Nicholas D. Morgan

The Quasar Accretion Disk Size-Black Hole Mass Relation

We use the microlensing variability observed for 11 gravitationally lensed quasars to show that the accretion disk size at a rest-frame wavelength of 2500 A is related to the black hole mass by log(R 2500/cm) = (15.78 ± 0.12) + (0.80 ± 0.17)log(M BH/109 M ☉). This scaling is consistent with the expectation from thin-disk theory (R M 2/3 BH), but when interpreted in terms of the standard thin-disk model (T R –3/4), it implies that black holes radiate with very low efficiency, log(η) = –1.77 ± 0.29 + log(L/L E), where . Only by making the maximum reasonable shifts in the average inclination, Eddington factors, and black hole masses can we raise the efficiency estimate to be marginally consistent with typical efficiency estimates (η 10%). With one exception, these sizes are larger by a factor of ~4 than the size needed to produce the observed 0.8 μmxa0 quasar flux by thermal radiation from a thin disk with the same T R –3/4 temperature profile. While scattering a significant fraction of the disk emission on large scales or including a large fraction of contaminating line emission can reduce the size discrepancy, resolving it also appears to require that accretion disks have flatter temperature/surface brightness profiles.

The Time Delays of Gravitational Lens HE 0435–1223: An Early-Type Galaxy with a Rising Rotation Curve*

We present Hubble Space Telescope images and 2 years of optical photometry of the quadruple quasar HE 0435� 1223. The time delays between the intrinsic quasar variations aretAD ¼� 14:37 þ0:75 � 0:85 , � tAB ¼� 8:00 þ0:73 � 0:82 ,a nd � tAC ¼� 2:10 þ0:78 � 0:71 days. We also observed nonintrinsic variations of � 0.1 mag yr� 1 that we attribute to micro- lensing. Instead of the traditional approach of assuming a rotation curve for the lens galaxy and then deriving the Hubbleconstant(H0),we assumeH0 ¼ (72 � 7) km s� 1Mpc� 1andderiveconstraintsontherotationcurve.Onthe scale over which the lensed images occur (1B2 ¼ 5 h � 1 kpc 1:5Re), the lens galaxy must have a rising rotation curve,anditcannothaveaconstantmass-to-lightratio.Theseresultsaddtotheevidencethatthestructuresofearly- type galaxies are heterogeneous. Subject headingg cosmological parameters — dark matter — galaxies: kinematics and dynamics — gravitational lensing — quasars: individual (HE 0435� 1223)

The Spatial Structure of an Accretion Disk

Based on the microlensing variability of the two-image gravitational lens HE 1104-1805 observed between 0.4 and 8 μm, we have measured the size and wavelength-dependent structure of the quasar accretion disk. Modeled as a power law in temperature, T ∝ R−β, we measure a B-band (0.13 μm in the rest frame) half-light radius of R1/2,B = 6.7+ 6.2−3.2 × 1015 cm (68% confidence level) and a logarithmic slope of β = 0.61+ 0.21−0.17 (68% confidence level) for our standard model with a logarithmic prior on the disk size. Both the scale and the slope are consistent with simple thin disk models where β = 3/4 and R1/2,B = 5.9 × 1015 cm for a Shakura-Sunyaev disk radiating at the Eddington limit with 10% efficiency. The observed fluxes favor a slightly shallower slope, β = 0.55+ 0.03−0.02, and a significantly smaller size for β = 3/4.

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

Optical and X-Ray Observations of GRB 060526: A Complex Afterglow Consistent with an Achromatic Jet Break

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

Microlensing of the Lensed Quasar SDSS 0924+0219*

-->. 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.

The Lens Redshift and Galaxy Environment for HE 0435−1223*

We obtained 98 R-band and 18 B, r, i images of the optical afterglow of GRB 060526 (z = 3.21) with the MDM 1.3 m, 2.4 m, and the PROMPT telescopes at CTIO over the five nights following the burst trigger. Combining these data with other optical observations reported in GCN and the Swift XRT observations, we compare the optical and X-ray afterglow light curves of GRB 060526. Both the optical and X-ray afterglow light curves show rich features, such as flares and breaks. The densely sampled optical observations provide very good coverage at T > 104 s. We observed a break at 2.4 × 105 s in the optical afterglow light curve. Compared with the X-ray afterglow light curve, the break is consistent with an achromatic break supporting the beaming models of GRBs. However, the prebreak and postbreak temporal decay slopes are difficult to explain in simple afterglow models. We estimated a jet angle of θj ~ 7° and a prompt emission size of Rprompt ~ 2 × 1014 cm. In addition, we detected several optical flares with amplitudes of Δm ~ 0.2, 0.6, and 0.2 mag. The X-ray afterglows detected by Swift have shown complicated decay patterns. Recently, many well-sampled optical afterglows also show decays with flares and multiple breaks. GRB 060526 provides an additional case of such a complex, well-observed optical afterglow. The accumulated well-sampled afterglows indicate that most of the optical afterglows are complex.

MID-IR OBSERVATIONS AND A REVISED TIME DELAY FOR THE GRAVITATIONAL LENS SYSTEM QUASAR HE 1104 1805

We analyze V-, I-, and H-band HST images and two seasons of R-band monitoring data for the gravitationally lensed quasar SDSS 0924+0219. We clearly see that image D is a point-source image of the quasar at the center of its host galaxy. We can easily track the host galaxy of the quasar close to image D because microlensing has provided a natural coronograph that suppresses the flux of the quasar image by roughly an order of magnitude. We observe low-amplitude, uncorrelated variability between the four quasar images due to microlensing, but no correlated variations that could be used to measure a time delay. Monte Carlo models of the microlensing variability provide estimates of the mean stellar mass in the lens galaxy (0.03 h2 M☉ M 2.0 h2 M☉), the accretion disk size (the disk temperature is 5 × 104 K at 1.3 × 1014 h-1 cm rs 4.7 × 1014 h-1 cm), and the black hole mass (6.6 × 106 M☉ MBH h3/2 η (L/LEdd)1/2 4.4 × 107 M☉), all at 68% confidence. The black hole mass estimate based on microlensing is mildly inconsistent with an estimate of MBH = (2.8 ± 0.9) × 108 M☉ from the Mg II emission-line width. If we extrapolate the best-fitting light curve models into the future, we expect images A and B to fade and images C and D to brighten. In particular, we estimate that image D has a roughly 16% probability of brightening by a factor of 2 during the next year and a 40% probability of brightening by an order of magnitude over the next decade.

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

The redshift of the galaxy lensing HE 0435-1223 is 0.4546 ± 0.0002, based on observations obtained with the Low Dispersion Survey Spectrograph 2 on the Magellan Consortiums 6.5 m Clay Telescope. Hubble Space Telescope Advanced Camera for Surveys observations of the system also reveal a spiral-rich group of 10 galaxies within 40 of the elliptical lensing galaxy. The redshifts for two of these galaxies were measured to be in the foreground (at z = 0.419) with respect to the lens; thus, at least some of the nearby galaxies are not part of the same physical group as the lens. Mass models of the system (assuming same-plane deflectors) that take the local galaxy environment into account do better at explaining the observed emission-line flux ratios (which are presumably unaffected by microlensing) than single-halo models, but the match is still not perfect. In particular, component A (a minimum of the light travel time) is observed to be 0.20 mag brighter than predicted, and component C (also a minimum image) is observed to be 0.16 mag fainter than predicted. The A - D time delay is predicted to be either 15.8 or 17.6 days (H0 = 72 km s-1 Mpc-1), depending on the details of the local galaxy environment.

Simultaneous Estimation of Time Delays and Quasar Structure

The mid-IR flux ratios FA/FB = 2.84 ± 0.06 of the two images of the gravitationally lensed quasar HE 1104-1805 show no wavelength dependence to within 3% across 3.6-8.0 μm, show no time dependence over 6 months, and agree with the broad emission-line flux ratios. This indicates that the mid-IR emission likely comes from scales large enough to be little affected by microlensing and that there is little differential extinction between the images. We measure a revised time delay between these two images of 152.2 (1 σ) days from R- and V-band data covering the years 1997-2006. This time delay indicates that the lens has an approximately flat rotation curve over scales of 1-2Re. We also observed uncorrelated variations of ~0.05 mag yr-1, which we attribute to microlensing of the optical emission from the accretion disk. The optical colors have also changed significantly in the sense that image A is now redder than image B, rather than bluer, as it was in 1993.