scholarly journals Star Formation in Disk Galaxies

1998 ◽  
Vol 15 (1) ◽  
pp. 118-122 ◽  
Author(s):  
Rosemary F. G. Wyse ◽  
Annette M. N. Ferguson ◽  
Jay S. Gallagher ◽  
Deidre A. Hunter
Keyword(s):  
Star Formation ◽  
Interstellar Medium ◽  
Massive Stars ◽  
Broad Band ◽  
Hii Regions ◽  
Disk Galaxies ◽  
Chemical Enrichment

AbstractWe present results, some preliminary, from a major new study of the star formation properties of a sample of nearby disk galaxies (Ferguson 1997). Our emphasis is on the faint outer regions of disks. Hα images, combined with broad-band images and spectroscopy of HII regions, constrain the present and past star formation rates and chemical enrichment. These data also allow study of faint diffuse ionised gas, which traces the influence of massive stars on their environment, and the structure of the interstellar medium.

scholarly journals HII regions and star formation in the Magellanic Clouds

1991 ◽  
Vol 148 ◽  
pp. 139-144 ◽  
Author(s):  
Robert C. Kennicutt
Keyword(s):  
Star Formation ◽  
Interstellar Medium ◽  
Massive Star ◽  
Massive Stars ◽  
Hii Regions ◽  
Magellanic Clouds ◽  
H Ii Regions ◽  
Distant Galaxies ◽  
Close Range ◽  
Mass Functions

The H II regions in the Magellanic Clouds provide an opportunity to characterize the global star formation properties of a galaxy at close range. They also provide a unique laboratory for testing empirical tracers of the massive star formation rates and initial mass functions in more distant galaxies, and for studying the dynamical interactions between massive stars and the interstellar medium. This paper discusses several current studies in these areas.

scholarly journals Density Bounding of Giant HII Regions and the Ionisation of the Diffuse Interstellar Medium

1998 ◽  
Vol 15 (1) ◽  
pp. 83-85 ◽  
Author(s):  
J. E. Beckman ◽  
M. Rozas ◽  
J. H. Knapen
Keyword(s):  
Star Formation ◽  
Interstellar Medium ◽  
Intergalactic Medium ◽  
Hii Regions ◽  
Critical Value ◽  
Disk Galaxies ◽  
Lyman Continuum ◽  
Different Types

AbstractThree different types of evidence are presented in favour of the hypothesis that the HII regions in disk galaxies with Hα luminosities greater than a critical value of 1038·6 erg s−1 are density-bounded, and that the escaping Lyman continuum photons from these are the principal ionising agents for the diffuse ISM in disk galaxies. This has important implications for the ionisation of the intergalactic medium, and for computed star formation rates in spirals.

scholarly journals Surround and Squash: the impact of superbubbles on the interstellar medium in Scorpius–Centaurus OB2

2018 ◽  
Vol 619 ◽  
pp. A120 ◽  
Author(s):  
Martin G. H. Krause ◽  
Andreas Burkert ◽  
Roland Diehl ◽  
Katharina Fierlinger ◽  
Benjamin Gaczkowski ◽  
...  
Keyword(s):  
Star Formation ◽  
Interstellar Medium ◽  
Massive Star ◽  
Massive Stars ◽  
Three Dimensional ◽  
X Rays ◽  
Hot Gas ◽  
Sky Survey ◽  
Hydrodynamical Simulations ◽  
The Impact

Context. Feedback by massive stars shapes the interstellar medium and is thought to influence subsequent star formation. The details of this process are under debate. Aims. We exploited observational constraints on stars, gas, and nucleosynthesis ashes for the closest region with recent massive-star formation, Scorpius–Centaurus OB2, and combined them with three-dimensional (3D) hydrodynamical simulations in order to address the physics and history of the Scorpius–Centaurus superbubble. Methods. We used published cold gas observations of continuum and molecular lines from Planck, Herschel, and APEX. We analysed the Galactic All Sky Survey (GASS) to investigate shell structures in atomic hydrogen, and used Hipparcos and Gaia data in combination with interstellar absorption against stars to obtain new constraints for the distance to the Hi features. Hot gas is traced in soft X-rays via the ROSAT all sky survey. Nucleosynthesis ejecta from massive stars were traced with new INTEGRAL spectrometer observations via 26Al radioactivity. We also performed 3D hydrodynamical simulations for the Sco–Cen superbubble. Results. Soft X-rays and a now more significant detection of 26Al confirm recent (≈1 Myr ago) input of mass, energy, and nucleosynthesis ejecta, likely from a supernova in the Upper Scorpius (USco) subgroup. We confirm a large supershell around the entire OB association and perform a 3D hydrodynamics simulation with a conservative massive star population that reproduces the morphology of the superbubble. High-resolution GASS observations reveal a nested, filamentary supershell. The filaments are possibly related to the Vishniac clumping instability, but molecular gas (Lupus I) is only present where the shell coincides with the connecting line between the subgroups of the OB association, suggesting a connection to the cloud, probably an elongated sheet, out of which the OB association formed. Stars have formed sequentially in the subgroups of the OB association and currently form in Lupus I. To investigate the impact of massive star feedback on extended clouds, we simulate the interaction of a turbulent cloud with the hot, pressurised gas in a superbubble. The hot gas fills the tenuous regions of the cloud and compresses the denser parts. Stars formed in these dense clumps would have distinct spatial and kinematic distributions. Conclusions. The combined results from observations and simulations are consistent with a scenario where dense gas was initially distributed in a band elongated in the direction now occupied by the OB association. Superbubbles powered by massive stars would then repeatedly break out of the elongated parent cloud, and surround and squash the denser parts of the gas sheet and thus induce more star formation. The expected spatial and kinematic distribution of stars is consistent with observations of Sco–Cen. The scenario might apply to many similar regions in the Galaxy and also to active galactic nucleus (AGN)-related superbubbles.

scholarly journals Star Formation in Young Cluster NGC 1893

2007 ◽  
Vol 3 (S246) ◽  
pp. 73-74
Author(s):  
Saurabh Sharma ◽  
A. K. Pandey ◽  
D. K. Ojha ◽  
W. P. Chen ◽  
S. K. Ghosh ◽  
...  
Keyword(s):  
Star Formation ◽  
Narrow Band ◽  
Massive Stars ◽  
Broad Band ◽  
Archival Data ◽  
Mass Star ◽  
Star Forming ◽  
Multi Wavelength ◽  
Low Mass

AbstractWe have carried out a multi-wavelength study of the star forming region NGC 1893 to make a comprehensive exploration of the effects of massive stars on low mass star formation. Using deep optical U BV RI broad band, Hα narrow band photometry and slit-less spectroscopy along with archival data from the surveys such as 2MASS, MSX, IRAS and NVSS, we have studied the region to understand the star formation scenario in the region.

scholarly journals Massive Star Formation in the Sparsest Environments

2015 ◽  
Vol 11 (S315) ◽  
Author(s):  
Sally Oey ◽  
Joel B. Lamb
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
Massive Stars ◽  
Hii Regions ◽  
Magellanic Cloud ◽  
Small Magellanic Cloud ◽  
Massive Star Formation ◽  
Ob Stars ◽  
Runaway Stars

AbstractThere is growing evidence that massive stars sometimes form in extremely sparse environments. The RIOTS4 survey presents a variety of evidence supporting this scenario, including a sample of 14 OB stars in the Small Magellanic Cloud (SMC) that appear to have formed in situ as field stars. This is based on the presence of dense, symmetric HII regions hosting apparent non-runaway stars. We also present a spatially complete IMF of SMC field OB stars for masses > 7 M⊙, showing that the slope is much steeper than the Salpeter value. The binary fraction among field OB stars is also the same as in clusters, based on a RIOTS4 subsample. These results suggest a relative, but incomplete, suppression of massive star formation in the sparsest regimes.

The role of automated methods for filament finding in understanding the complex relationship between filaments, magnetic fields and star formation

2018 ◽  
Vol 14 (S345) ◽  
pp. 23-26
Author(s):  
Maria R. Cunningham ◽  
Claire-Elise Green ◽  
Paul A. Jones ◽  
Giles Novak ◽  
Laura Fissel
Keyword(s):  
Magnetic Field ◽  
Star Formation ◽  
Interstellar Medium ◽  
Massive Stars ◽  
Field Measurements ◽  
Complex Relationship ◽  
Dense Cores ◽  
Magnetic Field Measurements ◽  
Automated Methods

AbstractThe discovery of the ubiquity of filaments in the interstellar medium in the last two decades has begged the question: “What role do filaments play in star formation?” Here we describe how our automated filament finding algorithms can combine with both magnetic field measurements and high-resolution observations of dense cores in these filaments, to provide a statistically large sample to investigate the effect of filaments on star formation. We find that filaments are likely actively accreting mass from the interstellar medium, explaining why some 60% of stars, and all massive stars, form “on-filament”.

scholarly journals Star Formation in M81

1987 ◽  
Vol 115 ◽  
pp. 626-626
Author(s):  
Frank Bash ◽  
Michele Kaufman
Keyword(s):  
Shock Wave ◽  
Star Formation ◽  
Interstellar Medium ◽  
Thermal Radiation ◽  
Spiral Galaxy ◽  
Density Wave ◽  
Wave Theory ◽  
Hii Regions ◽  
Radio Continuum ◽  
Density Wave Theory

VLA observations of the spiral galaxy M81 in the radio continuum at wavelengths of 6 and 20-cm have been used to check the predictions of the density wave theory. The non-thermal radiation from the arms has been detected and the arms are found to be broader than the predictions of the classical density wave theory. Their width does seem to agree with that predicted by models which take the clumpy nature of the interstellar medium into account. These data are also able to separate giant HII regions from the non-thermal arms. Collaborators have furnished optical Hα data on the HII regions and HI 21-cm data, from the VLA, which will be used to find and measure the location of the HII regions with respect to the spiral shock wave and to measure the visual extinction in the disk of M81.

Chemical enrichment of Pop III supernovae in the first galaxies

2019 ◽  
Vol 15 (S341) ◽  
pp. 257-260
Author(s):  
Ke-Jung Chen
Keyword(s):  
Star Formation ◽  
Massive Stars ◽  
Radiative Feedback ◽  
Chemical Enrichment ◽  
Modern Cosmology ◽  
First Galaxies ◽  
Inside Out

AbstractUnderstanding the formation of the first galaxies (FGs) is one of the most important topics in modern cosmology. In this proceeding, we briefly summarize the results of chemical enrichment from the Pop III supernovae during the assembly of the FGs. This early chemical enrichment plays an important role in triggering the Pop II star formation. Generally speaking, there are two major enrichment channels, inside-out (internal) and outside-in (external). Our results suggest that the external channel of chemical enrichment only works if the Pop III stars are very massive stars of 200–260 M⊙, which produce strong enough radiative feedback and supernova to derive the external metal mixing down to the center of the nearby halo.

Fueling Nuclear Starbursts

1999 ◽  
Vol 186 ◽  
pp. 213-216
Author(s):  
Jeroen P.E. Gerritsen ◽  
Vincent Icke
Keyword(s):  
Numerical Simulation ◽  
Star Formation ◽  
Interstellar Medium ◽  
Negative Feedback ◽  
Equal Mass ◽  
Young Stars ◽  
Disk Galaxies ◽  
Accurate Treatment

We present a numerical simulation of two merging equal-mass, gas-rich disk galaxies. Special emphasis is given to an accurate treatment of the interstellar medium physics and star formation with its feedback. We will explain how the negative feedback from young stars restricts the bulk of the star formation during the merger-induced starburst to the nucleus.

scholarly journals Non-stellar sources of turbulence in the interstellar medium

2006 ◽  
Vol 2 (S237) ◽  
pp. 70-75
Author(s):  
Eve C. Ostriker
Keyword(s):  
Star Formation ◽  
Large Scale ◽  
Milky Way ◽  
Hii Regions ◽  
Disk Galaxies ◽  
Magnetorotational Instability ◽  
Energy Inputs ◽  
Stellar Energy ◽  
Alternative Sources ◽  
Stellar Sources

AbstractTurbulence is believed to be important to star formation both within GMCs (affecting the IMF and the SFE), and on larger scales in the ISM (affecting GMC formation rates and properties). The traditional view of the ISM attributes most of the turbulent driving to stellar sources – in particular, supernovae and HII regions. However, evidence suggests that sources other than star formation must contribute significantly to large-scale turbulent driving in the diffuse ISM, thus also affecting the turbulence that GMCs inherit. I review recent investigations of alternative sources proposed for driving ISM turbulence, including thermal instabilities, the magnetorotational instability, large-scale self-gravitating modes, and instabilities in spiral shocks. I summarize results based on numerical simulations regarding the levels of turbulence that can be driven, and how these amplitudes depend on galactic conditions. This recent work shows that, under certain circumstances, very large-amplitude (trans-sonic with respect to the warm gas) motions and magnetic fields can be driven even without stellar energy inputs. Since turbulence can either trigger or limit star formation, understanding these potentially large non-stellar driving sources is crucial for a developing a theory of star formation regulation in the Milky Way and other disk galaxies.

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