HST imaging of four gravitationally lensed quasars

Bate, N. F., Vernardos, G., O'Dowd, M. J., Neri-Larios, D. M., Webster, R. L., Floyd, D. J. E., Barone-Nugent, R. L., Labrie, K., King, A. L. & Yong, S. -Y., Oct-2018, In : Monthly Notices of the Royal Astronomical Society. 479, 4, p. 4796-4814 19 p.

Research output: Contribution to journalArticleAcademicpeer-review

  • N. F. Bate
  • G. Vernardos
  • M. J. O'Dowd
  • D. M. Neri-Larios
  • R. L. Webster
  • D. J. E. Floyd
  • R. L. Barone-Nugent
  • K. Labrie
  • A. L. King
  • S. -Y. Yong

We present new Hubble Space Telescope WFC3 imaging of four gravitationally lensed quasars: MG 0414+0534; RXJ 0911+0551; B 1422+231; WFI J2026-4536. In three of these systems we detect wavelength-dependent microlensing, which we use to place constraints on the sizes and temperature profiles of the accretion discs in each quasar. Accretion disc radius is assumed to vary with wavelength according to the power-law relationship r proportional to lambda(p), equivalent to a radial temperature profile of T proportional to r(-1/p). The goal of this work is to search for deviations from standard thin disc theory, which predicts that radius goes as wavelength to the power p = 4/3. We find a wide range of power-law indices, from p = 1.4(-0.4)(+0.5) in B 1422+231to p = 2.3(-0.4)(+0.5) in WFI J2026-4536. The measured value of p appears to correlate with the strength of the wavelength-dependent microlensing. We explore this issue with mock simulations using a fixed accretion disc with p = 1.5, and find that cases where wavelength-dependent microlensing is small tend to underestimate the value of p. This casts doubt on previous ensemble single-epoch measurements which have favoured low values using samples of lensed quasars that display only moderate chromatic effects. Using only our systems with strong chromatic microlensing we prefer p>4/3, corresponding to shallower temperature profiles than expected from standard thin disc theory.

Original languageEnglish
Pages (from-to)4796-4814
Number of pages19
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
Publication statusPublished - Oct-2018


  • accretion, accretion discs, gravitational lensing: micro, quasars: individual: MG 0414+0534, quasars: individual: RXJ 0911+0551, quasars: individual: B 1422+231, quasars: individual: WFIJ2026-4536, ACCRETION DISK, QSO 2237+0305, MG 0414+0534, DARK-MATTER, LINE REGION, SKY SURVEY, SIZE, SUBSTRUCTURE, B1422+231, Q2237+0305

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