| 1. |
- Amanullah, Rahman, et al.
(författare)
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Spectra and Hubble Space Telescope Light Curves of Six Type Ia Supernovae at 0.511 < z < 1.12 and the Union2 Compilation
- 2010
-
Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 716, s. 712-738
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Tidskriftsartikel (refereegranskat)abstract
- We report on work to increase the number of well-measured Type Ia supernovae (SNe Ia) at high redshifts. Light curves, including high signal-to-noise Hubble Space Telescope data, and spectra of six SNe Ia that were discovered during 2001, are presented. Additionally, for the two SNe with z > 1, we present ground-based J-band photometry from Gemini and the Very Large Telescope. These are among the most distant SNe Ia for which ground-based near-IR observations have been obtained. We add these six SNe Ia together with other data sets that have recently become available in the literature to the Union compilation. We have made a number of refinements to the Union analysis chain, the most important ones being the refitting of all light curves with the SALT2 fitter and an improved handling of systematic errors. We call this new compilation, consisting of 557 SNe, the Union2 compilation. The flat concordance ΛCDM model remains an excellent fit to the Union2 data with the best-fit constant equation-of-state parameter w = -0.997+0.050 -0.054(stat)+0.077 -0.082(stat + sys together) for a flat universe, or w = -1.038+0.056 -0.059(stat)+0.093 -0.097(stat + sys together) with curvature. We also present improved constraints on w(z). While no significant change in w with redshift is detected, there is still considerable room for evolution in w. The strength of the constraints depends strongly on redshift. In particular, at z >~ 1, the existence and nature of dark energy are only weakly constrained by the data. Based in part on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute (STScI). STScI is operated by the Association of Universities for Research in Astronomy (AURA), Inc. under the NASA contract NAS 5-26555. The observations are associated with programs HST-GO-08585 and HST-GO-09075. Based, in part, on observations obtained at the ESO La Silla Paranal Observatory (ESO programs 67.A-0361 and 169.A-0382). Based, in part, on observations obtained at the Cerro-Tololo Inter-American Observatory (CTIO), National Optical Astronomy Observatory (NOAO). Based on observations obtained at the Canada-France-Hawaii Telescope (CFHT). Based, in part, on observations obtained at the Gemini Observatory (Gemini programs GN-2001A-SV-19 and GN-2002A-Q-31). Based, in part on observations obtained at the Subaru Telescope. Based, in part, on data that were obtained at the W. M. Keck Observatory.
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| 2. |
- Berg, Elisabeth Gräslund, et al.
(författare)
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Praktiker som gör skillnad : Om den verb-inriktade metoden
- 2013
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Ingår i: Historisk Tidskrift. - 0345-469X .- 2002-4827. ; 133:3, s. 335-354
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Tidskriftsartikel (refereegranskat)abstract
- This article discusses the so-called verb-oriented method and its role in the research project Gender and Work in early modern Sweden (GaW), which is based at Uppsala University. It provides a presentation of the GaW-database, which has been designed to allow analysis according to the verb-method. Finally, the article points out that this method can be combined with a number of different theoretical approaches as long as the focus is on practices. It is therefore compatible with the approaches of e.g., Judith Butler, Michel de Certeau, and Amartya Sen. Work is defined as "time-use with the purpose of making a living" and the article discusses why data on time-use, or actual work activities, are better suited for research into early modern Swedish working life than other types of data. It shows that activities are usually described in the sources by verb-phrases, and explains how and from what sources verb-phrases are collected and analyzed within the project. In order to allow for generalizations the verb-method presupposes large amounts of data. This is the rationale for the GaW-database, which at present includes around 5000 verb-phrases and 75000 data posts.
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| 3. |
- D'Andrea, Chris B., et al.
(författare)
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Type II-P Supernovae from the SDSS-II Supernova Survey and the Standardized Candle Method
- 2010
-
Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 708:1, s. 661-674
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Tidskriftsartikel (refereegranskat)abstract
- We apply the Standardized Candle Method (SCM) for Type II Plateau supernovae (SNe II-P), which relates the velocity of the ejecta of a SN to its luminosity during the plateau, to 15 SNe II-P discovered over the three season run of the Sloan Digital Sky Survey-II Supernova Survey. The redshifts of these SNe—0.027 < z < 0.144—cover a range hitherto sparsely sampled in the literature; in particular, our SNe II-P sample contains nearly as many SNe in the Hubble flow (z > 0.01) as all of the current literature on the SCM combined. We find that the SDSS SNe have a very small intrinsic I-band dispersion (0.22 mag), which can be attributed to selection effects. When the SCM is applied to the combined SDSS-plus-literature set of SNe II-P, the dispersion increases to 0.29 mag, larger than the scatter for either set of SNe separately. We show that the standardization cannot be further improved by eliminating SNe with positive plateau decline rates, as proposed in Poznanski et al. We thoroughly examine all potential systematic effects and conclude that for the SCM to be useful for cosmology, the methods currently used to determine the Fe II velocity at day 50 must be improved, and spectral templates able to encompass the intrinsic variations of Type II-P SNe will be needed. Based in part on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.
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| 4. |
- Dilday, Benjamin, et al.
(författare)
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A Measurement of the Rate of Type Ia Supernovae in Galaxy Clusters from the SDSS-II Supernova Survey
- 2010
-
Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 715, s. 1021-1035
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Tidskriftsartikel (refereegranskat)abstract
- We present measurements of the Type Ia supernova (SN) rate in galaxy clusters based on data from the Sloan Digital Sky Survey-II (SDSS-II) Supernova Survey. The cluster SN Ia rate is determined from 9 SN events in a set of 71 C4 clusters at z <= 0.17 and 27 SN events in 492 maxBCG clusters at 0.1 <= z <= 0.3. We find values for the cluster SN Ia rate of (0.37+0.17+0.01 -0.12-0.01) SNur h 2 and (0.55+0.13+0.02 -0.11-0.01) SNur h 2 (SNux = 10-12 L -1 xsun yr-1) in C4 and maxBCG clusters, respectively, where the quoted errors are statistical and systematic, respectively. The SN rate for early-type galaxies is found to be (0.31+0.18+0.01 -0.12-0.01) SNur h 2 and (0.49+0.15+0.02 -0.11-0.01) SNur h 2 in C4 and maxBCG clusters, respectively. The SN rate for the brightest cluster galaxies (BCG) is found to be (2.04+1.99+0.07 -1.11-0.04) SNur h 2 and (0.36+0.84+0.01 -0.30-0.01) SNur h 2 in C4 and maxBCG clusters, respectively. The ratio of the SN Ia rate in cluster early-type galaxies to that of the SN Ia rate in field early-type galaxies is 1.94+1.31+0.043 -0.91-0.015 and 3.02+1.31+0.062 -1.03-0.048, for C4 and maxBCG clusters, respectively. The SN rate in galaxy clusters as a function of redshift, which probes the late time SN Ia delay distribution, shows only weak dependence on redshift. Combining our current measurements with previous measurements, we fit the cluster SN Ia rate data to a linear function of redshift, and find rL = [(0.49+0.15 -0.14)+(0.91+0.85 -0.81) × z] SNuB h 2. A comparison of the radial distribution of SNe in cluster to field early-type galaxies shows possible evidence for an enhancement of the SN rate in the cores of cluster early-type galaxies. With an observation of at most three hostless, intra-cluster SNe Ia, we estimate the fraction of cluster SNe that are hostless to be (9.4+8.3 -5.1)%.
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| 5. |
- Dilday, Benjamin, et al.
(författare)
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Measurements of the Rate of Type Ia Supernovae at Redshift lsim0.3 from the Sloan Digital Sky Survey II Supernova Survey
- 2010
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 713, s. 1026-1036
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Tidskriftsartikel (refereegranskat)abstract
- We present a measurement of the volumetric Type Ia supernova (SN Ia) rate based on data from the Sloan Digital Sky Survey II (SDSS-II) Supernova Survey. The adopted sample of supernovae (SNe) includes 516 SNe Ia at redshift z <~ 0.3, of which 270(52%) are spectroscopically identified as SNe Ia. The remaining 246 SNe Ia were identified through their light curves; 113 of these objects have spectroscopic redshifts from spectra of their host galaxy, and 133 have photometric redshifts estimated from the SN light curves. Based on consideration of 87 spectroscopically confirmed non-Ia SNe discovered by the SDSS-II SN Survey, we estimate that 2.04+1.61 -0.95% of the photometric SNe Ia may be misidentified. The sample of SNe Ia used in this measurement represents an order of magnitude increase in the statistics for SN Ia rate measurements in the redshift range covered by the SDSS-II Supernova Survey. If we assume an SN Ia rate that is constant at low redshift (z < 0.15), then the SN observations can be used to infer a value of the SN rate of rV = (2.69+0.34+0.21 -0.30-0.01)×10-5 SNe yr-1 Mpc-3 (H 0/(70 km s-1 Mpc-1))3 at a mean redshift of ~0.12, based on 79 SNe Ia of which 72 are spectroscopically confirmed. However, the large sample of SNe Ia included in this study allows us to place constraints on the redshift dependence of the SN Ia rate based on the SDSS-II Supernova Survey data alone. Fitting a power-law model of the SN rate evolution, rV (z) = Ap × ((1 + z)/(1 + z 0))ν, over the redshift range 0.0 < z < 0.3 with z 0 = 0.21, results in Ap = (3.43+0.15 -0.15) × 10-5 SNe yr-1 Mpc-3 (H 0/(70 km s-1 Mpc-1))3 and ν = 2.04+0.90 -0.89.
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| 6. |
- Ekström, Linda, et al.
(författare)
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An improved course of glycaemia after a bread based breakfast is associated with beneficial effects on acute and semi-acute markers of appetite.
- 2016
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Ingår i: Food & Function. - : Royal Society of Chemistry (RSC). - 2042-6496 .- 2042-650X. ; 7:2, s. 1040-1047
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Tidskriftsartikel (refereegranskat)abstract
- The prevalence of type 2 diabetes mellitus is rapidly increasing all over the world and a diet promoting reduced glycaemic excursions in the postprandial phase may help to prevent the disease. In the present study guar gum (GG) and whole grain rye flour or high amylose maize starch (HAM) was combined to design bread products giving low and sustained glycaemia. A meal study was performed with young, healthy subjects and in addition to glucose and insulin, also subjective appetite ratings and biomarkers of appetite, voluntary energy intake at a second meal and markers of fermentation were studied. The combination of GG and rye was superior with improvements in subjective appetite whereas both test products lead to improvements in biomarkers of appetite compared to the white wheat bread reference. The inclusion of GG, rye and/or HAM in bread products show great potential in lowering risk factors associated with insulin resistance and improving acute and semi-acute appetite.
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| 7. |
- Ekström, Linda M N K, et al.
(författare)
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Oat β-glucan containing bread increases the glycaemic profile
- 2017
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Ingår i: Journal of Functional Foods. - : Elsevier BV. - 1756-4646. ; 32, s. 106-111
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Tidskriftsartikel (refereegranskat)abstract
- A net postprandial glucose increment beyond 2 h has been shown to improve glucose and appetite regulation at a subsequent meal. Such an improved glycaemic profile (GP) has been reported for bread containing guar gum. In the present study three commercially available β-glucans from barley and oat were baked into yeast leavened bread products. Only oat beta-glucan containing bread met the criteria of β-glucan molecular weight and was included in a meal study. The three levels of oat β-glucans reduced the GI and glucose iPeak by 32–37% compared to a white wheat reference bread. Furthermore, the highest oat β-glucan level increased GP by 66% compared to the reference bread. It is concluded that the oat β-glucans were suitable for use in baking, since the MW remained relatively high. Thus, the oat ingredient showed an interesting potential to be used when tailoring the glycaemic profile of bread products.
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| 8. |
- Ekström, Linda, et al.
(författare)
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On the possibility to affect the course of glycaemia, insulinaemia, and perceived hunger/satiety to bread meals in healthy volunteers.
- 2013
-
Ingår i: Food & Function. - : Royal Society of Chemistry (RSC). - 2042-6496 .- 2042-650X. ; 4:4, s. 522-529
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Tidskriftsartikel (refereegranskat)abstract
- Frequent hyperglycaemia is associated with oxidative stress and subclinical inflammation, and thus increased risk of cardiovascular disease. Possibilities of modulating glycaemia, insulinaemia and perceived satiety for bread products were investigated, with emphasis on the course of glycaemia expressed as a glycaemic profile (defined as the duration of the glucose curve above the fasting concentration divided by the incremental glucose peak). For this purpose white wheat bread was supplemented with whole grain corn flour with an elevated amylose content and different types and levels of guar gum. The bread products were characterised in vitro for release of starch degradation products and content of resistant starch. Fibre related fluidity following enzyme hydrolysis was also studied. By combining medium weight guar gum and whole grain corn flour with an elevated amylose content, the course of glycaemia, insulinaemia and subjective appetite ratings were improved compared to the reference white wheat bread. In addition, the combination beneficially influenced the content of resistant starch. Fluidity measurements showed potential to predict the glycaemic profile.
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| 9. |
- Frieman, Josh, et al.
(författare)
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The Sloan Digital Sky Survey-II Supernova Survey : Technical Summary
- 2008
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Ingår i: Astronomical Journal. - : American Astronomical Society. - 0004-6256 .- 1538-3881. ; 135:1, s. 338-347
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Tidskriftsartikel (refereegranskat)abstract
- The Sloan Digital Sky Survey-II (SDSS-II) has embarked on a multi-year project to identify and measure light curves for intermediate-redshift (0.05 < z < 0.35) Type Ia supernovae (SNe Ia) using repeated five-band (ugriz) imaging over an area of 300 sq. deg. The survey region is a stripe 2.5° wide centered on the celestial equator in the Southern Galactic Cap that has been imaged numerous times in earlier years, enabling construction of a deep reference image for the discovery of new objects. Supernova imaging observations are being acquired between September 1 and November 30 of 2005-7. During the first two seasons, each region was imaged on average every five nights. Spectroscopic follow-up observations to determine supernova type and redshift are carried out on a large number of telescopes. In its first two three-month seasons, the survey has discovered and measured light curves for 327 spectroscopically confirmed SNe Ia, 30 probable SNe Ia, 14 confirmed SNe Ib/c, 32 confirmed SNe II, plus a large number of photometrically identified SNe Ia, 94 of which have host-galaxy spectra taken so far. This paper provides an overview of the project and briefly describes the observations completed during the first two seasons of operation.
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| 10. |
- Galbany, Lluis, et al.
(författare)
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TYPE Ia SUPERNOVA PROPERTIES AS A FUNCTION OF THE DISTANCE TO THE HOST GALAXY IN THE SDSS-II SN SURVEY
- 2012
-
Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 755:2, s. 125-
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Tidskriftsartikel (refereegranskat)abstract
- We use Type Ia supernovae (SNe Ia) discovered by the Sloan Digital Sky Survey-II SN Survey to search for dependencies between SN Ia properties and the projected distance to the host-galaxy center, using the distance as a proxy for local galaxy properties (local star formation rate, local metallicity, etc.). The sample consists of almost 200 spectroscopically or photometrically confirmed SNe Ia at redshifts below 0.25. The sample is split into two groups depending on the morphology of the host galaxy. We fit light curves using both MLCS2k2 and SALT2, and determine color (A(V), c) and light-curve shape (Delta, x(1)) parameters for each SN Ia, as well as its residual in the Hubble diagram. We then correlate these parameters with both the physical and the normalized distances to the center of the host galaxy and look for trends in the mean values and scatters of these parameters with increasing distance. The most significant (at the 4 sigma level) finding is that the average fitted A(V) from MLCS2k2 and c from SALT2 decrease with the projected distance for SNe Ia in spiral galaxies. We also find indications that supernovae (SNe) in elliptical galaxies tend to have narrower light curves if they explode at larger distances, although this may be due to selection effects in our sample. We do not find strong correlations between the residuals of the distance moduli with respect to the Hubble flow and the galactocentric distances, which indicates a limited correlation between SN magnitudes after standardization and local host metallicity.
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| 11. |
- Johansson, Elin, et al.
(författare)
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Effects of wheat bran extract rich in arabinoxylan oligosaccharides and resistant starch on overnight glucose tolerance and markers of gut fermentation in healthy young adults.
- 2015
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Ingår i: European Journal of Nutrition. - : Springer Science and Business Media LLC. - 1436-6215 .- 1436-6207.
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Tidskriftsartikel (refereegranskat)abstract
- Specific combinations of dietary fiber (DF) have been observed to result in improved glucose tolerance at a subsequent standardized breakfast. Arabinoxylan oligosaccharides (AXOS) are considered as DF with prebiotic potential, but so far no studies have investigated their metabolic effects in humans. This randomized cross-over study evaluated the overnight impact of breads containing AXOS-rich wheat bran extract and resistant starch (RS, Hi-Maize), separately or combined, on glucose tolerance, related metabolic parameters and markers of gut fermentation in healthy subjects.
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| 12. |
- Kuninty, Praneeth R., et al.
(författare)
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MicroRNA-199a and -214 as potential therapeutic targets in pancreatic stellate cells in pancreatic tumor
- 2016
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Ingår i: Oncotarget. - : Impact press. - 1949-2553. ; 7:13, s. 16396-16408
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Tidskriftsartikel (refereegranskat)abstract
- Pancreatic stellate cells (PSCs) are the key precursor cells for cancer-associated fibroblasts (CAFs) in pancreatic tumor stroma. Although depletion of tumor stroma is debatable, attenuation of PSC activity is still an interesting strategy to treat pancreatic cancer. In this study, we explored miRNA as therapeutic targets in tumor stroma and found miR-199a-3p and miR-214-3p induced in patient-derived pancreatic CAFs as well as in TGF-β-activated human PSCs (hPSCs). Inhibition of miR-199a or miR-214 using their hairpin inhibitors in hPSCs significantly inhibited their TGFβ-induced differentiation (gene and protein levels of α-SMA, Collagen, PDGFβR), migration and proliferation. Furthermore, heterospheroids of Panc-1 and hPSCs were prepared, which attained smaller size when hPSCs were transfected with anti-miR-199a or -214 than those transfected with control anti-miR. The conditioned medium obtained from TGFβ-activated hPSCs induced tumor cell proliferation and endothelial cell tube formation, but these effects were abrogated when hPSCs were transfected with anti-miR-199a or miR-214. Moreover, IPA analyses revealed signaling pathways related to miR-199a (TP53, mTOR, Smad1) and miR-214 (PTEN, Bax, ING4). Taken together, this study reveals miR-199a-3p and miR-214-3p as major regulators of PSC activation and PSC-induced pro-tumoral effects, representing them as key therapeutic targets in PSCs in pancreatic cancer.
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| 13. |
- Lampeitl, Hubert, et al.
(författare)
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The Effect of Host Galaxies on Type Ia Supernovae in the SDSS-II Supernova Survey
- 2010
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 722, s. 566-576
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Tidskriftsartikel (refereegranskat)abstract
- We present an analysis of the host galaxy dependences of Type Ia Supernovae (SNe Ia) from the full three year sample of the SDSS-II Supernova Survey. We re-discover, to high significance, the strong correlation between host galaxy type and the width of the observed SN light curve, i.e., fainter, quickly declining SNe Ia favor passive host galaxies, while brighter, slowly declining Ia's favor star-forming galaxies. We also find evidence (at between 2σ and 3σ) that SNe Ia are sime0.1 ± 0.04 mag brighter in passive host galaxies than in star-forming hosts, after the SN Ia light curves have been standardized using the light-curve shape and color variations. This difference in brightness is present in both the SALT2 and MCLS2k2 light-curve fitting methodologies. We see evidence for differences in the SN Ia color relationship between passive and star-forming host galaxies, e.g., for the MLCS2k2 technique, we see that SNe Ia in passive hosts favor a dust law of RV = 1.0 ± 0.2, while SNe Ia in star-forming hosts require RV = 1.8+0.2 -0.4. The significance of these trends depends on the range of SN colors considered. We demonstrate that these effects can be parameterized using the stellar mass of the host galaxy (with a confidence of >4σ) and including this extra parameter provides a better statistical fit to our data. Our results suggest that future cosmological analyses of SN Ia samples should include host galaxy information.
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| 14. |
- Li, Xuri, et al.
(författare)
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PDGF-C is a new protease-activated ligand for the PDGF alpha-receptor.
- 2000
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Ingår i: Nat Cell Biol. - : Springer Science and Business Media LLC. - 1465-7392 .- 1476-4679. ; 2:5, s. 302-9
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Tidskriftsartikel (refereegranskat)abstract
- Platelet-derived growth factors (PDGFs) are important in many types of mesenchymal cell. Here we identify a new PDGF, PDGF-C, which binds to and activates the PDGF alpha-receptor. PDGF-C is activated by proteolysis and induces proliferation of fibroblasts when overexpressed in transgenic mice. In situ hybridization analysis in the murine embryonic kidney shows preferential expression of PDGF-C messenger RNA in the metanephric mesenchyme during epithelial conversion. Analysis of kidneys lacking the PDGF alpha-receptor shows selective loss of mesenchymal cells adjacent to sites of expression of PDGF-C mRNA; this is not found in kidneys from animals lacking PDGF-A or both PDGF-A and PDGF-B, indicating that PDGF-C may have a unique function.
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| 15. |
- Mega, Alessandro, et al.
(författare)
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Astrocytes enhance glioblastoma growth.
- 2020
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Ingår i: Glia. - : Wiley. - 0894-1491 .- 1098-1136. ; 68:2, s. 316-327
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Tidskriftsartikel (refereegranskat)abstract
- Glioblastoma (GBM) is a deadly disease with a need for deeper understanding and new therapeutic approaches. The microenvironment of glioblastoma has previously been shown to guide glioblastoma progression. In this study, astrocytes were investigated with regard to their effect on glioblastoma proliferation through correlative analyses of clinical samples and experimental in vitro and in vivo studies. Co-culture techniques were used to investigate the GBM growth enhancing potential of astrocytes. Cell sorting and RNA sequencing were used to generate a GBM-associated astrocyte signature and to investigate astrocyte-induced GBM genes. A NOD scid GBM mouse model was used for in vivo studies. A gene signature reflecting GBM-activated astrocytes was associated with poor prognosis in the TCGA GBM dataset. Two genes, periostin and serglycin, induced in GBM cells upon exposure to astrocytes were expressed at higher levels in cases with high "astrocyte signature score". Astrocytes were shown to enhance glioblastoma cell growth in cell lines and in a patient-derived culture, in a manner dependent on cell-cell contact and involving increased cell proliferation. Furthermore, co-injection of astrocytes with glioblastoma cells reduced survival in an orthotopic GBM model in NOD scid mice. In conclusion, this study suggests that astrocytes contribute to glioblastoma growth and implies this crosstalk as a candidate target for novel therapies.
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| 16. |
- Nordin, Jakob, et al.
(författare)
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EVIDENCE FOR A CORRELATION BETWEEN THE Si II lambda 4000 WIDTH AND TYPE Ia SUPERNOVA COLOR
- 2011
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 734:1, s. 42-
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Tidskriftsartikel (refereegranskat)abstract
- We study the pseudo-equivalent width of the Si II lambda 4000 feature of Type Ia supernovae (SNe Ia) in the redshift range 0.0024 <= z <= 0.634. We find that this spectral indicator correlates with the light curve color excess (SALT2c) as well as previously defined spectroscopic subclasses (Branch types) and the evolution of the Si II lambda 6150 velocity, i.e., the so-called velocity gradient. Based on our study of 55 objects from different surveys, we find indications that the Si II lambda 4000 spectral indicator could provide important information to improve cosmological distance measurements with SNe Ia.
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| 17. |
- Nordin, Jakob, et al.
(författare)
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Evidence for a correlation between the SiII λ4000 width and Type Ia supernova color
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357.
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Tidskriftsartikel (refereegranskat)abstract
- We study the pseudo equivalent width of the SiII λ4000 feature of Type Iasupernovae (SNe Ia) in the redshift range 0.0024 ≤z ≤0.634. We find that this spectral indicator correlateswith the light curve color excess SALT2 c as well as previouslydefined spectroscopic subclasses (Branch types) and theevolution of the SiII λ6150 velocity, i.e., the so called velocitygradient. Based on our study of 55 objects from different surveys, we find indications that the SiII λ4000 spectral indicatorcould provide important information to improve cosmological distancemeasurements with SNe Ia.
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| 18. |
- Nordin, Jakob, et al.
(författare)
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Properties of Type Ia supernova spectra up to z ~0.3
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Context: Distance estimates using Type Ia supernovae lead to the discovery of the accelerating universe a decade ago. Further high precision studies of the dynamics of the universe using supernovae are now limited by systematic uncertainties. Optical spectra of supernovae from follow-up observations of the SDSS-II Supernova Survey provide a natural testbed for investigating key uncertainties like a potential brightness evolution of the standard candle and the nature of the observed non-standard colour-brightness relation. Spectroscopic data also provides information needed to improve our understanding of the physical processes taking place in Type Ia supernova explosions. Aims: If supernova properties change with redshift, this may be detectable through comparisons of spectral indicators. Studies of individual supernovae are needed in order to determine whether explosionproperties, and not only the population distribution, change with redshift. Similarly, a possible intrinsic colour-brightness relation can be explored through correlations with spectral properties.Methods: We describe spectral indicator studies of spectra observed at the NTT and NOT during 2006 and 2007. These benefit from excellent multi-band SDSS photometry while being at cosmological distances (z=0.05-0.3) where evolution, limiting Type Ia supernovae as standarizable candles, could be present. We perform measurements of pseudo equivalent widths and line velocities as a function of redshift and lightcurve parameters. We also present multiple Monte Carlo studies designed to determine possible systematic errors in our spectral analysis arising when comparing local high S/N supernova spectra with lower S/N host-contaminated distant spectra.Reults: We do not detect any significant signs of evolution in individual Type Ia supernova spectra up to z=0.3. Better control of selection effects (both of the local and the distant sample) is needed in orderto determine whether a population drift exists. We can confirm correlations between pseudo equivalent widths and lightcurve shape (stretch) and see indications of correlations with supernova colours. We conclude that it is possible to compare individual low S/N supernova spectra with local ones, but that care must be taken during both noise filtering and host-galaxy subtraction. Host-galaxy contamination is the single largest source of systematic errors in our study, especially in the presence of differential slit loss.
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| 19. |
- Nordin, Jakob, et al.
(författare)
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Spectral properties of Type Ia supernovae up to z~0.3
- 2011
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 526, s. A119-
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Tidskriftsartikel (refereegranskat)abstract
- Aims: Spectroscopic observations of type Ia supernovae obtained at the New Technology Telescope (NTT) and the Nordic Optical Telescope (NOT), in conjunction with the SDSS-II Supernova Survey, are analysed. We use spectral indicators measured up to a month after the lightcurve peak luminosity to characterise the supernova properties, and examine these for potential correlations with host galaxy type, lightcurve shape, colour excess, and redshift. Methods: Our analysis is based on 89 type Ia supernovae at a redshift interval z = 0.05-0.3, for which multiband SDSS photometry is available. A lower-z spectroscopy reference sample was used for comparisons over cosmic time. We present measurements of time series of pseudo equivalent widths and line velocities of the main spectral features in type Ia supernovae. Results: Supernovae with shallower features are found predominantly among the intrinsically brighter slow declining supernovae. We detect the strongest correlation between lightcurve stretch and the Si ii λ4000 absorption feature, which also correlates with the estimated mass and star formation rate of the host galaxy. We also report a tentative correlation between colour excess and spectral properties. If confirmed, this would suggest that moderate reddening of type Ia supernovae is dominated by effects in the explosion or its immediate environment, as opposed to extinction by interstellar dust.
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| 20. |
- Sako, Masao, et al.
(författare)
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The Data Release of the Sloan Digital Sky Survey-II Supernova Survey
- 2018
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Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 130:988
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes the data release of the Sloan Digital Sky Survey-II (SDSS-II) Supernova Survey conducted between 2005 and 2007. Light curves, spectra, classifications, and ancillary data are presented for 10,258 variable and transient sources discovered through repeat ugriz imaging of SDSS Stripe 82, a 300 deg(2) area along the celestial equator. This data release is comprised of all transient sources brighter than r similar or equal to 22.5 mag with no history of variability prior to 2004. Dedicated spectroscopic observations were performed on a subset of 889 transients, as well as spectra for thousands of transient host galaxies using the SDSS-III BOSS spectrographs. Photometric classifications are provided for the candidates with good multi-color light curves that were not observed spectroscopically, using host galaxy redshift information when available. From these observations, 4607 transients are either spectroscopically confirmed, or likely to be, supernovae, making this the largest sample of supernova candidates ever compiled. We present a new method for SN host-galaxy identification and derive host-galaxy properties including stellar masses, star formation rates, and the average stellar population ages from our SDSS multi-band photometry. We derive SALT2 distance moduli for a total of 1364 SN. Ia with spectroscopic redshifts as well as photometric redshifts for a further 624 purely photometric SN. Ia candidates. Using the spectroscopically confirmed subset of the three-year SDSS-II SN. Ia sample and assuming a flat.CDM cosmology, we determine Omega(M) = 0.315 +/- 0.093 (statistical error only) and detect a non-zero cosmological constant at 5.7 sigma.
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| 21. |
- Stanishev, Vallery, et al.
(författare)
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Type Ia supernova Hubble diagram with near-infrared and optical observations
- 2018
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 615
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Tidskriftsartikel (refereegranskat)abstract
- Context. Type Ia Supernovae (SNe Ia) have been used as standardizable candles in the optical wavelengths to measure distances with an accuracy of similar to 7% out to redshift z similar to 1 : 5. There is evidence that in the near-infrared (NIR) wavelengths SNe Ia are even better standard candles, however, NIR observations are much more time-consuming.Aims. We aim to test whether the NIR peak magnitudes could be accurately estimated with only a single observation obtained close to maximum light, provided that the time of B band maximum, the B - V color at maximum and the optical stretch parameter are known.Methods. We present multi-epoch UBVRI and single-epoch J and H photometric observations of 16 SNe Ia in the redshift range z = 0 : 037 0 : 183, doubling the leverage of the current SN Ia NIR Hubble diagram and the number of SNe beyond redshift 0.04. This sample was analyzed together with 102 NIR and 458 optical light curves (LCs) of normal SNe Ia from the literature.Results. The analysis of 45 NIR LCs with well-sampled first maximum shows that a single template accurately describes the LCs if its time axis is stretched with the optical stretch parameter. This allows us to estimate the peak NIR magnitudes of SNe with only few observations obtained within ten days from B-band maximum. The NIR Hubble residuals show weak correlation with Delta M-15 and the color excess E(B V), and for the first time we report a potential dependence on the J(max) - H-max color. With these corrections, the intrinsic NIR luminosity scatter of SNe Ia is estimated to be similar to 0.10 mag, which is smaller than what can be derived for a similarly heterogeneous sample at optical wavelengths. Analysis of both NIR and optical data shows that the dust extinction in the host galaxies corresponds to a low R-V similar or equal to 1.8-1.9.Conclusions. We conclude that SNe Ia are at least as good standard candles in the NIR as in the optical and are potentially less affected by systematic uncertainties. We extended the NIR SN Ia Hubble diagram to its nonlinear part at z similar to 0 : 2 and confirmed that it is feasible to accomplish this result with very modest sampling of the NIR LCs, if complemented by well-sampled optical LCs. With future facilities it will be possible to extend the NIR Hubble diagram beyond redshift z similar or equal to 1; and our results suggest that the most efficient way to achieve this would be to obtain a single observation close to the NIR maximum.
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| 22. |
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Svenskans beskrivning 36 : Förhandlingar vid trettiosjätte sammankomsten. Uppsala 25–27 oktober 2017
- 2019
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Proceedings (redaktörskap) (refereegranskat)abstract
- Sedan 1963 har det vid olika universitet i Sverige och Finland regelbundet anordnats sammankomster för svenskans beskrivning. Vid dessa har forskningsresultat som rör svenska språkets uppbyggnad och användning presenterats och diskuterats.Den trettiosjätte sammankomsten ägde rum den 25–27 oktober 2017 i Uppsala. Temat för konferensen, som samlade runt 200 deltagare, var denna gång Varför svenska? Ambitionen var att på olika sätt belysa, problematisera och tydliggöra svenska språkets innebörd, roll och betydelse inom vetenskap, skola och samhälle. Sektionsföredragens ämnesmässiga spännvidd var som vanligt för konferensserien stor och föredragen berörde de flesta områden inom ämnet svenska språket.I denna volym publiceras i bearbetad form 27 av de föredrag som hölls vid sammankomsten. Den ger därmed en god överblick över aktuell forskning om svenska språket. Alla som vill följa den senaste utvecklingen på området finner här mycket av intresse.
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| 23. |
- Zheng, Chen, et al.
(författare)
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First-Year Spectroscopy for the Sloan Digital Sky Survey-II Supernova Survey
- 2008
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Ingår i: Astronomical Journal. - : American Astronomical Society. - 0004-6256 .- 1538-3881. ; 135:5, s. 1766-1784
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents spectroscopy of supernovae (SNe) discovered in the first season of the Sloan Digital Sky Survey-II SN Survey. This program searches for and measures multi-band light curves of SNe in the redshift range z = 0.05-0.4, complementing existing surveys at lower and higher redshifts. Our goal is to better characterize the SN population, with a particular focus on SNe Ia, improving their utility as cosmological distance indicators and as probes of dark energy. Our SN spectroscopy program features rapid-response observations using telescopes of a range of apertures, and provides confirmation of the SN and host-galaxy types as well as precise redshifts. We describe here the target identification and prioritization, data reduction, redshift measurement, and classification of 129 SNe Ia, 16 spectroscopically probable SNe Ia, 7 SNe Ib/c, and 11 SNe II from the first season. We also describe our efforts to measure and remove the substantial host-galaxy contamination existing in the majority of our SN spectra.
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| 24. |
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| 25. |
- Östman, Linda, et al.
(författare)
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Extinction properties of lensing galaxies
- 2008
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 485:2, s. 403-415
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Tidskriftsartikel (refereegranskat)
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| 26. |
- Östman, Linda, 1981-
(författare)
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Extragalactic extinction and spectral properties of Type Ia supernovae
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The use of Type Ia supernovae as standardisable candles for probing cosmological parameters with high precision requires good knowledge about how the supernova light is affected along the line of sight and how the intrinsic brightness varies between objects. The work in this thesis addresses these topics. One potential problem is if there is an evolution of the intrinsic brightness of Type Ia supernovae with redshift. To investigate this we have compared spectral features of intermediate-redshift supernovae with local ones. No redshift evolution could be detected up to z = 0.3. Correlations of the strength of some of the spectral features with supernova colour and lightcurve shape were found, in particular for the feature which primarily is a product of SiII 4130 absorption. Another difficulty concerns dust present in the line of sight which could both dim and redden the supernovae. We investigated dust extinction in distant galaxies by comparing the colours of background quasars with what is expected for different types of dust. A wide range of fitted values of Rv, the total-to-selective extinction ratio, was found, indicating that the dust properties in other galaxies could potentially be different from the Milky Way value, Rv ~ 3.1. The light could also be affected by an intergalactic dust population with an almost flat extinction curve. We found, using quasar observations, that any dimming larger than 0.2 magnitudes in the rest-frame B-band for a Type Ia supernova at z = 1 is ruled out. If the intergalactic dust has an extinction law similar to the one in the Milky Way, the corresponding limit would be 0.03 magnitudes. Another problem is that if axions exist, photons could be converted to axions over large cosmological distances, in the presence of magnetic fields, leading to a dimming of distant objects. For some model parameters, a dimming as large as 0.6 magnitudes for a Type Ia supernova at z = 1 would be allowed from quasar observations.
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| 27. |
- Östman, Linda, et al.
(författare)
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Limiting the dimming of distant type Ia supernovae
- 2005
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Ingår i: Journal of Cosmology and Astroparticle Physics. - : IOP Publishing. - 1475-7516. ; :2, s. 5-
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Tidskriftsartikel (refereegranskat)abstract
- Distant supernovae have been observed to be fainter than what is expected in a matter dominated universe. The most likely explanation is that the universe is dominated by an energy component with negative pressure, namely dark energy. However, there are several astrophysical processes that could, in principle, affect the measurements and in order to be able to take advantage of the growing supernova statistics, the control of systematic effects is crucial. We discuss two of these; extinction due to intergalactic grey dust and dimming due to photon-axion oscillations and show how their effect on supernova observations can be constrained using observed quasar colours and spectra. For a wide range of intergalactic dust models, we are able to rule out any dimming larger than 0.2 magnitudes for a type Ia supernova at z = 1. The corresponding limit for intergalactic Milky Way type dust is 0.03 magnitudes. For the more speculative model of photons mixing with axions, we find that the effect is independent of photon energy for certain combinations of parameter values and a dimming as large as 0.6 magnitudes cannot be ruled out. These effects can have profound implications for the possibility of constraining dark energy properties using supernova observations.
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| 28. |
- Östman, Linda, et al.
(författare)
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NTT and NOT spectroscopy of SDSS-II supernovae
- 2011
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 526, s. A28-
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Tidskriftsartikel (refereegranskat)abstract
- Context. The Sloan Digital Sky Survey II (SDSS-II) Supernova Survey, conducted between 2005 and 2007, was designed to detect a large number of type Ia supernovae around z ~ 0.2, the redshift "gap" between low-z and high-z supernova searches. The survey has provided multi-band (ugriz) photometric lightcurves for variable targets, and supernova candidates were scheduled for spectroscopic observations, primarily to provide supernova classification and accurate redshifts. We present supernova spectra obtained in 2006 and 2007 using the New Technology Telescope (NTT) and the Nordic Optical Telescope (NOT). Aims: We provide an atlas of supernova spectra in the range z = 0.03-0.32 that complements the well-sampled lightcurves from SDSS-II in the forthcoming three-year SDSS supernova cosmology analysis. The sample can, for example, be used for spectral studies of type Ia supernovae, which are critical for understanding potential systematic effects when supernovae are used to determine cosmological distances. Methods: The spectra were reduced in a uniform manner, and special care was taken in estimating the uncertainties for the different processing steps. Host-galaxy light was subtracted when possible and the supernova type fitted using the SuperNova IDentification code (SNID). We also present comparisons between spectral and photometric dating using SALT lightcurve fits to the photometry from SDSS-II, as well as the global distribution of our sample in terms of the lightcurve parameters: stretch and colour. Results: We report new spectroscopic data from 141 type Ia supernovae, mainly between -9 and +15 days from lightcurve maximum, including a few cases of multi-epoch observations. This homogeneous, host-galaxy subtracted, type Ia supernova spectroscopic sample is among the largest such data sets and unique in its redshift interval. The sample includes two potential SN 1991T-like supernovae (SN 2006on and SN 2007ni) and one potential SN 2002cx-like supernova (SN 2007ie). In addition, the new compilation includes spectra from 23 confirmed type II and 8 type Ib/c supernovae.
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