Galaxy formation and evolution

Abstract:

The Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS) has uncovered a population of strongly lensed submillimeter galaxies (SMGs). The Zpectrometer instrument on the Green Bank Telescope (GBT) was used to measure the redshifts and constrain the masses of the cold molecular gas reservoirs for two candidate highredshift lensed sources. We derive CO(1-0) redshifts of z = 3.042 ± 0.001 and z = 2.625 ± 0.001, and measure molecular gas masses of (1-3) ×1010M⊙, corrected for lens amplification and assuming a conversion factor of α = 0.8 M ⊙ (Kkm s-1 pc2)-1. We find typical L(IR)/L'(CO) ratios of 120 ±40 and 140±50L ⊙ (Kkm s-1 pc2)-1, which are consistent with those found for local ultraluminous infrared galaxies (ULIRGs) and other high-redshift SMGs. From analysis of published data, we find no evidence for enhanced L(IR)/L'(CO(1-0)) ratios for the SMG population in comparison to local ULIRGs. The GBT results highlight the power of using the CO lines to derive blind redshifts, which is challenging for the SMGs at optical wavelengths given their high obscuration. © 2011. The American Astronomical Society. All rights reserved. Printed in the U.S.A.

Abstract:

We demonstrate experimentally that slicer based integral field spectrographs are an attractive choice for the next generation of exoplanet direct detection instruments. By propagating a single simulated speckle though a slicer based integral field spectrograph (IFS) and performing the post processing technique of spectral deconvolution we are able to achieve a speckle rejection factor of ∼600 in broadband images (and ∼100 in individual wavelength channels) with contrasts only appearing to be limited by calibration errors in the IFS datacube. This is over an order of magnitude improvement on the current state-of-the-art and well within the requirements of EPICS (Exo Planet Imaging Camera and Spectrograph for the E-ELT) for post coronagraphic speckle rejection thus proving that slicers will not impose a limit on the achievable contrast. When using prior knowledge of the diffraction-limited size of real objects we further improve the speckle rejection factor such that it exceeds 103.

Abstract:

We examine a sample of 30 edge-on spiral and S0 galaxies that have boxy and peanut-shaped bulges.We compute model stellar kinematics by solving the Jeans equations for axisymmetric mass distributions derived from K-band images. These simple models have only one free parameter: the dynamical mass-to-light ratio, which we assume is independent of radius. Given the simplicity of the modelling procedure, the model second velocity moments are strikingly good fits to the observed stellar kinematics within the extent of our kinematic data, which typically reach ∼ 0.5-1 R25 (where R25 is the optical radius), or equivalently ∼ 2-3 Re (where Re is the effective or half-light radius).We therefore find no evidence for a dominant dark matter component within the optical disk of spiral galaxies. This is equally true of the S0s in our sample, which significantly extends previous observational constraints on dark matter in these galaxies. The predicted kinematics do deviate slightly but systematically from the observations in the bulge region of most galaxies, but we argue that this is consistent with the claim that boxy and peanut-shaped bulges are bars viewed edge-on.