Atacama Large Millimeter/submillimeter Array Research Articles

ALMA 400 pc Imaging of a z = 6.5 Massive Warped Disk Galaxy

We present 0.″075 (≈400 pc) resolution Atacama Large Millimeter/submillimeter Array (ALMA) observations of the [C ii] and dust continuum emission from the host galaxy of the z = 6.5406 quasar, P036+03. We find that the emission arises from a thin, rotating disk with an effective radius of 0.″21 (1.1 kpc). The velocity dispersion of the disk is consistent with a constant value of 66.4 ± 1.0 km s−1, yielding a scale height of 80 ± 30 pc. The [C ii] velocity field reveals a distortion that we attribute to a warp in the disk. Modeling this warped disk yields an inclination estimate of 40.°4 ± 1.°3 and a rotational velocity of 116 ± 3 km s−1. The resulting dynamical mass estimate of (1.96 ± 0.10) × 1010 M ⊙ is lower than previous estimates, which strengthens the conclusion that the host galaxy is less massive than expected based on local scaling relations between the black hole mass and the host galaxy mass. Using archival MUSE Lyα observations, we argue that counterrotating halo gas could provide the torque needed to warp the disk. We further detect a region with excess (15σ) dust continuum emission, which is located 1.3 kpc northwest of the galaxy’s center and is gravitationally unstable (Toomre Q < 0.04). We posit this is a star-forming region whose formation was triggered by the warp because the region is located within a part of the warped disk where gas can efficiently lose angular momentum. The combined ALMA and MUSE imaging provides a unique view of how gas interactions within the disk–halo interface can influence the growth of massive galaxies within the first billion years of the Universe.

Cryogenic Systems for Astronomical Research in the Special Astrophysical Observatory of the Russian Academy of Sciences

This article presents the main results and new plans for the development of receivers which are cooled cryogenically to deep cryogenic temperatures and used in optical and radio astronomy research at the Special Astrophysical Observatory of the Russian Academy of Sciences (SAO RAS) on both the Big Telescope Alt-Azimuthal optical telescope (BTA) and the Radio Astronomical Telescope Academy of Sciences (RATAN-600) radio telescope, 600 m in diameter. These two instruments almost completely cover the frequency range from long radio waves to the IR and optical bands (0.25–8 mm on RATAN and 10–0.3 μm, on BTA) with a certain gap in the terahertz part (8–0.01 mm) of the spectrum. Today, this range is of the greatest interest for astronomers. In particular, the ALMA (Atacama Large Millimeter Array) observatory and the worldwide network of modern telescopes called the EVH (Event Horizon Telescope) operate in this range. New developments at SAO RAS are aimed at mastering this part of the spectrum. Cryogenic systems of receivers in these ranges are a key element of the system and differ markedly from the cooling systems of optical and radio receivers that ensure cooling of the receivers to sub-Kelvin temperatures.

Galactic ‘Snake’ IRDC G11.11−0.12: a site of multiple hub–filament systems and colliding filamentary clouds

ABSTRACT To probe star formation processes, we present a multiscale and multiwavelength investigation of the ‘Snake’ nebula/infrared dark cloud G11.11−0.12 (hereafter, G11; length ∼27 pc). Spitzer images hint at the presence of subfilaments (in absorption), and reveal four infrared-dark hub–filament system (HFS) candidates (extent &amp;lt; 6 pc) towards G11, where massive clumps (&amp;gt; 500 M⊙) and protostars are identified. The 13CO(2–1), C18O(2–1), and NH3(1,1) line data reveal a noticeable velocity oscillation towards G11, as well as its left part (or part-A) around Vlsr of 31.5 km s−1, and its right part (or part-B) around Vlsr of 29.5 km s−1. The common zone of these cloud components is investigated towards the centre of G11 housing one HFS. Each cloud component hosts two subfilaments. In comparison to part-A, more APEX Telescope Large Area Survey of the Galaxy (ATLASGAL) clumps are observed towards part-B. The JWST near-infrared images discover one infrared-dark HFS candidate (extent ∼0.55 pc) around the massive protostar G11P1 (i.e. G11P1-HFS). Hence, the infrared observations reveal multiple infrared-dark HFS candidates at multiscale in G11. The Atacama Large Millimeter/submillimeter Array (ALMA) 1.16-mm continuum map shows multiple finger-like features (extent ∼3500–10 000 au) surrounding a dusty envelope-like feature (extent ∼18 000 au) towards the central hub of G11P1-HFS. Signatures of forming massive stars are found towards the centre of the envelope-like feature. The ALMA H13CO+ line data show two cloud components with a velocity separation of ∼2 km s−1 towards G11P1. Overall, the collision process, the ‘fray and fragment’ mechanism, and the ‘global non-isotropic collapse’ scenario seem to be operational in G11.

Spatial Extent of Molecular Gas, Dust, and Stars in Massive Galaxies at z ∼ 2.2–2.5 Determined with ALMA and JWST

We present the results of 0.″6-resolution observations of CO J = 3 − 2 line emission in 10 massive star-forming galaxies at z ∼ 2.2–2.5 with the Atacama Large Millimeter/submillimeter Array (ALMA). We compare the spatial extent of molecular gas with those of dust and stars, traced by the 870 and 4.4 μm continuum emissions, respectively. The average effective radius of the CO emission is 1.75 ± 0.34 kpc, which is about 60% larger than that of the 870 μm emission and is comparable with that of the 4.4 μm emission. Utilizing the best-fit parametric models, we derive the radial gradients of the specific star formation rate (sSFR), gas depletion timescale, and gas-mass fraction within the observed galaxies. We find a more intense star formation activity with a higher sSFR and a shorter depletion timescale in the inner region than in the outer region. The central starburst may be the primary process for massive galaxies to build up a core. Furthermore, the gas-mass fraction is high, independent of the galactocentric radius in the observed galaxies, suggesting that the galaxies have not begun to quench star formation. Given the shorter gas depletion timescale in the center compared to the outer region, quenching is expected to occur in the center first and then propagate outward. We may be witnessing the observed galaxies in the formation phase of a core prior to the forthcoming phase of star formation propagating outward.

ALMA High-frequency Long Baseline Campaign in 2021: Highest Angular Resolution Submillimeter Wave Images for the Carbon-rich Star R Lep

The Atacama Large Millimeter/submillimeter Array (ALMA) was used in 2021 to image the carbon-rich evolved star R Lep in Bands 8–10 (397–908 GHz) with baselines up to 16 km. The goal was to validate the calibration, using band-to-band (B2B) phase referencing with a close phase calibrator J0504-1512, 1.°2 from R Lep in this case, and the imaging procedures required to obtain the maximum angular resolution achievable with ALMA. Images of the continuum emission and the hydrogen cyanide (HCN) maser line at 890.8 GHz, from the J = 10−9 transition between the (1110) and (0400) vibrationally excited states, achieved angular resolutions of 13, 6, and 5 mas in Bands 8–10, respectively. Self-calibration (self-cal) was used to produce ideal images to compare with the B2B phase referencing technique. The continuum emission was resolved in Bands 9 and 10, leaving too little flux for the self-cal of the longest baselines, so these comparisons are made at coarser resolution. Comparisons showed that B2B phase referencing provided phase corrections sufficient to recover 92%, 83%, and 77% of the ideal image continuum flux densities. The HCN maser was sufficiently compact to obtain self-cal solutions in Band 10 for all baselines (up to 16 km). In Band 10, B2B phase referencing as compared to the ideal images recovered 61% and 70% of the flux density for the HCN maser and continuum, respectively.

ALMA Observations of the DART Impact: Characterizing the Ejecta at Submillimeter Wavelengths

We report observations of the Didymos–Dimorphos binary asteroid system using the Atacama Large Millimeter/submillimeter Array (ALMA) and the Atacama Compact Array (ACA) in support of the Double Asteroid Redirection Test mission. Our observations on UT 2022 September 15 provided a preimpact baseline and the first measure of Didymos–Dimorphos’s spectral emissivity at λ = 0.87 mm, which was consistent with the handful of siliceous and carbonaceous asteroids measured at millimeter wavelengths. Our postimpact observations were conducted using four consecutive executions each of ALMA and the ACA spanning from T+3.52 to T+8.60 hr, sampling thermal emission from the asteroids and the impact ejecta. We scaled our preimpact baseline measurement and subtracted it from the postimpact observations to isolate the flux density of millimeter-sized grains in the ejecta. Ejecta dust masses were calculated for a range of materials that may be representative of Dimorphos’s S-type asteroid material. The average ejecta mass over our observations is consistent with 1.3–6.4 × 107 kg, with the lower and higher values calculated for amorphous and crystalline silicates, respectively. Owing to the likely crystalline nature of S-type asteroid material, the higher value is favored. These ejecta masses represent 0.3%–1.5% of Dimorphos’s total mass and are in agreement with lower limits on the ejecta mass based on measurements at optical wavelengths. Our results provide the most sensitive measure of millimeter-sized material in the ejecta and demonstrate the power of ALMA for providing supporting observations to spaceflight missions.

MINDS

Context. The Mid-InfraRed Instrument (MIRI) Medium Resolution Spectrometer (MRS) on board the James Webb Space Telescope (JWST) allows us to probe the inner regions of protoplanetary disks, where the elevated temperatures result in an active chemistry and where the gas composition may dictate the composition of planets forming in this region. The disk around the classical T Tauri star Sz 98, which has an unusually large dust disk in the millimetre with a compact core, was observed with the MRS, and we examine its spectrum here. Aims. We aim to explain the observations and put the disk of Sz 98 in context with other disks, with a focus on the H2O emission through both its ro-vibrational and pure rotational emission. Furthermore, we compare our chemical findings with those obtained for the outer disk from Atacama Large Millimeter/submillimeter Array (ALMA) observations. Methods. In order to model the molecular features in the spectrum, the continuum was subtracted and local thermodynamic equilibrium (LTE) slab models were fitted. The spectrum was divided into different wavelength regions corresponding to H2O lines of different excitation conditions, and the slab model fits were performed individually per region. Results. We confidently detect CO, H2O, OH, CO2, and HCN in the emitting layers. Despite the plethora of H2O lines, the isotopo-logue H218O is not detected. Additionally, no other organics, including C2H2, are detected. This indicates that the C/O ratio could be substantially below unity, in contrast with the outer disk. The H2O emission traces a large radial disk surface region, as evidenced by the gradually changing excitation temperatures and emitting radii. Additionally, the OH and CO2 emission is relatively weak. It is likely that H2O is not significantly photodissociated, either due to self-shielding against the stellar irradiation, or UV shielding from small dust particles. While H2O is prominent and OH is relatively weak, the line fluxes in the inner disk of Sz 98 are not outliers compared to other disks. Conclusions. The relative emitting strength of the different identified molecular features points towards UV shielding of H2O in the inner disk of Sz 98, with a thin layer of OH on top. The majority of the organic molecules are either hidden below the dust continuum, or not present. In general, the inferred composition points to a sub-solar C/O ratio (&lt;0.5) in the inner disk, in contrast with the larger than unity C/O ratio in the gas in the outer disk found with ALMA.

Searching for C ii Emission from the First Sample of z ∼ 6 O i Absorption-associated Galaxies with the Atacama Large Millimeter/submillimeter Array

We report the first statistical analyses of [C ii] and dust continuum observations in six strong O i absorber fields at the end of the reionization epoch obtained by the Atacama Large Millimeter/submillimeter Array (ALMA). Combined with one [C ii] emitter reported in Wu et al., we detect one O i-associated [C ii] emitter in six fields. At redshifts of O i absorbers in nondetection fields, no emitters are brighter than our detection limit within impact parameters of 50 kpc and velocity offsets between ±200 km s−1. The averaged [C ii]-detection upper limit is <0.06 Jy km s−1(3σ), corresponding to the [C ii] luminosity of L [C II]< 5.8 × 107 L ⊙ and the [C ii]-based star formation rate of SFR[C II]<5.5 M ⊙ yr−1. Cosmological simulations suggest that only ∼10−2.5 [C ii] emitters around O i absorbers have comparable SFR to our detection limit. Although the detection in one out of six fields is reported, an order of magnitude number excess of emitters obtained from our ALMA observations supports that the contribution of massive galaxies that caused the metal enrichment cannot be ignored. Further, we also found 14 tentative galaxy candidates with a signal-to-noise ratio of ≈4.3 at large impact parameters (>50 kpc) and having larger outflow velocities within ±600 km s−1. If these detections are confirmed in the future, then the mechanism of pushing metals at larger distances with higher velocities needs to be further explored from the theoretical side.

A plausible link between dynamically unsettled molecular gas and the radio jet in NGC 6328

We report the detection of outflowing molecular gas at the center of the nearby radio galaxy NGC6328 (z = 0.014), which has a gigahertz-peaked spectrum radio core and a compact (2 pc) young double radio lobe tracing jet. Utilizing Atacama Large Millimeter/submillimeter Array (ALMA) CO(3 − 2) and CO(2 − 1) observations, as well as a novel code developed to fit the 3D gas distribution and kinematics, to study the molecular gas kinematics, we find that the bulk of the gas is situated within a highly warped disk structure, most likely the result of a past merger event. Our analysis further uncovers, within the inner regions of the gas distribution (R &lt; 300 pc) and at a position angle aligning with that of the radio jet (150°), the existence of two anti-diametric molecular gas structures kinematically detached from the main disk. These structures most likely trace a jet-induced cold gas outflow with a total lower limit mass of 2 × 106 M⊙ mass, corresponding to an outflow rate of 2 M⊙ yr−1 and a kinetic power of 2.7 × 1040 erg s−1. The energy required to maintain such a molecular outflow is aligned with the mechanical power of the jet.

Early Planet Formation in Embedded Disks (eDisk). XII. Accretion Streamers, Protoplanetary Disk, and Outflow in the Class I Source Oph IRS 63

We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of the Class I source Oph IRS 63 in the context of the Early Planet Formation in Embedded Disks large program. Our ALMA observations of Oph IRS 63 show a myriad of protostellar features, such as a shell-like bipolar outflow (in 12CO), an extended rotating envelope structure (in 13CO), a streamer connecting the envelope to the disk (in C18O), and several small-scale spiral structures seen toward the edge of the dust continuum (in SO). By analyzing the velocity pattern of 13CO and C18O, we measure a protostellar mass of M ⋆ = 0.5 ± 0.2 M ⊙ and confirm the presence of a disk rotating at almost Keplerian velocity that extends up to ∼260 au. These calculations also show that the gaseous disk is about four times larger than the dust disk, which could indicate dust evolution and radial drift. Furthermore, we model the C18O streamer and SO spiral structures as features originating from an infalling rotating structure that continuously feeds the young protostellar disk. We compute an envelope-to-disk mass infall rate of ∼10−6 M ⊙ yr−1 and compare it to the disk-to-star mass accretion rate of ∼10−8 M ⊙ yr−1, from which we infer that the protostellar disk is in a mass buildup phase. At the current mass infall rate, we speculate that soon the disk will become too massive to be gravitationally stable.

The ALMA-ALPAKA survey

Context. Spatially resolved studies of the kinematics of galaxies provide crucial insights into their assembly and evolution, enabling one to infer the properties of the dark matter halos, derive the impact of feedback on the interstellar medium (ISM), as well as measure and characterize the outflow motions. To date, most of the kinematic studies at z = 0.5 − 3.5 have been obtained using emission lines tracing the warm, ionized gas (e.g., Hα, [OII], and [OIII]). However, whether these provide an exhaustive or only a partial view of the dynamics of galaxies and of the properties of the ISM is still debated. Complementary insights into the cold gas kinematics are therefore needed. Aims. We present the Archival Large Program to Advance Kinematic Analysis (ALPAKA), a project aimed at gathering high-resolution observations of CO and [CI] emission lines of star-forming galaxies at z = 0.5 − 3.5 from the Atacama Large Millimeter Array (ALMA) public archive. With ≈147 h of total integration time, ALPAKA assembles ∼0.25″ observations for 28 star-forming galaxies, which is the largest sample with spatially resolved cold gas kinematics as traced by either CO or [CI] at z ≳ 0.5, spanning 7 Gyr of cosmic history. A large fraction of ALPAKA galaxies (19 out of 28) lie in overdense regions (clusters, groups, and protoclusters). Methods. By combining multiwavelength ground- and space-based ancillary data, we derived the stellar masses (M⋆) and star-formation rates (SFRs) for the ALPAKA targets. We exploited the ALMA data to infer the dynamical state of the ALPAKA galaxies and derive their rotation curves and velocity dispersion profiles using 3DBAROLO. Results. ALPAKA probes the massive (M⋆ ≳ 1010 M⊙), actively star-forming (SFR ≈ 10 − 3000 M⊙ yr−1) part of the population of galaxies at z ∼ 0.5 − 3.5. Based on our kinematic classification, we find that 19 out of 28 ALPAKA galaxies are rotating disks, two are interacting systems, while for the remaining seven sources the classification is uncertain. The disks have velocity dispersion values that are typically larger in the innermost regions than in the outskirts, with a median value for the entire disk sample of 35−9+11 km s−1. Despite the bias of our sample toward galaxies hosting very energetic mechanisms, the ALPAKA disks have high ratios of ordered-to-random motion (V/σ) with a median value of 9−2+7.

Resolved low-J12CO excitation at 190 parsec resolution across NGC 2903 and NGC 3627

ABSTRACT The low-J rotational transitions of 12CO are commonly used to trace the distribution of molecular gas in galaxies. Their ratios are sensitive to excitation and physical conditions in the molecular gas. Spatially resolved studies of CO ratios are still sparse and affected by flux calibration uncertainties, especially since most do not have high angular resolution or do not have short-spacing information and hence miss any diffuse emission. We compare the low-J CO ratios across the disc of two massive, star-forming spiral galaxies NGC 2903 and NGC 3627 to investigate whether and how local environments drive excitation variations at GMC scales. We use Atacama Large Millimeter Array (ALMA) observations of the three lowest-J CO transitions at a common angular resolution of 4 arcsec (190 pc). We measure median line ratios of $R_{21}=0.67^{+0.13}_{-0.11}$, $R_{32}=0.33^{+0.09}_{-0.08}$, and $R_{31}=0.24^{+0.10}_{-0.09}$ across the full disc of NGC 3627. We see clear CO line ratio variation across the galaxy consistent with changes in temperature and density of the molecular gas. In particular, towards the centre, R21, R32, and R31 increase by 35 per cent, 50 per cent, and 66 per cent, respectively, compared to their average disc values. The overall line ratio trends suggest that CO(3–2) is more sensitive to changes in the excitation conditions than the two lower J transitions. Furthermore, we find a similar radial R32 trend in NGC 2903, albeit a larger disc-wide average of $\langle R_{32}\rangle =0.47^{+0.14}_{-0.08}$. We conclude that the CO low-J line ratios vary across environments in such a way that they can trace changes in the molecular gas conditions, with the main driver being changes in temperature.

CoCCoA: Complex Chemistry in hot Cores with ALMA

Context. Complex organic molecules (COMs), especially the oxygen-bearing species, have been observed to be abundant in the gas phase toward low-mass and high-mass protostars. Deep line surveys have been carried out only for a limited number of well-known star-forming regions using the Atacama Large Millimeter/submillimeter Array (ALMA), which has unprecedented resolution and sensitivity, and statistical studies on oxygen-bearing COMs (O-COMs) in a large sample of high-mass protostars using ALMA are still lacking. Aims. We aim to determine the column density ratios of six O-COMs with respect to methanol (CH3OH) in a sample of 14 high-mass protostellar sources in order to investigate their origin through ice and/or gas-phase chemistry. The selected species are: acetalde-hyde (CH3CHO), ethanol (C2H5OH), dimethyl ether (DME; CH3OCH3), methyl formate (MF; CH3OCHO), glycolaldehyde (GA; CH2OHCHO), and ethylene glycol (EG; (CH2OH)2). Methods. We fit the spectra of 14 high-mass sources observed as part of the Complex Chemistry in hot Cores with ALMA (CoCCoA) survey and derived the column densities and excitation temperatures of the six selected O-COMs. We used the minor isotopologue of methanol CH318OH to infer the column density of the main isotopologue CH3OH, of which the lines are generally optically thick. We compared our O-COM ratios with those of five low-mass protostars studied with ALMA from the available literature as well as with the results from experiments and simulations. Results. Although the CoCCoA sources have different morphologies and brightness in their continuum and methanol emission, the O-COM ratios with respect to methanol have very similar values in the high-mass and low-mass samples. The DME and MF have the highest and most constant ratios within one order of magnitude, while the other four species have lower ratios and exhibit larger scatter by one to two orders of magnitude. The ratio between DME and MF is close to one, which agrees well with previous observational findings. Current simulations and experiments can reproduce most observational trends with a few exceptions. For example, they tend to overestimate the abundance of ethanol and GA with respect to methanol. Conclusions. The constant column density ratios of the selected O-COMs among the low- and high-mass sources suggest that these species are formed in similar environments during star formation, probably on icy dust grains in the pre-stellar stages. Where deviations are found, hypotheses exist to explain the differences between observations, simulations, and experiments, such as the involvement of gas-phase chemistry and different emitting areas of molecules.

The [CII] 158 μm emission line as a gas mass tracer in high redshift quiescent galaxies

A great deal of effort has been made in recent years to probe the gas fraction evolution of massive quiescent galaxies (QGs); however, a clear picture has not yet been established. Recent spectroscopic confirmations at z &gt; 3 offer the chance to measure the residual gas reservoirs of massive galaxies a few hundred Myr after their death and to study how fast quenching proceeds in a highly star-forming Universe. Even so, stringent constraints at z &gt; 2 remain hardly accessible with the Atacama Large Millimeter/submillimeter Array (ALMA) when adopting molecular gas tracers commonly used for the quenched population. In this Letter we propose overcoming this impasse by using the carbon [CII] 158 μm emission line to systematically probe the gaseous budget of unlensed QGs at z &gt; 2.8, when these galaxies could still host non-negligible star formation on an absolute scale and when the line becomes best observable with ALMA (Bands 8 and 7). Predominantly used for star-forming galaxies to date, this emission line is the best choice to probe the gas budget of spectroscopically confirmed QGs at z &gt; 3, reaching 2–4 and 13–30 times deeper than dust continuum emission (ALMA band 7) and CO(2–1)/(1–0) (Very Large Array, VLA, K − Kα bands), respectively, at fixed integration time. Exploiting archival ALMA observations, we place conservative 3σ upper limits on the molecular gas fraction (fmol = MH2/M⋆) of ADF22-QG1 (fmol &lt; 21%) and ZF-COS-20115 (fmol &lt; 3.2%), two of the best-studied high-z QGs in the literature, and GS-9209 (fmol &lt; 72%), the most distant massive QG discovered to date. The deep upper limit found for ZF-COS-20115 is three times lower than previously anticipated for high-z QGs suggesting, at best, the existence of a large scatter in the fmol distribution of the first QGs. Lastly, we discuss the current limitations of the method and propose ways to mitigate some of them by exploiting ALMA bands 9 and 10.

Complex Organic Molecules in a Very Young Hot Corino, HOPS 373SW

We present the spectra of complex organic molecules (COMs) detected in HOPS 373SW with the Atacama Large Millimeter/submillimeter Array (ALMA). HOPS 373SW, which is a component of a protostellar binary with a separation of 1500au, has been discovered as a variable protostar by the JCMT transient monitoring survey with a modest (∼30%) brightness increase at submillimeter wavelengths. Our ALMA target-of-opportunity observation at ∼345 GHz for HOPS 373SW revealed extremely young chemical characteristics with strong deuteration of methanol. The dust continuum opacity is very high toward the source center, obscuring line emission from within 0.″03. The other binary component, HOPS 373NE, was detected only in C17O in our observation, implying a cold and quiescent environment. We compare the COM abundances relative to CH3OH in HOPS 373SW with those of V883 Ori, which is an eruptive disk object, as well as other hot corinos, to demonstrate the chemical evolution from envelope to disk. High abundances of singly, doubly, and triply deuterated methanol (CH2DOH, CHD2OH, and CD3OH) and a low CH3CN abundance in HOPS 373SW compared to other hot corinos suggest a very early evolutionary stage of HOPS 373SW in the hot corino phase. Since the COMs detected in HOPS 373SW would have been sublimated very recently from grain surfaces, HOPS 373SW is a promising place to study the surface chemistry of COMs in the cold prestellar phase before sublimation.

Resolved Kennicutt–Schmidt law in two strongly lensed star-forming galaxies at redshift 1

We study the star formation rate (SFR) vs. molecular gas mass (Mmol) scaling relation from hundreds to thousands of parsec in two strongly lensed galaxies at redshift z ∼ 1, the Cosmic Snake and A521. We trace the SFR using extinction-corrected rest-frame UV observations with the Hubble Space Telescope (HST), and Mmol using detections of the CO(4–3) line with the Atacama Large Millimeter/submillimeter Array (ALMA). The similar angular resolutions of our HST and ALMA observations of 0.15 − 0.2″ combined with magnifications reaching μ &gt; 20 enable us to resolve structures in the galaxies of sizes lower than 100 pc. These resolutions are close to those of studies of nearby galaxies. This allows us to investigate for the first time the Kennicutt–Schmidt (KS) law (SFR–Mmol surface densities) at different spatial scales, from galactic scales to ∼100 pc scales, in galaxies at z ∼ 1. At integrated scales we find that both galaxies satisfy the KS law defined by galaxies at redshifts between 1 and 2.5. We test the resolved KS (rKS) law in cells of sizes down to 200 pc in the two galaxies. We observe that this relationship generally holds in these z ∼ 1 galaxies, although its scatter increases significantly with decreasing spatial scales. We check the scale dependence of the spatial correlation between the surface densities of SFR and Mmol by focusing on apertures centred on individual star-forming regions and molecular clouds. We conclude that star-forming regions and molecular clouds become spatially de-correlated at ≲1 kpc in the Cosmic Snake, whereas they appear de-correlated at all spatial scales (from 400 pc to 6 kpc) in A521.

A Near-infrared-faint, Far-infrared-luminous Dusty Galaxy at z ∼ 5 in COSMOS-Web

A growing number of far-infrared (FIR) bright sources completely invisible in deep extragalactic optical surveys hint at an elusive population of z > 4 dusty, star-forming galaxies. Cycle 1 JWST surveys are now detecting their rest-frame optical light, which provides key insight into their stellar properties and statistical constraints on the population as a whole. This work presents the JWST Near Infrared Camera (NIRCam) counterpart from the COSMOS-Web survey to an FIR SCUBA-2 and Atacama Large Millimeter/submillimeter Array (ALMA) source, AzTECC71, which was previously undetected at wavelengths shorter than 850 μm. AzTECC71, among the reddest galaxies in COSMOS-Web with F277W − F444W ∼ 0.9, is undetected in NIRCam/F150W and F115W and fainter in F444W than other submillimeter galaxies identified in COSMOS-Web by 2–4 magnitudes. This is consistent with the system having both a lower stellar mass and higher redshift than the median dusty, star-forming galaxy. With deep ground- and space-based upper limits combined with detections in F277W, F444W, and the FIR including ALMA Band 6, we find a high probability (99%) that AzTECC71 is at z > 4 with . This galaxy is massive () and infrared-luminous (), comparable to other optically undetected but FIR-bright dusty, star-forming galaxies at z > 4. This population of luminous, infrared galaxies at z > 4 is largely unconstrained but comprises an important bridge between the most extreme dust-obscured galaxies and more typical high-redshift star-forming galaxies. If further FIR-selected galaxies that drop out of the F150W filter in COSMOS-Web have redshifts z > 4 like AzTECC71, then the volume density of such sources may be ∼3–10 × greater than previously estimated.

ALMA 300 pc Resolution Imaging of a z = 6.79 Quasar: No Evidence for Supermassive Black Hole Influence on the C ii Kinematics

We present Atacama Large Millimeter/submillimeter Array (ALMA) [C ii] 158 μm and dust continuum observations of the z = 6.79 quasar J0109–3047 at a resolution of 0.″045 (∼300 pc). The dust and [C ii] emission are enclosed within a ∼500 pc radius, with the central beam (r < 144 pc) accounting for ∼25% (8%) of the total continuum ([C ii]) emission. The far-infrared (FIR) luminosity density increases radially from ∼5 × 1011 L ⊙ kpc−2 to a central value of ∼70 × 1011 L ⊙ kpc−2 (SFRD ∼50–700 M ⊙yr−1 kpc−2). The [C ii] kinematics are dispersion dominated with a constant velocity dispersion of 137 ± 6 km s−1. The constant dispersion implies that the underlying mass distribution is not centrally peaked, consistent with the expectations of a flat gas mass profile. The lack of an upturn in velocity dispersion within the central beam is inconsistent with a black hole mass greater than M BH < 6.5 × 108 M ⊙ (2σ level), unless highly fine-tuned changes in the interstellar medium properties conspire to produce a decrease of the gas mass in the central beam comparable to the black hole mass. Our observations therefore imply either that (a) the black hole is less massive than previously measured, or (b) the central peak of the FIR and [C ii] emission are not tracing the location of the black hole, as suggested by the tentative offset between the near-infrared position of the quasar and the ALMA continuum emission.

MAPS: Constraining Serendipitous Time Variability in Protoplanetary Disk Molecular Ion Emission

Theoretical models and observations suggest that the abundances of molecular ions in protoplanetary disks should be highly sensitive to the variable ionization conditions set by the young central star. We present a search for temporal flux variability of HCO+ J = 1–0, which was observed as a part of the Molecules with Atacama Large Millimeter/submillimeter Array (ALMA) at Planet-forming Scales ALMA Large Program. We split out and imaged the line and continuum data for each individual day the five sources were observed (HD 163296, AS 209, GM Aur, MWC 480, and IM Lup, with between three and six unique visits per source). Significant enhancement (>3σ) was not observed, but we find variations in the spectral profiles in all five disks. Variations in AS 209, GM Aur, and HD 163296 are tentatively attributed to variations in HCO+ flux, while variations in IM Lup and MWC 480 are most likely introduced by differences in the uv coverage, which impact the amount of recovered flux during imaging. The tentative detections and low degree of variability are consistent with expectations of X-ray flare-driven HCO+ variability, which requires relatively large flares to enhance the HCO+ rotational emission at significant (>20%) levels. These findings also demonstrate the need for dedicated monitoring campaigns with high signal-to-noise ratios to fully characterize X-ray flare-driven chemistry.

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.