We present Advanced Camera for Surveys, NICMOS, and Keck adaptive-optics-assisted photometry of 20 Type Ia supernovae (SNe Ia) from the Hubble Space Telescope (HST) Cluster Supernova Survey. The SNe Ia were discovered over the redshift interval 0.623 1 SNe Ia. We describe how such a sample could be efficiently obtained by targeting cluster fields with WFC3 on board HST. The updated supernova Union2.1 compilation of 580 SNe is available at http://supernova.lbl.gov/Union.

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The Hubble Space Telescope Cluster Supernova Survey. V. Improving the Dark-energy Constraints above z > 1 and Building an Early-type-hosted Supernova Sample

The High-z Supernova Search Team has discovered and observed eight new supernovae in the redshift interval z = 0.3-1.2. These independent observations, analyzed by similar but distinct methods, confirm the results of Riess and Perlmutter and coworkers that supernova luminosity distances imply an accelerating universe. More importantly, they extend the redshift range of consistently observed Type Ia supernovae (SNe Ia) to z ≈ 1, where the signature of cosmological effects has the opposite sign of some plausible systematic effects. Consequently, these measurements not only provide another quantitative confirmation of the importance of dark energy, but also constitute a powerful qualitative test for the cosmological origin of cosmic acceleration. We find a rate for SN Ia of (1.4 ± 0.5) × 10-4 h3 Mpc-3 yr-1 at a mean redshift of 0.5. We present distances and host extinctions for 230 SN Ia. These place the following constraints on cosmological quantities: if the equation of state parameter of the dark energy is w = -1, then H0t0 = 0.96 ± 0.04, and ΩΛ - 1.4ΩM = 0.35 ± 0.14. Including the constraint of a flat universe, we find ΩM = 0.28 ± 0.05, independent of any large-scale structure measurements. Adopting a prior based on the Two Degree Field (2dF) Redshift Survey constraint on ΩM and assuming a flat universe, we find that the equation of state parameter of the dark energy lies in the range -1.48 -1, we obtain w < -0.73 at 95% confidence. These constraints are similar in precision and in value to recent results reported using the WMAP satellite, also in combination with the 2dF Redshift Survey.

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Cosmological Results from High-z Supernovae* **

We present an empirical model of Type Ia supernovae spectro-photometric evolution with time. The model is built using a large data set including light-curves and spectra of both nearby and distant supernovae, the latter being observed by the SNLS collaboration. We derive the average spectral sequence of Type Ia supernovae and their main variability components including a color variation law. The model allows us to measure distance moduli in the spectral range 2500-8000 A with calculable uncertainties, including those arising from variability of spectral features. Thanks to the use of high-redshift SNe to model the rest-frame UV spectral energy distribution, we are able to derive improved distance estimates for SNe Ia in the redshift range 0.8

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SALT2: using distant supernovae to improve the use of type Ia supernovae as distance indicators

We have built a reliable and robust system that takes as input an astronomical image, and returns as output the pointing, scale, and orientation of that image (the astrometric calibration or World Coordinate System information). The system requires no first guess, and works with the information in the image pixels alone; that is, the problem is a generalization of the "lost in space" problem in which nothing—not even the image scale—is known. After robust source detection is performed in the input image, asterisms (sets of four or five stars) are geometrically hashed and compared to pre-indexed hashes to generate hypotheses about the astrometric calibration. A hypothesis is only accepted as true if it passes a Bayesian decision theory test against a null hypothesis. With indices built from the USNO-B catalog and designed for uniformity of coverage and redundancy, the success rate is >99.9% for contemporary near-ultraviolet and visual imaging survey data, with no false positives. The failure rate is consistent with the incompleteness of the USNO-B catalog; augmentation with indices built from the Two Micron All Sky Survey catalog brings the completeness to 100% with no false positives. We are using this system to generate consistent and standards-compliant meta-data for digital and digitized imaging from plate repositories, automated observatories, individual scientific investigators, and hobbyists. This is the first step in a program of making it possible to trust calibration meta-data for astronomical data of arbitrary provenance.

http://iopscience.iop.org/article/10.1088/0004-6256/139/5/1782/pdf

Astrometry.net: Blind Astrometric Calibration of Arbitrary Astronomical Images

Precise and accurate parameters for late-type (late K and M) dwarf stars are important for characterization of any orbiting planets, but such determinations have been hampered by these stars' compl ...

/pdf/how-to-constrain-your-m-dwarf-measuring-effective-2d8sxzh4ve.pdf

How to constrain your m dwarf: measuring effective temperature, bolometric luminosity, mass, and radius

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

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D. Andy Howell

Papers

Overview of the nearby supernova factory