galaxy groups and clusters (2010, background): “…formation and evolution of galaxy groups is crucial to solving the general problem of galaxy formation, as groups contain most of the galaxies in the Universe at the present day (e.g. Mulchaey 2000), and a large fraction of the universal stellar mass is formed in groups (e.g. Crain et al. 2009).”
Hot Gas In and Around Elliptical Galaxies (2003, result): “This approach is complementary to the recent ARAA review of the X-ray properties of galaxy groups by Mulchaey (2000) who presents a more complete discussion of the observations.”
The GEMS project: X-ray analysis and statistical properties of the group sample (2004, methodology): “To the resulting sample of 45 selected groups, we added a further 13 which had previously been studied with the PSPC by Helsdon & Ponman (2000a), who in turn assembled their sample from those of Nolthenius (1993); Ledlow et al. (1996); Mulchaey & Zabludoff (1998), and two additional Hickson compact ”
Quantifying the effect of baryon physics on weak lensing tomography (2011, background): “…considered a free parameter in the fit to X-ray data, but we note that for a hydrostatic isothermal sphere its value corresponds to the ratio of the specific energy in galaxies to the specific energy in the hot gas (e.g., King 1972; Jones & Foreman 1984; see also Mulchaey 2000 for a review).”
The Search for the Missing Baryons at Low Redshift (2007, background): “The mass of hot gas in galaxy groups is not well determined because at the last radius where X-ray surface brightness is usually measured, the gas mass is rising as rm where m≈1.5 (e.g., Mulchaey 2000).”
HIPASS High-Velocity Clouds: Properties of the Compact and Extended Populations (2001, background): “Evidence for diffuse intergalactic material comes directly from intra-cluster X-ray emission at high-redshift (Mulchaey 2000) and the Lyα absorber systems (Penton, Shull, & Stocke 2000).”
CHARACTERIZING THE CIRCUMGALACTIC MEDIUM OF NEARBY GALAXIES WITH HST/COS AND HST/STIS ABSORPTION-LINE SPECTROSCOPY (2012, background): “Observationally, both in rich clusters and in smaller groups of galaxies dominated by massive ellipticals, the intracluster and intra-group diffuse gas emits copious X-rays (Sarazin 1988; Mulchaey 2000) and contains most of the baryons (White et al. 1993).”
The case for AGN feedback in galaxy groups (2009, background): “Galaxy groups, on the other hand, contain a large fraction of present day galaxies and a significant fraction of the overall universal baryon budget (e.g., Mulchaey 2000).”
Theoretical Challenges in Galaxy Formation (2016, background): “…systems are usually embedded in hot (> 105K) X-ray emitting gas comprising a significant fraction of the total baryonic mass (e.g. Anderson et al. 2015, Dai et al. 2010, Giodini et al. 2009, Kravtsov & Borgani 2012, Mulchaey 2000, Renzini & Andreon 2014, Sun et al. 2009, Vikhlinin et al. 2006).”