Search Results
The SEDIGISM survey: A search for molecular outflows
2022, Yang, A.Y., Urquhart, J.S., Wyrowski, F., Thompson, M.A., König, C., Colombo, D., Menten, K.M., Duarte-Cabral, A., Schuller, F., Csengeri, T., Eden, D., Barnes, P., Traficante, A., Bronfman, L., Sanchez-Monge, A., Ginsburg, A., Cesaroni, R., Lee, M.-Y., Beuther, H., Medina, S.-N.X., Mazumdar, P., Henning, T.
Context. The formation processes of massive stars are still unclear, but a picture is emerging involving accretion disks and molecular outflows in what appears to be a scaled-up version of low-mass star formation. A census of outflow activity toward high-mass star-forming clumps in various evolutionary stages has the potential to shed light on high-mass star formation. Aims. We conducted an outflow survey toward ATLASGAL (APEX Telescope Large Area Survey of the Galaxy) clumps using SEDIGISM (structure, Excitation, and Dynamics of the Inner Galactic InterStellar Medium) data and aimed to obtain a large sample of clumps exhibiting outflow activity in different evolutionary stages. Methods. We identify the high-velocity wings of the 13CO lines, which indicate outflow activity, toward ATLASGAL clumps by (1) extracting the simultaneously observed 13CO (2-1) and C18O (2-1) spectra from SEDIGISM, and (2) subtracting Gaussian fits to the scaled C18O (core emission) from the 13CO line after considering opacity broadening. Results. We detected high-velocity gas toward 1192 clumps out of a total sample of 2052, corresponding to an overall detection rate of 58%. Outflow activity has been detected in the earliest (apparently) quiescent clumps (i.e., 70 μm weak) to the most evolved H » II region stages (i.e., 8 μm bright with tracers of massive star formation). The detection rate increases as a function of evolution (quiescent = 51%, protostellar = 47%, YSO = 57%, UC H » II regions = 76%). Conclusions. Our sample is the largest outflow sample identified so far. The high detection rate from this large sample is consistent with the results of similar studies reported in the literature and supports the scenario that outflows are a ubiquitous feature of high-mass star formation. The lower detection rate in early evolutionary stages may be due to the fact that outflows in the early stages are weak and difficult to detect. We obtain a statistically significant sample of outflow clumps for every evolutionary stage, especially for outflow clumps in the earliest stage (i.e., 70 μm dark). The detections of outflows in the 70 μm dark clumps suggest that the absence of 70 μm emission is not a robust indicator of starless and/or pre-stellar cores.
Probing the structure of a massive filament: ArTéMiS 350 and 450 μm mapping of the integral-shaped filament in Orion A
2021, Schuller, F., André, Ph., Shimajiri, Y., Zavagno, A., Peretto, N., Arzoumanian, D., Csengeri, T., Könyves, V., Palmeirim, P., Pezzuto, S., Rigby, A., Roussel, H., Ajeddig, H., Dumaye, L., P. Gallais, P., Le Pennec, J., Martignac, J., Mattern, M., Revéret, V., Rodriguez, L., Talvard, M.
Context. The Orion molecular cloud is the closest region of high-mass star formation. It is an ideal target for investigating the detailed structure of massive star-forming filaments at high resolution and the relevance of the filament paradigm for the earliest stages of intermediate- to high-mass star formation. Aims. Within the Orion A molecular cloud, the integral-shaped filament (ISF) is a prominent, degree-long structure of dense gas and dust with clear signs of recent and ongoing high-mass star formation. Our aim is to characterise the structure of this massive filament at moderately high angular resolution (8′′ or ~0.016 pc) in order to measure the intrinsic width of the main filament, down to scales well below 0.1 pc, which has been identified as the characteristic width of filaments. Methods. We used the ArTéMiS bolometer camera at APEX to map a ~0.6 × 0.2 deg2 region covering OMC-1, OMC-2, and OMC-3 at 350 and 450 μm. We combined these data with Herschel-SPIRE maps to recover extended emission. The combined Herschel-ArTéMiS maps provide details on the distribution of dense cold material, with a high spatial dynamic range, from our 8′′ resolution up to the transverse angular size of the map, ~10-15′. By combining Herschel and ArTéMiS data at 160, 250, 350, and 450 μm, we constructed high-resolution temperature and H2 column density maps. We extracted radial intensity profiles from the column density map in several representative portions of the ISF, which we fitted with Gaussian and Plummer models to derive their intrinsic widths. We also compared the distribution of material traced by ArTéMiS with that seen in the higher-density tracer N2H+(1-0) that was recently observed with the ALMA interferometer. Results. All the radial profiles that we extracted show a clear deviation from a Gaussian, with evidence for an inner plateau that had not previously been seen clearly using Herschel-only data. We measure intrinsic half-power widths in the range 0.06-0.11 pc. This is significantly larger than the Gaussian widths measured for fibres seen in N2H+, which probably only traces the dense innermost regions of the large-scale filament. These half-power widths are within a factor of two of the value of ~0.1 pc found for a large sample of nearby filaments in various low-mass star-forming regions, which tends to indicate that the physical conditions governing the fragmentation of pre-stellar cores within transcritical or supercritical filaments are the same over a large range of masses per unit length. © F. Schuller et al. 2021.
Massive stars in extremely metal-poor galaxies: a window into the past
2021, Garcia, Miriam, Evans, Christopher J., Bestenlehner, Joachim M., Bouret, Jean Claude, Castro, Norberto, Cerviño, Miguel, Fullerton, Alexander W., Gieles, Mark, Herrero, Artemio, de Koter, Alexander, Lennon, Daniel J., van Loon, Jacco Th., Martins, Fabrice, de Mink, Selma E., Najarro, Francisco, Negueruela, Ignacio, Sana, Hugues, Simón-Díaz, Sergio, Szécsi, Dorottya, Tramper, Frank, Vink, Jorick S., Wofford, Aida
Cosmic history has witnessed the lives and deaths of multiple generations of massive stars, all of them invigorating their host galaxies with ionizing photons, kinetic energy, fresh material, and stellar-mass black holes. Ubiquitous engines as they are, astrophysics needs a good understanding of their formation, evolution, properties and yields throughout the history of the Universe, and with decreasing metal content mimicking the environment at the earliest epochs. Ultimately, a physical model that could be extrapolated to zero metallicity would enable tackling long-standing questions such as “What did the first, very massive stars of the Universe look like?” or “What was their role in the re-ionization of the Universe?” Yet, most of our knowledge of metal-poor massive stars is drawn from one single point in metallicity. Massive stars in the Small Magellanic Cloud (SMC, ∼1/5Z⊙ ) currently serve as templates for low-metallicity objects in the early Universe, even though significant differences with respect to massive stars with poorer metal content have been reported. This White Paper summarizes the current knowledge on extremely (sub-SMC) metal poor massive stars, highlighting the most outstanding open questions and the need to supersede the SMC as standard. A new paradigm can be built from nearby extremely metal-poor galaxies that make a new metallicity ladder, but massive stars in these galaxies are out of reach to current observational facilities. Such a task would require an L-size mission, consisting of a 10m-class space telescope operating in the optical and the ultraviolet ranges. Alternatively, we propose that ESA unites efforts with NASA to make the LUVOIR mission concept a reality, thus continuing the successful partnership that made the Hubble Space Telescope one of the greatest observatories of all time.