Showing papers by "Peter Nugent published in 2002"
TL;DR: In this article, a method for performing generalized K-corrections for Type Ia supernovae is presented, which allows us to compare these objects from the UV to near-IR over the redshift range 0 < z < 2.
Abstract: The measurement of the cosmological parameters from Type Ia supernovae hinges on our ability to compare nearby and distant supernovae accurately. Here we present an advance on a method for performing generalized K-corrections for Type Ia supernovae which allows us to compare these objects from the UV to near-IR over the redshift range 0 < z < 2. We discuss the errors currently associated with this method and how future data can improve upon it significantly. We also examine the effects of reddening on the K-corrections and the light curves of Type Ia supernovae. Finally, we provide a few examples of how these techniques affect our current understanding of a sample of both nearby and distant supernovae.
349 citations
TL;DR: The Nearby Supernova Factory (SNfactory) as mentioned in this paper is an international experiment designed to lay the foundation for the next generation of cosmology experiments (such as CFHTLS, wP, SNAP and LSST) which will measure the expansion history of the Universe using Type Ia supernovae.
Abstract: Overview of the Nearby Supernova Factory G. Aldering a , G. Adam b , P. Antilogus c , P. Astier d , R. Bacon b , S. Bongard c , C. Bonnaud b , Y. Copin c , D. Hardin d , F. Henault b , D. A. Howell a , J.-P. Lemonnier b , J.-M. Levy d , S. Loken a , P. Nugent a , R. Pain d , A. Pecontal b , E. Pecontal b , S. Perlmutter a , R. Quimby a , K. Schahmaneche d , G. Smadja c , and W.M. Wood-Vasey a , the Nearby Supernova Factory collaboration Berkeley National Laboratory, Berkeley CA, USA de Recherche Astronomique, Universite Lyon I and Ecole Normale Superieure, Lyon, France c Institut de Physique Nucleaire, Universite Lyon I, Lyon, France d Laboratoire de Physique Nucleaire et de Hautes Energies, Universites Paris VI and VII, Paris, France b Centre a Lawrence ABSTRACT The Nearby Supernova Factory (SNfactory) is an international experiment designed to lay the foundation for the next generation of cosmology experiments (such as CFHTLS, wP, SNAP and LSST) which will measure the expansion history of the Universe using Type Ia supernovae. The SNfactory will discover and obtain frequent lightcurve spectrophotome- try covering 3200-10000 A for roughly 300 Type Ia supernovae at the low-redshift end of the smooth Hubble flow. The quantity, quality, breadth of galactic environments, and homogeneous nature of the SNfactory dataset will make it the premier source of calibration for the Type Ia supernova width-brightness relation and the intrinsic supernova colors used for K-correction and correction for extinction by host-galaxy dust. This dataset will also allow an extensive investiga- tion of additional parameters which possibly influence the quality of Type Ia supernovae as cosmological probes. The SNfactory search capabilities and follow-up instrumentation include wide-field CCD imagers on two 1.2-m telescopes (via collaboration with the Near Earth Asteroid Tracking team at JPL and the QUEST team at Yale), and a two-channel integral-field-unit optical spectrograph/imager being fabricated for the University of Hawaii 2.2-m telescope. In addition to ground-based follow-up, UV spectra for a subsample of these supernovae will be obtained with HST. The pipeline to obtain, transfer via wireless and standard internet, and automatically process the search images is in operation. Software and hardware development is now underway to enable the execution of follow-up spectroscopy of supernova candidates at the Hawaii 2.2-m telescope via automated remote control of the telescope and the IFU spectrograph/imager. Keywords: supernova, survey, cosmology, integral-field-unit, spectrograph 1. PROBING DARK ENERGY WITH SUPERNOVAE A coherent view of the universe is emerging in which a mysterious form of “dark energy” accounts for about 2/3 of the total energy density in the Universe. Direct evidence for this radical conclusion comes from distance measurements of Type Ia supernovae (SNe Ia; see Fig. 1) which indicate the expansion of the Universe is not slowing down as would be expected in a Universe filled with only matter and radiation. 1, 2 Further support for this result has come from recent measurements of the CMB indicating a flat universe, 3 combined with determinations of Ω M ∼ 0.3 from structure formation. SNe Ia remain the most mature cosmological distance indicator, and therefore, offer the best current means of exper- imentally probing the properties of the dark energy. Their cosmological use was developed in the early 1990’s, paving the way for the discovery of dark energy. 1, 4–10 Now similar developmental efforts are needed so that the next order of magnitude improvement of the experimental constraints on the properties of dark energy can be made. Progress must be made on two fronts, at a level which cannot be pursued with existing programs alone. First a large number of nearby SNe must be observed in an appropriate fashion since they provide the fulcrum of the lever-arm needed to make cosmological inferences from high-redshift SNe observations. Furthermore, these SNe provide the critical Correspondence: e-mail galdering@lbl.gov; telephone 510-495-2203
309 citations
Instituto Superior Técnico1, Durham University2, California Institute of Technology3, University of Cambridge4, Lawrence Berkeley National Laboratory5, Space Telescope Science Institute6, University of California, Berkeley7, Stockholm University8, University of Oxford9, Massachusetts Institute of Technology10, European Southern Observatory11, University of Barcelona12, Yale University13, University of Texas at Austin14
TL;DR: In this article, a measurement of the rate of distant Type Ia supernovae derived using 4 large subsets of data from the Supernova Cosmology Project is presented. But the authors do not consider the impact of the assumed cosmological parameters on the observed supernova rate.
Abstract: We present a measurement of the rate of distant Type Ia supernovae derived using 4 large subsets of data from the Supernova Cosmology Project. Within this fiducial sample,which surveyed about 12 square degrees, thirty-eight supernovae were detected at redshifts 0.25--0.85. In a spatially flat cosmological model consistent with the results obtained by the Supernova Cosmology Project, we derive a rest-frame Type Ia supernova rate at a mean red shift z {approx_equal} 0.55 of 1.53 {sub -0.25}{sub -0.31}{sup 0.28}{sup 0.32} x 10{sup -4} h{sup 3} Mpc{sup -3} yr{sup -1} or 0.58{sub -0.09}{sub -0.09}{sup +0.10}{sup +0.10} h{sup 2} SNu(1 SNu = 1 supernova per century per 10{sup 10} L{sub B}sun), where the first uncertainty is statistical and the second includes systematic effects. The dependence of the rate on the assumed cosmological parameters is studied and the redshift dependence of the rate per unit comoving volume is contrasted with local estimates in the context of possible cosmic star formation histories and progenitor models.
106 citations
TL;DR: In this article, the rate of distant Type Ia supernovae derived using 4 large subsets of data from the Supernova Cosmology Project was derived using a spatially-flat cosmological model.
Abstract: We present a measurement of the rate of distant Type Ia supernovae derived using 4 large subsets of data from the Supernova Cosmology Project. Within this fiducial sample, which surveyed about 12 square degrees, thirty-eight supernovae were detected at redshifts 0.25--0.85. In a spatially-flat cosmological model consistent with the results obtained by the Supernova Cosmology Project, we derive a rest-frame Type Ia supernova rate at a mean redshift $z\simeq0.55$ of $1.53 {^{+0.28}_{-0.25}} {^{+0.32}_{-0.31}} 10^{-4} h^3 {\rm Mpc}^{-3} {\rm yr}^{-1}$ or $0.58 {^{+0.10}_{-0.09}} {^{+0.10}_{-0.09}} h^2 {\rm SNu}$ (1 SNu = 1 supernova per century per $10^{10}$\Lbsun), where the first uncertainty is statistical and the second includes systematic effects. The dependence of the rate on the assumed cosmological parameters is studied and the redshift dependence of the rate per unit comoving volume is contrasted with local estimates in the context of possible cosmic star formation histories and progenitor models.
101 citations
University of Michigan1, Carnegie Institution for Science2, Lawrence Berkeley National Laboratory3, University of Washington4, Université Paris-Saclay5, Pontifical Catholic University of Chile6, University of California, Berkeley7, University of Arizona8, Stockholm University9, University of California, Santa Cruz10, University of Oxford11, University of Barcelona12, University of Concepción13, Harvard University14
TL;DR: In this paper, the authors presented the BVRI and JsHKs light curves of SN 1999aw (through ~100 days past maximum light), as well as several epochs of optical spectra.
Abstract: SN 1999aw was discovered during the first campaign of the Nearby Galaxies Supernova Search project. This luminous, slow-declining [Δm15(B) = 0.81 ± 0.03] Type Ia supernova was noteworthy in at least two respects. First, it occurred in an extremely low luminosity host galaxy that was not visible in the template images nor in initial subsequent deep imaging. Second, the photometric and spectral properties of this supernova indicate that it very likely was similar to the subclass of Type Ia supernovae whose prototype is SN 1999aa. This paper presents the BVRI and JsHKs light curves of SN 1999aw (through ~100 days past maximum light), as well as several epochs of optical spectra. From these data, we calculate the bolometric light curve and give estimates of the luminosity at maximum light and the initial 56Ni mass. In addition, we present deep BVI images obtained recently with the Baade 6.5 m telescope at Las Campanas Observatory that reveal the remarkably low-luminosity host galaxy.
92 citations
TL;DR: In this paper, the authors presented the BVRI and J{s} HK-s} lightcurves of SN 1999aw (through 100 days past maximum light), as well as several epochs of optical spectra.
Abstract: SN 1999aw was discovered during the first campaign of the Nearby Galaxies Supernova Search (NGSS) project. This luminous, slow-declining (Delta m_{15} (B) = 0.81 \pm 0.03) Type Ia supernova was noteworthy in at least two respects. First, it occurred in an extremely low luminosity host galaxy that was not visible in the template images, nor in initial subsequent deep imaging. Secondly, the photometric and spectral properties of this supernova indicate that it very likely was similar to the subclass of Type Ia supernovae whose prototype is SN 1999aa. This paper presents the BVRI and J_{s} HK_{s} lightcurves of SN 1999aw (through 100 days past maximum light), as well as several epochs of optical spectra. From these data we calculate the bolometric light curve, and give estimates of the luminosity at maximum light and the initial ^{56}Ni mass. In addition, we present deep BVI images obtained recently with the Baade 6.5-meter telescope at Las Campanas Observatory which reveal the remarkably low-luminosity host galaxy.
79 citations
Lawrence Berkeley National Laboratory1, University of Michigan2, Stockholm University3, Centre national de la recherche scientifique4, University of Pennsylvania5, University of California, Berkeley6, Indiana University7, American Astronomical Society8, California Institute of Technology9, Space Telescope Science Institute10, Case Western Reserve University11, University of Cambridge12, Goddard Space Flight Center13
TL;DR: The SuperNova / Acceleration Probe (SNAP) as mentioned in this paper is a space-based experiment to measure the expansion history of the universe and study both its dark energy and the dark matter.
Abstract: G. Aldering a , C. Akerlof b , R. Amanullah c , P. Astier d , E. Barrelet d , C. Bebek a , L. Bergstr¨ m c , o J. Bercovitz a , G. Bernstein e , M. Bester f , A. Bonissent g , C. Bower h , W. Carithers a , E. Commins f , C. Day a , S. Deustua i , R. DiGennaro a , A. Ealet g , R. Ellis j , M. Eriksson c , A. Fruchter k , J-F. Genat d , G. Goldhaber f , A. Goobar c , D. Groom a , S. Harris f , P. Harvey f , H. Heetderks f , S. Holland a , D. Huterer l , A. Karcher a , A. Kim a , W. Kolbe a , B. Krieger a , R. Lafever a , J. Lamoureux a , M. Lampton f , M. Levi a , D. Levin b , E. Linder a , S. Loken a , o R. Malina m , R. Massey n , T. McKay b , S. McKee b , R. Miquel a , E. M¨ rtsell c , N. Mostek h , h , J. Musser h , P. Nugent a , H. Oluseyi a , R. Pain d , N. Palaio a , D. Pankow f , S. Mufson S. Perlmutter a , R. Pratt f , E. Prieto m , A. Refregier n , J. Rhodes o , K. Robinson a , N. Roe a , M. Sholl f , M. Schubnell b , G. Smadja p , G. Smoot f , A. Spadafora a , G. Tarle b , A. Tomasch b , H. von der Lippe a , D. Vincent, d J. Walder a , and G. Wang a a Lawrence Berkeley National Laboratory, Berkeley CA, USA of Michigan, Ann Arbor MI, USA c University of Stockholm, Stockholm, Sweden d CNRS/IN2P3/LPNHE, Paris, France e University of Pennsylvania, Philadelphia PA, USA f University of California, Berkeley CA, USA g CNRS/IN2P3/CPPM, Marseille, France h Indiana University, Bloomington IN, USA i American Astronomical Society, Washington DC, USA j California Institute of Technology, Pasedena CA, USA k Space Telescope Science Institute, Baltimore MD, USA l Case Western Reserve University, Cleveland OH, USA m CNRS/INSU/LAM, Marseille, France n Cambridge University, Cambridge, UK o Goddard Space Flight Center, Greenbelt MD, USA p CNRS/IN2P3/IPNL, Lyon, France b University ABSTRACT The SuperNova / Acceleration Probe (SNAP) is a space-based experiment to measure the expansion history of the Uni- verse and study both its dark energy and the dark matter. The experiment is motivated by the startling discovery that the expansion of the Universe is accelerating. A 0.7 square-degree imager comprised of 36 large format fully-depleted O -type CCD’s sharing a focal plane with 36 HgCdTe detectors forms the heart of SNAP, allowing discovery and lightcurve measurements simultaneously for many supernovae. The imager and a high-efficiency low-resolution integral field spec- trograph are coupled to a 2-m three mirror anastigmat wide-field telescope, which will be placed in a high-earth orbit. The SNAP mission can obtain high-signal-to-noise calibrated light-curves and spectra for over 2000 Type Ia supernovae ¼ ½ and 1.7. The resulting data set can not only determine the amount of dark energy with at redshifts between Þ high precision, but test the nature of the dark energy by examining its equation of state. In particular, dark energy due to a cosmological constant can be differentiated from alternatives such as “quintessence”, by measuring the dark energy’s equation of state to an accuracy of ¦¼ ¼ , and by studying its time dependence. Keywords: Early universe—instrumentation: detectors—space vehicles: instruments—supernovae:general—telescopes Correspondence: e-mail galdering@lbl.gov; telephone 510-495-2203
75 citations
TL;DR: In this article, the authors used a hydrodynamical model to model the observed spectra from day 1 to day 81 of supernova 1987A and showed that good agreement can be obtained at times up to about 60 days, if they allow for extended nickel mixing.
Abstract: Supernova 1987A remains the most well-studied supernova to date. Observations produced excellent broad-band photometric and spectroscopic coverage over a wide wavelength range at all epochs. We model the observed spectra from Day 1 to Day 81 using a hydrodynamical model. We show that good agreement can be obtained at times up to about 60 days, if we allow for extended nickel mixing. Later than about 60 days the observed Balmer lines become stronger than our models can reproduce. We show that this is likely due to a more complicated distribution of gamma-rays than we allow for in our spherically symmetric calculations. We present synthetic light curves in UBVRIJHK and a synthetic bolometric light curve. Using this broad baseline of detailed spectroscopic models we find a distance modulus mu = 18.5 +/- 0.2 using the SEAM method of determining distances to supernovae. We find that the explosion time agrees with that of the neutrino burst and is constrained at 68 percent confidence to within +/- 0.9 days. We argue that the weak Balmer lines of our detailed model calculations casts doubt on the accuracy of the purely photometric EPM method. We also suggest that Type IIP supernovae will be most useful as distance indicators at early times due to a variety of effects.
57 citations
TL;DR: In this paper, the effects of lensing by those objects on the magnitude of SN 1997ff were investigated, and it was shown that due to the spatial configuration of the foreground galaxies, the shear from individual lenses partially cancels out, and total distortion induced on the host galaxy is considerably smaller than that produced by a single lens having the same magnification.
Abstract: With a redshift of z {approx} 1.7, SN 1997ff is the most distant type Ia supernova discovered so far. This SN is close to several bright, z = 0.6-0.9 galaxies, and we consider the effects of lensing by those objects on the magnitude of SN 1997ff. We estimate their velocity dispersions using the Tully-Fisher and Faber-Jackson relations corrected for evolution effects, and calculate, applying the multiple-plane lensing formalism, that SN 1997ff is magnified by 0.34{+-}0.12 mag. Due to the spatial configuration of the foreground galaxies, the shear from individual lenses partially cancels out,and the total distortion induced on the host galaxy is considerably smaller than that produced by a single lens having the same magnification. After correction for lensing, the revised distance to SN 1997ff is m-M = 45.49 {+-} 0.34 mag, which improves the agreement with the {Omega}{sub M} = 0.35, {Omega}{Lambda} = 0.65 cosmology expected from lower-redshift SNe Ia, and is inconsistent at the {approx} 3 sigma confidence level with a uniform gray dust model or a simple evolution model.
53 citations
TL;DR: In this article, the authors investigate the possibility of measuring the Hubble constant, the fractional energy density components and the equation of state parameter of the "dark energy" using lensed multiple images of high-redshift supernovae.
Abstract: We investigate the possibility of measuring the Hubble constant, the fractional energy density components and the equation of state parameter of the "dark energy" using lensed multiple images of high-redshift supernovae. With future instruments, such as the SNAP and NGST satellites, it will become possible to observe several hundred lensed core-collapse supernovae with multiple images. Accurate measurements of the image separation, flux-ratio, time-delay and lensing foreground galaxy will provide complementary information to the cosmological tests based on, e.g., the magnitude-redshift relation of type Ia supernovae, especially with regards to the Hubble parameter that could be measured with a statistical uncertainty at the one percent level. Assuming a flat universe, the statistical uncertainty on the mass density is found to be stat M < 0:05. However, systematic eects from the uncertainty of the lens modeling are likely to dominate. E.g., if the lensing galaxies are extremely compact but are (erroneously) modeled as singular isothermal spheres, the mass density is biased by syst M 0:1. We argue that wide-field near-IR instruments such as the one proposed for the SNAP mission are critical for collecting large statistics of lensed supernovae.
53 citations
TL;DR: In this article, the authors used a hydrodynamical model to model the observed spectra from day 1 to day 81 using a broad baseline of detailed spectroscopic models and found a distance modulus mu = 18.5 +/- 0.2 using the SEAM method of determining distances to supernovae.
Abstract: Supernova 1987A remains the most well-studied supernova to date. Observations produced excellent broad-band photometric and spectroscopic coverage over a wide wavelength range at all epochs. We model the observed spectra from Day 1 to Day 81 using a hydrodynamical model. We show that good agreement can be obtained at times up to about 60 days, if we allow for extended nickel mixing. Later than about 60 days the observed Balmer lines become stronger than our models can reproduce. We show that this is likely due to a more complicated distribution of gamma-rays than we allow for in our spherically symmetric calculations. We present synthetic light curves in UBVRIJHK and a synthetic bolometric light curve. Using this broad baseline of detailed spectroscopic models we find a distance modulus mu = 18.5 +/- 0.2 using the SEAM method of determining distances to supernovae. We find that the explosion time agrees with that of the neutrino burst and is constrained at 68% confidence to within +/- 0.9 days. We argue that the weak Balmer lines of our detailed model calculations casts doubt on the accuracy of the purely photometric EPM method. We also suggest that Type IIP supernovae will be most useful as distance indicators at early times due to a variety of effects.
Lawrence Berkeley National Laboratory1, University of Michigan2, Stockholm University3, Centre national de la recherche scientifique4, University of Pennsylvania5, University of California, Berkeley6, Indiana University7, American Astronomical Society8, California Institute of Technology9, Space Telescope Science Institute10, Case Western Reserve University11, University of Cambridge12, Goddard Space Flight Center13
TL;DR: The Supernova / Acceleration Probe (SNAP) is a proposed space-borne observatory that will survey the sky with a wide-field optical/near-infrared (NIR) imager.
Abstract: The Supernova / Acceleration Probe (SNAP) is a proposed space-borne observatory that will survey the sky with a wide-field optical/near-infrared (NIR) imager. The images produced by SNAP will have an unprecedented combination of depth, solid-angle, angular resolution, and temporal sampling. For 16 months each, two 7.5 square-degree fields will be observed every four days to a magnitude depth of AB=27.7 in each of the SNAP filters, spanning 3500-17000a. Co-adding images over all epochs will give AB=30.3 per filter. In addition, a 300 square-degree field will be surveyed to AB=28 per filter, with no repeated temporal sampling. Although the survey strategy is tailored for supernova and weak gravitational lensing observations, the resulting data will support a broad range of auxiliary science programs.
Journal Article•
TL;DR: The SuperNova/Acceleration Probe (SNAP) as discussed by the authors was the first NIR system to detect Type Ia supernovae between z = 1 and 1.7.
Abstract: The SuperNova/Acceleration Probe (SNAP) will measure precisely the cosmological expansion history over both the acceleration and deceleration epochs and thereby constrain the nature of the dark energy that dominates our universe today. The SNAP focal plane contains equal areas of optical CCDs and NIR sensors and an integral field spectrograph. Having over 150 million pixels and a field-of-view of 0.34 square degrees, the SNAP NIR system will be the largest yet constructed. With sensitivity in the range 0.9-1.7 {micro}m, it will detect Type Ia supernovae between z = 1 and 1.7 and will provide follow-up precision photometry for all supernovae. HgCdTe technology, with a cut-off tuned to 1.7 {micro}m, will permit passive cooling at 140 K while maintaining noise below zodiacal levels. By dithering to remove the effects of intrapixel variations and by careful attention to other instrumental effects, we expect to control relative photometric accuracy below a few hundredths of a magnitude. Because SNAP continuously revisits the same fields we will be able to achieve outstanding statistical precision on the photometry of reference stars in these fields, allowing precise monitoring of our detectors. The capabilities of the NIR system for broadening the science reach of SNAP are discussed.
TL;DR: In this article, a progress report on a collaborative program at the Las Campanas and Cerro Tololo Observatories to observe the near-IR light curves of Type Ia supernovae is provided.
Abstract: This paper provides a progress report on a collaborative program at the Las Campanas and Cerro Tololo Observatories to observe the near-IR light curves of Type Ia supernovae. We discuss how the morphologies of the JHK light curves change as a function of the decline rate. Evidence is presented which indicates that the absolute magnitudes in the H band have little or no dependence on the decline rate, suggesting that SNe Ia may be nearly perfect cosmological standard candles in the near-IR. A preliminary Hubble diagram in the H band is presented and compared with a similar diagram in V for the same objects. Finally, observations of two peculiar supernovae, 1999ac and 2001ay, are briefly discussed.
TL;DR: In this article, the authors investigate the possibility of measuring the Hubble constant, the fractional energy density components and the equation of state parameter of the ''dark energy'' using lensed multiple images of high-redshift supernovae.
Abstract: We investigate the possibility of measuring the Hubble constant, the fractional energy density components and the equation of state parameter of the ``dark energy'' using lensed multiple images of high-redshift supernovae. With future instruments, such as the SNAP and NGST satellites, it will become possible to observe several hundred lensed core-collapse supernovae with multiple images. Accurate measurements of the image separation, flux-ratio, time-delay and lensing foreground galaxy will provide complementary information to the cosmological tests based on, e.g., the magnitude-redshift relation of Type Ia supernovae, especially with regards to the Hubble parameter that could be measured with a statistical uncertainty at the one percent level. Assuming a flat universe, the statistical uncertainty on the mass density is found to be sigma^stat_m <0.05. However, systematic effects from the uncertainty of the lens modeling are likely to dominate. E.g., if the lensing galaxies are extremely compact but are (erroneously) modeled as singular isothermal spheres, the mass density is biased by sigma^syst_m =0.1.
We argue that wide-field near-IR instruments such as the one proposed for the SNAP mission are critical for collecting large statistics of lensed supernovae.
Durham University1, California Institute of Technology2, Lawrence Berkeley National Laboratory3, Stockholm University4, Pierre-and-Marie-Curie University5, Colorado College6, University of California, Berkeley7, American Astronomical Society8, University of Tokyo9, Space Telescope Science Institute10, University of Oxford11, University of Cambridge12, Vanderbilt University13, European Southern Observatory14, University of Barcelona15, University of Texas at Austin16
TL;DR: In this article, the authors show that the scatter in the SNe Ia Hubble diagram is smallest for SNe occurring in early-type hosts and largest for those occurring in late-type galaxies.
Abstract: (Abridged) We present new results on the Hubble diagram of distant type Ia supernovae (SNe Ia) segregated according to the type of host galaxy. This makes it possible to check earlier evidence for a cosmological constant by explicitly comparing SNe residing in galaxies likely to contain negligible dust with the larger sample. The cosmological parameters derived from these SNe Ia hosted by presumed dust-free early-type galaxies supports earlier claims for a cosmological constant, which we demonstrate at 5 sigma significance, and the internal extinction implied is small even for late-type systems (A_B<0.2). Thus, our data demonstrate that host galaxy extinction is unlikely to systematically dim distant SNe Ia in a manner that would produce a spurious cosmological constant. We classify the host galaxies of 39 distant SNe discovered by the Supernova Cosmology Project (SCP) using the combination of HST STIS imaging, Keck ESI spectroscopy and ground-based broad-band photometry. We compare with a low-redshift sample of 25 SNe Ia. The scatter observed in the SNe Ia Hubble diagrams correlates closely with host galaxy morphology. We find the scatter in the SNe Ia Hubble diagram is smallest for SNe occurring in early-type hosts and largest for those occurring in late-type galaxies. Moreover, SNe residing in early-type hosts appear only ~0.14+/-0.09 mag brighter in their light-curve-width-corrected luminosity than those in late-type hosts, implying only a modest amount of dust extinction even in the late-type systems.
TL;DR: In this paper, the effects of lensing by those objects on the magnitude of SN 1997ff were investigated and the authors estimated their velocity dispersions using the Tully-Fisher and Faber-Jackson relations corrected for evolution effects, and calculated, applying the multiple-plane lensing formalism, that SN1997ff is magnified by 0.34+-0.12 mag.
Abstract: With a redshift of z~1.7, SN 1997ff is the most distant type Ia supernova discovered so far. This SN is close to several bright, z=0.6-0.9 galaxies, and we consider the effects of lensing by those objects on the magnitude of SN 1997ff. We estimate their velocity dispersions using the Tully-Fisher and Faber-Jackson relations corrected for evolution effects,and calculate, applying the multiple-plane lensing formalism, that SN 1997ff is magnified by 0.34+-0.12 mag. Due to the spatial configuration of the foreground galaxies, the shear from individual lenses partially cancels out,and the total distortion induced on the host galaxy is considerable smaller than that produced by a single lens having the same magnification. After correction for lensing, the revised distance to SN 1997ff is m-M=45.5 mag, which improves the agreement with the Omega_M=0.35, Omega_Lambda = 0.65 cosmology expected from lower-redshift SNe Ia, and is inconsistent at the ~3 sigma confidence level with a uniform gray dust model or a simple evolution model.