9-13 July 2012
Africa/Johannesburg timezone
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Cosmic Telescope Chromacity: apparent spectral distortions in a high-redshift, gravitationally lensed starburst/AGN

13 Jul 2012, 11:20
Oral Presentation Track D1 - Astrophysics Astrophysics


Dr Roger Deane (University of Cape Town)

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Prof Renee Kraan-Korteweg

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Abstract content <br> &nbsp; (Max 300 words)

Strong gravitational lensing provides us with our deepest views of high-redshift galaxies, the effective sensitivity and angular resolution of which will only be possible with next-generation facilities for unlensed objects. However, any conclusions based on strong-lensing observations are crucially dependent on the 'calibration' of the cosmic telescope, i.e. the robust derivation of an accurate lens model. I will present a new Bayesian Markov Chain Monte Carlo algorithm to constrain the lens model of the high-redshift source IRAS F10214+47, which is routinely used as an archetype Ultra-Luminous InfraRed Galaxy (ULIRG). Using this new model, in combination with high resolution VLBI, EVLA CO (1-0) and HST optical/UV observations, the level of effective chromacity is constrained. This is the apparent distortion of the global spectral energy distribution (SED), owing to different emission components undergoing differing magnification boosts by virtue of their relative size and proximity to the lensing caustic. I argue that emission associated with the active nucleus in IRAS F10214+47 is preferentially magnified by an order of magnitude above that of emission associated with star formation, a model which explains a number of peculiarities of this famous galaxy. The demonstration of this spectral distortion by strong-lensing raises caution in using any lensed objects as archetypical sources; as well as statistical conclusions based on samples without accurate lens models. This is particularly important for the large sample of far-infrared selected lenses recently discovered with the Herschel Space Observatory.

Primary author

Dr Roger Deane (University of Cape Town)

Presentation Materials