Cosmology with photometric redshift surveys

We explore the utility of future photometric redshift imaging surveys for delineating the large-scale structure of the Universe, and assess the resulting constraints on the cosmological model. We perform the following two complementary types of analysis. (i) We quantify the statistical confidence and the accuracy with which such surveys will be able to detect and measure characteristic features in the clustering power spectrum such as the acoustic oscillations and the turnover, in a 'model-independent' fashion. We show for example that a 10 000-deg2 imaging survey with depth r= 22.5 and photometric redshift accuracy δz/(1 +z) = 0.03 will detect the acoustic oscillations with 99.9 per cent confidence, measuring the associated preferred cosmological scale with 2 per cent precision. Such a survey will also detect the turnover with 95 per cent confidence, determining the corresponding scale with 20 per cent accuracy. (ii) By assuming a Λ cold dark matter (ΛCDM) model power spectrum we calculate the confidence with which a non-zero baryon fraction can be deduced from such future galaxy surveys. We quantify 'wiggle detection' by calculating the number of standard deviations by which the baryon fraction is measured, after marginalizing over the shape parameter. This is typically a factor of 4 more significant (in terms of number of standard deviations) than the above 'model-independent' result. For both analyses, we quantify the variation of the results with magnitude depth and photometric redshift precision, and discuss the prospects for obtaining the required performance with realistic future surveys. We conclude that the precision with which the clustering pattern may be inferred from future photometric redshift surveys will be competitive with contemporaneous spectroscopic redshift surveys, assuming that systematic effects can be controlled. We find that for equivalent wiggle detection power, a photometric redshift survey requires an area approximately 12[δz/(1 +z)]/0.03 times larger than a spectroscopic survey, for a given magnitude limit. We also note that an analysis of luminous red galaxies in the Sloan Digital Sky Survey may yield a marginal detection of acoustic oscillations in the imaging survey, in addition to that recently reported for the spectroscopic component

RXTE and ASCA Constraints on Non-thermal Emission from the A2256 Galaxy Cluster

An 8.3 hour observation of the Abell 2256 galaxy cluster using the Rossi X-ray Timing Explorer proportional counter array produced a high quality spectrum in the 2 - 30 keV range. Joint fitting with the 0.7 - 11 keV spectrum obtained with the Advanced Satellite for Astrophysics and Cosmology gas imaging spectrometer gives an upperlimit of 2.3x10^-7 photons/cm^2/sec/keV for non-thermal emission at 30 keV. This yields a lower limit to the mean magnetic field of 0.36 micro Gauss (uG) and an upperlimit of 1.8x10^-13 ergs/cm^3 for the cosmic-ray electron energy density. The resulting lower limit to the central magnetic field is ~1 - 3 uG While a magnetic field of ~0.1 - 0.2 uG can be created by galaxy wakes, a magnetic field of several uG is usually associated with a cooling flow or, as in the case of the Coma cluster, a subcluster merger. However, for A2256, the evidence for a merger is weak and the main cluster shows no evidence of a cooling flow. Thus, there is presently no satisfactory hypothesis for the origin of an average cluster magnetic field as high as >0.36 uG in the A2256 cluster.Comment: 8 pages, Astrophysical Journal (in press

VLBA Imaging of NGC 4261: Symmetric Parsec-scale Jets and the Inner Accretion Region

We observed the nuclear region of NGC 4261 (3C270) with the VLBA at two frequencies (1.6 and 8.4 GHz) simultaneously. We find that the position angle of the parsec-scale radio axis agrees, within the errors, with the position angle of the VLA-scale jet. Our observations also reveal basically symmetric radio structures at both 1.6 and 8.4 GHz. Analysis of these images shows that most of the central 10 pc of this source is not significantly affected by free-free absorption, even though HST images show that the nucleus contains a nearly edge-on disk of gas and dust on larger scales. Our highest angular resolution image shows a very narrow gap in emission, which we interpret as an absorption feature, just east of the radio core. This suggests that there may be a small, dense inner accretion disk whose width is less than 0.1 pc. If the inclination of this inner disk is close to that of the larger-scale HST disk it becomes optically thin to 8.4 GHz radiation at a deprojected radius of about 0.8 pc. The brightness of the pc-scale jets falls off very rapidly on both sides of the core, suggesting that the jets are rapidly expanding during the the first several pc of their travel. It appears that there is a small dense inner disk centered on the radio core (the base of the jets; less than 1 pc), a low density bubble filling most of the the inner several pc of the nucleus (within which the radio jets expand rapidly; ~10 pc), and a surrounding cool, higher density region (of which the HST absorption disk is part; tens to hundreds of pc) within which the transverse expansion of the radio jets, as implied by the rate of decrease in jet brightness, is nearly halted.Comment: Accepted by the Astrophysical Journa

The effect of processing and other factors on the colour characteristics of some red wines

Red wines were made from the same batch of Cascade grapes (Seibel 13.053) at Long Ashton by three different processing methods (a) extraction on the skins, (b) thermovinification and (c) carbonic maceration and were analysed at intervals. The wine made by thermovinification was much more coloured than that fermented on its skins, but it contained less anthocyanin and more polymeric pigment. The wine made by carbonic maceration was the least coloured, despite containing anthocyanins similar in amount to those in the thermovinified wine, and it appeared more brown. The red colour differences were attributed to variations in the physicochemical state of the anthocyanins and were expressed numerically in terms of their degrees of ionisation. There was a remarkably exact linear relationship between wine colour density and the degree of ionisation of the anthocyanins in the three wines.Factors affecting anthocyanin ionisation were studied in the Long Ashton wines and in some commercial young Beaujolais wines. Exposure to air augmented colour, increased anthocyanin polymerisation and, in some of the commercial wines, actually increased the amount of anthocyanins, presumably by oxidation of unknown colourless forms. The effects of adding acetaldehyde were even more striking. Large increases in the degree of ionisation of the anthocyanins occurred concurrently with losses of anthocyanins by further transformations into polymeric pigments. Of the Long Ashton wines, that made by thermovinification contained an excess of acetaldehyde over bisulphite, which was probably a factor augmenting its colour.lt was concluded that these fermentation and storage factors were superimposed upon the main effects which were attributed to the different mechanisms of anthocyanin-phenolic interactions operative under the various extraction procedures.Der Einfluß der Weinbereitung und anderer Faktoren auf die Farbmerkmale von RotweinenIn Long Ashton wurden aus demselben Lesegut von Cascade-Trauben (Seibel 13.053) Rotweine nach drei verschiedenen Verfahren - (a) Vergärung auf der Maische, (b) Maischeerhitzung, (c) Kohlensäuremazeration - hergestellt und in bestimmten zeitlichen Abständen analysiert. Der Wein nach (b) war viel intensiver gefärbt als derjenige nach (a); er enthielt jedoch weniger Anthocyan- und mehr polymere Farbstoffe. Der Wein nach (c) war am schwächsten gefärbt, obgleich er einen ähnlichen Anthocyangehalt aufwies wie nach (b) hergestellter Wein; außerdem war er stärker braun getönt. Die Unterschiede in der Rotfärbung wurden auf Schwankungen im physiko-chemischen Zustand der Anthocyane zurückgeführt und zahlenmäßig durch den Ionisationsgrad ausgedrückt. Zwischen der optischen Dichte der Rotweine und dem Ionisationsgrad ihrer Anthocyane bestand eine auffällig genaue lineare Beziehung. Bei den Weinen aus Long Ashton und einigen jungen Beaujolais-Weinen aus dem Handel wurden die Faktoren untersucht, welche die Ionisierung der Anthocyane beeinflussen. Einwirkung von Luft verstärkte die Färbung, steigerte die Polymerisation der Anthocyane und erhöhte bei einigen kommerziellen Weinen, wohl durch Oxidation unbekannter farbloser Vorstufen, den tatsächlichen Anthocyangehalt. Ein Zusatz von Acetaldehyd war noch wirkungsvoller: Ein beträchtlicher Zuwachs ionisierter Anthocyane war begleitet von Anthocyanverlusten durch verstärkte Umwandlung in polymere Farbstoffe. Bei den Weinen aus Long Ashton überwog in den nach (b) hergestellten das Acetaldehyd gegenüber dem Bisulfit, wodurch wahrscheinlich die Färbung vertieft wurde.Die unterschiedliche Ausprägung der Rotweinfärbung ist in erster Linie durch das angewandte Extraktionsverfahren bedingt, wobei Anthocyane und Phenole in verschiedener Weise miteinander reagieren. Im Verlauf der Gärung und Lagerung wird der Farbcharakter durch weitere Faktoren abgewandelt

Chandra observtaion of A2256 - a cluster at the early stage of merging

We present here \chandra observations of the rich cluster of galaxies A2256. In addition to the known cool subcluster, a new structure was resolved 2$'$ east of the peak of the main cluster. Its position is roughtly at the center of a low-brightness radio halo. Spectral analysis shows that the "shoulder" has high iron abundance ($\sim$ 1). We suggest that this structure is either another merging component or an internal structure of the main cluster. The X-ray redshifts of several regions were measured. The results agree with the optical ones and suggest that the main cluster, the subcluster and the "shoulder" are physically associated and interacting. The subcluster has low temperature ($\sim$ 4.5 keV) and high iron abundance ($\sim$ 0.6) in the central 150 kpc. The \chandra image shows a relatively sharp brightness gradient at the south of the subcluster peak running south-south-east (SSE). A temperature jump was found across the edge, with higher temperature ahead of the edge in the low density region. This phenomenon is qualitatively similar to the "cold fronts" found in A2142 and A3667. If the "shoulder" is ignored, the temperature map resembles those simulations at the early stage of merging while the subcluster approached the main cluster from somewhere west. This fact and the observed edge, in combination with the clear iron abundance contrast between the center of the subcluster ($\sim$ 0.6) and the main cluster ($\sim$ 0.2), all imply that the ongoing merger is still at the early stage. At least three member galaxies, including a radio head-tail galaxy, were found to have corresponding X-ray emission.Comment: The revised version. The shown abstract is shrunk. Accepted by ApJ. If it is possible, please try to look at the high-resolution version is http://cfa160.harvard.edu/~sunm/a2256.tar.g

Tristimulus measurements (CIELAB 76) of port wine colour

Tristimulus colour values were measured using the CIELAB 76 convention and compared with conventional measurements on 87 freshly-made and ageing single cultivar port wines from 5 sites for up to 6 years. There were high correlations between a* (redness) and A520nm, and saturation and colour density, and a high negative correlation between L* (Lightness) and colour density. There was little correlation between b* (yellowness) and A420nm; consequently hue angle did not correspond to tint. Amongst the tristimulus parameters, there were high correlations between L* or saturation and a*. In individual ports L* varied linearly but negatively with hue angle, but in the group of ports examined there was no significant relationship between L* and hue angle because of adc;litional variable phenolic browning depending upon cultivar. In model anthocyanin solutions increasing L* (by decreasing pigment concentration or increasing pH) caused a linear reduction in hue angle but an increase in tint; the latter was attributed to dissociation of associated anthocyanin molecules. Measurement of hue angle in ageing ports gives an indication of the relative occurrence of two competing ageing mechanisms, involving or not involving acetaldehyde. Hue angle is a more discriminating parameter for expressing the colour nuance of red wines than tint

A Comprehensive Radio and Optical Study of Abell 2256: Activity from an Infalling Group

Abell 2256 is a nearby (z~0.06), rich cluster of galaxies with fascinating observed properties across a range of wavelengths. Long believed to represent a cluster merger, recent X-ray and optical results have suggested that in addition to the primary cluster and subcluster there is evidence for a third, poorer system. We present wide-field, high sensitivity 1.4 GHz VLA radio observations of Abell 2256 in conjunction with optical imaging and additional spectroscopy. Over 40 cluster radio galaxies are identified, with optical spectroscopy indicating the emission source (star formation or AGN) for most of them. While the overall fraction of galaxies exhibiting radio emission is consistent with a large sample of other nearby clusters, we find an increase in the activity level of galaxies belonging to the third system (hereafter, the ``Group''). Specifically, the Group has relatively more star formation than both the primary cluster and main subcluster. The position of the Group is also coincident with the observed cluster radio relic. We suggest that the Group recently (~0.3 Gyr) merged with the primary cluster and that this merger, not the ongoing merger of the primary and the main subcluster, might be responsible for many of the unusual radio properties of Abell 2256. Furthermore, the greater star formation activity of the Group suggests that the infall of groups is an important driver of galaxy evolution in clusters.Comment: 21 pages plus 13 JPEG figures; to appear in the Astronomical Journa

Leg dominance effects on knee kinematics in unilateral and bilateral squats

Squatting movements are often used to assess known risk factors of injury such as knee valgus angle. This study aims to investigate the knee kinematics during unilateral and bilateral squats in relation to the dominant and non-dominant leg. Five uninjured participants completed three squats in three conditions; dominant unilateral, non-dominant unilateral and bilateral. Knee extension and valgus angles were calculated. Maximum knee valgus angle was higher in the non-dominant unilateral trial than the same leg during the bilateral squat (unilateral = 10.6°, bilateral = 8.4°; p < 0.05). Knee extension angles were significantly lower during bilateral squats (unilateral = 111.9° & 109.2°, bilateral = 97.5° & 98.2°; p < 0.05). Limb dominance effects knee valgus during squatting, and should therefore be taken into account during injury risk assessments

Social and physical environment independently affect oviposition decisions in Drosophila

In response to environmental stimuli, including variation in the presence of conspecifics, genotypes show highly plastic responses in behavioral and physiological traits influencing reproduction. Although extensively documented in males, such female responses are rather less studied. We expect females to be highly responsive to environmental variation and to differentially allocate resources to increase offspring fitness, given the major contribution of mothers to offspring number, size, and developmental conditions. Using Drosophila melanogaster, we (a) manipulate exposure to conspecific females, which mothers could use to anticipate the number of potential mates and larval density, and; (b) test how this interacts with the spatial distribution of potential oviposition sites, with females from higher densities expected to prefer clustered resources that can support a larger number of larvae. We found that high density females were slower to start copulating and reduced their copulation duration, the opposite effect to that observed in males. There was a parallel, perhaps related, effect on egg production: females previously housed in groups laid fewer eggs than those housed in solitude. Resource patchiness also influenced oviposition behavior: females preferred aggregated substrate, which attracted more females to lay eggs. However, we found no interaction between prior housing conditions and resource patchiness, indicating that females did not perceive the value of different resource distributions differently when exposed to environments that could signal expected levels of larval competition. We show that, although exposure to consexual competition changes copulatory behaviors of females, the distribution of oviposition resources has a greater effect on oviposition decisions

Nonthermal hard X-ray excess in the cluster Abell 2256 from two epoch observations

After confirmation of the presence of a nonthermal hard X-ray excess with respect to the thermal emission in the Coma cluster from two independent observations, obtained using the Phoswich Detection System onboard BeppoSAX, we present in this Letter also for Abell 2256 the results of two observations performed with a time interval of about 2.5 yr. In both spectra a nonthermal excess is present at a confidence level of ~3.3sigma and ~3.7sigma, respectively. The combined spectrum obtained by adding up the two spectra allows to measure an excess at the level of ~4.8sigma in the 20-80 keV energy range. The nonthermal X-ray flux is in agreement with the published value of the first observation (Fusco-Femiano et al. 2000) and with that measured by a Rossi X-Ray Timing Explorer observation (Rephaeli & Gruber 2003).Comment: 12 pages, 3 figures, 1 table - ApJL, in pres