JoXSZ: Joint X-SZ fitting code for galaxy clusters

Abstract

<jats:p>The thermal Sunyaev-Zeldovich (SZ) effect and the X-ray emission offer separate and highly complementary probes of the thermodynamics of the intracluster medium. We present <jats:monospace>JoXSZ</jats:monospace>, the first publicly available code designed to jointly fit SZ and X-ray data coming from various instruments to derive the thermodynamic profiles of galaxy clusters. <jats:monospace>JoXSZ</jats:monospace> follows a fully Bayesian forward-modelling approach, accounts for the SZ calibration uncertainty, and for the X-ray background level systematic. It improves upon most current and not publicly available analyses because it adopts the correct Poisson-Gauss expression for the joint likelihood, makes full use of the information contained in the observations, even in the case of missing values within the datasets, has a more inclusive error budget, and adopts a consistent temperature in the various parts of the code, allowing for differences between X-ray and SZ gas-mass weighted temperatures when required by the user. <jats:monospace>JoXSZ</jats:monospace> accounts for beam smearing and data analysis transfer function, accounts for the temperature and metallicity dependencies of the SZ and X-ray conversion factors, adopts flexible parametrisation for the thermodynamic profiles, and on user request, allows either adopting or relaxing the assumption of hydrostatic equilibrium (HE). When HE holds, <jats:monospace>JoXSZ</jats:monospace> uses a physical (positive) prior on the radial derivative of the enclosed mass and derives the mass profile and overdensity radii <jats:italic>r</jats:italic><jats:sub>Δ</jats:sub>. For these reasons, <jats:monospace>JoXSZ</jats:monospace> goes beyond simple SZ and electron density fits. We illustrate the use of <jats:monospace>JoXSZ</jats:monospace> by combining Chandra and NIKA data of the high-redshift cluster CL J1226.9+3332. The code is written in Python, it is fully documented, and the users are free to customise their analysis in accordance with their needs and requirements. <jats:monospace>JoXSZ</jats:monospace> is publicly available on GitHub.</jats:p>

PANCO2: A new software to measure pressure profiles from resolved thermal SZ observations

“…Other codes have been publicly released in recent years, offering different and complementary options (see e.g. [11], offering joint modeling of SZ and X-ray signal, but no treatment of point source contamination).…”

“…The NIKA2 SZ Large Program (hereafter LPSZ, [1,2]) is a follow-up of 50 intermediatehigh redshift galaxy clusters (0.5 < z < 0.9, M 500 ∈ [3,11] × 10 14 M ). SZ observations are performed using the high angular resolution NIKA2 camera, observing at 150 and 260 GHz with respective angular resolutions 18" and 11" [3].…”

Many-probes multi-object spatially-resolved analyses of galaxy clusters in the big data era

“…The components required for processing X-ray data, i.e. the response matrix file (RMF) and the ancillary response file (ARF), must be provided by the user (see [4] for more details).…”

“…After specification, JoXSZ will process the data accordingly. JoXSZ has been already used for data coming from Chandra, NIKA and MUSTANG [4,7], and is being used for data from XMM, XRT, SPT, and Planck [8]. JoXSZ is also able to read data in di↵erent formats, and to automatically handle measurement units throughout the code using astropy.units [9] upon correct specification from the user of the measurement units of input data.…”

Thermodynamic evolution of the $z=1.75$ galaxy cluster IDCS J1426.5+3508

“…The Chandra ACIS-I X-ray data (obs ID 15168, 16321 with total exposure time of 100 ks; PI: Brodwin) were reduced following the standard procedures (e.g., Castagna & Andreon 2020). We briefly review the procedures here.…”