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Register a new userIonized and atomic interstellar medium in the z = 6.003 quasar SDSS J2310+1855
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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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It has been known for half a century that the interstellar medium (ISM) of our Galaxy is structured on scales as small as a few hundred km, more than 10 orders of magnitude smaller than typical ISM structures and energy input scales. In this review we focus on neutral and ionized structures on spatial scales of a few to ~10^4 Astronomical Units (AU) which appear to be highly overpressured, as these have the most important role in the dynamics and energy balance of interstellar gas: the Tiny Scale Atomic Structure (TSAS) and Extreme Scattering Events (ESEs) as the most over-pressured example of the Tiny Scale Ionized Structures (TSIS). We review observational results and highlight key physical processes at AU scales. We present evidence for and against microstructures as part of a universal turbulent cascade and as discrete structures, and review their association with supernova remnants, the Local Bubble, and bright stars. We suggest a number of observational and theoretical programs that could clarify the nature of AU structures. TSAS and TSIS probe spatial scales in the range of what is expected for turbulent dissipation scales, therefore are of key importance for constraining exotic and not-well understood physical processes which have implications for many areas of astrophysics. The emerging picture is one in which a magnetized, turbulent cascade, driven hard by a local energy source and acting jointly with phenomena such as thermal instability, is the source of these microstructures.
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.
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 report the discovery of six spatially extended (10-100 kpc) line-emitting nebulae in the z=0.57 galaxy group hosting PKS0405-123, one of the most luminous quasars at z<1. The discovery is enabled by the Multi Unit Spectroscopic Explorer (MUSE) and provides tantalizing evidence connecting large-scale gas streams with nuclear activity on scales of <10 proper kpc (pkpc). One of the nebulae exhibits a narrow, filamentary morphology extending over 50 pkpc toward the quasar with narrow internal velocity dispersion (50 km/s) and is not associated with any detected galaxies, consistent with a cool intragroup medium (IGrM) filament. Two of the nebulae are 10 pkpc North and South of the quasar with tidal arm like morphologies. These two nebulae, along with a continuum emitting arm extending 60 pkpc from the quasar are signatures of interactions which are expected to redistribute angular momentum in the host interstellar medium (ISM) to facilitate star formation and quasar fueling in the nucleus. The three remaining nebulae are among the largest and most luminous [O III] emitting `blobs known (1400-2400 pkpc^2) and correspond both kinematically and morphologically with interacting galaxy pairs in the quasar host group, consistent with arising from stripped ISM rather than large-scale quasar outflows. The presence of these large- and small-scale nebulae in the vicinity of a luminous quasar bears significantly on the effect of large-scale environment on galaxy and black hole fueling, providing a natural explanation for the previously known correlation between quasar luminosity and cool circumgalactic medium (CGM).
We combine state-of-the-art models for the production of stellar radiation and its transfer through the interstellar medium (ISM) to investigate ultraviolet-line diagnostics of stars, the ionized and the neutral ISM in star-forming galaxies. We start by assessing the reliability of our stellar population synthesis modelling by fitting absorption-line indices in the ISM-free ultraviolet spectra of 10 Large-Magellanic-Cloud clusters. In doing so, we find that neglecting stochastic sampling of the stellar initial mass function in these young ($sim10$-100 Myr), low-mass clusters affects negligibly ultraviolet-based age and metallicity estimates but can lead to significant overestimates of stellar mass. Then, we proceed and develop a simple approach, based on an idealized description of the main features of the ISM, to compute in a physically consistent way the combined influence of nebular emission and interstellar absorption on ultraviolet spectra of star-forming galaxies. Our model accounts for the transfer of radiation through the ionized interiors and outer neutral envelopes of short-lived stellar birth clouds, as well as for radiative transfer through a diffuse intercloud medium. We use this approach to explore the entangled signatures of stars, the ionized and the neutral ISM in ultraviolet spectra of star-forming galaxies. We find that, aside from a few notable exceptions, most standard ultraviolet indices defined in the spectra of ISM-free stellar populations are prone to significant contamination by the ISM, which increases with metallicity. We also identify several nebular-emission and interstellar-absorption features, which stand out as particularly clean tracers of the different phases of the ISM.
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