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1
Dalal, Roohi, Michael A. Strauss, Tomomi Sunayama, Masamune Oguri, Yen-Ting Lin, Song Huang, Youngsoo Park und Masahiro Takada. „Brightest cluster galaxies are statistically special from z = 0.3 to z = 1“. Monthly Notices of the Royal Astronomical Society 507, Nr. 3 (17.08.2021): 4016–29. http://dx.doi.org/10.1093/mnras/stab2363.
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ABSTRACT We study brightest cluster galaxies (BCGs) in ∼5000 galaxy clusters from the Hyper Suprime-Cam (HSC) Subaru Strategic Program. The sample is selected over an area of 830 deg2 and is uniformly distributed in redshift over the range of z = 0.3−1.0. The clusters have stellar masses in the range of 1011.8−1012.9M⊙. We compare the stellar mass of the BCGs in each cluster to what we would expect if their masses were drawn from the mass distribution of the other member galaxies of the clusters. The BCGs are found to be ‘special’, in the sense that they are not consistent with being a statistical extreme of the mass distribution of other cluster galaxies. This result is robust over the full range of cluster stellar masses and redshifts in the sample, indicating that BCGs are special up to a redshift of z = 1.0. However, BCGs with a large separation from the centre of the cluster are found to be consistent with being statistical extremes of the cluster member mass distribution. We discuss the implications of these findings for BCG formation scenarios.
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Rennehan, Douglas, Arif Babul, Christopher C. Hayward, Connor Bottrell, Maan H. Hani und Scott C. Chapman. „Rapid early coeval star formation and assembly of the most-massive galaxies in the Universe“. Monthly Notices of the Royal Astronomical Society 493, Nr. 4 (27.02.2020): 4607–21. http://dx.doi.org/10.1093/mnras/staa541.
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Abstract The current consensus on the formation and evolution of the brightest cluster galaxies is that their stellar mass forms early ($z$ ≳ 4) in separate galaxies that then eventually assemble the main structure at late times ($z$ ≲ 1). However, advances in observational techniques have led to the discovery of protoclusters out to $z$ ∼ 7. If these protoclusters assemble rapidly in the early Universe, they should form the brightest cluster galaxies much earlier than suspected by the late-assembly picture. Using a combination of observationally constrained hydrodynamical and dark-matter-only simulations, we show that the stellar assembly time of a sub-set of brightest cluster galaxies occurs at high redshifts ( $z$ > 3) rather than at low redshifts ($z$ < 1), as is commonly thought. We find, using isolated non-cosmological hydrodynamical simulations, that highly overdense protoclusters assemble their stellar mass into brightest cluster galaxies within ∼1 Gyr of evolution – producing massive blue elliptical galaxies at high redshifts ($z$ ≳ 1.5). We argue that there is a downsizing effect on the cluster scale wherein some of the brightest cluster galaxies in the cores of the most-massive clusters assemble earlier than those in lower mass clusters. In those clusters with $z$ = 0 virial mass ≥ 5 × 1014 M⊙, we find that $9.8{{\ \rm per\ cent}}$ have their cores assembly early, and a higher fraction of $16.4{{\ \rm per\ cent}}$ in those clusters above 1015 M⊙. The James Webb Space Telescope will be able to detect and confirm our prediction in the near future, and we discuss the implications to constraining the value of σ8.
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Wen, Z. L., und J. L. Han. „Photometric redshifts for galaxies in the Subaru Hyper Suprime-Cam and unWISE and a catalogue of identified clusters of galaxies“. Monthly Notices of the Royal Astronomical Society 500, Nr. 1 (27.10.2020): 1003–17. http://dx.doi.org/10.1093/mnras/staa3308.
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ABSTRACT We first present a catalogue of photometric redshifts for 14.68 million galaxies derived from the 7-band photometric data of Hyper Suprime-Cam Subaru Strategic Program and the Wide-field Infrared Survey Explorer using the nearest-neighbour algorithm. The redshift uncertainty is about 0.024 for galaxies of z ≤ 0.7, and steadily increases with redshift to about 0.11 at z ∼ 2. From such a large data set, we identify 21 661 clusters of galaxies, among which 5537 clusters have redshifts z > 1 and 642 clusters have z > 1.5, significantly enlarging the high redshift sample of galaxy clusters. Cluster richness and mass are estimated, and these clusters have an equivalent mass of M500 ≥ 0.7 × 1014 M⊙. We find that the stellar mass of the brightest cluster galaxies (BCGs) in each richness bin does not significantly evolve with redshift. The fraction of star-forming BCGs increases with redshift, but does not depend on cluster mass.
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Ragone-Figueroa, C., G. L. Granato, S. Borgani, R. De Propris, D. García Lambas, G. Murante, E. Rasia und M. West. „Evolution and role of mergers in the BCG–cluster alignment. A view from cosmological hydrosimulations“. Monthly Notices of the Royal Astronomical Society 495, Nr. 2 (20.05.2020): 2436–45. http://dx.doi.org/10.1093/mnras/staa1389.
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ABSTRACT Contradictory results have been reported on the time evolution of the alignment between clusters and their brightest cluster galaxy (BCG). We study this topic by analysing cosmological hydrosimulations of 24 massive clusters with $M_{200}|_{z=0} \gtrsim 10^{15}\, \rm {\, M_{\odot }}$, plus 5 less massive with $1 \times 10^{14} \lesssim M_{200}|_{z=0} \lesssim 7 \times 10^{14}\, \rm {\, M_{\odot }}$, which have already proven to produce realistic BCG masses. We compute the BCG alignment with both the distribution of cluster galaxies and the dark matter (DM) halo. At redshift z = 0, the major axes of the simulated BCGs and their host cluster galaxy distributions are aligned on average within 20°. The BCG alignment with the DM halo is even tighter. The alignment persists up to z ≲ 2 with no evident evolution. This result continues, although with a weaker signal, when considering the projected alignment. The cluster alignment with the surrounding distribution of matter (3R200) is already in place at z ∼ 4 with a typical angle of 35°, before the BCG–cluster alignment develops. The BCG turns out to be also aligned with the same matter distribution, albeit always to a lesser extent. These results taken together might imply that the BCG–cluster alignment occurs in an outside–in fashion. Depending on their frequency and geometry, mergers can promote, destroy or weaken the alignments. Clusters that do not experience recent major mergers are typically more relaxed and aligned with their BCG. In turn, accretions closer to the cluster elongation axis tend to improve the alignment as opposed to accretions closer to the cluster minor axis.
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Pizzardo, M., J. Sohn, M. J. Geller, A. Diaferio und K. Rines. „Mass Accretion Rates of the HectoMAP Clusters of Galaxies“. Astrophysical Journal 927, Nr. 1 (01.03.2022): 26. http://dx.doi.org/10.3847/1538-4357/ac5029.
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Abstract We estimate the mass accretion rate (MAR) of 321 clusters of galaxies in the HectoMAP Cluster Survey. The clusters span the redshift range 0.17–0.42 and the M 200 mass range ≈ (0.5–3.5) × 1014 M ⊙. The MAR estimate is based on the caustic technique along with a spherical infall model. Our analysis extends the measurement of MARs for 129 clusters at z < 0.3 from the Cluster Infall Regions in the Sloan Digital Sky Survey and the Hectospec Cluster Survey to redshift z ∼ 0.42. Averaging over redshift, low-mass clusters with masses near 0.7 × 1014 M ⊙ roughly accrete 3 × 104 M ⊙ yr−1; more massive clusters with masses near 2.8 × 1014 M ⊙ roughly accrete 1 × 105 M ⊙ yr−1. Low- and high-mass clusters increase their MAR by approximately 46% and 84%, respectively, as the redshift increases from z in the range 0.17–0.29 to z in the range 0.34–0.42. The MARs at fixed redshift increase with mass and MARs at fixed mass increase with redshift in agreement with the ΛCDM cosmological model for hierarchical structure formation. We consider the extension of MAR measurements to z ∼ 1.
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Bhatiani, Saloni, Xinyu Dai, Rhiannon D. Griffin, Jenna M. Nugent, Christopher S. Kochanek und Joel N. Bregman. „Optical Confirmation of X-Ray-selected Galaxy Clusters from the Swift AGN and Cluster Survey with MDM and Pan-STARRS Data. III“. Astrophysical Journal Supplement Series 259, Nr. 1 (23.02.2022): 9. http://dx.doi.org/10.3847/1538-4365/ac3b59.
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Abstract To understand structure formation in the universe and impose stronger constraints on the cluster mass function and cosmological models, it is important to have large galaxy cluster catalogs. The Swift AGN and Cluster Survey is a serendipitous X-ray survey aimed at building a large statistically selected X-ray cluster catalog with 442 cluster candidates in its first release. Our initial SDSS follow-up study confirmed 50% of clusters in the Sloan Digital Sky Survey footprint as z < 0.5 clusters. Here we present further optical follow-up analysis of 248 (out of 442) cluster candidates from the Swift cluster catalog using multiband imaging from the MDM 2.4 m telescope and the Pan-STARRS survey. We report the optical confirmation of 55 clusters with >3σ galaxy overdensities and detectable red sequences in the color–magnitude space. The majority of these confirmed clusters have redshifts z < 0.6. The remaining candidates are potentially higher-redshift clusters that are excellent targets for infrared observations. We report the X-ray luminosity and the optical richness for these confirmed clusters. We also discuss the distinction between X-ray and optical observables for the detected and nondetected cluster candidates.
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Adami, C., P. Giles, E. Koulouridis, F. Pacaud, C. A. Caretta, M. Pierre, D. Eckert et al. „The XXL Survey“. Astronomy & Astrophysics 620 (20.11.2018): A5. http://dx.doi.org/10.1051/0004-6361/201731606.
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Context. In the currently debated context of using clusters of galaxies as cosmological probes, the need for well-defined cluster samples is critical. Aims. The XXL Survey has been specifically designed to provide a well characterised sample of some 500 X-ray detected clusters suitable for cosmological studies. The main goal of present article is to make public and describe the properties of the cluster catalogue in its present state, as well as of associated catalogues of more specific objects such as super-clusters and fossil groups. Methods. Following from the publication of the hundred brightest XXL clusters, we now release a sample containing 365 clusters in total, down to a flux of a few 10−15 erg s−1 cm−2 in the [0.5–2] keV band and in a 1′ aperture. This release contains the complete subset of clusters for which the selection function is well determined plus all X-ray clusters which are, to date, spectroscopically confirmed. In this paper, we give the details of the follow-up observations and explain the procedure adopted to validate the cluster spectroscopic redshifts. Considering the whole XXL cluster sample, we have provided two types of selection, both complete in a particular sense: one based on flux-morphology criteria, and an alternative based on the [0.5–2] keV flux within 1 arcmin of the cluster centre. We have also provided X-ray temperature measurements for 80% of the clusters having a flux larger than 9 × 10−15 erg s−1 cm−2. Results. Our cluster sample extends from z ~ 0 to z ~ 1.2, with one cluster at z ~ 2. Clusters were identified through a mean number of six spectroscopically confirmed cluster members. The largest number of confirmed spectroscopic members in a cluster is 41. Our updated luminosity function and luminosity–temperature relation are compatible with our previous determinations based on the 100 brightest clusters, but show smaller uncertainties. We also present an enlarged list of super-clusters and a sample of 18 possible fossil groups. Conclusions. This intermediate publication is the last before the final release of the complete XXL cluster catalogue when the ongoing C2 cluster spectroscopic follow-up is complete. It provides a unique inventory of medium-mass clusters over a 50 deg2 area out to z ~ 1.
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Gal-Yam, A., D. Maoz, K. Sharon, F. Prada, P. Guhathakurta und A. V. Filippenko. „Supernovae in Galaxy Clusters“. International Astronomical Union Colloquium 192 (2005): 367–71. http://dx.doi.org/10.1017/s025292110000943x.
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SummaryWe present the results of several surveys for supernovae (SNe) in galaxy clusters. SNe discovered in deep, archival HST images were used to measure the cluster SN Ia rate to z = 1. A search for SNe in nearby (0.06 ≤ z ≤ 0.2) Abell galaxy clusters yielded 15 SNe, 12 of which were spectroscopically confirmed. Of these, 7 are cluster SNe Ia, which we will use to measure the SN Ia rate in nearby clusters. This search has also discovered the first convincing examples of intergalactic SNe. We conclude with a brief description of ongoing and future cluster SN surveys.
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Sohn, Jubee, Margaret J. Geller, Ho Seong Hwang, Antonaldo Diaferio, Kenneth J. Rines und Yousuke Utsumi. „The HectoMAP Cluster Survey: Spectroscopically Identified Clusters and their Brightest Cluster Galaxies (BCGs)“. Astrophysical Journal 923, Nr. 2 (01.12.2021): 143. http://dx.doi.org/10.3847/1538-4357/ac29c3.
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Abstract We apply a friends-of-friends (FoF) algorithm to identify galaxy clusters and we use the catalog to explore the evolutionary synergy between brightest cluster galaxies (BCGs) and their host clusters. We base the cluster catalog on the dense HectoMAP redshift survey (2000 redshifts deg−2). The HectoMAP FoF catalog includes 346 clusters with 10 or more spectroscopic members within the range 0.05 < z < 0.55 and with a median z = 0.29. We list these clusters and their members. We also include central velocity dispersions (σ *,BCG) for the FoF cluster BCGs, a distinctive feature of the HectoMAP FoF catalog. HectoMAP clusters with higher galaxy number density (80 systems) are all genuine clusters with a strong concentration and a prominent BCG in Subaru/Hyper Suprime-Cam images. The phase-space diagrams show the expected elongation along the line of sight. Lower-density systems include some low reliability systems. We establish a connection between BCGs and their host clusters by demonstrating that σ *,BCG /σ cl decreases as a function of cluster velocity dispersion (σ cl), in contrast, numerical simulations predict a constant σ *,BCG/σ cl. Sets of clusters at two different redshifts show that BCG evolution in massive systems is slow over the redshift range z < 0.4. The data strongly suggest that minor mergers may play an important role in BCG evolution in clusters with σ cl ≳ 300 km s−1. For lower mass systems (σ cl < 300 km s−1), major mergers may play a significant role. The coordinated evolution of BCGs and their host clusters provides an interesting test of simulations in high-density regions of the universe.
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Strazzullo, V., M. Pannella, J. J. Mohr, A. Saro, M. L. N. Ashby, M. B. Bayliss, S. Bocquet et al. „Galaxy populations in the most distant SPT-SZ clusters“. Astronomy & Astrophysics 622 (Februar 2019): A117. http://dx.doi.org/10.1051/0004-6361/201833944.
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We present the first results from a galaxy population study in the highest redshift galaxy clusters identified in the 2500 deg2 South Pole Telescope Sunyaev Zel’dovich effect (SPT-SZ) survey, which is sensitive to M500 ≳ 3 × 1014 M⊙ clusters from z ∼ 0.2 out to the highest redshifts where such massive structures exist. The cluster selection is to first order independent of galaxy properties, making the SPT-SZ sample particularly well suited for cluster galaxy population studies. We carried out a four-band imaging campaign with the Hubble and Spitzer Space Telescopes of the five z ≳ 1.4, S/NSZE > 5 clusters, that are among the rarest most massive clusters known at this redshift. All five clusters show clear overdensities of red galaxies whose colors agree with the initial cluster redshift estimates, although one (SPT-CLJ0607–4448) shows a galaxy concentration much less prominent than the others. The highest redshift cluster in this sample, SPT-CLJ0459–4947 at z ∼ 1.72, is the most distant M500 > 1014 M⊙ cluster discovered thus far through its intracluster medium, and is one of only three known clusters in this mass range at z ≳ 1.7, regardless of selection. Based on UVJ-like photometric classification of quiescent and star-forming galaxies, we find that the quiescent fraction in the cluster central regions (r/r500 < 0.7) is higher than in the field at the same redshift, with corresponding environmental quenching efficiencies typically in the range ∼0.5 − 0.8 for stellar masses log(M/M⊙) > 10.85. We have explored the impact of emission from star formation on the selection of this sample, concluding that all five clusters studied here would still have been detected with S/NSZE> 5, even if they had the same quiescent fraction as measured in the field. Our results thus point towards an efficient suppression of star formation in the central regions of the most massive clusters, occurring already earlier than z ∼ 1.5.
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Sohn, Jubee, Margaret J. Geller, Mark Vogelsberger und Josh Borrow. „IllustrisTNG Snapshots for 10 Gyr of Dynamical Evolution of Brightest Cluster Galaxies and Their Host Clusters“. Astrophysical Journal 938, Nr. 1 (01.10.2022): 3. http://dx.doi.org/10.3847/1538-4357/ac8f23.
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Abstract We explore the redshift evolution of the dynamical properties of massive clusters and their brightest cluster galaxies (BCGs) at z < 2 based on the IllustrisTNG-300 simulation. We select 270 massive clusters with M 200 < 1014 M ⊙ at z = 0 and trace their progenitors based on merger trees. From 67 redshift snapshots covering z < 2, we compute the 3D subhalo velocity dispersion as a cluster velocity dispersion (σ cl). We also calculate the 3D stellar velocity dispersion of the BCGs (σ *,BCG). Both σ cl and σ *,BCG increase as the universe ages. The BCG velocity dispersion grows more slowly than the cluster velocity dispersion. Furthermore, the redshift evolution of the BCG velocity dispersion shows dramatic changes at some redshifts resulting from dynamical interaction with neighboring galaxies (major mergers). We show that σ *,BCG is comparable with σ cl at z > 1, offering an interesting observational test. The simulated redshift evolution of σ cl and σ *,BCG generally agrees with an observed cluster sample for z < 0.3, but with large scatter. Future large spectroscopic surveys reaching to high redshift will test the implications of the simulations for the mass evolution of both clusters and their BCGs.
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Varga, T. N., D. Gruen, S. Seitz, N. MacCrann, E. Sheldon, W. G. Hartley, A. Amon et al. „Synthetic galaxy clusters and observations based on Dark Energy Survey Year 3 Data“. Monthly Notices of the Royal Astronomical Society 509, Nr. 4 (18.11.2021): 4865–85. http://dx.doi.org/10.1093/mnras/stab3269.
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ABSTRACT We develop a novel data-driven method for generating synthetic optical observations of galaxy clusters. In cluster weak lensing, the interplay between analysis choices and systematic effects related to source galaxy selection, shape measurement, and photometric redshift estimation can be best characterized in end-to-end tests going from mock observations to recovered cluster masses. To create such test scenarios, we measure and model the photometric properties of galaxy clusters and their sky environments from the Dark Energy Survey Year 3 (DES Y3) data in two bins of cluster richness $\lambda \in [30; 45)$, $\lambda \in [45; 60)$ and three bins in cluster redshift ($z\in [0.3; 0.35)$, $z\in [0.45; 0.5)$ and $z\in [0.6; 0.65)$. Using deep-field imaging data, we extrapolate galaxy populations beyond the limiting magnitude of DES Y3 and calculate the properties of cluster member galaxies via statistical background subtraction. We construct mock galaxy clusters as random draws from a distribution function, and render mock clusters and line-of-sight catalogues into synthetic images in the same format as actual survey observations. Synthetic galaxy clusters are generated from real observational data, and thus are independent from the assumptions inherent to cosmological simulations. The recipe can be straightforwardly modified to incorporate extra information, and correct for survey incompleteness. New realizations of synthetic clusters can be created at minimal cost, which will allow future analyses to generate the large number of images needed to characterize systematic uncertainties in cluster mass measurements.
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Aguena, M., C. Benoist, L. N. da Costa, R. L. C. Ogando, J. Gschwend, H. B. Sampaio-Santos, M. Lima et al. „The WaZP galaxy cluster sample of the dark energy survey year 1“. Monthly Notices of the Royal Astronomical Society 502, Nr. 3 (16.02.2021): 4435–56. http://dx.doi.org/10.1093/mnras/stab264.
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ABSTRACT We present a new (2+1)D galaxy cluster finder based on photometric redshifts called Wavelet Z Photometric (WaZP) applied to DES first year (Y1A1) data. The results are compared to clusters detected by the South Pole Telescope (SPT) survey and the redMaPPer cluster finder, the latter based on the same photometric data. WaZP searches for clusters in wavelet-based density maps of galaxies selected in photometric redshift space without any assumption on the cluster galaxy populations. The comparison to other cluster samples was performed with a matching algorithm based on angular proximity and redshift difference of the clusters. It led to the development of a new approach to match two optical cluster samples, following an iterative approach to minimize incorrect associations. The WaZP cluster finder applied to DES Y1A1 galaxy survey (1511.13 deg2 up to mi = 23 mag) led to the detection of 60 547 galaxy clusters with redshifts 0.05 < z < 0.9 and richness Ngals ≥ 5. Considering the overlapping regions and redshift ranges between the DES Y1A1 and SPT cluster surveys, all sz based SPT clusters are recovered by the WaZP sample. The comparison between WaZP and redMaPPer cluster samples showed an excellent overall agreement for clusters with richness Ngals (λ for redMaPPer) greater than 25 (20), with 95 per cent recovery on both directions. Based on the cluster cross-match, we explore the relative fragmentation of the two cluster samples and investigate the possible signatures of unmatched clusters.
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Zenteno, A., D. Hernández-Lang, M. Klein, C. Vergara Cervantes, D. L. Hollowood, S. Bhargava, A. Palmese et al. „A joint SZ–X-ray–optical analysis of the dynamical state of 288 massive galaxy clusters“. Monthly Notices of the Royal Astronomical Society 495, Nr. 1 (04.05.2020): 705–25. http://dx.doi.org/10.1093/mnras/staa1157.
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ABSTRACT We use imaging from the first three years of the Dark Energy Survey to characterize the dynamical state of 288 galaxy clusters at 0.1 ≲ z ≲ 0.9 detected in the South Pole Telescope (SPT) Sunyaev–Zeldovich (SZ) effect survey (SPT-SZ). We examine spatial offsets between the position of the brightest cluster galaxy (BCG) and the centre of the gas distribution as traced by the SPT-SZ centroid and by the X-ray centroid/peak position from Chandra and XMM data. We show that the radial distribution of offsets provides no evidence that SPT SZ-selected cluster samples include a higher fraction of mergers than X-ray-selected cluster samples. We use the offsets to classify the dynamical state of the clusters, selecting the 43 most disturbed clusters, with half of those at z ≳ 0.5, a region seldom explored previously. We find that Schechter function fits to the galaxy population in disturbed clusters and relaxed clusters differ at z > 0.55 but not at lower redshifts. Disturbed clusters at z > 0.55 have steeper faint-end slopes and brighter characteristic magnitudes. Within the same redshift range, we find that the BCGs in relaxed clusters tend to be brighter than the BCGs in disturbed samples, while in agreement in the lower redshift bin. Possible explanations includes a higher merger rate, and a more efficient dynamical friction at high redshift. The red-sequence population is less affected by the cluster dynamical state than the general galaxy population.
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REPHAELI, YOEL, und SHARON SADEH. „S-Z POWER SPECTRA“. Modern Physics Letters A 23, Nr. 17n20 (28.06.2008): 1498–505. http://dx.doi.org/10.1142/s0217732308027886.
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There is some observational evidence for earlier evolution of clusters of galaxies than predicted in the standard ΛCDM model with a Gaussian primordial density fluctuation field, and a low value for the mass variance parameter (σ8). Particularly difficult in this model is the interpretation of possible excess CMB anisotropy on cluster scales as due to the Sunyaev-Zeldovich (S-Z) effect. We have calculated S-Z power spectra in the standard model, and in two alternative models which predict higher cluster abundance - a model with non-Gaussian PDF, and an early dark energy model. As anticipated, the levels of S-Z power in the latter two models are significantly higher than in the standard model, and in good agreement with current measurements of CMB anisotropy at high multipole values. Our results provide a sufficient basis for testing the viability of the three models by future high quality measurements of cluster abundance and the anisotropy induced by the S-Z effect.
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Sarron, F., N. Martinet, F. Durret und C. Adami. „Evolution of the cluster optical galaxy luminosity function in the CFHTLS: breaking the degeneracy between mass and redshift“. Astronomy & Astrophysics 613 (Mai 2018): A67. http://dx.doi.org/10.1051/0004-6361/201731981.
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Obtaining large samples of galaxy clusters is important for cosmology: cluster counts as a function of redshift and mass can constrain the parameters of our Universe. They are also useful in order to understand the formation and evolution of clusters. We develop an improved version of the Adami & MAzure Cluster FInder (AMACFI), now the Adami, MAzure & Sarron Cluster FInder (AMASCFI), and apply it to the 154 deg2 of the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS) to obtain a large catalogue of 1371 cluster candidates with mass M200 > 1014 M⊙ and redshift z ≤ 0.7. We derive the selection function of the algorithm from the Millennium simulation, and cluster masses from a richness–mass scaling relation built from matching our candidates with X-ray detections. We study the evolution of these clusters with mass and redshift by computing the i′-band galaxy luminosity functions (GLFs) for the early-type (ETGs) and late-type galaxies (LTGs). This sample is 90% pure and 70% complete, and therefore our results are representative of a large fraction of the cluster population in these redshift and mass ranges. We find an increase in both the ETG and LTG faint populations with decreasing redshift (with Schechter slopes αETG = −0.65 ± 0.03 and αLTG = −0.95 ± 0.04 at z = 0.6, and αETG = −0.79 ± 0.02 and αLTG = −1.26 ± 0.03 at z = 0.2) and also a decrease in the LTG (but not the ETG) bright end. Our large sample allows us to break the degeneracy between mass and redshift, finding that the redshift evolution is more pronounced in high-mass clusters, but that there is no significant dependence of the faint end on mass for a given redshift. These results show that the cluster red sequence is mainly formed at redshift z > 0.7, and that faint ETGs continue to enrich the red sequence through quenching of brighter LTGs at z ≤ 0.7. The efficiency of this quenching is higher in large-mass clusters, while the accretion rate of faint LTGs is lower as the more massive clusters have already emptied most of their environment at higher redshifts.
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Koulouridis, E., N. Clerc, T. Sadibekova, M. Chira, E. Drigga, L. Faccioli, J. P. Le Fèvre et al. „The X-CLASS survey: A catalogue of 1646 X-ray-selected galaxy clusters up to z ∼ 1.5“. Astronomy & Astrophysics 652 (August 2021): A12. http://dx.doi.org/10.1051/0004-6361/202140566.
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Context. Cosmological probes based on galaxy clusters rely on cluster number counts and large-scale structure information. X-ray cluster surveys are well suited for this purpose because they are far less affected by projection effects than optical surveys, and cluster properties can be predicted with good accuracy. Aims. The XMM Cluster Archive Super Survey, X-CLASS, is a serendipitous search of X-ray-detected galaxy clusters in 4176 XMM-Newton archival observations until August 2015. All observations are clipped to exposure times of 10 and 20 ks to obtain uniformity, and they span ∼269 deg2 across the high-Galactic latitude sky (|b| > 20°). The main goal of the survey is the compilation of a well-selected cluster sample suitable for cosmological analyses. Methods. We describe the detection algorithm, the visual inspection, the verification process, and the redshift validation of the cluster sample, as well as the cluster selection function computed by simulations. We also present the various metadata that are released with the catalogue, along with two different count-rate measurements, an automatic one provided by the pipeline, and a more detailed and accurate interactive measurement. Furthermore, we provide the redshifts of 124 clusters obtained with a dedicated multi-object spectroscopic follow-up programme. Results. With this publication, we release the new X-CLASS catalogue of 1646 well-selected X-ray-detected clusters over a wide sky area, along with their selection function. The sample spans a wide redshift range, from the local Universe up to z ∼ 1.5, with 982 spectroscopically confirmed clusters, and over 70 clusters above z = 0.8. The redshift distribution peaks at z ∼ 0.1, while if we remove the pointed observations it peaks at z ∼ 0.3. Because of its homogeneous selection and thorough verification, the cluster sample can be used for cosmological analyses, but also as a test-bed for the upcoming eROSITA observations and other current and future large-area cluster surveys. It is the first time that such a catalogue is made available to the community via an interactive database which gives access to a wealth of supplementary information, images, and data.
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Zhen, Junfeng, Yuanyuan Yang, Weiwei Zhang und Qingfeng Zhu. „Formation and photochemistry of covalently bonded large functional PAH clusters“. Astronomy & Astrophysics 628 (August 2019): A57. http://dx.doi.org/10.1051/0004-6361/201935824.
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Polycyclic aromatic hydrocarbon (PAH) molecules belong to a large and diverse chemical family in the interstellar medium (ISM). We study the formation and photochemistry of covalently bonded large functional PAH clusters, dicoronylene (DC, C48H20)/9-vinylanthracene (C16H12) and dicoronylene/9-methylanthracene (C15H12) cluster cations, in the gas phase, and we offer an approach to the evolution of different types of large (covalently bonded) PAH clusters in the ISM. The experiments, which we combined with a quadrupole ion trap and time-of-flight mass spectrometry, show that large functional PAH cluster cations can form by gas-phase condensation through molecular-ion reactions. One group of functional PAH cluster cations contain the vinyl group (−CHCH2), that is, from C16H12DDC+ (e.g., C16H12C48H19+, m/z = 799) to (C16H12)2DDC+ (e.g., (C16H12)2C48H18+, m/z = 1002). The other group of functional PAH cluster cations contain the methyl group (−CH3), that is, from C15H12DDC+ (e.g., C15H12C48H19+, m/z = 787) to (C15H12)2DDC+ (e.g., (C15H12)2C48H18+, m/z = 990). With laser irradiation, the DC/9-vinylanthracene and DC/9-methylanthracene cluster cations show a very complicated dissociation process (e.g., dehydrogenation, −CH3 or −CHCH2 unit losses). We investigate the structure of newly formed PAH cluster cations, the bond energy, and the photodissociation energy for these reaction pathways with quantumchemical calculations. The obtained results provide a general molecular growth route toward large PAH cluster cations (e.g., functional PAH clusters) in a bottom-up formation process and the insight of the functional group (e.g., vinyl, −C2H3 and methyl, −CH3) effect on their evolutionary behavior. In addition, the studies of DC/9-vinylanthracene and DC/9-methylanthracene clusters (94–123 atoms, ∼2 nm in size) also provide a possible way of interpreting the formation processes of nanometer-sized grains in the ISM, especially when functional PAHs are included.
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Maoz, D., und A. Gal-Yam. „Constraints on SN Ia Progenitors and ICM Enrichment from Field and Cluster SN Rates“. International Astronomical Union Colloquium 192 (2005): 561–65. http://dx.doi.org/10.1017/s0252921100009660.
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SummaryThe iron mass in galaxy clusters is about 6 times larger than could have been produced by core-collapse SNe, assuming the stars in cluster galaxies formed with a standard IMF. Type-Ia SNe have been proposed as the alternative dominant iron source. We use our HST measurements of the cluster SN-Ia rate at high redshift to study the cluster iron enrichment scenario. The measurements can constrain the star-formation epoch and the SN-Ia progenitor models via the mean delay time between the formation of a stellar population and the explosion of some of its members as SNe-Ia. The low observed rate of cluster SNe-Ia at z ~ 1 pushes back the star-formation epoch in clusters to z > 2, and implies a short delay time. We also show a related analysis for high-z field SNe which implies, under some conditions, a long SN-Ia delay time. Thus, cluster enrichment by core-collapse SNe from a top-heavy IMF may remain the only viable option.
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Toba, Yoshiki, Aoi Hashiguchi, Naomi Ota, Masamune Oguri, Nobuhiro Okabe, Yoshihiro Ueda, Masatoshi Imanishi et al. „Active Galactic Nucleus Properties of ∼1 Million Member Galaxies of Galaxy Groups and Clusters at z < 1.4 Based on the Subaru Hyper Suprime-Cam Survey“. Astrophysical Journal 967, Nr. 1 (01.05.2024): 65. http://dx.doi.org/10.3847/1538-4357/ad32c6.
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Abstract Herein, we present the statistical properties of active galactic nuclei (AGNs) for approximately 1 million member galaxies of galaxy groups and clusters with 0.1 < cluster redshift (z cl) < 1.4 selected using the Subaru Hyper Suprime-Cam, the so-called CAMIRA clusters. In this research, we focused on the AGN power fraction (f AGN), which is defined as the proportion of the contribution of AGNs to the total infrared (IR) luminosity, L IR (AGN)/L IR, and examined how f AGN depends on (i) z cl and (ii) the distance from the cluster center. We compiled multiwavelength data using the ultraviolet–mid-IR range. Moreover, we performed spectral energy distribution fits to determine f AGN using the CIGALE code with the SKIRTOR AGN model. We found that (i) the value of f AGN in the CAMIRA clusters is positively correlated with z cl, with the correlation slope being steeper than that for field galaxies, and (ii) f AGN exhibits a high value at the cluster outskirts. These results indicate that the emergence of the AGN population depends on the redshift and environment and that galaxy groups and clusters at high redshifts are important in AGN evolution. Additionally, we demonstrated that cluster–cluster mergers may enhance AGN activity at the outskirts of particularly massive galaxy clusters. Our findings are consistent with a related study on the CAMIRA clusters that was based on the AGN number fraction.
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Negri, Andrea, Claudio Dalla Vecchia, Alfonso Aguerri, Yannick Bahé, David Barnes und Scott Kay. „The evolution of the luminosity function faint end of cluster galaxies in the Cluster-EAGLE simulation“. Proceedings of the International Astronomical Union 14, S344 (August 2018): 495–97. http://dx.doi.org/10.1017/s1743921318006233.
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AbstractIn the last decade observations have been able to probe the evolution of the galaxy luminosity function, in particular showing a variation of its faint-end with redshift. We employ the data of the Cluster-EAGLE project, a set of cosmological, hydrodynamical zoom-in simulations of 30 galaxy clusters, to study the evolution of the galaxy luminostity functions in clusters with redshift. We compile a catalogue of simulated galaxies’ luminosities in the SDSS bands using the E-MILES spectra database, and taking into account dust attenuation. Stacked luminosity functions present little evolution with redshift of the faint-end slope from z=3.5 to z=0, regardless of the cluster mass.
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Mantz, A. B., Z. Abdulla, S. W. Allen, J. E. Carlstrom, C. H. A. Logan, D. P. Marrone, B. J. Maughan, J. Willis, F. Pacaud und M. Pierre. „The XXL Survey“. Astronomy & Astrophysics 620 (20.11.2018): A2. http://dx.doi.org/10.1051/0004-6361/201630096.
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We present results from a 100 ks XMM-Newton observation of galaxy cluster XLSSC 122, the first massive cluster discovered through its X-ray emission at z ≈ 2. The data provide the first precise constraints on the bulk thermodynamic properties of such a distant cluster, as well as an X-ray spectroscopic confirmation of its redshift. We measure an average temperature of kT = 5.0 ± 0.7 keV; a metallicity with respect to solar of Z/Z⊙ = 0.33−0.17+0.19, consistent with lower-redshift clusters; and a redshift of z = 1.99+0.07-0.06 , consistent with the earlier photo-z estimate. The measured gas density profile leads to a mass estimate at r500 of M500 = (6.3 ± 1.5) × 1013 M⊙. From CARMA 30 GHz data, we measure the spherically integrated Compton parameter within r500 to be Y 500 = (3.6 ± 0.4) × 10−12. We compare the measured properties of XLSSC 122 to lower-redshift cluster samples, and find good agreement when assuming the simplest (self-similar) form for the evolution of cluster scaling relations. While a single cluster provides limited information, this result suggests that the evolution of the intracluster medium in the most massive, well-developed clusters is remarkably simple, even out to the highest redshifts where they have been found. At the same time, our data reaffirm the previously reported spatial offset between the centres of the X-ray and SZ signals for XLSSC 122, suggesting a disturbed configuration. Higher spatial resolution data could thus provide greater insights into the internal dynamics of this system.
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Strazzullo, V., E. Daddi, R. Gobat und M. Onodera. „Cluster galaxies 10 billion years ago“. Proceedings of the International Astronomical Union 8, S295 (August 2012): 60. http://dx.doi.org/10.1017/s1743921313004304.
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AbstractCl J1449+0856 is a spectroscopically confirmed galaxy cluster at z ~ 2. The detection of a faint, extended X-ray emission, suggestive of an already evolved, partially relaxed structure, puts this system among the most distant “established” clusters rather than in the realm of z≳2 proto-clusters. This gives us a chance of studying galaxies in an evolved overdense environment very close to their formation epoch, and in particular to trace the evolution of early-type galaxies in clusters back to ten billion years ago.
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Gupta, N., M. Pannella, J. J. Mohr, M. Klein, E. S. Rykoff, J. Annis, S. Avila et al. „Constraining radio mode feedback in galaxy clusters with the cluster radio AGNs properties to z ∼ 1“. Monthly Notices of the Royal Astronomical Society 494, Nr. 2 (03.04.2020): 1705–23. http://dx.doi.org/10.1093/mnras/staa832.
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ABSTRACT We study the properties of the Sydney University Molonglo Sky Survey (SUMSS) 843 MHz radio active galactic nuclei (AGNs) population in galaxy clusters from two large catalogues created using the Dark Energy Survey (DES): ∼11 800 optically selected RM-Y3 and ∼1000 X-ray selected MARD-Y3 clusters. We show that cluster radio loud AGNs are highly concentrated around cluster centres to $z$ ∼ 1. We measure the halo occupation number for cluster radio AGNs above a threshold luminosity, finding that the number of radio AGNs per cluster increases with cluster halo mass as N ∝ M1.2 ± 0.1 (N ∝ M0.68 ± 0.34) for the RM-Y3 (MARD-Y3) sample. Together, these results indicate that radio mode feedback is favoured in more massive galaxy clusters. Using optical counterparts for these sources, we demonstrate weak redshift evolution in the host broad-band colours and the radio luminosity at fixed host galaxy stellar mass. We use the redshift evolution in radio luminosity to break the degeneracy between density and luminosity evolution scenarios in the redshift trend of the radio AGNs luminosity function (LF). The LF exhibits a redshift trend of the form (1 + $z$)γ in density and luminosity, respectively, of γD = 3.0 ± 0.4 and γP = 0.21 ± 0.15 in the RM-Y3 sample, and γD = 2.6 ± 0.7 and γP = 0.31 ± 0.15 in MARD-Y3. We discuss the physical drivers of radio mode feedback in cluster AGNs, and we use the cluster radio galaxy LF to estimate the average radio-mode feedback energy as a function of cluster mass and redshift and compare it to the core (<0.1R500) X-ray radiative losses for clusters at $z$ < 1.
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Decker, Bandon, Mark Brodwin, Ripon Saha, Thomas Connor, Peter R. M. Eisenhardt, Anthony H. Gonzalez, Emily Moravec et al. „The Massive and Distant Clusters of WISE Survey. XI. Stellar Mass Fractions and Luminosity Functions of MaDCoWS Clusters at z ∼ 1“. Astrophysical Journal 936, Nr. 1 (31.08.2022): 71. http://dx.doi.org/10.3847/1538-4357/ac85e5.
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Abstract We present stellar mass fractions and composite luminosity functions (LFs) for a sample of 12 clusters from the Massive and Distant Clusters of WISE Survey (MaDCoWS) in the redshift range 0.951 ≤ z ≤ 1.43. Using spectral energy distribution fitting of optical and deep mid-infrared photometry, we establish the membership of objects along the lines of sight to these clusters and calculate the stellar masses of member galaxies. This allows us to calculate the stellar mass of the clusters much more precisely than in previous works. We find stellar mass fractions for these clusters largely consistent with previous works, and an apparent negative correlation with total cluster mass. We measure a composite 3.6 μm LF down to m* + 2.5 for all 12 clusters. Fitting a Schechter function to the LF, we find a characteristic 3.6 μm magnitude of m* = 19.83 ± 0.12 and faint-end slope of α = −0.81 ± 0.10 for the full sample at a mean redshift of z ¯ = 1.18 . We also divide the clusters into high- and low-redshift bins at z ¯ = 1.29 and z ¯ = 1.06 , respectively, and measure a composite LF for each bin. We see a small, but statistically significant, evolution in m* and α—consistent with passive evolution—when we study the joint fit to the two parameters, which is probing the evolution of faint cluster galaxies at z ∼ 1. This highlights the importance of deep IR data in studying the evolution of cluster galaxy populations at high redshift.
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Ando, Makoto, Kazuhiro Shimasaku und Rieko Momose. „A systematic search for galaxy proto-cluster cores at z ∼ 2“. Proceedings of the International Astronomical Union 15, S359 (März 2020): 166–67. http://dx.doi.org/10.1017/s1743921320001933.
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AbstractA proto-cluster core is the most massive dark matter halo (DMH) in a given proto-cluster. To reveal the galaxy formation in core regions, we search for proto-cluster cores at z ˜ 2 in ˜1.5deg2 of the COSMOS field. Using pairs of massive galaxies (log (M*/Mʘ) ≥ 11) as tracers of cores, we find 75 candidate cores. A clustering analysis and the extended Press-Schechter model show that their descendant mass at z = 0 is consistent with Fornax-like or Virgo-like clusters. Moreover, using the IllustrisTNG simulation, we confirm that pairs of massive galaxies are good tracers of DMHs massive enough to be regarded as proto-cluster cores. We then derive the stellar mass function and the quiescent fraction for member galaxies of the 75 candidate cores. We find that stellar mass assembly and quenching are accelerated as early as z ˜ 2 in proto-cluster cores.
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Poleshchuk, Olga. „Clustering Z-information based on a system of fuzzy reference requirements“. E3S Web of Conferences 420 (2023): 06022. http://dx.doi.org/10.1051/e3sconf/202342006022.
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The paper develops a clustering model of multi-criteria object evaluations, taking into account the reliability of the results obtained. Clustering is based on a system of fuzzy reference requirements about the importance of the evaluated characteristics of objects for each of the clusters. Object evaluations are formalized on the basis of linguistic Z-numbers, both fuzzy numbers of which are the values of linguistic variables. Information for each object and each cluster is presented as a set of pairs (according to the number of characteristics) consisting of a fuzzy number (importance of a characteristic for the corresponding cluster) and a Z-number (an evaluation of the object within this characteristic and its reliability). Using this information, fuzzy ratings are determined for each object in accordance with fuzzy reference requirements for each cluster. Fuzzy ratings of objects, defined as fuzzy numbers, reflect the compliance of multi-criteria ratings of objects with fuzzy reference requirements. The comparative analysis of fuzzy ratings of all objects within one cluster proposed in the paper makes it possible to identify the best representative (or best representatives) of the cluster under consideration and determine the degree of belonging of the remaining objects to this cluster. The analysis is carried out for all clusters. A numerical example is given, which shows the effectiveness of the developed method under Z-information.
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Burke, Claire, Chris Collins, John Stott und Matt Hilton. „Evolution in cluster cores since z ~ 1“. Proceedings of the International Astronomical Union 8, S295 (August 2012): 172–73. http://dx.doi.org/10.1017/s1743921313004602.
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AbstractA large fraction of the stellar mass in galaxy clusters is thought to be contained in the diffuse low surface brightness intracluster light (ICL). Being bound to the gravitational potential of the cluster rather than any individual galaxy, the ICL contains much information about the evolution of its host cluster and the interactions between the galaxies within. However due its low surface brightness it is notoriously difficult to study. We present the first detection and measurement of the flux contained in the ICL at z ~ 1. We find that the fraction of the total cluster light contained in the ICL may have increased by factors of 2–4 since z ~ 1, in contrast to recent findings for the lack of mass and scale size evolution found for brightest cluster galaxies. Our results suggest that late time build-up in cluster cores may occur more through stripping than merging and we discuss the implications of our results for hierarchical simulations.
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Pandhita S, Gea, und Sri Sutarni. „Gambaran Quantitative Electroencephalography (QEEG) Anak Laki-laki Penderita Attention-Deficit Disorder (ADD)“. Sanus Medical Journal 2, Nr. 1 (28.02.2021): 16–21. http://dx.doi.org/10.22236/sanus.v1i1.6610.
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Background. The Diagnostic and Statistical Manual of Mental Disorders (DSM) grouping the types of ADD is based on the clinical symptoms of neurobehavioral disorders, regardless of the possible underlying etiology. This means that the same ADD type group may have a different etiology of functional brain disorders. Meanwhile, QEEG has been known to describe the possible etiology that underlies an ADD event. This study aims to identify differences in QEEG features in the same ADD type group.
Methods. Subjects consisted of 40 boys with ADD. QEEG was recorded from 21 sites, and Fourier transformed to provide estimates for relative power in the delta, theta, alpha, and beta bands in the frontotemporal and central regions. These data were converted to Z-scores based on the normal value data; afterward, they were subjected to cluster analysis. Independent sample t-tests were used to determine how the total ADD group and the ADD cluster subgroups differed from the normal value.
Results. The total ADD group had increased relative delta (Z-score-frontotemporal region = 3,26 ± 1,59; Z-score-central region = 4,04 ± 1,71), decreased relative alpha (Z-score-frontotemporal region = -2,78 ± 1,29; Z-score-central region = -2,86 ± 1,36), decreased relative beta (Z-score-frontotemporal region = -5,33 ± 1,61; Z-score-central region = -6,19 ± 1,86), increased rasio teta/alpha (Z-score-frontotemporal region = 2,806 ± 1,41; Z-score-central region = 2,59 ± 1,26), and increased rasio teta/beta (Z-score-frontotemporal region = 4,36 ± 1,69; Z-score-central region = 4,94 ± 1,46). Two distinct QEEG clusters subgroups were found. The first cluster was characterized by increased central relative delta (Z-score-central region = 3,02 ± 1,17), decreased relative beta (Z-score-frontotemporal region = -4,29 ± 0,73; Z-score-central region = -5,06 ± 1,19) and increased rasio teta/beta (Z-score-frontotemporal region = 3,83 ± 1,91; Z-score-central region = 4,94 ± 1,96). The second cluster was characterized by increased relative delta (Z-score-frontotemporal region = 4,71 ± 1,02; Z-score-central region = 5,72 ± 0,98), decreased relative alpha (Z-score-frontotemporal region = -3,92 ± 1,12; Z-score-central region = -4,24 ± 0,69), decreased relative beta (Z-score-frontotemporal region = -7,08 ± 1,06; Z-score-central region = -8,09 ± 0,99), increased rasio teta/alpha (Z-score-frontotemporal region = 3,08 ± 1,04; Z-score-central region = 2,86 ± 1,02), and increased rasio teta/beta (Z-score-frontotemporal region = 5,23 ± 1,16; Z-score-central region = 5,71 ± 1,35)
Conclusions. These results indicate that boys with ADD do not constitute a homogenous group in QEEG profile terms. Two distinct QEEG clusters were found. The first cluster was typified by a cortically hypoaroused, while the second cluster was typified by a maturational-lag in central nervous system development. This difference in possible etiology may have implications for studies of the utility of QEEG in the diagnosis of ADD and the differences in therapeutic response between the two groups.
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Zaffanello, Marco, Angelo Pietrobelli, David Gozal, Luana Nosetti, Stefania La Grutta, Giovanna Cilluffo, Giuliana Ferrante, Michele Piazza und Giorgio Piacentini. „Cluster Analysis of Home Polygraphic Recordings in Symptomatic Habitually-Snoring Children: A Precision Medicine Perspective“. Journal of Clinical Medicine 11, Nr. 19 (09.10.2022): 5960. http://dx.doi.org/10.3390/jcm11195960.
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(1) Background: Sleep-disordered breathing (SDB) is a frequent problem in children. Cluster analyses offer the possibility of identifying homogeneous groups within a large clinical database. The application of cluster analysis to anthropometric and polysomnographic measures in snoring children would enable the detection of distinctive clinically-relevant phenotypes; (2) Methods: We retrospectively collected the results of nocturnal home-based cardiorespiratory polygraphic recordings and anthropometric measurements in 326 habitually-snoring otherwise healthy children. K-medoids clustering was applied to standardized respiratory and anthropometric measures, followed by Silhouette-based statistics. Respiratory Disturbance Index (RDI) and oxygen desaturation index (≤3%) were included in determining the optimal number of clusters; (3) Results: Mean age of subjects was 8.1 ± 4.1 years, and 57% were males. Cluster analyses uncovered an optimal number of three clusters. Cluster 1 comprised 59.5% of the cohort (mean age 8.69 ± 4.14 years) with a mean RDI of 3.71 ± 3.23 events/hour of estimated sleep (e/ehSleep). Cluster 2 included 28.5% of the children (mean age 6.92 ± 3.43 years) with an RDI of 6.38 ± 3.92 e/ehSleep. Cluster 3 included 12% of the cohort (mean age 7.58 ± 4.73 years) with a mean RDI of 25.5 ± 19.4 e/ehSleep. Weight z-score was significantly lower in cluster 3 [−0.14 ± 1.65] than in cluster 2 [0.86 ± 1.78; p = 0.015] and cluster 1 [1.04 ± 1.78; p = 0.002]. Similar findings emerged for BMI z scores. However, the height z-score was not significantly different among the 3 clusters; (4) Conclusions: Cluster analysis of children who are symptomatic habitual snorers and are referred for clinical polygraphic evaluation identified three major clusters that differed in age, RDI, and anthropometric measures. An increased number of children in the cluster with the highest RDI had reduced body weight. We propose that the implementation of these approaches to a multicenter-derived database of home-based polygraphic recordings may enable the delineation of objective unbiased severity categories of pediatric SDB. Our findings could be useful for clinical implementation, formulation of therapeutic decision guidelines, clinical management, prevision of complications, and long-term follow-up.
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Williams, Christina C., Stacey Alberts, Justin S. Spilker, Allison G. Noble, Mauro Stefanon, Christopher N. A. Willmer, Rachel Bezanson, Desika Narayanan und Katherine E. Whitaker. „ALMA Measures Molecular Gas Reservoirs Comparable to Field Galaxies in a Low-mass Galaxy Cluster at z = 1.3“. Astrophysical Journal 929, Nr. 1 (01.04.2022): 35. http://dx.doi.org/10.3847/1538-4357/ac58fa.
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Abstract We report the serendipitous discovery of an overdensity of CO emitters in an X-ray-identified cluster (Log10 M halo/M ⊙ ∼ 13.6 at z = 1.3188) using ALMA. We present spectroscopic confirmation of six new cluster members exhibiting CO(2–1) emission, adding to two existing optical/IR spectroscopic members undetected in CO. This is the lowest-mass cluster to date at z > 1 with molecular gas measurements, bridging the observational gap between galaxies in the more extreme, well-studied clusters (Log10 M halo/M ⊙ ≳ 14) and those in group or field environments at cosmic noon. The CO sources are concentrated on the sky (within ∼1 arcmin diameter) and phase space analysis indicates the gas resides in galaxies already within the cluster environment. We find that CO sources sit in similar phase space as CO-rich galaxies in more massive clusters at similar redshifts (have similar accretion histories) while maintaining field-like molecular gas reservoirs, compared to scaling relations. This work presents the deepest CO survey to date in a galaxy cluster at z > 1, uncovering gas reservoirs down to M H 2 > 1.6 × 10 10 M ⊙ (5σ at 50% primary beam). Our deep limits rule out the presence of gas content in excess of the field scaling relations; however, combined with literature CO detections, cluster gas fractions in general appear systematically high, on the upper envelope or above the field. This study is the first demonstration that low-mass clusters at z ∼ 1–2 can host overdensities of CO emitters with surviving gas reservoirs, in line with the prediction that quenching is delayed after first infall while galaxies consume the gas bound to the disk.
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Muñoz, Roberto P., L. F. Barrientos, B. P. Koester, D. G. Gilbank, M. D. Gladders und H. K. C. Yee. „The growth of the red-sequence in clusters since ≃1“. Proceedings of the International Astronomical Union 5, H15 (November 2009): 88. http://dx.doi.org/10.1017/s1743921310008410.
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AbstractWe use deep nIR imaging of 15 galaxy clusters at z ≃ 1 to study the build-up of the red-sequence in rich clusters since the Universe was half its present age. We measured, for the first time, the luminous-to-faint ratio of red-sequence galaxies at z=1 from a large ensemble of clusters, and found an increase of 100% in the ratio of luminous-to-faint red-sequence galaxies from z=0.45 to 1.0. The measured change in this ratio as function of redshift is well-reproduced by a simple evolutionary model developed in this work, that consists in an early truncation of the star formation for bright cluster galaxies and a delayed truncation for faint cluster galaxies.
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Beyoro-Amado, Zeleke, Mirjana Pović, Miguel Sánchez-Portal, Solomon Belay Tessema und Tilahun Getachew-Woreta. „Galaxy evolution studies in clusters: the case of Cl0024 + 1652 cluster galaxies at z ∼ 0.4“. Proceedings of the International Astronomical Union 15, S356 (Oktober 2019): 163–68. http://dx.doi.org/10.1017/s174392132000280x.
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AbstractStudying the transformation of cluster galaxies contributes a lot to have a clear picture of evolution of the universe. Towards that we are studying different properties (morphology, star formation, AGN contribution and metallicity) of galaxies in clusters up to z ∼ 1.0 taking three different clusters: ZwCl0024 + 1652 at z ∼ 0.4, RXJ1257 + 4738 at z ∼ 0.9 and Virgo at z ∼ 0.0038. For ZwCl0024 + 1652 and RXJ1257 + 4738 clusters we used tunable filters data from GLACE survey taken with GTC 10.4 m telescope and other public data, while for Virgo we used public data. We did the morphological classification of 180 galaxies in ZwCl0024 + 1652 using galSVM, where 54 % and 46 % of galaxies were classified as early-type (ET) and late-type (LT) respectively. We did a comparison between the three clusters within the clustercentric distance of 1 Mpc and found that ET proportion (decreasing with redshift) dominates over the LT (increasing with redshift) throughout. We finalized the data reduction for ZwCl0024 + 1652 cluster and identified 46 [OIII] and 73 Hβ emission lines. For this cluster we have classified 22 emission line galaxies (ELGs) using BPT-NII diagnostic diagram resulting with 14 composite, 1 AGN and 7 star forming (SF) galaxies. We are using these results, together with the public data, for further analysis of the variations of properties in relation to redshift within z < 1.0.
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Faisst, Andreas L., Ranga Ram Chary, Gabriel Brammer und Sune Toft. „What Are Those Tiny Things? A First Study of Compact Star Clusters in the SMACS0723 Field with JWST“. Astrophysical Journal Letters 941, Nr. 1 (01.12.2022): L11. http://dx.doi.org/10.3847/2041-8213/aca1bf.
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Abstract We use the unprecedented resolution and depth of the JWST NIRCam Early Release Observations at 1–5 μm to study the stellar mass, age, and metallicity of compact star clusters in the neighborhood of the host galaxies in the SMACS J0723.3–7327 galaxy cluster field at z = 0.39. The measured colors of these star clusters show a similar distribution as quiescent galaxies at the same redshift, but are >3 mag fainter than the current depths of wide-field galaxy survey. The star clusters are unresolved in the NIRCam/F150W data suggesting sizes smaller than 50 pc. This is significantly smaller than star-forming clumps or dwarf galaxies in local galaxies. From fitting their photometry with simple stellar population (SSP) models, we find stellar metallicities consistent with 0.2–0.3 Z ⊙ and ages of 1.5 − 0.5 + 0.5 Gyr . We rule out metallicities <0.2 Z ⊙ and solar/supersolar at 4σ significance. Assuming mass-to-light ratios obtained from the best-fit SSP, we estimate stellar masses of 2.4 − 1.5 + 3.0 × 10 6 M ⊙ . These are between average masses of local globular clusters and dwarf galaxies. Our analysis suggests middle-aged globular cluster with relatively recent formation times at z = 0.5–0.7, which could have been subsequently stripped away from their host galaxies due to interactions in the cluster environment or formed in cold flows onto the cluster core. However, we cannot rule out these objects being compact cores of stripped dwarf galaxies.
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Chuang, Yung-Kun, Szu-Hsueh Lai, Jung-Lee Lin und Chung-Hsuan Chen. „Biomolecular Clusters Distribution up to Mega Dalton Region Using MALDI-Quadrupole Ion Trap Mass Spectrometer“. International Journal of Molecular Sciences 19, Nr. 9 (17.09.2018): 2789. http://dx.doi.org/10.3390/ijms19092789.
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We present the first report on complete cluster distributions of cytochrome c (molecular weight of 12.4 kDa) and bovine serum albumin ((BSA), molecular weight of 66.4 kDa) with mass-to-charge ratio (m/z) reaching 350,000 and 1,400,000, respectively, by matrix-assisted laser desorption/ionization (MALDI). Large cluster distributions of the analytes were measured by our homemade frequency-scanned quadrupole ion trap (QIT) mass spectrometer with a charge detector. To our knowledge, we report the highest m/z clusters of these two biomolecules. The quantitative results indicate that large clusters ions of cytochrome c and BSA follow the power law (r2 > 0.99) with cluster size distribution, which provides experimental evidence for the laser ablation studies of MALDI.
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Maier, C., M. Hayashi, B. L. Ziegler und T. Kodama. „Cluster induced quenching of galaxies in the massive cluster XMMXCS J2215.9−1738 at z ∼ 1.5 traced by enhanced metallicities inside half R200“. Astronomy & Astrophysics 626 (Juni 2019): A14. http://dx.doi.org/10.1051/0004-6361/201935522.
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Aims. Cluster environments at z < 0.5 were found to increase the gas metallicities of galaxies which enter inner regions of the clusters where the density of the intracluster medium is high enough to remove their hot halo gas by ram-pressure stripping effects and to stop the inflow of pristine gas. To extend these studies to z > 1, the most massive clusters known at these redshifts are the sites where these environmental effects should be more pronounced and more easily observed with present day telescopes. Methods. We explore the massive cluster XMMXCS J2215.9−1738 at z ∼ 1.5 with KMOS spectroscopy of Hα and [N II] λ 6584 covering a region that corresponds to about one virial radius. Using published spectroscopic redshifts of 108 galaxies in and around the cluster we computed the location of galaxies in the projected velocity-versus-position phase-space to separate our cluster sample into a virialized region of objects accreted longer ago (roughly inside half R200) and a region of infalling galaxies. We measured oxygen abundances for ten cluster galaxies with detected [N II] λ 6584 lines in the individual galaxy spectra and compared the mass–metallicity relation of the galaxies inside half R200 with the infalling galaxies and a field sample at similar redshifts. Results. We find that the oxygen abundances of individual z ∼ 1.5 star-forming cluster galaxies inside half R200 are comparable, at the respective stellar mass, to the higher local SDSS metallicity values. We compare our measurements with a field galaxy sample from the KMOS3D survey at similar redshifts. We find that the [N II] λ 6584/Hα line ratios inside half R200 are higher by 0.2 dex and that the resultant metallicities of the galaxies in the inner part of the cluster are higher by about 0.1 dex, at a given mass, than the metallicities of infalling galaxies and of field galaxies at z ∼ 1.5. The enhanced metallicities of cluster galaxies at z ∼ 1.5 inside 0.5R200 indicate that the density of the intracluster medium in this massive cluster becomes high enough toward the cluster center such that the ram pressure exceeds the restoring pressure of the hot gas reservoir of cluster galaxies. This can remove the gas reservoir and initiate quenching; although the galaxies continue to form stars, albeit at slightly lower rates, using the available cold gas in the disk which is not stripped.
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Ma, Xiangcheng, Michael Y. Grudić, Eliot Quataert, Philip F. Hopkins, Claude-André Faucher-Giguère, Michael Boylan-Kolchin, Andrew Wetzel, Ji-hoon Kim, Norman Murray und Dušan Kereš. „Self-consistent proto-globular cluster formation in cosmological simulations of high-redshift galaxies“. Monthly Notices of the Royal Astronomical Society 493, Nr. 3 (21.02.2020): 4315–32. http://dx.doi.org/10.1093/mnras/staa527.
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ABSTRACT We report the formation of bound star clusters in a sample of high-resolution cosmological zoom-in simulations of z ≥ 5 galaxies from the Feedback In Realistic Environments project. We find that bound clusters preferentially form in high-pressure clouds with gas surface densities over $10^4\, \mathrm{ M}_{\odot }\, {\rm pc}^{-2}$, where the cloud-scale star formation efficiency is near unity and young stars born in these regions are gravitationally bound at birth. These high-pressure clouds are compressed by feedback-driven winds and/or collisions of smaller clouds/gas streams in highly gas-rich, turbulent environments. The newly formed clusters follow a power-law mass function of dN/dM ∼ M−2. The cluster formation efficiency is similar across galaxies with stellar masses of ∼107–$10^{10}\, \mathrm{ M}_{\odot }$ at z ≥ 5. The age spread of cluster stars is typically a few Myr and increases with cluster mass. The metallicity dispersion of cluster members is ∼0.08 dex in $\rm [Z/H]$ and does not depend on cluster mass significantly. Our findings support the scenario that present-day old globular clusters (GCs) were formed during relatively normal star formation in high-redshift galaxies. Simulations with a stricter/looser star formation model form a factor of a few more/fewer bound clusters per stellar mass formed, while the shape of the mass function is unchanged. Simulations with a lower local star formation efficiency form more stars in bound clusters. The simulated clusters are larger than observed GCs due to finite resolution. Our simulations are among the first cosmological simulations that form bound clusters self-consistently in a wide range of high-redshift galaxies.
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Haggar, Roan, Meghan E. Gray, Frazer R. Pearce, Alexander Knebe, Weiguang Cui, Robert Mostoghiu und Gustavo Yepes. „TheThreeHundred project: backsplash galaxies in simulations of clusters“. Monthly Notices of the Royal Astronomical Society 492, Nr. 4 (03.02.2020): 6074–85. http://dx.doi.org/10.1093/mnras/staa273.
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ABSTRACT In the outer regions of a galaxy cluster, galaxies either may be falling into the cluster for the first time or have already passed through the cluster centre at some point in their past. To investigate these two distinct populations, we utilize TheThreeHundred project, a suite of 324 hydrodynamical resimulations of galaxy clusters. In particular, we study the ‘backsplash population’ of galaxies: those that have passed within R200 of the cluster centre at some time in their history, but are now outside of this radius. We find that, on average, over half of all galaxies between R200 and 2R200 from their host at $z$ = 0 are backsplash galaxies, but that this fraction is dependent on the dynamical state of a cluster, as dynamically relaxed clusters have a greater backsplash fraction. We also find that this population is mostly developed at recent times ($z$ ≲ 0.4), and is dependent on the recent history of a cluster. Finally, we show that the dynamical state of a given cluster, and thus the fraction of backsplash galaxies in its outskirts, can be predicted based on observational properties of the cluster.
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Moyer-Anin, A., R. Adam, P. Ade, H. Ajeddig, P. André, E. Artis, H. Aussel et al. „Systematic effects on the upcoming NIKA2 LPSZ scaling relation“. EPJ Web of Conferences 293 (2024): 00032. http://dx.doi.org/10.1051/epjconf/202429300032.
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In cluster cosmology, cluster masses are the main parameter of interest. They are needed to constrain cosmological parameters through the cluster number count. As the mass is not an observable, a scaling relation is needed to link cluster masses to the integrated Compton parameters Y, i.e. the Sunyaev-Zeldovich observable (SZ). Planck cosmological results obtained with cluster number counts are based on a scaling relation measured with clusters at low redshift (z<0.5) observed in SZ and X-ray. In the SZ Large Program (LPSZ) of the NIKA2 collaboration, the scaling relation will be obtained with a sample of 38 clusters at intermediate to high redshift (0.5 < z < 0.9) and observed at high angular resolution in both SZ and X-ray. Thanks to analytical simulation of LPSZ-like samples, we take into account the LPSZ selection function and correct for its effects. Besides, we show that white and correlated noises in the SZ maps do not affect the scaling relation estimation.
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Khullar, Gourav, Matthew B. Bayliss, Michael D. Gladders, Keunho J. Kim, Michael S. Calzadilla, Veronica Strazzullo, Lindsey E. Bleem et al. „Synthesizing Stellar Populations in South Pole Telescope Galaxy Clusters. I. Ages of Quiescent Member Galaxies at 0.3 < z < 1.4“. Astrophysical Journal 934, Nr. 2 (01.08.2022): 177. http://dx.doi.org/10.3847/1538-4357/ac7c0c.
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Abstract Using stellar population synthesis models to infer star formation histories (SFHs), we analyze photometry and spectroscopy of a large sample of quiescent galaxies that are members of Sunyaev–Zel’dovich (SZ)-selected galaxy clusters across a wide range of redshifts. We calculate stellar masses and mass-weighted ages for 837 quiescent cluster members at 0.3 < z < 1.4 using rest-frame optical spectra and the Python-based Prospector framework, from 61 clusters in the SPT-GMOS Spectroscopic Survey (0.3 < z < 0.9) and three clusters in the SPT Hi-z cluster sample (1.25 < z < 1.4). We analyze spectra of subpopulations divided into bins of redshift, stellar mass, cluster mass, and velocity-radius phase-space location, as well as by creating composite spectra of quiescent member galaxies. We find that quiescent galaxies in our data set sample a diversity of SFHs, with a median formation redshift (corresponding to the lookback time from the redshift of observation to when a galaxy forms 50% of its mass, t 50) of z = 2.8 ± 0.5, which is similar to or marginally higher than that of massive quiescent field and cluster galaxy studies. We also report median age–stellar mass relations for the full sample (age of the universe at t 50 (Gyr) = 2.52 (±0.04)–1.66 (±0.12) log10(M/1011 M ⊙)) and recover downsizing trends across stellar mass; we find that massive galaxies in our cluster sample form on aggregate ∼0.75 Gyr earlier than lower-mass galaxies. We also find marginally steeper age–mass relations at high redshifts, and report a bigger difference in formation redshifts across stellar mass for fixed environment, relative to formation redshifts across environment for fixed stellar mass.
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Gonzalez, Anthony H., Kim-Vy H. Tran, Michelle N. Conbere und Dennis Zaritsky. „Galaxy Cluster Assembly at z = 0.37“. Astrophysical Journal 624, Nr. 2 (07.04.2005): L73—L76. http://dx.doi.org/10.1086/430518.
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Tudorica, A., H. Hildebrandt, M. Tewes, H. Hoekstra, C. B. Morrison, A. Muzzin, G. Wilson et al. „Weak lensing magnification of SpARCS galaxy clusters“. Astronomy & Astrophysics 608 (Dezember 2017): A141. http://dx.doi.org/10.1051/0004-6361/201731267.
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Context. Measuring and calibrating relations between cluster observables is critical for resource-limited studies. The mass–richness relation of clusters offers an observationally inexpensive way of estimating masses. Its calibration is essential for cluster and cosmological studies, especially for high-redshift clusters. Weak gravitational lensing magnification is a promising and complementary method to shear studies, that can be applied at higher redshifts. Aims. We aim to employ the weak lensing magnification method to calibrate the mass–richness relation up to a redshift of 1.4. We used the Spitzer Adaptation of the Red-Sequence Cluster Survey (SpARCS) galaxy cluster candidates (0.2 < z < 1.4) and optical data from the Canada France Hawaii Telescope (CFHT) to test whether magnification can be effectively used to constrain the mass of high-redshift clusters. Methods. Lyman-break galaxies (LBGs) selected using the u-band dropout technique and their colours were used as a background sample of sources. LBG positions were cross-correlated with the centres of the sample of SpARCS clusters to estimate the magnification signal, which was optimally-weighted using an externally-calibrated LBG luminosity function. The signal was measured for cluster sub-samples, binned in both redshift and richness. Results. We measured the cross-correlation between the positions of galaxy cluster candidates and LBGs and detected a weak lensing magnification signal for all bins at a detection significance of 2.6–5.5σ. In particular, the significance of the measurement for clusters with z> 1.0 is 4.1σ; for the entire cluster sample we obtained an average M200 of 1.28 -0.21+0.23 × 1014 M⊙. Conclusions. Our measurements demonstrated the feasibility of using weak lensing magnification as a viable tool for determining the average halo masses for samples of high redshift galaxy clusters. The results also established the success of using galaxy over-densities to select massive clusters at z > 1. Additional studies are necessary for further modelling of the various systematic effects we discussed.
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Piskunov, A. E., A. Just, N. V. Kharchenko, P. Berczik, R. D. Scholz, S. Reffert und S. X. Yen. „Global survey of star clusters in the Milky Way“. Astronomy & Astrophysics 614 (Juni 2018): A22. http://dx.doi.org/10.1051/0004-6361/201732337.
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Context. The all-sky Milky Way Star Clusters (MWSC) survey provides uniform and precise ages, along with other relevant parameters, for a wide variety of clusters in the extended solar neighbourhood. Aims. In this study we aim to construct the cluster age distribution, investigate its spatial variations, and discuss constraints on cluster formation scenarios of the Galactic disk during the last 5 Gyrs. Methods. Due to the spatial extent of the MWSC, we have considered spatial variations of the age distribution along galactocentric radius RG, and along Z-axis. For the analysis of the age distribution we used 2242 clusters, which all lie within roughly 2.5 kpc of the Sun. To connect the observed age distribution to the cluster formation history we built an analytical model based on simple assumptions on the cluster initial mass function and on the cluster mass-lifetime relation, fit it to the observations, and determined the parameters of the cluster formation law. Results. Comparison with the literature shows that earlier results strongly underestimated the number of evolved clusters with ages t ≳ 100 Myr. Recent studies based on all-sky catalogues agree better with our data, but still lack the oldest clusters with ages t ≳ 1 Gyr. We do not observe a strong variation in the age distribution along RG, though we find an enhanced fraction of older clusters (t > 1 Gyr) in the inner disk. In contrast, the distribution strongly varies along Z. The high altitude distribution practically does not contain clusters with t < 1 Gyr. With simple assumptions on the cluster formation history, the cluster initial mass function and the cluster lifetime we can reproduce the observations. The cluster formation rate and the cluster lifetime are strongly degenerate, which does not allow us to disentangle different formation scenarios. In all cases the cluster formation rate is strongly declining with time, and the cluster initial mass function is very shallow at the high mass end.
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Zohren, Hannah, Tim Schrabback, Remco F. J. van der Burg, Monique Arnaud, Jean-Baptiste Melin, Jan Luca van den Busch, Henk Hoekstra und Matthias Klein. „Optical follow-up study of 32 high-redshift galaxy cluster candidates from Planck with the William Herschel Telescope“. Monthly Notices of the Royal Astronomical Society 488, Nr. 2 (05.07.2019): 2523–42. http://dx.doi.org/10.1093/mnras/stz1838.
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Abstract The Planck satellite has detected cluster candidates via the Sunyaev Zel’dovich (SZ) effect, but the optical follow-up required to confirm these candidates is still incomplete, especially at high redshifts and for SZ detections at low significance. In this work, we present our analysis of optical observations obtained for 32 Planck cluster candidates using ACAM on the 4.2-m William Herschel Telescope. These cluster candidates were pre-selected using SDSS, WISE, and Pan-STARRS images to likely represent distant clusters at redshifts z ≳ 0.7. We obtain photometric redshift and richness estimates for all of the cluster candidates from a red-sequence analysis of r-, i-, and z-band imaging data. In addition, long-slit observations allow us to measure the redshifts of a subset of the clusters spectroscopically. The optical richness is often lower than expected from the inferred SZ mass when compared to scaling relations previously calibrated at low redshifts. This likely indicates the impact of Eddington bias and projection effects or noise-induced detections, especially at low-SZ significance. Thus, optical follow-up not only provides redshift measurements, but also an important independent verification method. We find that 18 (7) of the candidates at redshifts z > 0.5 (z > 0.8) are at least half as rich as expected from scaling relations, thereby clearly confirming these candidates as massive clusters. While the complex selection function of our sample due to our pre-selection hampers its use for cosmological studies, we do provide a validation of massive high-redshift clusters particularly suitable for further astrophysical investigations.
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Hattori, M. „A Metal Enriched Dark Cluster of Galaxies at Z = 1“. Symposium - International Astronomical Union 187 (2002): 129–38. http://dx.doi.org/10.1017/s0074180900113841.
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Looking for and studying very distant galaxy clusters, clusters at z > 1, are one of the prime subjects of the modern observational cosmology. If the metallicity of the hot intra-cluster medium in very distant galaxy clusters is measured for example, it provides fruitful informations for us to understand the formation and evolution of galaxies. However, difficulty of the study is that there is few confirmed very distant galaxy clusters yet. We first have to search for very distant clusters but it requires very deep observations. A random selection of sky is not practical. We have to select the sky. In this article, it is demonstrated that missing lens problem has close connection with very distant cluster of galaxies and dark lens searches could open a new window for studying very distant cluster of galaxies.
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Lubin, Lori M. „Clusters in the Optical“. Highlights of Astronomy 13 (2005): 286–90. http://dx.doi.org/10.1017/s1539299600015811.
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AbstractI present a brief review of studies of galaxy clusters in the optical. Clusters of galaxies were historically detected in the optical, and this selection provided the first large, statistical samples of clusters. I describe how these samples have been instrumental in characterizing the properties of the local cluster population, tracing large scale structure, and constraining cosmology. More sophisticated cluster detection techniques in the optical have now made it possible to detect large numbers of clusters up to z ~ 1.4. I describe these advances and discuss how large-area and deep surveys are being used to determine the evolution in the global cluster properties and the properties of cluster galaxy populations.
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Duffy, R. T., C. H. A. Logan, B. J. Maughan, D. Eckert, M. Birkinshaw, N. Clerc, S. Ettori et al. „The XXL Survey – XLVIII. X-ray follow-up of distant XXL clusters: masses, scaling relations, and AGN contamination“. Monthly Notices of the Royal Astronomical Society 512, Nr. 2 (09.03.2022): 2525–36. http://dx.doi.org/10.1093/mnras/stac617.
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ABSTRACT We use deep follow-up XMM–Newton observations of six clusters discovered in the XXL Survey at z > 1 to gain robust measurements of their X-ray properties and to investigate the extent to which scaling relations at low redshift are valid at z > 1. This sample is unique as it has been investigated for active galactic nucleus (AGN) contamination, which ensures measurements are not undermined by systematic uncertainties, and pushes to lower mass at higher redshift than is usually possible, for example with Sunyaev–Zel’dovich (SZ) selected clusters. We determine the flux contribution of point sources to the XXL cluster flux in order to test for the presence of AGN in other high-redshift cluster candidates, and find 3XLSS J231626.8−533822 to be a point source misclassified as a cluster and 3XLSS J232737.3−541618 to be a genuine cluster. We present the first attempt to measure the hydrostatic masses in a bright subsample of z > 1 X-ray selected galaxy clusters with a known selection function. Periods of high particle background significantly reduced the effective exposure times of observations (losing >50 per cent in some cases) limiting the power of this study. When combined with complementary SZ selected cluster samples at higher masses, the data appear broadly consistent with the self-similar evolution of the low redshift scaling relations between intracluster medium properties and cluster mass, suggesting that properties such as the X-ray temperature, gas mass, and SZ signal remain reliable mass proxies even at high redshift.
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Lee, Seong-Kook, Myungshin Im, Minhee Hyun, Bomi Park, Jae-Woo Kim, Dohyeong Kim und Yongjung Kim. „More connected, more active: galaxy clusters and groups at z ∼ 1 and the connection between their quiescent galaxy fractions and large-scale environments“. Monthly Notices of the Royal Astronomical Society 490, Nr. 1 (16.09.2019): 135–55. http://dx.doi.org/10.1093/mnras/stz2564.
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ABSTRACT High-redshift galaxy clusters, unlike local counterparts, show diverse star formation activities. However, it is still unclear what keeps some of the high-redshift clusters active in star formation. To address this issue, we performed a multiobject spectroscopic observation of 226 high-redshift (0.8 < z < 1.3) galaxies in galaxy cluster candidates and the areas surrounding them. Our spectroscopic observation reveals six to eight clusters/groups at z ∼ 0.9 and z ∼ 1.3. The redshift measurements demonstrate the reliability of our photometric redshift measurements, which in turn gives credibility for using photometric redshift members for the analysis of large-scale structures (LSSs). Our investigation of the large-scale environment (∼10 Mpc) surrounding each galaxy cluster reveals LSSs – structures up to ∼10 Mpc scale – around many of, but not all, the confirmed overdensities and the cluster candidates. We investigate the correlation between quiescent galaxy fraction of galaxy overdensities and their surrounding LSSs, with a larger sample of ∼20 overdensities including photometrically selected overdensities at 0.6 < z < 0.9. Interestingly, galaxy overdensities embedded within these extended LSSs show a lower fraction of quiescent galaxies ($\sim 20{{\ \rm per\ cent}}$) than isolated ones at similar redshifts (with a quiescent galaxy fraction of $\sim 50 {{\ \rm per\ cent}}$). Furthermore, we find a possible indication that clusters/groups with a high quiescent galaxy fraction are more centrally concentrated. Based on these results, we suggest that LSSs are the main reservoirs of gas and star-forming galaxies to keep galaxy clusters fresh and extended in size at z ∼ 1.
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Huang, Ting-Chi, Hideo Matsuhara, Tomotsugu Goto, Daryl Joe D. Santos, Simon C.-C. Ho, Seong Jin Kim, Tetsuya Hashimoto et al. „Optically detected galaxy cluster candidates in the AKARI North Ecliptic Pole field based on photometric redshift from the Subaru Hyper Suprime-Cam“. Monthly Notices of the Royal Astronomical Society 506, Nr. 4 (13.08.2021): 6063–80. http://dx.doi.org/10.1093/mnras/stab2128.
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ABSTRACT Galaxy clusters provide an excellent probe in various research fields in astrophysics and cosmology. However, the number of galaxy clusters detected so far in the AKARI North Ecliptic Pole (NEP) field is limited. In this work, we provide galaxy cluster candidates in the AKARI NEP field with the minimum requisites based only on the coordinates and photometric redshift (photo-z) of galaxies. We used galaxies detected in five optical bands (g, r, i, z, and Y) by the Subaru Hyper Suprime-Cam (HSC), with additional data from the u band obtained from the Canada-France-Hawaii Telescope (CFHT) MegaPrime/MegaCam, and from the IRAC1 and IRAC2 bands from the Spitzer space telescope for photo-z estimation. We calculated the local density around every galaxy using the 10th-nearest neighbourhood. Cluster candidates were determined by applying the friends-of-friends algorithm to over-densities. A total of 88 cluster candidates containing 4390 member galaxies below redshift 1.1 in 5.4 deg2 were identified. The reliability of our method was examined through false-detection tests, redshift-uncertainty tests, and applications on the Cosmic Evolution Survey (COSMOS) data, giving false-detection rates of 0.01 to 0.05 and a recovery rate of 0.9 at high richness. Three X-ray clusters previously observed by ROSAT and Chandra were recovered. The cluster galaxies show a higher stellar mass and lower star formation rate compared with the field galaxies in two-sample Z-tests. These cluster candidates are useful for environmental studies of galaxy evolution and future astronomical surveys in the NEP, where AKARI has performed unique nine-band mid-infrared photometry for tens of thousands of galaxies.
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Sarron, F., C. Adami, F. Durret und C. Laigle. „Pre-processing of galaxies in cosmic filaments around AMASCFI clusters in the CFHTLS“. Astronomy & Astrophysics 632 (26.11.2019): A49. http://dx.doi.org/10.1051/0004-6361/201935394.
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Context. Galaxy clusters and groups are thought to accrete material along the preferred direction of cosmic filaments. These structures have proven difficult to detect because their contrast is low, however, and only a few studies have focused on cluster infall regions. Aims. We detect cosmic filaments around galaxy clusters using photometric redshifts in the range 0.15 < z < 0.7. We characterise galaxy populations in these structures to study the influence of pre-processing by cosmic filaments and galaxy groups on star formation quenching. Methods. We detected cosmic filaments in the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS) T0007 data, focusing on regions around clusters of the AMASCFI CFHTLS cluster sample. The filaments were reconstructed with the discrete persistent structure extractor (DISPERSE) algorithm in photometric redshift slices. We show that this reconstruction is reliable for a CFHTLS-like survey at 0.15 < z < 0.7 using a mock galaxy catalogue. We split our galaxy catalogue into two populations (passive and star forming) using the LePhare spectral energy density fitting algorithm and worked with two redshift bins (0.15 < z ≤ 0.4 and 0.4 < z < 0.7). Results. We showed that the AMASCFI cluster connectivity (i.e. the number of filaments that is connected to a cluster) increases with cluster mass M200. Filament galaxies outside R200 are found to be closer to clusters at low redshift, regardless of the galaxy type. Passive galaxies in filaments are closer to clusters than star-forming galaxies in the low redshift bin alone. The passive fraction of galaxies decreases with increasing clustercentric distance up to d ∼ 5 cMpc. Galaxy groups and clusters that are not located at nodes of our reconstruction are mainly found inside cosmic filaments. Conclusions. These results give clues for pre-processing in cosmic filaments that could be due to smaller galaxy groups. This trend could be further explored by applying this method to larger photometric surveys such as the Hyper Suprime-Cam Subaru Strategic Program (HSC-SPP) or Euclid.