Deprojection of luminosity functions of galaxies in the Coma cluster

We use a simple analytic model to deproject 2-d luminosity functions (LF) of galaxies in the Coma cluster measured by Beijersbergen et al. 2002. We demonstrate that the shapes of the LFs change after deprojection. It is therefore essential to correct LFs for projection effects. The deprojected LFs of the central area have best-fitting Schechter parameters of M^{*}_U=-18.31^{+0.08}_{-0.08} and \alpha_U=-1.27^{+0.018}_{-0.018}, M^{*}_B=-19.79^{+0.14}_{-0.15} and \alpha_B=-1.44^{+0.016}_{-0.016} and M^{*}_r=-21.77^{+0.20}_{-0.28} and \alpha_r=-1.27^{+0.012}_{-0.012}. The corrections are not significant enough to change the previously observed trend of increasing faint end slopes with increasing distance to the cluster center. The weighted U, B, and r band slopes of the deprojected LFs show a slightly weaker steepening with increasing projected cluster radius.Comment: Accepted for publication in A&A as a Research Not

Orbital angular momentum exchange in an optical parametric oscillator

We present a study of orbital angular momentum transfer from pump to down-converted beams in a type-II Optical Parametric Oscillator. Cavity and anisotropy effects are investigated and demostrated to play a central role in the transverse mode dynamics. While the idler beam can oscillate in a Laguerre-Gauss mode, the crystal birefringence induces an astigmatic effect in the signal beam that prevents the resonance of such mode.Comment: 10 pages, 8 figures, regular articl

A Morphological-type dependence in the mu_0-log(h) plane of Spiral galaxy disks

We present observational evidence for a galaxy `Type' dependence to the location of a spiral galaxy's disk parameters in the mu_0-log(h) (central disk surface-brightness - disk scale-length) plane. With a sample of ~40 Low Surface Brightness galaxies (both bulge- and disk-dominated) and ~80 High Surface Brightness galaxies, the early-type disk galaxies (<=Sc) tend to define a bright envelope in the mu_0-log(h) plane, while the late-type (>=Scd) spiral galaxies have, in general, smaller and fainter disks. Below the defining surface brightness threshold for a Low Surface Brightness galaxy (i.e. more than 1 mag fainter than the 21.65 B-mag arcsec^(-2) Freeman value), the early-type spiral galaxies have scale-lengths greater than 8-9 kpc, while the late-type spiral galaxies have smaller scale-lengths. All galaxies have been modelled with a seeing-convolved Sersic r^(1/n) bulge and exponential disk model. We show that the trend of decreasing bulge shape parameter (n) with increasing Hubble type and decreasing bulge-to-disk luminosity ratio, which has been observed amongst the High Surface Brightness galaxies, extends to the Low Surface Brightness galaxies, revealing a continuous range of structural parameters.Comment: To be published in ApJ. Inc. three two-part figure

The rotation curves of dwarf galaxies: a problem for Cold Dark Matter?

We address the issue of accuracy in recovering density profiles from observations of rotation curves of galaxies. We ``observe'' and analyze our models in much the same way as observers do the real galaxies. We find that the tilted ring model analysis produces an underestimate of the central rotational velocity. In some cases the galaxy halo density profile seems to have a flat core, while in reality it does not. We identify three effects, which explain the systematic biases: (1) inclination (2), small bulge, and (3) bar. The presence of even a small non-rotating bulge component reduces the rotation velocity. In the case of a disk with a bar, the underestimate of the circular velocity is larger due to a combination of non-circular motions and random velocities. Signatures of bars can be difficult to detect in the surface brightness profiles of the model galaxies. The variation of inclination angle and isophote position angle with radius are more reliable indicators of bar presence than the surface brightness profiles. The systematic biases in the central ~ 1 kpc of galaxies are not large. Each effect separately gives typically a few kms error, but the effects add up. In some cases the error in circular velocity was a factor of two, but typically we get about 20 percent. The result is the false inference that the density profile of the halo flattens in the central parts. Our observations of real galaxies show that for a large fraction of galaxies the velocity of gas rotation (as measured by emission lines) is very close to the rotation of stellar component (as measured by absorption lines). This implies that the systematic effects discussed in this paper are also applicable both for the stars and emission-line gas.Comment: ApJ, in press, 30 pages, Latex, 21 .eps figure

Copers and Noncopers Use Different Landing Techniques to Limit Anterior Tibial Translation After Anterior Cruciate Ligament Reconstruction

Background: At 1 year after anterior cruciate ligament reconstruction (ACLR), two-thirds of patients manage to return to sports (copers), whereas one-third of patients do not return to sports (noncopers). Copers and noncopers have different muscle activation patterns, and noncopers may not be able to control dynamic anterior tibial translation (ATTd) as well as copers. Purpose/Hypothesis: To investigate whether (1) there is a positive correlation between passive ATT (ATTp; ie, general joint laxity) and ATTd during jump landing, (2) whether ATTd is moderated by muscle activating patterns, and (3) whether there is a difference in moderating ATTd between copers and noncopers. We hypothesized that patients who have undergone ACLR compensate for ATTd by developing muscle strategies that are more effective in copers compared with noncopers. Study Design: Controlled laboratory study. Methods: A total of 40 patients who underwent unilateral ACLR performed 10 single-leg hops for distance with both legs. Lower body kinematic and kinetic data were measured using a motion-capture system, and ATTd was determined with an embedded method. Muscle activity was measured using electromyographic signals. Bilateral ATTp was measured using a KT-1000 arthrometer. In addition, the Beighton score was obtained. Results: There was no significant correlation between ATTp and ATTd in copers; however, there was a positive correlation between ATTp and ATTd in the operated knee of noncopers. There was a positive correlation between the Beighton score and ATTp as well as between the Beighton score and ATTd in both copers and noncopers in the operated knee. Copers showed a negative correlation between ATTd and gastrocnemius activity in their operated leg during landing. Noncopers showed a positive correlation between ATTd and knee flexion moment in their operated knee during landing. Conclusion: Copers used increased gastrocnemius activity to reduce ATTd, whereas noncopers moderated ATTd by generating a smaller knee flexion moment

On the relation between circular velocity and central velocity dispersion in high and low surface brightness galaxies

In order to investigate the correlation between the circular velocity Vc and the central velocity dispersion of the spheroidal component sigma_c, we analyzed these quantities for a sample of 40 high surface brightness disc galaxies (hereafter HSB), 8 giant low surface brightness spiral galaxies (hereafter LSB), and 24 elliptical galaxies characterized by flat rotation curves. We find that the Vc-sigma_c relation is descri ed by a linear law out to velocity dispersions as low as sigma_c~50km/s, while in previous works a power law was adopted for galaxies with sigma_c>80k/ms. Elliptical galaxies with Vc based on dynamical models or directly derived from the HI rotation curves follow the same relation as the HSB galaxies in the Vc-sigma_c plane. On the contrary, the LSB galaxies follow a different relation, since most of them show either higher Vc (or lower sigma_c) with respect to the HSB galaxies. This argues against the relevance of baryon collapse in the radial density profile of the dark matter haloes of LSB galaxies. (abridged)Comment: 18 pages, 4 figures, ApJ in pres

Evidence for an outer disk in the Prototype `Compact Elliptical' Galaxy M32

M32 is the prototype for the relatively rare class of galaxies referred to as `compact ellipticals'. It has been suggested that M32 may be a tidally disturbed r^(1/4) elliptical galaxy, or the remnant bulge of a disk-stripped early-type spiral galaxy. This paper reveals that the surface brightness profile, the velocity dispersion measurements, and the estimated supermassive black hole mass in M32 are inconsistent with the galaxy having, and probably ever having had, an r^(1/4) light profile. Instead, the radial surface brightness distribution of M32 resembles an almost perfect (bulge + exponential disk) profile, which is accompanied by a marked increase in the ellipticity profile and an associated change in the position angle profile where the `disk' starts to dominate. Compelling evidence that this bulge/disk interpretation is accurate comes from the best-fitting r^(1/n) bulge model which has a Sersic index n=1.5, in agreement with the recently discovered relation between a bulge's Sersic index and the mass of its supermassive black hole. An index n>4 would also be inconsistent with the stellar velocity dispersion of M32. The bulge-to-disk size ratio r_e /h equals 0.20, and the logarithm of the bulge-to-disk luminosity ratio log(B/D) equals 0.22, typical of lenticular galaxies. The effective radius of the bulge is 27" (~100 pc), while the scale-length of the disk is less well determined: due to possible tidal- stripping of the outer profile beyond 220-250", the scale-length may be as large as 1.3 kpc. M32 is a relatively face-on, nucleated, dwarf galaxy with a low surface brightness disk and a high surface brightness bulge. This finding brings into question the existence of the compact elliptical class of galaxies.Comment: Accepted for publication in ApJ Letter

The stellar disk thickness of LSB galaxies

We present surface photometry results for a sample of eleven edge-on galaxies observed with the 6m telescope at the Special Astrophysical Observatory (Russia). The photometric scale length, scale height, and central surface brightness of the stellar disks of our sample galaxies are estimated. We show that four galaxies in our sample, which are visually referred as objects of the lowest surface brightness class in the Revised Flat Galaxies Catalog, have bona fide low surface brightness (LSB) disks. We find from the comparison of photometric scales that the stellar disks of LSB galaxies are thinner than those of high surface brightness (HSB) ones. There is a clear correlation between the central surface brightness of the stellar disk and its vertical to radial scale ratio. The masses of spherical subsystems (dark halo + bulge) and the dark halo masses are obtained for the sample galaxies based on the thickness of their stellar disks. The LSB galaxies tend to harbor more massive spherical subsystems than the HSB objects, whereas no systematic difference in the dark halo masses between LSB and HSB galaxies is found. At the same time, the inferred mass-to-luminosity ratio for the LSB disks appears to be systematically higher than for HSB disks.Comment: 33 pages with 17 Postscript figures, uses aastex.cls, accepted by Ap

Toroidal optical dipole traps for atomic Bose-Einstein condensates using Laguerre-Gaussian beams

We theoretically investigate the use of red-detuned Laguerre-Gaussian (LG) laser beams of varying azimuthal mode index for producing toroidal optical dipole traps in two-dimensional atomic Bose-Einstein condensates. Higher-order LG beams provide deeper potential wells and tighter confinement for a fixed toroid radius and laser power. Numerical simulations of the loading of the toroidal trap from a variety of initial conditions is also given.Comment: 12 pages, 5 figures, submitted to Phys. Rev.

Laser cooling of trapped atoms to the ground state : a dark state in position space

We propose a scheme that allows us to laser cool trapped atoms to the ground state of a one-dimensional confining potential. The scheme is based on the creation of a dark state by designing the laser profile, so that the hottest atoms are coherently pumped to another internal level, and then repumped back. The scheme works beyond the Lamb-Dicke limit. We present results of a full quantum treatment for a one-dimensional model