scholarly journals How Does Star Formation Affect the Large Scale Structure of the ISM?

1996 ◽  
Vol 169 ◽  
pp. 583-590 ◽  
Author(s):  
Jan Palouš
Keyword(s):  
Star Formation ◽  
Large Scale ◽  
Milky Way ◽  
Spiral Galaxies ◽  
High Mass ◽  
Stellar Winds ◽  
Giant Molecular Clouds ◽  
Star Forming ◽  
Supernova Explosions ◽  
Destructive Processes

Nearly all the star formation in the Milky Way and nearby spiral galaxies occurs in the giant molecular clouds (GMC). Inside the GMC's the units of star formation are the high density (≥ 103cm–3) and high mass (≥ 103M⊙) clumps (Blitz, 1991). Once a GMC is “infected” by star formation many clumps form stars producing a star forming region. The formation of massive stars induces destructive processes, such as H2 dissociation, HI ionization, stellar winds and supernova explosions, thus self-limiting the lifetime of GMC to ∼ 3 107 years.

scholarly journals GASTON: Galactic Star Formation with NIKA2. Evidence for the mass growth of star-forming clumps

2021 ◽  
Author(s):  
A J Rigby ◽  
N Peretto ◽  
R Adam ◽  
P Ade ◽  
M Anderson ◽  
...  
Keyword(s):  
Star Formation ◽  
Large Scale ◽  
Galactic Plane ◽  
High Sensitivity ◽  
High Mass ◽  
Evolutionary Stage ◽  
Mass Star ◽  
Mass Growth ◽  
Star Forming ◽  
Compact Source

Abstract Determining the mechanism by which high-mass stars are formed is essential for our understanding of the energy budget and chemical evolution of galaxies. By using the New IRAM KIDs Array 2 (NIKA2) camera on the Institut de Radio Astronomie Millimétrique (IRAM) 30-m telescope, we have conducted high-sensitivity and large-scale mapping of a fraction of the Galactic plane in order to search for signatures of the transition between the high- and low-mass star-forming modes. Here, we present the first results from the Galactic Star Formation with NIKA2 (GASTON) project, a Large Programme at the IRAM 30-m telescope which is mapping ≈2 deg2 of the inner Galactic plane (GP), centred on ℓ = 23${_{.}^{\circ}}$9, b = 0${_{.}^{\circ}}$05, as well as targets in Taurus and Ophiuchus in 1.15 and 2.00 mm continuum wavebands. In this paper we present the first of the GASTON GP data taken, and present initial science results. We conduct an extraction of structures from the 1.15 mm maps using a dendrogram analysis and, by comparison to the compact source catalogues from Herschel survey data, we identify a population of 321 previously-undetected clumps. Approximately 80 per cent of these new clumps are 70 μm-quiet, and may be considered as starless candidates. We find that this new population of clumps are less massive and cooler, on average, than clumps that have already been identified. Further, by classifying the full sample of clumps based upon their infrared-bright fraction – an indicator of evolutionary stage – we find evidence for clump mass growth, supporting models of clump-fed high-mass star formation.

scholarly journals Ammonia towards dust clumps in the giant molecular cloud associated with RCW 106

2012 ◽  
Vol 8 (S292) ◽  
pp. 50-50
Author(s):  
Vicki Lowe ◽  
Maria R. Cunningham ◽  
James S. Urquhart ◽  
Shinji Horiuchi
Keyword(s):  
Star Formation ◽  
Radio Telescope ◽  
Molecular Cloud ◽  
Galactic Plane ◽  
High Mass ◽  
Mass Star ◽  
Giant Molecular Clouds ◽  
Molecular Line ◽  
Star Forming ◽  
Star Formation Regions

AbstractHigh-mass stars are known to be born within giant molecular clouds (GMCs); However, the exact processes involved in forming a high-mass star are still not well understood. It is clear that high-mass stars do not form in isolation, and that the processes surrounding high-mass star formation may affect the environment of the entire molecular cloud. We are studying the GMC associated with RCW 106 (G333), which is one of the most active massive-star formation regions in the Galactic plane. This GMC, located at l = 333° b = − 0.5°, has been mapped in over 20 molecular line transitions with the Mopra radio telescope (83-110 GHz), in Australia, and with the Swedish-ESO Submillimeter Telescope (SEST) in the 1.2 mm cool dust continuum. The region is also within the Spitzer GLIMPSE infrared survey (3.6, 4.5, 5.8, and 8.0 μm) area. We have decomposed the dust continuum using a clump-finding algorithm (CLUMPFIND), and are using the multiple molecular line traditions from the Mopra radio telescope to classify the type and stage of star formation taking place therein. Having accurate physical temperatures of the star forming clumps is essential to constrain other parameters to within useful limits. To achieve this, we have obtained pointed NH3 observations from the Tidbinbilla 70-m radio telescope, in Australia, towards these clumps.

scholarly journals High-Mass Star and Massive Cluster Formation in the Milky Way

2018 ◽  
Vol 56 (1) ◽  
pp. 41-82 ◽  
Author(s):  
Frédérique Motte ◽  
Sylvain Bontemps ◽  
Fabien Louvet
Keyword(s):  
Star Formation ◽  
Milky Way ◽  
Galactic Plane ◽  
Cluster Formation ◽  
Theoretical Models ◽  
High Mass ◽  
High Angular Resolution ◽  
Mass Star ◽  
Star Forming ◽  
Massive Cluster

This review examines the state-of-the-art knowledge of high-mass star and massive cluster formation, gained from ambitious observational surveys, which acknowledges the multiscale characteristics of these processes. After a brief overview of theoretical models and main open issues, we present observational searches for the evolutionary phases of high-mass star formation, first among high-luminosity sources and more recently among young massive protostars and the elusive high-mass prestellar cores. We then introduce the most likely evolutionary scenario for high-mass star formation, which emphasizes the link of high-mass star formation to massive cloud and cluster formation. Finally, we introduce the first attempts to search for variations of the star-formation activity and cluster formation in molecular cloud complexes in the most extreme star-forming sites and across the Milky Way. The combination of Galactic plane surveys and high–angular resolution images with submillimeter facilities such as Atacama Large Millimeter Array (ALMA) are prerequisites to make significant progress in the forthcoming decade.

scholarly journals Magnetic fields in our Milky Way Galaxy and nearby galaxies

2012 ◽  
Vol 8 (S294) ◽  
pp. 213-224 ◽  
Author(s):  
JinLin Han
Keyword(s):  
Star Formation ◽  
Magnetic Fields ◽  
Large Scale ◽  
Milky Way ◽  
Spiral Galaxies ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Measure Data ◽  
Submillimeter Wavelength ◽  
Nearby Galaxies

AbstractMagnetic fields in our Galaxy and nearby galaxies have been revealed by starlight polarization, polarized emission from dust grains and clouds at millimeter and submillimeter wavelength, the Zeeman effect of spectral lines or maser lines from clouds or clumps, diffuse radio synchrotron emission from relativistic electrons in interstellar magnetic fields, and the Faraday rotation of background radio sources as well as pulsars for our Milky Way. It is easy to get a global structure for magnetic fields in nearby galaxies, while we have observed many details of magnetic fields in our Milky Way, especially by using pulsar rotation measure data. In general, magnetic fields in spiral galaxies probably have a large-scale structure. The fields follow the spiral arms with or without the field direction reversals. In the halo of spiral galaxies magnetic fields exist and probably also have a large-scale structure as toroidal and poloidal fields, but seem to be slightly weaker than those in the disk. In the central region of some galaxies, poloidal fields have been detected as vertical components. Magnetic field directions in galaxies seem to have been preserved during cloud formation and star formation, from large-scale diffuse interstellar medium to molecular clouds and then to the cloud cores in star formation regions or clumps for the maser spots. Magnetic fields in galaxies are passive to dynamics.

scholarly journals Cosmological simulations of the same spiral galaxy: the impact of baryonic physics

2020 ◽  
Vol 501 (1) ◽  
pp. 62-77
Author(s):  
A Nuñez-Castiñeyra ◽  
E Nezri ◽  
J Devriendt ◽  
R Teyssier
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Galaxy Formation ◽  
Spiral Galaxy ◽  
Milky Way ◽  
Spiral Galaxies ◽  
Cosmological Simulations ◽  
Star Forming ◽  
Small Scales ◽  
The Impact

ABSTRACT The interplay of star formation (SF) and supernova (SN) feedback in galaxy formation is a key element for understanding galaxy evolution. Since these processes occur at small scales, it is necessary to have sub-grid models that recover their evolution and environmental effects at the scales reached by cosmological simulations. In this work, we present the results of the Mochima simulation, where we simulate the same spiral galaxy inhabiting a Milky Way (MW) size halo in a cosmological environment changing the sub-grid models for SN feedback and SF. We test combinations of the Schmidt law and a multifreefall based SF with delayed cooling feedback or mechanical feedback. We reach a resolution of 35 pc in a zoom-in box of 36 Mpc. For this, we use the code $\rm{\small RAMSES}$ with the implementation of gas turbulence in time and trace the local hydrodynamical features of the star-forming gas. Finally, we compare the galaxies at redshift 0 with global and interstellar medium observations in the MW and local spiral galaxies. The simulations show successful comparisons with observations. Nevertheless, diverse galactic morphologies are obtained from different numerical implementations. We highlight the importance of detailed modelling of the SF and feedback processes, especially for simulations with a resolution that start to reach scales relevant for molecular cloud physics. Future improvements could alleviate the degeneracies exhibited in our simulated galaxies under different sub-grid models.

scholarly journals Turbulence, feedback, and slow star formation

2006 ◽  
Vol 2 (S237) ◽  
pp. 378-383
Author(s):  
Mark R. Krumholz
Keyword(s):  
Star Formation ◽  
Milky Way ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Free Fall ◽  
Giant Molecular Clouds ◽  
Star Forming ◽  
Striking Result ◽  
Wide Range ◽  
Individual Cluster

AbstractOne of the outstanding puzzles about star formation is why it proceeds so slowly. Giant molecular clouds convert only a few percent of their gas into stars per free-fall time, and recent observations show that this low star formation rate is essentially constant over a range of scales from individual cluster-forming molecular clumps in the Milky Way to entire starburst galaxies. This striking result is perhaps the most basic fact that any theory of star formation must explain. I argue that a model in which star formation occurs in virialized structures at a rate regulated by supersonic turbulence can explain this observation. The turbulence in turn is driven by star formation feedback, which injects energy to offset radiation from isothermal shocks and keeps star-forming structures from wandering too far from virial balance. This model is able to reproduce observational results covering a wide range of scales, from the formation times of young clusters to the extragalactic IR-HCN correlation, and makes additional quantitative predictions that will be testable in the next few years.

scholarly journals Molecular Gas Kinematics and High-Mass Star Formation in the Spiral Arms of the Milky Way

2004 ◽  
Vol 191 ◽  
pp. 143-144
Author(s):  
A. Luna ◽  
L. Carrasco ◽  
L. Ortega ◽  
L. Bronfman ◽  
O. Yam
Keyword(s):  
Star Formation ◽  
Rigid Body ◽  
Large Scale ◽  
Milky Way ◽  
Stellar System ◽  
High Mass ◽  
Rotational Line ◽  
Molecular Gas ◽  
Mass Star ◽  
Spiral Arms

AbstractWe study the kinematic of the molecular gas using observations of the rotational line 12CO(J=1→0), and also the star formation traced by Ultra-Compact HII regions in the IV galactic quadrant (270° ≤ l ≤ 360°). Our results show that there is a connection between 1) high-mass star formation in the spiral arms of the Milky Way, 2) molecular gas of high column density, and 3) the large-scale rigid-body-like motion of the gas. The large-scale rigid-body-like motions observed in the arms imply that there is less angular momentum to dissipate in the formation processes of stellar systems. We show a multiple stellar system under study, embedded in its parent molecular cloud in the Carina arm region.

Implications for star formation in spiral galaxies from observations of nearby molecular cloud complexes

1979 ◽  
Vol 84 ◽  
pp. 284-284
Author(s):  
Bruce G. Elmegreen
Keyword(s):  
Star Formation ◽  
Molecular Cloud ◽  
Large Scale ◽  
Spiral Galaxies ◽  
Density Wave ◽  
Transverse Dimension ◽  
Solar Neighborhood ◽  
Thermal Pressure ◽  
Star Forming ◽  
The Galaxy

I want to make three points about star formation in spiral galaxies that follow from consideration of the internal structure of giant molecular cloud complexes (GMCC). The first point comes from pressure considerations. The total pressure inside the star-forming core of a GMCC may be written 106k)v/3kms−1)4(17pc/D)2 for virial theorem line width v and cloud diameter D; the pressure from a spiral density wave shock (SDWS) is 105 k(ns/1cm−3)(vs/20kms−1)2 and the thermal pressure in the cloud is 104 k(n/103cm−3) (T/10K) for Boltzmann constant k. These three pressures differ by factors of 10. An SDWS has too low a pressure to affect a cloud core; the only way an SDWS could influence a GMCC is if it interacted with the low thermal pressure in the cloud, i.e., the SDWS could propagate into a cloud along the direction of a magnetic field which may be the source of large scale pressure in a transverse dimension. The second point is that the density and mass of a GMCC are so large that the cloud will enter an SDWS like a cannon ball and will not be readily deflected. GMCC in other galaxies would then look like spurs on the spiral pattern and not like dust lanes. The alternative to these two points is that an as yet undiscovered (or uncommon) population of low density (100cm−3) clouds exists involving GMCC-type masses, or that smaller clouds coalesce at the SDWS. This implies that the star-forming clouds studied by molecular observers would be post-SDWS and post-gravitational collapse objects. Finally, the maximum age of a GMCC in the solar neighborhood is probably less than 50 million years. Its destruction is a result of pressure forces from the stars which it creates. Destruction in this sense does not necessarily imply that the molecules are converted into atoms – only that the cloud is pushed around. In the solar neighborhood, some clouds may, in fact, turn into 21-cm features; e.g., an HI half shell with a radius of 100 pc and a visual extinction through the shell of 0.2 mag. contains 3×105 M⊙, the mass of a GMCC. However, in the 5-kpc ring of the Galaxy, there is too much H2 relative to HI to allow any cycling between H2 and HI that is in phase with an SDWS unless the cloud remains molecular for 80% of the cycle. More likely, the cloud will be “destroyed” before that time. The implication is that cloud destruction at 5 kpc must produce molecular shells in addition to some atomic shells. This could be observed.

scholarly journals Different Evolutionary Stages in the Massive Star-forming Complex W3 Main

2012 ◽  
Vol 8 (S292) ◽  
pp. 116-116
Author(s):  
Yuan Wang ◽  
Henrik Beuther ◽  
Qizhou Zhang ◽  
Arjan Bik ◽  
Javier A. Rodón ◽  
...  
Keyword(s):  
Star Formation ◽  
Large Scale ◽  
Massive Star ◽  
Chemical Properties ◽  
Hii Regions ◽  
High Mass ◽  
Mass Star ◽  
Star Forming ◽  
Star Forming Regions ◽  
And Chemical Properties

AbstractWe observed with the Submillimeter Array and IRAM 30 m telescope three high-mass star-forming regions in different evolutionary stages in the W3 high-mass star formation complex. These regions, i.e. W3 SMS1 (W3 IRS5), SMS2 (W3 IRS4) and SMS3, are located within the same large-scale environment, which allows us to study rotation and outflows as well as chemical properties in an evolutionary sense. While we find multiple mm continuum sources toward all regions, these three subregions exhibit different dynamical and chemical properties, which indicates that they are in different evolutionary stages. Even within each sub-region, massive cores of different ages are found, e.g. in SMS2, sub-sources from the most evolved UCHii region to potential starless cores exist within 30 000 AU (left panel, Fig. 1). Outflows and rotational structures are found in SMS1 and SMS2. Evidence for interactions between the molecular cloud and the HII regions is found in the 13CO channel maps (right panel, Fig. 1), which may indicate triggered star formation.

scholarly journals GS242-03+37: a lucky survivor in the galactic gravitational field

2018 ◽  
Vol 619 ◽  
pp. A101 ◽  
Author(s):  
S. Ehlerová ◽  
J. Palouš
Keyword(s):  
Star Formation ◽  
Milky Way ◽  
Star Clusters ◽  
Young Star ◽  
Stellar Winds ◽  
Supernova Explosions ◽  
High Velocity Clouds ◽  
Shell Approximation ◽  
Hi Shells ◽  
Young Star Clusters

Context. HI shells and supershells, found in discs of many galaxies including our own, are formed by the activity of young and massive stars (supernova explosions and stellar winds), but the formation of these structures may be linked to other energetic events, such as interactions of high-velocity clouds with the galactic disc. The larger structures in particular significantly influence their surroundings; their walls are often places where molecular clouds reside and where star formation happens. Aims. We explore the HI supershell GS242-03+37, a large structure in the outer Milky Way. Its size and position make it a good case for studying the effects of large shells on their surrounding. Methods. We perform numerical simulations of the structure with the simplified hydrodynamical code RING, which uses the thin-shell approximation. The best fit is found by a comparison with the HI data and then we compare our model with the distribution of star clusters near this supershell. Results. The best model of GS242-03+37 requires, contrary to previous estimates, a relatively low amount of energy, and it has an old age of ∼100 Myr. We also find that the distribution of young star clusters (with ages <120 Myr) is correlated with walls of the supershell, while the distribution of older clusters is not. Clusters that have the highest probability of being born in the wall of the supershell show an age sequence along the wall. Conclusions. GS242-03+37 is a relatively old structure, shaped by the differential rotation, and its wall is a birthplace of several star clusters. The star formation started at a time when the supershell was not already supersonically expanding; it was a result of the density increase due to the galactic shear and oscillations perpendicular to the disc of the Milky Way.

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