bluuebunny/crossref_metadata_2025 huggingface dataset:
Galaxy formation and evolution with the Dark Energy Survey
Authors: Capozzi Diego , Thomas Daniel , Maraston Claudia , Davies Luke J. M.
Published: July 2013

The Dark Energy Survey (DES) will be the new state-of the-art in large-scale galaxy imaging surveys. With 5,000 deg2, it will cover an area of the sky similar to SDSS-II, but will go over two magnitudes deeper, reaching 24th magnitude in all four optical bands (griz). DES will further provide observations in the redder Y-band and will be complemented with VISTA observations in the near-infrared bands JHK. Hence DES will furnish an unprecedented combination of sky and wavelength coverage and depth, unreached by any of the existing galaxy surveys. The very nature of the DES data set – large volume at intermediate photometric depth – allows us to probe galaxy formation and evolution within a cosmic-time range of ~ 10 Gyr and in different environments. In fact there will be many galaxy clusters available for galaxy evolution studies, given that one of the main aims of DES is to use their abundance to constrain the equation of state of dark energy. The X-ray follow up of these clusters, coupled with the use of gravitational lensing, will provide very precise measures of their masses, enabling us to study in detail the influence of the environment on galaxy formation and evolution processes. DES will leverage the study of these processes by allowing us to perform a detailed investigation of the galaxy luminosity and stellar mass functions and of the relationship between dark and baryonic matter as described by the Halo Occupation Distribution.
The GAMA Panchromatic Survey
Authors: Driver Simon P.
Published: July 2013

The Galaxy And Mass Assembly Survey (GAMA) has now been operating for almost 5 years gathering spectroscopic redshifts for five regions of sky spanning 300 sq degrees in total to a depth of r < 19.8 mag. The survey has amassed over 225,000 redshifts making it the third largest redshift campaign after the SDSS and BOSS surveys. The survey has two novel features that set it apart: (1) complete and uniform sampling to a fixed flux limit (r < 19.8 mag) regardless of galaxy clustering due to multiple-visits to each sky region, enabling the construction of high-fidelity catalogues of groups and pairs, (2) co-ordination with diverse imaging campaigns which together sample an extremely broad range along the electro-magnetic spectrum from the UV (GALEX) through optical (VST KIDs), near-IR (VISTA VIKING), mid-IR (WISE), far-IR (Herschel-Atlas), 1m (GMRT), and eventually 20cm continuum and rest-frame 21cm line measurements (ASKAP DINGO). Apart from the ASKAP campaign all multi-wavelength programmes are either complete or in the final stages of observations and the UV-far-IR data are expected to be fully merged by the end of 2013. This article provides a brief flavour of the coming panchromatic database which will eventually include measurements or upper-limits across 27 wavebands for 380,000 galaxies. GAMA DR2 is scheduled for the end of January 2013.
GAMA: The effect of environment on galaxy emission line properties
Authors: Steele Oliver , Thomas Daniel , Maraston Claudia , Etherington James ,   the GAMA collaboration
Published: July 2013

We study the influence of environment on emission line properties using the Galaxy And Mass Assembly (GAMA) survey, taking care to disentangle the role of mass and environment. We look at the role of local density separating galaxies into classifications star forming, AGN, and SF/AGN composite using the BPT diagnostic diagram. We find that environment is generally less important as a driving factor than galaxy mass. The presence of emission lines, whether driven by star formation or central supermassive black hole activity mostly depends on galaxy mass consistently for all galaxy types.
Merger rates for early-type galaxies: combining clustering and luminosity function measurements
Authors: Padilla Nelson D. , Gawiser Eric , Christlein Daniel , Marchesini Danilo
Published: July 2013

We present a study of the evolution of early-type galaxies (ETGs) that combines luminosity function and clustering measurements. This technique shows that ETGs at a given redshift evolve into brighter galaxies in the rest-frame passively evolved optical at lower redshifts. Notice that this indicates that a stellar-mass selection at different redshifts does not necessarily provide samples of galaxies in a progenitor-descendant relationship. The comparison between high redshift ETGs and their likely descendants at z = 0 points to a higher number density for the progenitors by a factor 3 to 11, implying the need for mergers to decrease their number density by today. Because the progenitor-to-descendant ratios of luminosity density are consistent with the unit value, our results show no need for strong star-formation episodes in ETGs since z = 1, which indicates that the needed mergers are dry, i.e. gas free.
Is there evolution in the black hole - bulge relation?
Authors: Schulze Andreas , Wisotzki Lutz
Published: July 2013

We present a framework to investigate sample selection effects on the observed BH - bulge relation and its evolution with redshift. We particularly discuss an active fraction bias and a luminosity bias. Applying our framework to literature studies, we cannot find statistically significant evidence for an evolving BH-bulge relation.
Dark matter in massive galaxies
Authors: Gerhard Ortwin
Published: July 2013

The spatial distributions of luminous and dark matter in massive early-type galaxies (ETGs) reflect the formation processes which shaped these systems. This article reviews the predictions of cosmological simulations for the dark and baryonic components of ETGs, and the observational constraints from lensing, hydrostatic X-ray gas atmospheres, and outer halo stellar dynamics.
Massive bulges are not just ellipticals surrounded by disks
Authors: Gadotti Dimitri A.
Published: July 2013

Using results from parametric multi-component multi-band image fitting of 1000 local massive galaxies in the SDSS, I investigate scaling relations of elliptical galaxies and bulges of disk galaxies. I show that ellipticals and bulges occupy different loci in both the edge-on and face-on views of the fundamental plane. In addition, ellipticals and bulges have offset mass-size relations (see Fig. 1). These results imply that massive bulges are not just massive ellipticals with a surrounding disk, a misconception driven by early studies. This is evidence that massive ellipticals and bulges have different formation histories, with important consequences for studies on galaxy formation and evolution. Full details can be seen in Gadotti (2009).
2D kinematics of the edge-on spiral galaxy ESO 379-006
Authors: Rosado M. , Gabbasov R. F. , Repetto P. , Fuentes-Carrera I. , Amram P. , Martos M. , Hernandez O.
Published: July 2013

We present a kinematical study of the marginally edge-on galaxy ESO 379-006. With Fabry-Perot spectroscopy at Hα we obtain velocity maps, the radial velocity field, and position-velocity diagrams parallel to the major and to the minor axis of the galaxy. We build the rotation curve of the galaxy and discuss the role of projection effects. The twisting of isovelocities in the radial velocity field of the disk of ESO 379-006 as well as a kinematical asymmetry found in the position-velocity diagrams parallel to the minor axis suggest the existence of non-circular motions that can be modeled by including a radial inflow besides the rotation motion. Extraplanar Diffuse Ionized gas was detected in this galaxy both from the images and from its kinematics. It is possible that the diffuse gas is lagging in rotation.
On the general structure of giant low surface brightness galaxy Malin 2
Authors: Saburova A. S. , Kasparova A. V. , Katkov I. Yu. , Bizyaev D. V. , Chilingarian I. V.
Published: July 2013

We carried out the multicolor surface photometry in BVR and griz filters parallel with stellar kinematic measurements from the long slit spectra for the low surface brightness galaxy Malin 2. The use of the multicolor surface photometry as well as the available HI rotation curve allowed us to construct the mass distribution model of the galaxy. Photometrical and dynamical mass estimates agree with the dark halo mass fraction of about 70% within four disc radial scalelengths (~ 70 kpc). We used our dynamical model to obtain radial profiles of the equilibrium disc volume density and gas pressure in the galaxy midplane based on the available HI and CO data. The observed molecular gas fraction appears to be much higher than in the high surface brightness galaxies for a similar gas pressure.
The intriguing properties of local compact massive galaxies: What are they?
Authors: Ferré-Mateu A. , Vazdekis A. , Trujillo I. , Sánchez-Blázquez P. , Ricciardelli E. , de la Rosa I. G.
Published: July 2013

Studying the properties of the few compact massive galaxies that exist in the local Universe (Trujillo et al. 2009) might provide a closer look to the nature of their high redshift (z ≥ 1.0) massive counterparts. By this means we have characterized their main kinematics, structural properties, stellar populations and star formation histories with a set of new high quality spectroscopic and imaging data (Ferré-Mateu et al. 2012 and Trujillo et al. 2012). These galaxies seem to be truly unique, as they do not follow the characteristic kinematics, stellar surface mass density profiles and stellar population patterns of present-day massive ellipticals or spirals of similar mass. They are, instead, more alike their high-z analogs.

Summarizing, local compact massive galaxies are rare, unique and the perfect laboratory to study their high redshift counterparts.
Super-massive black hole binaries in gas-rich environments
Authors: Cuadra Jorge
Published: July 2013

Black hole binaries form after major galaxy mergers, but their fate is unclear as hardening due to stars gets inefficient at sub-parsec distances. We model an alternative scenario in which the merger is driven by the interaction of the binary with the surrounding gas.†
Stellar Population Models
Authors: Maraston Claudia
Published: July 2013

Modelling stellar populations in galaxies is a key approach to gain knowledge on the still elusive process of galaxy formation as a function of cosmic time. In this review, after a summary of the state-of-art, I discuss three aspects of the modelling, that are particularly relevant to massive galaxies, the focus of this symposium, at low and high-redshift. These are the treatment of the Thermally-Pulsating Asymptotic Giant Branch phase, evidences of an unusual Initial Mass Function, and the effect of modern stellar libraries on the model spectral energy distribution.
Stellar population gradients in GASS
Authors: Johansson Jonas , Kauffmann Guinevere , Moran Sean
Published: July 2013

We study relationships between the stellar populations and interstellar medium in massive galaxies using the Galex Arecibo SDSS Survey (GASS). The sample consists of HI-observations (~1000 galaxies) and complementary H2-observations (330 galaxies) and long-slit spectroscopy (230 galaxies). Luminosity-weighted stellar population ages, metallicitites and element abundance ratios, are derived by fitting stellar population models of absorption line indices. We find that the ages correlate more strongly with molecular gas fraction (MH2/M*) than with neutral Hydrogen fraction (MHI/M*). This result strengthens the theory that H2 is a better tracer of star-formation than HI. The sample is dominated by negative metallicity-gradients and flat Mg/Fe-gradients. Galaxies with high MH2/M*-ratios show in general flat or weakly negative age-gradients. For low MH2/M*-ratios the age-gradients are overall negative. These results are in agreement with the inside-out galaxy formation scenario. For galaxies with high r90/r50-ratios, a sub-population show positive age-gradients indicating additional formation channels. Furthermore, for galaxies with high MH2/M*-ratios more massive systems have older stellar populations in their centers, suggesting downsizing within the inside-out formation scenario.
Probing the Build-Up of Stellar Mass in the Center of IR Luminous Major Mergers with HST
Authors: Haan Sebastian , Surace Jason , Armus Lee , Evans Aaron
Published: July 2013

Interactions and mergers are important drivers of galaxy evolution, transform spiral galaxies into massive ellipticals, and fuel both powerful starbursts and massive nuclear black holes. In particular one galaxy population, namely Luminous Infrared Galaxies (LIRGs), are believed to be responsible for most of the star formation that happened in the history of the universe (see e.g. Le Floch et al. 2005, Caputi et al. 2007, Magnelli et al. 2009), and hence represent a critical phase in the evolution of galaxies where most of the galaxies mass is building up. During a merger process, violent relaxation acts on stars present in gas-rich progenitor disks, while the centers are structured by the relics of dissipational, compact starbursts, imprinting a central “extra light” component or “cusp” into the surface brightness profiles of merger remnants. Our HST NICMOS/WFC3 imaging program of the 88 most luminous LIRGs in the Great Observatories Allsky LIRG Survey (GOALS, see Armus et al. 2009) shows that the central luminosity surface density in nearby LIRGs increases significantly along the merger sequence, indicating that the gas inflow fuels a central starburst and subsequently builds a compact stellar cusp (Haan et al. 2011). A large fraction of all galaxies in our sample possess double or multiple nuclei (~63%). Half of these double nuclei are not visible in the HST B-band images due to dust obscuration, which implies strong limitations on the ability to detect the true nuclear structures of luminous infrared galaxies at high-redshift (z >2) and may explain some of the apparent discrepancy of the LIRG population and merger ratio between local and high-redshift galaxies. We find that ULIRGs (log[LIR/L⊙] > 12.0) have significantly smaller nuclear separations than LIRGs (log[LIR/L⊙] = 11.4 — 12.0) with a median value of 1.2 kpc and 6.7 kpc, respectively. In our sample, merger (regardless of whether LIRG or ULIRG) seem to be prevalent at two time scales (based on the projected nuclear separation and mass ratio of the nuclei): First, at a remaining merger time scale of 0.3<[t-tmerg]<1.3 Gyr (53% of mergers in our sample), and second, at [t-tmerg]~ 0 (26%), likely representing the first passage of interacting galaxies and the final nuclear coalescence, respectively, with a post-merger time (starburst phase after the nuclei merged) of roughly 300 Myrs.
The intriguing life of cD galaxies
Authors: Kemp S. N. , Ramírez-Siordia Víctor Hugo , Pérez-Hernández Ernesto
Published: July 2013

cD galaxies are supergiant elliptical galaxies found generally in the central parts of rich clusters, which have an extended halo-like component (envelope) in addition to the underlying de Vaucouleurs-Sérsic elliptical galaxy-like component. This envelope can extend to radial distances of > 500 kpc (Oemler 1976, Schombert 1988). There have been many theories to explain the formation of these envelopes. These include tidal stripping, where material is stripped from neighbouring galaxies; mergers and fusions, where the envelope is built up hierarchically by successive mergers with large and small galaxies; primordial origin, where the envelope is formed at the same time as the rest of the elliptical galaxy (which appears to be related to theories of early formation of the largest galaxies); and cooling flows: in clusters with X-ray emission there is often a minimum temperature in the centre interpreted as a flow of cooling gas towards the centre of the cluster, where the gas can cool sufficiently, forming stars. The colours of the stars in the envelopes will be affected by their process of formation and subsequent evolution.
Stellar discs in massive galaxies
Authors: Krajnović D. , Alatalo K. , Blitz L. , Bois M. , Bournaud F. , Bureau M. , Cappellari M. , Davies R. L. , Davis T. A. , de Zeeuw P. T. , Emsellem E. , Khochfar S. , Kuntschner H. , McDermid R. M. , Morganti R. , Naab T. , Sarzi M. , Scott N. , Serra P. , Weijmans A. , Young L. M.
Published: July 2013

Excluding those unsettled systems undergoing mergers, bright galaxies come in two flavours: with and without discs. In this work we look for photometric evidence for presence of discs and compare it with kinematic results of the ATLAS3D survey (Cappellari et al. 2011). We fit a Sérsic (1968) function to azimuthally averaged light profiles of ATLAS3D galaxies to derive single component fits and, subsequently, we fit a combination of the Sérsic function (free index n) and an exponential function (n=1) with the purpose of decomposing the light profiles into “bulge” and “disc” components (B+D model) of all non-barred sample galaxies. We compare the residuals of the B+D models with those of the single Sérsic fits and select the B+D model as preferred only when the improvement is substantial and there are no correlations within residuals. We find that the high angular momentum objects (fast rotators) are disc dominated systems with bulges of typically low n (when their light profiles can be decomposed) or are best represented with a single Sérsic function with a low Sérsic index (n<3). Single component systems with large Sérsic indices are characteristic of low angular momentum objects (slow rotators).
On the Recovery of Galaxy Properties from Spectral Fits
Authors: Magris G. , Mateu C. , A. G. Bruzual , Cabrera I.
Published: July 2013

We show the results of a non-parametric, fully bayesian implementation of a spectral fitting algorithm, designed to calculate the main physical parameters that govern the galaxy assembly process. In this work, we present results from a statistical treatment of SED fitting that allows for easy recovery and visualization of the galaxy physical parameters.
Undressing M87 by Exposing its Most Private Globulars
Authors: Montes Mireia , Acosta-Pulido José A. , Prieto M. Almudena , Fernández-Ontiveros Juan A.
Published: July 2013

We present a multiwavelength photometric analysis of the innermost (3×3 kpc2) Globular Clusters (GCs) of M87. Their Spectral Energy Distributions (SEDs) were built with J and Ks imaging obtained with NaCo at the VLT, along with HST UV-optical archival data. Using both Galatic GC templates and stellar population models, we derived ages (> 10 Gyr) and metallicities ([Fe/H]~ −0.7) for these clusters (e.g: Cohen et al. 1998). These GCs have lower metallicities than its host galaxy. This agrees with the idea that the GC population formed earlier than the bulk of the stars.
Did brightest cluster galaxies experience more than one star formation epoch?
Authors: Viljoen D. N. , Loubser S. I.
Published: July 2013

We use the full spectrum fitting ability of ULySS, with the Pegase.HR stellar population model to fit the observed spectra of 40 brightest cluster galaxies in order to determine whether a single or a composite stellar population provided the most probable representation of the star formation history (SFH). We find that some galaxies in the sample have more complex SFHs.
The stellar initial mass function in the early universe revealed from old stellar populations in our neighbourhood
Authors: Komiya Yutaka , Yamada Shimako , Suda Takuma , Fujimoto Masayuki Y.
Published: July 2013

We present a new method to investigate the IMF in the early universe from observations of extremely metal-poor (EMP) stars. EMP stars are the low-mass survivors of stars which are formed in the early universe. We can give constraints on the IMF from statistics of the elemental abundances of the EMP stars in the Galactic halo.
Revealing the origin of the cold ISM in massive early-type galaxies
Authors: Davis T. A. , Alatalo K. , Bureau M. , Young L. , Blitz L. , Crocker A. , Bayet E. , Bois M. , Bournaud F. , Cappellari M. , Davies R. L. , Duc P-A. , de Zeeuw P. T. , Emsellem E. , Falcon-Barroso J. , Khochfar S. , Krajnovic D. , Kuntschner H. , Lablanche P.-Y. , McDermid R. M. , Morganti R. , Naab T. , Sarzi M. , Scott N. , Serra P. , Weijmans A.
Published: July 2013

Recently, massive early-type galaxies have shed their red-and-dead moniker, thanks to the discovery that many host residual star formation. As part of the ATLAS-3D project, we have conducted a complete, volume-limited survey of the molecular gas in 260 local early-type galaxies with the IRAM-30m telescope and the CARMA interferometer, in an attempt to understand the fuel powering this star formation. We find that around 22% of early-type galaxies in the local volume host molecular gas reservoirs. This detection rate is independent of galaxy luminosity and environment. Here we focus on how kinematic misalignment measurements and gas-to-dust ratios can be used to put constraints on the origin of the cold ISM in these systems. The origin of the cold ISM seems to depend strongly on environment, with misaligned, dust poor gas (indicative of externally acquired material) being common in the field but completely absent in rich groups and in the Virgo cluster. Very massive galaxies also appear to be devoid of accreted gas. This suggests that in the field mergers and/or cold gas accretion dominate the gas supply, while in clusters internal secular processes become more important. This implies that environment has a strong impact on the cold gas properties of ETGs.
Dust Emission in Early-Type Galaxies with the Herschel Virgo Cluster Survey
Authors: di Serego Alighieri Sperello ,   members of the HeViCS team
Published: July 2013

We have searched for dust in an optical sample of 910 Early-Type Galaxies (ETGs) in the Virgo cluster (447 of which are optically complete at mpg ≤ 18.0), extending also to the dwarf ETGs, using Herschel images at 100, 160, 250, 350 and 500 μm. Dust was found in 52 ETGs (46 are in the optically complete sample), including M87 and another 3 ETGs with strong synchrotron emisssion. Dust is detected in 17% of ellipticals, 41% of lenticulars, and in about 4% of dwarf ETGs. The dust-to-stars mass ratio increases with decreasing optical luminosity, and for some dwarf ETGs reaches values similar to those of the dusty late-type galaxies. Slowly rotating ETGs are more likely to contain dust than fast rotating ones. Only 8 ETGs have both dust and HI, while 39 have only dust and 8 have only HI, surprisingly showing that only rarely dust and HI survive together. ETGs with dust appear to be concentrated in the densest regions of the cluster, while those with HI tend to be at the periphery. ETGs with an X-ray active SMBH are more likely to have dust and vice versa the dusty ETGs are more likely to have an active SMBH.
The role of cold gas on the stellar mass - metallicity relation of nearby galaxies
Authors: Hughes Thomas M.
Published: July 2013

We investigate the relationship between stellar mass, metallicity and gas content for a magnitude- and volume-limited sample of 260 nearby late-type galaxies in different environments. Combining new oxygen abundance measurements with ultraviolet to near-infrared photometry and Hi 21 cm line observations, we observe the relationship between stellar mass and metallicity. We also find that, at fixed stellar mass, galaxies with lower gas fractions typically possess higher oxygen abundances. Gas-poor galaxies are typically more metal-rich. Our results indicate that internal evolutionary processes, rather than environmental effects, play a key role in shaping the stellar mass-metallicity relation.
Red Galaxies from Hot Halos in Cosmological Hydro Simulations
Authors: Gabor Jared
Published: July 2013

I highlight three results from cosmological hydrodynamic simulations that yield a realistic red sequence of galaxies: 1) Major galaxy mergers are not responsible for shutting off star-formation and forming the red sequence. Starvation in hot halos is. 2) Massive galaxies grow substantially (~ × 2 in mass) after being quenched, primarily via minor (1:5) mergers. 3) Hot halo quenching naturally explains why galaxies are red when they either (a) are massive or (b) live in dense environments.
The role of Active Galactic Nuclei feedback in the formation of the brightest cluster galaxies
Authors: Martizzi Davide , Teyssier Romain , Moore Ben
Published: July 2013

The formation of the brightest cluster galaxies (BCG) is a challenge for galaxy formation theory. We performed high resolution cosmological hydrodynamical simulations with the AMR code RAMSES to study the properties of the BCG which forms at the center of a Virgo–like cluster. We compare the results of 2 galaxy formation scenarios, one in which only supernovae feedback is included, and one in which also AGN feedback is considered. Properties of the simulated BCG which are comparable with those of observed massive elliptical galaxies and BCGs cannot be obtained if AGN feedback is not considered. The stellar-to-halo mass ratio in simulations without AGN feedback appears too large when compared to observations, while it is compatible the observationally determined values when AGN feedback is included. The kinematical and structural properties of the BCG are extremely different in the two models. When we do not include AGN feedback, the BCG is quickly rotating, with high Sérsic index, a clear mass excess in the center and a very large stellar mass fraction. When AGN feedback is considered, the BCG is slowly rotating, with a significantly cored surface density profile and low stellar mass fraction.
Structure and dynamics of massive galaxies at z=0 in a fully cosmological simulation
Authors: Ricciardelli E. , Navarro-González J. , Quilis V. , Vazdekis A.
Published: July 2013

In this contribution we present the results of an Eulerian adaptive mesh refinement (AMR) hydrodynamical and N-body simulation in a ΛCDM cosmology. The simulation used was performed with the cosmological code MASCLET (Quilis et al. 2004). Galaxies have been identified in the simulation outputs by means of an adaptive friends of friends algorithm applied to the star particles. To give light to our virtual galaxies we have assigned a spectrum to each stellar particle using the MIUSCAT stellar population models (Vazdekis et al. 2012; Ricciardelli et al. 2012).
Future prospects in observational galaxy evolution: towards increased resolution
Authors: Glazebrook Karl
Published: July 2013

Future prospects in observational galaxy evolution are reviewed from a personal perspective. New insights will especially come from high-redshift integral field kinematic data and similar low-redshift observations in very large and definitive surveys. We will start to systematically probe the mass structures of galaxies and their haloes via lensing from new imaging surveys and upcoming near-IR spectroscopic surveys will finally obtain large numbers of rest frame optical spectra at high-redshift routinely. ALMA will be an important new ingredient, spatially resolving the molecular gas fuelling the high star-formation rates seen in the early Universe.
Quantum internet using code division multiple access
Authors: Zhang Jing , Liu Yu-xi , Özdemir Şahin Kaya , Wu Re-Bing , Gao Feifei , Wang Xiang-Bin , Yang Lan , Nori Franco
Published: July 2013

A crucial open problem inS large-scale quantum networks is how to efficiently transmit quantum data among many pairs of users via a common data-transmission medium. We propose a solution by developing a quantum code division multiple access (q-CDMA) approach in which quantum information is chaotically encoded to spread its spectral content and then decoded via chaos synchronization to separate different sender-receiver pairs. In comparison to other existing approaches, such as frequency division multiple access (FDMA), the proposed q-CDMA can greatly increase the information rates per channel used, especially for very noisy quantum channels.
Time-resolved particle image velocimetry measurements of vortex and shear layer dynamics in the near wake of a tethered sphere
Authors: van Hout R. , Katz A. , Greenblatt D.
Published: July 2013

The coupling between shear layer, near wake dynamics, and structural oscillations downstream of a tethered spherical pendulum undergoing vortex induced vibrations (VIV) has been experimentally investigated using time-resolved particle image velocimetry in a wind tunnel. One quarter of the sphere was imaged in the field of view (spatial resolution 0.043D) that extended to 1.17D from the sphere's center (D is the sphere diameter). Reynolds numbers based on D, ranged between 493 ≤ Re ≤ 2218 and reduced velocities between 3.18 ≤ U* ≤ 14.1, covering a non-oscillating sphere, periodic oscillations, and the onset of non-stationary sphere oscillations. After the first Hopf bifurcation, the sphere exhibited large amplitude periodic oscillations and the near-wake vortices periodically interacted with the sphere and flapping shear layer. At U* = 5.97, a “secondary” counterclockwise rotating vortex seemed to facilitate shear layer pinch-off. In agreement with the onset of shear layer instabilities for a stationary sphere, only at Re = 2218 power spectra of velocity fluctuations inside the shear layer indicated a weak, broad frequency peak centered at 15 Hz similar as those measured for stationary cylinders and spheres. This peak was consistent with the results of linear instability theory indicating that despite the inherent three-dimensionality of the shear layer, its instability characteristics (at least for the Re investigated here) can be considered to be quasi-two-dimensional. Small-scale, near-wake structures were observed in the instantaneous swirling strength maps at all U* and it is conjectured here that their interaction with the sphere and separating shear layer is the feedback mechanism through which VIV occurs and is sustained.
Ions colliding with clusters of fullerenes—Decay pathways and covalent bond formations
Authors: Seitz F. , Zettergren H. , Rousseau P. , Wang Y. , Chen T. , Gatchell M. , Alexander J. D. , Stockett M. H. , Rangama J. , Chesnel J. Y. , Capron M. , Poully J. C. , Domaracka A. , Méry A. , Maclot S. , Vizcaino V. , Schmidt H. T. , Adoui L. , Alcamí M. , Tielens A. G. G. M. , Martín F. , Huber B. A. , Cederquist H.
Published: July 2013

We report experimental results for the ionization and fragmentation of weakly bound van der Waals clusters of n C60 molecules following collisions with Ar2 +, He2 +, and Xe20 + at laboratory kinetic energies of 13 keV, 22.5 keV, and 300 keV, respectively. Intact singly charged C60 monomers are the dominant reaction products in all three cases and this is accounted for by means of Monte Carlo calculations of energy transfer processes and a simple Arrhenius-type \documentclass[12pt]{minimal}\begin{document}$[{\rm C}_{60}]_n^+$\end{document}[C60]n+ → \documentclass[12pt]{minimal}\begin{document}${\rm C}_{60}^{+} + (n-1)\text{C}_{60}$\end{document}C60++(n−1)C60 evaporation model. Excitation energies in the range of only ∼0.7 eV per C60 molecule in a \documentclass[12pt]{minimal}\begin{document}$[{\rm C}_{60}]_{13}^+$\end{document}[C60]13+ cluster are sufficient for complete evaporation and such low energies correspond to ion trajectories far outside the clusters. Still we observe singly and even doubly charged intact cluster ions which stem from even more distant collisions. For penetrating collisions the clusters become multiply charged and some of the individual molecules may be promptly fragmented in direct knock-out processes leading to efficient formations of new covalent systems. For Ar2 + and He2 + collisions, we observe very efficient \documentclass[12pt]{minimal}\begin{document}${\rm C}_{119}^{+}$\end{document}C119+ and \documentclass[12pt]{minimal}\begin{document}${\rm C}_{118}^{+}$\end{document}C118+ formation and molecular dynamics simulations suggest that they are covalent dumb-bell systems due to bonding between \documentclass[12pt]{minimal}\begin{document}${\rm C}_{59}^{+}$\end{document}C59+ or \documentclass[12pt]{minimal}\begin{document}${\rm C}_{58}^{+}$\end{document}C58+ and C60 during cluster fragmentation. In the Ar2 + case, it is possible to form even smaller \documentclass[12pt]{minimal}\begin{document}${\rm C}_{120-2m}^{+}$\end{document}C120−2m+ molecules (m = 2–7), while no molecular fusion reactions are observed for the present Xe20 + collisions.
Lamination, stretching, and mixing in cat's eyes flip sequences with varying periods
Authors: Rossi Lionel , Doorly Denis , Kustrin Dimitri
Published: July 2013

This article explores the lamination, stretching, and mixing produced by sequences cyclically permuting a cat's eyes flow structure to stir the flow. Such sequences are experimentally driven by electromagnetic forces. Their intensity is kept constant between experiments while the duration of the forcing cycles varies over a decade. Mixing observations show that the mixing processes evolve from a seesaw stirring for short cycles (due to the regular rotation of the principal direction of the cat's eyes flow structures) to a cat's eyes stirring where the seesaw stirring is complemented by the rolling occurring within eddies. The transition from seesaw stirring to cat's eyes stirring is related to the persisting of the cat's eyes flow structure during one turnover time before it is flipped. Reference cases such as steady and random forcing configurations complement this exploration for comparison with the cat's eyes flip sequences. It is shown that cat's eyes flip sequences are efficient and possess baker-like mixing properties with an exponential growth for the length of interfaces and their lamination. The exponential coefficients of the stretching and lamination rates are conserved when varying the duration of the mixing cycles and using the generic cat's eyes flow turnover time as the reference of time to build these exponents. In particular, the stretching coefficients can be assumed as nearly constant when compared to the topological entropy which varies over a decade. This is attributed to the ability of the cat's eyes flip sequences to integrate lamination during the stirring sequences. This integration of the lamination compensates the reduction of flow's unsteadiness when increasing the duration of the mixing cycles so as to conserve a good stirring and mixing performance. Therefore, the lamination, stretching, and mixing of the cat's eyes flip sequences are robust to changes of the cycles’ duration.
A dynamical (e,2e) investigation of the structurally related cyclic ethers tetrahydrofuran, tetrahydropyran, and 1,4-dioxane
Authors: Builth-Williams J. D. , Bellm S. M. , Chiari L. , Thorn P. A. , Jones D. B. , Chaluvadi H. , Madison D. H. , Ning C. G. , Lohmann B. , da Silva G. B. , Brunger M. J.
Published: July 2013

Triple differential cross section measurements for the electron-impact ionization of the highest occupied molecular orbitals of tetrahydropyran and 1,4-dioxane are presented. For each molecule, experimental measurements were performed using the (e,2e) technique in asymmetric coplanar kinematics with an incident electron energy of 250 eV and an ejected electron energy of 20 eV. With the scattered electrons being detected at −5°, the angular distributions of the ejected electrons in the binary and recoil regions were observed. These measurements are compared with calculations performed within the molecular 3-body distorted wave model. Here, reasonable agreement was observed between the theoretical model and the experimental measurements. These measurements are compared with results from a recent study on tetrahydrofuran [D. B. Jones, J. D. Builth-Williams, S. M. Bellm, L. Chiari, C. G. Ning, H. Chaluvadi, B. Lohmann, O. Ingolfsson, D. Madison, and M. J. Brunger, Chem. Phys. Lett. 572, 32 (2013)] in order to evaluate the influence of structure on the dynamics of the ionization process across this series of cyclic ethers.
High-speed atomic force microscope combined with single-molecule fluorescence microscope
Authors: Fukuda Shingo , Uchihashi Takayuki , Iino Ryota , Okazaki Yasutaka , Yoshida Masato , Igarashi Kiyohiko , Ando Toshio
Published: July 2013

High-speed atomic force microscopy (HS-AFM) and total internal reflection fluorescence microscopy (TIRFM) have mutually complementary capabilities. Here, we report techniques to combine these microscopy systems so that both microscopy capabilities can be simultaneously used in the full extent. To combine the two systems, we have developed a tip-scan type HS-AFM instrument equipped with a device by which the laser beam from the optical lever detector can track the cantilever motion in the X- and Y-directions. This stand-alone HS-AFM system is mounted on an inverted optical microscope stage with a wide-area scanner. The capability of this combined system is demonstrated by simultaneous HS-AFM/TIRFM imaging of chitinase A moving on a chitin crystalline fiber and myosin V walking on an actin filament.
Penetrative phototactic bioconvection in an isotropic scattering suspension
Authors: Panda M. K. , Ghorai S.
Published: July 2013

Phototaxis is a directed swimming response dependent upon the light intensity sensed by micro-organisms. Positive (negative) phototaxis denotes the motion directed towards (away from) the source of light. Using the phototaxis model of Ghorai, Panda, and Hill [“Bioconvection in a suspension of isotropically scattering phototactic algae,” Phys. Fluids 22, 071901 (2010)]10.1063/1.3457163, we investigate two-dimensional phototactic bioconvection in an absorbing and isotropic scattering suspension in the nonlinear regime. The suspension is confined by a rigid bottom boundary, and stress-free top and lateral boundaries. The governing equations for phototactic bioconvection consist of Navier–Stokes equations for an incompressible fluid coupled with a conservation equation for micro-organisms and the radiative transfer equation for light transport. The governing system is solved efficiently using a semi-implicit second-order accurate conservative finite-difference method. The radiative transfer equation is solved by the finite volume method using a suitable step scheme. The resulting bioconvective patterns differ qualitatively from those found by Ghorai and Hill [“Penetrative phototactic bioconvection,” Phys. Fluids 17, 074101 (2005)]10.1063/1.1947807 at a higher critical wavelength due to the effects of scattering. The solutions show transition from steady state to periodic oscillations as the governing parameters are varied. Also, we notice the accumulation of micro-organisms in two horizontal layers at two different depths via their mean swimming orientation profile for some governing parameters at a higher scattering albedo.
How does the isomerization rate affect the photoisomerization-induced transport properties of a doped molecular glass-former?
Authors: Accary J.-B. , Teboul V.
Published: July 2013

We investigate the effect of the isomerization rate f on the microscopic mechanisms at the origin of the massive mass transport found in glass-formers doped with isomerizing azobenzene molecules that result in surface relief gratings formation. To this end we simulate the isomerization of dispersed probe molecules embedded into a molecular host glass-former. The host diffusion coefficient first increases linearly with f and then saturates. The saturated value of the diffusion coefficient and of the viscosity does not depend on f but increases with temperature while the linear response for these transport coefficients depends only slightly on the temperature. We interpret this saturation as arising from the appearance of increasingly soft regions around the probes for high isomerization rates, a result in qualitative agreement with experiments. These two different physical behaviors, linear response and saturation, are reminiscent of the two different unexplained mass transport mechanisms observed for small or large light intensities (for small intensities the molecules move towards the dark regions while for large intensities they move towards the illuminated regions).
Quantum tomography of a molecular bond in ice
Authors: Goldschleger I. U. , van Staveren M. N. , Ara Apkarian V.
Published: July 2013

We present the moving picture of a molecular bond, in phase-space, in real-time, at resolution limited by quantum uncertainty. The images are tomographically reconstructed Wigner distribution functions (WDF) obtained from four-wave mixing measurements on Br2-doped ice. The WDF completely characterizes the dissipative quantum evolution of the system, which despite coupling to the environment retains quantum coherence, as evidenced by its persistent negative Wigner hole. The spectral decomposition of the WDF allows a direct visualization of wavefunctions and spatiotemporal coherences of the system and the system-bath interaction. The measurements vividly illustrate nonclassical wave mechanics in a many-body system, in ordinary condensed matter.
Riemann problems and exact solutions to a traffic flow model
Authors: Curró C. , Manganaro N.
Published: July 2013

Within the theoretical framework of differential constraints method a nonhomogeneous model describing traffic flows is considered. Classes of exact solutions to the governing equations under interest are determined. Furthermore, Riemann problems and generalized Riemann problems which model situations of interest for traffic flows are solved.
Investigation of impurities in type-II InAs/GaSb superlattices via capacitance-voltage measurement
Authors: Chen G. , Hoang A. M. , Bogdanov S. , Haddadi A. , Bijjam P. R. , Nguyen B.-M. , Razeghi M.
Published: July 2013

Capacitance-voltage measurement was utilized to characterize impurities in the non-intentionally doped region of Type-II InAs/GaSb superlattice p-i-n photodiodes. Ionized carrier concentration versus temperature dependence revealed the presence of a kind of defects with activation energy below 6 meV and a total concentration of low 1015 cm−3. Correlation between defect characteristics and superlattice designs was studied. The defects exhibited a p-type behavior with decreasing activation energy as the InAs thickness increased from 7 to 11 monolayers, while maintaining the GaSb thickness of 7 monolayers. With 13 monolayers of InAs, the superlattice became n-type and the activation energy deviated from the p-type trend.
GeSi Raman spectra vs. local clustering/anticlustering: Percolation scheme and ab initio calculations
Authors: Pagès O. , Hussein R. Hajj , Torres V. J. B.
Published: July 2013

We formalize within the percolation scheme that operates along the linear chain approximation, i.e., at one dimension (1D), an intrinsic ability behind Raman scattering to achieve a quantitative insight into local clustering/anticlustering in an alloy, using GeSi as a case study. For doing so, we derive general expressions of the individual fractions of the six GeSi percolation-type oscillators [1×(Ge-Ge), 3×(Ge-Si), 2×(Si-Si)], which monitor directly the Raman intensities, via a relevant order parameter κ. This is introduced by adapting to the 1D oscillators of the GeSi-diamond version of the 1D-percolation scheme, i.e., along a fully consistent 1D treatment, the approach originally used by Verleur and Barker for the three-dimensional (3D) oscillators of their 1D-cluster scheme applying to zincblende alloys [H. W. Verleur and A. S. Barker, Phys. Rev. 149, 715 (1966)], a somehow problematic one in fact, due to its 3D–1D ambivalence. Predictive κ-dependent intensity-interplays between the Ge0.5Si0.5 Raman lines are confronted with existing experimental data and with ab initio Raman spectra obtained by using (32-atom) disordered supercells matching the required κ values, with special attention to the Ge-Si triplet and to the Si-Si doublet, respectively.
Spatial distribution of neutral oxygen vacancies on ZnO nanowire surfaces: An investigation combining confocal microscopy and first principles calculations
Authors: Mun Wong Kin , Alay-e-Abbas S. M. , Fang Yaoguo , Shaukat A. , Lei Yong
Published: July 2013

A qualitative approach using room-temperature confocal microscopy is employed to investigate the spatial distribution of shallow and deep oxygen vacancy (VO) concentrations on the polar (0001) and non-polar (101¯0) surfaces of zinc oxide (ZnO) nanowires (NWs). Using the spectral intensity variation of the confocal photoluminescence of the green emission at different spatial locations on the surface, the VO concentrations of an individual ZnO NW can be obtained. The green emission at different spatial locations on the ZnO NW polar (0001) and non-polar (101¯0) surfaces is found to have maximum intensity near the NW edges, decreasing to a minimum near the NW center. First-principles calculations using simple supercell-slab (SS) models are employed to approximate/model the defects on the ZnO NW (101¯0) and (0001) surfaces. These calculations give increased insight into the physical mechanism behind the green emission spectral intensity and the characteristics of an individual ZnO NW. The highly accurate density functional theory (DFT)-based full-potential linearized augmented plane-wave plus local orbitals (FP-LAPW + lo) method is used to compute the defect formation energy (DFE) of the SSs. Previously, using these SS models, it was demonstrated through the FP-LAPW + lo method that in the presence of oxygen vacancies at the (0001) surface, the phase transformation of the SSs in the graphite-like structure to the wurtzite lattice structure will occur even if the thickness of the graphite-like SSs are equal to or less than 4 atomic graphite-like layers [Wong et al., J. Appl. Phys. 113, 014304 (2013)]. The spatial profile of the neutral VO DFEs from the DFT calculations along the ZnO [0001] and [101¯0] directions is found to reasonably explain the spatial profile of the measured confocal luminescence intensity on these surfaces, leading to the conclusion that the green emission spectra of the NWs likely originate from neutral oxygen vacancies. Another significant result is that the variation in the calculated DFE along the ZnO [0001] and [101¯0] directions shows different behaviors owing to the non-polar and polar nature of these SSs. These results are important for tuning and understanding the variations in the optical response of ZnO NW-based devices in different geometric configurations.
Sensitivity enhancement of electro-optic polymer probing system using photo-isomerization and Fabry-Pérot effects
Authors: Kuo Wen-Kai , Su Tzu-Mao , Ke Zong-You , Lin Hui-Chi , Wu Chien-Jang
Published: July 2013

A sensitivity enhancement method for an external electro-optic (EO) probing system using a poled polymer as an EO sensor is proposed. A pumping laser, which induces the photo-isomerization effect in a prepoled EO polymer, and a tunable probing laser, which induces Fabry-Pérot effect, are combined to enhance the polymer EO sensor sensitivity. Results of an experiment with an EO sensor made of Disperse Red 1 poly(methy1 methacrylate) that demonstrates this combined effect are reported.