Galaxy cluster scaling relations measured with APEX-SZ

Abstract

We present thermal Sunyaev-Zel'dovich effect (SZE) measurements for 42 galaxy clusters observed at 150 GHz with the APEX-SZ experiment. For each cluster, we model the pressure profile and calculate the integrated Comptonization Y to estimate the total thermal energy of the intracluster medium (ICM). We compare the measured Y values to X-ray observables of the ICM from the literature (cluster gas mass M gas , temperature T X , and Y X = M gas T X ) that relate to total cluster mass. We measure power law scaling relations, including an intrinsic scatter, between the SZE and X-ray observables for three subsamples within the set of 42 clusters that have uniform X-ray analysis in the literature. We observe that differences between these X-ray analyses introduce significant variability into the measured scaling relations, particularly affecting the normalization. For all three subsamples, we find results consistent with a self-similar model of cluster evolution dominated by gravitational effects. Comparing to predictions from numerical simulations, these scaling relations prefer models that include cooling and feedback in the ICM. Lastly, we measure an intrinsic scatter of ∼ 28 per cent in the Y − Y X scaling relation for all three subsamples.

Weak-lensing mass calibration of the Sunyaev–Zel’dovich effect using APEX-SZ galaxy clusters

“…Typically, 140-170 live channels were used for further analysis. After these initial steps, an optical time constant (time delay in bolometer response) was de-convolved from each channel, using the approach of Bender et al (2016). The polysecant (a polynomial + secant model) fitting employed by Bender et al (2016) was also used here.…”

“…After these initial steps, an optical time constant (time delay in bolometer response) was de-convolved from each channel, using the approach of Bender et al (2016). The polysecant (a polynomial + secant model) fitting employed by Bender et al (2016) was also used here. To the time stream of each channel and subscan, we fit a 6th order polynomial plus a normalization of the expected variation of signal along a circle due to air mass load, and subtracted this baseline from the data.…”

“…After filtering, the point source transfer function represents the impulse response of the filter, and can be used, under the assumptions of directional independence and linearity of the filter, to model the response of any model that one may wish to compare to the data. Images of the data and the transfer functions were made using the methods outlined by Bender et al (2016). For each target we also created 100 noise images by randomly inverting half the data (randomly chosen subscans), to characterize instrument noise properties.…”

“…Based on the assumed parametrisation of the gNFW profile, Y sph,500 is obtained by dividing the Y cyl,500 by a factor of 1.203. To check for statistical compatibility between the integrated Comptonizations reported in Bender et al (2016) and this work, we use the centroids and apertures quoted in the former and re-measure the integrated Comptonizations for 41 clusters. We find a statistical agreement between the two pipelines across this sample.…”

Weak lensing measurements of the APEX-SZ galaxy cluster sample

“…Weak-lensing mass estimation have been actively pursued for numerous galaxy cluster samples (e.g., Applegate et al 2014;Postman et al 2012) of typical sample size of ∼ 20 to 50 clusters. In this paper, we present the weak gravitational lensing analysis of the APEX-SZ galaxy cluster sample (Bender et al 2016;Nagarajan et al 2018) comprising of 39 galaxy clusters in the redshift range of z = 0.1 to z = 0.83. Most of these clusters are X-ray selected.…”