NOAO >   Observing Info >   Approved Programs >   2009B-0532

# Proposal Information for 2009B-0532

PI: Yujin Yang, University of Arizona, yyang@as.arizona.edu
Address: Steward Observatory, 933 N Cherry Ave, Tucson, AZ 85721, USA

CoI: Ann Zabludoff, University of Arizona
CoI: Romeel Dave', University of Arizona
CoI: Daniel Eisenstein, University of Arizona

Title: Galaxy Formation in Action: Resolving the Nature of Newly Discovered Lyman-(alpha) Blobs in the Chandra Deep Field South

Abstract: At early times, galaxies grow significantly via the accretion of gas from the surrounding intergalactic medium. Yet galaxy formation via gas accretion has not been observed. The best candidates for gas-accreting forming galaxies are extended \lya sources, the so-called \lya blobs. However, it is impossible to determine whether gas infall is actually taking place due to the ambiguities in interpreting their optically thick \lya line. As a result, studies of the same \lya blob kinematics have led to radically different conclusions, suggesting that gas is indeed inflowing, outflowing in stellar or AGN winds, or even static. We have undertaken a program to resolve this ambiguity by detecting blobs in a blind, large-volume survey at a redshift (z ~ 2.3) chosen to allow comparison of their \lya \it and H(alpha) emission line centers. Despite the complexity of various blob models, \it all gas accretion scenarios predict that the optically thick \lya\ line will be blue-shifted with respect to the optically thin H(alpha) line, whereas outflows will redshift the line. \bf Using VLT/SINFONI/IFU visitor time, we have now made the first detection of H(alpha) lines from embedded galaxies in three \lya blobs. The \lya\ line in the brightest blob is blue-shifted relative to H(alpha), implying gas infall. Here we propose to obtain GMOS integral field \lya spectroscopy of this and our second-brightest blob to determine if there are infall signatures throughout the blob, instead of just in the one line-of-sight probed by our short-slit" \lya spectrum. This proposal is a resubmission - no time was awarded last semester because the TAC questioned the detectability of the H(alpha) line. We have now detected H(alpha).

National Optical Astronomy Observatory, 950 North Cherry Avenue, P.O. Box 26732, Tucson, Arizona 85726, Phone: (520) 318-8000, Fax: (520) 318-8360

 NOAO >   Observing Info >   Approved Programs >   2009B-0532