The Arecibo Galaxy Environment Survey V : The Virgo Cluster (I)

We present 21 cm observations of a 10 $\times$ 2 degree region in the Virgo cluster, obtained as part of the Arecibo Galaxy Environment Survey. 289 sources are detected over the full redshift range (-2,000 $<$ $v$$_{hel}$ $<$ + 20,000 km/s) with 95 belonging to the cluster ($v$$_{hel}$ $<$ 3,000 km/s). We combine our observations with data from the optically selected Virgo Cluster Catalogue (VCC) and the Sloan Digital Sky Survey (SDSS). Most of our detections can be clearly associated with a unique optical counterpart, and 30% of the cluster detections are new objects fainter than the VCC optical completeness limit. 7 detections may have no optical counterpart and we discuss the possible origins of these objects. 7 detections appear associated with early-type galaxies. We perform HI stacking on the HI-undetected galaxies listed in the VCC in this region and show that they must have significantly less gas than those actually detected in HI. Galaxies undetected in HI in the cluster appear to be really devoid of gas, in contrast to a sample of field galaxies from ALFALFA.Comment: 23 pages, 22 figures, 4 table

Utilizing Force-State Mapping for Detecting Fatigue Damage Precursors in Aerospace Applications

The Force-State-Mapping (FSM) method is utilized to identify and monitor precursors to fatigue damage in aerospace alloy structures exposed to vibratory loads. The method is created originally to detect nonlinearity in a dynamical system via a direct non-parametric identification. In this paper, FSM is constructed at various stages of the fatigue-life using the Masri-Caughey method. The experimental results show that FSM is a sensitive indicator for monitoring the health state of a structure prior to the development of cracks. The required restoring force due to fatiguing is obtained as a function of the vibration cycles and input loads. FSM appears to be a promising method in connecting the global structural dynamic response to the evolution in the micro-behavior of the materials due to fatigue degradation. For aerospace applications, the objective of this effort is to estimate the required restoring force using current structural health monitoring systems and supply this value to the control laws of an aircraft. Thus, an aircraft can prevent or slow crack development by autonomously readjusting its maneuver based on its health-state

The HI content of Early-Type Galaxies from the ALFALFA survey I. Catalogued HI sources in the Virgo cluster

Aims: We are using the Arecibo Legacy Fast ALFA survey (ALFALFA), which is covering 17% of the sky at 21 cm, to study the HI content of Early-Type galaxies (ETG) in an unbiased way. The aim is to get an overall picture of the hot, warm and cold ISM of ETG, as a function of galaxy mass and environment, to understand its origin and fate, and to relate it to the formation and evolution history of these objects. Methods: This paper deals with the first part of our study, which is devoted to the 8-16 deg. declination strip in the Virgo cluster. In this sky region, using the Virgo Cluster Catalogue (VCC), we have defined an optical sample of 939 ETG, 457 of which are brighter than the VCC completeness limit at B_T=18.0. We have correlated this optical sample with the catalogue of detected HI sources from ALFALFA. Results: Out of the 389 ETG from the VCC with B_T<=18.0, outside the 1 deg. region of poor HI detection around M87, and corrected for background contamination of VCC galaxies without a known radial velocity, only 9 galaxies (2.3%) are detected in HI with a completeness limit of 3.5 and 7.6 x 10^7 Mo of HI for dwarf and giant ETG, respectively. In addition 4 VCC ETG with fainter magnitudes are also detected. Our HI detection rate is lower than previously claimed. The majority of the detected ETG appear to have peculiar morphology and to be located near the edges of the Virgo cluster. Conclusions: Our preliminary conclusion is that cluster ETG contain very little neutral gas, with the exceptions of a few peculiar dwarf galaxies at the edge of the ETG classification and of very few larger ETG, where the cold gas could have a recent external origin.Comment: Accepted for publication in Astronomy and Astrophysics; 6 pages, 3 figure

ALFALFA HI Data Stacking I. Does the Bulge Quench Ongoing Star Formation in Early-Type Galaxies?

We have carried out an HI stacking analysis of a volume-limited sample of ~5000 galaxies with imaging and spectroscopic data from GALEX and the Sloan Digital Sky Survey, which lie within the current footprint of the Arecibo Legacy Fast ALFA (ALFALFA) Survey. Our galaxies are selected to have stellar masses greater than 10^10 Msun and redshifts in the range 0.025<z<0.05. We extract a sub-sample of 1833 "early-type" galaxies with inclinations less than 70deg, with concentration indices C>2.6 and with light profiles that are well fit by a De Vaucouleurs model. We then stack HI line spectra extracted from the ALFALFA data cubes at the 3-D positions of the galaxies from these two samples in bins of stellar mass, stellar mass surface density, central velocity dispersion, and NUV-r colour. We use the stacked spectra to estimate the average HI gas fractions M_HI/M_* of the galaxies in each bin. Our main result is that the HI content of a galaxy is not influenced by its bulge. The average HI gas fractions of galaxies in both our samples correlate most strongly with NUV-r colour and with stellar surface density. The relation between average HI fraction and these two parameters is independent of concentration index C. We have tested whether the average HI gas content of bulge-dominated galaxies on the red sequence, differs from that of late-type galaxies on the red sequence. We find no evidence that galaxies with a significant bulge component are less efficient at turning their available gas reservoirs into stars. This result is in contradiction with the "morphological quenching" scenario proposed by Martig et al. (2009).Comment: 21 pages, 15 figures. Accepted for publication in MNRAS. Version with high resolution figures available at http://www.mpa-garching.mpg.de/GASS/pubs.ph

Spectral Evolution of Circinus X-1 Along its Orbit

We report on the spectral analysis of Circinus X-1 observed by the ASCA satellite in March 1998 along one orbital period. The luminosity of the source (in the 0.1-100 keV band) ranges from $2.5 \times 10^{38}$ erg s$^{-1}$ at the periastron (orbital phase 0.01) to $1.5 \times 10^{38}$ erg s$^{-1}$ at orbital phase 0.3. From the spectral analysis and the lightcurve we argue that Cir X-1 shows three states along the orbital evolution. The first state is at the orbital phase interval 0.97-0.3: the luminosity becames super-Eddington and a strong flaring activity is present. In this state a shock could form in the inner region of the system due to the super-Eddington accretion rate, producing an outflow of ionized matter whose observational signature could be the prominent absorption edge at $\sim 8.7$ keV observed in the energy spectrum at these phases. In the second state, corresponding to the orbital phase interval between 0.3 and 0.7, the accretion rate is sub-Eddington and we observe a weaker outflow, with smaller hydrogen column: the absorption edge is now at $\sim 8.3$ keV with an optical depth a factor of 2.5 to 6 smaller. The third state corresponds to the orbital phase interval 0.78-0.97. In this state the best fit model to the spectrum requires the presence of a partial covering component, indicating that the emission from the compact object is partially absorbed by neutral matter, probably the atmosphere of the companion star and/or the accreting matter from the companion.Comment: 18 pages, 3 figures. Accepted by Ap

Parkes HI observations of galaxies behind the southern Milky Way. II. The Crux and Great Attractor regions (l ~ 289 degree to 338 degree)

As part of our programme to map the large-scale distribution of galaxies behind the southern Milky Way, we observed 314 optically-selected, partially-obscured galaxies in the Zone of Avoidance (ZOA) in the Crux and Great Attractor (GA) regions. The observations were conducted with the Parkes 64m radio telescope, in a single-pixel pointed mode, reaching an rms noise level of typically 2-6 mJy over the velocity search range of 400<v<10500km/s. A total of 162 galaxies were detected. This can be explained by the prominence of the GA overdensity in the survey regions, which leads to a relatively higher fraction of nearby galaxies. It is also evident from the quite narrow velocity distribution (largely confined to 3000-6000km/s) and deviates significantly from the expectation of a uniform galaxy distribution for the given sensitivity and velocity range. No systematic differences were found between detections and non-detections, in terms of latitude, foreground extinction, or environment, except for the very central part of the rich Norma cluster, where hardly any galaxies were detected. A detailed investigation of the HI content of the galaxies reveals strong HI deficiency at the core of the Norma cluster (within about a 0.4 Abell radius), similar to what has been found in the Coma cluster. The redshifts obtained by this observing technique result in a substantial reduction of the so-called redshift ZOA. This is obvious when analysing the large-scale structure of the new HI data in combination with data from optical ZOA redshift surveys. The lower latitude detections provide further evidence of the extension of the Norma Wall, across the ZOA, in particular its bending towards the Cen-Crux clusters above the Galactic plane at slightly higher redshift, rather than a straight continuation towards the Centaurus clusters.Comment: 30 pages, 11 figures, including aa.cls; accepted by A

'Divided they stand, divided they fail': opposition politics in Morocco

The literature on democratization emphasises how authoritarian constraints usually lead genuine opposition parties and movements to form alliances in order to make demands for reform to the authoritarian regime. There is significant empirical evidence to support this theoretical point. While this trend is partly visible in the Middle East and North Africa, such coalitions are usually short-lived and limited to a single issue, never reaching the stage of formal and organic alliances. This article, using the case of Morocco, seeks to explain this puzzle by focusing on ideological and strategic differences that exist between the Islamist and the secular/liberal sectors of civil society, where significant opposition politics occurs. In addition, this article also aims to explain how pro-democracy strategies of the European Union further widen this divide, functioning as a key obstacle to democratic reforms

Palaeolithic extinctions and the Taurid Complex

Intersection with the debris of a large (50-100 km) short-period comet during the Upper Palaeolithic provides a satisfactory explanation for the catastrophe of celestial origin which has been postulated to have occurred around 12900 BP, and which presaged a return to ice age conditions of duration ~1300 years. The Taurid Complex appears to be the debris of this erstwhile comet; it includes at least 19 of the brightest near-Earth objects. Sub-kilometre bodies in meteor streams may present the greatest regional impact hazard on timescales of human concern.Comment: 7 pages, 3 figures; accepted for Monthly Notices of the Royal Astronomical Society (definitive version will be available at www.blackwell-synergy.com

Kinematics of the Local Universe XIII. 21-cm line measurements of 452 galaxies with the Nan\c{c}ay radiotelescope, JHK Tully-Fisher relation and preliminary maps of the peculiar velocity field

This paper presents 452 new 21-cm neutral hydrogen line measurements carried out with the FORT receiver of the meridian transit Nan\c{c}ay radiotelescope (NRT) in the period April 2003 -- March 2005. This observational programme is part of a larger project aiming at collecting an exhaustive and magnitude-complete HI extragalactic catalogue for Tully-Fisher applications (the so-called KLUN project, for Kinematics of the Local Universe studies, end in 2008). The whole on-line HI archive of the NRT contains today reduced HI-profiles for ~4500 spiral galaxies of declination delta > -40&deg; (http://klun.obs-nancay.fr). As an example of application, we use direct Tully-Fisher relation in three (JHK) bands in deriving distances to a large catalog of 3126 spiral galaxies distributed through the whole sky and sampling well the radial velocity range between 0 and 8000 km/s. Thanks to an iterative method accounting for selection bias and smoothing effects, we show as a preliminary output a detailed and original map of the velocity field in the Local Universe