Christopher W. Morgan

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.

X-Ray and Optical Microlensing in the Lensed Quasar PG 1115+080

We analyzed the microlensing of the X-ray and optical emission of the lensed quasar PG 1115+080. We find that the effective radius of the X-ray emission is -->1.3+ 1.1−0.5 dex smaller than that of the optical emission. Viewed as a thin disk observed at inclination angle i, the optical accretion disk has a scale length, defined by the point where the disk temperature matches the rest-frame energy of the monitoring band ( -->kT = hc/λrest with -->λrest = 0.3 μm), of log{(rs, opt/cm)[cos(i)/0.5]½} = 16.6 ± 0.4

Further Evidence That Quasar X-Ray Emitting Regions Are Compact: X-Ray And Optical Microlensing In The Lensed Quasar Q J0158-4325

log b\{ (rs,opt/cm) [cos (i)/0.5]1/2b\} = 16.6 ± 0.4

The Rewards of Patience: An 822 Day Time Delay in the Gravitational Lens SDSS J1004+4112

-->. The X-ray emission region (1.4-21.8 keV in the rest frame) has an effective half-light radius of -->log (r1/2,X/cm) = 15.6+ 0.6−0.9. Given an estimated black hole mass of -->1.2 × 109 M☉, corresponding to a gravitational radius of -->log (rg/cm) = 14.3, the X-ray emission is generated near the inner edge of the disk, while the optical emission comes from scales slightly larger than those expected for an Eddington-limited thin disk. We find a weak trend supporting models with low stellar mass fractions near the lensed images, in mild contradiction to inferences from the stellar velocity dispersion and the time delays.

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

We present four new seasons of optical monitoring data and six epochs of X-ray photometry for the doubly imaged lensed quasar Q J0158-4325. The high-amplitude, short-period microlensing variability for which this system is known has historically precluded a time delay measurement by conventional methods. We attempt to circumvent this limitation by the application of a Monte Carlo microlensing analysis technique, but we are only able to prove that the delay must have the expected sign (image A leads image B). Despite our failure to robustly measure the time delay, we successfully model the microlensing at optical and X-ray wavelengths to find a half-light radius for soft X-ray emission log(r(1/2), (X), (soft)/cm) = 14.3(-0.5)(+0.4), an upper limit on the half-light radius for hard X-ray emission log(r(1/2), (X), (hard)/cm) <= 14.6, and a refined estimate of the inclination-corrected scale radius of the optical R-band (rest frame 3100 angstrom) continuum emission region of log(r(s)/cm) = 15.6 +/- 0.3.

COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses , VII. Time delays and the Hubble constant from WFI J2033-4723

We present 107 new epochs of optical monitoring data for the four brightest images of the gravitational lens SDSS J1004+4112 observed between 2006 October and 2007 June. Combining this data with the previously obtained light curves, we determine the time delays between images A, B, and C. We confirm our previous measurement, that B leads A by -->Δ τBA = 40.6 ± 1.8 days, and find that image C leads image A by -->Δ τCA = 821.6 ± 2.1 days. The lower limit on the remaining delay is that image D lags image A by -->Δ τAD > 1250 days. Based on the microlensing of images A and B, we estimate that the accretion disk size at a rest wavelength of 2300 A is -->1014.8 ± 0.3 cm for a disk inclination of

Microlensing of the Lensed Quasar SDSS 0924+0219*

cos i = f{1}{2}

TRANSIT TARGET SELECTION USING REDUCED PROPER MOTIONS

-->, which is consistent with the microlensing disk size-black hole mass correlation function given our estimate of the black hole mass from the Mg II line width of -->log MBH/M☉ = 8.4 ± 0.2. The long delays allow us to fill in the seasonal gaps and assemble a continuous, densely sampled light curve spanning 5.7 yr whose variability implies a structure function with a logarithmic slope of -->β = 0.52 ± 0.02. As C is the leading image, sharp features in the C light curve can be intensively studied 2.3 yr later in the A/B pair, potentially allowing detailed reverberation mapping studies of a quasar at minimal cost.

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

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.

Simultaneous Estimation of Time Delays and Quasar Structure

Gravitationally lensed quasars can be used to map the mass distribution in lensing galaxies and to estimate the Hubble constant H-0 by measuring the time delays between the quasar images. Here we report the measurement of two independent time delays in the quadruply imaged quasar WFI J2033-4723 (z = 1.66). Our data consist of R-band images obtained with the Swiss 1.2 m EULER telescope located at La Silla and with the 1.3 m SMARTS telescope located at Cerro Tololo. The light curves have 218 independent epochs spanning 3 full years of monitoring between March 2004 and May 2007, with a mean temporal sampling of one observation every 4th day. We measure the time delays using three different techniques, and we obtain Delta t(B-A) = 35.5 +/- 1.4 days (3.8%) and Delta t(B-C) = 62.6(-2.3)(+4.1) days ((+6.5%)(-3.7%)), where A is a composite of the close, merging image pair. After correcting for the time delays, we find R-band flux ratios of F-A/F-B = 2.88 +/- 0.04, F-A/F-C = 3.38 +/- 0.06, and F-A1/F-A2 = 1.37 +/- 0.05 with no evidence for microlensing variability over a time scale of three years. However, these flux ratios do not agree with those measured in the quasar emission lines, suggesting that longer term microlensing is present. Our estimate of H-0 agrees with the concordance value: non-parametric modeling of the lensing galaxy predicts H-0 = 67(-10)(+13) km s(-1) Mpc(-1), while the Single Isothermal Sphere model yields H-0 = 63(-3)(+7) km s(-1) Mpc(-1) (68% confidence level). More complex lens models using a composite de Vaucouleurs plus NFW galaxy mass profile show twisting of the mass isocontours in the lensing galaxy, as do the non-parametric models. As all models also require a significant external shear, this suggests that the lens is a member of the group of galaxies seen in field of view of WFI J2033-4723.