CO (4-3) and dust emission in two powerful high-z radio galaxies, and CO lines at high redshifts

We report the detection of submillimeter emission from dust at 850 mu m and of the (12)CO J = 4-3 line in the two distant powerful radio galaxies 4C 60.07 (z = 3.79) and 6C 1909 + 722 (z = 3.53). Tn 4C 60.07, the dust emission is also detected at 1.25 mm. The estimated molecular gas masses are large, of the order of similar to(0.5-1)x 10(11) M. The large far-infrared (FIR) luminosities (L(FIR) similar to 10(13) L.) suggest that we are witnessing two major starburst phenomena, while the observed large velocity widths (Delta V(FWHM) greater than or similar to 500 km s(-1)) are characteristic of mergers. In the case of 4C 60.07, the CO emission extends over similar to 30 kpc and spans a velocity range of greater than or similar to 1000 lim s(-1). It consists of two distinct features with FWHM of greater than or similar to 550 km s(-1) and similar to 150 km s(-1), and line centers separated by greater than or similar to 700 km s(-1). The least massive of these components is probably very gas rich, with potentially greater than or similar to 60% of its dynamical mass in the form of molecular gas. The extraordinary morphology of the CO emission in this object suggests that it is not just a scaled-up version of a local ultraluminous infrared galaxy, and it may be a formative stage of the elliptical host of the residing radio-loud active galactic nucleus (AGN). Finally, we briefly explore the effects of the wide range of gas-excitation conditions expected for starburst environments on the luminosity of high-J CO lines and conclude that in unlensed objects, CO (J + 1 --> J), J + 1 > 3 lines can be significantly weak with respect to CO J = 1-0, and this can hinder their detection even in the presence of substantial molecular gas masses.