NOAO >   Observing Info >   Approved Programs >   2017A-0366

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Program Information for 2017A-0366


PI: Sangeeta Malhotra, Arizona State U., sangeeta.malhotra@asu.edu
Address: School of Earth and Space Exploration, PO Box 871404, Tempe, AZ 85287-1404 USA

CoI: Zhenya Zheng, Pontificia Universidad Catolica de Chile
CoI: James Rhoads, Arizona State U.
CoI: Junxian Wang, University of Science & Technology of China
CoI: Alistair Walker, CTIO
CoI: Leopoldo Infante, Pontificia Universidad Catolica de Chile
CoI: Linhua Jiang, Peking University
CoI: Chunyan Jiang, SHAO
CoI: Weida Hu, University of Science & Technology of China
CoI: Pascale Hibon, ESO
CoI: Alicia Gonzalez, Arizona State U.

Title: Lyman Alpha Galaxies in the Epoch of Reionization (LAGER)

Abstract: underline{it Science background:/ }The scattering of lya photons by neutral intergalactic medium (IGM) leads to an apparent decline in the characteristic luminosity of lya galaxies, providing a powerful test of reionization. In the first application of this method, Malhotra & Rhoads (2004) saw no such decline at $z=6.5$, concluding that the IGM is mostly ionized at z=6.5. Since then hundreds of LAEs have been efficiently detected with deep narrowband surveys up to z = 6.5, but are largely missing at $zgtrsim 7$. Is the decline of lya galaxies at $z gtrsim 7$ due to neutral IGM, or a decline in CCD sensitivities at 1 micron, or a change in intrinsic properties of lya galaxies? To answer these questions we need robust statistical samples of lya galaxies at $zsim 7$ at low and high luminosities. underline{it LAGER survey:/ }To address the scarcity of lya emitters at $zsim 7$ we started a definitive narrowband LAE survey project at $zsim 7$--- Lyman Alpha Galaxies in the Epoch of Reionization (LAGER). This survey exploits DECam's uniquely large FOV and QE in the near-infrared. We have fabricated and tested a custom filter at 9640 AA for DECAM and obtained deep narrowband imaging in one field (COSMOS). The first 26 high confidence $zsim 7$ LAE candidates have been selected, plus one lya Blob candidate, which, if confirmed, will break redshift and luminosity records. The new lya LF at $zsim 7$ implies an average IGM neutral fraction x(HI) $sim$ 50%. Spectroscopic followup of the blob and lya emitters are ongoing. We also find 700 H$alpha$ line emitters at z=0.46 and 1300 [OIII] emitters at z=0.9, which should be extremely useful for planning of BigBOSS, Euclid, and WFIRST surveys. underline{it In this proposal:/ }We request time to image a second field to our full survey depth. This will double the number of LAGER $zsim 7$ LAEs,which is important for the determination of the bright end of the luminosity function, but more importantly, it will give an independent estimate of the neutral fraction of the IGM in an independent field. Many models predict large inhomogenieties in the neutral fraction and ionized bubbles halfway through reionization, making a second field essential for robust results. We need 6 nights, 3 of which will be requested from the Chilean TAC.

Program Type: Standard/Extragalactic

Scheduled Nights:
Run 1 (2017A):  CT-4m/DECam -- 3n on May 24 - May 26 2017


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 >   2017A-0366

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