Detailed surface photometry of the cD galaxies NGC 4839 and NGC 4874

We present a detailed photometric study of the cD galaxies NGC 4839 and NGC 4874 based on the technique of surface photometry by fitting ellipses to the isophotes of the galaxies in the u, g, r, i, and z bands using Data Release 7 (DR7) of the Sloan Digital Sky Survey (SDSS). The motivation of this paper is to study the properties (e.g. break radius and surface brightness, color gradient, etc.) of the extended envelope of the two cD galaxies. The surface brightness profile in each band is obtained and fitted to the de Vaucouleurs r ^1/4 model. A deviation of the observed profile brighter than the fitted r ^1/4 model is noticed especially in the outer part of each galaxy. The profiles of ellipticity, position angle, B4 and shifts with respect to the center of each isophote are also obtained. The color index profiles, u-g, g-r, r-i, and i-z are also obtained and no significant color gradients are noticed except in the outer parts of the two galaxies. The integrated magnitude in each band and color indices are obtained and found to be in good agreement with the published ones.     

Mass Estimation in the Globular Cluster M4

Using the kinematical data we try to solve the Jeans equation to provide mass estimation of the globular cluster M4. The proper motion data provides two independent velocity dispersion profiles which we need in this estimation. Moreover, we have calculated the density distribution function and checked the anisotropy of the velocity dispersion. The comparison of the dynamical mass with the estimation stellar mass for M4 gives the best estimation of the mass inside a spherical shell centered on the cluster, with a radius corresponding to 840 arcsec on the sky, as 4-5× 10⁴ M . This revised version was published online in July 2006 with corrections to the Cover Date.     

Escape Of Planetary Atmospheres Including The Effects Of Rotation And Orbital Motion Of The Planet

The problem of escape of planetary atmospheres is discussed taking into account the effects of planet's rotation and planet's orbital momentum. The expressions for the rates of loss of mass and angular momentum per unit area and the total rates of loss of mass and angular momentum for the whole planetary surface are obtained. These expressions are, then, applied to study the escape of the constituents of the atmospheres of Mars and Venus. This revised version was published online in July 2006 with corrections to the Cover Date.