Astronomy & Astrophysics最新文献

{"title":"Revisiting the massive star-forming complex RCW 122: New millimeter and submillimeter study","authors":"N. Duronea, L. Bronfman, M. Ortega, L. Suad, G. Baume, E. Mendoza, M. Carvajal, S. Cichowolski, E. M. Arnal, R. Finger, M. Merello, R. Gamen","doi":"10.1051/0004-6361/202349136","DOIUrl":"https://doi.org/10.1051/0004-6361/202349136","url":null,"abstract":"In this paper, we present a new multifrequency study of the giant star-forming complex RCW,122. We used molecular data obtained with the ASTE 10 m and the APEX 12 m telescopes, along with infrared observations spanning from 3.6 to 870 obtained from available databases. We also incorporated a range of public datasets, including the radio continuum at 3 GHz, narrowband Halpha images, and deep JHK photometry. Our analysis focuses mostly on cataloged ATLASGAL sources, showcasing a spectrum of evolutionary stages from infrared dark cloud (IRDC)/high-mass protostellar object (HMPO) to ultra-compact HII region (UCHII), as inferred from preliminary inspections of the public dataset. Based on ASTE HCO$^+$(4--3) and CO(3--2) data, we identified five molecular clumps, designated A, B, C, D, and E, as molecular counterparts of the ATLASGAL sources. These clumps have radial velocities ranging from sim --15 to --10 confirming their association with RCW,122. In addition, we report the detection of 20 transitions from 11 distinct molecules in the APEX spectra in the frequency ranges from 228.538 GHz to 232.538 GHz and 218.3 to 222.3 GHz, unveiling a diverse chemical complexity among the clumps. Utilizing CO(2--1) and C18O(2--1) data taken from the observations with the APEX telescope we estimated the total LTE molecular mass, ranging from 200 $M_ odot $ (clump A) to 4400 $M_ odot $ (clump B). Our mid- to far-infrared (MIR-FIR) flux density analysis yielded minimum dust temperatures of 23.7 K (clump A) to maximum temperatures of 33.9 K (clump B), indicating varying degrees of internal heating among the clumps. The bolometric luminosities span 1.7times 10$^3$ L$_ odot $ (clump A) to 2.4times 10$^5$ L$_ odot $ (clump B), while the total (dust+gas) mass ranges from 350 $M_ odot $ (clump A) to 3800 $M_ odot $ (clump B). Our analysis of the molecular line richness, $L/M$ ratios, and CH$_3$CCH and dust temperatures reveals an evolutionary sequence of A/Erightarrow Crightarrow D/B, consistent with preliminary inferences of the ATLASGAL sources. In this context, clumps A and E exhibit early stages of collapse, with clump A likely in an early HMPO phase, which is supported by identifying a candidate molecular outflow. Clump E appears to be in an intermediate stage between IRDC and HMPO. Clumps D and B show evidence of being in the UCHII phase, with clump B likely more advanced. Clump C likely represents an intermediate stage between HMPO and HMC. Our findings suggest clump B is undergoing ionization and heating by multiple stellar and protostellar members of the stellar cluster DBS,119. Meanwhile, other cluster members may be responsible for ionizing other regions of RCW,122 that have evolved into fully developed HII regions, beyond the molecular dissociation stage.","PeriodicalId":8585,"journal":{"name":"Astronomy & Astrophysics","volume":"119 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141812000","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Two-dimensional simulations of disks in close binaries. Simulating outburst cycles in cataclysmic variables","authors":"Lucas M. Jordan, Dennis Wehner, Rolf Kuiper","doi":"10.1051/0004-6361/202348726","DOIUrl":"https://doi.org/10.1051/0004-6361/202348726","url":null,"abstract":"Previous simulations of cataclysmic variables studied either the\u0000 quiescence, or the outburst state in multiple dimensions or they simulated complete outburst cycles\u0000 in one dimension using simplified models for the gravitational torques. We self-consistently simulate complete outburst cycles\u0000 of normal and superoutbursts in cataclysmic variable systems in two dimensions.\u0000 We study the effect of different alpha viscosity parameters, mass transfer rates,\u0000 and binary mass ratios on the disk luminosities, outburst occurrence rates, and superhumps. We simulate non-isothermal, viscous accretion disks in cataclysmic variable systems\u0000 using a modified version of the Fargo code with an updated equation of state\u0000 and a cooling function designed to reproduce s-curve behavior. Our simulations can model complete outburst cycles\u0000 using the thermal tidal instability model.\u0000 We find higher superhump amplitudes and stronger gravitational torques \u0000 than previous studies, resulting in better agreement with observations.","PeriodicalId":8585,"journal":{"name":"Astronomy & Astrophysics","volume":"53 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141810463","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Extragalactic 85Rb/87Rb and 6Li/ ^7Li ratios in the Small Magellanic Cloud","authors":"P. Molaro, P. Bonifacio, G. Cupani, J. C. Howk","doi":"10.1051/0004-6361/202449529","DOIUrl":"https://doi.org/10.1051/0004-6361/202449529","url":null,"abstract":"The line of sight toward Sk 143 (AzV 456), an O9.5 Ib star in the Small Magellanic Cloud (SMC), shows significant\u0000absorption from neutral atoms and molecules. We report a new study of this line of sight by means of high-resolution spectra obtained with the ESPRESSO spectrograph at the VLT of ESO. The absorption from neutral and ionized species is well characterized by a single component at v$_ hel $ approx +132 that was modeled with the ASTROCOOK code. The \u0000 rubidium Rb I 780.0 nm line is detected for the first time outside the Galaxy, and we derive Rb/H = -1.86 pm 0.09. As a result of the high resolution, the 85Rb and 87Rb isotope lines are also exceptionally well resolved. The 85Rb/87Rb isotope ratio is 0.46, which\u0000 is opposite of the meteoritic value of 2.43. \u0000 This implies that Rb is made through a dominant contribution of the $r$-process, which is dominant for the 87Rb isotope. We also confirm the presence of 670.7 nm and set a limit on the isotopic ratio of $^6$Li/$^7Li$ < 0.1. The dominance of the 87Rb isotope implies that Rb is made through a dominant contribution of the $r$-process. At the low metallicity of the cloud of Zn/H = -1.28 pm 0.09 , neutron rich material may have occurred in rotating metal-poor massive stars. Moreover, the\u0000 low metallicity of the cloud leads to an absolute Li abundance of A($^7$Li) approx 2.2, which differs from the expectation from big bang nucleosynthesis. Because the gas-phase abundance is not affected by stellar depletion, the burning of Li inside the halo stars is probably not the solution for the cosmological $^7$Li problem.","PeriodicalId":8585,"journal":{"name":"Astronomy &amp; Astrophysics","volume":"141 7","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141811135","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The 2024 KIDA network for interstellar chemistry","authors":"V. Wakelam, P. Gratier, J. Loison, K. M. Hickson, J. Penguen, A. Mechineau","doi":"10.1051/0004-6361/202450606","DOIUrl":"https://doi.org/10.1051/0004-6361/202450606","url":null,"abstract":"The study of the chemical composition of the interstellar medium (ISM) requires a strong synergy between laboratory astrophysics, modeling, and observations. In particular, astrochemical models have been developed for decades now and include an increasing number of processes studied in the laboratory or theoretically. These models follow the chemistry both in the gas phase and at the surface of interstellar grains. Since 2012, we have provided complete gas-phase chemical networks for astrochemical codes that can be used to model various environments of the ISM. Our aim is to introduce the new up-to-date astrochemical network kida.uva.2024 together with the ice chemical network and the fortran code to compute time dependent compositions of the gas, the ice surface, and the ice mantles under physical conditions relevant for the ISM. The gas-phase chemical reactions, as well as associated rate coefficients, included in kida.uva.2024 were carefully selected from the KIDA online database and represent the most recent values. The model predictions for cold core conditions and for when considering only gas-phase processes were computed as a function of time and compared to the predictions obtained with the previous version, kida.uva.2014. In addition, key chemical reactions were identified. The model predictions, including both gas and surface processes, were compared to the molecular abundances as observed in the cold core TMC1-CP. Many gas-phase reactions were revised or added to produce kida.uva.2024. The new model predictions are different by several orders of magnitude for some species. The agreement of this new model with observations in TMC-1 (CP) is, however, similar to the one obtained with the previous network.","PeriodicalId":8585,"journal":{"name":"Astronomy &amp; Astrophysics","volume":"16 11","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141816925","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Imprint of the magnetic activity cycle on solar asteroseismic characterisation based on 26 years of GOLF and BiSON data","authors":"J. B'etrisey, Martin Farnir, S. Breton, Rafael A. Garc'ia, A. Broomhall, A. Amarsi, Oleg Kochukhov","doi":"10.1051/0004-6361/202451365","DOIUrl":"https://doi.org/10.1051/0004-6361/202451365","url":null,"abstract":"Asteroseismic modelling will play a key role in future space-based missions, such as PLATO, CubeSpec, and Roman. Despite remarkable achievements, asteroseismology has revealed significant discrepancies between observations and theoretical predictions of the physics used in stellar models, which have the potential to bias stellar characterisation at the precision level demanded by PLATO. The current modelling strategies largely overlook magnetic activity, assuming that its effects are masked within the parametrisation of the so-called `surface effects'. Given the presence of activity cycles in multiple solar-like oscillators and activity variations in a significant fraction of Kepler observations of main-sequence stars, it is therefore relevant to investigate systematic errors in asteroseismic characterisations caused by our incomplete understanding of magnetic activity. Based on 26.5 years of GOLF and BiSON observations, we measured the impact of magnetic activity on the asteroseismic characterisation of the Sun as a star, a reference target for assessing the PLATO mission requirements. The GOLF and BiSON observations, which fully cover solar cycles 23 and 24, were divided into yearly overlapping snapshots, each delayed by a quarter of a year. For each snapshot, an advanced asteroseismic characterisation, similar to that to be adopted by the PLATO pipeline, was performed with standard prescriptions for the parametrisation of the surface effects. This allowed us to monitor the apparent temporal evolution of fundamental solar parameters such as mass, radius, and age. The correlation of these parameters with the 10.7 cm radio emission flux, a proxy of the solar activity cycle, was then measured. The effects of magnetic activity are partially absorbed into the parametrisation of the surface effects when suitable\u0000prescriptions are used, and they do not significantly affect the measured solar mass or radius. However, contrary to literature expectations, we find a significant imprint on the age determination, with variations of up to 6.5 between solar minima and maxima. This imprint persists across both BiSON and GOLF datasets. Considering that the Sun exhibits low levels of activity, our study highlights the looming challenge posed by magnetic activity for future photometry missions, and it prompts a potential reevaluation of the asteroseismic characterisation of the most active Kepler targets.","PeriodicalId":8585,"journal":{"name":"Astronomy &amp; Astrophysics","volume":"22 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141815961","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"More sulphur in TMC-1: Discovery of the NC_3S and HC_3S radicals with the QUIJOTE line survey","authors":"J.Cernicharo, C.Cabezas, M. Ag'undez, R. Fuentetaja, B. Tercero, N. Marcelino, P. D. Vicente","doi":"10.1051/0004-6361/202451256","DOIUrl":"https://doi.org/10.1051/0004-6361/202451256","url":null,"abstract":"We present the detection of the free radicals NC$_3$S and HC$_3$S towards TMC-1\u0000with the QUIJOTE line survey. The derived column densities are (1.4pm 0.2)times 1011 for NC$_3$S and \u0000(1.5pm 0.2)times 1011 for HC$_3$S. We searched for NCCS, but only three transitions are within the \u0000domain of our QUIJOTE line\u0000survey and the observed lines are marginally detected at the 3sigma level, providing an upper limit to its \u0000column density of leq 6times 1010 cm$^ $.\u0000We also unsuccessfully searched for longer species of the NC$_n$S (nge 4) and HC$_n$S (nge 5)\u0000families in our TMC-1 data. A chemical model based on \u0000a reduced set of reactions involving HC$_3$S and NC$_3$S predicts abundances that are 10-100 times \u0000below the observed values. These calculations indicate that the most efficient reactions of formation \u0000of HC$_3$S and NC$_3$S in the model are S + C$_3$H$_2$ and N + HC$_3$S, respectively, while both radicals \u0000are very efficiently \u0000destroyed through reactions with neutral atoms.","PeriodicalId":8585,"journal":{"name":"Astronomy &amp; Astrophysics","volume":"80 21","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141818849","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Abundances of neutron-capture elements in selected solar-type stars","authors":"Valentina Sheminova, M. Baratella, V. D’Orazi","doi":"10.1051/0004-6361/202449753","DOIUrl":"https://doi.org/10.1051/0004-6361/202449753","url":null,"abstract":"The primary objective of this study is to accurately determine the abundances of Cu, Sr, Y, Zr, Ba, La, and Ce in selected solar-type stars. This will allow us to establish observational abundance--metallicity and abundance--age relations and to explore the reasons for the excess of Ba compared to other $s$-elements in younger solar-type stars. The chosen $s$-process elements are critical diagnostics for understanding the chemical evolution of our Galaxy. We analysed HARPS spectra with a high resolution ($R$ = 115,000) and high signal-to-noise ratio (close to 100) of main-sequence solar-type FGK stars with metallicities from $-0.15$ to +0.35 dex and ages from 2 to 14 Gyr using one-dimensional (1D) local thermodynamic equilibrium (LTE) synthesis and MARCS atmospheric models. In the procedure of fitting synthetic to observed line profiles, the free parameters included abundance and microturbulent and macroturbulent velocity. The macroturbulent velocity can substantially compensate for non-local thermodynamic equilibrium (NLTE) effects in the line core. The resulting elemental abundance X/H increases with metallicity and age for solar-type stars.\u0000The ratio of the abundances of $s$-process elements s/Fe increases with decreasing metallicity and age, while the Cu/Fe ratio increases with both metallicity and age. These observed trends agree well with published observational data and with predictions from Galactic chemical evolution (GCE) models. A small Ba/Fe enhancement of 0.08 ± 0.08 dex has been detected in seven younger stars with an average age of $2.8 0.6$ Gyr. Compared to the abundances of other $s$-process elements Ba/Fe is 0.07 and 0.08 dex higher than La and Ce on average, respectively. Furthermore, we find that the Ba/Fe ratio increases with increasing chromospheric activity.\u0000The average Ba/Fe for the three most active stars is $0.15 0.10$ dex higher than that of the other stars. Chromospheric activity, characterised by stronger magnetic fields found in active regions such as pores, spots, plages, and networks, can significantly alter the physical conditions in the formation layers of the Ba lines. Our primary conclusion is that to account for the observed excess of Ba/Fe abundance in younger stars, it is essential to use more complex atmospheric models that incorporate magnetic structures.","PeriodicalId":8585,"journal":{"name":"Astronomy &amp; Astrophysics","volume":"23 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141819511","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hydrodynamical simulations of wind interaction in spider systems. A step toward understanding transitional millisecond pulsars","authors":"C. Guerra, Z. Meliani, G. Voisin","doi":"10.1051/0004-6361/202450638","DOIUrl":"https://doi.org/10.1051/0004-6361/202450638","url":null,"abstract":"The detected population of \"spiders\", referring to millisecond pulsar binaries, has significantly grown in the past decade thanks to multiwavelength follow-up investigations of unidentified Fermi sources. These systems consist of low-mass stellar companions orbiting rotation-powered millisecond pulsars in short periods of a few hours up to day. Among them, a subset of intriguing objects called transitional millisecond pulsars (tMSPs) has been shown to exhibit a remarkable behavior, transitioning between pulsar-binary and faint low-mass X-ray binary states over a span of a few years. Our objective is to study the interaction of stellar winds in tMSPs in order to understand their observational properties. To this end we focus on the parameter range that places the system near Roche-lobe overflow. Employing the adaptative mesh refinement (AMR) AMRVAC 2.0 code, we performed 2D hydrodynamical (HD) simulations of the interaction between the flows from both stars, accounting for the effects of gravity and orbital motion. By studying the mass loss and launch speed of the winds, we successfully recreated two phenomenologically distinct regimes: the accretion stream and the pulsar radio state. We also identified the tipping point that marks the sharp transition between these two states. In the accretion stream state, we discover a very strong variability induced by the pulsar wind. In the pulsar state, we reconstructed the corresponding X-ray light curves of the system that produces the characteristic double-peak pattern of these systems. The position of the peaks is shifted due to orbital motion and the leading peak is weaker due to eclipsing by the companion. This study highlights the importance of gravity and orbital motion in the interaction between the companion and pulsar winds.\u0000 Our setup allows the study of the complex interaction between the pulsar wind and an accretion stream during mass transfer.\u0000 We suggest that a smaller leading peak in X-rays is indicative of a nearly edge-on system.","PeriodicalId":8585,"journal":{"name":"Astronomy &amp; Astrophysics","volume":"125 10","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141819549","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"MINDS. Hydrocarbons detected by JWST/MIRI in the inner disk of Sz28 consistent with a high C/O gas-phase chemistry","authors":"J. Kanwar, I. Kamp, H. Jang, L. Waters, E. V. Dishoeck, V. Christiaens, A. M. Arabhavi, Thomas K. Henning, M. Gudel, P. Woitke, Olivier Absil, D. Barrado, A. C. O. Garatti, A. Glauser, F. Lahuis, S. Scheithauer, B. Vandenbussche, D. Gasman, S. Grant, N. Kurtovic, G. Perotti, B. Tabone, M. Temmink","doi":"10.1051/0004-6361/202450078","DOIUrl":"https://doi.org/10.1051/0004-6361/202450078","url":null,"abstract":"With the advent of JWST, we are acquiring unprecedented insights into the physical and chemical structure of the inner regions of planet-forming disks where terrestrial planet formation occurs. Very low-mass stars (VLMSs) are known to have a high occurrence of the terrestrial planets orbiting them. Exploring the chemical composition of the gas in these inner disk regions can help us better understand the connection between planet-forming disks and planets. sun We used the dust-fitting tool DuCK to determine the dust continuum and to place constraints on the dust composition and grain sizes. We used 0D slab models to identify and fit the molecular spectral features, which yielded estimates on the temperature, column density, and emitting area. To test our understanding of the chemistry in the disks around VLMSs, we employed the thermo-chemical disk model P RO D I M O and investigated the reservoirs of the detected hydrocarbons. We explored how the C/O ratio affects the inner disk chemistry. JWST reveals a plethora of hydrocarbons, including CH3 CH4 C2H2 CCH2 C2H6 C3H4 C4H2 and C6H6 which suggests a disk with a gaseous C/O,>,1. Additionally, we detect CO2 CO2 HCN and HC3N H2O and OH are absent from the spectrum. We do not detect polycyclic aromatic hydrocarbons. Photospheric stellar absorption lines of H2O and CO are identified. Notably, our radiation thermo-chemical disk models are able to produce these detected hydrocarbons in the surface layers of the disk when C/O,>,1. The presence of C C+ H, and H2 is crucial for the formation of hydrocarbons in the surface layers, and a C/O ratio larger than 1 ensures the surplus of C needed to drive this chemistry. Based on this, we predict a list of additional hydrocarbons that should also be detectable. Both amorphous and crystalline silicates (enstatite and forsterite) are present in the disk and we find grain sizes of 2 and 5,mu m. The disk around Sz28 is rich in hydrocarbons, and its inner regions have a high gaseous C/O ratio. In contrast, it is the first VLMS disk in the MINDS sample to show both distinctive dust features and a rich hydrocarbon chemistry. The presence of large grains indicates dust growth and evolution. Thermo-chemical disk models that employ an extended hydrocarbon chemical network together with C/O,>1 are able to explain the hydrocarbon species detected in the spectrum.","PeriodicalId":8585,"journal":{"name":"Astronomy &amp; Astrophysics","volume":"108 46","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141821508","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Star formation in extreme environments: A 200 pc high velocity gas stream in the Galactic centre","authors":"V. S. Veena, W.-J. Kim, Á. Sánchez-Monge, P. Schilke, K. Menten, G. Fuller, M. Sormani, F. Wyrowski, W. E. Banda-Barragan, D. Riquelme, P. Tarrio, P. D. Vicente","doi":"10.1051/0004-6361/202450902","DOIUrl":"https://doi.org/10.1051/0004-6361/202450902","url":null,"abstract":"The expanding molecular ring (EMR) manifests itself as a parallelogram in the position-velocity diagram of spectral line emission from the Central Molecular Zone (CMZ) surrounding the Galactic centre (GC). It is a high velocity ($ V_ LSR extended molecular gas structure. The formation of the EMR is believed to be associated with the bar driven inflow onto the nuclear region of the Galaxy. The physical and chemical properties, as well as the evolution of the EMR and its connection to other GC clouds and the CMZ as a whole, are not yet fully comprehended. Using multiwavelength data, we investigate the gas kinematics, star formation activity, and the presence of shocked gas in a 200 pc long high velocity gas stream (V$_ LSR with a double helix morphology named the helix stream, that is located 15--55 pc above the CMZ ($l $b and is kinematically associated with the EMR/parallelogram. To study the kinematics of the helix stream, we used 13CO ($J=2-1$) data from the SEDIGISM survey and 12CO ($J=1-0$) archival data from the Nobeyama telescope. Additional multiwavelength archival data from infrared to radio wavelengths were used to investigate the star formation activity. We carried out molecular line observations using the IRAM 30m, Yebes 40m, and APEX 12m telescopes. The detection of four rotational transitions of the SiO molecule ($J=$ 1--0, 2--1, 5--4, 7--6) indicate the presence of shocks. We derived the SiO column densities and abundances in different regions of the helix stream using the rotational diagram method. We also performed non-local thermodynamic equilibrium (non-LTE) modelling of the SiO emission to analyse the excitation conditions of the shocked gas. The presence of clumps with submillimetre continuum emission from dust and \u0000 a candidate region signify the ongoing star formation activity within the helix stream. The cloud is massive ($2.5 M$_ and highly turbulent ($ V mean We find evidence of cloud-cloud collisions towards the eastern edge ($l suggesting a dynamic interaction with the CMZ. An expanding shell is detected within the cloud with radius of 6.7 pc and an expansion velocity of 35 The shell might be powered by several supernovae or a single hypernova. The relative abundance of SiO within the helix stream with respect to H$_2$ implies extensive shock processes occurring on large scales ($X$(SiO) $ $). The helical or cork-screw velocity structure observed within the individual strands of the helix stream indicates twisting and turning motions occurring within the cloud. We propose that the helix stream is the continuation of the near side bar lane, that is overshooting after ``brushing'' the CMZ and interacting with it at the location of the G1.3 cloud. This interpretation finds support both from numerical simulations and prior observational studies of the CMZ. Our findings carry profound implications for understanding star formation in extreme conditions and they elucidate the intricate properties of gas and dust associated wit","PeriodicalId":8585,"journal":{"name":"Astronomy &amp; Astrophysics","volume":"122 11","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141821951","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}