scholarly journals Supershells

1988 ◽  
Vol 101 ◽  
pp. 447-459
Author(s):  
Richard McCray
Keyword(s):  
Star Formation ◽  
Radio Emission ◽  
Interstellar Medium ◽  
Milky Way ◽  
Disk Galaxy ◽  
Interstellar Gas ◽  
Irregular Galaxies ◽  
Nearby Galaxies ◽  
Gas Layer

AbstractRepeated supernovae from an OB association will, in a few ×107 yr, create a cavity of coronal gas in the interstellar medium, with radius > 100 pc, surrounded by a dense expanding shell of cool interstellar gas. Such a cavity will likely burst through the gas layer of a disk galaxy. Such holes and “supershells” have been observed in optical and H I radio emission maps of the Milky Way and other nearby galaxies. The gas swept up in the supershell is likely to become gravitationally unstable, providing a mechanism for propagating star formation that may be particularly effective in irregular galaxies.

scholarly journals Observations of supershells in the interstellar medium of nearby galaxies

2006 ◽  
Vol 2 (S237) ◽  
pp. 76-83
Author(s):  
Elias Brinks ◽  
Ioannis Bagetakos ◽  
Fabian Walter ◽  
Erwin de Blok
Keyword(s):  
Star Formation ◽  
Interstellar Medium ◽  
Detection Threshold ◽  
Nearby Galaxy ◽  
Late Type ◽  
First Results ◽  
Nearby Galaxies ◽  
Gas Layer ◽  
Expanding Shells ◽  
Major Project

AbstractHI observations at sufficiently high spatial and velocity resolution have revealed a wealth of structures such as shells and bubbles in the ISM of late–type galaxies. These structures are filled with metal–enriched, coronal gas from SNe which, through overpressure, powers their expansion. Material swept up by these expanding shells can go “critical” and form subsequent (secondary or propagating) star formation. Shells that grow larger than the thickness of the gas layer will blow out of the disk, spilling enriched material into the halo (or in the case of violent starbursts, the Intergalactic Medium). We review what has been achieved to date and present some first results of a major project based on THINGS (The HI Nearby Galaxy Survey), which aims to extend studies of the ISM in galaxies to 34 nearby systems (<10 Mpc), all observed to the same exacting standards (resolution 6″ × 5 km s−1, or better; typical detection threshold of ~5 × 1019 atom cm−2).

Molecular Clouds

1977 ◽  
Vol 75 ◽  
pp. 37-54 ◽  
Author(s):  
P. Thaddeus
Keyword(s):  
Star Formation ◽  
Interstellar Medium ◽  
Molecular Clouds ◽  
Physical State ◽  
Molecular Gas ◽  
Spectroscopic Techniques ◽  
Low Density ◽  
Recombination Line ◽  
Interstellar Gas ◽  
Impossible Task

To attempt to understand star formation without knowing the physical state of the dense interstellar molecular gas from which stars are made is an almost impossible task. Star formation has developed late as a branch of astrophysics largely for lack of observational data, and in particular, has lagged badly behind the study of the atomic and ionized components of the interstellar gas because spectroscopic techniques which work well at low density have an unfortunate tendency to fail when the density is high. Optical spectroscopy, which has been applied to the interstellar medium for over 70 years, has made little progress in regions of high density because of obscuration, and the same is true a fortiori of spacecraft spectroscopy in the UV; radio 21-cm and recombination line observations, although unhampered by obscuration, are unsatisfactory because the dense condensations are almost entirely molecular in composition.

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 Measurements of Cosmic Magnetism with LOFAR and SKA

2007 ◽  
Vol 5 ◽  
pp. 399-405 ◽  
Author(s):  
R. Beck
Keyword(s):  
Magnetic Fields ◽  
Interstellar Medium ◽  
Milky Way ◽  
Intergalactic Medium ◽  
Low Frequency ◽  
Radio Telescopes ◽  
New Era ◽  
Origin And Evolution ◽  
Central Regions ◽  
Nearby Galaxies

Abstract. The origin of magnetic fields in stars, galaxies and clusters is an open problem in astrophysics. The next-generation radio telescopes Low Frequency Array (LOFAR) and Square Kilometre Array (SKA) will revolutionize the study of cosmic magnetism. "The origin and evolution of cosmic magnetism" is a key science project for SKA. The planned all-sky survey of Faraday rotation measures (RM) at 1.4 GHz will be used to model the structure and strength of the magnetic fields in the intergalactic medium, the interstellar medium of intervening galaxies, and in the Milky Way. A complementary survey of selected regions at around 200 MHz is planned as a key project for LOFAR. Spectro-polarimetry applied to the large number of spectral channels available for LOFAR and SKA will allow to separate RM components from distinct foreground and background regions and to perform 3-D Faraday tomography of the interstellar medium of the Milky Way and nearby galaxies. – Deep polarization mapping with LOFAR and SKA will open a new era also in the observation of synchrotron emission from magnetic fields. LOFAR's sensitivity will allow to map the structure of weak, extended magnetic fields in the halos of galaxies, in galaxy clusters, and possibly in the intergalactic medium. Polarization observations with SKA at higher frequencies (1–10 GHz) will show the detailed magnetic field structure within the disks and central regions of galaxies, with much higher angular resolution than present-day radio telescopes.

scholarly journals Molecular gas in galaxies: changing conditions from disks to starbursts

2015 ◽  
Vol 11 (S315) ◽  
pp. 199-206
Author(s):  
Christine D. Wilson
Keyword(s):  
Star Formation ◽  
Interstellar Medium ◽  
Galaxy Evolution ◽  
Surface Density ◽  
Physical State ◽  
Active Galaxies ◽  
Molecular Gas ◽  
Central Question ◽  
Space Observatory ◽  
Nearby Galaxies

AbstractIn understanding galaxy evolution, one central question is how star formation is regulated in galaxies. Changes in star formation rates are likely tied to changes in the interstellar medium, particularly the molecular gas which is the fuel for star formation. I will discuss our recent results which use data from the Herschel Space Observatory, the Atacama Large Millimeter/submillimeter Array, and other telescopes to determine the typical density, temperature, and surface density of the molecular gas in various nearby galaxies. Comparing the properties of molecular gas in starburst and other active galaxies with more quiescent spiral disks provides some clues as to how changes in the physical state of the gas, such as mean density, can lead to enhanced star formation rates.

scholarly journals The Interstellar Medium in Star Burst Galaxies

1987 ◽  
Vol 115 ◽  
pp. 614-614
Author(s):  
R. Genzel ◽  
J. B. Lugten ◽  
M. K. Crawford ◽  
D. M. Watson
Keyword(s):  
Star Formation ◽  
Interstellar Medium ◽  
Line Emission ◽  
Far Infrared ◽  
High Rate ◽  
Interstellar Gas ◽  
Infrared Observations ◽  
Bolometric Luminosity ◽  
Neutral Gas ◽  
Molecular Lines

We report far-infrared observations of [0 I], [C II] and [O III] fine structure emission lines toward the nuclei of M82 and 7 other galaxies with a high rate of star formation. The far-infrared line emission is bright, contains about 0.5% of the bolometric luminosity in the central 60″, and is spatially concentrated toward the nuclei. In these galaxies between 10 and 30% of the interstellar gas near the nuclei is contained in a warm, atomic component. This atomic gas is probably located at the UV photodissociated surfaces of molecular clouds. The neutral gas in M82 has a temperature of ∼ 200 K, hydrogen density of ∼ 3 × 104 cm−3 and is very clumpy, indicating that the interstellar medium in this star burst galaxy is very different from that in the disk of our own galaxy. We discuss the implications of the infrared observations for the interpretation of mm molecular lines and for star formation at the nuclei of star burst galaxies.

scholarly journals Live fast, die young: GMC lifetimes in the FIRE cosmological simulations of Milky Way mass galaxies

2020 ◽  
Vol 497 (3) ◽  
pp. 3993-3999 ◽  
Author(s):  
Samantha M Benincasa ◽  
Sarah R Loebman ◽  
Andrew Wetzel ◽  
Philip F Hopkins ◽  
Norman Murray ◽  
...  
Keyword(s):  
Star Formation ◽  
Molecular Clouds ◽  
Milky Way ◽  
Giant Molecular Clouds ◽  
Physical Processes ◽  
Cosmological Simulations ◽  
Initial Investigation ◽  
Nearby Galaxies

ABSTRACT We present the first measurement of the lifetimes of giant molecular clouds (GMCs) in cosmological simulations at z = 0, using the Latte suite of FIRE-2 simulations of Milky Way (MW) mass galaxies. We track GMCs with total gas mass ≳105 M⊙ at high spatial (∼1 pc), mass (7100 M⊙), and temporal (1 Myr) resolution. Our simulated GMCs are consistent with the distribution of masses for massive GMCs in the MW and nearby galaxies. We find GMC lifetimes of 5–7 Myr, or 1–2 freefall times, on average, with less than 2 per cent of clouds living longer than 20 Myr. We find decreasing GMC lifetimes with increasing virial parameter, and weakly increasing GMC lifetimes with galactocentric radius, implying that environment affects the evolutionary cycle of GMCs. However, our GMC lifetimes show no systematic dependence on GMC mass or amount of star formation. These results are broadly consistent with inferences from the literature and provide an initial investigation into ultimately understanding the physical processes that govern GMC lifetimes in a cosmological setting.

scholarly journals The interstellar medium and star formation in nearby galaxies

2014 ◽  
Vol 335 (5) ◽  
pp. 470-485 ◽  
Author(s):  
F. Bigiel ◽  
D. Cormier ◽  
T. Schmidt
Keyword(s):  
Star Formation ◽  
Interstellar Medium ◽  
Nearby Galaxies

scholarly journals Star Formation and the Interstellar Medium in Four Dwarf Irregular Galaxies

2003 ◽  
Vol 592 (1) ◽  
pp. 111-128 ◽  
Author(s):  
L. M. Young ◽  
L. van Zee ◽  
K. Y. Lo ◽  
R. C. Dohm‐Palmer ◽  
Michelle E. Beierle
Keyword(s):  
Star Formation ◽  
Interstellar Medium ◽  
Irregular Galaxies ◽  
Dwarf Irregular Galaxies
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