Sunyaev-Zeldovich Effect Studies of Galaxy Clusters with Bolocam (and Future Instrumentation)

Galaxy clusters are excellent laboratories for studying the astrophysics of gravitational collapse and the non-self-similar processes that can affect it. A number of different techniques allow us to study the distribution of the consituents of galaxy clusters. The thermal Sunyaev-Zeldovich effect measures the line-of-sight integral of the the pressure in the ICM plasma. Comparison to and combination with other probes enables a variety of studies of the ICM and of clusters: scaling relations, radial profiles, tests of hydrostatic equilibrium, etc. We report on the status of our program to image clusters in the thermal Sunyaev-Zeldovich effect at 150 GHz using Bolocam and perform such tests. We also describe the upcoming MKIDCam long-wavelength multi-color facility camera for the CSO, which will provide new capabilities in thermal Sunyaev-Zeldovich effect imaging. We comment on the role Tom Phillips and the CSO have played in facilitating the development of mm-wave SZ observations

SZ contribution to characterize the shape of galaxy cluster haloes

We present the on-going activity to characterize the geometrical properties of the gas and dark matter haloes using multi-wavelength observations of galaxy clusters. The role of the SZ signal in describing the gas distribution is discussed for the pilot case of the CLASH object MACS J1206.2-0847

Unveiling the Dynamical State of Massive Clusters through the ICL Fraction

We have selected a sample of 11 massive clusters of galaxies observed by the Hubble Space Telescope in order to study the impact of the dynamical state on the intracluster light (ICL) fraction, the ratio of total integrated ICL to the total galaxy member light. With the exception of the Bullet cluster, the sample is drawn from the Cluster Lensing and Supernova Survey and the Frontier Fields program, containing five relaxed and six merging clusters. The ICL fraction is calculated in three optical filters using the CHEFs ICL estimator, a robust and accurate algorithm free of a priori assumptions. We find that the ICL fraction in the three bands is, on average, higher for the merging clusters, ranging between ~7% and 23%, compared with the ~2%–11% found for the relaxed systems. We observe a nearly constant value (within the error bars) in the ICL fraction of the regular clusters at the three wavelengths considered, which would indicate that the colors of the ICL and the cluster galaxies are, on average, coincident and, thus, so are their stellar populations. However, we find a higher ICL fraction in the F606W filter for the merging clusters, consistent with an excess of lower-metallicity/younger stars in the ICL, which could have migrated violently from the outskirts of the infalling galaxies during the merger event

Policy Responsiveness and Political Accountability in City Politics

Peculiar patterns have emerged in municipal politics in Canada. Unlike at federal and provincial levels of government, party politics is weak or absent in cities. But looking at the entire history of municipal elections of three Western Canadian cities — Calgary, Edmonton and Vancouver — also finds that, again unlike politicians at higher levels, municipal representatives are increasingly more likely to win repeated re-elections, facing a much lower threat from any competitive challenge. In addition, the careers of municipal politicians are growing steadily longer, leading to relatively stable, almost static, city governments that tend to see change most commonly when councillors choose to step down, rather than being forced out.Such patterns, of course, run counter to the general presumption in lively democracies, including this one, that the responsiveness of government leaders (that is, following the wishes of their constituents) and their accountability for the actions they take are best served by frequent turnovers in government: The need to throw politicians out every now and again to let new ones try and do things better. Whether the remarkable levels of stability and incumbency on city councils actually do serve the best interests of voters is unclear. More clear is that the lack of a party system at the city level seems to have contributed to this peculiar dynamic, and that city politicians have an interest in keeping it that way.While party affiliations provide a candidate some benefits in the form of campaign co-ordination, they also provide voters with increased clarity about what each candidate stands for policy-wise. That might be helpful to voters, but city politicians might find it more useful to blur their positions, leaving voters uncertain of exactly how to define a specific councillor’s stand, overall. The amount of information required to root through a councillor’s voting record, and the relatively light media coverage of daily council business, leaves most voters inclined to rely on something other than political signals when they decide who to support. Inevitably, a candidate’s personal character and length of experience take on a larger priority in the voting decision. So, the longer a councillor serves, the longer he or she might be likely to keep serving.The natural outcome of this phenomenon is that city councils are less likely to become polarized as councillors have an incentive to seek consensus by limiting obvious policy distinctions between themselves and their fellow representatives, contributing to a dynamic where city council works more like a corporate body and less like a partisan legislature. As long as citizens remain largely unperturbed by the overall actions of their city council, they might judge the risk of replacing them at election time as unnecessarily high compared to sticking with the status quo.This behaviour challenges much of the prevailing theory about how political processes improve political responsiveness and accountability. This is occurring at a time when cities are emerging as important and increasingly powerful nodes in the modern global economy. That the very nature of how they are governed is diverging so markedly from the norm that Canadians have come to expect from other levels of government is not something to be considered lightly

A kinetic inductance detectors array design for high background conditions at 150 GHz

We present a design for an array of kinetic inductance detectors (KIDs) integrated with phased array antennas for imaging at 150 GHz under high background conditions. The microstrip geometry KID detectors are projected to achieve photon noise limited sensitivity with larger than 100 pW absorbed optical power. Both the microstrip KIDs and the antenna feed network make use of a low-loss amorphous silicon dielectric. A new aspect of the antenna implementation is the use of a NbTiN microstrip feed network to facilitate impedance matching to the 50 Ohm antenna. The array has 256 pixels on a 6-inch wafer and each pixel has two polarizations with two Al KIDs. The KIDs are designed with a half wavelength microstrip transmission line with parallel plate capacitors at the two ends. The resonance frequency range is 400 to 800 MHz. The readout feedline is also implemented in microstrip and has an impedance transformer from 50 Ohm to 9 Ohm at its input and output.Comment: 6 pages, 3 figures, Journal of Low Temperature Physic

SZ contribution to characterize the shape of galaxy cluster haloes

We present the on-going activity to characterize the geometrical properties of the gas and dark matter haloes using multi-wavelength observations of galaxy clusters. The role of the SZ signal in describing the gas distribution is discussed for the pilot case of the CLASH object MACS J1206.2-0847

CLUMP-3D. Testing Λ\LambdaCDM with galaxy cluster shapes

The $\Lambda$CDM model of structure formation makes strong predictions on concentration and shape of DM (dark matter) halos, which are determined by mass accretion processes. Comparison between predicted shapes and observations provides a geometric test of the $\Lambda$CDM model. Accurate and precise measurements needs a full three-dimensional analysis of the cluster mass distribution. We accomplish this with a multi-probe 3D analysis of the X-ray regular CLASH (Cluster Lensing And Supernova survey with Hubble) clusters combining strong and weak lensing, X-ray photometry and spectroscopy, and the Sunyaev-Zel'dovich effect. The cluster shapes and concentrations are consistent with $\Lambda$CDM predictions. The CLASH clusters are randomly oriented, as expected given the sample selection criteria. Shapes agree with numerical results for DM-only halos, which hints at baryonic physics being not so effective in making halos rounder.Comment: v2: 8 pages, in press on ApJL. Extended discussion on regularity. One of three new companion papers of the CLUMP-3D project (Keiichi Umetsu et al., arxiv:1804.00664; I-Non Chiu et al., arXiv:1804.00676