We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of the [C II] 158 µm fine structure line and dust continuum emission from the host galaxies of five redshift 6 quasars. We also report complementary observations of 250 GHz dust continuum and CO (6-5) line emission from the z=6.00 quasar SDSS J231038.88+185519.7 using the IRAM facilities. The ALMA observations were carried out in the extended array at 0. −4 , which is comparable to the values found in other high-redshift quasar-starburst systems and local ultra-luminous infrared galaxies. 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. The intensity-weighted velocity maps of three sources show clear velocity gradients. Such velocity gradients are consistent with a rotating, gravitationally bound gas component, although they are not uniquely interpreted as such. Under the simplifying assumption of rotation, the implied dynamical masses within the [C II]-emitting regions are of order 10 10 to 10 11 M ⊙ . Given these estimates, the mass ratios between the SMBHs and the spheroidal bulge are an order of magnitude higher than the mean value found in local spheroidal galaxies, which is in agreement with results from previous CO observations of high redshift quasars.

We make use of deep 1.2 mm-continuum observations (12.7µJy/beam RMS) of a 1 arcmin 2 region in the Hubble Ultra Deep Field (HUDF) to probe dust-enshrouded star formation from 330 Lyman-break galaxies spanning the redshift range z = 2-10 (to ∼2-3 M ⊙ /yr at 1σ over the entire range). Given the depth and area of ASPECS, we would expect to tentatively detect 35 galaxies extrapolating the Meurer z ∼ 0 IRX-β relation to z ≥ 2 (assuming T d ∼ 35 K). However, only 6 tentative detections are found at z 2 in ASPECS, with just three at >3σ. Subdividing z = 2-10 galaxies according to stellar mass, U V luminosity, and U V -continuum slope and stacking the results, we only find a significant detection in the most massive (>10 9.75 M ⊙ ) subsample, with an infrared excess (IRX=L IR /L UV ) consistent with previous z ∼ 2 results. However, the infrared excess we measure from our large selection of sub-L * (<10 9.75 M ⊙ ) galaxies is 0.11 +0.32 −0.42 ±0.34 (bootstrap and formal uncertainties) and 0.14 +0.15 −0.14 ±0.18 at z = 2-3 and z = 4-10, respectively, lying below even an SMC IRX-β relation (95% confidence). These results demonstrate the relevance of stellar mass for predicting the IR luminosity of z 2 galaxies. We find that the evolution of the IRX-stellar mass relationship depends on the evolution of the dust temperature. If the dust temperature increases monotonically with redshift (∝ (1 + z) 0.32 ) such that T d ∼ 44-50 K at z ≥ 4, current results are suggestive of little evolution in this relationship to z ∼ 6. We use these results to revisit recent estimates of the z ≥ 3 star-formation rate density.

We report the detection of the CO 4-3, 6-5, 9-8, 10-9, and 11-10 lines in the Broad Absorption Line quasar APM 08279+5255 at z = 3.9 using the IRAM 30 m telescope. We also present IRAM PdBI high spatial resolution observations of the CO 4-3 and 9-8 lines, and of the 1.4 mm dust radiation as well as an improved spectrum of the HCN(5-4) line. Unlike CO in other QSO host galaxies, the CO line SED of APM 08279+5255 rises up to the CO(10-9) transition. The line fluxes in the CO ladder and the dust continuum fluxes are best fit by a two component model, a "cold" component at ∼65 K with a high density of n(H 2 ) = 1 × 10 5 cm −3 , and a "warm", ∼220 K component with a density of 1 × 10 4 cm −3 . We show that IR pumping via the 14 µm bending mode of HCN is the most likely channel for the HCN excitation. From our models we find, that the CO(1-0) emission is dominated by the dense gas component which implies that the CO conversion factor is higher than usually assumed for high-z galaxies with α ≈ 5 M (K km s −1 pc 2 ) −1 . Using brightness temperature arguments, the results from our high-resolution mapping, and lens models from the literature, we argue that the molecular lines and the dust continuum emission arise from a very compact (r ≈ 100−300 pc), highly gravitationally magnified (m = 60−110) region surrounding the central AGN. Part of the difference relative to other high-z QSOs may therefore be due to the configuration of the gravitational lens, which gives us a high-magnification zoom right into the central 200-pc radius of APM 08279+5255 where IR pumping plays a significant role for the excitation of the molecular lines.

We report our new observations of redshifted carbon monoxide emission from six z∼6 quasars, using the IRAM Plateau de Bure Interferometer. or (5-4) line emission was detected in all six sources. Together with two other previous CO detections, these observations provide unique constraints on the molecular gas emission properties in these quasar systems close to the end of the cosmic reionization. Complementary results are also presented for low-J CO lines observed at the Green Bank Telescope and the Very Large Array, and dust continuum from five of these sources with the SHARC-II bolometer camera at the Caltech Submillimeter Observatory. We then present a study of the molecular gas properties in our combined sample of eight CO-detected quasars at z∼6. The detections of high-order CO line emission in these objects indicates the presence of highly excited molecular gas, with estimated masses on the order of 10 10 M ⊙ within the quasar host galaxies. No significant difference is found in the gas mass and CO line width distributions between our z ∼ 6 quasars and samples of CO-detected 1.4 ≤ z ≤ 5 quasars and submillimeter galaxies. Most of the 11 Hubble Fellow -2 -CO-detected quasars at z∼6 follow the far infrared-CO luminosity relationship defined by actively star-forming galaxies at low and high redshifts. This suggests that ongoing star formation in their hosts contributes significantly to the dust heating at FIR wavelengths. The result is consistent with the picture of galaxy formation co-eval with supermassive black hole (SMBH) accretion in the earliest quasar-host systems. We investigate the black hole-bulge relationships of our quasar sample, using the CO dynamics as a tracer for the dynamical mass of the quasar host. The median estimated black hole-bulge mass ratio is about fifteen times higher than the present-day value of ∼0.0014. This places important constraints on the formation and evolution of the most massive SMBH-spheroidal host systems at the highest redshift.