Total Gas Mass Research Articles

Ionized Carbon in Galaxies: The [C ii] 158 μm Line as a Total Molecular Gas Mass Tracer Revisited

In this paper, we present a statistical study of the [C ii] 158 μm line and the CO(1−0) emission for a sample of ∼200 local and high-z (32 sources with z > 1) galaxies with very different physical conditions. We explore the correlation between the luminosities of [C ii] and CO(1−0) lines and obtain a strong linear relationship, confirming that [C ii] is able to trace total molecular gas mass, with a small difference between (U)LIRGs and less-luminous galaxies. The tight and linear relation between [C ii] and CO(1−0) is likely determined by the average value of the observed visual extinction A V and the range of G 0/n in galaxies. Further investigations into the dependence of L [C ii]/L CO(1−0) on different physical properties show that L [C ii]/L CO(1−0) (1) anticorrelates with ΣIR, and the correlation becomes steeper when ΣIR ≳ 1011 L ⊙ kpc−2; (2) correlates positively with the distance from the main sequence Δ(MS) when Δ(MS) ≲ 0; and (3) tends to show a systematically smaller value in systems where the [C ii] emission is dominated by ionized gas. Our results imply that caution needs to be taken when applying a constant [C ii]-to-M mol conversion factor to estimate the molecular gas content in extreme cases, such as galaxies having low-level star formation activity or high star formation rate surface density.

Evidence for a Sharp CO Snow Line Transition in a Protoplanetary Disk and Implications for Millimeter-wave Observations of CO Isotopologues

Observations of CO isotopologue emission from protoplanetary disks at millimeter wavelengths are a powerful tool for probing the CO snow line, an important marker for disk chemistry, and also for estimating total disk gas mass, a key quantity for planet formation. We use simple models to demonstrate that the vertical thickness of an isothermal layer around the disk midplane has important effects on the CO column density radial profile, with a thick layer producing a sharp CO snow line transition. We simulate next-generation Very Large Array (ngVLA) and Atacama Large Millimeter/submillimeter Array (ALMA) images to show that this sharp change in the CO column density can be detected in the derivative of the radial profile of emission from optically thin CO isotopologue lines. We apply this method to archival ALMA observations of the disk around the Herbig Ae star HD 163296 in the C17O and C18O J = 1–0 and J = 2–1 lines to identify a sharp CO snow line transition near ∼80 au (0.″8 at 101 pc), and show the CO column density decreases by more than a factor of 20. This finding is consistent with previous inferences from the steep rise of N2H+ emission, which marks the location where CO depletes. We also demonstrate that the disk’s thermal structure introduces significant systematic uncertainty to estimates of total disk gas mass derived from these lines. The substantial improvement in sensitivity envisioned for the ngVLA over ALMA for observations of ground-state lines of CO isotopologues has the potential to extend this approach to a much larger population of disks.

Discovery of a > 13 Mpc long X-ray filament between two galaxy clusters beyond three times their virial radii

Context. A significant fraction of the missing baryons in the local Universe is expected to reside in large-scale filaments that may be observable in soft X-ray emission. Until now, however, very few candidate emission filaments have been found in individual systems, and none beyond three times the virial radius of the clusters at the nodes of these filaments. The new Spectrum Roentgen Gamma (SRG) eROSITA X-ray telescope has a superior response to extended soft X-rays, which makes it ideal for studying low X-ray surface brightness emission of cosmic filaments. Aims. We search for extended X-ray emission between the two nearby galaxy clusters Abell 3667 and Abell 3651, which are separated by a projected transverse distance of ~13 Mpc, using data from the SRG/eROSITA All-Sky Survey. Methods. We performed a detailed X-ray image analysis of the region between the two galaxy clusters and conducted a redshift analysis of the sources between them. We carried out a thorough surface brightness and spectral analysis between the clusters. The analysis was complemented with an X-ray pointed observation from XMM-Newton, infrared 2MASS data, and redshift information from NED. Results. We discover an emission filament beyond the known radio relic northwest of A3667 and even beyond three times its virial radius. It is smoothly connected to A3651. The X-ray emission in the direction of the filament shows an enhancement of (30 ± 3) % with a significance of 11 σ. The 2MASS map and redshift analysis show an alignment of galaxies along the filament and make a projection effect unlikely. Taking the redshift progression of galaxies within the filament into account, we estimate its three-dimensional length to be in the range of 25 Mpc–32 Mpc. The surface brightness analysis in combination with the temperature T = (0.91−0.11+0.07) keV and metallicity Z = (0.10−0.08+0.05) Z⊙ from the spectral analysis leads to estimates of a total flux, gas mass, and central baryon overdensity of FX = (7.4 ± 1.2)×10−12 erg s−1 cm−2, Mg = (2.7−0.8+1.4) M⊙ and δ0 = 215−50+86.

AGN feeding along a one-armed spiral in NGC 4593

Context. We investigate active galactic nuclei (AGN) feeding through the molecular gas (CO(2−1) emission) properties of the local Seyfert 1 galaxy NGC 4593, using Atacama Large Millimeter Array (ALMA) observations and other multi-wavelength data. Aims. Our study aims to understand the interplay between the AGN and the interstellar medium (ISM) in this galaxy, examining the role of the AGN in steering gas dynamics within its host galaxy, evaluating the energy injected into the ISM, and determining whether gas is inflowing or outflowing from the galaxy. Methods. After reducing the ALMA CO(2−1) images, we employed two models, 3D-BAROLO and DISCFIT, to construct a disc model and fit its emission to the ALMA data. Additionally, we used photometric data to build a spectral energy distribution (SED) and apply the CIGALE code to derive key physical properties of the AGN and its host. Results. Our analysis reveals a complex interplay within NGC 4593, including a clear rotational pattern, the influence of a non-axisymmetric bar potential, and a central molecular zone (CMZ)-like ring. We observe an outflow of CO(2−1) gas along the minor axis, at a distance of ∼220 pc from the nucleus. The total molecular gas mass is estimated to be 1 − 5 × 108 M⊙, with non-circular motions contributing 10%. Our SED analysis indicates an AGN fraction of 0.88 and a star formation rate (SFR) of 0.42 M⊙ yr−1. Conclusions. These findings highlight the complex dynamics in the centre of NGC 4593, which are significantly influenced by the presence of the AGN. The overall physical properties of this system suggest that the AGN has a substantial impact on the evolution of NGC 4593.

Abundant Molecular Gas in the Central Region of Lenticular Galaxy PGC 39535

Lenticular galaxies (S0s) in the local Universe are generally absent of recent star formation and lack molecular gas. In this paper, we investigate one massive (M * ∼ 5 × 1010 M ⊙) star-forming S0, PGC 39535, with the Northern Extended Millimeter Array (NOEMA). Using optical data from the Sloan Digital Sky Survey IV Mapping Nearby Galaxies at the Apache Point Observatory survey, we find star formation mainly concentrates in the central region of PGC 39535. The total star formation rate estimated using extinction-corrected Hα flux is 1.57 M ⊙ yr−1. The results of the NOEMA observation suggest that the molecular gas mainly concentrates in the central regions as a gaseous bar and a ring-like structure, and shows similar kinematics as the stellar and ionized gas components. The total molecular gas mass estimated from CO(1–0) is (5.42 ± 1.52) × 109 M ⊙. We find PGC 39535 lies on the star-forming main sequence but falls below the Kennicutt–Schmidt relation of spiral galaxies, suggesting that the star formation efficiency may be suppressed by the massive bulge. The existence of a second Gaussian component in the CO spectrum of the central region indicates possible gas flows. Furthermore, our analyses suggest that PGC 39535 resides in the center of a massive group and the derived star formation history indicates it may experience a series of gas-rich mergers over the past 2–7 Gyr.

Nucleosynthesis Contribution of Neutrino-dominated Accretion Flows to the Solar Neighborhood

The elemental abundances of stars reflect the complex enrichment history of the Galaxy. To explore and explain the metal enrichment history of the cosmic environment near our solar system, we study the evolution of 56Fe abundance over time and [Mg/Fe] versus [Fe/H] evolution in the solar neighborhood. Core-collapse supernovae make the dominant contribution in the early stages, while Type Ia supernovae (SNe Ia) have a delayed and dominant impact in the later stages. In this work, we consider the nucleosynthesis contribution of neutrino-dominated accretion flows (NDAFs) formed at the end of the lives of massive stars. The results show that the [Fe/H] gradually increases over time and eventually reaches [Fe/H] = 0 and above, reproducing the chemical enrichment process in the solar neighborhood. Before the onset of SNe Ia, the ratio of 56Fe mass to the total gas mass increases by a factor of at most ∼1.44 when NDAFs are taken into account. We find that by including NDAF in our models, the agreement with the observed metallicity distribution of metal-poor stars in the solar neighborhood (<1 kpc) is improved while not significantly altering the location of the metallicity peak. This inclusion can also reproduce the observed evolutionary change of [Mg/Fe] at [Fe/H] ∼ −1.22, bringing the ratio to match the solar abundance. Our results provide an extensive understanding of metallicity evolution in solar environments by highlighting the nucleosynthesis contribution of NDAF outflows in the solar neighborhood.

IPA: Class 0 Protostars Viewed in CO Emission Using JWST

We investigate the bright CO fundamental emission in the central regions of five protostars in their primary mass assembly phase using new observations from JWST’s Near-Infrared Spectrograph and Mid-Infrared Instrument. CO line emission images and fluxes are extracted for a forest of ∼150 rovibrational transitions from two vibrational bands, v = 1−0 and v = 2−1. However, 13CO is undetected, indicating that 12CO emission is optically thin. We use H2 emission lines to correct fluxes for extinction and then construct rotation diagrams for the CO lines with the highest spectral resolution and sensitivity to estimate rotational temperatures and numbers of CO molecules. Two distinct rotational temperature components are required for v = 1 (∼600 to 1000 K and 2000 to ∼104 K), while one hotter component is required for v = 2 (≳3500 K). 13CO is depleted compared to the abundances found in the interstellar medium, indicating selective UV photodissociation of 13CO; therefore, UV radiative pumping may explain the higher rotational temperatures in v = 2. The average vibrational temperature is ∼1000 K for our sources and is similar to the lowest rotational temperature components. Using the measured rotational and vibrational temperatures to infer a total number of CO molecules, we find that the total gas masses range from lower limits of ∼1022 g for the lowest mass protostars to ∼1026 g for the highest mass protostars. Our gas mass lower limits are compatible with those in more evolved systems, which suggest the lowest rotational temperature component comes from the inner disk, scattered into our line of sight, but we also cannot exclude the contribution to the CO emission from disk winds for higher mass targets.

Merging Gas-rich Galaxies That Harbor Low-luminosity Twin Quasars at z = 6.05: A Promising Progenitor of the Most Luminous Quasars

We present Atacama Large Millimeter/submillimeter Array [C ii] 158 μm line and underlying far-IR continuum emission observations (0.″57 × 0.″46 resolution) toward a quasar–quasar pair system recently discovered at z = 6.05. The quasar nuclei (C1 and C2) are faint (M 1450 ≳ −23 mag), but we detect very bright [C ii] emission bridging the 12 kpc between the two objects and extending beyond them (total luminosity L [C ii] ≃ 6 × 109 L ⊙). The [C ii]-based total star formation rate of the system is ∼550 M ⊙ yr−1 (the IR-based dust-obscured star formation is ∼100 M ⊙ yr−1), with a [C ii]-based total gas mass of ∼1011 M ⊙. The dynamical masses of the two galaxies are large (∼9 × 1010 M ⊙ for C1 and ∼5 × 1010 M ⊙ for C2). There is a smooth velocity gradient in [C ii], indicating that these quasars are a tidally interacting system. We identified a dynamically distinct, fast-[C ii] component around C1: detailed inspection of the line spectrum there reveals the presence of a broad-wing component, which we interpret as the indication of fast outflows with a velocity of ∼600 km s−1. The expected mass-loading factor of the outflows, after accounting for multiphase gas, is ≳2 − 3, which is intermediate between AGN-driven and starburst-driven outflows. Hydrodynamic simulations in the literature predict that this pair will evolve to a luminous (M 1450 ≲ −26 mag), starbursting (≳1000 M ⊙ yr−1) quasar after coalescence, one of the most extreme populations in the early Universe.

H i content at cosmic noon – a millimetre-wavelength perspective

ABSTRACT In order to understand galaxy growth evolution, it is critical to constrain the evolution of its building block: gas. Mostly comprised by Hydrogen in its neutral (H i) and molecular (H$_2$) phases, the latter is the one mostly directly associated to star formation, while the neutral phase is considered the long-term gas reservoir. In this work, we make use of an empirical relation between dust emission at millimetre wavelengths and total gas mass in the interstellar medium (M$_{\rm HI}$ plus M$_{\rm H_2}$) in order to retrieve the H i content in galaxies. We assemble an heterogeneous sample of 335 galaxies at $0.01\lt z\lt 6.4$ detected in both mm-continuum and carbon monoxide (CO), with special focus on a blindly selected sample to retrieve H i cosmological content when the Universe was $\sim 2-6\,$ Gyr old ($1\lt z\lt 3$). We find no significant evolution with redshift of the M$_{\rm HI}$/M$_{\rm H_2}$ ratio, which is about $1-3$ (depending on the relation used to estimate M$_{\rm HI}$). This also shows that M$_{\rm H_2}$-based gas depletion times are underestimated overall by a factor of $2-4$. Compared to local Universe H i mass functions, we find that the number density of galaxies with M$_{\rm HI}\gtrsim 10^{10.5}\,$M$_\odot$ significantly decreased since 8–12 Gyr ago. The specific sample used for this analysis is associated to 20–50 per cent of the total cosmic H i content as estimated via Damped Lyman-$\alpha$ Absorbers. In IR luminous galaxies, H i mass content decreases between $z\sim 2.5$ and $z\sim 1.5$, while H$_2$ seems to increase. We also show source detection expectations for SKA surveys.

MINDS: Mid-infrared atomic and molecular hydrogen lines in the inner disk around a low-mass star

Context. Understanding the physical conditions of circumstellar material around young stars is crucial to star and planet formation studies. In particular, very low-mass stars (M★ &lt; 0.2 M⊙) are interesting sources to characterize as they are known to host a diverse population of rocky planets. Molecular and atomic hydrogen lines can probe the properties of the circumstellar gas. Aims. This work aims to measure the mass accretion rate, the accretion luminosity, and more generally the physical conditions of the warm emitting gas in the inner disk of the very low-mass star 2MASS-J16053215-1933159. We investigate the source mid-infrared spectrum for atomic and molecular hydrogen line emission. Methods. We present the full James Webb Space Telescope (JWST) Mid-InfraRed Instrument (MIRI) Medium Resolution Spectrometer (MRS) spectrum of the protoplanetary disk around the very low-mass star 2MASS-J16053215-1933159 from the MINDS GTO program, previously shown to be abundant in hydrocarbon molecules. We analyzed the atomic and molecular hydrogen lines in this source by fitting one or multiple Gaussian profiles. We then built a rotational diagram for the H2 lines to constrain the rotational temperature and column density of the gas. Finally, we compared the observed atomic line fluxes to predictions from two standard emission models. Results. We identify five molecular hydrogen pure rotational lines and 16 atomic hydrogen recombination lines in the 5–20 µm spectral range. The spectrum indicates optically thin emission for both species. We use the molecular hydrogen lines to constrain the mass and temperature of the warm emitting gas. We derive a total gas mass of only 2.3 × 10−5 MJup and a temperature of 635 K for the warm H2 gas component located in the very inner disk (r &lt; 0.033 au), which only accounts for a small fraction of the upper limit for the disk mass from continuum observations (0.2 MJup). The HI (7−6) recombination line is used to measure the mass accretion rate (4.0 × 10−10 M⊙ yr−1) and luminosity (3.1 × 10−3 L⊙) onto the central source. This line falls close to the HI (11−8) line, however at the spectral resolution of JWST MIRI we managed to measure both separately. Previous studies based on Spitzer have measured the combined flux of both lines to measure accretion rates. HI recombination lines can also be used to derive the physical properties of the gas using atomic recombination models. The model predictions of the atomic line relative intensities constrain the atomic hydrogen density to about 109−1010 cm−3 and temperatures up to 5000 K. Conclusions. The JWST-MIRI MRS observations for the very low-mass star 2MASS-J16053215-1933159 reveal a large number of emission lines, many originating from atomic and molecular hydrogen because we are able to look into the disk warm molecular layer. Their analysis constrains the physical properties of the emitting gas and showcases the potential of JWST to deepen our understanding of the physical and chemical structure of protoplanetary disks.

Precipitation and evaporation affecting landfill gas migration into passive methane oxidation biosystems: Models development and verification

Passive methane oxidation biosystems (PMOBs) are developed as an innovative and cost-effective solution to reduce methane (CH4) emissions from municipal solid waste landfills. A PMOB consists of a methane oxidation layer (MOL) and an underlying gas distribution layer (GDL). The length of unrestricted gas migration (LUGM) has been recently proposed as the design criterion for PMOBs where the LUGM is calculated as the horizontal length along the MOL-GDL interface with the volumetric gas content (θa) exceeding the threshold volumetric gas content (θa,occ). This paper examined water and gas migration within three PMOBs with different MOL-GDL interfaces subject to precipitation and evaporation using verified numerical models. The results show that the use of a single-phase flow model underestimates the LUGM values of the PMOB for heavy precipitation events, and a two-phase flow model should be used to calculate both the LUGM and the total gas mass flow rate into the MOL when designing PMOBs. Both zig-zag and trapezoidal MOL-GDL interfaces can redistribute the gas mass flow rate at the MOL-GDL interface, while the trapezoidal MOL-GDL interface slightly outperforms the zig-zag MOL-GDL interface for enhancing the total gas mass flow rate into the MOL when comparing with the planar MOL-GDL interface. The zig-zag and trapezoidal MOL-GDL interfaces allow gas migration in the upper part of each PMOB segment even when the lower part of each PMOB segment was filled with water, and thus have a potential to minimize hotspot formation.

Dynamical modelling and the origin of gas turbulence in z ∼ 4.5 galaxies

Context. In recent years, a growing number of regularly rotating galaxy discs have been found at z ≥ 4. Such systems provide us with the unique opportunity to study the properties of dark matter (DM) halos at these early epochs, the turbulence within the interstellar medium and the evolution of scaling relations. Aims. Here, we investigate the dynamics of four gas discs in galaxies at z ∼ 4.5 observed with ALMA in the [CII] 158 μm fine-structure line. We aim to derive the structural properties of the gas, stars and DM halos of the galaxies and to study the mechanisms driving the turbulence in high-z discs. Methods. We decomposed the rotation curves into baryonic and DM components within the extent of the [CII] discs, that is, 3 to 5 kpc. Furthermore, we used the gas velocity dispersion profiles as a diagnostic tool in investigating the mechanisms driving the turbulence in the discs. Results. We obtain total stellar, gas and DM masses in the ranges of log(M/M⊙) = 10.3 − 11.0, 9.8 − 11.3, and 11.2 − 13.3, respectively. We find dynamical evidence in all four galaxies for the presence of compact stellar components conceivably, stellar bulges. The turbulence present in the galaxies appears to be primarily driven by stellar feedback, negating the necessity for large-scale gravitational instabilities. Finally, we investigate the position of our galaxies in the context of local scaling relations, in particular the stellar-to-halo mass and Tully–Fisher analogue relations.

Low-mass Population III Star Formation due to the HD Cooling Induced by Weak Lyman–Werner Radiation

Lyman–Werner (LW) radiation photodissociating molecular hydrogen (H2) influences the thermal and dynamical evolution of the Population III (Pop III) star-forming gas cloud. The effect of powerful LW radiation has been well investigated in the context of supermassive black hole formation in the early Universe. However, the average intensity in the early Universe is several orders of magnitude lower. For a comprehensive study, we investigate the effects of LW radiation at 18 different intensities, ranging from J LW/J 21 = 0 (no radiation) to 30 (H-cooling cloud), on the primordial star-forming gas cloud obtained from a three-dimensional cosmological simulation. The overall trend with increasing radiation intensity is a gradual increase in the gas cloud temperature, consistent with previous works. Due to the HD cooling, however, the dependence of gas cloud temperature on J LW deviates from the aforementioned increasing trend for a specific range of intensities (J LW/J 21 = 0.025–0.09). In HD-cooling clouds, the temperature remained below 200 K during 105 yr after the first formation of the high-density region, maintaining a low accretion rate. Finally, the HD-cooling clouds have only a low-mass dense core (above 108 cm−3) with about 1–16 M ⊙, inside of which a low-mass Pop III star with ≤0.8 M ⊙ (a so-called “surviving star”) could form. The upper limit of star formation efficiency Mcore/Mvir,gas significantly decreases from 10−3 to 10−5 as HD cooling becomes effective. This tendency indicates that, whereas the total gas mass in the host halo increases with the LW radiation intensity, the total Pop III stellar mass does not increase similarly.

Probing the interstellar medium of the quasar BRI 0952−0115

Context. The extent of the effect of active galactic nuclei (AGN) on their host galaxies at high-redshift is not apparent. The processes governing the co-eval evolution of the stellar mass and the mass of the central supermassive black hole, along with the effects of the supermassive black hole on the host galaxy, remain unclear. Studying this effect in the distant universe is a difficult process as the mechanisms of tracing AGN activity can often be inaccurately associated with intense star formation and vice versa. Aims. Our aim is to better understand the processes governing the interstellar medium (ISM) of the quasar BRI 0952−0952 at z = 4.432, specifically with regard to the individual heating processes at work and to place the quasar in an evolutionary context. Methods. We analyzed ALMA archival bands 3, 4, and 6 data and combined the results with high-resolution band-7 ALMA observations of the quasar. We detected [C I](2–1), [C II](2P3/2 − 2P1/2), CO(5–4), CO(7–6), CO(12–11), OH 2Π1/2(3/2 − 1/2), and H2O(211 − 202), and we report a tentative detection of OH+. We updated the lensing model and we used the radiative transfer code MOLPOP-CEP to produce line emission models which we compared with our observations. Results. We used the [C I] line emission to estimate the total molecular gas mass in the quasar. We present results from the radiative transfer code MOLPOP-CEP constraining the properties of the CO emission and suggest different possible scenarios for heating mechanisms within the quasar. We extended our results from MOLPOP-CEP to the additional line species detected in the quasar to place stronger constraints on the ISM properties. Conclusions. Modeling from the CO SLED suggests that there are extreme heating mechanisms operating within the quasar in the form of star formation or AGN activity; however, with the current data, it remains unclear which of the two is the preferred mechanism as both models reasonably reproduce the observed CO line fluxes. The updated lensing model suggests a velocity gradient across the [C II] line, suggestive of ongoing kinematical processes within the quasar. We find that the H2O emission in BRI 0952 is likely correlated with star-forming regions of the ISM. We used the molecular gas mass from [C I] to calculate a depletion time for the quasar. We conclude that BRI 0952−0952 is a quasar with a significant AGN contribution while also showing signs of extreme starburst activity, indicating that the quasar could be in a transitional phase between a starburst-dominated stage and an AGN-dominated stage.

Benchmarking the IRDC G351.77−0.53: Gaia DR3 distance, mass distribution, and star formation content

ABSTRACT While intensively studied, it remains unclear how the star formation (SF) in infrared dark clouds (IRDCs) compares to that of nearby clouds. We study G351.77-0.53 (henceforth G351), a cluster-forming filamentary IRDC. We begin by characterizing its young stellar object (YSO) content. Based on the average parallax of likely members, we obtain a Gaia distance of $\sim \, 2.0\pm 0.14$ kpc, resolving the literature distance ambiguity. Using our Herschel-derived N(H2) map, we measure a total gas mass of 10 200 M⊙ (within 11 pc2) and the average line-mass profile of the entire filament, which we model as $\lambda =~1660 (w/\rm pc)^{0.62}\, \, {\rm M}_{\odot }\, \rm {pc}^{-1}$. At w &amp;lt; 0.63 pc, our λ profile is higher and has a steeper power-law index than λ profiles extracted in Orion A and most of its substructures. Based on the YSOs inside the filament area, we estimate the SF efficiency (SFE) and SF rate (SFR). We calculate a factor of 5 incompleteness correction for our YSO catalogue relative to Spitzer surveys of Orion A. The G351 SFE is ∼1.8 times lower than that of Orion A and lower than the median value for local clouds. We measure SFR and gas masses to estimate the efficiency per free-fall time, ϵff. We find that ϵff is ∼1.1 dex below the previously proposed mean local relation, and $\sim \, 4.7\times$ below Orion A. These observations indicate that local SF-relations do not capture variations present in the Galaxy. We speculate that cloud youth and/or magnetic fields might account for the G351 inefficiency.

Constraining the gas mass of Herbig disks using CO isotopologues

Context. The total disk mass sets the formation potential for exoplanets. Obtaining the disk mass is however not an easy feat, as one needs to consider the optical thickness, temperature, photodissociation, and freeze-out of potential mass tracers. Carbon-monoxide (CO) has been used as a gas mass tracer in T Tauri disks, but was found to be less abundant than expected due to the freeze-out and chemical conversion of CO on the surfaces of cold dust grains. The disks around more massive intermediate mass pre-main sequence stars called Herbig disks are likely to be warmer, allowing for the possibility of using CO as a more effective total gas mass tracer. Aims. This work aims to obtain the gas mass and size of Herbig disks observed with ALMA and compare these to previous works on T Tauri disks and debris disks. Methods. Using ALMA archival data and new NOEMA data of 12CO, 13CO, and C 18O transitions of 35 Herbig disks within 450 pc, the masses were determined using the thermo-chemical code Dust And Lines (DALI). A grid of models was run spanning five orders of magnitude in disk mass, for which the model CO line luminosities could be linked to the observed luminosities. Survival analysis was used to obtain cumulative distributions of the resulting disk masses. These were compared with dust masses from previous work to obtain gas-to-dust ratios for each disk. In addition, radii for all three isotopologues were obtained. Results. The majority of Herbig disks for which 13CO and C18O were detected are optically thick in both. For these disks, the line flux essentially only traces the disk size and only lower limits to the mass can be obtained. Computing the gas mass using a simple optically thin relation between line flux and column density results in an underestimate of the gas mass of at least an order of magnitude compared to the masses obtained with DALI. The inferred gas masses with DALI are consistent with a gas-to-dust ratio of at least 100. These gas-to-dust ratios are two orders of magnitude higher compared to those found for T Tauri disks using similar techniques, even over multiple orders of magnitude in dust mass, illustrating the importance of the chemical conversion of CO in colder T Tauri disks. Similar high gas-to-dust ratios are found for Herbig group I and II disks. Since group II disks have dust masses comparable to T Tauri disks, their higher CO gas masses illustrate the determining role of temperature. Compared to debris disks, Herbig disks have gas masses higher by four orders of magnitude. At least one Herbig disk, HD 163296, has a detected molecular disk wind, but our investigation has not turned up other detections of the CO disk wind in spite of similar sensitivities. Conclusions. Herbig disks are consistent with a gas-to-dust ratio of at least 100 over multiple orders of magnitude in dust mass. This indicates a fundamental difference between CO emission from Herbig disks and T Tauri disks, which is likely linked to the warmer temperature of the Herbig disks.

Astrochemical Diagnostics of the Isolated Massive Protostar G28.20-0.05

We study the astrochemical diagnostics of the isolated massive protostar G28.20-0.05. We analyze data from Atacama Large Millimeter/submillimeter Array 1.3 mm observations with a resolution of 0.″2 (∼1000 au). We detect emission from a wealth of species, including oxygen-bearing (e.g., H2CO, CH3OH, CH3OCH3), sulfur-bearing (SO2, H2S), and nitrogen-bearing (e.g., HNCO, NH2CHO, C2H3CN, C2H5CN) molecules. We discuss their spatial distributions, physical conditions, correlation between different species, and possible chemical origins. In the central region near the protostar, we identify three hot molecular cores (HMCs). HMC1 is part of a millimeter continuum ring-like structure, is closest in projection to the protostar, has the highest temperature of ∼300 K, and shows the most line-rich spectra. HMC2 is on the other side of the ring, has a temperature of ∼250 K, and is of intermediate chemical complexity. HMC3 is further away, ∼3000 au in projection, cooler (∼70 K), and is the least line-rich. The three HMCs have similar mass surface densities (∼10 g cm−2), number densities (n H ∼ 109 cm−3), and masses of a few solar masses. The total gas mass in the cores and in the region out to 3000 au is ∼25 M ⊙, which is comparable to that of the central protostar. Based on spatial distributions of peak line intensities as a function of excitation energy, we infer that the HMCs are externally heated by the protostar. We estimate column densities and abundances of the detected species and discuss the implications for hot core astrochemistry.

The Structure and Composition of Multiphase Galactic Winds in a Large Magellanic Cloud Mass Simulated Galaxy

We present the first results from a high-resolution simulation with a focus on galactic wind driving for an isolated galaxy with a halo mass of ∼1011 M ⊙ (similar to the Large Magellanic Cloud) and a total gas mass of ∼6 × 108 M ⊙, resulting in ∼108 gas cells at ∼4 M ⊙ mass resolution. We adopt a resolved stellar feedback model with nonequilibrium cooling and heating, including photoelectric heating and photoionizing radiation, as well as supernovae, coupled to the second-order meshless finite-mass method for hydrodynamics. These features make this the largest resolved interstellar medium (ISM) galaxy model run to date. We find mean star formation rates around 0.05 M ⊙ yr−1 and evaluate typical time-averaged loading factors for mass (η M ∼ 1.0, in good agreement with recent observations) and energy (η E ∼ 0.01). The bulk of the mass of the wind is transported by the warm (T < 5 × 105 K) phase, while there is a similar amount of energy transported in the warm and the hot phases (T > 5 × 105 K). We find an average opening angle of 30° for the wind, decreasing with higher altitude above the midplane. The wind mass loading is decreasing (flat) for the warm (hot) phase as a function of the star formation surface rate density ΣSFR, while the energy loading shows inverted trends with ΣSFR, decreasing for the warm wind and increasing for the hot wind, although with very shallow slopes. These scalings are in good agreement with previous simulations of resolved wind driving in the multiphase ISM.

Starbursts driven by central gas compaction

ABSTRACT Starburst (SB) galaxies are a rare population of galaxies with star formation rates (SFRs) greatly exceeding those of the majority of star-forming galaxies with similar stellar mass. It is unclear whether these bursts are the result of either especially large gas reservoirs or enhanced efficiencies in converting gas into stars. Tidal torques resulting from gas-rich galaxy mergers are known to enhance the SFR by funnelling gas towards the centre. However, recent theoretical works show that mergers do not always trigger an SB and not all SB galaxies are interacting systems, raising the question of what drives an SB. We analyse a large sample of SB galaxies and a mass- and redshift-matched sample of control galaxies, drawn from the FIREbox cosmological volume at z = 0–1. We find that SB galaxies have both larger molecular gas fractions and shorter molecular depletion times than control galaxies, but similar total gas masses. Control galaxies evolve towards the SB regime by gas compaction in their central regions, over time-scales of ∼70 Myr, accompanied by an increase in the fraction of ultradense and molecular gas. The driving mechanism behind the SB varies depending on the mass of the galaxy. Massive ($M_\star \gtrsim 10^{10}~\rm {M}_\odot$) galaxies undergoing intense, long-lasting SBs are mostly driven by galaxy interactions. Conversely, SBs in non-interacting galaxies are often triggered by a global gravitational instability, which can result in a ‘breathing’ mode in low-mass galaxies.

Quasar feedback survey: molecular gas affected by central outflows and by ∼10-kpc radio lobes reveal dual feedback effects in ‘radio quiet’ quasars

ABSTRACT We present a study of molecular gas, traced via CO (3–2) from Atacama Large Millimeter/submillimeter Array data, of four z &amp;lt; 0.2, ‘radio quiet’, type 2 quasars (Lbol ∼ 1045.3–1046.2 erg s−1; L$_{\mathrm{1.4\, GHz}}\sim 10^{23.7}\!-\!10^{24.3}$ W Hz−1). Targets were selected to have extended radio lobes (≥ 10 kpc), and compact, moderate-power jets (1–10 kpc; Pjet ∼ 1043.2–1043.7 erg s−1). All targets show evidence of central molecular outflows, or injected turbulence, within the gas discs (traced via high-velocity wing components in CO emission-line profiles). The inferred velocities (Vout = 250–440 km s−1) and spatial scales (0.6–1.6 kpc), are consistent with those of other samples of luminous low-redshift active galactic nuclei. In two targets, we observe extended molecular gas structures beyond the central discs, containing 9–53 per cent of the total molecular gas mass. These structures tend to be elongated, extending from the core, and wrap-around (or along) the radio lobes. Their properties are similar to the molecular gas filaments observed around radio lobes of, mostly ‘radio loud’, brightest cluster galaxies. They have the following: projected distances of 5–13 kpc; bulk velocities of 100–340 km s−1; velocity dispersion of 30–130 km s−1; inferred mass outflow rates of 4–20 M⊙ yr−1; and estimated kinetic powers of 1040.3–1041.7 erg s−1. Our observations are consistent with simulations that suggest moderate-power jets can have a direct (but modest) impact on molecular gas on small scales, through direct jet–cloud interactions. Then, on larger scales, jet-cocoons can push gas aside. Both processes could contribute to the long-term regulation of star formation.