Complementary Data & Observations

Space-based Mid-Infrared Observations with Spitzer

(PI Klaus Meisenheimer, MPIA)

Before proposing the Herschel GT Key Project in April 2007, about 1/3 of the high-z QSOs (z > 3) had no Spitzer IRAC/MIPS 24 μm coverage. A Spitzer medium-sized proposal led by Klaus Meisenheimer (PI) got awarded 70 hours of observing time. With these new observations all high-z QSOs (z > 3) from our Herschel Source List will also have Spitzer IRAC/MIPS 24 μm observations.

These observations are the essential short wavelength complement to our Herschel guaranteed time Key Project. The combined Spitzer plus Herschel photometry will characterize the overall Mid- to Far-Infrared SEDs of a large sample of quasars at the highest redshifts in great detail and thus provide a data base of profound legacy value.

The proposed Spitzer observations will cover rest-frame wavelengths between 0.5 and 4 μm which will allow us to detect the hottest dust as an excess of the measured 24 μm flux (above the UV-optical continuum as derived from the IRAC bands and NIR photometry). Our observations will enlarge the number of z>5 QSOs observed in the infrared by a factor of 4. This allow us to determine the frequency of peculiar (dust-free ?) objects detected in previous studies and to carry out statistical investigations of the relation between UV-optical spectrum from the accretion disk and the emission from the hottest part of the dust torus.

From September 2007 until February 2009 we obtained Spitzer observations for all our proposed targets. The first analysis of our data shows that all quasars are detected in the four IRAC bands and - except of a handful sources - also in the MIPS 24 μm bands, see also our first results.

Ground-based Near-Infrared Observations

(PI Klaus Meisenheimer, MPIA)

We plan to conduct near-infrared observations with telescopes at Calar Alto and La Silla in the Y, J, H and K band. We were granted 4 nights in service mode to perform Y, J, H and K imaging at Calar Alto with the NIR camera Omega 2000 at the 3.5 m telescope during the second half year of 2008 and data for 24 QSOs at z>5 have been obtained.

Millimeter Observations

We plan to follow-up all objects lacking observations in the (sub)-mm window with IRAM and ESO facilities.