Alma-Sz Detection of a Galaxy Cluster Merger Shock at Half the Age of the Universe

Basu, Kaustuv; Sommer, Martin W.; Erler, Jens; Eckert, D.; Vazza, Franco; Magnelli, B.; Bertoldi, F.; Tozzi, P.

doi:10.3847/2041-8205/829/2/l23

Cited by 41 publications

(51 citation statements)

References 31 publications

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“…Indeed, analogous approaches have already been shown over the past two decadeds to provide a reliable technique for studying interferometric observations of the SZ effect (see e.g. Carlstrom et al 1996;LaRoque et al 2006;Feroz et al 2009;Mroczkowski et al 2009;Basu et al 2016;Abdulla et al 2019, for an incomplete list of examples of applications of the interferometric modelling technique). We therefore follow this method as well in our joint SZ analysis, rather than relying on image-space techniques, while incorporating some of the recent advances in Bayesian and uv-space modelling.…”

Section: Introductionmentioning

confidence: 99%

“…Nevertheless, radio interferometers remain the only instruments so far capable of measuring the SZ effect with an angular resolution better than 5 arcsec. The first pioneering observations of the SZ effect with the Atacama Large Millimeter/Submillimeter Array (ALMA) demonstrated its ability to provide images of galaxy clusters with such unprecedented angular resolution (Kitayama et al 2016) and to detect discontinuities in the pressure distribution of the ICM (Basu et al 2016). Unfortunately, analysis techniques used for single-dish SZ effect imaging cannot be easily generalized for the fitting of images obtained from interferometric data.…”

Section: Introductionmentioning

confidence: 99%

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A joint ALMA–Bolocam–Planck SZ study of the pressure distribution in RX J1347.5−1145

Mascolo

Churazov

Mroczkowski

2019

Monthly Notices of the Royal Astronomical Society

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We report the joint analysis of single-dish and interferometric observations of the Sunyaev-Zeldovich (SZ) effect from the galaxy cluster RX J1347.5-1145. We have developed a parametric fitting procedure that uses native imaging and visibility data, and tested it using the rich data sets from ALMA, Bolocam, and Planck available for this object. RX J1347.5-1145 is a very hot and luminous cluster showing signatures of a merger. Previous X-ray-motivated SZ studies have highlighted the presence of an excess SZ signal south-east of the X-ray peak, which was generally interpreted as a strong, shock-induced pressure perturbation. Our model, when centred at the X-ray peak, confirms this. However, the presence of two almost equally bright giant elliptical galaxies separated by ∼ 100 kpc makes the choice of the cluster centre ambiguous, and allows for considerable freedom in modelling the structure of the galaxy cluster. For instance, we have shown that the SZ signal can be well-described by a single smooth ellipsoidal generalized Navarro-Frenk-White profile, where the best-fitting centroid is located between the two brightest cluster galaxies. This leads to a considerably weaker excess SZ signal from the south-eastern substructure. Further, the most prominent features seen in the X-ray can be explained as predominantly isobaric structures, alleviating the need for highly supersonic velocities, although overpressurized regions associated with the moving subhaloes are still present in our model.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A joint ALMA–Bolocam–Planck SZ study of the pressure distribution in RX J1347.5−1145

Mascolo

Churazov

Mroczkowski

2019

Monthly Notices of the Royal Astronomical Society

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“…In the bottom panel the ALMA SZ data indicates a modulated flux (red dot-dashed line) which is the result of interferometric imaging of a step function-like shock signal (shown with the green solid line for the best-fit model). Figures adapted from Basu et al (2016). tected, while the rest of the ICM contribution is filtered by the instrumental response. There is a same problem with interferometric observations, such as those performed with ALMA, as discussed below.…”

Section: Shock Frontsmentioning

confidence: 99%

Astrophysics with the Spatially and Spectrally Resolved Sunyaev-Zeldovich Effects

et al. 2019

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2 Tony Mroczkowski et al.Abstract In recent years, observations of the Sunyaev-Zeldovich (SZ) effect have had significant cosmological implications and have begun to serve as a powerful and independent probe of the warm and hot gas that pervades the Universe. As a few pioneering studies have already shown, SZ observations both complement X-ray observations -the traditional tool for studying the intra-cluster medium -and bring unique capabilities for probing astrophysical processes at high redshifts and out to the low-density regions in the outskirts of galaxy clusters. Advances in SZ observations have largely been driven by developments in centimetre-, millimetre-, and submillimetre-wave instrumentation on ground-based facilities, with notable exceptions including results from the Planck satellite. Here we review the utility of the thermal, kinematic, relativistic, non-thermal, and polarised SZ effects for studies of galaxy clusters and other large scale structures, incorporating the many advances over the past two decades that have impacted SZ theory, simulations, and observations. We also discuss observational results, techniques, and challenges, and aim to give an overview and perspective on emerging opportunities, with the goal of highlighting some of the exciting new directions in this field.Keywords Sunyaev-Zeldovich Effect · Clusters of Galaxies · Intra-cluster medium · Millimetre and Submillimetre-wave astronomy · Cosmology

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“…Apart from its morphology, the main parameter defining the shock is the ratio of downstream to upstream pressure at the jump itself. In practice, for a fixed line-of-sight geometry, the available ALMA+ACA data are mainly sensitive to the absolute difference of the downstream and upstream electron pressures near the nose of the shock, i.e., ∆P e = P e,ds − P e,us ; the SZ signal associated with the large-scale distribution of the gas is effectively filtered out (see, e.g., Basu et al 2016, and discussion in Section 3.2). Thus, the modelling of the ALMA signal remains only weakly sensitive to the assumed large-scale model.…”

Section: Sionmentioning

confidence: 99%

“…In fact, due to the lack of information on the pressure normalization, the marginalized posterior distribution of the Mach number inferred when performing an SZ-only analysis are found to entirely span the corresponding prior interval. To get a meaningful measure of the pressure jump from the ALMA+ACA data, we therefore employ an X-ray-informed analysis of the ALMA+ACA SZ observations as in Section 3.3 of Basu et al (2016), and set the upstream electron pressure P e,us to the value derived by modelling the Chandra data in a narrow sector centered on the shock nose (Markevitch 2006).…”

Section: Sionmentioning

confidence: 99%

An ALMA+ACA measurement of the shock in the Bullet Cluster

Mascolo

Mroczkowski

Churazov

et al. 2019

A&A

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Context. The thermal Sunyaev-Zeldovich (SZ) effect presents a relatively new tool for characterizing galaxy cluster merger shocks, traditionally studied through X-ray observations. Widely regarded as the "textbook example" of a cluster merger bow shock, the western, most-prominent shock front in the Bullet Cluster (1E0657-56) represents the ideal test case for such an SZ study. Aims. We aim to characterize the shock properties using deep, high-resolution interferometric SZ effect observations in combination with priors from an independent X-ray analysis. Methods. Our analysis technique relies on the reconstruction of a parametric model for the SZ signal by directly and jointly fitting data from the Atacama Large Millimeter/submillimeter Array (ALMA) and Atacama Compact Array (ACA) in Fourier space. Results. The ALMA+ACA data are primarily sensitive to the electron pressure difference across the shock front. To estimate the shock Mach number M, this difference can be combined with the value for the upstream electron pressure derived from an independent Chandra X-ray analysis. In the case of instantaneous electron-ion temperature equilibration, we find M = 2.08 +0.12 −0.12 , in ∼ 2.4σ tension with the independent constraint from Chandra, M X = 2.74 ± 0.25. The assumption of purely adiabatic electron temperature change across the shock leads to M = 2.53 +0.33 −0.25 , in better agreement with the X-ray estimate M X = 2.57 ± 0.23 derived for the same heating scenario. Conclusions. We have demonstrated that interferometric observations of the thermal SZ effect provide constraints on the properties of the shock in the Bullet Cluster that are highly complementary to X-ray observations. The combination of X-ray and SZ data yields a powerful probe of the shock properties, capable of measuring M and addressing the question of electron-ion equilibration in cluster shocks. Our analysis is however limited by systematics related to the overall cluster geometry and the complexity of the post-shock gas distribution. To overcome these limitations, a simultaneous, joint-likelihood analysis of SZ and X-ray data is needed.Key to identifying merging clusters is the detection of shocks in the ICM. A "textbook example of a bow shock" is observed in the X-ray image of the Bullet Cluster (Markevitch et al. 2002). Using 500 ks of Chandra X-ray data, Markevitch (2006) reported a Mach number M = 3.0 ± 0.4 for the western, mostprominent shock in the Bullet Cluster, an estimate largely determined by the density jump conditions. We also note that Shimwell et al. (2015) revealed a second shock, on the eastern (opposite) side of the cluster, which we do not consider here.Here we present deep, continuum Atacama Large Millimeter/submillimeter Array (ALMA) observations, sensitive to the thermal Sunyaev-Zeldovich (tSZ; Sunyaev & Zeldovich 1972) effect, of the main shock in the Bullet Cluster. These observations include data from both the 12-meter array (hereafter "ALMA") and 7-meter Atacama Compact (Morita) Array (ACA). As the tSZ effect is linearly ...

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Alma-Sz Detection of a Galaxy Cluster Merger Shock at Half the Age of the Universe

Cited by 41 publications

References 31 publications

A joint ALMA–Bolocam–Planck SZ study of the pressure distribution in RX J1347.5−1145

A joint ALMA–Bolocam–Planck SZ study of the pressure distribution in RX J1347.5−1145

Astrophysics with the Spatially and Spectrally Resolved Sunyaev-Zeldovich Effects

An ALMA+ACA measurement of the shock in the Bullet Cluster

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