Star Formation and Quasar-host Galaxy Co-evolution in the Most Distant Universe

Dr. Ran Wang and her collaborators have carried out millimeter and radio observations to study the ISM properties and star forming activity in the host galaxies of quasars at the highest redshift. The team detected strong dust continuum and molecular CO line emission in about 30% of the optically bright quasars at z~6. The results indicate  huge amounts of 40 to 60 K warm dust and molecular gas in the host galaxies of these millimeter bright quasars. 


They searched for [C II] 158 micron fine structure line emission in five millimeter bright quasars at z~6 using ALMA and all of them were detected. The sources are marginally resolved and the intrinsic source sizes (major axis FWHM) are constrained to be 0.3′′ to 0.6′′ (i.e., 1.7 to 3.5 kpc) for the [C II] line emission and 0.2′′ to 0.4′′ (i.e., 1.2 to 2.3 kpc) for the continuum. These measurements indicate that there is vigorous star formation over the central few kpc in the quasar host galaxies. The ALMA observations also constrain the dynamical properties of the star-forming gas in the nuclear region. Three of the five objects show clear velocity gradients on the line intensity-weighted velocity maps. Such velocity gradients are consistent with a rotating, gravitationally bound gas component, although they are not uniquely interpreted as such. These observations set important constraints on the supermassive black hole and galaxy co-evolution at the earliest epoch. The results have been published in Wang et al. 2013, ApJ, 773, 44.


Collaborators : Carilli, C. (NRAO); Walter, F. (MPIfA); Fan, X. (Steward); Wagg, J. (NRAO); Neri, R. (IRAM); Bertoldi, F. (University of Bonn); Riechers, D. (Cornell); Omont, A. (IAP); Strauss, M. (Princeton); Cox, P. (IRAM); Menten, K. (MPIfR); Narayanan, D. (Steward); Jiang, L. (ASU)


Figure -- The PdBI detection of CO (6-5) line (bottom) and ALMA images of the dust continuum (top-lepf), 

[C II] line intensity (top-middle) and velocity distribution (top-right) of one of the millimeter bright 


quasars, J2310+1855 at z=6.00 (Wang et al. 2013, ApJ, 773, 44).