Evolved stars on the asymptotic giant branch and red supergiants have multiple processes that can be studied in the (sub)mm, including stellar surfaces, circumstellar thermal gas and dust, and masers. Telescopes such as APEX and ALMA have opened the possibility to perform studies that are revealing new information on these, as well as on the role of binaries in shaping stellar winds and the evolution to planetary nebulae. Here, we discuss some recent results for (sub)mm observations towards evolved stars focusing particularly on masers. This includes SiO and water masers, as well as ALMA high angular resolution observations of HCN masers towards a carbon-rich star.

We report the first detection of [NII] 122 μm line toward a QSO-SMG pair, BRI 1202-0725, at z = 4.7 using ALMA. Combining with [NII] 205 μm line detection and taking the line ratio of [NII]122/[NII]205, we constrain electron densities of both galaxies. The derived electron densities are ${26_{ - 11}^{ + 12}$ and ${134_{ - 39}^{ + 50}$ cm−3 for the SMG and the QSO, respectively, which are the first measurements for galaxies at z > 4. The electron density of the SMG is comparable to the Galactic plane and the average of local spiral galaxies, while the value for the QSO is comparable to local starbursts and optical-line based measurements for star-forming galaxies at z ∼ 2–3. Considering the similar star-formation rates (SFRs) of ≍ 1000 M⊙ yr−1 for both galaxies, our results suggest a large scatter of electron densities at fixed SFR and caution against using optical lines for dusty starbursts. The details of this report are presented in Lee et al. 2019 (submitted).

The estimation of interstellar dust masses is an important pursuit in our understanding of both local and early Universe – see e.g. the “dust budget crisis”. One of the most used methods of estimating dust masses – dust emission fitting – requires an estimate of the dust opacity at far-infrared and submillimeter wavelengths, but in most models this quantity is based on extrapolation rather than on actual measurements. It is becoming more and more evident that the opacity in typical dust models differs from that of dust analogs measured in the lab, meaning that astronomical dust mass estimations may need to be revised. To estimate the systematic errors introduced by this mismatch, we calculated dust emission for a model where dust far-infrared opacity is the same as that measured in lab samples, then we fit the synthetic emission with a typical (modified blackbody) dust model. Our results show that, if interstellar dust is indeed similar to the lab dust analogs, most fits may overestimate dust masses by as much as an order of magnitude.

The spatial distribution of the dust and stars contains crucial information about the evolutionary pathways of galaxies. We present results of our study combing high-resolution ALMA and HST observations of z ∼ 2 bright sub-millimeter galaxies (SMGs). We have developed a two-dimensional extinction and age correction technique to obtain accurate stellar mass distributions from HST/CANDELS. For the first time, we can directly compare the spatial distribution of assembled stellar mass and ongoing star formation on kpc scales for distant SMGs, shedding light on their highly debated formation mechanisms. We find that the dust distribution is more compact than the stellar component, regardless if the SMG lies on the main sequence or at the starburst regime. Taking the dust emission as a proxy for dust-obscured star formation, our results imply that high-redshift SMGs are experiencing centrally enhanced star formation. These findings suggests that major galaxy interactions are not necessarily the main formation channel for SMGs with secular disk formation remaining a viable option as suggested by state-of-the-art cosmological simulations. The sizes and stellar densities of our z ∼ 2 SMGs agree well with the most compact early-type galaxies in the local Universe, strongly supporting the idea that the latter systems are indeed the descendants of massive SMGs at z ∼ 2.

We present 0.″2–0.″4 resolution ALMA images of the submillimeter dust continuum and the CO, H2O, and H2O+ line emission in a z = 3.63 strongly lensed dusty starburst. We construct the lens model for the system with an MCMC technique. While the average magnification for the dust continuum is about 11, the magnification of the line emission varies from 5 to 22 across the source, resolving the source down to sub-kpc scales. The ISM content reveals that it is a pre-coalescence major merger of two ultra-luminous infrared galaxies, both with a large amount of molecular gas reservoir. The approaching galaxy in the south shows no apparent kinematic structure with a half-light radius of 0.4 kpc, while the preceding one resembles a 1.2 kpc rotating disk, separated by a projected distance of 1.3 kpc. The distribution of dust and gas emission suggests a large amount of cold ISM concentrated in the interacting region.

Powerful AGN have been detected up to very high redshifts (z ∼ 6–8), well within the Epoch of Reionization (EoR), but the lack of powerful radio-galaxies among such sources strongly disagrees with the expectations based on the known radio population up to z ∼ 5. Our group has been pursuing a detailed analysis of the faintest population of radio sources detected in the deepest fields searching for clues of these first radio galaxies. This paper describes our strategy and presents a highly confident candidate. The results, once follow-up of all candidates is completed, will have significant implications for the upcoming generation of all-sky deep radio surveys such as ASKAP-EMU, Westerbork-WODAN, and SKA itself.

Submillimeter galaxies at redshift z⩾1 show a pronounced [CII]/FIR deficit down to sub-kpc scales; however, the physical origin of this deficit remains poorly understood. We use resolved ALMA observations of the [CII], FIR and CO(3–2) emission in two z = 3 SMGs to distinguish between the different proposed scenarios; the thermal saturation of the [CII] emission is the most likely explanation.

We present new constraints on the cosmic cold molecular gas evolution out to redshift 6 based on systematic mining of the public ALMA archive in the COSMOS field (A3 COSMOS). Our A3 COSMOS dataset contains ∼ 700 galaxies (0.3 ≲ z ≲ 6) with high-confidence ALMA detection and multi-wavelength SEDs. Combining with ∼ 1,200 CO-observed galaxies at 0 ≲ z ≲ 4 (75% at z < 0.1) in the literature, we parameterize galaxies’ molecular gas depletion time and gas fraction each as a function of stellar mass, offset from the star-forming main-sequence and cosmic age. We propose a new functional form which provides a better fit and implies a “downsizing” effect and “mass-quenching”. By adopting galaxy stellar mass functions and applying our gas fraction function, we obtain a cosmic cold molecular gas density evolution in agreement with recent CO blind field surveys as well as semi-analytic modeling. These together provide us a coherent picture of galaxy cold molecular gas, SFR and stellar mass evolution.

Circumstellar dust analogues can be studied experimentally to determine their collisional behavior and their optical properties. These results affect simulations of circumstellar disks in various, substantial ways: Collision results determine how dust aggregates grow and how their aerodynamic properties change with time. This determines how solids move throughout the disk, how they accumulate, and how planetesimals might be formed. The optical properties determine the observational signature of these effects and allow us to constrain the spatial distribution of dust in disks, the sizes of the aggregates, as well as the temperature and optical depth of the dust emission. In this contribution, it is discussed how theoretical models and their predictions depend on laboratory results and what we learned about disks from high spatial resolution radio interferometry.

We present the results of a 69 arcmin2 ALMA survey at 1.1 mm, GOODS-ALMA, matching the deepest HST-WFC3 H-band observed region of the GOODS-South field. The 35 galaxies detected by ALMA are among the most massive galaxies at z = 2–4 and are either starburst or located in the upper part of the galaxy star-forming main sequence. The analysis of the gas fraction, depletion time, X-ray luminosity and the size suggests that they are building compact bulges and are the ideal progenitors of compact passive galaxies at z˜2, and a slow downfall scenario is favoured in their future transition from star-forming to passive galaxies.

In the era of ALMA, we can now resolve polarization within circumstellar disks at (sub)millimeter wavelengths. While many initially hoped that these observations would map magnetic fields in disks, the observed polarization patterns indicate other possible polarization mechanisms. These alternative polarization mechanisms include Rayleigh self-scattering, grains aligning with the radiation anisotropy (k-RAT alignment), and mechanical alignment. Stephens et al. (2017) specifically showed that the polarization morphology in HL Tau changes rapidly with wavelength; the morphology is uniform at 870 μm, azimuthal at 3.1 mm, and ∼50%/50% mix of the two at 1.3 mm. Although it has been suggested that the polarized emission at 870 μm is due to scattering and at 3.1 mm is due to k-RAT alignment, both mechanisms appear to have shortcomings. Specifically, Kataoka et al. (2017) showed that scattering requires much smaller grains (10s of μm) than that suggested by other studies, while k-RAT alignment suggest a significant decrease in polarization along the minor axis, which is not seen. Studies of other disks have suggested that polarization may come from grains aligned with the magnetic fields, but these studies are inconclusive. Understanding and extracting information about the polarized emission from disks requires multi-wavelength and high resolution observations.

Star formation started as a cosmic process soon after the big bang and still continues in the Milky Way, although at a decreasing rate. The formation of dense interstellar clouds, their fragmentation and eventual collapse lead to the birth of stars. The nearby clouds provide the highest resolution for the study of this process. The progress is closely following the improvement of the infrared and radio-wavelength facilities that enables us to follow even the earliest stages of the star-formation process inside molecular clouds. On the other hand, modern numerical simulations can take into account most of the relevant physics and often provide a more direct access into the general principles of star formation. The comparison of observations and simulations is therefore essential. In this paper, will discuss star formation in the solar neighbourhood, concentrating on the prestellar phases leading up to the formation of protostars.

Dense cores represent a critical stage in the star-formation process, but are not physically well-defined entities. We present a new technique to define core boundaries in observations of molecular clouds based on the physical properties of the cloud medium. Applying this technique to regions in the Pipe nebula, we find that our core boundaries differ from previous analyses, with potentially crucial implications for the statistical properties of the core sample.

We observed the circumstellar environments (CSEs) of the semiregular AGB stars L2 Puppis, R Doradus and EP Aquarii with ALMA. (1) The molecular emission in the L2 Pup nebula reveals an edge-on rotating disk. (2) PV diagrams of the 28SiO emission in the inner CSE of R Dor expose a pattern pointing to an inclined rotating disk. (3) The CO emission in the CSE of EP Aqr reveals a nearly face-on equatorial density enhancement (EDE). The inner EDE strongly resembles theoretical wind-Roche-lobe-overflow models. The SiO emission points to a potential companion. The combination of (1), (2) and (3) suggests that a link may exist between the type of AGB pulsations and the morphological nature of the CSE.

Low and intermediate mass stars evolve to the asymptotic red giant branch (AGB) late in their lives. These are surrounded by a circumstellar envelope (CSE) filled with gas and dust. The dust is formed close to the star at sublimation radii and is pushed away by the stellar wind. The dust in turn pushes gases from the envelope into the interstellar medium, thus enriching it with metals. This poster summary is a general description of the next piece of a larger project, whereas the first half has been published by Nicolaes et al. (2018). We now aim to use radiative transfer simulations to model spectral energy distributions (SED) of dust and fit them to far-infrared observations for the same 40 sources. We will use 2D and 3D simulations and models containing several dust species simultaneously.

In this work, we carry out two-fluid (gas+dust) hydrodynamical simulations on a large family of models in order to study the dust coagulation and the dust-gas dynamical processes in protoplanetary disks. Our theoretical effort is guided by the observational results of disks in nearby star forming regions at sub-millimeter and millimeter (mm) wavelengths. By a systematic comparison with the continuum emission at several mm bands from ALMA observations, we find that ringed structures are predicated in the unresolved faint disks for those with mm spectral indexes as low as about 2.0. Our parameter exploration can also be used to constrain the fragmentation velocity, one key parameter of the dust coagulation model, and some other disk parameters.

Carbon-rich Asymptotic Giant Branch (AGB) stars are major sources of gas and dust in the interstellar medium. During the brief (∼1000 yr) period in the evolution from AGB to the Planetary Nebula (PN) stage, the molecular composition evolves from mainly diatomic and small polyatomic species to more complex molecules. Using the Submillimeter Array (SMA), we have carried out a spectral line survey of CRL 618, covering a frequency range of 281.9 to 359.4 GHz. More than 1000 lines were detected in the ∼60 GHz range, most of them assigned to HC3N and c-C3H2, and their isotopologues. About 200 lines are unassigned. Lines of CO, HCO+, and CS show the fast outflow wings, while the majority of line emission arises from a compact region of ∼1” diameter. We have analyzed the lines of HC3N, c-C3H2, CH3CN, and their isotopologues with rotation temperature diagrams.

In the last decade, it has become clear that the dust-enshrouded star formation contributes significantly to early galaxy evolution. Detection of dust is therefore essential in determining the properties of galaxies in the high-redshift universe. This requires observations at the (sub-)millimeter wavelengths. Unfortunately, sensitivity and background confusion of single dish observations on the one hand, and mapping efficiency of interferometers on the other hand, pose unique challenges to observers. One promising route to overcome these difficulties is intensity mapping of fluctuations which exploits the confusion-limited regime and measures the collective light emission from all sources, including unresolved faint galaxies. We discuss in this contribution how 2D and 3D intensity mapping can measure the dusty star formation at high redshift, through the Cosmic Infrared Background (2D) and [CII] fine structure transition (3D) anisotropies.

Masers have been well-known phenomena for decades, but water masers at 183, 321, 325 and 658 GHz have only been detected since the 1990s. Early detections came from single-dish telescopes with follow-up observations from the PdBI and the Submillimeter Array. Detecting them at these short wavelengths has been very difficult due to water in our atmosphere, meaning that even in very good weather, one can only detect very bright masers, such as those in stellar atmospheres. In the last 7 years, a new window on submillimeter water masers, both Galactic and now extragalactic, has opened. Located at high altitude, above a large fraction of the Earth’s atmosphere, ALMA sits on the edge of the driest desert on the planet, meaning that the air that does remain above the telescope is frequently extremely low in water vapor content. Combine this with sensitive, stable receivers covering a number of masing transitions from 183-658 GHz and you have an excellent machine for detecting and characterizing submillimeter water masers. In addition, other molecules also exhibit maser emission in the ALMA observing bands, such as SiO and HCN.

We present the results of the first detection of submillimeter water maser emission toward water-fountain nebulae. Using APEX we found emission at 321.226 GHz toward two sources: IRAS 18043−2116, and IRAS 18286−0959. The submillimeter H2O masers exhibit expansion velocities larger than those of the OH masers, suggesting that these masers, similarly to the 22 GHz masers, originate in fast bipolar outflows. The 321 GHz masers in IRAS 18043−2116 and IRAS 18286−0959, which figure among the sources with the fastest H2O masers, span a velocity range similar to that of the 22 GHz masers, indicating that they probably coexist. The intensity of the submillimeter masers is comparable to the 22 GHz masers, implying that the kinetic temperature of the region where the masers originate is Tk>1000 K. We propose a simple model invoking the passage of two shocks through the same gas that creates the conditions for explaining the strong high-velocity 321 GHz masers coexisting with the 22 GHz masers in the same region.