The Grism Lens-Amplified Survey from space (GLASS). III. A census of Lyα emission at z≳7 from HST spectroscopy

Journal Article · Wed Feb 10 04:00:00 EST 2016 · Astrophysical Journal

DOI:https://doi.org/10.3847/0004-637X/818/1/38· OSTI ID:22887055

Schmidt, K. B.; Jones, T. A.; Mason, C.; Wang, X. ^[1]; Treu, T. ^[2]; Bradač, M.; Huang, K. -H.; Hoag, A. ^[3]; Vulcani, B. ^[4]; Maseda, M. ^[5]; Guaita, L.; Pentericci, L.; Fontana, A. ^[6]; Brammer, G. B. ^[7]; Dijkstra, M. ^[8]; Dressler, A. ^[9]; Henry, A. L. ^[10]

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1. Department of Physics, University of California, Santa Barbara, CA 93106-9530 (United States)
2. Department of Physics and Astronomy, UCLA, Los Angeles, CA 90095-1547 (United States)
3. Department of Physics, University of California, Davis, CA 95616 (United States)
4. Kavli Institute for the Physics and Mathematics of the Universe (WPI), Todai Institutes for Advanced Study, the University of Tokyo, Kashiwa 277-8582 (Japan)
5. Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany)
6. INAF—Osservatorio Astronomico di Roma Via Frascati 33—I-00040 Monte Porzio Catone (Italy)
7. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
8. Institute of Theoretical Astrophysics, University of Oslo, Postboks 1029, NO-0858 Oslo (Norway)
9. The Observatories of the Carnegie Institution for Science, 813 Santa Barbara St., Pasadena, CA 91101 (United States)
10. Astrophysics Science Division, Goddard Space Flight Center, Code 665, Greenbelt, MD 20771 (United States)

We present a census of Lyα emission at z≳7, utilizing deep near-infrared Hubble Space Telescope grism spectroscopy from the first six completed clusters of the Grism Lens-Amplified Survey from Space (GLASS). In 24/159 photometrically selected galaxies we detect emission lines consistent with Lyα in the GLASS spectra. Based on the distribution of signal-to-noise ratios and on simulations, we expect the completeness and the purity of the sample to be 40%–100% and 60%–90%, respectively. For the objects without detected emission lines we show that the observed (not corrected for lensing magnification) 1σ flux limits reach 5 × 10{sup −18} erg s{sup −1} cm{sup −2} per position angle over the full wavelength range of GLASS (0.8–1.7 μm). Based on the conditional probability of Lyα emission measured from the ground at z∼7, we would have expected 12–18 Lyα emitters. This is consistent with the number of detections, within the uncertainties, confirming the drop in Lyα emission with respect to z∼6. Deeper follow-up spectroscopy, here exemplified by Keck spectroscopy, is necessary to improve our estimates of completeness and purity and to confirm individual candidates as true Lyα emitters. These candidates include a promising source at z = 8.1. The spatial extent of Lyα in a deep stack of the most convincing Lyα emitters with 〈z〉 = 7.2 is consistent with that of the rest-frame UV continuum. Extended Lyα emission, if present, has a surface brightness below our detection limit, consistent with the properties of lower-redshift comparison samples. From the stack we estimate upper limits on rest-frame UV emission line ratios and find f{sub CIV}/f{sub Lyα}≲0.32 and f{sub CIII]}/f{sub Lyα}≲0.23, in good agreement with other values published in the literature.

• OSTI ID: 22887055
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 818; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United Kingdom
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
BRIGHTNESS
COMPARATIVE EVALUATIONS
COMPUTERIZED SIMULATION
DATA ANALYSIS
DETECTION
DISTRIBUTION
EMISSION
GALAXIES
GRAVITATIONAL LENSES
LYMAN LINES
PROBABILITY
RED SHIFT
SIGNAL-TO-NOISE RATIO
SPACE
SPECTRA
SPECTROSCOPY
TELESCOPES