Studying the properties of galaxy cluster morphology estimators

X-ray observations of galaxy clusters reveal a large range of morphologies with various degrees of disturbance, showing that the assumptions of hydrostatic equilibrium and spherical shape which are used to determine the cluster mass from X-ray data are not always satisfied. It is therefore important for the understanding of cluster properties as well as for cosmological applications to detect and quantify substructure in X-ray images of galaxy clusters. Two promising methods to do so are power ratios and center shifts. Since these estimators can be heavily affected by Poisson noise and X-ray background, we performed an extensive analysis of their statistical properties using a large sample of simulated X-ray observations of clusters from hydrodynamical simulations. We quantify the measurement bias and error in detail and give ranges where morphological analysis is feasible. A new, computationally fast method to correct for the Poisson bias and the X-ray background contribution in power ratio and center shift measurements is presented and tested for typical XMM-Newton observational data sets. We studied the morphology of 121 simulated cluster images and establish structure boundaries to divide samples into relaxed, mildly disturbed and disturbed clusters. In addition, we present a new morphology estimator - the peak of the 0.3-1 r500 P3/P0 profile to better identify merging clusters. The analysis methods were applied to a sample of 80 galaxy clusters observed with XMM-Newton. We give structure parameters (P3/P0 in r500, w and P3/P0_max) for all 80 observed clusters. Using our definition of the P3/P0 (w) substructure boundary, we find 41% (47%) of our observed clusters to be disturbed.Comment: Replaced to match version published in A&A, Eq. 1 correcte

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

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

Jungle Travel

The following is a study prepared so that I, Jorge Ameglio, can open a full service travel agency in Miami named Jungle Travel (Jungle) focusing on tourism to Panama. I will show here that it can be profitable, not only for investors and myself, but also for my country, Panama. I plan to demonstrate the feasibility and the need for a business such as this one. Now, I ask, can Jungle become operational with a fair-sized initial investment of $150,000.00? Likewise, the problem that lies herein, is whether there is an economic and business viability in establishing a travel agency that specializes in travel and vacations primarily towards Panama. The purpose of centering Jungle on Panama is partially because it is located only two and half hours away by air. Another important reason for me, a Panamanian, is that by encouraging tourism towards Panama, will not only bring foreign currency into the area, thus helping the development of underdeveloped regions, but will also improve the level of lie for its people through new jobs, diversify the use of the country\u27s resources, and inspire economic development in order to accommodate tourism. Currently, Panama City is the only truly developed city within the country\u27s borders leaving vast areas of prime location and substantial natural resources awaiting to be cultivated by touristic locals and foreign investments, something the Panamanian Tourism Institute (IPAT) is trying to promote. Though Jungle will be serving as a full service agency to all destinations, its primary emphasis will be that of promoting tourism to Panama. As stated by Jon P. Goodman, director of the University of Southern California Entrepreneur Program, Successful entrepreneurs don\u27t have failure. They do have learning experiences.. . The first crucial sign I\u27ve learned to look for is passion.. .Successful entrepreneurs also have imagination.. .a crucial sign I look for is self-determination (Goodman, p.29). Well, I, Jorge Ameglio, will see this first enterprise as a learning experience for future growth. I, too, have a passion to complete this project in order to benefit financially and to benefit my country. I am determined to see it through. It seems that I am not the only one interested in developing tourism. World organizations such as the Organization of American States and the United Nations Organization work on plans and give direction so that countries in development, such as Panama, organize their tourism sector, in order to solve their economic problems. (Villa, p.3G). The following translation is of a full page editorial published in El Panama America, a Panamanian newspaper, on the 7th of January, 1996. It states: Panama is following this plan and is developing a strong and coherent effort, accomplished by joining both the private and government sectors in order to achieve touristic goods. Examples of these efforts are the internationally publicized activities such as The Turistic Caravans, (which are tours throughout provinces in Panama). Also, the holding of international meetings for people involved in tourism, such as the Travel Mart, both realities promoted by Panama. The construction of new hotels, such as the Riande Continental, the Hotel Marina, and the new Marriot. Another example is the effort to start tourist projects on the beaches to serve as a starting point to place Panama as a \u27beach Tourist Destination\u27 . which will help Panama become an important \u27Tourist Destination \u27 (Villa, p.3G). With the inspiration of the Panamanian government and that brought forth through my desire to help my country, I can partially arrive at my goal. Both these incentives will be stepping stones to complete the hard but accomplishable objective. Nevertheless, nothing, not even a flower will bloom with desire. It takes effort, determination, and resistance, along with finds, personality, and devotion, to accomplish a successful self owned business. That is what this project is about. Its about Jungle Travel

Joint deprojection of Sunyaev-Zeldovich and X-ray images of galaxy clusters

We present two non-parametric deprojection methods aimed at recovering the three-dimensional density and temperature profiles of galaxy clusters from spatially resolved thermal Sunyaev-Zeldovich (tSZ) and X-ray surface brightness maps, thus avoiding the use of X-ray spectroscopic data. In both methods, clusters are assumed to be spherically symmetric and modeled with an onion-skin structure. The first method follows a direct geometrical approach. The second method is based on the maximization of a single joint (tSZ and X-ray) likelihood function, which allows one to fit simultaneously the two signals by following a Monte Carlo Markov Chain approach. These techniques are tested against a set of cosmological simulations of clusters, with and without instrumental noise. We project each cluster along the three orthogonal directions defined by the principal axes of the momentum of inertia tensor. This enables us to check any bias in the deprojection associated to the cluster elongation along the line of sight. After averaging over all the three projection directions, we find an overall good reconstruction, with a small (<~10 per cent) overestimate of the gas density profile. This turns into a comparable overestimate of the gas mass within the virial radius, which we ascribe to the presence of residual gas clumping. Apart from this small bias the reconstruction has an intrinsic scatter of about 5 per cent, which is dominated by gas clumpiness. Cluster elongation along the line of sight biases the deprojected temperature profile upwards at r<~0.2r_vir and downwards at larger radii. A comparable bias is also found in the deprojected temperature profile. Overall, this turns into a systematic underestimate of the gas mass, up to 10 percent. (Abridged)Comment: 17 pages, 15 figures, accepted by MNRA

Cluster Morphologies and Model-independent Y_(SZ) Estimates from Bolocam Sunyaev-Zel'dovich Images

We present initial results from our ongoing program to image the Sunyaev-Zel'dovich (SZ) effect in galaxy clusters at 143 GHz using Bolocam; five clusters and one blank field are described in this manuscript. The images have a resolution of 58 arcsec and a radius of ≃ 6-7 arcmin, which is approximately r_(500)-2r_(500) for these clusters. We effectively high-pass filter our data in order to subtract noise sourced by atmospheric fluctuations, but we are able to obtain unbiased images of the clusters by deconvolving the effects of this filter. The beam-smoothed rms is ≃ 10 μK_(CMB) in these images; with this sensitivity, we are able to detect the SZ signal to beyond r_(500) in binned radial profiles. We have fit our images to beta and Nagai models, fixing spherical symmetry or allowing for ellipticity in the plane of the sky, and we find that the best-fit parameter values are in general consistent with those obtained from other X-ray and SZ data. Our data show no clear preference for the Nagai model or the beta model due to the limited spatial dynamic range of our images. However, our data show a definitive preference for elliptical models over spherical models, quantified by an F ratio of ≃ 20 for the two models. The weighted mean ellipticity of the five clusters is ϵ = 0.27 ± 0.03, consistent with results from X-ray data. Additionally, we obtain model-independent estimates of Y_(500), the integrated SZ y-parameter over the cluster face to a radius of r_(500), with systematics-dominated uncertainties of ≃ 10%. Our Y_(500) values, which are free from the biases associated with model-derived Y_(500) values, scale with cluster mass in a way that is consistent with both self-similar predictions and expectations of a ≃ 10% intrinsic scatter

Reconstructing mass profiles of simulated galaxy clusters by combining Sunyaev-Zeldovich and X-ray images

We present a method to recover mass profiles of galaxy clusters by combining data on thermal Sunyaev-Zeldovich (tSZ) and X-ray imaging, thereby avoiding to use any information on X-ray spectroscopy. This method, which represents a development of the geometrical deprojection technique presented in Ameglio et al. (2007), implements the solution of the hydrostatic equilibrium equation. In order to quantify the efficiency of our mass reconstructions, we apply our technique to a set of hydrodynamical simulations of galaxy clusters. We propose two versions of our method of mass reconstruction. Method 1 is completely model-independent, while Method 2 assumes instead the analytic mass profile proposed by Navarro et al. (1997) (NFW). We find that the main source of bias in recovering the mass profiles is due to deviations from hydrostatic equilibrium, which cause an underestimate of the mass of about 10 per cent at r_500 and up to 20 per cent at the virial radius. Method 1 provides a reconstructed mass which is biased low by about 10 per cent, with a 20 per cent scatter, with respect to the true mass profiles. Method 2 proves to be more stable, reducing the scatter to 10 per cent, but with a larger bias of 20 per cent, mainly induced by the deviations from equilibrium in the outskirts. To better understand the results of Method 2, we check how well it allows to recover the relation between mass and concentration parameter. When analyzing the 3D mass profiles we find that including in the fit the inner 5 per cent of the virial radius biases high the halo concentration. Also, at a fixed mass, hotter clusters tend to have larger concentration. Our procedure recovers the concentration parameter essentially unbiased but with a scatter of about 50 per cent.Comment: 13 pages, 11 figures, submitted to MNRA

Lamasquère – La Tourasse

Identifiant de l'opération archéologique : Date de l'opération : 1987 - 1989 (SU) Inventeur(s) : Ameglio Henri À proximité de la ferme actuelle de La Tourasse, le cadastre de 1832 indique un fossé en eau de 8 m à 10 m de large, mentionné comme vivier, qui entoure une parcelle légèrement trapézoïdale de 40 m de long sur 20 m de large environ. Cette pièce de terre présente un plan plus proche du carré sur le cadastre de 1948, encore entouré de fossés : ceux-ci, largement comblés depuis, n'exis..

Depresión: una perspectiva psicoanalítica

La depresión supone el duelo, esto es, el dolor psíquico que acompaña las separaciones y pérdidas. El proceso subsiguiente a la pérdida de un objeto, por el cual el sujeto logra desligarse progresivamente de él, se conoce como trabajo de duelo, actividad cuyo fracaso constituye el duelo patológico. Con el fin de indagar en las posibles causas del duelo patológico, el autor describe, en primer término, el proceso de trabajo de duelo. Siguiendo a Bleichmar, distigue entre depresión narcisista y depresión culposa, y profundiza luego en el estatuto de los sentimientos de culpa, diferenciando la culpa persecutoria de la culpa depresiva. No existe un único tratamiento éticas de la depresión, sino que éste deberá adaptarse al tipo de depresión en particular

Angular diameter distance estimates from the Sunyaev-Zel'dovich effect in hydrodynamical cluster simulations

The angular-diameter distance D_A of a galaxy cluster can be measuread by combining its X-ray emission with the cosmic microwave background fluctution due to the Sunyaev-Zeldovich effect. The application of this distance indicator usually assumes that the cluster is spherically symmetric, the gas is distributed according to the isothermal beta-model, and the X-ray temperature is an unbiased measure of the electron temperature. We test these assumptions with galaxy clusters extracted from an extended set of cosmological N-body/hydrodynamical simulations of a LCDM concordance cosmology, which include the effect of radiative cooling, star formation and energy feedback from supernovae. We find that, due to the steep temperature gradients which are present in the central regions of simulated clusters, the assumption of isothermal gas leads to a significant underestimate of D_A. This bias is efficiently corrected by using the polytropic version of the beta-model to account for the presence of temperature gradients. In this case, once irregular clusters are removed, the correct value of D_A is recovered with a ~ 5 per cent accuracy on average, with a ~ 20 per cent intrinsic scatter due to cluster asphericity. This result is valid when using either the electron temperature or a spectroscopic-like temperature. When using instead the emission-weighted definition for the temperature of the simulated clusters, D_A is biased low by \~ 20 per cent. We discuss the implications of our results for an accurate determination of the Hubble constant H_0 and of the density parameter Omega_m. We find that H_0 can be potentially recovered with exquisite precision, while the resulting estimate of Omega_m, which is unbiased, has typical errors Delta(Omega_m) ~ 0.05.Comment: 12 pages, 10 figures, accepted by MNRAS, replaced to match accepted versio

Using hydrodynamical simulations to combine Sunyaev-Zeldovich and X-ray studies of galaxy clusters

2006/2007The main focus of the work presented in this Thesis is the study of the potentiality and possible systematics in combining observations of the thermal Sunyaev-Zeldovich effect (tSZ) and of the X–ray emission in galaxy clusters. The great advantage of the combination of this two types of observations is that they have a different dependence on the properties (density and temperature) of the Intra Cluster Medium (ICM). Also the behavior with redshift is completely different: X–rays provide very bright images of nearby clusters, but decline rapidly with redshift, while the tSZ signal is independent of redshift and is more suitable for observations of distant objects. At present, the X–ray data have far better resolution than the tSZ ones. For this reason, our attention is mainly directed to the present and upcoming generation of tSZ telescopes, which should produce high resolution images. In this perspective, we analyze a sample of galaxy clusters extracted from a set of cosmological hydrodynamical simulations, which have been carried out with the GADGET-2 code. These simulations include the effects of radiative cooling, star formation and supernovae feedback and, as such, they provide a realistic description of the ICM.A widely adopted technique to measure the angular diameter distance of galaxy clusters is based on the combination of X–ray and tSZ observations (e.g. Bonamente et al., 2006). The method is completely independent of any other distance ladder and provides a measure of the Hubble constant out to z ~ 1. We study the systematics of this type of measure through the analysis of simulated clusters. The ICM is usually modelled with an isothermal beta-model. We find that this model does not provide a satisfactory description of our simulated clusters. In order to take into account the presence of temperature gradients, we instead introduce a polytropic equation of state. Our results show that the distance is correctly recovered, with an intrinsic scatter of about 20% which we attribute to cluster asphericities. Finally, we generate a redshift distribution of our clusters in order to test the capabilities of this technique in recovering the cosmological parameters. We first find that the Hubble constant is correctly recovered with an uncertainty of only 2%. Then, we assume a prior for the Hubble constant and a flat geometry. We find that extending this type of measure out to z ~ 1.5 with future datasets would allow to recover also the density parameter Omega_m with a typical error of about 0.05.Galaxy clusters are interesting not only as cosmological probes, but also as virialized structures which are the result of a long and complex formation process. Their study has implications on both the thermodynamical processes ongoing in the hot ICM plasma and on the cosmological models of structure formation. Given the poor resolution of past tSZ telescopes, the principal source of information on the structure of the ICM comes from X–ray data, for which both imaging and spectroscopy are available. In the perspective of having new high-resolution tSZ images, we propose a technique aiming at reconstructing gas density and temperature by combining them with the X–ray images, without the need of X–ray spectroscopy which is a potential source of biases in the measure of the ICM temperature. The method is based on a joint deprojection of tSZ and X–ray images and requires the only assumption of spherical symmetry. Gas density (rho) and temperature (T) can be recovered by taking advantage of the different dependence of the two signals on gas properties: tSZ ~ rho*T, while X–ray ~ int rho^2 Lambda(T), where Lambda(T) is the cooling function at X–ray energies. Our technique implements the deprojection by following a Markov Chain Monte Carlo approach, which allows us to deproject both images simultaneously, by the maximization of a joint (tSZ + X–ray) likelihood function. From this method, we obtain at the same time an accurate estimate of the uncertainty on the recovered profiles of density and temperature, along with an analysis of all degeneracies. A typical feature of geometrical deprojection is to introduce spurious fluctuations in the profiles, which are due to the presence of noise. The effect increases rapidly when reducing the width of the bins adopted in the deprojection. Our statistical approach instead allows us to introduce a regularization constraint which has the effect of smoothing out these spurious fluctuations, thus offering a much more stable reconstruction of the gas properties.We first apply the whole procedure to an ideal model cluster, realized by assuming a polytropic beta–model. We find that density and temperature are recovered unbiased, with errors of < 5% and about 20% respectively. On the simulated clusters we find a general overestimate of density from 5 to 10%, which we attribute to small-scale inhomogeneities and to small unresolved gas clumps which cause a boosting of the X–ray surface brightness. As a consequence the temperature is slightly underestimated. By integrating the density profile one directly obtains the gas mass content of the cluster. Together with an estimate of the total mass, it allows us to measure the gas mass fraction, which is another important constrain on cosmological models. Since the density within each shell depends on the density of all the other shells, it is important to have an estimate of the full covariance matrix, which is naturally provided by the Markov Chain Monte Carlo method. We find that the gas mass is also overestimated by about 5-10%, with a statistical uncertainty of about 5%. A common way to select samples of clusters is to fix a lower limit in their X–ray luminosity. This criterion may slightly favor objects which are elongated along the line of sight. This represents a potential source of bias when these samples are used for a statistical analysis of cluster properties. In fact, we find that cluster elongation along the line of sight causes a systematic underestimate of the gas mass by up to 10%.Correctly measuring the total cluster mass is of fundamental importance for clusters to be used as tools for precision cosmology. In cluster studies based on the observations of the ICM the mass is obtained by assuming that the gas lies in hydrostatic equilibrium in the cluster gravitational potential. We implemented the solution of the hydrostatic equilibrium equation in the deprojection algorithm, so as to derive profiles of gas density and temperature and total mass simultaneously. In practice, this involves a derivative of gas density and temperature profiles, for which our regularization constraint is quite useful. However, deviations from such equilibrium are expected, due to any non–thermal pressure support (e.g. stochastic velocity fields, turbulence, residual bulk motions). As a consequence, we find the mass to be systematically underestimated by a factor of 10% (in agreement with findings from other authors). In order to better characterize the sources of systematics in the mass measurement, we also compute the hydrostatic mass profile, which is obtained by applying the hydrostatic equilibrium equation to the true gas density and temperature profiles, given by the simulation data. We find that our reconstructed mass profiles are generally close to hydrostatic mass profiles, thus confirming that the main source of systematics is intrinsic (i.e. the non–thermal pressure support), while our procedure is basically unbiased.To summarize, in the work presented in this Thesis we use hydrodynamical cosmological simulations to study combined tSZ/X–ray observations, by following two different perspectives. The first makes use of galaxy clusters as distance indicators to probe the geometry of the Universe. We study systematics and future capabilities of this technique, which has been widely adopted with datasets extending out to z ~ 1. The second aims at a detailed characterization of cluster properties, which are relevant to both understand of the ICM physics and calibrate galaxy clusters as precision tools for cosmology. We develope a maximum–likelihood deprojection technique which allows us to recover the three–dimensional profiles of gas density and temperature and of total mass, which is completely model–independent.XX Ciclo198