2,340 research outputs found
Synergies between SALT and Herschel, Euclid & the SKA: strong gravitational lensing & galaxy evolution
Gravitational lensing has seen a surge of interest in the past few years. The handful of strong lensing systems known in the year 2000 has now been replaced with hundreds, thanks to innovative multi-wavelength selection, and there is an imminent prospect of thousands of lenses from Herschel and other sub-millimetre surveys. Euclid and the Square Kilometre Array promise tens or even hundreds of thousands. Gravitational lensing is one of the very few probes capable of mapping dark matter halo distributions. Lensing also provides independent cosmological parameter estimates and enables the study of galaxy populations that are otherwise too faint for detailed study. SALT is extremely well placed to have an enormous impact with follow-up observations of foreground lenses and background sources from e.g. Herschel, the South Pole Telescope, the Atacama Cosmology Telescope, Euclid and the Square Kilometre Array. This paper reviews the prospects for high-impact SALT science and the many constraints of galaxy evolution that can result
Herschel ATLAS: The cosmic star formation history of quasar host galaxies
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 I_(AB) > -32 We use the science demonstration observations of the first ~16 deg^2 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 μm. 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 > I_(AB) > -24 have a comoving star formation rate (derived from 100 μm rest-frame luminosities) peaking between redshifts of 1 and 2, while high-luminosity quasars with I_(AB) I_(AB) > -24 quasars evolves as (1 + z)^(2.3±0.7) at z I_(AB) > -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
HST imaging of redshift z>0.5 7C and 3C Quasars
We present preliminary results from HST imaging of radio-loud quasar hosts,
covering a ~x100 range in radio luminosity but in a narrow redshift range (0.5
to 0.65). The sample was selected from our new, spectroscopically complete 7C
survey and the 3CRR catalogue. Despite the very large radio luminosity range,
the host luminosities are only weakly correlated (if at all) with radio power,
perhaps reflecting a predominance of purely central engine processes in the
formation of radio jets, and hence perhaps also in the radio-loud/-quiet
dichotomy at these redshifts. The results also contradict naive expectations
from several quasar formation theories, but the host magnitudes support
radio-loud Unified Schemes.Comment: To appear in the Proceedings of the ESO/IAC Conference on 'Quasar
Hosts' - Tenerife 24-27 September 199
IRAS F10214+4724: the inner 100pc
We use new near-infrared spectroscopy and our published optical spectroscopy
of the gravitationally-lensed Seyfert-2 galaxy F10214+4724 to study both the
links between the starburst and AGN in this object and the properties of the
inner narrow-line clouds. The UV spectrum is consistent with a compact,
moderately- reddened starburst providing about half the UV light. Spectroscopy
of the Halpha /[NII] line blend has enabled us to distinguish emission from the
narrow-line region of the Seyfert-2 and a moderately-reddened emission line
region which we argue is associated with the starburst. Estimates of the star
formation rate from the UV continuum flux and the Halpha flux are broadly
consistent. We can explain the unusual emission line properties of F10214+4724
in terms of conventional models for nearby Seyfert-2 galaxies if lensing is
preferentially magnifying the side of the inner narrow-line region between the
AGN and the observer, and the other side is both less magnified and partially
obscured by the torus. The hydrogen densities of clouds in this region are high
enough to make the Balmer lines optically thick and to suppress forbidden
emission lines with low critical densities. We have deduced the column density
of both ionised and neutral gas in the narrow-line clouds, and the density of
the ionised gas. Using these we have been able to estimate the mass of the
inner narrow-line clouds to be ~ 1 solar mass, and show that the gas:dust ratio
NH/E(B-V) in these clouds must be ~1.3x10^{27}m^{-2}mag^{-1}, significantly
higher than in the Milky Way. The cloud properties are consistent with the
those of the warm absorbers seen in the X-ray spectra of Seyfert-1 galaxies.
Our results favour models in which narrow-line clouds start close to the
nucleus and flow out.Comment: 13 pages, 5 figures. Accepted by MNRA
Finding bright <i>z</i> ≥ 6.6 Ly <i>α</i> emitters with lensing: prospects for <i>Euclid</i>
We model the Ly luminosity function to estimate the
number of lensed high Ly emitters that may be detected by the
Euclid Deep Survey. To span the whole range of possible predictions we exploit
two Ly luminosity function models and two strong gravitational lensing
models from the literature. We show that the planned Euclid Deep Survey
observing 40 deg over the 920-1850 nm wavelength range down to a flux limit
of erg scm will enable us to find
between and deg lensed Ly emitters at depending on the adopted Ly luminosity function and strong
gravitational lensing model. The obvious [OII], [OIII] and H
contaminants of the Ly lensed population will be identified with the
help of Euclid's spectral resolving power, while the SKA will enable the
identification of the interloper population of H emitters. By combining
Euclid and the SKA, we will thus be able to identify, for the first time, a
sample of to lensed Ly emitters at .Comment: Accepted for publication in MNRAS on 20 June 2017. (NEW: Amended
Latex
GENIE observations of small scale astrophysical processes in star forming regions and quasars
The VLTI/GENIE configuration will operate using at least 4 of the VLTI
telescopes (and possibly with one or more of the AT telescopes in the future if
adaptive optics become available on them). GENIE effectively can be thought of
as a 'smart' coronagraph, enabling high dynamic range imaging to be achieved at
moderate spatial resolution, with high rejection of the emission of a central
bright point source. However, but this bright source rejection may only provide
a rather moderate image quality (due to the few baselines and transfer function
on the sky). Operated in this way, only limited image reconstruction is
possible since classical radio and millimeter wavelength interferometry
techniques are not directly applicable to the outputs of optical
interferometers because the absolute phases are generally not measured.
However, measurements of visibility and closure phase could lead to situations
where image reconstruction becomes possible. This paper addresses the issue of
whether there are areas outside of the exoplanet search where it might be able
to make a useful impact on astronomy.Comment: Proceedings of the Genie-Darwin Workshop - Hunting for Planet
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