AGN - Dust-Obscured Galaxies at z~1-3 revealed by near-to-far infrared SED-fitting

Dust-Obscured galaxies (DOGs, Dey et al. 2008) are bright 24μm-selected sources with extreme obscuration at optical wavelengths (F24μ m/FR > 982). Recent studies (Dey et al. 2008, Bussmann et al. 2009) describe an evolutionary scenario in which the starbursting nature of submillimeter galaxies (SMGs) evolves into the composite nature of DOGs as an underlying AGN grows; this is followed by a quasar phase that terminates star formation (SF), leading to the formation of a passive, massive elliptical galaxy. Within this context, DOGs could provide a key insight to an extremely dusty stage in the evolution of galaxies at z ~ 2, where both AGN and SF activity coexist.

Optical and Infrared Spectroscopy of CM Draconis

We compare observations of the binary system CM Draconis with synthetic spectra. Spectroscopic observations from 0.40 to 2.41μm, combined with photometry and the accurately known surface gravity enable us to estimate the temperature and metallicity using detailed spectra synthesis. We find discrepancies between the analysis of the infrared and optical spectrum: while the optical spectral energy distribution (SED) yields a metal-rich solution with Teff = 3000K, the infrared SED yields around 3200K and —0.8 ≤ [M/H] ≤ —0.6 compatible with the high space motion of the system. The low-metallicity characteristics of the infrared SED could be real and is partly supported by the detailed analysis of the atomic lines in the optical region. Although, the known incompleteness of the TiO and H2O line lists in the models may cause substantial systematic errors.