Search

We use the James Webb Space Telescope (JWST) and its Mid-Infrared Instrument (MIRI) (5-28 um), to study the embedded HH 211 flow. We map a 0.95'x0.22' region, covering the full extent of the blue-shifted lobe, the central protostellar region, and a small portion of the red-shifted lobe. The jet driving source is not detected even at the longest mid-IR wavelengths. The overall morphology of the flow consists of a highly collimated jet, mostly molecular (H2, HD) with an inner atomic ([FeI], [FeII], [SI], [NiII]) structure. The jet shocks the ambient medium, producing several large bow-shocks, rich in forbidden atomic and molecular lines, and is driving an H2 molecular outflow, mostly traced by low-J, v=0 transitions. Moreover, 0-0 S(1) uncollimated emission is also detected down to 2"-3" (~650-1000 au) from the source, tracing a cold (T=200-400 K), less dense and poorly collimated molecular wind. The atomic jet ([FeII] at 26 um) is detected down to ~130 au from source, whereas the lack of H2 emission close to the source is likely due to the large visual extinction. Dust continuum-emission is detected at the terminal bow-shocks, and in the blue- and red-shifted jet, being likely dust lifted from the disk. The jet shows an onion-like structure, with layers of different size, velocity, temperature, and chemical composition. Moreover, moving from the inner jet to the outer bow-shocks, different physical, kinematic and excitation conditions for both molecular and atomic gas are observed. The jet mass-flux rate, momentum, and momentum flux of the warm H2 component are up to one order of magnitude higher than those inferred from the atomic jet component. Our findings indicate that the warm H2 component is the primary mover of the outflow, namely it is the most significant dynamical component of the jet, in contrast to jets from more evolved YSOs, where the atomic component is dominant., Comment: Paper accepted in A&A for publication

We use data from the ALMA Evolutionary Study of High Mass Protocluster Formation in the Galaxy (ALMAGAL) survey to study 100 ALMAGAL regions at $\sim$ 1 arsecond resolution located between $\sim$ 2 and 6 kpc distance. Using ALMAGAL $\sim$ 1.3mm line and continuum data we estimate flow rates onto individual cores. We focus specifically on flow rates along filamentary structures associated with these cores. Our primary analysis is centered around position velocity cuts in H$_2$CO (3$_{0,3}$ - 2$_{0,2}$) which allow us to measure the velocity fields, surrounding these cores. Combining this work with column density estimates we derive the flow rates along the extended filamentary structures associated with cores in these regions. We select a sample of 100 ALMAGAL regions covering four evolutionary stages from quiescent to protostellar, Young Stellar Objects (YSOs), and HII regions (25 each). Using dendrogram and line analysis, we identify a final sample of 182 cores in 87 regions. In this paper, we present 728 flow rates for our sample (4 per core), analysed in the context of evolutionary stage, distance from the core, and core mass. On average, for the whole sample, we derive flow rates on the order of $\sim$10$^{-4}$ M$_{sun}$yr$^{-1}$ with estimated uncertainties of $\pm$50%. We see increasing differences in the values among evolutionary stages, most notably between the less evolved (quiescent/protostellar) and more evolved (YSO/HII region) sources. We also see an increasing trend as we move further away from the centre of these cores. We also find a clear relationship between the flow rates and core masses $\sim$M$^{2/3}$ which is in line with the result expected from the tidal-lobe accretion mechanism. Overall, we see increasing trends in the relationships between the flow rate and the three investigated parameters; evolutionary stage, distance from the core, and core mass., Comment: 11 pages, 11 figures, accepted for publication in A&A

A rich inventory of complex organic molecules (COMs) has been observed in high abundances in the gas phase toward Class 0 protostars. These molecules are suggested to be formed in ices and sublimate in the warm inner envelope close to the protostar. However, only the most abundant COM, methanol (CH3OH), has been firmly detected in ices before the era of James Webb Space Telescope (JWST). Now it is possible to detect the interstellar ices of other COMs and constrain their ice column densities quantitatively. We aim to determine the column densities of several oxygen-bearing COMs (O-COMs) in both gas and ice for two low-mass protostellar sources, NGC 1333 IRAS 2A and B1-c, as case studies in our JWST Observations of Young protoStars (JOYS+) program. By comparing the column density ratios w.r.t. CH3OH between both phases measured in the same sources, we can probe into the evolution of COMs from ice to gas in the early stages of star formation. We are able to fit the fingerprints range of COM ices between 6.8 and 8.8 um in the JWST/MIRI-MRS spectra of B1-c using similar components as recently used for IRAS 2A. We claim detection of CH4, OCN-, HCOO-, HCOOH, CH3CHO, C2H5OH, CH3OCH3, CH3OCHO, and CH3COCH3 in B1-c, and upper limits are estimated for SO2, CH3COOH, and CH3CN. The comparison of O-COM ratios w.r.t CH3OH between ice and gas shows two different cases. 1) the column density ratios of CH3OCHO and CH3OCH3 match well between the two phases, which may be attributed to a direct inheritance from ice to gas or strong chemical links with CH3OH. 2) the ice ratios of CH3CHO and C2H5OH w.r.t. CH3OH are higher than the gas ratios by 1-2 orders of magnitudes. This difference can be explained by the gas-phase reprocessing following sublimation, or different spatial distributions of COMs in the envelope., Comment: 42 pages (22 main text, 20 appendix); 27 figures (12 in main text, 15 in appendix); 5 tables (2 in main text, 3 in appendix) Accepted for publication in A&A

Deuterated molecules and their molecular D/H-ratios (RD(D)) are important diagnostic tools to study the physical conditions of star-forming regions. The degree of deuteration, RD(D), can be significantly enhanced over the elemental D/H-ratio depending on physical parameters. Within the Cygnus Allscale Survey of Chemistry and Dynamical Environments (CASCADE), we aim to explore the large-scale distribution of deuterated molecules in the nearby Cygnus-X region. We focus on the analysis of large-scale structures of deuterated molecules in the filamentary region hosting the prominent Hii region DR21 and DR21(OH). Here we discuss the HCO+, HNC and HCN molecules and their deuterated isotopologues DCO+, DNC and DCN. The spatial distributions of integrated line emissions from DCO+, DNC, and DCN reveal morphological differences. DCO+ displays the most extended emission, characterized by several prominent peaks. Likewise, DNC exhibits multiple peaks, although its emission appears less extended compared to DCO+. In contrast to the extended emission of DCO+ and DNC, DCN appears the least extended, with distinct peaks. Focusing only on the regions where all three molecules are observed, the mean deuteration ratios for each species are 0.01 for both DNC and DCN, and = 0.005 for DCO+. Anti-correlations are found with deuterated molecules and dust temperature or N(H2). The strongest anti-correlation is found with RD(DCO+) and N(H2). The anti-correlation of RD(DCO+) and N(H2) is suggested to be a result of a combination of an increased photodissociation degree and shocks. A strong positive correlation between the ratio of integrated intensities of DCN and DNC with their 13C-isotopologues, are found in high column density regions. The positive relationship between the ratios implies that the D-isotopologue of the isomers could potentially serve as a tracer for the kinetic gas temperature., Comment: 24 pages, 21 figures, accepted to A&A

Complex Organic Molecules (COMs) have been found toward low-mass protostars but the origins of the COM emission are still unclear. It can be associated with, for example, hot corinos, outflows, and/or accretion shock/disk atmosphere. We have conducted NOEMA observations toward SVS13A from the PROtostars & DIsks: Global Evolution (PRODIGE) program. Our previous \ce{DCN} observations reveal a possible infalling streamer, which may affect the chemistry of the central protobinary by inducing accretion outbursts and/or shocked gas. Here, we further analyze six O-bearing COMs: CH3OH, aGg'-(CH2OH)2, C2H5OH, CH2(OH)CHO, CH3CHO, and CH3OCHO. Although the COM emission is not spatially resolved, we constrain the source sizes to $\lesssim0.3-0.4$ arcsec (90$-$120 au) by conducting uv-domain Gaussian fitting. Interestingly, the high-spectral resolution data reveal complex line profiles with multiple peaks showing differences between these six O-bearing COMs. The LTE fitting unveils differences in excitation temperatures and emitting areas among these COMs. We further conduct multiple-velocity-component LTE fitting to decompose the line emission into different kinematic components. Up to 6 velocity components are found from the LTE modeling. The temperature, column density, and source size of these components from each COM are obtained. We find a variety in excitation temperatures ($100-500$ K) and source sizes (D$\sim10-70$ au) from these kinematic components from different COMs. The emission of each COM can trace several components and different COMs most likely trace different regions. Given this complex structure, we suggest that the central region is inhomogeneous and unlikely to be heated by only protostellar radiation. We conclude that accretion shocks induced by the large-scale infalling streamer likely exist and contribute to the complexity of the COM emission., Comment: 29 pages, 18 figures, accepted to A&A

We are performing a line survey of 8 planet-forming Class II disks in Taurus with the IRAM NOrthern Extended Millimeter Array (NOEMA), as a part of the MPG-IRAM Observatory Program PRODIGE (PROtostars and DIsks: Global Evolution; PIs: P. Caselli and Th. Henning). Compact and extended disks around T Tauri stars CI, CY, DG, DL, DM, DN, IQ Tau, and UZ Tau E are observed in ~80 lines from >20 C-, O,- N-, and S-bearing species. The observations in four spectral settings at 210-280 GHz with $1\sigma$ rms sensitivity of ~ 8-12 mJy/beam at 0.9" and 0.3 km/s resolution will be completed in 2024. The uv-visibilities are fitted with the DiskFit model to obtain key stellar and disk properties. In this paper, the combined $^{12}$CO, $^{13}$CO and C$^{18}$O $J = 2-1$ data are presented. We find that the CO fluxes and disk masses inferred from dust continuum tentatively correlate with the CO emission sizes. We constrain dynamical stellar masses, geometries, temperatures, the CO column densities and gas masses for each disk. The best-fit temperatures at 100 au are ~ 17-37 K, and decrease radially with the power-law exponent q ~ 0.05-0.76. The inferred CO column densities decrease radially with the power-law exponent p ~ 0.2-3.1. The gas masses estimated from $^{13}$CO (2-1) are ~ $0.001-0.2 M_\textrm{Sun}$. The best-fit CO column densities point to severe CO freeze-out in the disks. The DL Tau disk is an outlier, and has either stronger CO depletion or lower gas mass than the rest of the sample. The CO isotopologue ratios are roughly consistent with the observed values in disks and the low-mass star-forming regions., Comment: 47 pages, 10 figures, 6 tables, accepted for publication by A&A on 22/02/2024

Complex organic molecules (COMs) detected in the gas phase are thought to be mostly formed on icy grains, but no unambiguous detection of icy COMs larger than CH3OH has been reported so far. Exploring this matter in more detail has become possible with the JWST the critical 5-10 $\mu$m range. In the JOYS+ program, more than 30 protostars are being observed with the MIRI/MRS. This study explores the COMs ice signatures in the low and high-mass protostar, IRAS 2A and IRAS 23385, respectively. We fit continuum and silicate subtracted observational data with IR laboratory ice spectra. We use the ENIIGMA fitting tool to find the best fit between the lab data and the observations and to performs statistical analysis of the solutions. We report the best fits for the spectral ranges between 6.8 and 8.6 $\mu$m in IRAS 2A and IRAS 23385, originating from simple molecules, COMs, and negative ions. The strongest feature in this range (7.7 $\mu$m) is dominated by CH4 and has contributions of SO2 and OCN-. Our results indicate that the 7.2 and 7.4 $\mu$m bands are mostly dominated by HCOO-. We find statistically robust detections of COMs based on multiple bands, most notably CH3CHO, CH3CH2OH, and CH3OCHO. The likely detection of CH3COOH is also reported. The ice column density ratios between CH3CH2OH and CH3CHO of IRAS 2A and IRAS 23385, suggests that these COMs are formed on icy grains. Finally, the derived ice abundances for IRAS 2A correlate well with those in comet 67P/GC within a factor of 5. Based on the MIRI/MRS data, we conclude that COMs are present in interstellar ices, thus providing additional proof for a solid-state origin of these species in star-forming regions. The good correlation between the ice abundances in comet 67P and IRAS 2A is in line with the idea that cometary COMs can be inherited from the early protostellar phases., Comment: Accepted for publication in A&A

Methods: Observing the large pc-scale Stokes I mm dust continuum emission with the IRAM 30m telescope and the intermediate-scale (<0.1pc) polarized submm dust emission with the Submillimeter Array toward a sample of 20 high-mass star-forming regions allows us to quantify the dependence of the fragmentation behaviour of these regions depending on the density and magnetic field structures. Results: We infer density distributions n~r^{-p} of the regions with typical power-law slopes p around ~1.5. There is no obvious correlation between the power-law slopes of the density structures on larger clump scales (~1pc) and the number of fragments on smaller core scales (<0.1pc). Comparing the large-scale single-dish density profiles to those derived earlier from interferometric observations at smaller spatial scales, we find that the smaller-scale power-law slopes are steeper, typically around ~2.0. The flattening toward larger scales is consistent with the star-forming regions being embedded in larger cloud structures that do not decrease in density away from a particular core. Regarding the magnetic field, for several regions it appears aligned with filamentary structures leading toward the densest central cores. Furthermore, we find different polarization structures with some regions exhibiting central polarization holes whereas other regions show polarized emission also toward the central peak positions. Nevertheless, the polarized intensities are inversely related to the Stokes I intensities. We estimate magnetic field strengths between ~0.2 and ~4.5mG, and we find no clear correlation between magnetic field strength and the fragmentation level of the regions. Comparison of the turbulent to magnetic energies shows that they are of roughly equal importance in this sample. The mass-to-flux ratios range between ~2 and ~7, consistent with collapsing star-forming regions., Comment: Accepted for Astronomy & Astrophysics, 14 pages, 14 figures plus appendices, also download option at https://www2.mpia-hd.mpg.de/homes/beuther/papers.html

(abridged) We study and compare the warm (>100 K) and cold (<100 K) material toward the high-mass star-forming region IRAS 23385+6053 (IRAS 23385 hereafter) combining high angular resolution observations in the mid-infrared (MIR) with the JWST Observations of Young protoStars (JOYS) project and with the NOEMA at mm wavelengths at angular resolutions of 0.2"-1". The spatial morphology of atomic and molecular species is investigated by line integrated intensity maps. The temperature and column density of different gas components is estimated using H2 transitions (warm and hot component) and a series of CH3CN transitions as well as 3 mm continuum emission (cold component). Toward the central dense core in IRAS 23385 the material consists of relatively cold gas and dust (~50 K), while multiple outflows create heated and/or shocked H2 and show enhanced temperatures (~400 K) along the outflow structures. An energetic outflow with enhanced emission knots of [Fe II] and [Ni II] hints at J-type shocks, while two other outflows have enhanced emission of only H2 and [S I] caused by C-type shocks. The latter two outflows are also more prominent in molecular line emission at mm wavelengths (e.g., SiO, SO, H2CO, and CH3OH). Even higher angular resolution data are needed to unambiguously identify the outflow driving sources given the clustered nature of IRAS 23385. While most of the forbidden fine structure transitions are blueshifted, [Ne II] and [Ne III] peak at the source velocity toward the MIR source A/mmA2 suggesting that the emission is originating from closer to the protostar., Comment: 15 pages, 7 figures, accepted for publication in A&A

Molecular outflows are believed to be a key ingredient in the process of star formation. The molecular outflow associated with DR21 Main in Cygnus-X is one of the most extreme, in mass and size, molecular outflows in the Milky Way. The outflow is suggested to belong to a rare class of explosive outflows which are formed by the disintegration of protostellar systems.We aim to explore the morphology, kinematics,and energetics of the DR21 Main outflow, and compare those properties to confirmed explosive outflows to unravel the underlying driving mechanism behind DR21. Line and continuum emission are studied at a wavelength of 3.6\,mm with IRAM 30 m and NOEMA telescopes as part of the Cygnus Allscale Survey of Chemistry and Dynamical Environments (CASCADE) program. The spectra include ($J= 1-0$) transitions of HCO$^+$, HCN, HNC, N$_2$H$^+$, H$_2$CO, CCH tracing different temperature and density regimes of the outflowing gas at high-velocity resolution ($\sim$ 0.8 km s$^{-1}$). The map encompasses the entire DR21 Main outflow and covers all spatial scales down to a resolution of ~3" ($\sim$ 0.02 pc). Integrated intensity maps of the HCO$^+$ emission reveal a strongly collimated bipolar outflow with significant overlap of the blue- and red-shifted emission. The opening angles of both outflow lobes decrease with velocity, from $\sim80$ to 20$^{\circ}$ for the velocity range from 5 to 45 km s$^{-1}$ relative to the source velocity. No evidence is found for the presence of elongated, "filament-like" structures expected in explosive outflows. N$_2$H$^+$ emission near the western outflow lobe reveals the presence of a dense molecular structure which appears to be interacting with the DR21 Main outflow. The overall morphology as well as the detailed kinematics of the DR21 Main outflow is more consistent with that of a typical bipolar outflow instead of an explosive counterpart., Comment: 26 pages, 37 figures. Accepted for publication in A&A

The fragmentation mode of high-mass molecular clumps and the accretion processes that form the most massive stars ($M\gtrsim 8M_\odot$) are still not well understood. To this end, we have undertaken a large observational program (CORE) making use of interferometric observations from the Northern Extended Millimetre Array (NOEMA) for a sample of 20 luminous ($L>10^4L_\odot$) protostellar objects in the 1.37 mm wavelength regime in both continuum and line emission, reaching $\sim$0.4" resolution (800 au at 2 kpc). Using the dense gas tracer CH$_3$CN, we find velocity gradients across 13 cores perpendicular to the directions of bipolar molecular outflows, making them excellent disk candidates. Specific angular momentum ($j$) radial profiles are on average $\sim10^{-3}$ km /s pc and follow $j \propto r^{1.7}$, consistent with a poorly resolved rotating and infalling envelope/disk model. Fitting the velocity profiles with a Keplerian model, we find protostellar masses in the range of $\sim 10-25$ $M_\odot$. Modelling the level population of CH$_3$CN lines, we present temperature maps and find median gas temperatures in the range $70-210$ K. We create Toomre $Q$ maps to study the stability of the disks and find almost all (11 of 13) disk candidates to be prone to fragmentation due to gravitational instabilities at the scales probed by our observations. In particular, disks with masses greater than $\sim10-20\%$ of the mass of their host (proto)stars are Toomre unstable, and more luminous protostellar objects tend to have disks that are more massive and hence more prone to fragmentation. Our finings show that most disks around high-mass protostars are prone to disk fragmentation early in their formation due to their high disk to stellar mass ratio. This impacts the accretion evolution of high-mass protostars which will have significant implications for the formation of the most massive stars., Comment: 27 pages, 12 figures, 6 appendices - accepted for publication in Astronomy and Astrophysics

Aims: The JWST program JOYS (JWST Observations of Young protoStars) aims at characterizing the physical and chemical properties of young high- and low-mass star-forming regions, in particular the unique mid-infrared diagnostics of the warmer gas and solid-state components. We present early results from the high-mass star formation region IRAS23385+6053. Methods: The JOYS program uses the MIRI MRS with its IFU to investigate a sample of high- and low-mass star-forming protostellar systems. Results: The 5 to 28mum MIRI spectrum of IRAS23385+6053 shows a plethora of features. While the general spectrum is typical for an embedded protostar, we see many atomic and molecular gas lines boosted by the higher spectral resolution and sensitivity compared to previous space missions. Furthermore, ice and dust absorption features are also present. Here, we focus on the continuum emission, outflow tracers like the H2, [FeII] and [NeII] lines as well as the potential accretion tracer Humphreys alpha HI(7--6). The short-wavelength MIRI data resolve two continuum sources A and B, where mid-infrared source A is associated with the main mm continuum peak. The combination of mid-infrared and mm data reveals a young cluster in its making. Combining the mid-infrared outflow tracer H2, [FeII] and [NeII] with mm SiO data shows a complex interplay of at least three molecular outflows driven by protostars in the forming cluster. Furthermore, the Humphreys alpha line is detected at a 3-4sigma level towards the mid-infrared sources A and B. Following Rigliaco et al. (2015), one can roughly estimate accretion luminosities and corresponding accretion rates between ~2.6x10^-6 and ~0.9x10^-4 M_sun/yr. This is discussed in the context of the observed outflow rates. Conclusions: The analysis of the MIRI MRS observations for this young high-mass star-forming region reveals connected outflow and accretion signatures., Comment: 12 pages, 9 figures, accepted for Astronomy & Astrophysics, the paper is also available at https://www2.mpia-hd.mpg.de/homes/beuther/papers.html

Context: While star formation on large molecular cloud scales and on small core and disk scales has been investigated intensely over the past decades, the connection of the large-scale interstellar material with the densest small-scale cores has been a largely neglected field. Methods: Using NOEMA and the IRAM 30\,m telescope, we mapped large areas (640\,arcmin$^2$) of the archetypical star formation complex Cygnus X at 3.6\,mm wavelengths in line and continuum emission. Results: The scope and outline of The Cygnus Allscale Survey of Chemistry and Dynamical Environments (CASCADE) is presented. We then focus on the first observed subregion in Cygnus X, namely the DR20 star formation site, which comprises sources in a range of evolutionary stages from cold pristine gas clumps to more evolved ultracompact H{\sc ii} regions. The data covering cloud to cores scales at a linear spatial resolution of $<5000$\,au reveal several kinematic cloud components that are likely part of several large-scale flows onto the central cores. The temperature structure of the region is investigated by means of the HCN/HNC intensity ratio and compared to dust-derived temperatures. We find that the deuterated DCO$^+$ emission is almost exclusively located toward regions at low temperatures below 20\,K. Investigating the slopes of spatial power spectra of dense gas tracer intensity distributions (HCO$^+$, H$^{13}$CO$^+$, and N$_2$H$^+$), we find comparatively flat slopes between $-2.9$ and $-2.6$, consistent with high Mach numbers and/or active star formation in DR20., Comment: 18 pages, 16 figures, accepted to A&A, also available at https://www2.mpia-hd.mpg.de/homes/beuther/papers.html

We aim to characterize the physical and chemical properties of fragmented cores during the earliest evolutionary stages in the very young star-forming regions ISOSS J22478+6357 and ISOSS J23053+5953. NOEMA 1.3 mm data are used in combination with archival mid- and far-infrared observations to construct and fit the SEDs of individual fragmented cores. The radial density profiles are inferred from the 1.3 mm continuum visibility profiles and the radial temperature profiles are estimated from H2CO rotation temperature maps. Molecular column densities are derived with the line fitting tool XCLASS. The physical and chemical properties are combined by applying the physical-chemical model MUSCLE in order to constrain the chemical timescales of a few line-rich cores. The morphology and spatial correlations of the molecular emission are analyzed using the HOG method. The mid-infrared data show that both regions contain a cluster of young stellar objects. Bipolar molecular outflows are observed in the CO 2-1 transition toward the strong mm cores indicating protostellar activity. We find strong molecular emission of SO, SiO, H2CO, and CH3OH in locations which are not associated with the mm cores. These shocked knots can be either associated with the bipolar outflows or, in the case of ISOSS J23053+5953, with a colliding flow that creates a large shocked region between the mm cores. The mean chemical timescale of the cores is lower (20 000 yr) compared to that of the sources of the more evolved CORE sample (60 000 yr). With the HOG method, we find that the spatial emission of species tracing the extended emission and of shock-tracing molecules are well correlated within transitions of these groups., Comment: 34 pages, 17 figures, accepted for publication in A&A

Increasing evidence suggests that, similar to their low-mass counterparts, high-mass stars form through a disk-mediated accretion process. At the same time, formation of high-mass stars still necessitates high accretion rates, and hence, high gas densities, which in turn can cause disks to become unstable against gravitational fragmentation. We study the kinematics and fragmentation of the disk around the high-mass star forming region AFGL 2591-VLA 3 which was hypothesized to be fragmenting based on the observations that show multiple outflow directions. We use a new set of high-resolution (0.19 arcsec) IRAM/NOEMA observations at 843 micron towards VLA 3 which allow us to resolve its disk, characterize the fragmentation, and study its kinematics. In addition to the 843 micron continuum emission, our spectral setup targets warm dense gas and outflow tracers such as HCN, HC$_3$N and SO$_2$, as well as vibrationally excited HCN lines. The high resolution continuum and line emission maps reveal multiple fragments with subsolar masses within the inner 1000 AU of VLA 3. Furthermore, the velocity field of the inner disk observed at 843 micron shows a similar behavior to that of the larger scale velocity field studied in the CORE project at 1.37 mm. We present the first observational evidence for disk fragmentation towards AFGL 2591-VLA 3, a source that was thought to be a single high-mass core. While the fragments themselves are low-mass, the rotation of the disk is dominated by the protostar with a mass of 10.3$\pm 1.8~M_{\odot}$. These data also show that NOEMA Band 4 can obtain the highest currently achievable spatial resolution at (sub-)mm wavelengths in observations of strong northern sources., Comment: 16 pages, 11 figures, Accepted for publication in A&A

Context: The formation of high-mass star-forming regions from their parental gas cloud and the subsequent fragmentation processes lie at the heart of star formation research. Aims: We aim to study the dynamical and fragmentation properties at very early evolutionary stages of high-mass star formation. Methods: Employing the NOrthern Extended Millimeter Array (NOEMA) and the IRAM 30m telescope, we observed two young high-mass star-forming regions, ISOSS22478 and ISOSS23053, in the 1.3mm continuum and spectral line emission at a high angular resolution (~0.8''). Results: We resolved 29 cores that are mostly located along filament-like structures. Depending on the temperature assumption, these cores follow a mass-size relation of approximately M~r^2.0, corresponding to constant mean column densities. However, with different temperature assumptions, a steeper mass-size relation up to M~r^3.0, which would be more likely to correspond to constant mean volume densities, cannot be ruled out. The correlation of the core masses with their nearest neighbor separations is consistent with thermal Jeans fragmentation. We found hardly any core separations at the spatial resolution limit, indicating that the data resolve the large-scale fragmentation well. Although the kinematics of the two regions appear very different at first sight - multiple velocity components along filaments in ISOSS22478 versus a steep velocity gradient of more than 50km/s/pc in ISOSS23053 - the findings can be explained within the framework of a dynamical cloud collapse scenario. Conclusions: While our data are consistent with a dynamical cloud collapse scenario and subsequent thermal Jeans fragmentation, the importance of additional environmental properties, such as the magnetization of the gas or external shocks triggering converging gas flows, is nonetheless not as well constrained and would require future investigation., Comment: 16 pages, 16 figures, accepted for Astronomy and Astrophysics, a higher-resolution version can also be found at https://www.mpia.de/homes/beuther/papers.html

We use sub-arcsecond resolution ($\sim$0.4$''$) observations with NOEMA at 1.37 mm to study the dust emission and molecular gas of 18 high-mass star-forming regions. We combine the derived physical and chemical properties of individual cores in these regions to estimate their ages. The temperature structure of these regions are determined by fitting H2CO and CH3CN line emission. The density profiles are inferred from the 1.37 mm continuum visibilities. The column densities of 11 different species are determined by fitting the emission lines with XCLASS. Within the 18 observed regions, we identify 22 individual cores with associated 1.37 mm continuum emission and with a radially decreasing temperature profile. We find an average temperature power-law index of q = 0.4$\pm$0.1 and an average density power-law index of p = 2.0$\pm$0.2 on scales on the order of several 1 000 au. Comparing these results with values of p derived in the literature suggest that the density profiles remain unchanged from clump to core scales. The column densities relative to N(C18O) between pairs of dense gas tracers show tight correlations. We apply the physical-chemical model MUSCLE to the derived column densities of each core and find a mean chemical age of $\sim$60 000 yrs and an age spread of 20 000-100 000 yrs. With this paper we release all data products of the CORE project available at https://www.mpia.de/core. The CORE sample reveals well constrained density and temperature power-law distributions. Furthermore, we characterize a large variety in molecular richness that can be explained by an age spread confirmed by our physical-chemical modeling. The hot molecular cores show the most emission lines, but we also find evolved cores at an evolutionary stage, in which most molecules are destroyed and thus the spectra appear line-poor again., Comment: 29 pages, 14 figures, accepted for publication in A&A

In the massive star-forming region IRAS 21078+5211, a highly fragmented cluster (0.1~pc in size) of molecular cores is observed, located at the density peak of an elongated (1~pc in size) molecular cloud. A small (1~km/s per 0.1~pc) LSR velocity (Vlsr) gradient is detected across the axis of the molecular cloud. Assuming we are observing a mass flow from the harboring cloud to the cluster, we derive a mass infall rate of about 10^{-4}~M_{sun}~yr^{-1}. The most massive cores (labeled 1, 2, and 3) are found at the center of the cluster, and these are the only ones that present a signature of protostellar activity in terms of emission from high-excitation molecular lines or a molecular outflow. We reveal an extended (size about 0.1~pc), bipolar collimated molecular outflow emerging from core 1. We believe this is powered by a (previously discovered) compact (size <= 1000~au) radio jet, ejected by a YSO embedded in core 1 (named YSO-1), since the molecular outflow and the radio jet are almost parallel and have a comparable momentum rate. By means of high-excitation lines, we find a large (14~km/s over 500~au) Vlsr gradient at the position of YSO-1, oriented approximately perpendicular to the radio jet. Assuming this is an edge-on, rotating disk and fitting a Keplerian rotation pattern, we determine the YSO-1 mass to be 5.6+/-2.0~M_{sun}. The water masers (previously observed with VLBI) emerge within 100-300~au from YSO-1 and are unique tracers of the jet kinematics. Their three-dimensional (3D) velocity pattern reveals that the gas flows along, and rotates about, the jet axis. We show that the 3D maser velocities are fully consistent with the magneto-centrifugal disk-wind models predicting a cylindrical rotating jet. Under this hypothesis, we determine the jet radius to be about 16~au and the corresponding launching radius and terminal velocity to be about 2.2~au and 200~km/s, respectively., Comment: 25 pages, 16 figures

The formation of hot stars out of the cold interstellar medium lies at the heart of astrophysical research. Understanding the importance of magnetic fields during star formation remains a major challenge. With the advent of the Atacama Large Millimeter Array, the potential to study magnetic fields by polarization observations has tremendously progressed. However, the major question remains how much magnetic fields shape the star formation process or whether gravity is largely dominating. Here, we show that for the high-mass star-forming region G327.3 the magnetic field morphology appears to be dominantly shaped by the gravitational contraction of the central massive gas core where the star formation proceeds. We find that in the outer parts of the region, the magnetic field is directed toward the gravitational center of the region. Filamentary structures feeding the central core exhibit U-shaped magnetic field morphologies directed toward the gravitational center as well, again showing the gravitational drag toward the center. The inner part then shows rotational signatures, potentially associated with an embedded disk, and there the magnetic field morphology appears to be rotationally dominated. Hence, our results demonstrate that for this region gravity and rotation are dominating the dynamics and shaping the magnetic field morphology., Comment: 10 pages, 4 figures, accepted for the Astrophysical Journal, also available at https://www2.mpia-hd.mpg.de/homes/beuther/papers.html

We have studied the dust density, temperature and velocity distributions of the archetypal massive young stellar object (MYSO) AFGL 2591. Given its high luminosity ($L=2 \times 10^5$ L$_\odot$) and distance ($d=3.3$ kpc), AFGL 2591 has one of the highest $\sqrt{L}/d$ ratio, giving better resolved dust emission than any other MYSO. As such, this paper provides a template on how to use resolved multi-wavelength data and radiative transfer to obtain a well-constrained 2-D axi-symmetric analytic rotating infall model. We show for the first time that the resolved dust continuum emission from Herschel 70 $\mu$m observations is extended along the outflow direction, whose origin is explained in part from warm dust in the outflow cavity walls. However, the model can only explain the kinematic features from CH$_3$CN observations with unrealistically low stellar masses ($<15$ M$_\odot$), indicating that additional physical processes may be playing a role in slowing down the envelope rotation. As part of our 3-step continuum and line fitting, we have identified model parameters that can be further constrained by specific observations. High-resolution mm visibilities were fitted to obtain the disc mass (6 M$_\odot$) and radius (2200 au). A combination of SED and near-IR observations were used to estimate the luminosity and envelope mass together with the outflow cavity inclination and opening angles., Comment: 34 pages, 22 figures, 15 tables, 4 appendices. Accepted for publication in MNRAS

We present a detailed observational and modeling study of the hot core VLA 3 in the high-mass star-forming region AFGL 2591, which is a target region of the NOrthern Extended Millimeter Array (NOEMA) large program CORE. Using NOEMA observations at 1.37 mm with an angular resolution of ~0."42 (1 400 au at 3.33 kpc), we derived the physical and chemical structure of the source. We modeled the observed molecular abundances with the chemical evolution code MUSCLE (MUlti Stage ChemicaL codE). Results. With the kinetic temperature tracers CH3CN and H2CO we observe a temperature distribution with a power-law index of q = 0.41+-0.08. Using the visibilities of the continuum emission we derive a density structure with a power-law index of p = 1.7+-0.1. The hot core spectra reveal high molecular abundances and a rich diversity in complex molecules. The majority of the molecules have an asymmetric spatial distribution around the forming protostar(s), which indicates a complex physical structure on scales < 1 400 au. Using MUSCLE, we are able to explain the observed molecular abundance of 10 out of 14 modeled species at an estimated hot core chemical age of ~21 100 years. In contrast to the observational analysis, our chemical modeling predicts a lower density power-law index of p < 1.4. Reasons for this discrepancy are discussed. Conclusions. Combining high spatial resolution observations with detailed chemical modeling allows us to derive a concise picture of the physical and chemical structure of the famous AFGL 2591 hot core. The next steps are to conduct a similar analysis for the whole CORE sample, and then use this analysis to constrain the chemical diversity in high-mass star formation to a much greater depth., Comment: 22 pages, 13 figures, accepted for publication in A&A

This study is part of the project ``CORE'', an IRAM/NOEMA large program consisting of observations of the millimeter continuum and molecular line emission towards 20 selected high-mass star forming regions. We focus on IRAS23385+6053, which is believed to be the least evolved source of the CORE sample. The observations were performed at ~1.4 mm and employed three configurations of NOEMA and additional single-dish maps, merged with the interferometric data to recover the extended emission. Our correlator setup covered a number of lines from well-known hot core tracers and a few outflow tracers. The angular (~0.45"$-$0.9") and spectral (0.5 km/s) resolutions were sufficient to resolve the clump in IRAS23385+6053 and investigate the existence of large-scale motions due to rotation, infall, or expansion. We find that the clump splits into six distinct cores when observed at sub-arcsecond resolution. These are identified through their 1.4 mm continuum and molecular line emission. We produce maps of the velocity, line width, and rotational temperature from the methanol and methyl cyanide lines, which allow us to investigate the cores and reveal a velocity and temperature gradient in the most massive core. We also find evidence of a bipolar outflow, possibly powered by a low-mass star. We present the tentative detection of a circumstellar self-gravitating disk lying in the most massive core and powering a large-scale outflow previously known in the literature. In our scenario, the star powering the flow is responsible for most of the luminosity of IRAS23385+6053 (~$3000~L_\odot$). The other cores, albeit with masses below the corresponding virial masses, appear to be accreting material from their molecular surroundings and are possibly collapsing or on the verge of collapse. We conclude that we are observing a sample of star-forming cores that is bound to turn into a cluster of massive stars.

Aims: We aim to understand the fragmentation as well as the disk formation, outflow generation and chemical processes during high-mass star formation on spatial scales of individual cores. Methods: Using the IRAM Northern Extended Millimeter Array (NOEMA) in combination with the 30m telescope, we have observed in the IRAM large program CORE the 1.37mm continuum and spectral line emission at high angular resolution (~0.4'') for a sample of 20 well-known high-mass star-forming regions with distances below 5.5kpc and luminosities larger than 10^4Lsun. Results: We present the overall survey scope, the selected sample, the observational setup and the main goals of CORE. Scientifically, we concentrate on the mm continuum emission on scales on the order of 1000AU. We detect strong mm continuum emission from all regions, mostly due to the emission from cold dust. The fragmentation properties of the sample are diverse. We see extremes where some regions are dominated by a single high-mass core whereas others fragment into as many as 20 cores. A minimum-spanning-tree analysis finds fragmentation at scales on the order of the thermal Jeans length or smaller suggesting that turbulent fragmentation is less important than thermal gravitational fragmentation. The diversity of highly fragmented versus singular regions can be explained by varying initial density structures and/or different initial magnetic field strengths. Conclusions: The smallest observed separations between cores are found around the angular resolution limit which indicates that further fragmentation likely takes place on even smaller spatial scales. The CORE project with its numerous spectral line detections will address a diverse set of important physical and chemical questions in the field of high-mass star formation., Comment: 29 pages, 17 figures, Astronomy & Astrophysics in press, for a higher-resolution version of the paper see http://www.mpia.de/homes/beuther/papers.html