Atacama Large Millimeter Array Observations Research Articles

Testing Primordial Black Hole Dark Matter with Atacama Large Millimeter Array Observations of the Gravitational Lens B1422+231

We examine the flux density ratio anomaly in the quadruply imaged strong gravitational lens, B1422+231, and consider the contribution of 10–103M⊙ primordial black holes (PBHs) as a potential dark matter constituent. We describe the first flux density ratio measurement of B1422+231 in the millimeter-wave band using the Atacama Large Millimeter Array (ALMA). The flux density of the quasar at 233 GHz is dominated by synchrotron emission and the source size is estimated to be less than 66.9 pc. The observed flux density ratios at 233 GHz are similar to those measured in other wave bands, which cannot be explained by a simple smooth mass model of the lens galaxy. We examine the probability of the flux density ratio anomaly arising from PBH microlensing using ray tracing simulations. The simulations consider the cases where 10% and 50% of dark matter are 10–103M⊙ PBHs with a power law mass function. The simulated scenarios are consistent with the ALMA observations, so PBH dark matter cannot be ruled out as a cause of flux density ratio anomalies. Our analysis shows that the anomalous flux density ratio for B1422+231 can be explained by a lens model with a significant fraction of dark matter being PBHs. This study demonstrates the potential for new constraints on PBH dark matter using ALMA observations of multiply imaged strong gravitational lenses.

FAUST

Context. Deuterium in H-bearing species is enhanced during the early stages of star formation. However, only a small number of high-spatial-resolution deuteration studies exist towards protostellar objects, leaving the small-scale structures of these objects unrevealed and understudied. Aims. We aim to constrain the deuterium fractionation ratios in a Class 0/I protostellar object in formaldehyde (H2CO), which has abundant deuterated isotopologues in this environment. Methods. We used the Atacama Large Millimeter Array (ALMA) within the context of the Large Program Fifty AU STudy of the chemistry in the disk/envelope system of Solar-like protostars (FAUST) to observe the Class 0/I protobinary system [BHB2007] 11, whose emission components are embedded in circumstellar disks that have radii of 2 to 3 au. The system is surrounded by a complex filamentary structure (the so-called streamers) connected to the larger circumbinary disk. In this work, we present the first study of formaldehyde D-fractionation towards this source with detections of H2CO 3(0,3)–2(0,2), combined with HDCO 4(2,2)–3(2,1), HDCO 4(1,4)–3(1,3) and D2CO 4(0,4)–3(0,3). These observations probe the structures of the protobinary system, enabling us to resolve multiple velocity components associated with the methanol hot spots also uncovered by FAUST data, as well as the colder external envelope. In addition, based on the kinematics seen in our observations of the H2CO emission, we propose the presence of a second large-scale outflow. Results. The results derived from our ALMA observations agree with the current literature in that we only find the deuterated species HDCO and D2CO in the central regions of the core, while undeuterated H2CO is found more ubiquitously. From our radiative transfer modelling, we the column density of H2CO to be in the range of (3-8) × 1014 cm−2 and that of HDCO to be within (0.8−2.9) × 1013 cm−2. The column density for the single detected velocity component of D2CO is within (2.6–1.3) × 1012 cm−2. This yields an average D/H ratio for formaldehyde in [BHB2007] 11 of $0.02_{ - 0.01}^{ + 0.02}$ from HDCO. The results of our kinematic model suggest that the dynamic feature is inconsistent with a streamer-like nature given the flat and outflowing velocity relation; we therefore tentatively conclude that the feature is an asymmetric molecular outflow launched by a wide-angle disk wind.

The ALMA REBELS Survey: the first infrared luminosity function measurement at z ∼ 7

ABSTRACT We present the first observational infrared luminosity function (IRLF) measurement in the Epoch of Reionization (EoR) based on a ultraviolet (UV)-selected galaxy sample with the Atacama Large Millimeter Array (ALMA) spectroscopic observations. Our analysis is based on the ALMA large program Reionization Era Bright Emission Line Survey (REBELS), which targets 42 galaxies at z = 6.4–7.7 with [C ii] 158 $\rm{\mu m}$ line scans. 16 sources exhibit dust detection, 15 of which are also spectroscopically confirmed through the [C ii] line. The infrared (IR) luminosities of the sample range from log LIR/L⊙ = 11.4 to 12.2. Using the UV luminosity function as a proxy to derive the effective volume for each of our target sources, we derive IRLF estimates, both for detections and for the full sample including IR luminosity upper limits. The resulting IRLFs are well reproduced by a Schechter function with the characteristic luminosity of $\log L_{*}/\mathrm{ L}_\odot =11.6^{+0.2}_{-0.1}$ . Our observational results are in broad agreement with the average of predicted IRLFs from simulations at z ∼ 7. Conversely, our IRLFs lie significantly below lower redshift estimates, suggesting a rapid evolution from z ∼ 4 to z ∼ 7, into the reionization epoch. The IR obscured contribution to the cosmic star formation rate density at z ∼ 7 amounts to $\mathrm{log(SFRD/{\rm M}_{\odot }\,yr^{-1}\,Mpc^{-3}) = -2.66^{+0.17}_{-0.14} }$ that is at least ∼10 per cent of UV-based estimates. We conclude that the presence of dust is already abundant in the EoR and discuss the possibility of unveiling larger samples of dusty galaxies with future ALMA and JWST observations.

JWST’s PEARLS: A JWST/NIRCam View of ALMA Sources

We report the results of James Webb Space Telescope/NIRCam observations of 19 (sub)millimeter sources detected by the Atacama Large Millimeter Array (ALMA). The accurate ALMA positions allowed unambiguous identifications of their NIRCam counterparts. Taking gravitational lensing into account, these represent 16 distinct galaxies in three fields and constitute the largest sample of its kind to date. The counterparts’ spectral energy distributions cover from rest-frame ultraviolet to near-IR and provide photometric redshifts (1 < z < 4.5) and stellar masses (M * > 1010.5 M ⊙), which are similar to submillimeter galaxies (SMGs) studied previously. However, our sample is fainter in (sub)millimeter than the classic SMG samples are, and our sources exhibit a wider range of properties. They have dust-embedded star formation rates as low as 10 M ⊙ yr−1, and the sources populate both the star-forming main sequence and the quiescent categories. The deep NIRCam data allow us to study the rest-frame near-IR morphologies. Excluding two multiply imaged systems and one quasar, the majority of the remaining sources are disk-like and show either little or no disturbance. This suggests that secular growth is a potential route for the assembly of high-mass disk galaxies. While a few objects have large disks, the majority have small disks (median half-mass radius of 1.6 kpc). At this time, it is unclear whether this is due to the prevalence of small disks at these redshifts or some unknown selection effects of deep ALMA observations. A larger sample of ALMA sources with NIRCam observations will be able to address this question.

Razor-thin dust layers in protoplanetary disks: Limits on the vertical shear instability

Context. Recent observations with the Atacama Large Millimeter Array (ALMA) have shown that the large dust aggregates observed at millimeter wavelengths settle to the midplane into a remarkably thin layer. This sets strong limits on the strength of the turbulence and other gas motions in these disks. Aims. We intend to find out if the geometric thinness of these layers is evidence against the vertical shear instability (VSI) operating in these disks. We aim to verify if a dust layer consisting of large enough dust aggregates could remain geometrically thin enough to be consistent with the latest observations of these dust layers, even if the disk is unstable to the VSI. If this is falsified, then the observed flatness of these dust layers proves that these disks are stable against the VSI, even out to the large radii at which these dust layers are observed. Methods. We performed hydrodynamic simulations of a protoplanetary disk with a locally isothermal equation of state, and let the VSI fully develop. We sprinkled dust particles with a given grain size at random positions near the midplane and followed their motion as they got stirred up by the VSI, assuming no feedback onto the gas. We repeated the experiment for different grain sizes and determined for which grain size the layer becomes thin enough to be consistent with ALMA observations. We then verified if, with these grain sizes, it is still possible (given the constraints of dust opacity and gravitational stability) to generate a moderately optically thick layer at millimeter wavelengths, as observations appear to indicate. Results. We found that even very large dust aggregates with Stokes numbers close to unity get stirred up to relatively large heights above the midplane by the VSI, which is in conflict with the observed geometric thinness. For grains so large that the Stokes number exceeds unity, the layer can be made to remain thin, but we show that it is hard to make dust layers optically thick at ALMA wavelengths (e.g., τ1.3mm ≳ 1) with such large dust aggregates. Conclusions. We conclude that protoplanetary disks with geometrically thin midplane dust layers cannot be VSI unstable, at least not down to the disk midplane. Explanations for the inhibition of the VSI out to several hundreds of au include a high dust-to-gas ratio of the midplane layer, a modest background turbulence, and/or a reduced dust-to-gas ratio of the small dust grains that are responsible for the radiative cooling of the disk. A reduction of small grains by a factor of between 10 and 100 is sufficient to quench the VSI. Such a reduction is plausible in dust growth models, and still consistent with observations at optical and infrared wavelengths.

An ALMA Search for High-albedo Objects Among the Midsized Jupiter Trojan Population

We use Atacama Large Millimeter Array (ALMA) measurements of 870 μm thermal emission from a sample of midsized (15–40 km diameter) Jupiter Trojan asteroids to search for high-albedo objects in this population. We calculate the diameters and albedos of each object using a thermal model which also incorporates contemporaneous Zwicky Transient Facility photometry to accurately measure the absolute magnitude at the time of the ALMA observation. We find that while many albedos are lower than reported from WISE, several small Trojans have high albedos independently measured both from ALMA and from WISE. The number of these high-albedo objects is approximately consistent with expectations of the number of objects that recently have undergone large-scale impacts, suggesting that the interiors of freshly-crated Jupiter Trojans could contain high-albedo materials such as ices.

Protostellar discs subject to infall: a one-dimensional inviscid model and comparison with ALMA observations

ABSTRACT A new one-dimensional, inviscid, and vertically integrated disc model with prescribed infall is presented. The flow is computed using a second-order shock-capturing scheme. Included are vertical infall, radial infall at the outer radial boundary, radiative cooling, stellar irradiation, and heat addition at the disc-surface shock. Simulation parameters are chosen to target the L1527 IRS disc which has been observed using Atacama Large Millimeter Array (ALMA). The results give an outer envelope of radial infall and uϕ ∝ 1/r which encounters a radial shock at rshock ∼ 1.5 × the centrifugal radius (rc) across which the radial velocity is greatly reduced and the gas temperature rises from a pre-shock value of ≈25 to ≈180 K over a spatially thin region calculated using a separate shock structure code. At rc, the azimuthal velocity uϕ transitions from being ∝ 1/r to being nearly Keplerian. These results qualitatively agree with recent ALMA observations which indicate a radial shock where SO is sublimated as well as a transition from a uϕ ∼ 1/r region to a Keplerian inner disc. However, in one set of observations, the observed position-velocity map of cyclic-C3H2, together with a certain ballistic maximum velocity relation suggests that the radial shock coincides with a ballistic centrifugal barrier, which places the shock at rshock = 0.5rc, i.e. inward of rc, rather than outward as given by our simulations. It is argued that radial velocity plots from previous magnetic rotating-collapse simulations also indicate that the radial shock is located outward of rc. The discrepancy with observations is analysed and discussed, but remains unresolved.

A Twin-jet Structure Rather than Jet Rotation in the Young Stellar Object OMC 2/FIR 6b

Abstract We analyze recent high-quality Atacama Large Millimeter Array (ALMA) molecular line mapping observations of the northeast jet of the young stellar object (YSO) OMC 2/FIR 6b (HOPS-60) and find that these ALMA observations are much more likely to indicate a twin-jet structure than jet rotation, as previously hypothesized. The interpretation of the line-of-sight velocity gradient across (perpendicular to its axis) the northeast jet of Fir 6b in terms of jet rotation leads to jet-launching radii of ≃2–3 au. However, the velocities of the jets ≃100–400 km s−1 are much larger than the escape speed from these radii. We argue that the northeast jet of FIR 6b is instead compatible with a twin-jet structure, as observed in some planetary nebulae. Specifically, we find that the main, redshifted jet emanating from the central YSO is composed of two, very closely aligned, narrower jets that were launched by the central YSO at about the same time but at different inclinations with respect to the plain of the sky. This twin-jet structure removes the extreme requirement that jets with velocities similar to the escape velocity from the YSO be launched from very large radii. The YSO FIR 6b and certain planetary nebulae also share the characteristics of unequal structures and intensities of their two opposing bipolar jets. We propose that such opposing lobe asymmetries can result from a substellar binary companion on an eccentric orbit that is inclined to the accretion disk plane.

The Galaxy Activity, Torus, and Outflow Survey (GATOS)

We present the first results of the Galaxy Activity, Torus, and Outflow Survey (GATOS), a project aimed at understanding the properties of the dusty molecular tori and their connection to the host galaxy in nearby Seyfert galaxies. Our project expands the range of active galactic nuclei (AGN) luminosities and Eddington ratios covered by previous surveys of Seyferts conducted by the Atacama Large Millimeter Array (ALMA), allowing us to study the gas feeding and feedback cycle in a combined sample of 19 Seyferts. We used ALMA to obtain new images of the emission of molecular gas and dust using the CO(3–2) and HCO+(4–3) lines as well as their underlying continuum emission at 870 μm with high spatial resolutions (0.1″ ∼ 7 − 13 pc) in the circumnuclear disks (CND) of ten nearby (D &lt; 28 Mpc) Seyfert galaxies selected from an ultra-hard X-ray survey. Our new ALMA observations detect 870 μm continuum and CO line emission from spatially resolved disks located around the AGN in all the sources. The bulk of the 870 μm continuum flux can be accounted for by thermal emission from dust in the majority of the targets. For most of the sources, the disks show a preponderant orientation perpendicular to the AGN wind axes, as expected for dusty molecular tori. The median diameters and molecular gas masses of the tori are ∼42 pc and ∼6 × 105 M⊙, respectively. We also detected the emission of the 4–3 line of HCO+in four GATOS targets. The order of magnitude differences found in the CO/HCO+ratios within our combined sample point to a very different density radial stratification inside the dusty molecular tori of these Seyferts. We find a positive correlation between the line-of-sight gas column densities responsible for the absorption of X-rays and the molecular gas column densities derived from CO toward the AGN in our sources. Furthermore, the median values of both column densities are similar. This suggests that the neutral gas line-of-sight column densities of the dusty molecular tori imaged by ALMA significantly contribute to the obscuration of X-rays. The radial distributions of molecular gas in the CND of our combined sample show signs of nuclear-scale molecular gas deficits. We also detect molecular outflows in the sources that show the most extreme nuclear-scale gas deficits in our sample. These observations find for the first time supporting evidence that the imprint of AGN feedback is more extreme in higher luminosity and/or higher Eddington ratio Seyfert galaxies.

Characterizing the dust content of disk substructures in TW Hydrae

Context. A key piece of information to understand the origin and role of protoplanetary disk substructures is their dust content. In particular, disk substructures associated with gas pressure bumps can work as dust traps, accumulating grains and reaching the necessary conditions to trigger the streaming instability. Aims. In order to shed some light on the origin and role that disk substructures play in planet formation, we aim to characterize the dust content of substructures in the disk of TW Hya. Methods. We present Atacama Large Millimeter Array (ALMA) observations of TW Hya at 3.1 mm with ~50 milliarcsecond resolution. These new data were combined with archival high angular resolution ALMA observations at 0.87, 1.3, and 2.1 mm. We analyze these multiwavelength data to infer a disk radial profile of the dust surface density, maximum particle size, and slope of the particle size distribution. Results. Most previously known annular substructures in the disk of TW Hya are resolved at the four wavelengths. Inside the inner 3 au cavity, the 2.1 and 3.1 mm images show a compact source of free–free emission, likely associated with an ionized jet. Our multiwavelength analysis of the dust emission shows that the maximum particle size in the disk of TW Hya is &gt;1 mm. The inner 20 au are completely optically thick at all four bands, which results in the data tracing different disk heights at different wavelengths. Coupled with the effects of dust settling, this prevents the derivation of accurate density and grain size estimates in these regions. At r &gt; 20 au, we find evidence of the accumulation of large dust particles at the position of the bright rings, indicating that these are working as dust traps. The total dust mass in the disk is between 250 and 330 M⊕, which represents a gas-to-dust mass ratio between 50 and 70. Our mass measurement is a factor of 4.5–5.9 higher than the mass that one would estimate using the typical assumptions of large demographic surveys. Conclusions. Our results indicate that the ring substructures in TW Hya are ideal locations to trigger the streaming instability and form new generations of planetesimals.

Dynamical model of an obscuring clumpy torus in AGNs – I. Velocity and velocity dispersion maps for interpretation of ALMA observations

ABSTRACT We have developed the dynamical model of a clumpy torus in an active galactic nucleus (AGN) and compared to recent The Atacama Large Millimeter Array (ALMA) observations. We present N-body simulations of a torus in the field of a supermassive black hole (SMBH), made of up to N = 105 gravitationally interacting clouds. As initial conditions, we choose random distributions of the orbital elements of the clouds with a cut-off in the inclination to mimic the presence of wind cones produced at the early AGN stage. When the torus reaches an equilibrium, it has a doughnut shape. We discuss the presence of box orbits. We have then constructed the velocity and velocity dispersion maps using the resulting distributions of the clouds at equilibrium. The effects of torus inclination and cloud sizes are duly analysed. We discuss the obscuration effects of the clouds using a ray tracing simulation matching the model maps to ALMA resolution. By comparing the model with the observational maps of NGC 1068, we find that the SMBH mass is $M_\text{smbh}=5\times 10^6 \, \mathrm{M}_\odot$ for the range of the torus inclination angles 45°–60°. We also construct the velocity dispersion maps for NGC 1326 and NGC 1672. They show that the peaks in the ALMA dispersion maps are related to the emission of the torus throat. Finally, we obtain the temperature distribution maps with parameters that correspond to our model velocity maps for NGC 1068. They show stratification in temperature distribution with the shape of the high-temperature region as in the VLTI/MIDI map.

ALMA and VLA Observations of EX Lupi in Its Quiescent State

Abstract Extreme outbursts in young stars may be a common stage of pre-main-sequence stellar evolution. These outbursts, caused by enhanced accretion and accompanied by increased luminosity, can also strongly impact the evolution of the circumstellar environment. We present Atacama Large Millimeter Array (ALMA) and Very Large Array observations of EX Lupi, a prototypical outburst system, at 100, 45, and 15 GHz. We use these data, along with archival ALMA 232 GHz data, to fit radiative transfer models to EX Lupi’s circumstellar disk in its quiescent state following the extreme outburst in 2008. The best-fit models show a compact disk with a characteristic dust radius of 45 au and a total mass of 0.01 M ⊙. Our modeling suggests grain growth to sizes of at least 3 mm in the disk, possibly spurred by the recent outburst, and an ice line that has migrated inward to 0.2–0.3 au post-outburst. At 15 GHz, we detected significant emission over the expected thermal disk emission which we attribute primarily to stellar (gyro)synchrotron and free–free disk emission. Altogether, these results highlight what may be a common impact of outbursts on the circumstellar dust.

ALMaQUEST. IV. The ALMA-MaNGA QUEnching and STar Formation (ALMaQUEST) Survey

Abstract The ALMaQUEST (ALMA-MaNGA QUEnching and STar formation) survey is a program with spatially resolved 12CO(1−0) measurements obtained with the Atacama Large Millimeter Array (ALMA) for 46 galaxies selected from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) DR15 optical integral-field spectroscopic survey. The aim of the ALMaQUEST survey is to investigate the dependence of star formation activity on the cold molecular gas content at kiloparsec scales in nearby galaxies. The sample consists of galaxies spanning a wide range in specific star formation rate (sSFR), including starburst (SB), main-sequence (MS), and green valley (GV) galaxies. In this paper, we present the sample selection and characteristics of the ALMA observations and showcase some of the key results enabled by the combination of spatially matched stellar populations and gas measurements. Considering the global (aperture-matched) stellar mass, molecular gas mass, and star formation rate of the sample, we find that the sSFR depends on both the star formation efficiency (SFE) and the molecular gas fraction ( ), although the correlation with the latter is slightly weaker. Furthermore, the dependence of sSFR on the molecular gas content (SFE or ) is stronger than that on either the atomic gas fraction or the molecular-to-atomic gas fraction, albeit with the small Hi sample size. On kiloparsec scales, the variations in both SFE and within individual galaxies can be as large as 1–2 dex, thereby demonstrating that the availability of spatially resolved observations is essential to understand the details of both star formation and quenching processes.

Is the gap in the DS Tau disc hiding a planet?

ABSTRACT Recent millimetre-wavelength surveys performed with the Atacama Large Millimeter Array (ALMA) have revealed protoplanetary discs characterized by rings and gaps. A possible explanation for the origin of such rings is the tidal interaction with an unseen planetary companion. The protoplanetary disc around DS Tau shows a wide gap in the ALMA observation at 1.3 mm. We construct a hydrodynamical model for the dust continuum observed by ALMA assuming the observed gap is carved by a planet between one and five Jupiter masses. We fit the shape of the radial intensity profile along the disc major axis varying the planet mass, the dust disc mass, and the evolution time of the system. The best-fitting model is obtained for a planet with $M_{\rm p}=3.5\, \mathrm{ M}_{\rm Jup}$ and a disc with $M_{\rm dust}= 9.6\,\times \,10^{-5}\, \mathrm{ M}_{\odot }$. Starting from this result, we also compute the expected signature of the planet in the gas kinematics, as traced by CO emission. We find that such a signature (in the form of a ‘kink’ in the channel maps) could be observed by ALMA with a velocity resolution between $0.2-0.5\, \rm {kms}^{-1}$ and a beam size between 30 and 50 mas.

The ALMA view of the high-redshift relation between supermassive black holes and their host galaxies

Context. The existence of tight correlations between supermassive black holes (BHs) and their host galaxies’ properties in the local Universe suggests a closely linked evolution. Investigating these relations up to the high redshifts (z ≳ 6) is crucial in order to understand the interplay between star formation and BH growth across the cosmic time and to set constraints on galaxy formation and evolution models. In this work, we focus on the relation between BH mass (MBH) and the dynamical mass (Mdyn) of the host galaxy. Aims. Previous works suggest an evolution of the MBH−Mdyn relation with redshift indicating that BH growth precedes the galaxy mass assembly during their co-evolution at z &gt; 3. However, dynamical galaxy masses at high redshift are often estimated through the virial theorem, thus introducing significant uncertainties. Within the scope of this work, our aim is to study the MBH−Mdyn relation of a sample of 2 &lt; z &lt; 7 quasars by constraining their galaxy masses through a full kinematical modelling of the cold gas kinematics, thus avoiding all possible biases and effects introduced by the rough estimates usually adopted so far. Methods. For this purpose, we retrieved public observations of 72 quasar host galaxies observed in [CII]158 μm or CO transitions with the Atacama Large Millimeter Array (ALMA). We then selected those quasars whose line emission is spatially resolved, and performed a kinematic analysis on ALMA observations. We estimated the dynamical mass of the systems by modelling the gas kinematics with a rotating disc, taking into account geometrical and instrumental effects. Our dynamical mass estimates, combined with MBH obtained from literature and our own new CIVλ1550 observations allowed us to investigate the MBH/Mdyn in the early Universe. Results. Overall, we obtained a sample of ten quasars at z ∼ 2−7, in which line emission is detected with high S/N (≳5−10) and the gas kinematics are spatially resolved and dominated by ordered rotation. The estimated dynamical masses place six out of ten quasars above the local relation yielding to MBH/Mdyn ratios ∼10× higher than those estimated in low-z galaxies. On the other hand, we found that four quasars at z ∼ 4−6 have dynamical-to-BH-mass ratios consistent with what is observed in early-type galaxies in the local Universe.

ALMA reveals a large structured disk and nested rotating outflows in DG Tauri B

We present Atacama Large Millimeter Array (ALMA) Band 6 observations at 14−20 au spatial resolution of the disk and CO(2-1) outflow around the Class I protostar DG Tau B in Taurus. The disk is very large, both in dust continuum (Reff, 95% = 174 au) and CO (RCO = 700 au). It shows Keplerian rotation around a 1.1 ± 0.2 M⊙ central star and two dust emission bumps at r = 62 and 135 au. These results confirm that large structured disks can form at an early stage where residual infall is still ongoing. The redshifted CO outflow at high velocity shows a striking hollow cone morphology out to 3000 au with a shear-like velocity structure within the cone walls. These walls coincide with the scattered light cavity, and they appear to be rooted within &lt; 60 au in the disk. We confirm their global average rotation in the same sense as the disk, with a specific angular momentum ≃65 au km s−1. The mass-flux rate of 1.7−2.9 × 10−7 M⊙ yr−1 is 35 ± 10 times that in the atomic jet. We also detect a wider and slower outflow component surrounding this inner conical flow, which also rotates in the same direction as the disk. Our ALMA observations therefore demonstrate that the inner cone walls, and the associated scattered light cavity, do not trace the interface with infalling material, which is shown to be confined to much wider angles (&gt; 70°). The properties of the conical walls are suggestive of the interaction between an episodic inner jet or wind with an outer disk wind, or of a massive disk wind originating from 2 to 5 au. However, further modeling is required to establish their origin. In either case, such massive outflow may significantly affect the disk structure and evolution.

A spectral stacking analysis to search for faint outflow signatures inz∼ 6 quasars

Aims.Outflows in quasars during the early epochs of galaxy evolution are an important part of the feedback mechanisms that potentially affect the evolution of the host galaxy. However, systematic millimetre (mm) observations of outflows are only now becoming possible with the advent of sensitive mm telescopes. In this study we used spectral stacking methods to search for a faint high-velocity outflow signal in a sample of [C II] detected,z ∼ 6 quasars.Methods.We searched for broad emission line signatures from high-velocity outflows for a sample of 26z ∼ 6 quasars observed with the Atacama Large Millimeter Array (ALMA), with a detection of the [C II] line. The observed emission lines of the sources are dominated by the host galaxy, and outflow emission is not detected for the individual sources. We used a spectral line stacking analysis developed for interferometric data to search for outflow emission. We stacked both extracted spectra and the full spectral cubes. We also investigated the possibility that only a sub-set of our sample contributes to the stacked outflow emission.Results.We find only a tentative detection of a broad emission line component in the stacked spectra. When taking a region of about 2″ around the central position of the stacked cubes, the stacked line shows an excess emission due to a broad component of 1.1–1.5σ, but the significance drops to 0.4–0.7σwhen stacking the extracted spectra from a smaller region. The broad component can be characterised by a line width of full width at half-maximumFWHM &gt; 700 km s−1. Furthermore, we find a sub-sample of 12 sources, the stack of which maximises the broad component emission. The stack of this sub-sample shows an excess emission due to a broad component of 1.2–2.5σ. The stacked line of these sources has a broad component ofFWHM &gt; 775 km s−1.Conclusions.We find evidence suggesting the presence of outflows in a sub-sample of 12 out of 26 sources, which demonstrates the importance of spectral stacking techniques in tracing faint signal in galaxy samples. However, deeper ALMA observations are necessary to confirm the presence of a broad component in the individual spectra.

ALMA observations of A0620–00: fresh clues on the nature of quiescent black hole X-ray binary jets

ABSTRACT We report on Atacama Large Millimeter Array (ALMA) continuum observations of the black hole X-ray binary A0620–00 at an X-ray luminosity nine orders of magnitude sub-Eddington. The system was significantly detected at 98 GHz (at 44 ± 7 $\mu$Jy) and only marginally at 233 GHz (20 ± 8 $\mu$Jy), about 40 d later. These results suggest either an optically thin sub-mm synchrotron spectrum, or highly variable sub-mm jet emission on month time-scales. Although the latter appears more likely, we note that, at the time of the ALMA observations, A0620–00 was in a somewhat less active optical-IR state than during all published multiwavelength campaigns when a flat-spectrum, partially self-absorbed jet has been suggested to extend from the radio to the mid-IR regime. Either interpretation is viable in the context of an internal shock model, where the jet’s spectral shape and variability are set by the power density spectrum of the shells’ Lorentz factor fluctuations. While strictly simultaneous radio–mm-IR observations are necessary to draw definitive conclusions for A0620–00, the data presented here, in combination with recent radio and sub-mm results from higher luminosity systems, demonstrate that jets from black hole X-ray binaries exhibit a high level of variability – either in flux density or intrinsic spectral shape, or both – across a wide spectrum of Eddington ratios. This is not in contrast with expectations from an internal shock model, where lower jet power systems can be expected to exhibit larger fractional variability owing to an overall decrease in synchrotron absorption.

One Solution to the Mass Budget Problem for Planet Formation: Optically Thick Disks with Dust Scattering

Abstract Atacama Large Millimeter Array (ALMA) surveys have suggested that the dust in Class II disks may not be enough to explain the averaged solid mass in exoplanets, under the assumption that the mm disk continuum emission is optically thin. This optically thin assumption seems to be supported by recent Disk Substructures at High Angular Resolution Project (DSHARP) observations where the measured optical depths are mostly less than one. However, we point out that dust scattering can considerably reduce the emission from an optically thick region. If that scattering is ignored, an optically thick disk with scattering can be misidentified as an optically thin disk. Dust scattering in more inclined disks can reduce the intensity even further, making the disk look even fainter. The measured optical depth of ∼0.6 in several DSHARP disks can be naturally explained by optically thick dust with an albedo of ∼0.9 at 1.25 mm. Using the DSHARP opacity, this albedo corresponds to a dust population with the maximum grain size (s max) of 0.1–1 mm. For optically thick scattering disks, the measured spectral index α can be either larger or smaller than 2 depending on whether the dust albedo increases or decreases with wavelength. We describe how this optically thick scattering scenario could explain the observed scaling between submm continuum sizes and luminosities, and might help ease the tension between the dust size constraints from polarization and dust continuum measurements. We suggest that a significant amount of disk mass can be hidden from ALMA observations and longer wavelength observations (e.g., Very Large Array or Square Kilometre Array) are desired to probe the dust mass in disks.

Environmental Effect on the Interstellar Medium in Galaxies across the Cosmic Web at z = 0.73

Abstract We present new Atacama Large Millimeter Array (ALMA) dust continuum observations of 101 galaxies in the COSMOS field to study the effect of the environment on the interstellar medium at z ∼ 0.7. At this redshift, our targets span a wide range of environments allowing for a diverse sample of galaxies with densities of Σ = 0.16–10.5 Mpc−2 (per Δz = 0.024). Using the ALMA observations, we calculate the total interstellar medium (ISM) mass (M ISM) and look for depletion as a function of galaxy density in order to understand the quenching or triggering of star formation in galaxies in different environments. M ISM is found to have a small dependence on the environment, while the depletion timescale remains constant (∼200 Myr) across all environments. We find elevated M ISM values at intermediate densities and lower values at high densities compared to low (field) densities. Our observed evolution in gas fraction with density in this single redshift slice is equivalent to the observed evolution with cosmic time over 2–3 Gyr. To explain the change in the gas mass fraction seen in galaxies in intermediate and high densities, these results suggest environmental processes such as mergers and ram pressure stripping are likely playing a role in dense filamentary cluster environments.