Gemini H-band imaging of the field of a z=10 candidate

摘要

We present a deep H-band image of the field of a candidate z=10 galaxymagnified by the foreground (z=0.25) cluster A1835. The image was obtained withNIRI on Gemini North to better constrain the photometry and investigate themorphology of the source. The image is approximately one magnitude deeper andhas better spatial resolution (seeing was 0.4-0.5 arcsec) than the existingH-band image obtained with ISAAC on the VLT by Pello' et al. 2004. The objectis not detected in our new data. Given the published photometry (H(AB)=25.0),we would have expected it to have been detected at more than ~7 sigma in a 1.4arcsec diameter aperture. We obtain a limit of H(AB)>26.0 (3 sigma) for theobject. A major part of the evidence that this object is at z=10 was thepresence of a strong continuum break between the J and H band, attributed toabsorption of all continuum shortward of 1216 Ang in the rest-frame of theobject. Our H-band non-detection substantially reduces the magnitude of anybreak and therefore weakens the case that this object is at z=10. Without aclear continuum break, the identification of an emission line at 1.33745um asLy-alpha at z~10 is less likely. We show that the width and flux of this lineare consistent with an alternative emission line such as [OIII]5007 from anintermediate redshift HII/dwarf galaxy.