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 (CO)-C-12 J = 4-3 line in the two distant powerful radio galaxies 4 C 60.07 (z = 3.79) and 6C 1909 + 722 (z = 3.53). Tn 4C 60.07, the dust emis sion is also detected at 1.25 mm. The estimated molecular gas masses are la rge, of the order of similar to(0.5-1)x 10(11) M. The large far-infrared (F IR) luminosities (L-FIR similar to 10(13) L.) suggest that we are witnessin g 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 simi lar 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 com ponents is probably very gas rich, with potentially greater than or similar to 60% of its dynamical mass in the form of molecular gas. The extraordina ry morphology of the CO emission in this object suggests that it is not jus t 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 acti ve galactic nucleus (AGN). Finally, we briefly explore the effects of the w ide 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 t o CO J = 1-0, and this can hinder their detection even in the presence of s ubstantial molecular gas masses.