Cosmology

Abstract:

We present observations of early-type galaxies with laser guide star adaptive optics (LGS AO) obtained at Gemini North telescope using the NIFS integral field unit (IFU). We employ an innovative technique where the focus compensation due to the changing distance to the sodium layer is made 'open loop', allowing the extended galaxy nucleus to be used only for tip-tilt correction. The purpose of these observations is to determine high spatial resolution stellar kinematics within the nuclei of these galaxies to determine the masses of the super-massive black holes. The resulting data have spatial resolution of 0.2" FWHM or better. This is sufficient to positively constrain the presence of the central black hole in even low-mass early-type galaxies, suggesting that larger samples of such objects could be observed with this technique in the future. The open-loop focus correction technique is a supported queue-observing mode at Gemini, significantly extending the sky coverage in particular for faint, extended guide sources. We also provide preliminary results from tests combining tip/tilt correction from the Gemini peripheral guider with on-axis LGS. The current test system demonstrates feasibility of this mode, providing about a factor 2-3 improvement over natural seeing. With planned upgrades to the peripheral wave-front sensor, we hope to provide close to 100% sky coverage with low Strehl corrections, or 'improved seeing', significantly increasing flux concentration for deep field and extended object studies. © 2010 SPIE.

Abstract:

We present a derivation of the star formation rate per comoving volume of quasar host galaxies, derived from stacking analyses of far-infrared to mm-wave photometry of quasars with redshifts 0 < z < 6 and absolute I-band magnitudes -22 > IAB > -32 We use the science demonstration observations of the first ∼ 16 deg2 from the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS) in which there are 240 quasars from the Sloan Digital Sky Survey (SDSS) and a further 171 from the 2dF-SDSS LRG and QSO (2SLAQ) survey. We supplement this data with a compilation of data from IRAS, ISO, Spitzer, SCUBA and MAMBO. H-ATLAS alone statistically detects the quasars in its survey area at > 5σ at 250, 350 and 500 μ m. From the compilation as a whole we find striking evidence of downsizing in quasar host galaxy formation: low-luminosity quasars with absolute magnitudes in the range -22 > IAB > -24 have a comoving star formation rate (derived from 100 μ m rest-frame luminosities) peaking between redshifts of 1 and 2, while high-luminosity quasars with IAB < -26 have a maximum contribution to the star formation density at z ∼ 3. The volume-averaged star formation rate of -22 > IAB > -24 quasars evolves as (1 + z)2.3±0.7 at z < 2, but the evolution at higher luminosities is much faster reaching (1 + z) 10±1 at -26 > IAB > -28. We tentatively interpret this as a combination of a declining major merger rate with time and gas consumption reducing fuel for both black hole accretion and star formation. © 2010 ESO.

Abstract:

The C-Band All-Sky Survey (C-BASS) aims to produce sensitive, all-sky maps of diffuse Galactic emission at 5 GHz in total intensity and linear polarization. These maps will be used (with other surveys) to separate the several astrophysical components contributing to microwave emission, and in particular will allow an accurate map of synchrotron emission to be produced for the subtraction of foregrounds from measurements of the polarized Cosmic Microwave Background. We describe the design of the analog instrument, the optics of our 6.1 m dish at the Owens Valley Radio Observatory, the status of observations, and first-look data. © 2010 SPIE.

Abstract:

The C-Band All-Sky Survey (C-BASS) aims to produce sensitive, all-sky maps of diffuse Galactic emission at 5 GHz in total intensity and linear polarization. These maps will be used (with other surveys) to separate the several astrophysical components contributing to microwave emission, and in particular will allow an accurate map of synchrotron emission to be produced for the subtraction of foregrounds from measurements of the polarized Cosmic Microwave Background. We describe the design of the analog instrument, the optics of our 6.1 m dish at the Owens Valley Radio Observatory, the status of observations, and first-look data.