ULTRADEEP NEAR-INFRARED OBSERVATIONS OF GOODS 850-5

作者：Wang Wei Hao^*; Barger Amy J; Cowie Lennox L

来源：Astrophysical Journal, 2009, 690(1): 319-329.

DOI：10.1088/0004-637X/690/1/319

• cosmology: observations
• galaxies: evolution
• galaxies: formation
• galaxies: starburst
• infrared: galaxies
• submillimeter

GOODS 850-5 is a hyperluminous radio-faint submillimeter source in the Great Observatories Origins Deep Survey-North. Although it is generally agreed that GOODS 850-5 is at a high redshift, z greater than or similar to 4, its exact redshift is unknown. While its stellar spectral energy distribution ( SED) suggests z similar to 6, its radio/far-IR ( FIR) SED suggests a lower redshift of z similar to 4. To better constrain its stellar SED and redshift, we carried out nano-Jansky sensitivity ultradeep near-IR (NIR) observations between 1.2 and 2.1 mu m with the Hubble Space Telescope and the 8 m Subaru Telescope. Even with such great depths we did not detect GOODS 850-5, and the results show that it is an extremely curious source. Between the K(s) and 3.6 mu m bands, its spectral slope is greater than 3 times that of an extremely red object, and the flux ratio between the two bands is greater than 8 times that of Lyman breaks. It is quite challenging to explain this unusually red color without a Lyman break (which would imply z > 17). It requires a large amount (M(star) similar to 10(11.5) M(circle dot)) of reddened old stars at z similar to 6, coexisting with an even more extinguished violent similar to 2400-4400 M(circle dot) yr(-1) starburst, which does not have any associated detectable rest-frame UV radiation. We discuss the discrepancy between the NIR and radio/FIR photometric redshifts. We conclude that GOODS 850-5 is at least at z > 4 and is more likely at z greater than or similar to 6. We describe the unusual properties of GOODS 850-5, including its SED and formation history, and we discuss the implications of such massive z > 6 galaxies.

• 出版日期2009-1-1