The LX-sigma Relation for Galaxies and Clusters of Galaxies

We demonstrate that individual elliptical galaxies and clusters of galaxies form a continuous X-ray luminosity---velocity dispersion (LX-sigma) relation. Our samples of 280 clusters and 57 galaxies have LX ~ sigma^4.4 and LX ~ sigma^10, respectively. This unified LX - sigma relation spans 8 orders of magnitude in LX and is fully consistent with the observed and theoretical luminosity---temperature scaling laws. Our results support the notion that galaxies and clusters of galaxies are the luminous tracers of similar dark matter halos.Comment: 11 pages, including 2 tables and 2 figures. Accepted for publication in The Astrophysical Journal Letters; the Letters version excludes Table 1, which is available in ASCII format at http://tdc-www.harvard.edu/lxsigm

XMM-Newton and Gemini Observations of Eight RASSCALS Galaxy Groups

We study the distribution of gas pressure and entropy in eight groups of galaxies belonging to the ROSAT All-Sky Survey / Center for Astrophysics Loose Systems (RASSCALS). We use archival and proprietary XMM-Newton observations, supplementing the X-ray data with redshifts derived from the literature; we also list 127 new redshifts measured with the Gemini North telescope. The groups show remarkable self-similarity in their azimuthally averaged entropy and temperature profiles. The entropy increases with radius; the behavior of the entropy profiles is consistent with an increasing broken power law with inner and outer slope 0.92+0.04-0.05 and 0.42+0.05-0.04 (68% confidence), respectively. There is no evidence of a central, isentropic core, and the entropy distribution in most of the groups is flatter at large radii than in the inner region, challenging earlier reports as well as theoretical models predicting large isentropic cores or asymptotic slopes of 1.1 at large radii. The pressure profiles are consistent with a self-similar decreasing broken power law in radius; the inner and outer slopes are -0.78+0.04-0.03 and -1.7+0.1-0.3, respectively. The results suggest that the larger scatter in the entropy distribution reflects the varied gasdynamical histories of the groups; the regularity and self-similarity of the pressure profiles is a sign of a similarity in the underlying dark matter distributions.Comment: Accepted for publication in the Astrophysical Journa

Mass Profile of the Infall Region of the Abell 2199 Supercluster

Using a redshift survey of 1323 galaxies (1092 new or remeasured) in a region of 95 square degrees centered on the nearby galaxy cluster Abell 2199, we analyze the supercluster containing A2199, A2197, and an X-ray group. The caustic technique accurately reproduces the true mass profiles of simulated simple superclusters (i.e., superclusters where the virial mass of one cluster is 2-10 times the virial mass of all other clusters in the supercluster). We calculate the masses of the two main components of A2197 (A2197W and A2197E) using archival X-ray observations and demonstrate that the A2199 supercluster is simple and thus that the caustic technique should yield an accurate mass profile. The mass profile is uncertain by ~30% within 3 Mpc/h and by a factor of two within 8 Mpc/h and is one of only a few for a supercluster on such large scales. Independent X-ray mass estimates agree with our results at all radii where they overlap. The mass profile strongly disagrees with an isothermal sphere profile but agrees with profiles suggested by simulations. We discuss the interplay of the supercluster dynamics and the dynamics of the bound subclusters. The agreement between the infall mass profile and other techniques shows that the caustic technique is surprisingly robust for simple superclusters (abridged).Comment: 49 pages, 20 figures, to appear in The Astronomical Journal, version containing high-resolution figures available at http://cfa-www.harvard.edu/~krines/a2199mp.p

Joint Analysis of Cluster Observations: II. Chandra/XMM-Newton X-ray and Weak Lensing Scaling Relations for a Sample of 50 Rich Clusters of Galaxies

We present a study of multiwavelength X-ray and weak lensing scaling relations for a sample of 50 clusters of galaxies. Our analysis combines Chandra and XMM-Newton data using an energy-dependent cross-calibration. After considering a number of scaling relations, we find that gas mass is the most robust estimator of weak lensing mass, yielding 15 +/- 6% intrinsic scatter at r500 (the pseudo-pressure YX has a consistent scatter of 22%+/-5%). The scatter does not change when measured within a fixed physical radius of 1 Mpc. Clusters with small BCG to X-ray peak offsets constitute a very regular population whose members have the same gas mass fractions and whose even smaller <10% deviations from regularity can be ascribed to line of sight geometrical effects alone. Cool-core clusters, while a somewhat different population, also show the same (<10%) scatter in the gas mass-lensing mass relation. There is a good correlation and a hint of bimodality in the plane defined by BCG offset and central entropy (or central cooling time). The pseudo-pressure YX does not discriminate between the more relaxed and less relaxed populations, making it perhaps the more even-handed mass proxy for surveys. Overall, hydrostatic masses underestimate weak lensing masses by 10% on the average at r500; but cool-core clusters are consistent with no bias, while non-cool-core clusters have a large and constant 15-20% bias between r2500 and r500, in agreement with N-body simulations incorporating unthermalized gas. For non-cool-core clusters, the bias correlates well with BCG ellipticity. We also examine centroid shift variance and and power ratios to quantify substructure; these quantities do not correlate with residuals in the scaling relations. Individual clusters have for the most part forgotten the source of their departures from self-similarity.Comment: Corrects an error in the X-ray luminosities (erratum submitted)---none of the other results are affected. Go to http://sfstar.sfsu.edu/jaco for an electronic fitter and updated quick data download link

The Orbital Structure of Dark Matter Halos with Gas

With the success of the Chandra and XMM missions and the maturation of gravitational lensing techniques, powerful constraints on the orbital structure of cluster dark matter halos are possible. I show that the X-ray emissivity and mass of a galaxy cluster uniquely specify the anisotropy and velocity dispersion profiles of its dark matter halo. I consider hydrostatic as well as cooling flow scenarios, and apply the formalism to the lensing cluster CL0024+16 and the cooling flow cluster Abell 2199. In both cases, the model predicts a parameter-free velocity dispersion profile that is consistent with independent optical redshift surveys of the clusters.Comment: 17 pages, 12 figures; to appear in the Astrophysical Journa

A Comparative Analysis of IELTS and TOEFL in an Iranian Context: A Case Study of Washback of Standard Tests

Having desired results represents a type of success on what the teachers and the learners have been working on. In order to obtain the correlation of the standard tests of IELTS and TOEFL 120 applicants have been selected. They were grouped under IELTS study phase and non-IELTS study group and also TOEFL study group and non-TOEFL study group. The applicants were at C1, C2, and B2 level of CEFR in the first group and Advanced and intermediate high of ACTFL Proficiency Guidelines. The applicants received treatment and took six tests along with a pretest and a post test. Therefore, there were four groups in the study as receiving the treatment and the placebo thereof.  Besides, the applicants were interviewed in order to get their ideas and personal attitudes to the success or failure of standard exams. In order to do so a questionnaire was developed and its reliability and validity was gauged. The results of the testing procedure represents more plausible scores on IELTS test results. This could be attributed to the recent trend among Iranian graduate and post graduate learners to IELTS exam. The results of the total study reveals the idea of teaching to the test and studying for the test which verifies the washback of the tests and reflects washback on teaching and learning

A Study of the Dark Core in A520 with Hubble Space Telescope: The Mystery Deepens

We present a Hubble Space Telescope/Wide Field Planetary Camera 2 weak-lensing study of A520, where a previous analysis of ground-based data suggested the presence of a dark mass concentration. We map the complex mass structure in much greater detail leveraging more than a factor of three increase in the number density of source galaxies available for lensing analysis. The "dark core" that is coincident with the X-ray gas peak, but not with any stellar luminosity peak is now detected with more than 10 sigma significance. The ~1.5 Mpc filamentary structure elongated in the NE-SW direction is also clearly visible. Taken at face value, the comparison among the centroids of dark matter, intracluster medium, and galaxy luminosity is at odds with what has been observed in other merging clusters with a similar geometric configuration. To date, the most remarkable counter-example might be the Bullet Cluster, which shows a distinct bow-shock feature as in A520, but no significant weak-lensing mass concentration around the X-ray gas. With the most up-to-date data, we consider several possible explanations that might lead to the detection of this peculiar feature in A520. However, we conclude that none of these scenarios can be singled out yet as the definite explanation for this puzzle.Comment: Published in ApJ. Figures are slightly degraded to meet the size limi

An adaptive Neuro-Fuzzy controller for maximum power point tracking of photovoltaic systems

© 2015 IEEE. This paper presents a high performance tracking method for maximum power generated by photovoltaic (PV) systems. Based on adaptive Neuro-Fuzzy inference systems (ANFIS), this method combines the learning abilities of artificial neural networks and the ability of fuzzy logic to handle imprecise data. It is able to handle non-linear and time varying problems hence making it suitable for accurate maximum power point tracking (MPPT) to ensure PV systems work effectively. The performance of the proposed method is compared to that of a fuzzy logic based MPPT algorithm to demonstrate its effectiveness

The feasibility and benefits of using high-strength concrete for construction purposes in earthquake prone areas

In recent years, concrete technology has benefited from great advances and evolutions that lead to emergence of new concrete with different properties. One of the most important of these concretes is high strength concrete (HSC). The emergence of HSC has made possible to high-rise buildings and towers with architectural art and delicacy and it is expected that in the next few years, there is the possibility of using HSC in wider areas. Examining the studies on this type of concrete, this paper has deal with the feasibility and benefits of using HSC for construction purposes in earthquake prone areas. The results of this study show that in case of respecting the bylaw constrains and conformity of new bylaws with this type of concrete, it is hoped to use it as a reliable option for safe construction in seismic areas.Keywords: Concrete, High-Strength, Construction, Seismic Area, Feasiblit