Galaxy formation and evolution

Abstract:

We report the detection of four IRAC sources in the GOODS-South field with an extremely red color of H - [3.6] > 4.5. The four sources are not detected in the deep Hubble Space Telescope WFC3 H-band image with H limit = 28.3mag. We find that only three types of SED templates can produce such a red H - [3.6] color: a very dusty SED with the Calzetti extinction of AV = 16mag at z = 0.8; a very dusty SED with the SMC extinction of AV = 8mag at z = 2.0- 2.2; and an 1Gyr SSP with AV ∼0.8 at z = 5.7. We argue that these sources are unlikely dusty galaxies at z ≤ 2.2 based on absent strong MIPS 24 μm emission. The old stellar population model at z > 4.5 remains a possible solution for the 4 sources. At z > 4.5, these sources have stellar masses of log(M */M ⊙) = 10.6-11.2. One source, ERS-1, is also a type-II X-ray QSO with L 2 - 8 keV = 1.6 × 1044 erg s-1. One of the four sources is an X-ray QSO and another one is a HyperLIRG, suggesting a galaxy-merging scenario for the formation of these massive galaxies at high redshifts. © 2011. The American Astronomical Society. All rights reserved.

Abstract:

The `Eagle' galaxy at a redshift of 0.77 is studied with the Oxford Short Wavelength Integral Field Spectrograph (SWIFT) and multi-wavelength data from the All-wavelength Extended Groth strip International Survey (AEGIS). It was chosen from AEGIS because of the bright and extended emission in its slit spectrum. Three dimensional kinematic maps of the Eagle reveal a gradient in velocity dispersion which spans 35-75 +/- 10 km/s and a rotation velocity of 25 +/- 5 km/s uncorrected for inclination. Hubble Space Telescope images suggest it is close to face-on. In comparison with galaxies from AEGIS at similar redshifts, the Eagle is extremely bright and blue in the rest-frame optical, highly star-forming, dominated by unobscured star-formation, and has a low metallicity for its size. This is consistent with its selection. The Eagle is likely undergoing a major merger and is caught in the early stage of a star-burst when it has not yet experienced metal enrichment or formed the mass of dust typically found in star-forming galaxies.