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Register a new userThe Largest Gravitationally Bound Structures: The Corona Borealis Supercluster - Mass and Bound Extent
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Recent simulations of the densest portion of the Corona Borealis supercluster (A2061, A2065, A2067, and A2089) have shown virtually no possibility of extended gravitationally bound structure without inter-cluster matter (Pearson & Batuski). In contrast, recent analyses of the dynamics found that the clusters had significant peculiar velocities towards the supercluster centroid (Batiste & Batuski). In this paper we present the results of a thorough investigation of the CSC: we determine redshifts and virial masses for all 8 clusters associated with the CSC; repeat the analysis of Batiste & Batuski with the inclusion of A2056 and CL1529+29; estimate the mass of the supercluster by applying the virial theorem on the supercluster scale (e.g. Small et al.), the caustics method (e.g. Reisenegger et al.), and a new procedure using the spherical collapse model (SCM) with the results of the dynamical analysis (SCM+FP); and perform a series of simulations to assess the likelihood of the CSC being a gravitationally bound supercluster. We find that the mass of the CSC is between 0.6 and 12 x 10^{16} h^{-1} M_{sun}. The dynamical analysis, caustics method and the SCM+FP indicate that the structure is collapsing, with the latter two both indicating a turn around radius of about 12.5 h^{-1} Mpc. Lastly, the simulations show that with a reasonable amount of inter-cluster mass, there is likely extended bound structure in the CSC. Our results suggest that A2056, A2061, A2065, A2067, and A2089 form a gravitationally bound supercluster.
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We present a study of the Corona Borealis (CB) supercluster. We determined the high-density cores of the CB and the richest galaxy clusters in them, and studied their dynamical state and galaxy content. We determined filaments in the supercluster to analyse the connectivity of clusters. We compared the mass distribution in the CB with predictions from the spherical collapse model and analysed the acceleration field in the CB. We found that at a radius $R_{mathrm{30}}$ around clusters in the CB (A2065, A2061, A2089, and Gr2064) (corresponding to the density contrast $Deltarho approx 30$), the galaxy distribution shows a minimum. The $R_{30}$ values for individual clusters lie in the range of $3 - 6$ $h^{-1}$ Mpc. The radii of the clusters (splashback radii) lie in the range of $R_{mathrm{cl}} approx 2 - 3$ $R_{mathrm{vir}}$. The projected phase space diagrams and the comparison with the spherical collapse model suggest that $R_{mathrm{30}}$ regions have passed turnaround and are collapsing. Galaxy content in clusters varies strongly. The cluster A2061 has the highest fraction of galaxies with old stellar populations, and A2065 has the highest fraction of galaxies with young stellar populations. The number of long filaments near clusters vary from one at A2089 to five at A2061. During the future evolution, the clusters in the main part of the CB may merge and form one of the largest bound systems in the nearby Universe. Another part of the CB, with the cluster Gr2064, will form a separate system. The structures with a current density contrast $Deltarho approx 30$ have passed turnaround and started to collapse at redshifts $z approx 0.3 - 0.4$. The comparison of the number and properties of the most massive collapsing supercluster cores from observations and simulations may serve as a test for cosmological models.
Using data from the Sloan Digital Sky Survey we assess the current dynamical state of the Corona Borealis Supercluster (CSC), a highly dense and compact supercluster at z = 0.07. The Fundamental Plane relation is used to determine redshift independent distances to six clusters in the densest region of the supercluster, with mean accuracy in the relative distance estimates of 4 per cent. Peculiar velocities determined from these distance estimates indicate that the clusters have broken from the Hubble Flow, suggesting that the CSC likely contains two regions that have reached turnaround and are currently undergoing gravitational collapse. These results provide the strongest observational evidence to date that the CSC is a bound system similar to the much more extensive Shapley Supercluster, which is the most extensive confirmed bound supercluster yet identified in the Universe. When compared with simulations of the CSC our results require substantially more mass than is contained within the clusters, possibly indicating a significant inter-cluster dark matter component. In order to facilitate comparison with studies for which spectroscopic data are not available, an alternative analysis of the dynamics is made using the Kormendy relation as a distance indicator. The results are generally consistent with those of the Fundamental Plane and suggest similar global dynamics, but we find that the relatively sparse sampling of the clusters makes the Kormendy relation less reliable overall and more susceptible to small systematic differences between the cluster samples.
We have observed the Corona Borealis Supercluster with the Millimeter and Infrared Testa grigia Observatory (MITO), located in the Italian Alps, at 143, 214, 272, and 353 GHz. We present a description of the measurements, data analysis, and results of the observations together with a comparison with observations performed at 33 GHz with the Very Small Array (VSA) interferometer situated at the Teide Observatory (Tenerife-Spain). Observations have been made in the direction of the supercluster towards one Cosmic Microwave Background (CMB) cold spot previously detected in a VSA temperature map. Observational strategy and data analysis are described in detail, explaining the procedures used to disentangle primary and secondary anisotropies in the resulting maps. From a first level of data analysis we find evidence in MITO data of primary anisotropy, however still with room for the presence of secondary anisotropy, especially when VSA results are included. With a second level of data analysis using map-making and the maximum entropy method we claim a weak detection of a faint signal compatible with a SZ effect characterized at most by a Comptonization parameter $y=(7.8^{+5.3}_{-4.4})times10^{-6}$ 68% CL. The low level of confidence in the presence of a SZ signal invite us to study this sky region with higher sensitivity and angular resolution experiments like the already planned upgrad
(abridged) Radio recombination lines (RRLs) at frequencies $ u$ < 250 MHz trace the cold, diffuse phase of the ISM. Next generation low frequency interferometers, such as LOFAR, MWA and the future SKA, with unprecedented sensitivity, resolution, and large fractional bandwidths, are enabling the exploration of the extragalactic RRL universe. We observed the radio quasar 3C 190 (z~1.2) with the LOFAR HBA. In reducing this data for spectroscopic analysis, we have placed special emphasis on bandpass calibration. We devised cross-correlation techniques to significantly identify the presence of RRLs in a low frequency spectrum. We demonstrate the utility of this method by applying it to existing low-frequency spectra of Cassiopeia A and M 82, and to the new observations of 3C 190. RRLs have been detected in the foreground of 3C 190 at z = 1.12355 (assuming a carbon origin), owing to the first detection of RRLs outside of the local universe (first reported in Emig et al. 2019). Towards the Galactic supernova remnant Cas A, we uncover three new detections: (1) C$epsilon$-transitions ($Delta$n = 5) for the first time at low radio frequencies, (2) H$alpha$-transitions at 64 MHz with a FWHM of 3.1 km/s, the most narrow and one of the lowest frequency detections of hydrogen to date, and (3) C$alpha$ at v$_{LSR}$ = 0 km/s in the frequency range 55-78 MHz for the first time. Additionally we recover C$alpha$, C$beta$, C$gamma$, and C$delta$ from the -47 km/s and -38 km/s components. In the nearby starburst galaxy, M 82, we do not find a significant feature. Our current searches for RRLs in LOFAR observations are limited to narrow (< 100 km/s) features, owing to the relatively small number of channels available for continuum estimation. Future strategies making use of larger contiguous frequency coverage would aid calibration to deeper sensitivities and broader features.
Using the most recent kinematic and radial velocity data in the literature, we calculate the binding energy of Proxima Centauri relative to the center of mass of the Alpha Centauri system. When we adopt the centroids of the observed data, we find that the three stars constitute a bound system, albeit with a semi-major axis that is on order the same size as Alpha Centauri ABs Hill radius in the galactic potential. We carry out a Monte Carlo simulation under the assumption that the errors in the observed quantities are uncorrelated. In this simulation, 44% of the trial systems are bound, and systems on the 1-3 sigma tail of the radial velocity distribution can have Proxima currently located near the apastron position of its orbit. Our analysis shows that a further, very significant improvement in the characterization of the system can be gained by obtaining a more accurate measurement of the radial velocity of Proxima Centauri.
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