The High-z Supernova Search Team has discovered and observed eight new supernovae in the redshift interval z ¼ 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 ð1:4 AE 0:5Þ Â 10 À4 h 3 Mpc À3 yr À1 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 ¼ À1, then H 0 t 0 ¼ 0:96 AE 0:04, and à À 1:4 M ¼ 0:35 AE 0:14. Including the constraint of a flat universe, we find M ¼ 0:28 AE 0:05, independent of any large-scale structure measurements. Adopting a prior based on the Two Degree Field (2dF) Redshift Survey constraint on M and assuming a flat universe, we find that the equation of state parameter of the dark energy lies in the range À1:48 < w < À0:72 at 95% confidence. If we further assume that w > À1, we obtain w < À0:73 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.

To empirically calibrate the IR surface brightness fluctuation (SBF) distance scale and probe the properties of unresolved stellar populations, we measured fluctuations in 65 galaxies using NICMOS on the Hubble Space Telescope. The early-type galaxies in this sample include elliptical and S0 galaxies and spiral bulges in a variety of environments. Absolute fluctuation magnitudes in the F160W (1.6 µm) filter (M F160W ) were derived for each galaxy using previouslymeasured I-band SBF and Cepheid variable star distances. F160W SBFs can be used to measure distances to early-type galaxies with a relative accuracy of ∼10% provided that the galaxy color is known to ∼0.035 mag or better. Near-IR fluctuations can also reveal the properties of the most luminous stellar populations in galaxies. Comparison of F160W fluctuation magnitudes and optical colors to stellar population model predictions suggests that bluer elliptical and S0 galaxies have significantly younger populations than redder ones, and may also be more metal-rich. There are no galaxies in this sample with fluctuation magnitudes consistent with old, metal-poor (t > 5 Gyr, [Fe/H] < −0.7) stellar population models. Composite stellar population models imply that bright fluctuations in the bluer galaxies may be the result of an episode of recent star formation in a fraction of the total mass of a galaxy. Age estimates from the F160W fluctuation magnitudes are consistent with those measured using the Hβ Balmer line index. The two types of measurements make use of completely different techniques and are sensitive to stars in different evolutionary phases. Both techniques reveal the presence of intermediate-age stars in the early-type galaxies of this sample.To the 1996 Virgo sample, Jensen et al. (1998) added galaxies in the Fornax and Eridanus clusters. Three of the bluest galaxies in their sample showed K-band fluctuation magnitudes that were ∼0.25 mag brighter than the others. Jensen et al. noted that the models implied younger stellar populations in these bluer ellipticals. However, the sample size was small and the range in (V −I) color was limited; hence, the slope they measured was not statistically significant and they adopted a constant K-band SBF calibration. The K-band fluctuations for the bluest galaxy in their sample (NGC 4489) were significantly brighter than the others in the Virgo cluster, but the measurement was not trusted due to its low signal-to-noise (S/N) ratio. Mei, Silva, & Quinn (2001c) subsequently re-observed this galaxy and found comparably bright K-band fluctuations.

We present photometric and spectroscopic observations of 23 high-redshift supernovae (SNe) spanning a range of z ¼ 0:34 1:03, nine of which are unambiguously classified as Type Ia. These SNe were discovered during the IfA Deep Survey, which began in 2001 September and observed a total of 2.5 deg 2 to a depth of approximately m % 25 26 in RIZ over 9-17 visits, typically every 1-3 weeks for nearly 5 months, with additional observations continuing until 2002 April. We give a brief description of the survey motivations, observational strategy, and reduction process. This sample of 23 high-redshift SNe includes 15 at z ! 0:7, doubling the published number of objects at these redshifts, and indicates that the evidence for acceleration of the universe is not due to a systematic effect proportional to redshift. In combination with the recent compilation of Tonry et al. (2003), we calculate cosmological parameter density contours that are consistent with the flat universe indicated by the cosmic microwave background (Spergel et al. 2003). Adopting the constraint that total ¼ 1:0, we obtain best-fit values of ð m ; Ã Þ ¼ ð0:33; 0:67Þ using 22 SNe from this survey augmented by the literature compilation. We show that using the empty-beam model for gravitational lensing does not eliminate the need for à > 0. Experience from this survey indicates great potential for similar large-scale surveys while also revealing the limitations of performing surveys for z > 1 SNe from the ground.

In this first paper in a series we present 1298 low-redshift (z 0.2) optical spectra of 582 Type Ia supernovae (SNe Ia) observed from 1989 through 2008 as part of the Berkeley SN Ia Program (BSNIP). 584 spectra of 199 SNe Ia have well-calibrated light curves with measured distance moduli, and many of the spectra have been corrected for host-galaxy contamination. Most of the data were obtained using the Kast double spectrograph mounted on the Shane 3 m telescope at Lick Observatory and have a typical wavelength range of 3300-10,400Å, roughly twice as wide as spectra from most previously published datasets. We present our observing and reduction procedures, and we describe the resulting SN Database (SNDB), which will be an online, public, searchable database containing all of our fully reduced spectra and companion photometry. In addition, we discuss our spectral classification scheme (using the SuperNova IDentification code, SNID; Blondin & Tonry 2007), utilising our newly constructed set of SNID spectral templates. These templates allow us to accurately classify our entire dataset, and by doing so we are able to reclassify a handful of objects as bona fide SNe Ia and a few other objects as members of some of the peculiar SN Ia subtypes. In fact, our dataset includes spectra of nearly 90 spectroscopically peculiar SNe Ia. We also present spectroscopic host-galaxy redshifts of some SNe Ia where these values were previously unknown. The sheer size of the BSNIP dataset and the consistency of our observation and reduction methods makes this sample unique among all other published SN Ia datasets and is complementary in many ways to the large, low-redshift SN Ia spectra presented by Matheson et al. 2008 andBlondin et al. 2012. In other BSNIP papers in this series, we use these data to examine the relationships between spectroscopic characteristics and various observables such as photometric and host-galaxy properties.

We derive the rates of Type Ia supernovae (SNe Ia) over a wide range of redshifts using a complete sample from the IfA Deep Survey. This sample of more than 100 SNe Ia is the largest set ever collected from a single survey and therefore uniquely powerful for a detailed supernova rate (SNR) calculation. Measurements of the SNR as a function of cosmological time offer a glimpse into the relationship between the star formation rate (SFR) and Type Ia SNR and may provide evidence for the progenitor pathway. We observe a progressively increasing Type Ia SNR between redshifts z % 0:3 and 0.8. The Type Ia SNR measurements are consistent with a short time delay (t % 1 Gyr) with respect to the SFR, indicating a fairly prompt evolution of SN Ia progenitor systems. We derive a best-fit value of SFR /SNR % 580 h À2 70 M per SN Ia for the conversion factor between the star formation and the SN Ia rates, as determined for a delay time of t % 1 Gyr between the SFR and the Type Ia SNR. More complete measurements of the Type Ia SNR at z > 1 are necessary to conclusively determine the SFR-SNR relationship and constrain SN Ia evolutionary pathways.