Graphs with unique maximum independent sets

AbstractA graph is a unique independence graph if it has a unique maximum independent set. If, further, the complement of the maximum independent set is independent, the graph is a strong unique independence graph. We characterize strong unique independence graphs and unique independence trees

Beyond the “Historical” Simulation: Using Theories of History to Inform Scholarly Game Design.

The authors of this paper present a case for a gamic mode of history that focuses on the construction of the historical narrative via procedural rhetoric. The gamic mode of history presented in the paper maintains the constructionist epistemologies and explanatory narratives for the creation of reasonably justifiable truths found in many current text based works of scholarly history. It maintains them yet changes the mode to an interactive digital form where the reader explorers the historical argument through meaningful decision making and play. This paper establishes that the epistemologies of constructionist history are not mode dependent which allows for a change of mode without a change in epistemology. This is different from some other recent explorations of digital forms of history where in the pursuit of historical accurate reconstructions of the past researchers fail to address how we construct knowledge about the past, or assume that how we know the past much change with the mode of expression. It is suggested by this paper that in the gamic mode it is not the historical past and accepted epistemologies one should reconstruct, but simply the mode of the historical narrative about the past

Evidence for 1000 km/s Molecular Outflows in the Local ULIRG Population

The feedback from galactic outflows is thought to play an important role in shaping the gas content, star formation history, and ultimately the stellar mass function of galaxies. Here we present evidence for massive molecular outflows associated with ultra-luminous infrared galaxies (ULIRGs) in the coadded Redshift Search Receiver 12CO(1-0) spectrum. Our stacked spectrum of 27 ULIRGs at z = 0.043-0.11 (freq_rest = 110-120 GHz) shows broad wings around the CO line with delta_V(FWZI)~2000 km/s. Its integrated line flux accounts for up to 25+/-5% of the total CO line luminosity. When interpreted as a massive molecular outflow wind, the associated mechanical energy can be explained by a concentrated starburst with SFR \geq 100 M_sun/yr, which agrees well with their SFR derived from the FIR luminosity. Using the high signal-to-noise stacked composite spectrum, we also probe 13CO and 12CN emission in the sample and discuss how the chemical abundance of molecular gas may vary depending on the physical conditions of the nuclear region.Comment: 5 pages, 2 figures. Accepted for publication in ApJ

The Deep SWIRE Field. IV. First properties of the sub-mJy galaxy population: redshift distribution, AGN activity and star formation

We present a study of a 20cm selected sample in the Deep SWIRE VLA Field, reaching a limiting flux density of ~13.5 uJy at the image center. In a 0.6x0.6 square degrees field, we are able to assign an optical/IR counterpart to 97% of the radio sources. Up to 11 passbands from the NUV to 4.5um are then used to sample the spectral energy distribution (SED) of these counterparts in order to investigate the nature of the host galaxies. By means of an SED template library and stellar population synthesis models we estimate photometric redshifts, stellar masses, and stellar population properties, dividing the sample in three sub-classes of quiescent, intermediate and star-forming galaxies. We focus on the radio sample in the redshift range 0.3<z<1.3 where we estimate to have a redshift completeness higher than 90%, and study the properties and redshift evolution of these sub-populations. We find that, as expected, the relative contributions of AGN and star-forming galaxies to the uJy population depend on the flux density limit of the sample. At all flux levels a significant population of "green-valley" galaxies is observed. While the actual nature of these sources is not definitely understood, the results of this work may suggest that a significant fraction of faint radio sources might be composite (and possibly transition) objects, thus a simple "AGN vs star-forming" classification might not be appropriate to fully understand what faint radio populations really are.Comment: 18 pages, 16 figures, accepted for publication in Ap

A deep ATCA 20cm radio survey of the AKARI Deep Field South near the South Ecliptic Pole

The results of a deep 20 cm radio survey at 20 cm are reported of the AKARI Deep Field South (ADF-S) near the South Ecliptic Pole (SEP), using the Australia Telescope Compact Array telescope, ATCA. The survey has 1 sigma detection limits ranging from 18.7--50 microJy per beam over an area of ~1.1 sq degrees, and ~2.5 sq degrees to lower sensitivity. The observations, data reduction and source count analysis are presented, along with a description of the overall scientific objectives, and a catalogue containing 530 radio sources detected with a resolution of 6.2" x 4.9". The derived differential source counts show a pronounced excess of sources fainter than ~1 mJy, consistent with an emerging population of star forming galaxies. Cross-correlating the radio with AKARI sources and archival data we find 95 cross matches, with most galaxies having optical R-magnitudes in the range 18-24 mag, and 52 components lying within 1" of a radio position in at least one further catalogue (either IR or optical). We have reported redshifts for a sub-sample of our catalogue finding that they vary between galaxies in the local universe to those having redshifts of up to 0.825. Associating the radio sources with the Spitzer catalogue at 24 microns, we find 173 matches within one Spitzer pixel, of which a small sample of the identifications are clearly radio loud compared to the bulk of the galaxies. The radio luminosity plot and a colour-colour analysis suggest that the majority of the radio sources are in fact luminous star forming galaxies, rather than radio-loud AGN. There are additionally five cross matches between ASTE or BLAST submillimetre galaxies and radio sources from this survey, two of which are also detected at 90 microns, and 41 cross-matches with submillimetre sources detected in the Herschel HerMES survey Public Data release.Comment: MNRAS accepted and in press 9 July 2012: 28 pages, 15 Figures, 17 Table

Reliability of isometric and isokinetic trunk flexor strength using a functional electromechanical dynamometer

This paper will be part of Angela Rodriguez-Perea Doctoral Thesis performed in the Biomedicine Doctorate Program of the University of Granada, Spain. We would like to thank the Pleokinetic Network and the students of Catholic University of Most Holy Conception for making this study possible.Aim To determine the absolute and relative reliability of functional trunk tests, using a functional electromechanical dynamometer to evaluate the isokinetic strength of trunk flexors and to determine the most reliable assessment condition, in order to compare the absolute and relative reliability of mean force and peak force of trunk flexors and to determine which isokinetic condition of evaluation is best related to the maximum isometric. Methods Test-retest of thirty-seven physically active male student volunteers who performed the different protocols, isometric contraction and the combination of three velocities (V1 = 015 m s−1 , V2 = 0.30 m s−1, V3 = 0.45 m s−1) and two range of movement (R1 = 25% cm ; R2 = 50% cm) protocols. Results All protocols to evaluate trunk flexors showed an absolute reliability provided a stable repeatability for isometric and dynamic protocols with a coefficient of variation (CV) being below 10% and a high or very high relative reliability (0.69 0.86). The more reliable strength manifestation (CV = 6.82%) to evaluate the concentric contraction of trunk flexors was mean force, with 0.15 m s−1 and short range of movement (V1R1) condition. The most reliable strength manifestation to evaluate the eccentric contraction of trunk flexors was peak force, with 0.15 m s−1 and a large range of movement (V1R2; CV = 5.07%), and the most reliable way to evaluate isometric trunk flexors was by peak force (CV = 7.72%). The mean force of eccentric trunk flexor strength with 0.45 m s−1 and short range of movement (V3R1) condition (r = 0.73) was best related to the maximum isometric contraction. Conclusion Functional electromechanical dynamometry is a reliable evaluation system for assessment of trunk flexor strength

The Warm Molecular Gas Around the Cloverleaf Quasar

We present the first broadband lambda = 1 mm spectrum toward the z=2.56 Cloverleaf Quasar, obtained with Z-Spec, a 1-mm grating spectrograph on the 10.4-meter Caltech Submillimeter Observatory. The 190-305 GHz observation band corresponds to rest-frame 272 to 444 microns, and we measure the dust continuum as well as all four transitions of carbon monoxide (CO) lying in this range. The power-law dust emission, F_nu = 14 mJy (nu/240GHz)^3.9 is consistent with the published continuum measurements. The CO J=6->5, J=8->7, and J=9->8 measurements are the first, and now provide the highest-J CO information in this source. Our measured CO intensities are very close to the previously-published interferometric measurements of J=7->6, and we use all available transitions and our 13CO upper limits to constrain the physical conditions in the Cloverleaf molecular gas disk. We find a large mass (2-50x10^9 Msun) of highly-excited gas with thermal pressure nT > 10^6 Kcm^-3. The ratio of the total CO cooling to the far-IR dust emission exceeds that in the local dusty galaxies, and we investigate the potential heating sources for this bulk of warm molecular gas. We conclude that both UV photons and X-rays likely contribute, and discuss implications for a top-heavy stellar initial mass function arising in the X-ray-irradiated starburst. Finally we present tentative identifications of other species in the spectrum, including a possible detection of the H20 2_0,2->1_1,1 transition at lambda_rest = 303 microns.Comment: ApJ in press, 12 pages in emulateAp

Galaxy Properties from the Ultra-violet to the Far-Infrared: Lambda-CDM models confront observations

We combine a semi-analytic model of galaxy formation with simple analytic recipes describing the absorption and re-emission of starlight by dust in the interstellar medium of galaxies. We use the resulting models to predict galaxy counts and luminosity functions from the far-ultraviolet to the sub-mm, from redshift five to the present, and compare with an extensive compilation of observations. We find that in order to reproduce the rest-UV and optical luminosity functions at high redshift, we must assume an evolving normalization in the dust-to-metal ratio, implying that galaxies of a given bolometric luminosity (or metal column density) must be less extinguished than their local counterparts. In our best-fit model, we find remarkably good agreement with observations from rest-frame 1500 Angstroms to 250 microns. At longer wavelengths, most dramatically in the sub-mm, our models underpredict the number of bright galaxies by a large factor. The models reproduce the observed total IR luminosity function fairly well. We show the results of varying several ingredients of the models, including various aspects of the dust attenuation recipe, the dust emission templates, and the cosmology. We use our models to predict the integrated Extragalactic Background Light (EBL), and compare with an observationally-motivated EBL model and with other available observational constraints.Comment: 27 pages, 17 figures, 1 table, accepted to MNRAS, this version matches accepted manuscrip

Short gamma-ray bursts from dynamically-assembled compact binaries in globular clusters: pathways, rates, hydrodynamics and cosmological setting

We present a detailed assessment of the dynamical pathways leading to the coalescence of compact objects in Globular Clusters (GCs) and Short Gamma-Ray Burst (SGRB) production. We consider primordial binaries, dynamically formed binaries (through tidal two-body and three-body exchange interactions) and direct impacts of compact objects (WD/NS/BH). We show that if the primordial binary fraction is small, close encounters dominate the production rate of coalescing compact systems. We find that the two dominant channels are the interaction of field NSs with dynamically formed binaries, and two-body encounters. We then estimate the redshift distribution and host galaxy demographics of SGRB progenitors, and find that GCs can provide a significant contribution to the overall observed rate. We have carried out hydrodynamical modeling of evolution of close stellar encounters with WD/NS/BH, and show that there is no problem in accounting for the energy budget of a typical SGRB. The particulars of each encounter are variable and lead to interesting diversity: the encounter characteristics are dependent on the impact parameter, in contrast to the merger scenario; the nature of the compact star itself can produce very different outcomes; the presence of tidal tails in which material falls back onto the central object at later times is a robust feature of these calculations, with the mass involved being larger than for binary mergers. It is thus possible to account generically in this scenario for a prompt episode of energy release, as well as for activity many dynamical time scales later (abridged).Comment: Accepted for publication in ApJ (24 pages, 19 figures