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Paper pool » History » Version 38

Shantanu Desai, 01/30/2013 04:27 PM

1 1 Robert Suhada
h1. Paper pool
2 1 Robert Suhada
3 14 Robert Suhada
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7 34 Robert Suhada
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11 6 Robert Suhada
12 28 Robert Suhada
h2. The relation between velocity dispersion and mass in simulated clusters of galaxies: dependence on the tracer and the baryonic physics
13 29 Robert Suhada
14 28 Robert Suhada
Emiliano Munari, Andrea Biviano, Stefano Borgani, Giuseppe Murante, Dunja Fabjan
15 28 Robert Suhada
(Submitted on 8 Jan 2013)
16 28 Robert Suhada
[Abridged] We present an analysis of the relation between the masses of cluster- and group-sized halos, extracted from $\Lambda$CDM cosmological N-body and hydrodynamic simulations, and their velocity dispersions, at different redshifts from $z=2$ to $z=0$. The main aim of this analysis is to understand how the implementation of baryonic physics in simulations affects such relation, i.e. to what extent the use of the velocity dispersion as a proxy for cluster mass determination is hampered by the imperfect knowledge of the baryonic physics. In our analysis we use several sets of simulations with different physics implemented. Velocity dispersions are determined using three different tracers, DM particles, subhalos, and galaxies.
17 28 Robert Suhada
We confirm that DM particles trace a relation that is fully consistent with the theoretical expectations based on the virial theorem and with previous results presented in the literature. On the other hand, subhalos and galaxies trace steeper relations, and with larger values of the normalization. Such relations imply that galaxies and subhalos have a $\sim10$ per cent velocity bias relative to the DM particles, which can be either positive or negative, depending on halo mass, redshift and physics implemented in the simulation.
18 28 Robert Suhada
We explain these differences as due to dynamical processes, namely dynamical friction and tidal disruption, acting on substructures and galaxies, but not on DM particles. These processes appear to be more or less effective, depending on the halo masses and the importance of baryon cooling, and may create a non-trivial dependence of the velocity bias and the $\soneD$--$\Mtwo$ relation on the tracer, the halo mass and its redshift.
19 28 Robert Suhada
These results are relevant in view of the application of velocity dispersion as a proxy for cluster masses in ongoing and future large redshift surveys.
20 28 Robert Suhada
21 28 Robert Suhada
http://arXiv.org/abs/1301.1682
22 28 Robert Suhada
 	
23 31 Joseph Mohr
Votes: *1*
24 28 Robert Suhada
25 27 Jiayi Liu
h2. The Contribution of Radio Galaxy Contamination to Measurements of the Sunyaev-Zel'dovich Decrement in Massive Galaxy Clusters at 140 GHz with Bolocam
26 27 Jiayi Liu
27 27 Jiayi Liu
Jack Sayers, Tony Mroczkowski, Nicole G. Czakon, Sunil R. Golwala, Adam Mantz, Silvia Ameglio, Tom P. Downes, Patrick M. Koch, Kai-Yang Lin, Sandor M. Molnar, Stephen J. C. Muchovej, Elena Pierpaoli, Jennifer A. Shitanishi, Seth Siegel, Keiichi Umetsu
28 27 Jiayi Liu
(Submitted on 23 Sep 2012)
29 27 Jiayi Liu
We describe in detail our characterization of the compact radio source population in 140 GHz Bolocam observations of a set of 45 massive galaxy clusters. We use a combination of 1.4 and 30 GHz data to select a total of 28 probable cluster member radio galaxies and also to predict their 140 GHz flux densities. All of these galaxies are steep-spectrum radio sources and they are found preferentially in the cool-core clusters within our sample. In particular, 11 of the 12 brightest cluster member radio sources are associated with cool-core systems. Although none of the individual galaxies are robustly detected in the Bolocam data, the ensemble-average flux density at 140 GHz is consistent with, but slightly lower than, the extrapolation from lower frequencies assuming a constant spectral index. Specifically, we find a multiplicative factor of 0.85 +- 0.16 between the flux densities observed at 140 GHz and those predicted from a power-law extrapolation. In addition, our data indicate an intrinsic scatter of 30 percent around the power-law extrapolated flux densities at 140 GHz, although our data do not tightly constrain this scatter. For our cluster sample, which is composed of high mass and moderate redshift systems, we find that the maximum fractional change in the Sunyaev-Zel'dovich signal integrated over any single cluster due to the presence of these radio sources is 20 percent, and only 1/4 of the clusters show a fractional change of more than 1 percent. The amount of contamination is strongly dependent on cluster morphology, and nearly all of the clusters with more than 1 percent contamination are cool-core systems. This result indicates that radio contamination is not significant compared to current noise levels in 140 GHz images of massive clusters and is in good agreement with the level of radio contamination found in previous results based on lower frequency data or simulations.
30 27 Jiayi Liu
31 27 Jiayi Liu
http://arxiv.org/abs/1209.5129v1
32 27 Jiayi Liu
33 27 Jiayi Liu
Votes: *0*
34 1 Robert Suhada
35 25 Robert Suhada
h2. Mind the Gap: Tightening the Mass-Richness Relation with Magnitude Gaps
36 1 Robert Suhada
37 25 Robert Suhada
Andrew P. Hearin, Andrew R. Zentner, Jeffrey A. Newman, Andreas A. Berlind
38 25 Robert Suhada
(Submitted on 4 Jul 2012 (v1), last revised 7 Jan 2013 (this version, v2))
39 25 Robert Suhada
We investigate the potential to improve optical tracers of cluster mass by exploiting measurements of the magnitude gap, m12, defined as the difference between the r-band absolute magnitude of the two brightest cluster members. We find that in a mock sample of galaxy groups and clusters constructed from the Bolshoi simulation, the scatter about the mass-richness relation decreases by 15-20% when magnitude gap information is included. A similar trend is evident in a volume-limited, spectroscopic sample of galaxy groups observed in the Sloan Digital Sky Survey (SDSS). We find that SDSS groups with small magnitude gaps are richer than large-gap groups at fixed values of the one-dimensional velocity dispersion among group members sigma_v, which we use as a mass proxy. We demonstrate explicitly that m12 contains information about cluster mass that supplements the information provided by group richness and the luminosity of the brightest cluster galaxy, L_bcg. In so doing, we show that the luminosities of the members of a group with richness N are inconsistent with the distribution of luminosities that results from N random draws from the global galaxy luminosity function. As the cosmological constraining power of galaxy clusters is limited by the precision in cluster mass determination, our findings suggest a new way to improve the cosmological constraints derived from galaxy clusters.
40 24 Robert Suhada
41 25 Robert Suhada
http://arXiv.org/abs/1207.1074
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43 25 Robert Suhada
Notes:
44 25 Robert Suhada
- recommended by Ben Hoyle
45 26 Robert Suhada
46 25 Robert Suhada
Votes: *1*
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48 25 Robert Suhada
h2. The Atacama Cosmology Telescope: the stellar content of galaxy clusters selected using the Sunyaev-Zel'dovich effect
49 24 Robert Suhada
50 25 Robert Suhada
Matt Hilton, Matthew Hasselfield, Cristóbal Sifón, Andrew J. Baker, L. Felipe Barrientos, Nicholas Battaglia, J. Richard Bond, Devin Crichton, Sudeep Das, Mark J. Devlin, Megan Gralla, Amir Hajian, Adam D. Hincks, John P. Hughes, Leopoldo Infante, Kent D. Irwin, Arthur Kosowsky, Yen-Ting Lin, Tobias A. Marriage, Danica Marsden, Felipe Menanteau, Kavilan Moodley, Michael D. Niemack, Mike R. Nolta, Lyman A. Page, Erik D. Reese, Jon Sievers, David N. Spergel, Edward J. Wollack
51 24 Robert Suhada
(Submitted on 4 Jan 2013)
52 25 Robert Suhada
We present a first measurement of the stellar mass component of galaxy clusters selected via the Sunyaev-Zel'dovich (SZ) effect, using 3.6 um and 4.5 um photometry from the Spitzer Space Telescope. Our sample consists of 14 clusters detected by the Atacama Cosmology Telescope (ACT), which span the redshift range 0.27 < z < 1.07 (median z = 0.50), and have dynamical mass measurements, accurate to about 30 per cent, with median M500 = 6.9 x 10^{14} MSun. We measure the 3.6 um and 4.5 um galaxy luminosity functions, finding the characteristic magnitude (m*) and faint-end slope (alpha) to be similar to those for IR-selected cluster samples. We perform the first measurements of the scaling of SZ-observables (Y500 and y0) with both brightest cluster galaxy (BCG) stellar mass and total cluster stellar mass (M500star). We find a significant correlation between BCG stellar mass and Y500 (E(z)^{-2/3} DA^2 Y500 ~ M*^{1.2 +/- 0.6}), although we are not able to obtain a strong constraint on the slope of the relation due to the small sample size. Additionally, we obtain E(z)^{-2/3} DA^2 Y500 ~ M500star^{1.0 +/- 0.6} for the scaling with total stellar mass. The mass fraction in stars spans the range 0.006-0.034, with the second ranked cluster in terms of dynamical mass (ACT-CL J0237-4939) having an unusually low total stellar mass and the lowest stellar mass fraction. For the five clusters with gas mass measurements available in the literature, we see no evidence for a shortfall of baryons relative to the cosmic mean value.
53 24 Robert Suhada
54 25 Robert Suhada
http://arXiv.org/abs/1301.0780
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56 24 Robert Suhada
Votes: *0*
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58 24 Robert Suhada
h2. The Atacama Cosmology Telescope: likelihood for small-scale CMB data
59 24 Robert Suhada
60 24 Robert Suhada
J. Dunkley, E. Calabrese, J. Sievers, G. E. Addison, N. Battaglia, E. S. Battistelli, J. R. Bond, S. Das, M. J. Devlin, R. Dunner, J. W. Fowler, M. Gralla, A. Hajian, M. Halpern, M. Hasselfield, A. D. Hincks, R. Hlozek, J. P. Hughes, K. D. Irwin, A. Kosowsky, T. Louis, T. A. Marriage, D. Marsden, F. Menanteau, K. Moodley, M. Niemack, M. R. Nolta, L. A. Page, B. Partridge, N. Sehgal, D. N. Spergel, S. T. Staggs, E. R. Switzer, H. Trac, E. Wollack
61 24 Robert Suhada
(Submitted on 4 Jan 2013)
62 24 Robert Suhada
The Atacama Cosmology Telescope has measured the angular power spectra of microwave fluctuations to arcminute scales at frequencies of 148 and 218 GHz, from three seasons of data. At small scales the fluctuations in the primordial Cosmic Microwave Background (CMB) become increasingly obscured by extragalactic foregounds and secondary CMB signals. We present results from a nine-parameter model describing these secondary effects, including the thermal and kinematic Sunyaev-Zel'dovich (tSZ and kSZ) power; the clustered and Poisson-like power from Cosmic Infrared Background (CIB) sources, and their frequency scaling; the tSZ-CIB correlation coefficient; the extragalactic radio source power; and thermal dust emission from Galactic cirrus in two different regions of the sky. In order to extract cosmological parameters, we describe a likelihood function for the ACT data, fitting this model to the multi-frequency spectra in the multipole range 500<ell<10000. We extend the likelihood to include spectra from the South Pole Telescope at frequencies of 95, 150, and 220 GHz. Accounting for different radio source levels and Galactic cirrus emission, the same model provides an excellent fit to both datasets simultaneously, with chi2/dof= 675/697 for ACT, and 96/107 for SPT. We then use the multi-frequency likelihood to estimate the CMB power spectrum from ACT in bandpowers, marginalizing over the secondary parameters. This provides a simplified `CMB-only' likelihood in the range 500<ell<3500 for use in cosmological parameter estimation.
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64 24 Robert Suhada
http://arXiv.org/abs/1301.0776
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66 24 Robert Suhada
Votes: *0*
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68 24 Robert Suhada
h2. The X-ray/SZ view of the virial region. I. Thermodynamic properties
69 24 Robert Suhada
70 24 Robert Suhada
Dominique Eckert, Silvano Molendi, Franco Vazza, Stefano Ettori, Stéphane Paltani
71 24 Robert Suhada
(Submitted on 3 Jan 2013)
72 24 Robert Suhada
We measure the thermodynamic properties of cluster outer regions to provide constraints on the processes that rule the formation of large scale structures. We derived the thermodynamic properties of the intracluster gas (temperature, entropy) by combining the SZ thermal pressure from Planck and the X-ray gas density from ROSAT. This method allowed us to reconstruct for the first time temperature and entropy profiles out to the virial radius and beyond in a large sample of objects. At variance with several recent Suzaku studies, we find that the entropy rises steadily with radius, albeit at at a somewhat lower rate than predicted by self-similar expectations. We note significant differences between relaxed, cool-core systems and unrelaxed clusters in the outer regions. Relaxed systems appear to follow the self-similar expectations more closely than perturbed objects. Our results indicate that the well-known entropy excess observed in cluster cores extends well beyond the central regions. When correcting for the gas depletion, the observed entropy profiles agree with the prediction from gravitational collapse only, especially for cool-core clusters.
73 24 Robert Suhada
74 24 Robert Suhada
http://arXiv.org/abs/1301.0617
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76 24 Robert Suhada
Votes: *0*
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78 24 Robert Suhada
h2. The X-ray/SZ view of the virial region. II. Gas mass fraction
79 24 Robert Suhada
80 24 Robert Suhada
Dominique Eckert, Stefano Ettori, Silvano Molendi, Franco Vazza, Stéphane Paltani
81 24 Robert Suhada
(Submitted on 3 Jan 2013)
82 24 Robert Suhada
Several recent studies used the hot gas fraction of galaxy clusters as a standard ruler to constrain dark energy, which provides competitive results compared to other techniques. This method, however, relies on the assumption that the baryon fraction in clusters agrees with the cosmic value Omega_b/Omega_m, and does not differ from one system to another. We test this hypothesis by measuring the gas mass fraction over the entire cluster volume in a sample of local clusters. Combining the SZ thermal pressure from Planck and the X-ray gas density from ROSAT, we measured for the first time the average gas fraction (fgas) out to the virial radius and beyond in a large sample of clusters. We also obtained azimuthally-averaged measurements of the gas fraction for 18 individual systems, which we used to compute the scatter of fgas around the mean value at different radii and its dependence on the cluster's temperature. The gas mass fraction increases with radius and reaches the cosmic baryon fraction close to R200. At R200, we measure fgas,200=0.176+/-0.009. We find significant differences between the baryon fraction of relaxed, cool-core (CC) systems and unrelaxed, non-cool core (NCC) clusters in the outer regions. In average, the gas fraction in NCC clusters slightly exceeds the cosmic baryon fraction, while in CC systems the gas fraction converges to the expected value when accounting for the stellar content, without any evidence for variations from one system to another. We find that fgas estimates in NCC systems slightly disagree with the cosmic value approaching R200. This result could be explained either by a violation of the assumption of hydrostatic equilibrium or by an inhomogeneous distribution of the gas mass. Conversely, cool-core clusters are found to provide reliable constraints on fgas at overdensities >200, which makes them suitable for cosmological studies.
83 24 Robert Suhada
84 24 Robert Suhada
http://arXiv.org/abs/1301.0624
85 24 Robert Suhada
86 24 Robert Suhada
Votes: *0*
87 24 Robert Suhada
88 21 Jiayi Liu
h2. Planck Intermediate Results. XI: The gas content of dark matter halos: the Sunyaev-Zeldovich-stellar mass relation for locally brightest galaxies
89 21 Jiayi Liu
90 21 Jiayi Liu
We present the scaling relation between Sunyaev-Zeldovich (SZ) signal and stellar mass for almost 260,000 locally brightest galaxies (LBGs) selected from the Sloan Digital Sky Survey (SDSS). These are predominantly the central galaxies of their dark matter halos. We calibrate the stellar-to-halo mass conversion using realistic mock catalogues based on the Millennium Simulation. Applying a multi-frequency matched filter to the Planck data for each LBG, and averaging the results in bins of stellar mass, we measure the mean SZ signal down to $M_\ast\sim 2\times 10^{11} \Msolar$, with a clear indication of signal at even lower stellar mass. We derive the scaling relation between SZ signal and halo mass by assigning halo properties from our mock catalogues to the real LBGs and simulating the Planck observation process. This relation shows no evidence for deviation from a power law over a halo mass range extending from rich clusters down to $M_{500}\sim 2\times 10^{13} \Msolar$, and there is a clear indication of signal down to $M_{500}\sim 4\times 10^{12} \Msolar$. Planck's SZ detections in such low-mass halos imply that about a quarter of all baryons have now been seen in the form of hot halo gas, and that this gas must be less concentrated than the dark matter in such halos in order to remain consistent with X-ray observations. At the high-mass end, the measured SZ signal is 20% lower than found from observations of X-ray clusters, a difference consistent with Malmquist bias effects in the X-ray sample.
91 21 Jiayi Liu
92 22 Jiayi Liu
http://arxiv.org/abs/1212.4131
93 22 Jiayi Liu
Votes : *1*
94 22 Jiayi Liu
95 18 Robert Suhada
h2. The Planck Sunyaev-Zel'dovich vs. the X-ray View of the Coma Cluster
96 18 Robert Suhada
97 18 Robert Suhada
R. Fusco-Femiano (1), A. Lapi (2,3), A. Cavaliere (2,4) (1-IAPS/INAF Roma, Italy, 2-Univ. 'Tor Vergata', Rome, Italy, 3-SISSA, Trieste, Italy, 4-OAR/INAF, Rome, Italy)
98 18 Robert Suhada
(Submitted on 13 Dec 2012)
99 18 Robert Suhada
The Planck collaboration has recently published precise and resolved measurements of the Sunyaev-Zel'dovich effect in Abell 1656 (the Coma cluster of galaxies), so directly gauging the electron pressure profile in the intracluster plasma. On the other hand, such a quantity may be also derived from combining the density and temperature provided by X-ray observations of the thermal bremsstrahlung radiation emitted by the plasma. We find a model-independent tension between the SZ and the X-ray pressure, with the SZ one being definitely lower by 15-20%. We propose that such a challenging tension can be resolved in terms of an additional, non-thermal support to the gravitational equilibrium of the intracluster plasma. This can be straightforwardly included in our Supermodel, so as to fit in detail the Planck SZ profile while being consistent with the X-ray observables. Possible origins of the nonthermal component include cosmic-ray protons, ongoing turbulence, and relativistic electrons; given the existing observational constraints on the first two options, here we focus on the third. For this to be effective, we find that the electron population must include not only an energetic tail accelerated to gamma> 10^3 responsible for the Coma radiohalo, but also many more, lower energy electrons. The electron acceleration is to be started by merging events similar to those which provided the very high central entropy of the thermal intracluster plasma in Coma.
100 18 Robert Suhada
101 18 Robert Suhada
http://arxiv.org/abs/1212.3082
102 18 Robert Suhada
103 19 Robert Suhada
Votes : *0*
104 19 Robert Suhada
105 16 Robert Suhada
h2. The extended ROSAT-ESO Flux Limited X-ray Galaxy Cluster Survey (REFLEX II) III. Construction of the first flux-limited supercluster sample
106 16 Robert Suhada
107 16 Robert Suhada
Gayoung Chon, Hans Boehringer, Nina Nowak
108 16 Robert Suhada
(Submitted on 7 Dec 2012)
109 16 Robert Suhada
We present the first supercluster catalogue constructed with the extended ROSAT-ESO Flux Limited X-ray Galaxy Cluster survey (REFLEX II) data, which comprises 919 X-ray selected galaxy clusters. Based on this cluster catalogue we construct a supercluster catalogue using a friends-of-friends algorithm with a linking length depending on the local cluster density. The resulting catalogue comprises 164 superclusters at redshift z<=0.4. We study the properties of different catalogues such as the distributions of the redshift, extent and multiplicity by varying the choice of parameters. In addition to the main catalogue we compile a large volume-limited cluster sample to investigate the statistics of the superclusters. We also compare the X-ray luminosity function for the clusters in superclusters with that for the field clusters with the flux- and volume-limited catalogues. The results mildly support the theoretical suggestion of a top-heavy X-ray luminosity function of galaxy clusters in regions of high cluster density.
110 16 Robert Suhada
111 16 Robert Suhada
http://arxiv.org/abs/1212.1597
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113 16 Robert Suhada
Votes : *0*
114 16 Robert Suhada
115 7 Robert Suhada
h2. An HST/WFC3-UVIS View of the Starburst in the Cool Core of the Phoenix Cluster
116 7 Robert Suhada
117 7 Robert Suhada
Michael McDonald, Bradford Benson, Sylvain Veilleux, Marshall W. Bautz, Christian L. Reichardt
118 7 Robert Suhada
(Submitted on 29 Nov 2012)
119 7 Robert Suhada
We present the results of Hubble Space Telescope Wide Field Camera 3 observations of the core of the Phoenix Cluster (SPT-CLJ2344-4243) in five broadband filters spanning rest-frame 1000-5500A. These observations reveal complex, filamentary blue emission, extending for >40 kpc from the brightest cluster galaxy. We observe an underlying, diffuse population of old stars, following an r^1/4 distribution, confirming that this system is somewhat relaxed. The spectral energy distribution in the inner part of the galaxy, as well as along the extended filaments, is a smooth continuum and is consistent with that of a star-forming galaxy, suggesting that the extended, filamentary emission is not due to a large-scale highly-ionized outflow from the central AGN, but rather a massive population of young stars. We estimate an extinction-corrected star formation rate of 798 +/- 42 Msun/yr, consistent with our earlier work based on low spatial resolution ultraviolet, optical, and infrared imaging. We argue that such a high star formation rate is not the result of a merger, as it would require >10 mergers with gas-rich galaxies and there is no evidence for such multiple merger events. Instead, we propose that the high X-ray cooling rate of ~2850 Msun/yr is the origin of the cold gas reservoir. The combination of such a high cooling rate and the relatively weak radio source in the cluster core suggests that feedback has been unable to halt runaway cooling in this system, leading to this tremendous burst of star formation.
120 7 Robert Suhada
121 17 Robert Suhada
http://arxiv.org/abs/1211.7058
122 17 Robert Suhada
123 7 Robert Suhada
Votes: *0*
124 7 Robert Suhada
125 7 Robert Suhada
h2. Reconstructing three-dimensional parameters of galaxy clusters via multifrequency SZ observations
126 7 Robert Suhada
127 7 Robert Suhada
Andrea Morandi, Daisuke Nagai, Wei Cui
128 7 Robert Suhada
(Submitted on 29 Nov 2012)
129 7 Robert Suhada
The Sunyaev-Zeldovich (SZ) effect is a promising tool to study physical properties of the hot X-ray emitting intracluster medium (ICM) in galaxy clusters. To date, most SZ observations have been interpreted in combination with X-ray follow-up measurements in order to determine the ICM temperature and estimate the cluster mass. Future high-resolution, multifrequency SZ observations promise to enable detailed studies of the ICM structures, by measuring the ICM temperature through the temperature-dependent relativistic corrections. In this work we develop a non-parametric method to derive three-dimensional physical quantities, including temperature, pressure, total mass, and peculiar velocities, of galaxy clusters from SZ observations alone. We test the performance of this method using hydrodynamical simulations of galaxy clusters, in order to assess systematic uncertainties in the reconstructed physical parameters. In particular, we analyze mock Cerro Chajnantor Atacama Telescope (CCAT) SZ observations, taking into account various sources of systematic uncertainties associated with instrumental effects and astrophysical foregrounds. We show that our method enables accurate reconstruction of the three-dimensional ICM profiles, while retaining full information about the gas distribution. We discuss the application of this technique for ongoing and future multifrequency SZ observations.
130 7 Robert Suhada
131 7 Robert Suhada
http://arxiv.org/abs/1211.7096
132 7 Robert Suhada
133 7 Robert Suhada
Votes: *0*
134 7 Robert Suhada
135 1 Robert Suhada
h2. Quenching star formation in cluster galaxies
136 1 Robert Suhada
137 1 Robert Suhada
Dan S. Taranu, Michael J. Hudson, Michael L. Balogh, Russell J. Smith, Chris Power, Brad Krane
138 1 Robert Suhada
(Submitted on 14 Nov 2012)
139 1 Robert Suhada
In order to understand the processes that quench star formation within rich clusters, we construct a library of subhalo orbits drawn from lambdaCDM cosmological N-body simulations of four rich clusters. The orbits are combined with models of star formation followed by quenching in the cluster environment to predict colours and spectroscopic line indices of satellite galaxies. Simple models with only halo mass-dependent quenching and without environmental (i.e. cluster-dependent) quenching fail to reproduce the observed cluster-centric colour and absorption linestrength gradients. Models in which star formation is instantly quenched at the virial radius also fail to match the observations. Better matches to the data are achieved by more complicated bulge-disc models in which the bulge stellar populations depend only on the galaxy subhalo mass while the disc quenching depends on the cluster environment. In the most successful models quenching begins at pericentre, operating on an exponential timescale of 2 -- 3 Gyr, with the shorter timescale being a better match to disc colours as a function of cluster-centric radius and the longer being a better fit to the radial dependence of stellar absorption line indices. The models thus imply that the environments of rich clusters must impact star formation rates of infalling galaxies on relatively long timescales - several times longer than a typical halo spends within the virial radius of a cluster. This scenario favours gentler quenching mechanisms such as slow "strangulation" over more rapid ram-pressure stripping.
140 1 Robert Suhada
141 1 Robert Suhada
http://arxiv.org/abs/1211.3411
142 1 Robert Suhada
143 7 Robert Suhada
Votes: *0*
144 1 Robert Suhada
145 1 Robert Suhada
h2. Sunyaev-Zel'dovich-Measured Pressure Profiles from the Bolocam X-ray/SZ Galaxy Cluster Sample
146 1 Robert Suhada
147 1 Robert Suhada
Jack Sayers, Nicole G. Czakon, Adam Mantz, Sunil R. Golwala, Silvia Ameglio, Tom P. Downes, Patrick M. Koch, Kai-Yang Lin, Ben J. Maughan, Sandor M. Molnar, Leonidas Moustakas, Tony Mroczkowski, Elena Pierpaoli, Jennifer A. Shitanishi, Seth Siegel, Keiichi Umetsu, Nina Van der Pyl
148 1 Robert Suhada
(Submitted on 7 Nov 2012)
149 1 Robert Suhada
We describe Sunyaev-Zel'dovich (SZ) effect measurements and analysis of the intracluster medium (ICM) pressure profiles of a set of 45 massive galaxy clusters imaged using Bolocam at the Caltech Submillimeter Observatory. We have used masses determined from Chandra X-ray observations to scale each cluster's profile by the overdensity radius R500 and the mass-and-redshift-dependent normalization factor P500. We deproject the average pressure profile of our sample into 13 logarithmically spaced radial bins between 0.07R500 and 3.5R500. We find that a generalized Navarro, Frenk, and White (gNFW) profile describes our data with sufficient goodness-of-fit and best-fit parameters (C500, alpha, beta, gamma, P0 = 1.18, 0.86, 3.67, 0.67, 4.29). We also use the X-ray data to define cool-core and disturbed subsamples of clusters, and we constrain the average pressure profiles of each of these subsamples. We find that given the precision of our data the average pressure profiles of disturbed and cool-core clusters are consistent with one another at R>~0.15R500, with cool-core systems showing indications of higher pressure at R<~0.15R500. In addition, for the first time, we place simultaneous constraints on the mass scaling of cluster pressure profiles, their ensemble mean profile, and their radius-dependent intrinsic scatter between 0.1R500 and 2.0R500. The scatter among profiles is minimized at radii between ~0.2R500 and ~0.5R500, with a value of ~20%. The best-fit mass scaling has a power-law slope of 0.49, which is shallower than the nominal prediction of 2/3 from self-similar hydrostatic equilibrium models. These results for the intrinsic scatter and mass scaling are largely consistent with previous analyses, most of which have relied heavily on X-ray derived pressures of clusters at significantly lower masses and redshifts compared to our sample.
150 1 Robert Suhada
151 1 Robert Suhada
http://arxiv.org/abs/1211.1632
152 1 Robert Suhada
153 7 Robert Suhada
Votes: *0*
154 1 Robert Suhada
155 1 Robert Suhada
h2. The Sloan Bright Arcs Survey: Ten Strong Gravitational Lensing Clusters and Evidence of Overconcentration
156 1 Robert Suhada
157 1 Robert Suhada
Matthew P. Wiesner, Huan Lin, Sahar S. Allam, James Annis, Elizabeth J. Buckley-Geer, H. Thomas Diehl, Donna Kubik, Jeffrey M. Kubo, Douglas Tucker
158 1 Robert Suhada
(Submitted on 6 Nov 2012)
159 1 Robert Suhada
We describe ten strong lensing galaxy clusters of redshift 0.26-0.56 that were found in the Sloan Digital Sky Survey. We present measurements of richness, mass and velocity dispersion for the clusters. We find that in order to use the mass-richness relation from Johnston et al. (2007), which was established at mean redshift of 0.25, it is necessary to scale measured richness values up by 1.47. We also present measurements of Einstein radius, mass and velocity dispersion for the lensing systems. The Einstein radii are all relatively small, between 5.4-13 arcseconds. Finally we consider if there is evidence that our clusters are more concentrated than standard cosmology would predict. We find that six of our clusters do not show evidence of overconcentration, while four of our clusters do. We note a correlation between overconcentration and mass, as the four clusters showing evidence of overconcentration are all lower-mass clusters.
160 1 Robert Suhada
161 1 Robert Suhada
http://arxiv.org/abs/1211.1421
162 1 Robert Suhada
163 7 Robert Suhada
Votes: *0*
164 4 Robert Suhada
165 4 Robert Suhada
h2. A low-scatter survey-based mass proxy for clusters of galaxies
166 4 Robert Suhada
167 4 Robert Suhada
S. Andreon (INAF-OABrera)
168 1 Robert Suhada
(Submitted on 5 Nov 2012)
169 4 Robert Suhada
Estimates of cosmological parameters using galaxy clusters have the scatter in the observable at a given mass as a fundamental parameter. This work computes the amplitude of the scatter for a newly introduced mass proxy, the product of the cluster total luminosity times the mass-to-light ratio, usually referred as stellar mass. The analysis of 12 galaxy clusters with excellent total masses shows a tight correlation between the stellar mass, or stellar fraction, and total mass within r500 with negligible intrinsic scatter: the 90% upper limit is 0.06 dex, the posterior mean is 0.027 dex. This scatter is similar to the one of best-determined mass proxies, such as Yx, i.e. the product of X-ray temperature and gas mass. The size of the cluster sample used to determine the intrinsic scatter is small, as in previous works proposing low-scatter proxies because very accurate masses are needed to infer very small values of intrinsic scatter. Three-quarters of the studied clusters have lgM <~14 Msol, which is advantageous from a cosmological perspective because these clusters are far more abundant than more massive clusters. At the difference of other mass proxies such as Yx, stellar mass can be determined with survey data up to at least z=0.9 using upcoming optical near-infrared surveys, such as DES and Euclid, or even with currently available surveys, covering however smaller solid angles. On the other end, the uncertainty about the predicted mass of a single cluster is large, 0.21 to 0.32 dex, depending on cluster richness. This is largely because the proxy itself has ~0.10 dex errors for clusters of lgM<~ 14 Msol mass.
170 4 Robert Suhada
171 4 Robert Suhada
http://arxiv.org/abs/1211.0790
172 4 Robert Suhada
173 7 Robert Suhada
Votes: *1*
174 4 Robert Suhada
175 20 Robert Suhada
*Notes*
176 20 Robert Suhada
* controversial?
177 4 Robert Suhada
178 30 Joseph Mohr
h2. CALCLENS: Weak Lensing Simulations for Large-area Sky Surveys and Second-order Effects in Cosmic Shear Power Spectra
179 32 Joseph Mohr
180 30 Joseph Mohr
Matthew R. Becker (UChicago/KICP)
181 30 Joseph Mohr
(Submitted on 10 Oct 2012 (v1), last revised 12 Oct 2012 (this version, v2))
182 30 Joseph Mohr
I present a new algorithm, CALCLENS, for efficiently computing weak gravitational lensing shear signals from large N-body light cone simulations over a curved sky. This new algorithm properly accounts for the sky curvature and boundary conditions, is able to produce redshift-dependent shear signals including corrections to the Born approximation by using multiple-plane ray tracing, and properly computes the lensed images of source galaxies in the light cone. The key feature of this algorithm is a new, computationally efficient Poisson solver for the sphere that combines spherical harmonic transform and multgrid methods. As a result, large areas of sky (~10, 000 square degrees) can be ray traced efficiently at high-resolution using only a few hundred cores on widely available machines. Using this new algorithm and curved-sky calculations that only use a slower but more accurate spherical harmonic transform Poisson solver, I study the shear B-mode and rotation mode power spectra. Employing full-sky E/B-mode decompositions, I confirm that the shear B-mode and rotation mode power spectra are equal at high accuracy (~1%), as expected from perturbation theory up to second order. Coupled with realistic galaxy populations placed in large N-body light cone simulations, this new algorithm is ideally suited for the construction of synthetic weak lensing shear catalogs to be used to test for systematic effects in data analysis procedures for upcoming large-area sky surveys. The implementation presented in this work, written in C and employing widely available software libraries to maintain portability, is publicly available at this http URL
183 30 Joseph Mohr
184 30 Joseph Mohr
http://arxiv.org/abs/1210.3069
185 30 Joseph Mohr
186 31 Joseph Mohr
Votes: *1*
187 38 Shantanu Desai
188 38 Shantanu Desai
h2. Dark matter mass profiles in the Milky Way and in galaxy clusters support a prior claim of 4.0 eV and 21.4 eV sterile neutrinos
189 38 Shantanu Desai
190 38 Shantanu Desai
Man Ho Chan, Robert Ehrlich
191 38 Shantanu Desai
192 38 Shantanu Desai
In several recent papers it was claimed that SN 1987A data supports the existence of 4.0 eV and 21.4 eV active neutrino mass eigenstates, and it was shown that such large masses could be made consistent with existing constraints including neutrino oscillation data and upper limits on the neutrino flavor state masses, provided that there also exist a pair of sterile neutrino mass states whose masses are nearly degenerate with the active ones, plus a third active-sterile doublet that is tachyonic ($m^2 <0$). Here, independent evidence is presented for the existence of sterile neutrinos with the previously claimed masses based on fits to the dark matter distributions in the Milky Way galaxy and four clusters of galaxies. The fits are in excellent agreement with observations. In addition, sterile neutrinos having the suggested masses address the "cusp" problem and the missing satellites problem, as well as that of the "top down" scenario of structure formation -- previously a chief drawback of HDM particles. Nevertheless, the highly controversial nature of the claim, and the need for two free parameters in the dark matter fits, additional confirming evidence will be required before it can be considered proven.
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