Cosmology

Abstract:

We show that high quality laser guide star (LGS) adaptive optics (AO) observations of nearby early-type galaxies are possible when the tip-tilt correction is done by guiding on nuclei while the focus compensation due to the changing distance to the sodium layer is made 'open loop'. We achieve corrections such that 40% of flux comes from R<0.2 arcsec. To measure a black hole mass (Mbh) one needs integral field observations of both high spatial resolution and large field of view. With these data it is possible to determine the lower limit to Mbh even if the spatial resolution of the observations are up to a few times larger than the sphere of influence of the black hole.

Abstract:

We present a comprehensive theoretical study, using a semi-analytical model within the standard LCDM framework, of the photometric properties of the progenitors of present-day early-type galaxies in the redshift range 00.7) spirals have 75-95% chance of being an early-type progenitor, while the corresponding probability for large blue spirals (M_B<-21.5, B-V<0.7) is 50-75%. The prescriptions developed here can be used to address, from the perspective of the standard model, the issue of `progenitor bias', whereby the exclusion of late-type progenitors in observational studies can lead to inaccurate conclusions regarding the evolution of the early-type population over cosmic time. (abridged)

Abstract:

The Very Small Array (VSA) has been used to survey the ℓ ∼ 27° to region of the Galactic plane at a resolution of 13 arcmin. This ℓ-range covers a section through the Local, Sagittarius and the Cetus spiral arms. The survey consists of 44 pointings of the VSA, each with an rms sensitivity of ∼90 mJy beam^-1. These data are combined in a mosaic to produce a map of the area. The majority of the sources within the map are H ii regions. The main aim of the programme was to investigate the anomalous radio emission from the warm dust in individual H ii regions of the survey. This programme required making a spectrum extending from GHz frequencies to the far-infrared (FIR) IRAS frequencies for each of nine strong sources selected to lie in unconfused areas. It was necessary to process each of the frequency maps with the same u, v coverage as was used for the VSA 33 GHz observations. The additional radio data were at 1.4, 2.7, 4.85, 8.35, 10.55, 14.35 and 94 GHz in addition to the 100, 60, 25 and 12 μm IRAS bands. From each spectrum the free-free, thermal dust and anomalous dust emission were determined for each H ii region. The mean ratio of 33 GHz anomalous flux density to FIR 100 μm flux density for the nine selected H ii regions was ΔS(33 GHz)/S(100 μm) = 1.10 ± 0.21 × 10^-4. When combined with six H ii regions previously observed with the VSA and the Cosmic Background Imager, the anomalous emission from warm dust in H ii regions is detected with a 33 GHz emissivity of 4.65 ± 0.40 μK (MJy sr^-1)^-1 (11.5σ). This level of anomalous emission is 0.3 to 0.5 of that detected in cool dust clouds. A radio spectrum of the H ii region anomalous emission covering GHz frequencies is constructed. It has the shape expected for spinning dust composed of very small grains. The anomalous radio emission in H ii regions is on average 41 ± 10 per cent of the radio continuum at 33 GHz. Another result is that the excess (i.e. non-free-free) emission from H ii regions at 94 GHz correlates strongly with the 100 μm emission; it is also inversely correlated with the dust temperature. Both these latter results are as expected for very large grain dust emission. The anomalous emission on the other hand is expected to originate in very small spinning grains and correlates more closely with the 25 μm emission. © 2010 The Authors. Journal compilation © 2010 RAS.