Astronomical instrumentation

Abstract:

The Q/U Imaging ExperimenT (QUIET) employs coherent receivers at 43GHz and 94GHz, operating on the Chajnantor plateau in the Atacama Desert in Chile, to measure the anisotropy in the polarization of the cosmic microwave background (CMB). QUIET primarily targets the B modes from primordial gravitational waves. The combination of these frequencies gives sensitivity to foreground contributions from diffuse Galactic synchrotron radiation. Between 2008 October and 2010 December, over 10,000hr of data were collected, first with the 19 element 43 GHz array (3458hr) and then with the 90 element 94 GHz array. Each array observes the same four fields, selected for low foregrounds, together covering ≈1000 deg2. This paper reports initial results from the 43 GHz receiver, which has an array sensitivity to CMB fluctuations of 69μK√s. The data were extensively studied with a large suite of null tests before the power spectra, determined with two independent pipelines, were examined. Analysis choices, including data selection, were modified until the null tests passed. Cross-correlating maps with different telescope pointings is used to eliminate a bias. This paper reports the EE, BB, and EB power spectra in the multipole range ℓ = 25-475. With the exception of the lowest multipole bin for one of the fields, where a polarized foreground, consistent with Galactic synchrotron radiation, is detected with 3σ significance, the E-mode spectrum is consistent with the ΛCDM model, confirming the only previous detection of the first acoustic peak. The B-mode spectrum is consistent with zero, leading to a measurement of the tensor-to-scalar ratio of r = 0.35+1.06-0.87. The combination of a new time-stream "double-demodulation" technique, side-fed Dragonian optics, natural sky rotation, and frequent boresight rotation leads to the lowest level of systematic contamination in the B-mode power so far reported, below the level of r = 0.1. © 2011. The American Astronomical Society. All rights reserved.

Abstract:

The `Eagle' galaxy at a redshift of 0.77 is studied with the Oxford Short Wavelength Integral Field Spectrograph (SWIFT) and multi-wavelength data from the All-wavelength Extended Groth strip International Survey (AEGIS). It was chosen from AEGIS because of the bright and extended emission in its slit spectrum. Three dimensional kinematic maps of the Eagle reveal a gradient in velocity dispersion which spans 35-75 +/- 10 km/s and a rotation velocity of 25 +/- 5 km/s uncorrected for inclination. Hubble Space Telescope images suggest it is close to face-on. In comparison with galaxies from AEGIS at similar redshifts, the Eagle is extremely bright and blue in the rest-frame optical, highly star-forming, dominated by unobscured star-formation, and has a low metallicity for its size. This is consistent with its selection. The Eagle is likely undergoing a major merger and is caught in the early stage of a star-burst when it has not yet experienced metal enrichment or formed the mass of dust typically found in star-forming galaxies.

Abstract:

The 'Eagle' galaxy at a redshift of 0.77 is studied with the Oxford Short Wavelength Integral Field Spectrograph (SWIFT) and multiwavelength data from the All-wavelength Extended Groth strip International Survey (AEGIS). It was chosen from AEGIS because of the bright and extended emission in its slit spectrum. 3D kinematic maps of the Eagle reveal a gradient in velocity dispersion which spans 35-75 ± 10kms-1 and a rotation velocity of 25 ± 5kms-1 uncorrected for inclination. Hubble Space Telescope images suggest it is close to face-on. In comparison with galaxies from AEGIS at similar redshifts, the Eagle is extremely bright and blue in the rest-frame optical, highly star forming, dominated by unobscured star formation and has a low metallicity for its size. This is consistent with its selection. The Eagle is likely undergoing a major merger and is caught in the early stage of a starburst when it has not yet experienced metal enrichment or formed the mass of dust typically found in star-forming galaxies. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS.

Abstract:

We present ground-based MDM Observatory V-band and Spitzer/InfraRed Array Camera 3.6-m-band photometric observations of the 72 representative galaxies of the SAURON survey. Galaxies in our sample probe the elliptical E, lenticular S0 and spiral Sa populations in the nearby Universe, both in field and cluster environments. We perform aperture photometry to derive homogeneous structural quantities. In combination with the SAURON stellar velocity dispersion measured within an effective radius (σe), this allows us to explore the location of our galaxies in the colour-magnitude, colour-σe, Kormendy, Faber-Jackson and Fundamental Plane scaling relations. We investigate the dependence of these relations on our recent kinematical classification of early-type galaxies (i.e. slow/fast rotators) and the stellar populations. Slow rotator and fast rotator E/S0 galaxies do not populate distinct locations in the scaling relations, although slow rotators display a smaller intrinsic scatter. We find that Sa galaxies deviate from the colour-magnitude and colour-σe relations due to the presence of dust, while the E/S0 galaxies define tight relations. Surprisingly, extremely young objects do not display the bluest (V-[3.6]) colours in our sample, as is usually the case in optical colours. This can be understood in the context of the large contribution of thermally pulsing asymptotic giant branch stars to the infrared, even for young populations, resulting in a very tight (V-[3.6])-σe relation that in turn allows us to define a strong correlation between metallicity and σe. Many Sa galaxies appear to follow the Fundamental Plane defined by E/S0 galaxies. Galaxies that appear offset from the relations correspond mostly to objects with extremely young populations, with signs of ongoing, extended star formation. We correct for this effect in the Fundamental Plane, by replacing luminosity with stellar mass using an estimate of the stellar mass-to-light ratio, so that all galaxies are part of a tight, single relation. The new estimated coefficients are consistent in both photometric bands and suggest that differences in stellar populations account for about half of the observed tilt with respect to the virial prediction. After these corrections, the slow rotator family shows almost no intrinsic scatter around the best-fitting Fundamental Plane. The use of a velocity dispersion within a small aperture (e.g. Re/8) in the Fundamental Plane results in an increase of around 15 per cent in the intrinsic scatter and an average 10 per cent decrease in the tilt away from the virial relation. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS.