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Published September 2006 | Published
Journal Article Open

Spitzer Observations of the Prototypical Extremely Red Objects HR 10 and LBDS 53W091: Separating Dusty Starbursts from Old Elliptical Galaxies


We present Spitzer Space Telescope observations of the well-studied extremely red objects (EROs) HR 10 and LBDS 53W091 from 3.6 to 160 μm. These galaxies are the prototypes of the two primary classes of EROs: dusty starbursts and old, evolved galaxies, respectively. Both galaxies, as well as LBDS 53W069, another example of an old, quiescent galaxy, are well detected out to 8 μm. However, only the dusty starburst HR 10 is detected in the far-infrared. All three EROs have stellar masses of a few × 10^(11) M_☉. Using evolutionary model fits to their multiband photometry, we predict the infrared colors of similar EROs at 1 < z < 2. We find that blueward of observed 10 μm, the two ERO classes are virtually indistinguishable photometrically. Deep spectroscopy and 24 μm data allow the classes to be separated.

Additional Information

© 2006 American Astronomical Society. Received 2005 December 22; accepted 2006 May 21. This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under a NASA contract. Support was provided by NASA through an award issued by JPL/Caltech.

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August 22, 2023
October 23, 2023