Chun Xu et al. 2007 The Astronomical Journal 134 169 doi:10.1086/513512
Redshifts of Emission-Line Objects in the Hubble Ultra Deep Field
FREE ISSUEChun Xu1, Norbert Pirzkal1, Sangeeta Malhotra1,2, James E. Rhoads1,2, Bahram Mobasher1, Emanuele Daddi3, Caryl Gronwall4, Nimish P. Hathi5, Nino Panagia1, Henry C. Ferguson1, Anton M. Koekemoer1, Martin Kümmel6, Leonidas A. Moustakas1, Anna Pasquali7, Sperello di Serego Alighieri8, Joel Vernet8, Jeremy R. Walsh6, Rogier Windhorst2 and Haojing Yan9
Show affiliationsWe present redshifts for 115 emission-line objects in the Hubble Ultra Deep Field identified through the Grism ACS Program for Extragalactic Science (GRAPES) project using the slitless grism spectroscopy mode of the Advanced Camera for Surveys on the Hubble Space Telescope (HST). The sample was selected by an emission-line search on all extracted one-dimensional GRAPES spectra. We identify the emission lines using line wavelength ratios where multiple lines are detected in the grism wavelength range (5800 Å 
λ 9600 Å), and using photometric redshift information where multiple lines are unavailable. We then derive redshifts using the identified lines. Our redshifts are accurate to δz ≈ 0.009, based on both statistical uncertainty estimates and comparison with published ground-based spectra. Over 40% of our sample is fainter than typical magnitude limits for ground-based spectroscopy (with iAB > 25 mag). Such emission lines would likely remain undiscovered without our deep survey. The emission-line objects fall into three categories: (1) most are low- to moderate-redshift galaxies (0 ≤ z ≤ 2), including many actively star-forming galaxies with strong H II regions; (2) nine are high-redshift (4 ≤ z ≤ 7) Lyα emitters; and (3) at least three are candidate active galactic nuclei.
- Keywords
galaxies: formation; galaxies: high-redshift; galaxies: starburst
- Dates
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Issue 1 (2007 July)
Received 2006 April 19, accepted for publication 2006 December 22
Published 2007 May 17
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Redshifts of Emission-Line Objects in the Hubble Ultra Deep Field
Chun Xu et al. 2007 The Astronomical Journal 134 169