| 1. |
- Altavilla, G., et al.
(författare)
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Type Ia SNe Along Redshift : The \mathcal {R}(Si II) Ratio and the Expansion Velocities in Intermediate-z Supernovae
- 2009
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 695, s. 135-148
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Tidskriftsartikel (refereegranskat)abstract
- We present a study of intermediate-z Type Ia supernovae (SNe Ia) using empirical physical diagrams which permit the investigation of those SNe explosions. This information can be very useful to reduce systematic uncertainties of the Hubble diagram of SNe Ia up to high z. The study of the expansion velocities and the measurement of the ratio \mathcal {R}(Si II) allow subtyping of SNe Ia as done in nearby samples. The evolution of this ratio as seen in the diagram \mathcal {R}(Si II)-(t) together with \mathcal {R}(Si II)max versus (B - V)0 indicates consistency of the properties at intermediate-z compared with the nearby SNe Ia. At intermediate-z, expansion velocities of Ca II and Si II are found similar to those of the nearby sample. This is found in a sample of six SNe Ia in the range 0.033 <=z<= 0.329 discovered within the International Time Programme of SNe Ia for Cosmology and Physics in the spring run of 2002.7The program run under Omega and Lambda from Supernovae and the Physics of Supernova Explosions within the International Time Programme at the telescopes of the European Northern Observatory (ENO) at La Palma (Canary Islands, Spain). Two SNe Ia at intermediate-z were of the cool FAINT type, one being an SN1986G-like object highly reddened. The \mathcal {R}(Si II) ratio as well as subclassification of the SNe Ia beyond templates help to place SNe Ia in their sequence of brightness and to distinguish between reddened and intrinsically red supernovae. This test can be done with very high z SNe Ia and it will help to reduce systematic uncertainties due to extinction by dust. It should allow to map the high-z sample into the nearby one.
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| 2. |
- 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
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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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| 3. |
- Dongiovanni, Paola, et al.
(författare)
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PCSK7 gene variation bridges atherogenic dyslipidemia with hepatic inflammation in NAFLD patients.
- 2019
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Ingår i: Journal of lipid research. - 1539-7262. ; 60:June, s. 1144-1153
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Tidskriftsartikel (refereegranskat)abstract
- Dyslipidemia and altered iron metabolism are typical features of non-alcoholic fatty liver disease (NAFLD). Proprotein Convertase Subtilisin/Kexin Type 7 (PCSK7) gene variation has been associated with circulating lipids and liver damage during iron overload. Aim of this study was to examine the impact of the PCSK7 rs236918 variant on NAFLD-related traits in 1,801 individuals from the Liver Biopsy Cohort (LBC), 500,000 from the UK Biobank Cohort (UKBBC), and 4,580 from the Dallas Heart Study (DHS). The minor PCSK7 rs236918 C allele was associated with higher triglycerides, aminotransferases and hepatic inflammation in the LBC (p<0.05) and with hypercholesterolemia and liver disease in the UKBBC. In the DHS, PCSK7 missense variants were associated with circulating lipids. PCSK7 was expressed in hepatocytes and its hepatic expression correlated with that of lipogenic genes (p<0.05). The rs236918 C allele was associated with upregulation of a new 'intra-PCSK7' lnc-RNA predicted to interact with the protein, higher hepatic and circulating PCSK7 protein (p<0.01), and the latter correlated with triglycerides (p=0.04). In HepG2, PCSK7 deletion reduced lipogenesis, fat accumulation, inflammation, TGFB pathway activation and fibrogenesis. In conclusion, PCSK7 gene variation is associated with dyslipidemia and more severe liver disease in high risk individuals, likely by modulating PCSK7 expression/activity.
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| 4. |
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| 5. |
- Garavini, G, et al.
(författare)
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Spectroscopic Observations and Analysis of the Peculiar SN 1999aa
- 2004
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Ingår i: Astronomical Journal. - : The American Astronomical Society.. - 0004-6256 .- 1538-3881. ; 128, s. 387-404
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Tidskriftsartikel (refereegranskat)abstract
- We present an extensive new time series of spectroscopic data of the peculiar SN 1999aa in NGC 2595. Ourdata set includes 25 optical spectra between 11 and +58 days with respect to B-band maximum light, providingan unusually complete time history. The early spectra resemble those of an SN 1991T–like object but with arelatively strong Ca H and K absorption feature. The first clear sign of Si ii k6355, characteristic of Type Iasupernovae, is found at day 7, and its velocity remains constant up to at least the first month after B-bandmaximum light. The transition to normal-looking spectra is found to occur earlier than in SN 1991T, suggestingSN 1999aa as a possible link between SN 1991T–like and Branch-normal supernovae. Comparing the observationswith synthetic spectra, doubly ionized Fe, Si, and Ni are identified at early epochs. These are characteristicof SN 1991T–like objects. Furthermore, in the day 11 spectrum, evidence is found for an absorptionfeature that could be identified as high velocity C ii k6580 or H. At the same epoch C iii k4648.8 at photosphericvelocity is probably responsible for the absorption feature at 4500 8. High-velocity Ca is found aroundmaximum light together with Si ii and Fe ii confined in a narrow velocity window. Implied constraints onsupernovae progenitor systems and explosion hydrodynamic models are briefly discussed.
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| 6. |
- Goobar, Ariel, et al.
(författare)
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Near-IR search for lensed supernovae behind galaxy clusters. II. First detection and future prospects
- 2009
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 507:1, s. 71-83
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Tidskriftsartikel (refereegranskat)abstract
- Aims: Powerful gravitational telescopes in the form of massive galaxy clusters can be used to enhance the light collecting power over a limited field of view by about an order of magnitude in flux. This effect is exploited here to increase the depth of a survey for lensed supernovae at near-IR wavelengths. Methods: We present a pilot supernova search programme conducted with the ISAAC camera at VLT. Lensed galaxies behind the massive clusters A1689, A1835, and AC114 were observed for a total of 20 h divided into 2, 3, and 4 epochs respectively, separated by approximately one month to a limiting magnitude J ≲ 24 (Vega). Image subtractions including another 20 h worth of archival ISAAC/VLT data were used to search for transients with lightcurve properties consistent with redshifted supernovae, both in the new and reference data. Results: The feasibility of finding lensed supernovae in our survey was investigated using synthetic lightcurves of supernovae and several models of the volumetric type Ia and core-collapse supernova rates as a function of redshift. We also estimate the number of supernova discoveries expected from the inferred star-formation rate in the observed galaxies. The methods consistently predict a Poisson mean value for the expected number of supernovae in the survey of between N_SN = 0.8 and 1.6 for all supernova types, evenly distributed between core collapse and type Ia supernovae. One transient object was found behind A1689, 0.5 arcsec from a galaxy with photometric redshift z_gal = 0.6 ± 0.15. The lightcurve and colors of the transient are consistent with being a reddened type IIP supernova at z_SN = 0.59. The lensing model predicts 1.4 mag of magnification at the location of the transient, without which this object would not have been detected in the near-IR ground-based search described in this paper (unlensed magnitude J ~ 25). We perform a feasibility study of the potential for lensed supernovae discoveries with larger and deeper surveys and conclude that the use of gravitational telescopes is a very exciting path for new discoveries. For example, a monthly rolling supernova search of a single very massive cluster with the HAWK-I camera at VLT would yield ≳ 10 lensed supernova lightcurves per year, where type Ia supernovae would constitute about half of the expected sample. Based on observations made with ESO telescopes at the La Silla Paranal Observatory under programme ID 079.A-0192 and ID 081.A-0734.
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| 7. |
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| 8. |
- Nobili, Serena, et al.
(författare)
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Constraining Dust and Color Variations of High-z SNe Using NICMOS on the Hubble Space Telescope
- 2009
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 700, s. 1415-1427
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Tidskriftsartikel (refereegranskat)abstract
- We present data from the Supernova Cosmology Project for five high redshift Type Ia supernovae (SNe Ia) that were obtained using the NICMOS infrared camera on the Hubble Space Telescope. We add two SNe from this sample to a rest-frame I-band Hubble diagram, doubling the number of high redshift supernovae on this diagram. This I-band Hubble diagram is consistent with a flat universe (ΩM, ΩΛ) = (0.29, 0.71). A homogeneous distribution of large grain dust in the intergalactic medium (replenishing dust) is incompatible with the data and is excluded at the 5σ confidence level, if the SN host galaxy reddening is corrected assuming RV = 1.75. We use both optical and infrared observations to compare photometric properties of distant SNe Ia with those of nearby objects. We find generally good agreement with the expected color evolution for all SNe except the highest redshift SN in our sample (SN 1997ek at z = 0.863) which shows a peculiar color behavior. We also present spectra obtained from ground-based telescopes for type identification and determination of redshift. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science 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 GO-07850.
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| 9. |
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| 10. |
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| 11. |
- Nobili, Serena, 1971-
(författare)
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Tests for systematic effects in supernova cosmology
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Type~Ia supernovae are used as standard candles to measure the energy density components of the universe. This led to the new paradigm in cosmology: only about 30\% of the universe is made by ordinary pressure-less matter, the rest is associated with an unknown form of energy with a negative equation of state parameter, called dark energy, able to drive the accelaration of the universe. The importance of this discovery requires to fully understand and control the possible systematic effects affecting both current and future measurements, aiming at probing the equation of state parameter, i.e. the nature of dark energy.In this thesis, we tackle systematic effects involved in several aspects of supernova cosmology. Studies of supernova colours are used for investigating the homogeneity of the standard candle and to improve the spectral templates used for $K$-corrections. We have measured the intrinsic colour dispersion and assessed its correlation between different epochs of supernova evolution. We develop a technique for fitting the $I$-band ligthcurve and present studies of correlations of its properties with the SN luminosity. Moreover, we present a pioneer study of restframe $I$-band Hubble diagram extended at redshift $\sim$ 0.5. This is found to be a valuable complementary tool for cosmological studies, and the results found are consistent with the concordance model of the universe, though the uncertainties are large. Presence of grey dust in the intergalactic medium is investigated both using the $I$-band Hubble diagram and supernova colour excess. Although the low statistics of the high redshift sample used do not allow to draw firm conclusions, both methods are tested and shown to be useful for probing the presence of intergalactic dust. The hypothesis of supernova population drift is tested in two different ways, both studying restframe $I$-band lightcurve properties and by comparing spectra of high redshift with those of nearby SNe. One distant supernova SN~2002fd (z=0.279) shows spectral similarities with 1991T/1999aa like objects. No signs of evolution in supernova properties is found in these studies, strengthening our confidence in the measured cosmological parameters.
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| 12. |
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| 13. |
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| 14. |
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| 15. |
- Rubin, D., et al.
(författare)
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Looking Beyond Lambda with the Union Supernova Compilation
- 2009
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 695, s. 391-403
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Tidskriftsartikel (refereegranskat)abstract
- The recent robust and homogeneous analysis of the world's supernova distance-redshift data, together with cosmic microwave background and baryon acoustic oscillation data—provides a powerful tool for constraining cosmological models. Here we examine particular classes of scalar field, modified gravity, and phenomenological models to assess whether they are consistent with observations even when their behavior deviates from the cosmological constant Λ. Some models have tension with the data, while others survive only by approaching the cosmological constant, and a couple are statistically favored over Λ cold dark matter. Dark energy described by two equation-of-state parameters has considerable phase space to avoid Λ and next-generation data will be required to constrain such physics, with the level of complementarity between probes varying with cosmology.
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| 16. |
- Stanishev, Vallery, et al.
(författare)
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Near-IR search for lensed supernovae behind galaxy clusters. I. Observations and transient detection efficiency
- 2009
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 507:1, s. 61-69
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Tidskriftsartikel (refereegranskat)abstract
- Context: Massive galaxy clusters at intermediate redshift can magnify the flux of distant background sources by several magnitudes. Aims: We exploit this effect to search for lensed distant supernovae that may otherwise be too faint to be detected. Methods: A supernova search was conducted at near infrared wavelengths using the ISAAC instrument at the VLT. The massive galaxy clusters Abell 1689, Abell 1835, and AC114 were observed for a total of 20 h to search for supernovae in gravitationally magnified background galaxies. The observations were split into individual epochs of 2 h of exposure time, separated by approximately one month. Image-subtraction techniques were used to search for transient objects with light curve properties consistent with supernovae, both in our new and archival ISAAC/VLT data. The limiting magnitude of the individual epochs was estimated by adding artificial stars to the subtracted images. Most of the epochs reach 90% detection efficiency at SZ(J) ≃ 23.8-24.0 mag (Vega). Results: Two transient objects, both in archival images of Abell 1689 and AC114, were detected. The transient in AC114 coincides - within the position uncertainty - with an X-ray source and is likely to be a variable AGN at the cluster redshift. The transient in Abell 1689 was found at SZ = 23.24 mag, ~0.5´´away from a galaxy with photometric redshift z_gal = 0.6 ± 0.15. The light curves and the colors of the transient are consistent with a reddened type IIP supernova at redshift z = 0.59 ± 0.05. The lensing model of Abell 1689 predicts ~1.4 mag of magnification at the position of the transient, making it the most magnified supernova ever found and only the second supernova found behind a galaxy cluster. Conclusions: Our pilot survey has demonstrated the feasibility to find distant gravitationally magnified supernovae behind massive galaxy clusters. One likely supernova was found behind Abell 1689, in accordance with the expectations for this survey, as shown in an accompanying analysis paper. Based on observations made with ESO telescopes at the Paranal Observatory under program IDs 079.A-0192 and 081.A-0734.
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| 17. |
- Stanishev, Vallery, et al.
(författare)
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SN 2003du: 480 days in the life of a normal type Ia supernova
- 2007
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 469:2, s. 645-661
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Tidskriftsartikel (refereegranskat)abstract
- Aims.We present a study of the optical and near-infrared (NIR) properties of the Type Ia Supernova (SN Ia) 2003du.Methods: An extensive set of optical and NIR photometry and low-resolution long-slit spectra was obtained using a number of facilities. The observations started 13 days before B-band maximum light and continued for 480 days with exceptionally good time sampling. The optical photometry was calibrated through the S-correction technique.Results: The {UBVRIJHK} light curves and the color indices of SN 2003du closely resemble those of normal SNe Ia. SN 2003du reached a B-band maximum of 13.49 ± 0.02 mag on JD2 452 766.38 ± 0.5. We derive a B-band stretch parameter of 0.988 ±0.003, which corresponds to Δ m15=1.02 ±0.05, indicative of a SN Ia of standard luminosity. The reddening in the host galaxy was estimated by three methods, and was consistently found to be negligible. Using an updated calibration of the V and {JHK} absolute magnitudes of SNe Ia, we find a distance modulus μ=32.79±0.15 mag to the host galaxy, UGC 9391. We measure a peak {uvoir} bolometric luminosity of 1.35(±0.20)×1043 erg s-1 and Arnett's rule implies that M56Ni≃0.68 ±0.14 Mȯ of 56Ni was synthesized during the explosion. Modeling of the {uvoir} bolometric light curve also indicates M56Ni in the range 0.6-0.8 Mȯ. The spectral evolution of SN 2003du at both optical and NIR wavelengths also closely resembles normal SNe Ia. In particular, the Si II ratio at maximum R(Si II) = 0.22 ±0.02 and the time evolution of the blueshift velocities of the absorption line minima are typical. The pre-maximum spectra of SN 2003du showed conspicuous high-velocity features in the Ca II H&K doublet and infrared triplet, and possibly in Si II λ6355, lines. We compare the time evolution of the profiles of these lines with other well-observed SNe Ia and we suggest that the peculiar pre-maximum evolution of Si II λ6355 line in many SNe Ia is due to the presence of two blended absorption components.
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