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Science Spotlight from this week's observations

Proposal ID = 12579
Principle Investigator =   Joanna Holt  -  Sterrewacht Leiden
Title = "AGN feedback in young, radio-loud AGN"
Time = May 14, 2012, 22:56:53 - 23:57:05
Target = PKS-0023-26
Instrument = ACS/WFC

Background:

The "Cold Dark Matter" (CDM) paradigm for the formation of galaxies is one of the mainstays of modern astronomy. The primary evidence comes from detailed cosmological simulations. One of the basic results is that galaxies form in a hierarchical sequence, with smaller, low mass galaxies forming first and then merging together to form larger galaxies. While these simulations have been successful in explaining a wide range of galactic properties, a key, poorly known parameter is the nature and amount of "feedback", i.e., the degree to which outflows from Active Galactic Nuclei (AGNs), and star formation in general, retard the formation of new stars. This proposal aims to provide some of the basic information needed to better quantify AGN feedback, such as the mass outflow rates and the total amount of energy produced by AGNs. This will allow modelers to better simulate the actual physical processes involved in feedback, rather than making it a largely free parameter in their models.

Paraphrasing from the abstract:

AGN feedback is now routinely included in both galaxy evolution models and cosmological simulations, yet large uncertainties remain about the most important parameters, such as the mass outflow rates, bulk kinetic powers and the dominant outflow driving mechanisms. In order to address this issue, we propose to make HST ACS/WFC observations of a small, complete sample of compact (young) radio sources which have clear evidence for strong emission line outflows. Compact radio sources are ideal sources for studying AGN feedback as in addition to being young, recently triggered AGN, all potential outflow drivers are present in these sources (AGN winds/starbursts/radio jets). We will use the unique capabilities of HST ACS/WFC to map the outflowing regions with high spatial resolution to determine the dominant outflow driving mechanism. Furthermore, the morphological information, in combination with our new high resolution VLT/X-Shooter spectra (which cover the entire optical - near-IR wavelength range simultaneously), will allow us to accurately calculate the outflow energetics in these sources. Such studies are crucial for determining whether AGN feedback in real galaxies can achieve the requirements made by simulations.


You can find most of this information and more from the following webpage: http://www.stsci.edu/hst/ by entering "12579" in the Prop. ID box.