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arXiv · 1302.7005

A Lyman Break Galaxy in the Epoch of Reionization from HST Grism Spectroscopy

James E. Rhoads·Sangeeta Malhotra·Daniel Stern·Mark Dickinson·Norbert Pirzkal·Hyron Spinrad·Naveen Reddy·Nimish Hathi·Norman Grogin·Anton Koekemoer·Michael A. Peth·Seth Cohen·Zhenya Zheng·Tamas Budavari·Ignacio Ferreras·Jonathan Gardner·Caryl Gronwall·Zoltan Haiman·Gerhardt Meurer·Leonidas Moustakas·Nino Panagia·Anna Pasquali·Kailash Sahu·Sperello di Serego Alighieri·Amber Straughn·Rachel Somerville·Jeremy Walsh·Rogier Windhorst·Chun Xu·Haojing Yan
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Abstract

We present observations of a luminous galaxy at redshift z=6.573 --- the end of the reioinization epoch --- which has been spectroscopically confirmed twice. The first spectroscopic confirmation comes from slitless HST ACS grism spectra from the PEARS survey (Probing Evolution And Reionization Spectroscopically), which show a dramatic continuum break in the spectrum at restframe 1216 A wavelength. The second confirmation is done with Keck + DEIMOS. The continuum is not clearly detected with ground-based spectra, but high wavelength resolution enables the Lyman alpha emission line profile to be determined. We compare the line profile to composite line profiles at redshift z=4.5. The Lyman alpha line profile shows no signature of a damping wing attenuation, confirming that the intergalactic gas is ionized at redshift z=6.57. Spectra of Lyman breaks at yet higher redshifts will be possible using comparably deep observations with IR-sensitive grisms, even at redshifts where Lyman alpha is too attenuated by the neutral IGM to be detectable using traditional spectroscopy from the ground.

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James E. Rhoads, Sangeeta Malhotra, Daniel Stern, Mark Dickinson, Norbert Pirzkal, Hyron Spinrad, Naveen Reddy, Nimish Hathi, Norman Grogin, Anton Koekemoer, Michael A. Peth, Seth Cohen, Zhenya Zheng, Tamas Budavari, Ignacio Ferreras, Jonathan Gardner, Caryl Gronwall, Zoltan Haiman, Gerhardt Meurer, Leonidas Moustakas, Nino Panagia, Anna Pasquali, Kailash Sahu, Sperello di Serego Alighieri, Amber Straughn, Rachel Somerville, Jeremy Walsh, Rogier Windhorst, Chun Xu, Haojing Yan. 2013-02-27. A Lyman Break Galaxy in the Epoch of Reionization from HST Grism Spectroscopy. https://doi.org/10.1088/0004-637x/773/1/32

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