The intragroup medium in loose groups of galaxies

By S. F. Helsdon, Trevor J. Ponman. 2000

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We have used the ROSAT PSPC to study the properties of a sample of 24 X-ray-bright galaxy groups, representing the largest sample examined in detail to date. Hot plasma models are fitted to the spectral data to derive temperatures, and modified King models are used to characterize the surface brightness profiles. In agreement with previous work, we find evidence for the presence of two components in the surface brightness profiles. The extended component is generally found to be much flatter than that observed in galaxy clusters, and there is evidence that the profiles follow a trend with system mass. We derive relationships between X-ray luminosity, temperature and optical velocity dispersion. The relation between X-ray luminosity and temperature is found to be LX∝T4.9, which is significantly steeper than the same relation in galaxy clusters. These results are in good agreement with pre-heating models, in which galaxy winds raise the internal energy of the gas, inhibiting its collapse into the shallow potential wells of poor systems.

Subfields: Astronomy and Astrophysics, Instrumentation, Statistical and Nonlinear Physics

View Paper: https://www.semanticscholar.org/paper/eea95baf88e82c448a7ac1f6fe967f5829d61296

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Citations in the corpus

Hot Gas In and Around Elliptical Galaxies (2003, background): “However, in our particular universe this relation is somewhat steeper, Lx ∝ T 3 (e.g. Arnaud & Evrard 1999), and may become very steep (at least Lx ∝ T 4) for groups having kT ∼ 1 keV (Helsdon & Ponman 2000a,b).”
The Evolution of X-Ray Clusters and the Entropy of the Intracluster Medium (2000, background): “Such an entropy minimum bends the relation from self–similar L ∝ T 2 behaviour at very large scales (∼ 1015M⊙) towards a steeper slope on the scale of groups (∼ 1013 − 1014M⊙) which is actually observed (Ponman et al. 1996; Helsdon & Ponman 2000).”
Modified Entropy Models for the Intracluster Medium (2002, background): “We therefore suspect that the dispersion in the L-T data of Helsdon & Ponman (2000) arises from a combination of differing surface brightness biases and differing amounts of gas below the cooling threshold.”
Mass, metal, and energy feedback in cosmological simulations (2007, methodology): “This is now in the range for the canonical ICM metallicities of around 0.3 solar, as well as for groups between 0.316 and 3.16 keV as observed by Helsdon & Ponman (2000) (they found −0.60 [Fe/H] −0.36).”
THE EVOLUTION OF X-RAY CLUSTERS OF GALAXIES (2002, background): “For cooler groups, ∼ 1 keV, the Lbol–TX relation steepens, with a slope α ∼ 5 (e.g. Helsdon & Ponman 2000).”
The Birmingham-CfA cluster scaling Project – I. Gas fraction and the M-Tx relation (2003, methodology): “A further steepening of this slope is observed in the group regime (e.g. Helsdon & Ponman 2000), consistent with a flattening in the gas density profiles, which is evident in systems cooler than 3–4 keV (Ponman, Cannon & Navarro 1999).”
X‐ray properties of galaxy clusters and groups from a cosmological hydrodynamical simulation (2003, background): “1996; Helsdon & Ponman 2000; Sanderson et al. 2003), it agrees with other analyses which indicate a unique slope from the cluster to the group scales (Mulchaey & Zabludoff 1998).”
The cool-core bias in X-ray galaxy cluster samples - I. Method and application to HIFLUGCS (2010, methodology): “For galaxy groups, the relation is steeper (Helsdon & Ponman 2000), so at low temperatures (kT 1 keV) we use the corresponding determination of the LX −T relation (A = 9.55× 1042 ergs s−1, α = 4.9).”
Universal gas density and temperature profile (2001, methodology): “The data are taken from Mohr, Mathiesen & Evrard (1999) and Helsdon & Ponman (2000).r500 is calculated from the emission-weighted mean temperature through the normalization found by Mohr et al. (1999): r500 = 2.37 ( TX 10 keV )1/2 ( h 0.5 )−1 Mpc. (35) Despite the large scatter there is some…”
Quasar Feedback: The Missing Link in Structure Formation (2004, background): “If nongravitational heating were unimportant, the gas density distribution would be self-similar, resulting in LX / T 2 (Kaiser 1986), but instead the observed slope steepens considerably for low-temperature clusters (e.g., David et al. 1993; Arnaud & Evrard 1999; Helsdon & Ponman 2000).”
The Mass-to-Light Function of Virialized Systems and the Relationship between Their Optical and X-Ray Properties (2001, result): “…& Ponman 2000), we obtain the steeper relation LX ∝ T 3.9±1.2 which is in agreement with the theoretical predictions of Cavaliere, Menci & Tozzi (1997, 1999) (see the discussion at the end of the section) and in excellent agreement with the results LX ∝ T 4.9±0.9 of Helsdon & Ponman (2000).”
ERRATUM: “CHANDRA SAMPLE OF NEARBY RELAXED GALAXY CLUSTERS: MASS, GAS FRACTION, AND MASS–TEMPERATURE RELATION” (2006, ApJ, 640, 691) (2005, methodology): “This trend is responsible for flat gas density slopes derived for galaxy groups and low-mass clusters in the previous analyses using the -model approximations (e.g., Helsdon & Ponman 2000; Finoguenov et al. 2001; Sanderson & Ponman 2003).”
Physical Implications of the X-ray Properties of Galaxy Groups and Clusters (2001, methodology): “This is the strategy that has been adopted, for example, by Mulchaey (2000) in the construction of his Figure 3 and by Helsdon and Ponman (2000).”
The case for AGN feedback in galaxy groups (2009, methodology): “For comparison, we show in the left panel the ROSAT measurements of Helsdon & Ponman (2000) and Mulchaey et al. (2003) (temperatures uncorrected) and in the right panel the ROSAT measurements of Osmond & Ponman (2004) (cool core-corrected temperatures).”
Measuring Ωm with the ROSAT Deep Cluster Survey (2001, background): “For cooler groups, ∼ 1 keV, the Lbol–TX relation steepen, with a slope α ∼ 5 (e.g., Helsdon & Ponman 2000).”
An X-Ray Atlas of Groups of Galaxies (2003, methodology): “Figure 4 shows a comparison of the temperatures from our survey with the temperatures in Helsdon & Ponman (2000b).”
The entropy and energy of intergalactic gas in galaxy clusters (2000, result): “Low-mass systems have significantly flatter gas density profiles, with b dropping to ,0.4 for the galaxy groups, which agrees well with the Helsdon & Ponman (2000) Table 2.”
A comparison of weak-lensing masses and X-ray properties of galaxy clusters (2007, background): “For clusters with temperatures 2 keV the slope is ∼3, with even steeper slopes observed for lower temperature galaxy groups (e.g. Helsdon & Ponman 2000).”