NOAO >   Observing Info >   Approved Programs >   2016B-0005

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Program Information for 2016B-0005


PI: Alexandra Truebenbach, U. of Colorado, alexandra.truebenbach@colorado.edu
Address: Center for Astrophysics and Space Astronomy (CASA), Campus Box 389, Boulder, CO, 80309 USA

CoI: Jeremy Darling, U. of Colorado

Title: Measuring Quasar Redshifts to Observe the Real-Time Recession and Collapse of Large-Scale Structures

Abstract: Objects and structures gravitationally decoupled from the Hubble expansion will appear to shrink in angular size as the universe expands. Observations of extragalactic proper motions can thus directly reveal the cosmic expansion without reliance on canonical cosmological models. The apparent fractional angular compression of static objects such as galaxies and galaxy clusters is ~15 microarcseconds/yr in the local universe. Pairs of gravitationally bound objects (separations less than ~ 150 Mpc) will also show a deviation from pure cosmic expansion caused by the collapse of large-scale structure. We have attempted to measure the pairwise proper motion of a small sample of quasar pairs using extant data, but lack a large enough sample to make a significant detection. We are currently obtaining proper motions for 40 pairs of quasars with the VLBA, but lack redshifts of three quasars to confirm that they are in physically close pairs. Therefore, we propose to complete our sample of 40 quasars needed to detect the collapse of large-scale structure by obtaining the redshifts of these three quasars. The quasars were previously observed on a 3.5m telescope but no spectral lines were detected. With a total time request of 10.84 hours on GMOS-N, we will be able to measure the redshifts of the objects and complete our sample of close separation pairs needed to make a "real-time," model-independent measurement of the Hubble expansion and collapse of large-scale structure.

Program Type: Standard/Extragalactic

Scheduled Nights:
Run 1 (2016B):  GEM-NQ/GMOSN -- 7hrs band 3 (GN-2016B-Q-81)


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