Correlation functions for pairs and groups of galaxies

There are many studies on the correlation functions of galaxies, of clusters of galaxies, even of superclusters (e.g., Groth and Peebles 1977; Davies and Peebles 1983; Kalinkov and Kuneva 1985, 1986; Bahcall 1988 and references therein) but not so many on pairs and groups of galaxies. Results of the calculations of two-point correlation fuctions for some catalogs of pairs and groups of galaxies are given. It is assumed that the distances to pairs and groups of galaxies are given by their mean redshifts according to R = sigma (sup n, sub i-1) V sub i/nH (sub 0), where n is the number of galaxies in the system and H sub 0 = 100 km s(exp -1) Mpc(exp -1)

Astigmatism management during cataract surgery

Цел: да обсъдим и споделим нашия опит при интраоперативната корекция на роговичния астигматизъм по време на катарактна хирургия. Методи: В проучването са включени 48 пациенти с различна степен на роговичен астигматизъм, разделени в две групи. Подборът на метода на корекция на астигматизма беше направен на база на степента на астигматизма след изследване на роговицата с корнеален топограф и томограф. Пациентите с роговичен астигматизъм до 2,5 Д -38 очи третирахме с АК (аркуатни кератотомии), извършени с B&L VICTUS Femtosecond Laser P1atform , при останалите 11 очи имплантирахме торична вътреочна леща. Проследихме пациентите за период от 18 месеца постоперативно. Резултати: И в двете групи получихме желаната корекция на астигматизма постоперативно, В първата група редукцията на астигматизма беше средно 1, 71 dpt ± 0,63 (SD) до 0,28 ± 0,39 (РObjective: To share our experience in correcting corneal astigmatism in patients undergoing cataract surgery. Methods: Our study includes 48 eyes, 37 eyes with a corneal astigmatism of up to 2.50 dpt and 11 eyes with a higher (>2.50dpt) astigmatism. The first group was treated with arcuate keratotomies (AK) performed by B&L VICTUS Femtosecond Laser Platform. The AKs were placed on the steepest corneal meridian in a resulting depth of 85% based on the real-time OCT pachymetry. Patients from group 2 were treated with intraocular toric IOLs. Postsurgical follow-up period was 18 months and includes uncorrected visual acuity, manifest refraction, count and density of endothelial corneal cells prior to and after surgery, pachymetry, corneal topography (Placidobased and Scheimpflug image -derived topography). Results: - The mean astigmatismus reduction in the first group was from 1.71 D ± 0.63 (SD) to 0.28 ± 0.39 D (

Rotation of the cluster of galaxies A2107

We present indications of rotation in the galaxy cluster A2107 by a method that searches for the maximum gradient in the velocity field in a flat disk-like model of a cluster. Galaxies from cumulative sub-samples containing more and more distant members from the cluster centre, are projected onto an axis passing through the centre and we apply a linear regression model on the projected distances $x$ and the line-of-sight velocities $V$. The axis with the maximum linear correlation coefficient $r_{max} = \max [ r(V,x) ]$ defines the direction of the maximum velocity gradient, and consequently it presents the major axis of the apparently elliptical cluster. Because the effects of rotation are subtle, we put strong emphasis on the estimation of the uncertainties of the results by implementing different bootstrap techniques. We have found the rotational effects are more strongly expressed from distances $0.26 \div 0.54$ Mpc from the cluster centre. The total virial mass of the cluster is (3.2\pm0.6)\times10^{14} {\cal M}_{\sun}, while the virial mass, corrected for the rotation, is (2.8\pm0.5) \times 10^{14}{\cal M}_{\sun}.Comment: 7 pages, 9 figures gzipped tar file. to be published in MNRA

Comparison of Simulated and Observed Density Profiles in Galaxy Clusters

Introduction We have undertaken a detailed study of density profiles of compact groups of galaxies and rich clusters of galaxies. Some preliminary results will be presented here. We attack two problems in the study -- how to define a quantity connected with the density profiles of the Hickson compact groups (HCG) and how to verify the existence of the secondary maxima in density profiles of some rich clusters of galaxies. We assume H 0 = 100 km/s/Mpc. 2 Density profiles of HCG It is very difficult if possible to define any radial distribution of galaxies in groups, especially for the compact ones. Our effort leads to a proposal to use only one median characteristic r mm . Supposing M=L = const for HCG galaxies we estimate weighted group centers and define the median distance r m to the center of each group. Then a median distance r mm o