We model the polarized thermal dust emission from protostellar cores that are assembled by super-sonic turbulent flows in molecular clouds. Self-gravitating cores are selected from a three dimensional simulation of super-sonic and super-Alfvenic magneto-hydrodynamic (MHD) turbulence. The polarization is computed in two ways. In model A it is assumed that dust properties and grain alignment efficiency are uniform; in model B it is assumed that grains are not aligned at visual extinction larger than 3 mag. The main results of this work are: i) Values of the degree of polarization P between 1 and 10% are typical, despite the super-Alfvenic nature of the turbulence; ii) A steep decrease of P with increasing values of the sub-mm dust continuum intensity I is always found in self--gravitating cores selected from the MHD simulations, if grains are not aligned above a certain value of visual extinction (model B); iii) The same behavior is hard to reproduce if grains are aligned independently of visual extinction (model A); iv) The Chandrasekhar-Fermi formula, corrected by a factor f=0.4, provides an approximate estimate of the average magnetic field strength in the cores. Sub-mm dust continuum polarization maps of quiescent protostellar cores and Bok globules always show a decrease in P with increasing value of I consistent with the predictions of our model B. We therefore conclude that sub-mm polarization maps of quiescent cores do not map the magnetic field inside the cores at visual extinction larger than approximately 3 mag. There is no inconsistency between the results from optical and near-IR polarized absorption of background stars, and the observed polarization of sub-mm dust continuum from quiescent cores. In both cases, grains at large visual extinction appear to be virtually unaligned.Comment: 21 pages, color figures, submitted to Ap

We present numerical calculations of the equation of state for dense matter in high magnetic Ðelds, using a temperature-dependent Thomas-Fermi theory with a magnetic Ðeld that takes all Landau levels into account. Free energies for atoms and matter are also calculated, as well as proÐles of the electron density as a function of distance from the atomic nucleus for representative values of the magnetic Ðeld strength, total matter density, and temperature. The Landau shell structure, which is so prominent in cold dense matter in high magnetic Ðelds, is still clearly present at Ðnite temperature as long as it is less than approximately 1/10 of the cyclotron energy. This structure is reÑected in an oscillatory behavior of the equation of state and other thermodynamic properties of dense matter and hence also in proÐles of the density and pressure as functions of depth in the surface layers of magnetic neutron stars. These oscillations are completely smoothed out by thermal e †ects at temperatures of the order of the cyclotron energy or higher.

Abstract. We estimate the total mass distribution of the galaxy cluster CL0024+1654 from the measured source depletion due to lens magnification in the R band. Within a radius of 0.54 h −1 Mpc, a total projected mass of (8.1 ± 3.2) × 10 14 h −1 M (EdS) is measured. The 1σ error here includes shot noise, source clustering, uncertainty in background count normalisation and contamination from cluster and foreground galaxies. This corresponds to a mass-to-light ratio of M/LB = 470 ± 180. We compute the luminosity function of CL0024+1654 in order to estimate contamination of the background source counts from cluster galaxies. Three different magnificationbased reconstruction methods are employed: 1) an estimator method using a local calculation of lens shear; 2) a non-local, self-consistent method applicable to axi-symmetric mass distributions; 3) a non-local, self-consistent method for derivation of 2D mass maps. We have modified the standard single power-law slope number count theory to incorporate a break and applied this to our observations. Fitting analytical magnification profiles of different cluster models to the observed number counts, we find that CL0024+1654 is best described either by a NFW model with scale radius rs = 334 ± 191 h −1 kpc and normalisation κs = 0.23 ± 0.08 or a power-law profile with slope ξ = 0.61 ± 0.11, central surface mass density κ0 = 1.52 ± 0.20 and assuming a core radius of rcore = 35 h −1 kpc. The NFW model predicts that the cumulative projected mass contained within a radius R scales as M (

A B S T R A C TWe have obtained U-and R-band observations of the depletion of background galaxies resulting from the gravitational lensing of the galaxy cluster CL002411654 z 0X39X The radial depletion curves show a significant depletion in both bands within a radius of 40± 70 arcsec from the cluster centre. This is the first time that depletion is detected in the U band. This gives independent evidence for a break in the slope of the U-band luminosity function at faint magnitudes. The radially averaged R-band depletion curve is broader and deeper than in the U band. The differences can be attributed to the wavelength dependence of the slope of the luminosity function and to the different redshift distribution of the objects probed in the two bands. We estimate the Einstein radius, r E , of a singular isothermal sphere lens model using maximum-likelihood analysis. Adopting a slope of the number counts of a 0X2 and using the background density found beyond r 150 arcsecY we find r E 17^3 and 25^3 arcsec in the U and R bands, respectively. When combined with the redshift of the single background galaxy at z 1X675 seen as four giant arcs around 30 arcsec from the cluster centre, these values indicate a median redshift in the range kz S l < 0X7 to 1.1 for the U AB $ 24 mag and R AB $ 24 mag populations.

Abstract.We have studied the fate of initial magnetic fields in the hot halo gas out of which the visible parts of galaxies form, using threedimensional numerical MHD-experiments. The halo gas undergoes compression by several orders of magnitude in the subsonic cooling flow that forms the cold disk. The magnetic field is carried along and is amplified considerably in the process, reaching µG levels for reasonable values of the initial ratio of magnetic to thermal energy density.