SPECTROSCOPIC CONFIRMATION OF TWO LYMAN BREAK GALAXIES AT REDSHIFT BEYOND 7

Journal Article · Fri Apr 01 00:00:00 EDT 2011 · Astrophysical Journal Letters

DOI:https://doi.org/10.1088/2041-8205/730/2/L35· OSTI ID:21560403

Vanzella, E; Cristiani, S ^[1]; Pentericci, L; Fontana, A; Grazian, A; Castellano, M; Boutsia, K; Gallozzi, S; Giallongo, E; Maiolino, R; Paris, D; Santini, P ^[2]; Dickinson, M ^[3]; Giavalisco, M ^[4]; Moorwood, A ^[5]

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1. INAF Osservatorio Astronomico di Trieste, Via G.B. Tiepolo 11, 34131 Trieste (Italy)
2. INAF Osservatorio Astronomico di Roma, Via Frascati 3300040, Monteporzio (Italy)
3. National Optical Astronomy Observatory, P.O. Box 26732, Tucson, AZ 85726 (United States)
4. Department of Astronomy, University of Massachusetts, 710 North Pleasant Street, Amherst, MA 01003 (United States)
5. European Southern Observatory, Karl-Schwarzschild Strasse, 85748 Garching (Germany)

We report the spectroscopic confirmation of two Lyman break galaxies at redshift >7. The galaxies were observed as part of an ultra-deep spectroscopic campaign with FORS2 at the ESO/VLT for the confirmation of z {approx_equal} 7 'z-band dropout' candidates selected from our VLT/Hawk-I imaging survey. Both galaxies show a prominent emission line at 9735 A and 9858 A, respectively: the lines have fluxes of {approx}(1.6-1.2) x 10{sup -17} erg s{sup -1} cm{sup -2} and exhibit a sharp decline on the blue side and a tail on the red side. The asymmetry is quantitatively comparable to the observed asymmetry in z {approx} 6 Ly{alpha} lines, where absorption by neutral hydrogen in the intergalactic medium (IGM) truncates the blue side of the emission-line profile. We carefully evaluate the possibility that the galaxies are instead at lower redshift and we are observing either [O II], [O III], or H{alpha} emission: however from the spectroscopic and the photometric data we conclude that there are no other plausible identifications, except for Ly{alpha} at redshift >7, implying that these are two of the most robust redshift determination for galaxies in the reionization epoch. Based on their redshifts and broadband photometry, we derive limits on the star formation rate and on the ultraviolet spectral slopes of the two galaxies. We argue that these two galaxies alone are unlikely to have ionized the IGM in their surroundings.

• OSTI ID: 21560403
• Journal Information: Astrophysical Journal Letters, Vol. 730, Issue 2; Other Information: DOI: 10.1088/2041-8205/730/2/L35; ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
EMISSION
GALAXIES
LYMAN LINES
PHOTOMETRY
RED SHIFT
ULTRAVIOLET RADIATION
ELECTROMAGNETIC RADIATION
RADIATIONS