Image of Alice in Wonderland at the Mad Hatter's tea party You are cordially invited to afternoon tea and biscuits wine and chocolate

Astronomy Tea Talks at Caltech

Mondays, Hameetman auditorium (Cahill)
Tea:  4.00pm
Talk: 4.15pm

Organized by:

2010 - 2011 season:
28 Feb 2011 Mark Ammons (UoA)

'New Insights into the Use of Cosmic Telescopes and the Role of AGN Feedback in Galaxy Formation'

I will discuss the observable consequences of black hole-mediated feedback in massive galaxies, and in the more distance universe, the use of cosmic telescopes to magnify distant sources into observability.

AGN feedback may contribute to quenching of star formation by the expulsion or heating of cold gas, causing the host galaxy to evolve onto the red sequence while a central quasar is revealed as unobscured. However, the u-R colors and color gradients of obscured and unobscured AGN at z ~ 0.5-2 in GOODS are similar. This is inconsistent with rapid, extended quenching mediated by feedback processes in high luminosity AGN (log LX > 43.5 ergs/s) at z = 0.5-2.0, so new interpretations are necessary. The relationship between black hole growth and host galaxy assembly may also be probed by placing active mergers on the M-sigma relation. We use the OSIRIS IFU at Keck to directly observe the Keplerian rotation of stars around the southern black hole in the active merger NGC6240. Modeling of 2-D kinematics reveals a black hole of ~9x10^8 solar masses, nearly on the M-sigma relation, hinting that black hole and bulge growth are simultaneous during a merger.

At higher redshifts, it is not known whether the reionization of the universe at z ~ 6-10 was caused by bright sources alone or with faint sources in concert. I discuss the use of massive clusters as cosmic telescopes to lens faint objects into detectability to constrain the luminosity function at these redshifts. It is debated whether cosmic telescopes are more efficient than blank field surveys in doing so. Multiple-plane lensing simulations with realistic assumptions for the intrinsic size and shapes of sources indicate that detection of z ~ 10 sources is less likely in regions of high magnification (> 20). This suggests that spectroscopic slits should be placed just off the lines of infinite magnification in critical-line surveys for Lyman-alpha emitters at z ~ 10.
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Last modified on 20th Jul 2011 by Dominik A. Riechers.  

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