ner_tags: O O O O O O O O O O O O O O O O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation O O O O O O O O B-Telescope O O O O O B-Citation I-Citation I-Citation I-Citation O B-Citation I-Citation O B-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Model O O O O O O O O O O O O O O B-Wavelength O O O O O O O B-Wavelength O O O O O O B-Citation I-Citation I-Citation I-Citation I-Citation I-Citation I-Citation I-Citation O O O O O O B-Citation I-Citation I-Citation I-Citation I-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Wavelength O O O O O O B-Dataset I-Dataset B-Citation I-Citation I-Citation I-Citation O O O O O B-CelestialObject O O O O B-Wavelength O O O O O O O O O O O O O O O O O O O O O B-Wavelength O O O O O O O O O O O O O O O O O B-Wavelength O O O O O O O O O O O O O O O O O O O O O O O O O O B-Wavelength O O O O B-Archive I-Archive I-Archive I-Archive O O O O O O O B-Observatory O O O O O O O O O O O O O O B-Citation I-Citation B-Observatory O O O O O O O B-Wavelength O B-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O B-Citation I-Citation I-Citation O O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation I-Citation B-Citation I-Citation I-Citation I-Citation O B-Citation I-Citation I-Citation I-Citation I-Citation I-Citation O O O O O O B-Citation I-Citation I-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O B-Citation I-Citation O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Wavelength O O O O O O O O O O
tokens: at 10 to 20%. However, a much larger bias has been invoked to reconcile cosmological parameters derived from the cosmic microwave background and cluster counts (Planck Collaboration XX 2014 ), although the calibration of the bias by Planck team has been amply discussed (von der Linden 2014 ; Andreon 2014 ; Smith et al. 2016 ). Caustic masses can provide an alternative calibration of the bias of hydrostatic masses. They are almost unused for this purpose (we are only aware of Maughan et al. 2016 ) and we exploit a new method for using this type of masses: if there is a relative bias between caustic and hydrostatic masses then there should be an offset in gas mass derived using the two masses. Throughout this paper, we assume , , and km s Mpc. Results of stochastic computations are given in the form , where and are the posterior mean and standard deviation. The latter also corresponds to 68% intervals because we only summarize posteriors close to Gaussian in this way. Logarithms are in base 10. 2. Sample selection, cluster masses, and X-ray data Sample selection, halo mass derivation, and X-ray data are presented and discussed in Andreon et al. ( 2016 , Paper I), and gas masses are derived in Andreon et al. ( 2017 , Paper II), to which we refer for details. We summarize here the work done. We used a sample of 34 clusters in the very nearby universe (, XUCS, for X-ray Unbiased Cluster Sample) extracted from the C4 catalog (Miller et al. 2005 ) in regions of low Galactic absorption. There is no X-ray selection in our sample, meaning that 1) the probability of inclusion of the cluster in the sample is independent of its X-ray luminosity (or count rate), and 2) no cluster is kept or removed on the basis of its X-ray properties, except for two clusters for which we cannot derive gas masses. The impact of this selection is discussed in Sect. 3.3. We collected the few X-ray observations present in the XMM-Newton or Chandra archives and we observed the remaining clusters with Swift (individual exposure times between 9 and 31 ks), as detailed in Table 1 of Paper I. Swift observations have the advantage of a low X-ray background (Moretti et al. 2009 ), making it extremely useful for sampling a cluster population that includes low surface brightness clusters (Andreon Moretti 2011 ). Caustic masses within 1 , , have been derived following Diaferio Geller ( 1997 ), Diaferio ( 1999 ), and Serra et al. ( 2011 ), then converted into and assuming a Navarro et al. ( 1997 ) profile with concentration . Adopting would change mass estimates by a negligible amount; see Paper I. The median number of members within the caustics is and the interquartile range is . The median mass of the cluster sample, , is and the interquartile range is 0.4 dex. The average mass error is 0.14 dex. Gas masses are derived by projecting a flexible radial profile, fitting its projection to the unbinned X-ray data, and propagating all modeled sources of uncertainties (e.g., spectral