Shannon Multiresolution Analysis on the Heisenberg Group

We present a notion of frame multiresolution analysis on the Heisenberg group, abbreviated by FMRA, and study its properties. Using the irreducible representations of this group, we shall define a sinc-type function which is our starting point for obtaining the scaling function. Further, we shall give a concrete example of a wavelet FMRA on the Heisenberg group which is analogous to the Shannon MRA on \RR.Comment: 17 page

Environments of Redshift Survey Compact Groups of Galaxies

Redshift Survey Compact Groups (RSCGs) are tight knots of N >= 3 galaxies selected from the CfA2+SSRS2 redshift survey. The selection is based on physical extent and association in redshift space alone. We measured 300 new redshifts of fainter galaxies within 1 h^{-1} Mpc of 14 RSCGs to explore the relationship between RSCGs and their environments. 13 of 14 RSCGs are embedded in overdense regions of redshift space. The systems range from a loose group of 5 members to an Abell cluster. The remaining group, RSCG 64, appears isolated. RSCGs are isolated and distinct from their surroundings to varying degrees, as are the Hickson Compact Groups. Among the 13 embedded RSCGs, 3 are distinct from their general environments (RSCG 9, RSCG 11 and RSCG 85).Comment: 35 pages, including 10 figures and 5 tables, accepted for publication in the Astronomical Journa

Characterizing a cluster's dynamic state using a single epoch of radial velocities

Radial velocity measurements can be used to constrain the dynamical state of a stellar cluster. However, for clusters with velocity dispersions smaller than a few km/s the observed radial velocity distribution tends to be dominated by the orbital motions of binaries rather than the stellar motions through the potential well of the cluster. Our goal is to characterize the intrinsic velocity distribution of a cluster from a single epoch of radial velocity data, even for a cluster with a velocity dispersion of a fraction of a km/s, using a maximum likelihood procedure. Assuming a period, mass ratio, and eccentricity distribution for the binaries in the observed cluster this procedure fits a dynamical model describing the velocity distribution for the single stars and center of masses of the binaries, simultaneously with the radial velocities caused by binary orbital motions, using all the information available in the observed velocity distribution. We find that the fits to the intrinsic velocity distribution depend only weakly on the binary properties assumed, so the uncertainty in the fitted parameters tends to be dominated by statistical uncertainties. Based on Monte Carlo simulations we provide an estimate of how these statistical uncertainties vary with the velocity dispersion, binary fraction, and the number of observed stars, which can be used to estimate the sample size needed to reach a specific accuracy. Finally we test the method on the well-studied open cluster NGC 188, showing that it can reproduce a velocity dispersion of only 0.5 km/s using a single epoch of the multi-epoch radial velocity data. If the binary period, mass ratio, and eccentricity distribution of the observed stars are roughly known, this procedure can be used to correct for the effect of binary orbital motions on an observed velocity distribution. [Abridged]Comment: 11 pages, 6 figures, accepted by A&

The Faint End of the Luminosity Function and Low Surface Brightness Galaxies

SHELS (Smithsonian Hectospec Lensing Survey) is a dense redshift survey covering a 4 square degree region to a limiting R = 20.6. In the construction of the galaxy catalog and in the acquisition of spectroscopic targets, we paid careful attention to the survey completeness for lower surface brightness dwarf galaxies. Thus, although the survey covers a small area, it is a robust basis for computation of the slope of the faint end of the galaxy luminosity function to a limiting M_R = -13.3 + 5logh. We calculate the faint end slope in the R-band for the subset of SHELS galaxies with redshif ts in the range 0.02 <= z < 0.1, SHELS_{0.1}. This sample contains 532 galaxies with R< 20.6 and with a median surface brightness within the half light radius of SB_{50,R} = 21.82 mag arcsec^{-2}. We used this sample to make one of the few direct measurements of the dependence of the faint end of the galaxy luminosity function on surface brightness. For the sample as a whole the faint end slope, alpha = -1.31 +/- 0.04, is consistent with both the Blanton et al. (2005b) analysis of the SDSS and the Liu et al. (2008) analysis of the COSMOS field. This consistency is impressive given the very different approaches of th ese three surveys. A magnitude limited sample of 135 galaxies with optical spectroscopic reds hifts with mean half-light surface brightness, SB_{50,R} >= 22.5 mag arcsec^{-2} is unique to SHELS_{0.1}. The faint end slope is alpha_{22.5} = -1.52+/- 0.16. SHELS_{0.1} shows that lower surface brightness objects dominate the faint end slope of the l uminosity function in the field, underscoring the importance of surface brightness limits in evaluating measurements of the faint end slope and its evolution.Comment: 34 pages, 13 figures, 3 tables, Astronomical Journal, in press (updated based on review

Phase-Coherent Transport through a Mesoscopic System: A New Probe of Non-Fermi-Liquid Behavior

A novel chiral interferometer is proposed that allows for a direct measurement of the phase of the transmission coefficient for transport through a variety of mesoscopic structures in a strong magnetic field. The effects of electron-electron interaction on this phase is investigated with the use of finite-size bosonization techniques combined with perturbation theory resummation. New non-Fermi-liquid phenomena are predicted in the FQHE regime that may be used to distinguish experimentally between Luttinger and Fermi liquids.Comment: 4 pages, 3 figures, Revte

Formation of new stellar populations from gas accreted by massive young star clusters

Stars in star clusters are thought to form in a single burst from a common progenitor cloud of molecular gas. However, massive, old globular clusters -- with ages greater than 10 billion years and masses of several hundred thousand solar masses -- often harbour multiple stellar populations, indicating that more than one star-forming event occurred during their lifetimes. Colliding stellar winds from late-stage, asymptotic-giant-branch stars are often invoked as second-generation star-formation trigger. The initial cluster masses should be at least 10 times more massive than they are today for this to work. However, large populations of clusters with masses greater than a few million solar masses are not found in the local Universe. Here we report on three 1-2 billion-year-old, massive star clusters in the Magellanic Clouds, which show clear evidence of burst-like star formation that occurred a few hundred million years after their initial formation era. We show that such clusters could accrete sufficient gas reservoirs to form new stars if the clusters orbited in their host galaxies' gaseous discs throughout the period between their initial formation and the more recent bursts of star formation. This may eventually give rise to the ubiquitous multiple stellar populations in globular clusters.Comment: 10 pages, 11 figures, Authors' version of a letter published in Nature (27 January 2016), including Methods and Extended Dat

Triggered Star Formation in Galaxy Pairs at z=0.08-0.38

We measure the strength, frequency, and timescale of tidally triggered star formation at redshift z=0.08-0.38 in a spectroscopically complete sample of galaxy pairs drawn from the magnitude-limited redshift survey of 9,825 Smithsonian Hectospec Lensing Survey (SHELS) galaxies with R<20.3. To examine the evidence for tidal triggering, we identify a volume-limited sample of major (|\Delta M_R|1/5) pair galaxies with $M_R < -20.8 in the redshift range z=0.08-0.31. The size and completeness of the spectroscopic survey allows us to focus on regions of low local density. The spectrophotometric calibration enables the use of the 4000 Ang break (D_n4000), the H\alpha specific star formation rate (SSFR_{H\alpha}), and population models to characterize the galaxies. We show that D_n4000 is a useful population classification tool; it closely tracks the identification of emission line galaxies. The sample of major pair galaxies in regions of low local density with low D_n4000 demonstrates the expected anti-correlation between pair-wise projected separation and a set of star formation indicators explored in previous studies. We measure the frequency of triggered star formation by comparing the SSFR_{H\alpha} in the volume-limited sample in regions of low local density: 32 +/-7% of the major pair galaxies have SSFR_{H\alpha} at least double the median rate of the unpaired field galaxies. Comparison of stellar population models for pair and for unpaired field galaxies implies a timescale for triggered star formation of ~300-400 Myr.Comment: 25 pages, 15 figures. Accepted to A

Asbestos-related pleural disease

The image shows asbestos plaques on the right parietal pleura of a 58-year-old former shipyard worker who died of acute suppurative bronchitis. He also had cor pulmonale and congestive heart failure. Histologically, pulmonary interstitial fibrosis with asbestos bodies was demonstrated. The pleural plaques consist predominantly of dense collagen. This photograph was taken after removal of the lung with the camera held in the lower right thorax, at approximately the level of the diaphragm, looking up toward the apex of the chest cavity

Focal nodular hyperplasia of the liver

A benign, non-neoplastic, reactive growth of the liver, focal nodular hyperplasia (FNH) of the liver was first clearly described by Edmondson in the 1950’s, although there are various prior reports that likely represent the same lesion. A variety of synonyms have been applied including focal cirrhosis, pedunculated adenoma, solitary hyperplastic nodule, mixed adenoma, hamartoma and hamartomatous cholangeiohepatoma