Infrared Space Observatory Observations of the 53W002 Group at 6.7 Microns: In Search of the Oldest Stellar Populations at z = 2.4
Abstract
We present a deep Infrared Space Observatory (ISO) observation at 6.7 μm of the 53W002 group of galaxies and active galactic nuclei (AGNs) at z=2.4. This approximately samples the emitted K band. Faint, blue star-forming objects are not detected, as expected from their very blue color across the emitted optical and UV spectrum. However, 53W002 itself is detected at the ~3 σ level, with an emitted V-K color that is appropriate for a population that formed starting at z=3.6-7.0, most likely z=4.7. This fits with shorter wavelength data, suggesting that the more massive members of this group, which may all host AGNs, began star formation earlier in deeper potential wells than the compact Lyα emission objects. Two foreground galaxies are detected, as are several stars. One additional 6.7 μm source closely coincides with an optically faint galaxy, potentially at z=2-3. The overall source counts are consistent (within the errors of such a small sample) with the other ISO deep fields at 6.7 μm.
Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, the Netherlands, and the United Kingdom) and with the participation of ISAS and NASA.- Publication:
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Publications of the Astronomical Society of the Pacific
- Pub Date:
- August 2004
- DOI:
- 10.1086/423432
- arXiv:
- arXiv:astro-ph/0406438
- Bibcode:
- 2004PASP..116..712K
- Keywords:
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- Galaxies: High-Redshift;
- Galaxies: Evolution;
- Infrared: Galaxies;
- Astrophysics
- E-Print:
- In press, PASP (August 2004)