Zooming into the broad line region of the gravitationally lensed quasar QSO 2237 + 0305 the Einstein Cross: III. Determination of the size and structure of the Civ and Ciii emitting regions using microlensing

D. Sluse, R. Schmidt, F. Courbin, D. Hutsemékers, G. Meylan, A. Eigenbrod, T. Anguita, E. Agol, J. Wambsganss

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59 Citations (Scopus)

Abstract

Aims. We aim to use microlensing taking place in the lensed quasar QSO 2237 + 0305 to study the structure of the broad line region (BLR) and measure the size of the region emitting the Civ and Ciii] lines. Methods. Based on 39 spectrophotometric monitoring data points obtained between Oct. 2004 and Dec. 2007, we derived lightcurves for the Civ and Ciii] emission lines. We used three different techniques to analyse the microlensing signal. Different components of the lines (narrow, broad, and very broad) were identified and studied. We built a library of the simulated microlensing lightcurves that reproduce the signal observed in the continuum and in the lines provided only the source size is changed. A Bayesian analysis scheme is then developed to derive the size of the various components of the BLR. Results. 1. The half-light radius of the region emitting the Civ line is found to be RCIV∼66 +110-46 light-days = 0.06+0.09-0.04 pc = 1.7+2.8-1.1×1017 cm (at 68.3% CI). Similar values are obtained for Ciii]. Relative sizes of the carbon-line and V-band continuum emitting-regions are also derived with median values of R line/Rcont in the range 4 to 29, depending on the FWHM of the line component. 2. The size of the Civ emitting region agrees with the radius-luminosity relationship derived from reverberation mapping. Using the virial theorem, we derive the mass of the black hole in QSO 2237 + 0305 to be MBH ∼ 108.3±0.3 M⊙. 3. We find that the Civ and Ciii] lines are produced in at least 2 spatially distinct regions, the most compact one giving rise to the broadest component of the line. The broad and narrow line profiles are slightly different for Civ and Ciii]. 4. Our analysis suggests a different structure for the Civ and F ii+iii emitting regions, with the latter produced in the inner part of the BLR or in a less extended emitting region than C iv.

Original languageEnglish
Article numberA100
JournalAstronomy and Astrophysics
Volume528
DOIs
Publication statusPublished - 2011

Keywords

  • gravitational lensing: micro
  • gravitational lensing: strong
  • line: formation
  • quasars: emission lines
  • quasars: general
  • quasars: individual: QSO 2237+0305

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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