Friday, 12 November 2010

A Compact Early-type Galaxy at z = 0.6 Under a Magnifying Lens

By Auger et al.

Figure 1. Keck LGS-AO imaging of the EEL SDSSJ1347-0101 (left). The image is well modelled using a singular isothermal ellipsoid mass distribution for the lensing mass, a single Sersic component for the lensing galaxy, and a two-component de Vaucouleurs and Sersic profile for the background source (right), while a single-component fit to the source leaves a ring of residual flux (centre); the scaling of the two residual plots is set to saturate at 3 times the background noise level. The Kp-band imaging reveals an observed source magnitude of 17.6 but this is corrected to 20.3 when the magnification from lensing is taken into account; the inferred stellar mass of the source is 10^10.9M⊙ and the half-light radius of the two-component surface brightness model is 0.′′16 or 1.1 kpc at the redshift of the source.

Thursday, 4 November 2010

Rapid QSO shutdown in Hanny's Voorwerp

Schawinski et al (2010, presents interesting X-ray observations of Hanny's Voorwerp. They argue that the light from the Voorwerp (the green fuzz above) is caused by ionizing radiation from an AGN in the center of the host galaxy IC 2497. However their X-ray data show only a weak AGN, much too weak to explain the emission lines in the Voorwerp they argue (by 2-4 orders of magnitude). The inference is thus that the Voorwerp is a light echo of a QSO phase that terminated < 70,000 years ago. This is a rapid turn-off and more extreme than what you would expect by scaling up an X-ray binary for instance.