4,803 research outputs found

    Absolute properties of BG Ind - a bright F3 system just leaving the Main Sequence

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    We present photometric and spectroscopic analysis of the bright detached eclipsing binary BG Ind. The masses of the components are found to be 1.428 +- 0.008 and 1.293 +- 0.008 Msun and the radii to be 2.290+-0.017 and 1.680+-0.038 Rsun for primary and secondary stars, respectively. Spectra- and isochrone-fitting coupled with color indices calibration yield [Fe/H]=-0.2+-0.1. At an age of 2.65+-0.20 Gyr BG Ind is well advanced in the main-sequence evolutionary phase - in fact, its primary is at TAMS or just beyond it. Together with three similar systems (BK Peg, BW Aqr and GX Gem) it offers an interesting opportunity to test the theoretical description of overshooting in the critical mass range 1.2-1.5 Msun.Comment: 8 pages, 5 figures, corrected bugs in author lis

    Transformation of Morphology and Luminosity Classes of the SDSS Galaxies

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    We present a unified picture on the evolution of galaxy luminosity and morphology. Galaxy morphology is found to depend critically on the local environment set up by the nearest neighbor galaxy in addition to luminosity and the large scale density. When a galaxy is located farther than the virial radius from its closest neighbor, the probability for the galaxy to have an early morphological type is an increasing function only of luminosity and the local density due to the nearest neighbor (ρn\rho_n). The tide produced by the nearest neighbor is thought to be responsible for the morphology transformation toward the early type at these separations. When the separation is less than the virial radius, i.e. when ρn>ρvirial\rho_n > \rho_{\rm virial}, its morphology depends also on the neighbor's morphology and the large-scale background density over a few Mpc scales (ρ20\rho_{20}) in addition to luminosity and ρn\rho_n. The early type probability keeps increasing as ρn\rho_n increases if its neighbor is an early type. But the probability decreases as ρn\rho_n increases when the neighbor is a late type. The cold gas streaming from the late type neighbor can be the reason for the morphology transformation toward late type. The overall early-type fraction increases as ρ20\rho_{20} increases when ρn>ρvirial\rho_n > \rho_{\rm virial}. This can be attributed to the hot halo gas of the neighbor which is confined by the pressure of the ambient medium held by the background mass. We have also found that galaxy luminosity depends on ρn\rho_n, and that the isolated bright galaxies are more likely to be recent merger products. We propose a scenario that a series of morphology and luminosity transformation occur through distant interactions and mergers, which results in the morphology--luminosity--local density relation.Comment: 14 pages, 7 figures, for higher resolution figures download PDF file at http://astro.kias.re.kr/docs/trans.pdf ; references added and typos in section 3.2 corrected; Final version accepted for publication in Ap

    The Relationship Between Baryons and Dark Matter in Extended Galaxy Halos

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    The relationship between gas-rich galaxies and Ly-alpha absorbers is addressed in this paper in the context of the baryonic content of galaxy halos. Deep Arecibo HI observations are presented of two gas-rich spiral galaxies within 125 kpc projected distance of a Ly-alpha absorber at a similar velocity. The galaxies investigated are close to edge-on and the absorbers lie almost along their major axes, allowing for a comparison of the Ly-alpha absorber velocities with galactic rotation. This comparison is used to examine whether the absorbers are diffuse gas rotating with the galaxies' halos, outflow material from the galaxies, or intergalactic gas in the low redshift cosmic web. The results indicate that if the gas resides in the galaxies' halos it is not rotating with the system and possibly counter-rotating. In addition, simple geometry indicates the gas was not ejected from the galaxies and there are no gas-rich satellites detected down to 3.6 - 7.5 x 10^6 Msun, or remnants of satellites to 5-6 x 10^{18} cm^{-2}. The gas could potentially be infalling from large radii, but the velocities and distances are rather high compared to the high velocity clouds around the Milky Way. The most likely explanation is the galaxies and absorbers are not directly associated, despite the vicinity of the spiral galaxies to the absorbers (58-77 kpc from the HI edge). The spiral galaxies reside in a filament of intergalactic gas, and the gas detected by the absorber has not yet come into equilibrium with the galaxy. These results also indicate that the massive, extended dark matter halos of spiral galaxies do not commonly have an associated diffuse baryonic component at large radii.Comment: Accepted by AJ, 33 pages preprint format, see http://www.astro.lsa.umich.edu/~mputman/putman1.pdf for a higher resolution versio

    Fabry Perot Halpha Observations of the Barred Spiral NGC 3367

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    We report the gross properties of the velocity field of the barred spiral galaxy NGC 3367. The following values were found: inclination with respect to the plane of the sky, i=30 deg; position angle (PA) of receding semi major axis PA=51 and systemic velocity V(sys)=3032 km/s. Large velocity dispersion are observed of upt o 120 km/s in the nuclear region, of up to 70 km/s near the eastern bright sources just beyond the edge of the stellar bar where three spiral arms seem to start and in the western bright sources at about 10 kpc. Deviations from normal circular velocities are observed from all the disk but mainly from the semi circle formed by the string of south western Halpha sources. An estimate of the dynamical mass is M(dyn)=2x10^11 Msolar.Comment: Accepted to be published in May 2001 issue in the A.J. 19 pages, 7 figure

    Acidification in Europe : A Simulation Model for Evaluating Control Strategies

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    RAINS (Regional Acidification Information and Simulation) is an integrated model of acidification in Europe designed as a tool for evaluating control strategies. It is currently sulfur-based, but is being expanded to include nitrogen species. Emphasis of the model is on the transboundary aspects of the acidification problem. Model computations are performed on a personal computer. Linked submodels are available for SO2 emissions, cost of control strategies, atmospheric transport of sulfur, forest soil and groundwater acidity, lake acidification, and the direct impact of SO2 on forests. The model can be used for scenario analysis, where the user prescribes a control strategy and then examines the cost and environmental consequences of this strategy, or for optimization analysis, in which the user sets cost and deposition goals, and identifies an "optimal" sulfur-reduction strategy. Preliminary use of the model has pointed to 1. the importance of examining long-term environmental consequences of control strategies, and 2. the cost advantages of a cooperative European sulfur-reduction program

    Colorectal cancer screening with fecal immunochemical testing or primary colonoscopy:An analysis of health equity based on a randomised trial

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    Background: We have addressed health equity attained by fecal immunochemical testing (FIT) and primary colonoscopy (PCOL), respectively, in the randomised controlled screening trial SCREESCO conducted in Sweden. Methods: We analysed data on the individuals recruited between March 2014, and March 2020, within the study registered with ClinicalTrials.gov, NCT02078804. Swedish population registry data on educational level, household income, country of birth, and marital status were linked to each 60-year-old man and woman who had been randomised to two rounds of FIT 2 years apart (n = 60,123) or once-only PCOL (n = 30,390). Furthermore, we geo-coded each study individual to his/her residential area and assessed neighbourhood-level data on deprivation, proportion of non-Western immigrants, population density, and average distance to healthcare center for colonoscopy. We estimated adjusted associations of each covariate with the colonoscopy attendance proportion out of all invited to respective arms; ie, the preferred outcome for addressing health equity. In the FIT arm, the test uptake and the colonoscopy uptake among the test positives were considered as the secondary outcomes. Findings: We found a marked socioeconomic gradient in the colonoscopy attendance proportion in the PCOL arm (adjusted odds ratio [95% credibility interval] between the groups categorised in the highest vs. lowest national quartile for household income: 2.20 [2.01-2.42]) in parallel with the gradient in the test uptake of the FIT x 2 screening (2.08 [1.96-2.20]). The corresponding gradient in the colonoscopy attendance proportion out of all invited to FIT was less pronounced (1.29 [1.16-1.42]), due to higher proportions of FIT positives in socioeconomically disadvantaged groups. Interpretation: The unintended risk of exacerbating inequalities in health by organised colorectal cancer screening may be higher with a PCOL strategy than a FIT strategy, despite parallel socioeconomic gradients in uptake

    Environmental Symbiont Acquisition May Not Be the Solution to Warming Seas for Reef-Building Corals

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    BACKGROUND: Coral reefs worldwide are in decline. Much of the mortality can be attributed to coral bleaching (loss of the coral's intracellular photosynthetic algal symbiont) associated with global warming. How corals will respond to increasing oceanic temperatures has been an area of extensive study and debate. Recovery after a bleaching event is dependent on regaining symbionts, but the source of repopulating symbionts is poorly understood. Possibilities include recovery from the proliferation of endogenous symbionts or recovery by uptake of exogenous stress-tolerant symbionts. METHODOLOGY/PRINCIPAL FINDINGS: To test one of these possibilities, the ability of corals to acquire exogenous symbionts, bleached colonies of Porites divaricata were exposed to symbiont types not normally found within this coral and symbiont acquisition was monitored. After three weeks exposure to exogenous symbionts, these novel symbionts were detected in some of the recovering corals, providing the first experimental evidence that scleractinian corals are capable of temporarily acquiring symbionts from the water column after bleaching. However, the acquisition was transient, indicating that the new symbioses were unstable. Only those symbiont types present before bleaching were stable upon recovery, demonstrating that recovery was from the resident in situ symbiont populations. CONCLUSIONS/SIGNIFICANCE: These findings suggest that some corals do not have the ability to adjust to climate warming by acquiring and maintaining exogenous, more stress-tolerant symbionts. This has serious ramifications for the success of coral reefs and surrounding ecosystems and suggests that unless actions are taken to reverse it, climate change will lead to decreases in biodiversity and a loss of coral reefs

    Three Different Types of Galaxy Alignment within Dark Matter Halos

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    Using a large galaxy group catalogue based on the Sloan Digital Sky Survey Data Release 4 we measure three different types of intrinsic galaxy alignment within groups: halo alignment between the orientation of the brightest group galaxies (BGG) and the distribution of its satellite galaxies, radial alignment between the orientation of a satellite galaxy and the direction towards its BGG, and direct alignment between the orientation of the BGG and that of its satellites. In agreement with previous studies we find that satellite galaxies are preferentially located along the major axis. In addition, on scales r < 0.7 Rvir we find that red satellites are preferentially aligned radially with the direction to the BGG. The orientations of blue satellites, however, are perfectly consistent with being isotropic. Finally, on scales r < 0.1 \Rvir, we find a weak but significant indication for direct alignment between satellites and BGGs. We briefly discuss the implications for weak lensing measurements.Comment: 4 pages, 4 figures, ApJL accepte

    Completeness of case ascertainment and survival time error in English cancer registries: impact on 1-year survival estimates

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    BACKGROUND: It has been suggested that cancer registries in England are too dependent on processing of information from death certificates, and consequently that cancer survival statistics reported for England are systematically biased and too low. METHODS: We have linked routine cancer registration records for colorectal, lung, and breast cancer patients with information from the Hospital Episode Statistics (HES) database for the period 2001-2007. Based on record linkage with the HES database, records missing in the cancer register were identified, and dates of diagnosis were revised. The effects of those revisions on the estimated survival time and proportion of patients surviving for 1 year or more were studied. Cases that were absent in the cancer register and present in the HES data with a relevant diagnosis code and a relevant surgery code were used to estimate (a) the completeness of the cancer register. Differences in survival times calculated from the two data sources were used to estimate (b) the possible extent of error in the recorded survival time in the cancer register. Finally, we combined (a) and (b) to estimate (c) the resulting differences in 1-year cumulative survival estimates. RESULTS: Completeness of case ascertainment in English cancer registries is high, around 98-99%. Using HES data added 1.9%, 0.4% and 2.0% to the number of colorectal, lung, and breast cancer registrations, respectively. Around 5-6% of rapidly fatal cancer registrations had survival time extended by more than a month, and almost 3% of rapidly fatal breast cancer records were extended by more than a year. The resulting impact on estimates of 1-year survival was small, amounting to 1.0, 0.8, and 0.4 percentage points for colorectal, lung, and breast cancer, respectively. INTERPRETATION: English cancer registration data cannot be dismissed as unfit for the purpose of cancer survival analysis. However, investigators should retain a critical attitude to data quality and sources of error in international cancer survival studies
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