Spectroscopy of luminous z>7 galaxy candidates and sources of contamination in z>7 galaxy searches

Understand

We present three bright z+ dropout candidates selected from deep Near-Infrared (NIR) imaging of the COSMOS 2 square degree field.

• All three objects match the 0.8-8um colors of other published z>7 candidates but are three magnitudes brighter, facilitating further study.
• Deep spectroscopy of two of the candidates covering 0.64-1.02um with Keck-DEIMOS and all three covering 0.94-1.10um and 1.52-1.80um with Keck-NIRSPEC detects weak spectral features tentatively identified as Ly-alpha at z=6.95 and z=7.69 in two of the objects.
• The third object is placed at z~1.6 based on a 24um and weak optical detection.