Photometric Calibration of the Supernova Legacy Survey Fields

We present the photometric calibration of the Supernova Legacy Survey (SNLS) fields. The SNLS aims at measuring the distances to SNe Ia at (0.3<z<1) using MegaCam, the 1 deg^2 imager on the Canada-France-Hawaii Telescope (CFHT). The uncertainty affecting the photometric calibration of the survey dominates the systematic uncertainty of the key measurement of the survey, namely the dark energy equation of state. The photometric calibration of the SNLS requires obtaining a uniform response across the imager, calibrating the science field stars in each survey band (SDSS-like ugriz bands) with respect to standards with known flux in the same bands, and binding the calibration to the UBVRI Landolt standards used to calibrate the nearby SNe from the literature necessary to produce cosmological constraints. The spatial non-uniformities of the imager photometric response are mapped using dithered observations of dense stellar fields. Photometric zero-points against Landolt standards are obtained. The linearity of the instrument is studied. We show that the imager filters and photometric response are not uniform and publish correction maps. We present models of the effective passbands of the instrument as a function of the position on the focal plane. We define a natural magnitude system for MegaCam. We show that the systematics affecting the magnitude-to-flux relations can be reduced if we use the spectrophotometric standard star BD +17 4708 instead of Vega as a fundamental flux standard. We publish ugriz catalogs of tertiary standards for all the SNLS fields.Comment: 46 pages, 23 figures. Accepted by Astronomy and Astrophysics. Online material available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/ or alternatively from: http://supernovae.in2p3.fr/snls3/regnault09_cds.tar.g

A Precision Photometric Comparison between SDSS-II and CSP Type Ia Supernova Data

Consistency between Carnegie Supernova Project (CSP) and SDSS-II supernova (SN) survey ugri measurements has been evaluated by comparing SDSS and CSP photometry for nine spectroscopically confirmed Type Ia supernova observed contemporaneously by both programs. The CSP data were transformed into the SDSS photometric system. Sources of systematic uncertainty have been identified, quantified, and shown to be at or below the 0.023 magnitude level in all bands. When all photometry for a given band is combined, we find average magnitude differences of equal to or less than 0.011 magnitudes in ugri, with rms scatter ranging from 0.043 to 0.077 magnitudes. The u band agreement is promising, with the caveat that only four of the nine supernovae are well-observed in u and these four exhibit an 0.038 magnitude supernova-to-supernova scatter in this filter.Comment: This paper has been accepted for publication in The Astronomical Journa

Disruption of pro-oxidant and antioxidant systems with elevated expression of the ubiquitin proteosome system in the cachectic heart muscle of nude mice

BACKGROUND: Current research into the mechanisms of organ atrophy associated with cancer cachexia have centred on the loss of skeletal muscle, as it is one of the most profound physical changes of the disease. However, many patients with cancer cachexia also experience significant atrophy of the heart. The mechanisms causing cardiac tissue wastage in cancer cachexia are largely unknown. However, it is believed to involve a number of molecular interactions between the tumour and host. Increased levels of oxidative stress have been found in cancer cachectic skeletal muscle and has been linked to the activation of the ubiquitin proteosome system (UPS). The aim of the current study was to examine the role of oxidative stress and the UPS in the hearts of mice with cancer cachexia. METHODS: Oxidative damage to DNA (8-OH-2dG), mRNA levels of the ROS-producing enzymes NADPH oxidase (NOX), and xanthine oxidase (XDH), the antioxidant enzyme superoxide dismutase (SOD) and key components of the UPS was measured in the heart of mice with cancer cachexia. Protein expression levels of NOX enzyme subunits and SOD enzyme activity was also measured in the same heart samples. RESULTS: 8-OH-2dG levels were 1.5-fold higher in the heart of mice with cancer cachexia, and this was associated with a 1.7-fold lower level of NOX2 mRNA and twofold higher XDH mRNA in the same hearts. Cancer cachexia was also associated with a 1.5-fold lower level of SOD activity in the heart. Accompanying these pro- and antioxidant differences was a significantly higher level of mRNA for the key UPS elements MURF-1 (4.3=fold) and MAFbx (3.8-fold) in the hearts of mice with cancer cachexia. CONCLUSIONS: The current study demonstrated that cardiac atrophy of cachectic mice is associated with oxidative damage to DNA in the myocardium. The higher levels of XDH mRNA in cachectic hearts suggest that xanthine oxidase may have an important role to play in producing oxidative stress. It appears that the combination of higher XDH expression and lower SOD enzyme activity are key contributors to oxidative stress and cardiac tissue damage in cancer-induced cardiac atrophy. Oxidative stress in the myocardium as with skeletal muscle may also induce increased expression of the E3 ligases MURF-1 and MAFbx as seen in this study

A Mismatch in the Ultraviolet Spectra between Low-Redshift and Intermediate-Redshift Type Ia Supernovae as a Possible Systematic Uncertainty for Supernova Cosmology

We present Keck high-quality rest-frame ultraviolet (UV) through optical spectra of 21 Type Ia supernovae (SNe Ia) in the redshift range 0.11 < z < 0.37 and a mean redshift of 0.22 that were discovered during the Sloan Digital Sky Survey-II (SDSS-II) SN Survey. Using the broad-band photometry of the SDSS survey, we are able to reconstruct the SN host-galaxy spectral energy distributions (SEDs), allowing for a correction for the host-galaxy contamination in the SN Ia spectra. Comparison of composite spectra constructed from a subsample of 17 high-quality spectra to those created from a low-redshift sample with otherwise similar properties shows that the Keck/SDSS SNe Ia have, on average, extremely similar rest-frame optical spectra but show a UV flux excess. This observation is confirmed by comparing synthesized broad-band colors of the individual spectra, showing a difference in mean colors at the 2.4 - 4.4 sigma level for various UV colors. We further see a slight difference in the UV spectral shape between SNe with low-mass and high-mass host galaxies. Additionally, we detect a relationship between the flux ratio at 2770 and 2900 A and peak luminosity that differs from that observed at low redshift. We find that changing the UV SED of an SN Ia within the observed dispersion can change the inferred distance moduli by ~0.1 mag. This effect only occurs when the data probe the rest-frame UV. We suggest that this discrepancy could be due to differences in the host-galaxy population of the two SN samples or to small-sample statistics.Comment: 28 pages, 21 figures, accepted by AJ, spectra are available at http://www.cfa.harvard.edu/~rfoley/data

First-year Sloan Digital Sky Survey-II (SDSS-II) supernova results: consistency and constraints with other intermediate-redshift datasets

We present an analysis of the luminosity distances of Type Ia Supernovae from the Sloan Digital Sky Survey-II (SDSS-II) Supernova Survey in conjunction with other intermediate redshift (z<0.4) cosmological measurements including redshift-space distortions from the Two-degree Field Galaxy Redshift Survey (2dFGRS), the Integrated Sachs-Wolfe (ISW) effect seen by the SDSS, and the latest Baryon Acoustic Oscillation (BAO) distance scale from both the SDSS and 2dFGRS. We have analysed the SDSS-II SN data alone using a variety of "model-independent" methods and find evidence for an accelerating universe at >97% level from this single dataset. We find good agreement between the supernova and BAO distance measurements, both consistent with a Lambda-dominated CDM cosmology, as demonstrated through an analysis of the distance duality relationship between the luminosity (d_L) and angular diameter (d_A) distance measures. We then use these data to estimate w within this restricted redshift range (z<0.4). Our most stringent result comes from the combination of all our intermediate-redshift data (SDSS-II SNe, BAO, ISW and redshift-space distortions), giving w = -0.81 +0.16 -0.18(stat) +/- 0.15(sys) and Omega_M=0.22 +0.09 -0.08 assuming a flat universe. This value of w, and associated errors, only change slightly if curvature is allowed to vary, consistent with constraints from the Cosmic Microwave Background. We also consider more limited combinations of the geometrical (SN, BAO) and dynamical (ISW, redshift-space distortions) probes.Comment: 13 pages, 7 figures, accepted for publication in MNRA

The physical properties of star forming galaxies in the low redshift universe

(modified) We present a comprehensive study of the physical properties of \~10^5 galaxies with measurable star formation in the SDSS. By comparing physical information extracted from the emission lines with continuum properties, we build up a picture of the nature of star-forming galaxies at z<0.2. We take out essentially all aperture bias using resolved imaging, allowing an accurate estimate of the total SFRs in galaxies. We determine the SFR density to be 1.915^{+0.02}_{-0.01}(rand.)^{+0.14}_{-0.42} (sys.) h70 10^{-2} Msun/yr/Mpc^3 at z=0.1 (for a Kroupa IMF) and we study the distribution of star formation as a function of various physical parameters. The majority of the star formation in the low redshift universe takes place in moderately massive galaxies (10^10-10^11 Msun), typically in HSB disk galaxies. Roughly 15% of all star formation takes place in galaxies that show some sign of an active nucleus. About 20% occurs in starburst galaxies. We show that the present to past-average star formation rate, the Scalo b-parameter; is almost constant over almost three orders of magnitude in mass, declining only at M*>10^10 Msun. The volume averaged b parameter is 0.408^{+0.005}_{-0.002} (rand).^{+0.029}_{-0.090} (sys.) h70^{-1}. We use this value constrain the star formation history of the universe. In agreement with other work we find a correlation between $b$ and morphological type, as well as a tight correlation between the 4000AA break (D4000) and b. We discuss how D4000 can be used to estimate b parameters for high redshift galaxies.Comment: Accepted for MNRAS. Replaced with accepted version. A section on comparison with other methods of SFR estimation added and various updates have been made. The main results are almost unchange

First-year Sloan Digital Sky Survey-II (SDSS-II) Supernova Results: Hubble Diagram and Cosmological Parameters

We present measurements of the Hubble diagram for 103 Type Ia supernovae (SNe) with redshifts 0.04 < z < 0.42, discovered during the first season (Fall 2005) of the Sloan Digital Sky Survey-II (SDSS-II) Supernova Survey. These data fill in the redshift "desert" between low- and high-redshift SN Ia surveys. We combine the SDSS-II measurements with new distance estimates for published SN data from the ESSENCE survey, the Supernova Legacy Survey, the Hubble Space Telescope, and a compilation of nearby SN Ia measurements. Combining the SN Hubble diagram with measurements of Baryon Acoustic Oscillations from the SDSS Luminous Red Galaxy sample and with CMB temperature anisotropy measurements from WMAP, we estimate the cosmological parameters w and Omega_M, assuming a spatially flat cosmological model (FwCDM) with constant dark energy equation of state parameter, w. For the FwCDM model and the combined sample of 288 SNe Ia, we find w = -0.76 +- 0.07(stat) +- 0.11(syst), Omega_M = 0.306 +- 0.019(stat) +- 0.023(syst) using MLCS2k2 and w = -0.96 +- 0.06(stat) +- 0.12(syst), Omega_M = 0.265 +- 0.016(stat) +- 0.025(syst) using the SALT-II fitter. We trace the discrepancy between these results to a difference in the rest-frame UV model combined with a different luminosity correction from color variations; these differences mostly affect the distance estimates for the SNLS and HST supernovae. We present detailed discussions of systematic errors for both light-curve methods and find that they both show data-model discrepancies in rest-frame $U$-band. For the SALT-II approach, we also see strong evidence for redshift-dependence of the color-luminosity parameter (beta). Restricting the analysis to the 136 SNe Ia in the Nearby+SDSS-II samples, we find much better agreement between the two analysis methods but with larger uncertainties.Comment: Accepted for publication by ApJ

Clustering of the AKARI NEP deep field 24<i>μ</i>m selected galaxies

Aims. We present a method of selection of 24 μm galaxies from the AKARI north ecliptic pole (NEP) deep field down to 150 μJy and measurements of their two-point correlation function. We aim to associate various 24 μm selected galaxy populations with present day galaxies and to investigate the impact of their environment on the direction of their subsequent evolution. Methods. We discuss using of Support Vector Machines (SVM) algorithm applied to infrared photometric data to perform star-galaxy separation, in which we achieve an accuracy higher than 80%. The photometric redshift information, obtained through the CIGALE code, is used to explore the redshift dependence of the correlation function parameter (r0) as well as the linear bias evolution. This parameter relates galaxy distribution to the one of the underlying dark matter. We connect the investigated sources to their potential local descendants through a simplified model of the clustering evolution without interactions. Results. We observe two different populations of star-forming galaxies, at zmed ∼ 0.25, zmed ∼ 0.9. Measurements of total infrared luminosities (LTIR) show that the sample at zmed ∼ 0.25 is composed mostly of local star-forming galaxies, while the sample at zmed ∼ 0.9 is composed of luminous infrared galaxies (LIRGs) with LTIR ∼ 1011.62 L⨀. We find that dark halo mass is not necessarily correlated with the LTIR: for subsamples with LTIR = 1011.15 L⨀ at zmed ∼ 0.7 we observe a higher clustering length (r0 = 6.21 ± 0.78 [h−1Mpc]) than for a subsample with mean LTIR = 1011.84 L⨀ at zmed ∼ 1.1 (r0 = 5.86 ± 0.69 h−1Mpc). We find that galaxies at zmed ∼ 0.9 can be ancestors of present day L∗ early type galaxies, which exhibit a very high r0 ∼ 8h−1 Mpc.</p