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Register a new userSpatially Resolved Interstellar Medium and Highly-Excited Dense Molecular Gas in the Most Luminous Quasar at z=6.327
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Among more than 200 quasars known at $zgtrsim6$, only one object, J0100+2802 (z=6.327), was found hosting a $>10^{10}M_odot$ super-massive black hole (SMBH). In order to investigate the host galaxy properties of J0100+2802, we performed multi-band ALMA observations, aiming at mapping the dust continuum, [CII] and CO(6-5) emission lines with sub-kiloparsec scale resolution, as well as detecting high-J CO lines in CO(11-10), CO(10-9), and CO(7-6). The galaxy size is measured to be $R_{rm major}=3.6pm0.2$ kpc from the high resolution continuum observations. No ordered motion on kilo-parsec scales was found in both [CII] and CO(6-5) emissions. The velocity dispersion is measured to be 161$pm$7 km s$^{-1}$, $sim$3 times smaller than that estimated from the local M-$sigma$ relation. In addition, we found that the CO emission is more concentrate (a factor of 1.8$pm$0.4) than the [CII] emission. Together with CO(2-1) detected by VLA, we measured the CO Spectral Line Energy Distribution (SLED), which is best fit by a two-components model, including a cool component at $sim24$ K with a density of $n_{rm (H_2)}$=10$^{4.5}$ cm$^{-3}$, and a warm component at $sim224$ K with a density of $n_{rm (H_2)}$=10$^{3.6}$ cm$^{-3}$. We also fitted the dust continuum with a graybody model, which indicates that it has either a high dust emissivity $betagtrsim2$ or a hot dust temperature $T_{rm dust}gtrsim60$ K, or a combination of both factors. The highly excited CO emission and hot dust temperature suggest that the powerful AGN in J0100+2802 could contribute to the gas and dust heating although future observations are needed to confirm this.
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We present high-resolution observations (0.2-1.5) of multiple dense gas tracers, HCN and HCO$^+$ ($J$ = 1-0, 3-2, and 4-3), HNC ($J$ = 1-0), and CS ($J$ = 7-6) lines, toward the nearby luminous infrared galaxy VV 114 with the Atacama Large Millimeter/submillimeter Array. All lines are robustly detected at the central gaseous filamentary structure including the eastern nucleus and the Overlap region, the collision interface of the progenitors. We found that there is no correlation between star formation efficiency and dense gas fraction, indicating that the amount of dense gas does not simply control star formation in VV 114. We predict the presence of more turbulent and diffuse molecular gas clouds around the Overlap region compared to those at the nuclear region assuming a turbulence-regulated star formation model. The intracloud turbulence at the Overlap region might be excited by galaxy-merger-induced shocks, which also explains the enhancement of gas-phase CH$_3$OH abundance previously found there. We also present spatially resolved spectral line energy distributions of HCN and HCO$^+$ for the first time, and derive excitation parameters by assuming optically-thin and local thermodynamic equilibrium (LTE) conditions. The LTE model revealed that warmer, HCO$^+$-poorer molecular gas medium is dominated around the eastern nucleus, harboring an AGN. The HCN abundance is remarkably flat ($sim$3.5 $times$ 10$^{-9}$) independently of the various environments within the filament of VV 114 (i.e., AGN, star formation, and shock).
We present the results of our ALMA HCN J=3-2 and HCO+ J=3-2 line observations of a uniformly selected sample (>25) of nearby ultraluminous infrared galaxies (ULIRGs) at z < 0.15. The emission of these dense molecular gas tracers and continuum are spatially resolved in the majority of observed ULIRGs for the first time with achieved synthesized beam sizes of ~0.2 arcsec or ~500 pc. In most ULIRGs, the HCN-to-HCO+ J=3-2 flux ratios in the nuclear regions within the beam size are systematically higher than those in the spatially extended regions. The elevated nuclear HCN J=3-2 emission could be related to (a) luminous buried active galactic nuclei, (b) the high molecular gas density and temperature in ULIRGs nuclei, and/or (c) mechanical heating by spatially compact nuclear outflows. A small fraction of the observed ULIRGs display higher HCN-to-HCO+ J=3-2 flux ratios in localized off-nuclear regions than those of the nuclei, which may be due to mechanical heating by spatially extended outflows. The observed nearby ULIRGs are generally rich in dense (>10^5 cm^-3) molecular gas, with an estimated mass of >10^9 Msun within the nuclear (a few kpc) regions, and dense gas can dominate the total molecular mass there. We find a low detection rate (<20%) regarding the possible signature of a vibrationally excited (v2=1f) HCN J=3-2 emission line in the vicinity of the bright HCO+ J=3-2 line that may be due, in part, to the large molecular line widths of ULIRGs.
Context. Spatially resolved observations of the ionized and molecular gas are critical for understanding the physical processes that govern the interstellar medium (ISM) in galaxies. Aims. To study the morpho-kinematic properties of the ionized and molecular gas in three dusty starburst galaxies at $z = 0.12-0.17$ to explore the relation between molecular ISM gas phase dynamics and the star-formation activity. Methods. We analyse $sim$kpc-scale ALMA CO(1--0) and seeing limited SINFONI Paschen-$alpha$ observations. We use a dynamical mass model, which accounts for beam-smearing effects, to constrain the CO-to-H$_2$ conversion factor. Results. One starburst galaxy shows irregular morphology which may indicate a major merger, while the other two systems show disc-like morpho-kinematics. The two disc-like starbursts show molecular gas velocity dispersion values comparable with that seen in local LIRG/ULIRGs, but in an ISM with molecular gas fraction and surface density values consistent to that reported for local star-forming galaxies. These molecular gas velocity dispersion values can be explained by assuming vertical pressure equilibrium. The star-formation activity is correlated with the molecular gas content suggesting depletion times of the order of $sim 0.1-1$ Gyr. The star formation rate surface density ($Sigma_{rm SFR}$) correlates with the ISM pressure set by self-gravity ($P_{rm grav}$) following a power law with an exponent close to 0.8. Conclusions. In dusty disc-like starburst galaxies, our data support the scenario in which the molecular gas velocity dispersion values are driven by the ISM pressure set by self-gravity, responsible to maintain the vertical pressure balance. The correlation between $Sigma_{rm SFR}$ and $P_{rm grav}$ suggests that, in these dusty starbursts galaxies, the star formation activity arises as a consequence of the ISM pressure balance.
We present high-resolution VLA observations of the molecular gas in the host galaxy of the highest redshift quasar currently known, SDSS J1148+5251 (z=6.42). Our VLA data of the CO(3-2) emission have a maximum resolution of 0.17 x 0.13 (~1 kpc), and enable us to resolve the molecular gas emission both spatially and in velocity. The molecular gas in J1148+5251 is extended to a radius of 2.5 kpc, and the central region shows 2 peaks, separated by 0.3 (1.7 kpc). These peaks account for about half of the total emission, while the remainder is more extended. Each of these unresolved peaks contains a molecular gas mass of ~5 x 10^9 M_sun (similar to the total mass found in nearby ULIRGS) and has an intrinsic brightness temperature of ~35 K (averaged over the 1 kpc-sized beam), comparable to what is found in nearby starburst centers. Assuming that the molecular gas is gravitationally bound, we estimate a dynamical mass of ~4.5 x 10^10 M_sun within a radius of 2.5 kpc (~5.5 x 10^10 M_sun if corrected for a derived inclination of i~65 deg.). This dynamical mass estimate leaves little room for matter other than the detected molecular gas, and in particular the data are inconsistent with a ~10^12 M_sun stellar bulge which would be predicted based on the M_BH-sigma_bulge relation. This finding may indicate that black holes form prior to the assembly of the stellar bulges and that the dark matter halos are less massive than predicted based on the black hole/bulge mass relationship.
Observing the interstellar medium (ISM) in $z gtrsim 6$ quasars host galaxies is essential for understanding the co-evolution between the supermassive black holes and their hosts. To probe the gas physical conditions and search for imprints of Active Galactic Nuclei (AGN) on the ISM, we report ALMA observations of the $rm [N II]_{122 mu m}$ and $rm [O I]_{146 mu m}$ lines and the underlying continuum from the $z=6.003$ quasar SDSS J231038.88+185519.7. Together with previous $rm [C II]_{158 mu m}$ and $rm [O III]_{88 mu m}$ observations, we use the ratios of these fine-structure lines to probe the ISM properties. Similar to other high-$z$ systems, this object exhibits a $rm [C II]_{158 mu m}$/$rm [O I]_{146 mu m}$ ratio comparable to the lowest values found in local (Ultra) luminous infrared galaxies, suggesting a warmer and denser gas component compared to typical local systems. The $rm [O III]_{88 mu m}$/$rm [O I]_{146 mu m}$ ratio is lower than that of other local and high-$z$ systems, indicating a smaller ionized gas fraction in this quasar. The $rm [O III]_{88 mu m}$/$rm [N II]_{122 mu m}$ ratio is comparable to that of local systems, and suggests a metallicity of $Z/Z_{odot}$=1.5$-$2.1. Based on the $rm [N II]_{122 mu m}$ detection, we estimate that $17%$ of the $rm [C II]_{158 mu m}$ emission is associated with ionized gas. The $rm [N II]_{122 mu m}$ line shows a flux deficit comparable to local systems. The $rm [O I]_{146 mu m}$ line, with a $rm [O I]_{146 mu m}$/FIR ratio $ge 2times$ than expected from the local relation, indicates no $rm [O I]_{rm 146 mu m}$ deficit. The low $rm [C II]_{158 mu m}$/$rm [O I]_{146 mu m}$ ratio, together with the high $rm [O I]_{146 mu m}$/FIR ratio in J2310+1855, reveals that the warm and dense gas is likely a result of AGN heating to the ISM.
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