1. Measuring the properties of QSO broad- line regions with the GMOS IFU. Randall Wayth with Matt O'Dowd & Rachel Webster.

2. Outline  Motivation  Introduction to 2237+0305  Observations & Data reduction  Emission line flux ratios  Microlensing of QSO emission regions  Constraints on emitting region size

3. Motivation - QSO emission regions  QSO continuum/line emission regions are too small to resolve  Reverberation mapping suggests they are very small  Gravitational lensing magnifies objects. If a source is resolved in a lensed image, then we can directly determine its true size & surface brightness  If not resolved, then microlensing should create different magnifications for the continuum and broad-line regions of the QSO.

4. 2237+0305  Barred spiral (Sbc) galaxy at low redshift (z=0.04) lensing z=1.69 radio quiet QSO.  Four images of QSO formed around galaxy bulge with separation ~1-2 arcsec  Lensing offers unique opportunity to study QSO continuum and emission line region size/structure Properties of dark matter halo (shape, cuspiness, clumpiness) Mass function of galaxy bulge stars, and more...

5. 2237+0305 15 second r-band acquisition image N E

6. 2237+0305 Same image, different contrast

7. 2237+0305 A D B C Galaxy centre QSO image labels follow Yee (1988)

8. Is the CIII] emission region in 2237+0305 resolved?  Mediavilla et al. (1998) claimed seeing an arc of resolved CIII] emission using INTEGRAL IFU on WHT. (0.5” separation, rectangular array, 0.45” fibre diameter)  If real, we can “undo” the effects of lensing and create a true image of the emission region. From Mediavilla et al. (1998) ApJ 503 L27

9. Data - GMOS IFU  IFU is a hexagonal lenslet array with separation 0.2”  R400 grating in “one slit” mode. Useful wavelength range ~500-850nm. Object coverage is 5”x3”.  8 x 30min exposures taken on 16/17 July, 2002. We use 5 of the 8 frames. Seeing 0.6” Object Sky

10. Aims  Confirm/refute existence of arc of emission  If real, make an image of the QSO BELR!  If not real, examine effect of lensing on the relative strengths of continuum and broad-line emission from the QSO

11. Data QSO spectrum Galaxy spectrum A B D C CIII] MgII

12. Line flux extraction CIII] line Continuum MgII line

13. Images of the broad-line flux  Subtracting surrounding continuum from the emission lines leaves the line flux  Subtraction is quite clean  Notice difference in brightness of QSO images CIII] continuum CIII] - emission line MgII continuum MgII – emission line Arc or PSF overlap?

14. PSF modelling & subtraction  We are looking for a faint arc, so we need to create an accurate PSF and subtract the QSO images.  Method combine line images for the 5 good frames define a mask around each QSO image including a region which is uncontaminated by other images cut out, rescale and combine sections from each image use this PSF, to subtract QSO images, iterate a few times

15. PSF model Uncontaminated regions Combined PSF ( MgII )

16. Line images with QSOs subtracted Unresolved! - No arc in MgII or CIII]! Peak residual ~10% MgII CIII]

17. Microlensing and the BELR  Microlensing by stars in the lens galaxy's bulge project a network of “caustics” onto the QSO.  Parts of the source crossing caustics (red/yellow) are highly magnified.  The QSO can be differentially magnified depending on its size relative to the caustic network. Microlensing caustic network Image courtesy Joachim Wambsganss

18. Microlensing and the BELR  Small source = no differential magnification  All parts of the source are equally magnified

19. Microlensing and the BELR  Medium source = differential magnification!  If the QSO's continuum region is much smaller than the BELR, then the continuum should be more highly magnified.

20. Flux ratios A D B C Galaxy centre  Extinction corrected flux ratios for continuum and broad-lines are certainly different!  Without microlensing, all images should have approx same magnitude, so BELR is also microlensed.  Because MgII and CIII] lines have same flux ratio, they must be similar size.  BELR size ~0.06pc based on simulations of Wyithe et. al 2002 (MNRAS 331)

21. Next: de-dispersed spectral ratios  After correcting for atmospheric dispersion, take ratios of image spectra  Broad-line magnifications clearly visible  Shape of continuum is a function of source morphology, microlensing and extinction  Shape/location of lines depends on BELR structure! C/A D/A B/A 5000 6000 7000 8000

22. Summary  Using GMOS-N IFU we have taken the best spectroscopic data of 2237+0305 to date  We find no arc of emission in either the CIII] or MgII line, contrary to previous claims  Magnification ratios of the images in both the continuum and broad-lines show microlensing  BELR is measured from flux ratios to be ~0.06pc. This estimate will improve using de- dispersed data.  MNRAS 359 561 (2005)

23. Line flux extraction  MgII line flux = sum spectrum between (7478, 7584) Angstroms – continuum spectrum between (7421,7478) and (7684,7740). The region of sky absorption is ignored  CIII] line flux = sum spectrum between (5078,5208) - sum of continuum between (5013,5078) and (5209,5273)