A Hyper Extremely Red Object in the Field near 53W002

Abstract

Hyper extremely red objects (HEROs) are objects that are very red in near-IR colors (J-K>~3). They are speculated to be intrinsically red galaxies at z>~2 or Lyman break galaxies at z>10. We report the discovery of a HERO in the field that includes a known radio galaxy, 53W002, and a possible cluster of galaxies both at z=2.39. The HERO, which we name HERO J171411.91+501541.8, or 53W002-HERO1 for brevity, is visible in the Hubble Space Telescope Near-Infrared Camera and Multi-Object Spectrometer H-band data and deep K'-band data from the Subaru Telescope (K'~=21.5 mag) but not visible in B-, V-, I-, and J-band images (J-K>4.45, 2 σ). Its spectral energy distribution is consistent with that of a dusty star-forming or old galaxy at z~=2.4, which may suggest that 53W002-HERO1 is a member of the group of galaxies associated with 53W002. Alternatively, the HERO could be at z~=12.5, if its red color is due to the redshifted Lyman break. If 53W002-HERO1 is an old galaxy at z~2.4, the implied stellar age is ~2-3 Gyr, meaning that stars in the HERO formed at the reionization epoch of z>~10.