An HST Archival Survey of Feathers in Spiral Galaxies

We present a survey of spiral arm extinction substructure referred to as feathers in 223 spiral galaxies using HST WFPC2 images. The sample includes all galaxies in the RC3 catalog with cz < 5000 km/s, B_T < 15, i < 60 degrees, and types Sa--Sd with well-exposed broadband WFPC2 images. The detection frequency of delineated, periodic feathers in this sample is 20% (45 of 223). This work is consistent with Lynds (1970), who concluded that feathers are common in prototypical Sc galaxies; we find that feathers are equally common in Sb galaxies. Sb--Sc galaxies without clear evidence for feathers either had poorer quality images, or flocculent or complex structure. We did not find clearly defined feathers in any Scd--Sd galaxy. The probability of detecting feathers was highest (83%) for spirals with well-defined primary dust lanes (PDLs; the lanes which line the inner edge of an arm); well-defined PDLs were only noted in Sab--Sc galaxies. Consistent with earlier work, we find that neighboring feathers tend to have similar shapes and pitch angles. OB associations are often found lining feathers, and many feathers transition to the stellar substructures known as spurs (Elmegreen 1980). We find that feathers are coincident with interarm filaments strikingly revealed in Spitzer 8 micron images. Comparison with CO 1-0 maps of NGC 0628 and NGC 5194 from BIMA SONG shows that feathers originate at the PDL coincident with gas surface density peaks. Contrary to the appearance at 8 microns, the CO maps show that gas surface density in feathers decreases rapidly with distance from the PDL. Also, we find that the spacing between feathers decreases with increasing gas surface density, consistent with formation via a gravitational instability.Comment: 47 pages, 22 figures (Figures 1-16,18 are in JPEG format, figures 17,19-22 are embedded postscript files; full resolution images at http://www.astro.umd.edu/~mlavigne/research/hst-survey-06-2006/). Accepted for publication in the Ap

Dynamically Driven Evolution of the Interstellar Medium in M51

We report the highest-fidelity observations of the spiral galaxy M51 in CO emission, revealing the evolution of giant molecular clouds (GMCs) vis-a-vis the large-scale galactic structure and dynamics. The most massive GMCs (so-called GMAs) are first assembled and then broken up as the gas flow through the spiral arms. The GMAs and their H2 molecules are not fully dissociated into atomic gas as predicted in stellar feedback scenarios, but are fragmented into smaller GMCs upon leaving the spiral arms. The remnants of GMAs are detected as the chains of GMCs that emerge from the spiral arms into interarm regions. The kinematic shear within the spiral arms is sufficient to unbind the GMAs against self-gravity. We conclude that the evolution of GMCs is driven by large-scale galactic dynamics --their coagulation into GMAs is due to spiral arm streaming motions upon entering the arms, followed by fragmentation due to shear as they leave the arms on the downstream side. In M51, the majority of the gas remains molecular from arm entry through the inter-arm region and into the next spiral arm passage.Comment: 6 pages, including 3 figures. Accepted, ApJ

Dynamically Driven Evolution of the Interstellar Medium in M51

Massive star formation occurs in giant molecular clouds (GMCs); an understanding of the evolution of GMCs is a prerequisite to develop theories of star formation and galaxy evolution. We report the highest-fidelity observations of the grand-design spiral galaxy M51 in carbon monoxide (CO) emission, revealing the evolution of GMCs vis-a-vis the large-scale galactic structure and dynamics. The most massive GMCs (giant molecular associations (GMAs)) are first assembled and then broken up as the gas flow through the spiral arms. The GMAs and their H_2 molecules are not fully dissociated into atomic gas as predicted in stellar feedback scenarios, but are fragmented into smaller GMCs upon leaving the spiral arms. The remnants of GMAs are detected as the chains of GMCs that emerge from the spiral arms into interarm regions. The kinematic shear within the spiral arms is sufficient to unbind the GMAs against self-gravity. We conclude that the evolution of GMCs is driven by large-scale galactic dynamics—their coagulation into GMAs is due to spiral arm streaming motions upon entering the arms, followed by fragmentation due to shear as they leave the arms on the downstream side. In M51, the majority of the gas remains molecular from arm entry through the interarm region and into the next spiral arm passage

Polygonal Structures in the Gaseous Disk: Numerical Simulations

The results of numerical simulations of a gaseous disk in the potential of a stellar spiral density wave are presented. The conditions under which straightened spiral arm segments (rows) form in the gas component are studied. These features of the spiral structure were identified in a series of works by A.D. Chernin with coauthors. Gas-dynamic simulations have been performed for a wide range of model parameters: the pitch angle of the spiral pattern, the amplitude of the stellar spiral density wave, the disk rotation speed, and the temperature of the gas component. The results of 2D- and 3D-disk simulations are compared. The rows in the numerical simulations are shown to be an essentially nonstationary phenomenon. A statistical analysis of the distribution of geometric parameters for spiral patterns with rows in the observed galaxies and the constructed hydrodynamic models shows good agreement. In particular, the numerical simulations and observations of galaxies give $\simeq 120^\circ$ for the average angles between straight segments.Comment: 22 pages, 10 figure

In and around: identifying predictors of theft within and near to major mass underground transit systems

This article identifies factors that encourage or reduce pick-pocketing at underground rail stations through a case study analysis of the London Underground. Negative binomial Poisson regression models found predictor variables of pick-pocketing selected from the internal characteristics of stations and features of their nearby surroundings. Factors that increased risk were those associated with greater congestion inside stations including lifts, waiting rooms and fewer platforms; and increased levels of accessibility near stations, more paths and roads. Features that reduced risk were those likely to encourage detection and guardianship; stations with more personal validators, staffing levels and shop rentals; and the presence of more domestic buildings nearby. Station type was also influential; those that were ‘attractors’ of crime and those frequently used by tourists were at greater risk. The findings suggest a transmission of theft risk between the internal settings of underground stations and their nearby surroundings

Mental health (GHQ12; CES-D) and attitudes towards the value of work among inmates of a semi-open prison and the long-term unemployed in Luxembourg

Aim: To analyse the relationships between mental health and employment commitment among prisoners and the long-term unemployed (LTU) trying to return to work. Method: Fifty-two of 62 male inmates of a semi-open prison (Givenich Penitentiary Centre, the only such unit in Luxembourg), and 69 LTU registered at the Luxembourg Employment Administration completed a questionnaire exploring: 1) mental health (measured by means of scales GHQ12 and CES-D); 2) employment commitment; 3) availability of a support network, selfesteem, empowerment; and 4) socio-demographic characteristics. Results: Compared with LTU, inmates were younger, more had work experience (54.9% vs 26.1%), and more were educated to only a low level (71.1% vs 58.0%). The link between employment commitment and mental health in the LTU was the opposite of that seen among the prisoners: the more significant the perceived importance of employment, the worse the mental health (GHQ12 p = 0.003; CES-D p < 0.001) of the LTU; in contrast, among prisoners, the GHQ12 showed that the greater the perceived value of work, the lower the psychic distress (p = 0.012). Greater empowerment was associated with less depression in both populations. The education levels of people who did not reach the end of secondary school, whether inmates or LTU, were negatively linked with their mental equilibrium. Conclusion: The two groups clearly need professional support. Future research should further investigate the link between different forms of professional help and mental health. Randomized controlled trials could be carried out in both groups, with interventions to improve work commitment for prisoners and to help with getting a job for LTU. For those LTU who value employment but cannot find it, the best help may be psychological support

Relationship Between Biogenic Amines and Free Amino Acid Contents of Winesand Musts from Alentejo (Portugal)

The concentration of biogenic amines and free amino acids was studied in 102 Portuguese wines and 18 musts from Alentejo demarcated (D.O.C.) regions. Most wines were commercial, except for 38 monovarietals obtained by micro vinification. Musts from the varieties used to produce the latter wines were also studied. Both biogenic amines and free amino acids were analyzed by HPLC using fluorescence detection for their o-phthalaldehyde/fluorenylmethyl chloroformate (OPA/FMOC) derivatives. The most significant amines (average 10.8 mg/L for histamine+tyramine in red, and 7.4 mg/L for white wines) were found to be present at low levels and, although no important relationship between each individual biogenic amine could be obtained, the total amine content depends significantly on the assimilable amino acid content in wine

Measurement of χ c1 and χ c2 production with s√ = 7 TeV pp collisions at ATLAS

The prompt and non-prompt production cross-sections for the χ c1 and χ c2 charmonium states are measured in pp collisions at s√ = 7 TeV with the ATLAS detector at the LHC using 4.5 fb−1 of integrated luminosity. The χ c states are reconstructed through the radiative decay χ c → J/ψγ (with J/ψ → μ + μ −) where photons are reconstructed from γ → e + e − conversions. The production rate of the χ c2 state relative to the χ c1 state is measured for prompt and non-prompt χ c as a function of J/ψ transverse momentum. The prompt χ c cross-sections are combined with existing measurements of prompt J/ψ production to derive the fraction of prompt J/ψ produced in feed-down from χ c decays. The fractions of χ c1 and χ c2 produced in b-hadron decays are also measured

Search for squarks and gluinos in events with isolated leptons, jets and missing transverse momentum at s√=8 TeV with the ATLAS detector

The results of a search for supersymmetry in final states containing at least one isolated lepton (electron or muon), jets and large missing transverse momentum with the ATLAS detector at the Large Hadron Collider are reported. The search is based on proton-proton collision data at a centre-of-mass energy s√=8 TeV collected in 2012, corresponding to an integrated luminosity of 20 fb−1. No significant excess above the Standard Model expectation is observed. Limits are set on supersymmetric particle masses for various supersymmetric models. Depending on the model, the search excludes gluino masses up to 1.32 TeV and squark masses up to 840 GeV. Limits are also set on the parameters of a minimal universal extra dimension model, excluding a compactification radius of 1/R c = 950 GeV for a cut-off scale times radius (ΛR c) of approximately 30

Evidence for the Higgs-boson Yukawa coupling to tau leptons with the ATLAS detector

Results of a search for H → τ τ decays are presented, based on the full set of proton-proton collision data recorded by the ATLAS experiment at the LHC during 2011 and 2012. The data correspond to integrated luminosities of 4.5 fb−1 and 20.3 fb−1 at centre-of-mass energies of √s = 7 TeV and √s = 8 TeV respectively. All combinations of leptonic (τ → `νν¯ with ` = e, µ) and hadronic (τ → hadrons ν) tau decays are considered. An excess of events over the expected background from other Standard Model processes is found with an observed (expected) significance of 4.5 (3.4) standard deviations. This excess provides evidence for the direct coupling of the recently discovered Higgs boson to fermions. The measured signal strength, normalised to the Standard Model expectation, of µ = 1.43 +0.43 −0.37 is consistent with the predicted Yukawa coupling strength in the Standard Model