ALBERT

Description: We present Karl G. Jansky Very Large Array (VLA) observations of the CO ( J  = 2 -〉 1) line emission towards the z  = 6.419 quasar SDSS J114816.64 + 525150.3 (J1148 + 5251). The molecular gas is found to be marginally resolved with a major axis of 0.9 arcsec (consistent with previous size measurements of the CO ( J  = 7 -〉 6) emission). We observe tentative evidence for extended line emission towards the south-west on a scale of ~1.4 arcsec, but this is only detected at 3.3 significance and should be confirmed. The position of the molecular emission region is in excellent agreement with previous detections of low-frequency radio continuum emission as well as [C  ii ] line and thermal dust continuum emission. These CO ( J  = 2 -〉 1) observations provide an anchor for the low-excitation part of the molecular line spectral energy distribution. We find no evidence for extended low-excitation component, neither in the spectral line energy distribution nor the image. We fit a single kinetic gas temperature model of 50 K. We revisit the gas and dynamical masses in light of this new detection of a low-order transition of CO, and confirm previous findings that there is no extended reservoir of cold molecular gas in J1148 + 5251, and that the source departs substantially from the low- z relationship between black hole mass and bulge mass. Hence, the characteristics of J1148 + 5251 at z  = 6.419 are very similar to z  ~ 2 quasars, in the lack of a diffuse cold gas reservoir and kpc-size compactness of the star-forming region.

Description: We present Karl G. Jansky Very Large Array (VLA) observations of the CO ( J  = 2 -〉 1) line emission towards the z  = 6.419 quasar SDSS J114816.64 + 525150.3 (J1148 + 5251). The molecular gas is found to be marginally resolved with a major axis of 0.9 arcsec (consistent with previous size measurements of the CO ( J  = 7 -〉 6) emission). We observe tentative evidence for extended line emission towards the south-west on a scale of ~1.4 arcsec, but this is only detected at 3.3 significance and should be confirmed. The position of the molecular emission region is in excellent agreement with previous detections of low-frequency radio continuum emission as well as [C  ii ] line and thermal dust continuum emission. These CO ( J  = 2 -〉 1) observations provide an anchor for the low-excitation part of the molecular line spectral energy distribution. We find no evidence for extended low-excitation component, neither in the spectral line energy distribution nor the image. We fit a single kinetic gas temperature model of 50 K. We revisit the gas and dynamical masses in light of this new detection of a low-order transition of CO, and confirm previous findings that there is no extended reservoir of cold molecular gas in J1148 + 5251, and that the source departs substantially from the low- z relationship between black hole mass and bulge mass. Hence, the characteristics of J1148 + 5251 at z  = 6.419 are very similar to z  ~ 2 quasars, in the lack of a diffuse cold gas reservoir and kpc-size compactness of the star-forming region.

Description: We present ALLSMOG, the APEX Low-redshift Legacy Survey for MOlecular Gas. ALLSMOG is a survey designed to observe the CO(2 – 1) emission line with the APEX telescope, in a sample of local galaxies (0.01 〈  z  〈 0.03), with stellar masses in the range 8.5 〈 log(M * /M ) 〈 10. This paper is a data release and initial analysis of the first two semesters of observations, consisting of 42 galaxies observed in CO(2 – 1). By combining these new CO(2 – 1) emission line data with archival H  i data and SDSS optical spectroscopy, we compile a sample of low-mass galaxies with well-defined molecular gas masses, atomic gas masses, and gas-phase metallicities. We explore scaling relations of gas fraction and gas consumption time-scale, and test the extent to which our findings are dependent on a varying CO/H 2 conversion factor. We find an increase in the H 2 /H  i mass ratio with stellar mass which closely matches semi-analytic predictions. We find a mean molecular gas fraction for ALLSMOG galaxies of M H2 / M * = (0.09–0.13), which decreases with stellar mass. This decrease in total gas fraction with stellar mass is in excess of some model predictions at low stellar masses. We measure a mean molecular gas consumption time-scale for ALLSMOG galaxies of 0.4–0.7 Gyr. We also confirm the non-universality of the molecular gas consumption time-scale, which varies (with stellar mass) from ~100 Myr to ~2 Gyr. Importantly, we find that the trends in the H 2 /H  i mass ratio, gas fraction, and the non-universal molecular gas consumption time-scale are all robust to a range of recent metallicity-dependent CO/H 2 conversion factors.

Description: We use sensitive observations of three high-redshift sources: [C  ii ] $^2\text{P}_{3/2}$ -〉 $^2\text{P}_{1/2}$ fine-structure and CO ( J = 2 -〉 1) rotational transitions for the z  = 6.4 quasar (QSO) host galaxy J1148+5251 taken with the Plateau de Bure Interferometer (PdBI) and Jansky Very Large Array, respectively, and [C  ii ] and CO ( J = 5 -〉 4) transitions from the QSO BR1202–0725 and its companion sub-millimetre galaxy (SMG) at z  = 4.7 taken with the Atacama Large Millimeter Array and the PdBI. We use these observations to place constraints on the quantity $\Delta z = z_{\rm CO} - z_{\text{C}{\,\small {ii}}}$ for each source where z CO and $z_{\text{C}{\,\small {ii}}}$ are the observed redshifts of the CO rotational transition and [C  ii ] fine-structure transition, respectively, using a combination of approaches: (1) modelling the emission line profiles using ‘shapelets’ – a complete orthonormal set of basis functions that allow us to recreate most physical line shapes – to compare both the emission redshifts and the line profiles themselves, in order to make inferences about the intrinsic velocity differences between the molecular and atomic gas, and (2) performing a marginalization over all model parameters in order to calculate a non-parametric estimate of z . We derive 99 per cent confidence intervals for the marginalized posterior of z of (–1.9 ± 1.3)  x 10 –3 , (–3 ± 8)  x 10 –4 and (–2 ± 4)  x 10 –3 for J1148+5251, and the BR1202–0725 QSO and SMG, respectively. We show that the [C  ii ] and CO ( J = 2 -〉 1) line profiles for J1148+5251 are consistent with each other within the limits of the data, whilst the [C  ii ] and CO ( J = 5 -〉 4) line profiles from the BR1202–0725 QSO and SMG, respectively, have 65 and 〉99.9 per cent probabilities of being inconsistent, with the CO ( J = 5 -〉 4) lines ~30 per cent wider than the [C  ii ] lines. Therefore, whilst the observed values of z can correspond to variations in the quantity F / F with cosmic time, where F  = α 2 /μ, with α the fine-structure constant and μ the proton-to-electron mass ratio, of both (–3.3 ± 2.3)  x 10 –4 for a look-back time of 12.9 Gyr and of (–5 ± 15)  x 10 –5 for a look-back time of 12.4 Gyr, we propose that they are the result of the two species of gas being spatially separated as indicated by the inconsistencies in their line profiles.

Description: We present ALMA observations of cold dust and molecular gas in four high-luminosity, heavily reddened ( A V ~ 2.5–6 mag) type 1 quasars at z ~ 2.5 with virial M BH ~ 10 10  M , to test whether dusty, massive quasars represent the evolutionary link between submillimetre-bright galaxies and unobscured quasars. All four quasars are detected in both the dust continuum and in the 12 CO(3-2) line. The mean dust mass is 6 x 10 8  M assuming a typical high-redshift quasar spectral energy distribution ( T = 41 K, β = 1.95 or T = 47 K, β = 1.6). The implied star formation rates are very high – 1000 M  yr –1 in all cases. Gas masses estimated from the CO line luminosities cover ~1–5 x 10 10 (α CO /0.8)M and the gas depletion time-scales are very short – ~5–20 Myr. A range of gas-to-dust ratios is observed in the sample. We resolve the molecular gas in one quasar – ULASJ2315+0143 ( z = 2.561) – which shows a strong velocity gradient over ~20 kpc. The velocity field is consistent with a rotationally supported gas disc but other scenarios, e.g. mergers, cannot be ruled out at the current resolution of these data. In another quasar – ULASJ1234+0907 ( z = 2.503) – we detected molecular line emission from two millimetre-bright galaxies within 200 kpc of the quasar, suggesting that this quasar resides in a significant overdensity. The high detection rate of both cold dust and molecular gas in these sources, suggests that reddened quasars could correspond to an early phase in massive galaxy formation associated with large gas reservoirs and significant star formation.

Description: We present detections of the CO( J  = 1–0) emission line in a sample of four massive star-forming galaxies at z ~ 1.5–2.2 obtained with the Karl G. Jansky Very Large Array. Combining these observations with previous CO(2–1) and CO(3–2) detections of these galaxies, we study the excitation properties of the molecular gas in our sample sources. We find an average line brightness temperature ratios of R 21  = 0.70 ± 0.16 and R 31  = 0.50 ± 0.29, based on measurements for three and two galaxies, respectively. These results provide additional support to previous indications of sub-thermal gas excitation for the CO(3–2) line with a typically assumed line ratio R 31 ~ 0.5. For one of our targets, BzK-21000, we present spatially resolved CO line maps. At the resolution of 0.18 arcsec (1.5 kpc), most of the emission is resolved out except for some clumpy structure. From this, we attempt to identify molecular gas clumps in the data cube, finding four possible candidates. We estimate that 〈40 per cent of the molecular gas is confined to giant clumps (~1.5 kpc in size), and thus most of the gas could be distributed in small fainter clouds or in fairly diffuse extended regions of lower brightness temperatures than our sensitivity limit.

Description: We report optical spectroscopy from the Very Large Telescope/FOcal Reducer and low dispersion spectroscopy of the two Lyα emitters (LAEs) companions to the quasi-stellar object–sub-millimetre galaxy system BRI1202-0725 at z  = 4.7, which have recently been detected in the [C ii ]158 μm line by the Atacama Large Millimetre/Sub-millimetre Array. We detect Lyα emission from both sources and so confirm that these LAE candidates are physically associated with the BRI1202-0725 system. We also report the lack of detection of any high-ionization emission lines (N v 1240, Si iv 1396, C iv 1549 and He ii 1640) and find that these systems are likely not photoionized by the quasar, leaving in situ star formation as the main powering source of these LAEs. We also find that both LAEs have Lyα emission much broader (~1300 km s –1 ) than the [C ii ] emission and broader than most LAEs. In addition, both LAEs have roughly symmetric Lyα profiles implying that both systems are within the H ii sphere produced by the quasar. This is the first time that the proximity zone of a quasar is probed by exploiting nearby LAEs. We discuss the observational properties of these galaxies in the context of recent galaxy formation models.