Tracing the reionization epoch with ALMA: [C ii] emission in z ∼ 7 galaxies

Journal Article · Tue Sep 20 04:00:00 EDT 2016 · Astrophysical Journal Letters

DOI:https://doi.org/10.3847/2041-8205/829/1/L11· OSTI ID:22868681

Pentericci, L.; Castellano, M.; Fontana, A.; Guaita, L.; Grazian, A.; Santini, P. ^[1]; Carniani, S.; Maiolino, R. ^[2]; Vanzella, E. ^[3]; Yan, H. ^[4]; Cristiani, S. ^[5]; Conselice, C. ^[6]; Giavalisco, M. ^[7]; Hathi, N. ^[8]; Koekemoer, A. ^[9]

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1. INAF, Osservatorio Astronomico di Roma, via Frascati 33, I-00040 Monteporzio (Italy)
2. Kavli Institute for Cosmology, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom)
3. INAF, Osservatorio Astronomico di Bologna, via Ranzani 1, I-40127 Bologna (Italy)
4. Department of Physics and Astronomy, University of Missouri, Columbia, MO (United States)
5. INAF, Osservatorio Astronomico di Trieste, Via G. B. Tiepolo, 11, I-34143 Trieste (Italy)
6. University of Nottingham, School of Physics and Astronomy, Nottingham NG7 2RD (United Kingdom)
7. Astronomy Department, University of Massachusetts, Amherst, MA 01003 (United States)
8. Aix Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) (France)
9. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21208 (United States)

We present new results on [C ii]158 μm emission from four galaxies in the reionization epoch. These galaxies were previously confirmed to be at redshifts between 6.6 and 7.15 from the presence of the Lyα emission line in their spectra. The Lyα emission line is redshifted by 100–200 km s{sup −1} compared to the systemic redshift given by the [C ii] line. These velocity offsets are smaller than what is observed in z∼3 Lyman break galaxies (LBGs) with similar UV luminosities and emission line properties. Smaller velocity shifts reduce the visibility of Lyα and hence somewhat alleviate the need for a very neutral intergalactic medium at z∼7 to explain the drop in the fraction of Lyα emitters observed at this epoch. The galaxies show [C ii] emission with L[C ii] = 0.6 − 1.6×10{sup 8}L{sub ⊙}: these luminosities place them consistently below the star formation rate (SFR)–L[C ii] relation observed for low-redshift star-forming and metal-poor galaxies and also below z = 5.5 LBGs with similar SFRs. We argue that previous undetections of [C ii] in z∼7 galaxies with similar or smaller SFRs are due to selection effects: previous targets were mostly strong Lyα emitters and therefore probably metal-poor systems, while our galaxies are more representative of the general high-redshift star-forming population.

• OSTI ID: 22868681
• Journal Information: Astrophysical Journal Letters, Journal Name: Astrophysical Journal Letters Journal Issue: 1 Vol. 829; ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
GALACTIC EVOLUTION
GALAXIES
IONIZATION
LUMINOSITY
METALS
RED SHIFT
STARS
VELOCITY