Russet Jennifer McMillan

The Sloan Digital Sky Survey - II:supernova survey: technical summary

The Sloan Digital Sky Survey-II (SDSS-II) has embarked on a multi-year project to identify and measure light curves for intermediate-redshift (0.05 < z < 0.35) Type Ia supernovae (SNe Ia) using repeated five-band (ugriz) imaging over an area of 300 sq. deg. The survey region is a stripe 2.5° wide centered on the celestial equator in the Southern Galactic Cap that has been imaged numerous times in earlier years, enabling construction of a deep reference image for the discovery of new objects. Supernova imaging observations are being acquired between September 1 and November 30 of 2005-7. During the first two seasons, each region was imaged on average every five nights. Spectroscopic follow-up observations to determine supernova type and redshift are carried out on a large number of telescopes. In its first two three-month seasons, the survey has discovered and measured light curves for 327 spectroscopically confirmed SNe Ia, 30 probable SNe Ia, 14 confirmed SNe Ib/c, 32 confirmed SNe II, plus a large number of photometrically identified SNe Ia, 94 of which have host-galaxy spectra taken so far. This paper provides an overview of the project and briefly describes the observations completed during the first two seasons of operation.

The Sloan Digital Sky Survey-II Supernova Survey: Search Algorithm and Follow-up Observations

The Sloan Digital Sky Survey-II Supernova Survey has identified a large number of new transient sources in a 300 deg2 region along the celestial equator during its first two seasons of a three-season campaign. Multi-band (ugriz) light curves were measured for most of the sources, which include solar system objects, galactic variable stars, active galactic nuclei, supernovae (SNe), and other astronomical transients. The imaging survey is augmented by an extensive spectroscopic follow-up program to identify SNe, measure their redshifts, and study the physical conditions of the explosions and their environment through spectroscopic diagnostics. During the survey, light curves are rapidly evaluated to provide an initial photometric type of the SNe, and a selected sample of sources are targeted for spectroscopic observations. In the first two seasons, 476 sources were selected for spectroscopic observations, of which 403 were identified as SNe. For the type Ia SNe, the main driver for the survey, our photometric typing and targeting efficiency is 90%. Only 6% of the photometric SN Ia candidates were spectroscopically classified as non-SN Ia instead, and the remaining 4% resulted in low signal-to-noise, unclassified spectra. This paper describes the search algorithm and the software, and the real-time processing of the SDSS imaging data. We also present the details of the supernova candidate selection procedures and strategies for follow-up spectroscopic and imaging observations of the discovered sources.

Uniformity of (V?Near-Infrared) Color Evolution of Type Ia Supernovae and Implications for Host Galaxy Extinction Determination

From an analysis of SNe 1972E, 1980N, 1981B, 1981D, 1983R, 1998bu, 1999cl, and 1999cp, we find that the intrinsic V-K colors of Type Ia SNe of typical luminosity (i.e., with multicolor light-curve shape (MLCS) parameter -0.4 ? +0.2 mag) suggest a uniform color curve. V-K colors become bluer linearly with time from roughly one week before B-band maximum until one week after maximum, after which they redden linearly until four weeks after maximum. V-H colors exhibit very similar color evolution. V-J colors exhibit slightly more complex evolution, with greater scatter. The existence of V-near-infrared (NIR) color relations allows the construction of near-infrared light-curve templates that are an improvement on those of Elias et al. from 1985. We provide optical BVRI and infrared JHK photometry of the Type Ia supernovae 1999aa, 1999cl, and 1999cp. SN 1999aa is an overluminous slow decliner (with ? = -0.47 mag). SN 1999cp is a moderately bright SN unreddened in its host. SN 1999cl is extremely reddened in its host. The V-NIR colors of SN 1999cl yield AV = 2.01 ? 0.11 mag. This leads to a distance for its host galaxy (M88) in agreement with other distance measurements for members of the Virgo Cluster.

A Measurement of the Rate of Type Ia Supernovae at Redshift z ≈ 0.1 from the First Season of the SDSS-II Supernova Survey

We present a measurement of the rate of Type Ia supernovae (SNe Ia) from the first of three seasons of data from the SDSS-II Supernova Survey. For this measurement, we include 17 SNe Ia at redshift z ≤ 0.12. Assuming a flat cosmology with Ωm = 0.3 = 1 − ΩΛ, we find a volumetric SN Ia rate of [ 2.93+ 0.17−0.04(systematic)+ 0.90−0.71(statistical) ] × 10−5 SNe Mpc −3 h370 yr −1, at a volume-weighted mean redshift of 0.09. This result is consistent with previous measurements of the SN Ia rate in a similar redshift range. The systematic errors are well controlled, resulting in the most precise measurement of the SN Ia rate in this redshift range. We use a maximum likelihood method to fit SN rate models to the SDSS-II Supernova Survey data in combination with other rate measurements, thereby constraining models for the redshift evolution of the SN Ia rate. Fitting the combined data to a simple power-law evolution of the volumetric SN Ia rate, rV ∝ (1 + z)β, we obtain a value of β = 1.5 ± 0.6, i.e., the SN Ia rate is determined to be an increasing function of redshift at the ~2.5 σ level. Fitting the results to a model in which the volumetric SN rate is rV = Aρ(t) + B(t), where ρ (t) is the stellar mass density and (t) is the star formation rate, we find A = (2.8 ± 1.2) × 10−14 SNe M−1☉ yr −1, B = (9.3+ 3.4−3.1) × 10−4 SNe M−1☉.

Photometry of the Type Ia Supernovae 1999cc, 1999cl, and 2000cf*

We present previously unpublished BVRI photometry of the Type Ia supernovae 1999cc and 2000cf along with revised photometry of SN 1999cl. We confirm that SN 1999cl is reddened by highly nonstandard dust, with RV = 1.55 ? 0.08. Excepting two quasar-lensing galaxies whose low values of RV are controversial, this is the only known object with a published value of RV less than 2.0. SNe 1999cl and 2000cf have near-infrared absolute magnitudes at maximum in good agreement with other Type Ia supernovae of midrange decline rates.

Optical and Infrared Photometry of the Unusual Type Ia Supernova 2000cx

ABSTRACT We present optical and infrared photometry of the unusual Type Ia supernova 2000cx. With the data of Li et al. and Jha, this constitutes the largest data set ever assembled for a Type Ia SN, more than 600 points in UBVRIJHK. We confirm the finding of Li et al. regarding the unusually blue B−V colors as SN 2000cx entered the nebular phase. Its I‐band secondary hump was extremely weak given its B‐band decline rate. The V minus near‐infrared colors likewise do not match loci based on other slowly declining Type Ia SNe, although V−K is the least “abnormal.” In several ways, SN 2000cx resembles other slow decliners, given its B‐band decline rate [ \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \ren...

First-year spectroscopy for the sloan digital sky survey - II. Supernova survey

This paper presents spectroscopy of supernovae (SNe) discovered in the first season of the Sloan Digital Sky Survey-II SN Survey. This program searches for and measures multi-band light curves of SNe in the redshift range z = 0.05-0.4, complementing existing surveys at lower and higher redshifts. Our goal is to better characterize the SN population, with a particular focus on SNe Ia, improving their utility as cosmological distance indicators and as probes of dark energy. Our SN spectroscopy program features rapid-response observations using telescopes of a range of apertures, and provides confirmation of the SN and host-galaxy types as well as precise redshifts. We describe here the target identification and prioritization, data reduction, redshift measurement, and classification of 129 SNe Ia, 16 spectroscopically probable SNe Ia, 7 SNe Ib/c, and 11 SNe II from the first season. We also describe our efforts to measure and remove the substantial host-galaxy contamination existing in the majority of our SN spectra.

Long-term degradation of optical devices on the Moon

Forty years ago, Apollo astronauts placed the first of several retroreflector arrays on the lunar surface. Their continued usefulness for laser ranging might suggest that the lunar environment does not damage optical devices. However, new laser ranging data reveal that the efficiency of the three Apollo reflector arrays is now diminished by a factor of 10 at all lunar phases and by an additional factor of 10 when the lunar phase is near full Moon. These deficits did not exist in the earliest years of lunar ranging, indicating that the lunar environment damages optical equipment on the timescale of decades. Dust or abrasion on the front faces of the corner-cube prisms may be responsible, reducing their reflectivity and degrading their thermal performance when exposed to face-on sunlight at full Moon. These mechanisms can be tested using laboratory simulations and must be understood before designing equipment destined for the Moon.

Planetary Nebulae as Standard Candles. IX. The Distance to the Fornax Cluster

We present the results of a planetary nebula (PN) survey of three galaxies in the Fornax Cluster performed with the Cerro Tololo 4 m telescope and on-band off-band [O III] λ5007 interference filters. In all, we detected 224 PN candidates: 105 in the peculiar S0/Sa galaxy NGC 1316 (Fornax A), 47 in the E2 galaxy NGC 1404, and 72 in the central cD of the cluster NGC 1399. Using statistically complete samples of planetaries and the procedures described in previous papers in the series, we derive distances to these galaxies from the planetary nebula luminosity function (PNLF). Our distance moduli of 31.13, 31.17,and 31.15 to NGC 1316, 1399, and 1404 show that the cluster is tightly clumped, as suggested by Tonry (1991)

A Time Delay for the Cluster-lensed Quasar SDSS J1004+4112

We present 426 epochs of optical monitoring data spanning 1000 days from 2003 December to 2006 June for the gravitationally lensed quasar SDSS J1004+4112. The time delay between the A and B images is ΔtBA = 38:4 ± 2:0 days (Δχ^2 = 4) in the expected sense that B leads A and the overall time ordering is C-B-A-D-E. The measured delay invalidates all published models. The models probably failed because they neglected the perturbations from cluster member galaxies. Models including the galaxies can fit the data well, but conclusions about the cluster mass distribution should await the measurement of the longer, and less substructure sensitive, delays of the C and D images. For these images, a delay of ΔtCB ≃ 681 ± 15 days is plausible but requires confirmation, while delays of ΔtCB > 560 days and ΔtAD > 800 days are required. We clearly detect microlensing of the A/B images, with the delay-corrected flux ratios changing from mB - mA = 0:44 ± 0:01 mag in the first season to 0:29 ± 0:01 mag in the second season and 0:32 ± 0:01 mag in the third season.