Baruch T. Soifer

The most luminous far-infrared extragalactic sources

Extremely luminous far-infrared sources are difficult to explain as active sites of star formation, because their ratios of optical-to-infrared luminosities are extremely low. It is shown that brief intervals during which interacting galaxies collide can account for extremely high (more than 10 to the 11th) solar luminosities. The small fraction of the population that exhibits extreme luminosity also roughly equals the fraction of spiral galaxies expected to be observed undergoing collisions at any given time. A number of potential tests that would distinguish the model from others is proposed. 40 references.

The Discovery of Three New z > 5 Quasars in the AGN and Galaxy Evolution Survey

We present the discovery of three z > 5 quasars in the AGN and Galaxy Evolution Survey spectroscopic observations of the NOAO Deep Wide-Field Survey (NDWFS) Bootes Field. These quasars were selected as part of a larger Spitzer mid-infrared quasar sample, with no selection based on optical colors. The highest redshift object, NDWFS J142516.3+325409, at z = 5.85, is the lowest luminosity z > 5.8 quasar currently known. We compare mid-infrared techniques for identifying z > 5 quasars to more traditional optical techniques and show that midinfrared colors allow for the selection of high-redshift quasars even at redshifts at which quasars lie near the optical stellar locus and at z > 7, where optical selection is impossible. Using the superb multiwavelength coverage available in the NDWFS Bootes field, we construct the spectral energy distributions (SEDs) of high-redshift quasars from observed B_W band to 24 µm (rest-frame 600 A–3.7 µm). We show that the three high-redshift quasars have quite similar SEDs, and the rest-frame composite SED of low-redshift quasars from the literature shows little evolution compared to our high-redshift objects.We compare the number of z > 5 quasars we have discovered to the expected number from published quasar luminosity functions. While analyses of the quasar luminosity function are tenuous based on only three objects, we find that a relatively steep luminosity function with Ψ ∝ L^(-3.2) provides the best agreement with the number of high-redshift quasars discovered in our survey.

The Far Infrared and Submillimeter Background

Abstract : The authors repeat earlier observations of the infrared and submillimeter background radiation. While the measured values of the infrared background radiation remain unchanged, the high flux previously reported for the 0.4 to 1.3 mm range was not observed. This indicates that the flux cannot have been galactic or cosmic, but further observations are needed to rule out a solar cycle dependent geocoronal origin.