Article

# A New Robust Low-Scatter X-ray Mass Indicator for Clusters of Galaxies

The Astrophysical Journal (Impact Factor: 6.28). 03/2006; DOI: 10.1086/506319

Source: arXiv

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**ABSTRACT:**We study the thermodynamic properties of the hot gas in a sample of groups in the 0.012-0.024 redshift range, using XMM-Newton observations. We present measurements of temperature, entropy, pressure and iron abundance. Non-parametric fits are used to derive the mean properties of the sample and to study dispersion in the values of entropy and pressure. The scaling of the entropy at 0.2r500 matches well the results of Ponman, Sanderson & Finoguenov. However, compared to cool clusters, the groups in our sample reveal larger entropy at inner radii and a substantially flatter slope in the entropy in the outskirts, compared to both the prediction of pure gravitational heating and observations of clusters. This difference corresponds to the systematically flatter group surface brightness profiles, reported previously. The scaled pressure profiles can be well approximated with a Sérsic model with n = 4. We find that groups exhibit a systematically larger dispersion in pressure, compared to clusters of galaxies, while the dispersion in entropy is similar.Monthly Notices of the Royal Astronomical Society 01/2007; 374(2):737-760. · 5.23 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**We investigate the regularity of cluster pressure profiles with REXCESS, a representative sample of 33 local (z < 0.2) clusters drawn from the REFLEX catalogue and observed with XMM-Newton. The sample spans a mass range of 1014 M&sun; < M500 < 1015 M&sun;, where M500 is the mass corresponding to a density contrast of 500. We derive an average profile from observations scaled by mass and redshift according to the standard self-similar model, and find that the dispersion about the mean is remarkably low, at less than 30 per cent beyond 0.2 R500, but increases towards the center. Deviations about the mean are related to both the mass and the thermo-dynamical state of the cluster. Morphologically disturbed systems have systematically shallower profiles while cooling core systems are more concentrated. The scaled profiles exhibit a residual mass dependence with a slope of ~0.12, consistent with that expected from the empirically-derived slope of the M500 - YX relation; however, the departure from standard scaling decreases with radius and is consistent with zero at R500. The scatter in the core and departure from self-similar mass scaling is smaller compared to that of the entropy profiles, showing that the pressure is the quantity least affected by dynamical history and non-gravitational physics. Comparison with scaled data from several state of the art numerical simulations shows good agreement outside the core. Combining the observational data in the radial range [0.03-1] R500 with simulation data in the radial range [1-4] R500, we derive a robust measure of the universal pressure profile, that, in an analytical form, defines the physical pressure profile of clusters as a function of mass and redshift up to the cluster "boundary". Using this profile and direct spherical integration of the observed pressure profiles, we estimate the integrated Compton parameter Y and investigate its scaling with M500 and LX, the soft band X-ray luminosity. We consider both the spherically integrated quantity, Ysph(R), proportional to the gas thermal energy, and the cylindrically integrated quantity, Ycyl(R)=YSZ DA2, which is directly related to the Sunyaev-Zel'dovich (SZ) effect signal. From the low scatter of the observed Ysph(R500) - YX relation we show that variations in pressure profile shape do not introduce extra scatter into the Ysph(R500) - M500 relation as compared to that from the YX - M500 relation. The Ysph(R500) - M500 and Ysph(R500) - LX relations derived from the data are in excellent agreement with those expected from the universal profile. This profile is used to derive the expected YSZ - M500 and YSZ - LX relations for any aperture.Astronomy and Astrophysics 07/2010; 517. · 4.48 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**Non-thermal motions in the intra-cluster medium (ICM) are believed to play a non-negligible role in the pressure support to the total gravitating mass of galaxy clusters. Future high-precision X-ray missions will allow us to directly detect the signature of these motions from highly resolved spectra of the ICM. With this perspective, we will present here a study on a set of clusters extracted from a cosmological hydrodynamical simulation, for which we simulated X-ray observations and characterized them via the non-thermal velocity amplitude of the ICM. We have applied the X-ray virtual telescope PHOX to generate mock observations of the simulated clusters and estimated in an observational fashion global X-ray properties. We included ICM non-thermal motions as additional parameter to further identify non-regular clusters. In particular, the influence of internal gas motions on the location of clusters in the L_X-T plane was investigated and was found that objects with the largest amount of non-thermal velocity have on average higher X-ray luminosities.Astronomische Nachrichten 04/2013; · 1.12 Impact Factor

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