Integral-field spectrophotometry of the quadruple QSO HE 0435-1223: Evidence for microlensing

Abstract

Abstract. We present the first spatially resolved spectroscopic observations of the recently discovered quadruple QSO and gravitational lens HE 0435−1223. Using the Potsdam Multi-Aperture Spectrophotometer (PMAS), we show that all four QSO components have very similar but not identical spectra. In particular, the spectral slopes of components A, B, and D are indistinguishable, implying that extinction due to dust plays no major role in the lensing galaxy. While also the emission line profiles are identical within the error bars, as expected from lensing, the equivalent widths show significant differences between components. Most likely, microlensing is responsible for this phenomenon. This is also consistent with the fact that component D, which shows the highest relative continuum level, has brightened by 0.07 mag since Dec. 2001. We find that the emission line flux ratios between the components are in better agreement with simple lens models than broad band or continuum measurements, but that the discrepancies between model and data are still unacceptably large. Finally, we present a detection of the lensing galaxy, although this is close to the limits of the data. Comparing with a model galaxy spectrum, we obtain a redshift estimate of z lens = 0.44 ± 0.02.

Probing the Broad-Line Region and the Accretion Disk in the Lensed Quasars HE 0435-1223, WFI 2033-4723, and HE 2149-2745 Using Gravitational Microlensing

“…This confirms the expectation that the cores are not very sensitive to microlensing and that extinction is not significantly present in this lens system (in agreement with Wisotzki et al 2003;Morgan et al 2005). In Figure 2 we show the continuum ratio values available from the literature and those obtained from the spectra used in the present work.…”

Influence of Microlensing on Spectral Anomalies of the Lensed Objects

“…The influence of microlensing on the spectra (continuum and spectral lines) of the lensed QSOs has been investigated theoretically (e.g., Wambsganss & Paczynski 1991;Popović et al 2001;Abajas 2002;Abajas et al 2007, etc.). Some observational effects have been also described by Lewis et al (1998), Mediavilla et al (1998), Wisotzki et al (2003), Richards et al (2004), Mosquera et al (2011), Sluse et al (2011 and others. The flux anomalies have been observed in the spectra of a number of quasars (e.g., see Kratzer et al 2011).…”

Spectra of faint sources in crowded fields with FRODOSpec on the Liverpool Robotic Telescope

“…In order to obtain accurate fluxes for the two quasar images of the lens system q0957, we use a method similar to that presented in Wisotzki et al (2003). The Wisotzki et al's procedure was successfully applied to IFS data of the quadruply lensed quasar HE 0435−1223.…”

“…The Wisotzki et al's procedure was successfully applied to IFS data of the quadruply lensed quasar HE 0435−1223. At each wavelength (monochromatic frame), Wisotzki et al (2003) decomposed this lens system into four point-like sources (quasar images) convolved with analytical 2D-Gaussian PSFs, plus a spatially constant background. In other words, each quasar image in each monochromatic frame was initially characterised by six free parameters: centroid, FWHM along major and minor axis, position angle and amplitude.…”

“…It is better to use a PSF fitting method Roth et al 2004;Wisotzki et al 2003). An additional complication arises as a result of the differential atmospheric refraction, which causes source position variations with wavelength (Filippenko 1982).…”