Quantitative Interpretation of Quasar Microlensing Light Curves

By C. Kochanek. 2003

219 citations recorded by the source corpus.

We develop a general method for analyzing the light curves of microlensed quasars and apply it to the OGLE light curves of the four-image lens Q2237+0305. We simultaneously estimate the effective source velocity, the average stellar mass, the stellar mass function, and the size and structure of the quasar accretion disk. The light curves imply an effective source-plane velocity of 10,200 km s-1 ≲ veh⟨M/M☉⟩-1/2 ≲ 39,600 km s-1 (68% confidence). Given an independent estimate for the source velocity, found by combining estimates for the peculiar velocity of the lens galaxy with its measured stellar velocity dispersion, we obtain a mean stellar mass of ⟨M⟩ ≃ 0.037 h2 M☉ (0.0059 h2 M☉ ≲ ⟨M⟩ ≲ 0.20 h2 M☉). We were unable to distinguish a Salpeter mass function from one in which all stars had the same mass, but we do find a strong lower bound of κ*/κ ≳ 0.5 on the fraction of the surface mass density represented by the microlenses. Our models favor a standard thin accretion disk model as the source structure over a simple Gaussian source. For a face-on, thin disk radiating as a blackbody with temperature profile Ts ∝ R-3/4, the radius rs where the temperature matches the filter pass band [2000 Å or Ts(rs) ≃ 7 × 104 K] is 1.4 × 1015 h-1 cm ≲ rs ≲ 4.5 × 1015 h-1 cm. The flux predicted by the disk model agrees with the observed flux of the quasar, so nonthermal or optically thin emission processes are not required. From the disk structure we estimate a black hole mass of MBH ≃ 1.1 × 109 h-3/2η(L/LE)-1/2 M☉, consistent with the mass estimated under the assumption that the quasar is radiating at the Eddington luminosity (L/LE = 1).

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/523ed5796c6943290642a0cb88c4b6f4561afb1b

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Citations in the corpus

A SHARP view of H0LiCOW: H0 from three time-delay gravitational lens systems with adaptive optics imaging (2019, background): “= 0.3M and the ratio between the upper and lower masses Mupper/Mlower = 100 (Kochanek 2004).”
THE SIZES OF THE X-RAY AND OPTICAL EMISSION REGIONS OF RXJ 1131–1231 (2009, methodology): “We modeled the relative velocities as in Kochanek (2004), where for RXJ1131 the projection of the CMB dipole velocity (Kogut et al. 1993) on the lens plane is 47 km/s, the lens velocity dispersion estimated from the Einstein radius is 350 km/s, and the estimated rms peculiar velocities of the lens…”
KEPLER OBSERVATIONS OF RAPID OPTICAL VARIABILITY IN ACTIVE GALACTIC NUCLEI (2011, unknown): “Because this region is too small to image (except via gravitational lensing; Kochanek 2004), indirect methods must be used to probe its structure and physical conditions.”
The Time Delays of Gravitational Lens HE 0435–1223: An Early-Type Galaxy with a Rising Rotation Curve (2005, methodology): “It should be possible to go beyond the ensemble analysis and analyze the light curves of individual systems in detail, now that there is a method for analyzing quasar microlensing light curves of arbitrary complexity (Kochanek 2004).”
SIZES AND TEMPERATURE PROFILES OF QUASAR ACCRETION DISKS FROM CHROMATIC MICROLENSING (2010, methodology): “We followed Kochanek (2004) in setting the presentday velocity dispersion of galaxies σpec to 235 km s−1.”
The Evolution and Structure of Early-Type Field Galaxies: A Combined Statistical Analysis of Gravitational Lenses (2004, background): “…of lensed images can also help break the degeneracy because the light curves can be used to determine the fraction of the surface mass density in the form of stars (Kochanek 2004; see also Schechter &Wambsganss 2002 for a discussion of statistical constraints based on flux ratio anomalies).”