| 31. |
|
|
| 32. |
|
|
| 33. |
|
|
| 34. |
- Clayton, Geoffrey C., et al.
(författare)
-
THE CIRCUMSTELLAR ENVIRONMENT OF R CORONAE BOREALIS : WHITE DWARF MERGER OR FINAL-HELIUM-SHELL FLASH?
- 2011
-
Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 743:1, s. 44-
-
Tidskriftsartikel (refereegranskat)abstract
- In 2007, R Coronae Borealis (R CrB) went into a historically deep and long decline. In this state, the dust acts like a natural coronagraph at visible wavelengths, allowing faint nebulosity around the star to be seen. Imaging has been obtained from 0.5 to 500 mu m with Gemini/GMOS, Hubble Space Telescope/WFPC2, Spitzer/MIPS, and Herschel/SPIRE. Several of the structures around R CrB are cometary globules caused by wind from the star streaming past dense blobs. The estimated dust mass of the knots is consistent with their being responsible for the R CrB declines if they form along the line of sight to the star. In addition, there is a large diffuse shell extending up to 4 pc away from the star containing cool 25 K dust that is detected all the way out to 500 mu m. The spectral energy distribution of R CrB can be well fitted by a 150 AU disk surrounded by a very large diffuse envelope which corresponds to the size of the observed nebulosity. The total masses of the disk and envelope are 10(-4) and 2M(circle dot), respectively, assuming a gas-to-dust ratio of 100. The evidence pointing toward a white dwarf merger or a final-helium-shell flash origin for R CrB is contradictory. The shell and the cometary knots are consistent with a fossil planetary nebula. Along with the fact that R CrB shows significant lithium in its atmosphere, this supports the final-helium-shell flash. However, the relatively high inferred mass of R CrB and its high fluorine abundance support a white dwarf merger.
|
|
| 35. |
|
|
| 36. |
- Dawson, K. S., et al.
(författare)
-
An Intensive Hubble Space Telescope Survey for z>1 Type Ia Supernovae by Targeting Galaxy Clusters
- 2009
-
Ingår i: Astronomical Journal. - : American Astronomical Society. - 0004-6256 .- 1538-3881. ; 138, s. 1271-1283
-
Tidskriftsartikel (refereegranskat)abstract
- We present a new survey strategy to discover and study high-redshift Type Ia supernovae (SNe Ia) using the Hubble Space Telescope (HST). By targeting massive galaxy clusters at 0.9 < z < 1.5, we obtain a twofold improvement in the efficiency of finding SNe compared to an HST field survey and a factor of 3 improvement in the total yield of SN detections in relatively dust-free red-sequence galaxies. In total, sixteen SNe were discovered at z>0.95, nine of which were in galaxy clusters. This strategy provides an SN sample that can be used to decouple the effects of host-galaxy extinction and intrinsic color in high-redshift SNe, thereby reducing one of the largest systematic uncertainties in SN cosmology. Based on observations made with the NASA/ESA Hubble Space Telescope and obtained from the data archive at the Space Telescope Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc. under the NASA contract NAS 5-26555. The observations are associated with program 10496.
|
|
| 37. |
- Fotopoulou, S., et al.
(författare)
-
The XXL Survey VI. The 1000 brightest X-ray point sources
- 2016
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 592:A5
-
Forskningsöversikt (refereegranskat)abstract
- Context. X-ray extragalactic surveys are ideal laboratories for the study of the evolution and clustering of active galactic nuclei (AGN). Usually, a combination of deep and wide surveys is necessary to create a complete picture of the population. Deep X-ray surveys provide the faint population at high redshift, while wide surveys provide the rare bright sources. Nevertheless, very wide area surveys often lack the ancillary information available for modern deep surveys. The XXL survey spans two fields of a combined 50 deg(2) observed for more than 6Ms with XMM-Newton, occupying the parameter space that lies between deep surveys and very wide area surveys; at the same time it benefits from a wealth of ancillary data. Aims. This paper marks the first release of the XXL point source catalogue including four optical photometry bands and redshift estimates. Our sample is selected in the 2-10 keV energy band with the goal of providing a sizable sample useful for AGN studies. The limiting flux is F2-10 keV = 4.8 x 10(14) erg s(-1) cm(-2). Methods. We use both public and proprietary data sets to identify the counterparts of the X-ray point-like sources by means of a likelihood ratio test. We improve upon the photometric redshift determination for AGN by applying a Random Forest classification trained to identify for each object the optimal photometric redshift category (passive, star forming, starburst, AGN, quasi-stellar objects (QSO)). Additionally, we assign a probability to each source that indicates whether it might be a star or an outlier. We apply Bayesian analysis to model the X-ray spectra assuming a power-law model with the presence of an absorbing medium. Results. We find that the average unabsorbed photon index is = 1.85 +/- 0.40 while the average hydrogen column density is log i = 21.07 +/- 1.2 cm(-2). We find no trend of Gamma or N-H with redshift and a fraction of 26% absorbed sources (log N-H > 22) consistent with the literature on bright sources (log L-x > 44). The counterpart identification rate reaches 96.7% for sources in the northern field, 97.7% for the southern field, and 97.2% in total. The photometric redshift accuracy is 0.095 for the full XMM-XXL with 28% catastrophic outliers estimated on a sample of 339 sources. Conclusions. We show that the XXL-1000-AGN sample number counts extended the number counts of the COSMOS survey to higher fluxes and are fully consistent with the Euclidean expectation. We constrain the intrinsic luminosity function of AGN in the 2-10 keV energy band where the unabsorbed X-ray flux is estimated from the X-ray spectral fit up to z = 3. Finally, we demonstrate the presence of a supercluster size structure at redshift 0.14, identified by means of percolation analysis of the XXL-1000-AGN sample. The XXL survey, reaching a medium flux limit and covering a wide area, is a stepping stone between current deep fields and planned wide area surveys.
|
|
| 38. |
- Householder, John Ethan, et al.
(författare)
-
One sixth of Amazonian tree diversity is dependent on river floodplains
- 2024
-
Ingår i: NATURE ECOLOGY & EVOLUTION. - 2397-334X. ; 8, s. 901-911
-
Tidskriftsartikel (refereegranskat)abstract
- Amazonia's floodplain system is the largest and most biodiverse on Earth. Although forests are crucial to the ecological integrity of floodplains, our understanding of their species composition and how this may differ from surrounding forest types is still far too limited, particularly as changing inundation regimes begin to reshape floodplain tree communities and the critical ecosystem functions they underpin. Here we address this gap by taking a spatially explicit look at Amazonia-wide patterns of tree-species turnover and ecological specialization of the region's floodplain forests. We show that the majority of Amazonian tree species can inhabit floodplains, and about a sixth of Amazonian tree diversity is ecologically specialized on floodplains. The degree of specialization in floodplain communities is driven by regional flood patterns, with the most compositionally differentiated floodplain forests located centrally within the fluvial network and contingent on the most extraordinary flood magnitudes regionally. Our results provide a spatially explicit view of ecological specialization of floodplain forest communities and expose the need for whole-basin hydrological integrity to protect the Amazon's tree diversity and its function.
|
|
| 39. |
- Lin, HY, et al.
(författare)
-
KLK3 SNP-SNP interactions for prediction of prostate cancer aggressiveness
- 2021
-
Ingår i: Scientific reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 11:1, s. 9264-
-
Tidskriftsartikel (refereegranskat)abstract
- Risk classification for prostate cancer (PCa) aggressiveness and underlying mechanisms remain inadequate. Interactions between single nucleotide polymorphisms (SNPs) may provide a solution to fill these gaps. To identify SNP–SNP interactions in the four pathways (the angiogenesis-, mitochondria-, miRNA-, and androgen metabolism-related pathways) associated with PCa aggressiveness, we tested 8587 SNPs for 20,729 cases from the PCa consortium. We identified 3 KLK3 SNPs, and 1083 (P < 3.5 × 10–9) and 3145 (P < 1 × 10–5) SNP–SNP interaction pairs significantly associated with PCa aggressiveness. These SNP pairs associated with PCa aggressiveness were more significant than each of their constituent SNP individual effects. The majority (98.6%) of the 3145 pairs involved KLK3. The 3 most common gene–gene interactions were KLK3-COL4A1:COL4A2, KLK3-CDH13, and KLK3-TGFBR3. Predictions from the SNP interaction-based polygenic risk score based on 24 SNP pairs are promising. The prevalence of PCa aggressiveness was 49.8%, 21.9%, and 7.0% for the PCa cases from our cohort with the top 1%, middle 50%, and bottom 1% risk profiles. Potential biological functions of the identified KLK3 SNP–SNP interactions were supported by gene expression and protein–protein interaction results. Our findings suggest KLK3 SNP interactions may play an important role in PCa aggressiveness.
|
|
| 40. |
- Lu, Lingyi, et al.
(författare)
-
Chromosomes 4 and 8 implicated in a genome wide SNP linkage scan of 762 prostate cancer families collected by the ICPCG
- 2012
-
Ingår i: The Prostate. - : Wiley. - 0270-4137 .- 1097-0045. ; 72:4, s. 410-426
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND In spite of intensive efforts, understanding of the genetic aspects of familial prostate cancer (PC) remains largely incomplete. In a previous microsatellite-based linkage scan of 1,233 PC families, we identified suggestive evidence for linkage (i.e., LOD?=?1.86) at 5q12, 15q11, 17q21, 22q12, and two loci on 8p, with additional regions implicated in subsets of families defined by age at diagnosis, disease aggressiveness, or number of affected members. METHODS. In an attempt to replicate these findings and increase linkage resolution, we used the Illumina 6000 SNP linkage panel to perform a genome-wide linkage scan of an independent set of 762 multiplex PC families, collected by 11 International Consortium for Prostate Cancer Genetics (ICPCG) groups. RESULTS. Of the regions identified previously, modest evidence of replication was observed only on the short arm of chromosome 8, where HLOD scores of 1.63 and 3.60 were observed in the complete set of families and families with young average age at diagnosis, respectively. The most significant linkage signals found in the complete set of families were observed across a broad, 37cM interval on 4q13-25, with LOD scores ranging from 2.02 to 2.62, increasing to 4.50 in families with older average age at diagnosis. In families with multiple cases presenting with more aggressive disease, LOD cores over 3.0 were observed at 8q24 in the vicinity of previously identified common PC risk variants, as well as MYC, an important gene in PC biology. CONCLUSIONS. These results will be useful in prioritizing future susceptibility gene discovery efforts in thiscommon cancer. Prostate 72: 410-426, 2012. (C) 2011 Wiley Periodicals, Inc.
|
|
