scholarly journals Massive Star Formation in W49

1987 ◽  
Vol 115 ◽  
pp. 143-145
Author(s):  
J. Dreher ◽  
S. Vogel ◽  
S. Terebey ◽  
W. J. Welch
Keyword(s):  
Star Formation ◽  
High Resolution ◽  
Massive Star ◽  
Hii Regions ◽  
Molecular Line ◽  
The Galaxy ◽  
Molecular Lines ◽  
H Ii Region ◽  
Scale Structures ◽  
The Continuum

W49 is the most luminous H II region complex in the galaxy. VLA maps in the continuum reveal a complex of more than two dozen compact HII regions, including a ring-like distribution of a dozen such regions within a volume of 1 pc. In addition to the VLA maps, we have obtained high resolution maps in this field with the Hat Creek Millimeter Interferometer in the following molecular lines: HCO+(1-0), H13CO+(1-0), SiO(v = 0, J = 2-1), SiO(v = 1, J = 2-1), H13CN(1-0), HC15N(1-0), SO2 [8(3,5)-9(2,8)], SO2[8(1,7)-8(0,8)], SO[2(2)-1(1)], and CH3CH2CN[10(1,10)-9(1,9)], all near 3 mm wavelengh. These maps will be discussed. The HCO+distribution corresponds to the larger scale structures observed in the continuum maps. In contrast the SO and SiO sources are quite compact. Using the detailed molecular line results obtained in the ORION/KL region as a guide, we are able to identify these latter sources as regions in which the star formation is at an earlier stage, regions where there are outflows.

scholarly journals 4.8. Distribution of C18O and HNCO emission in the Sagittarius B2 molecular cloud

1998 ◽  
Vol 184 ◽  
pp. 181-182 ◽  
Author(s):  
Fumio Sato ◽  
Tetsuo Hasegawa ◽  
John B. Whiteoak ◽  
Masayoshi Shimizu
Keyword(s):  
Star Formation ◽  
Molecular Cloud ◽  
Massive Star ◽  
Galactic Center ◽  
Full Description ◽  
Massive Star Formation ◽  
Hii Region ◽  
The Galaxy ◽  
Molecular Lines ◽  
Star Formation Regions

Sgr B2, located at a distance of ∼100 pc from the Galactic center, is one of the most active, recent massive-star formation regions in the Galaxy. Based on the 13CO (J = 1–0) line data taken with the Nobeyama 45 m telescope, we presented a cloud collision scenario as the triggering mechanism of the burst of massive-star formation there (Hasegawa et al. 1994). In order to obtain further evidence supporting our model, we observed the Sgr B2 molecular cloud in various molecular lines with the 45 m telescope in 1992 February. Twelve points each with 20″ spacings were observed along several strips 3.67′ long at constant galactic longitudes through the major HII region complexes. Here we report the results of the two lines in the 110 GHz band, C18O (J = 1–0) and HNCO (50,5–40,4). Full description of the observations will be given elsewhere (Sato et al. 1997).

scholarly journals HERMES – An instrument of the future

2009 ◽  
Vol 5 (S262) ◽  
pp. 448-449 ◽  
Author(s):  
Elizabeth Wylie-de Boer ◽  
Kenneth Freeman
Keyword(s):  
Star Formation ◽  
High Resolution ◽  
Resolving Power ◽  
Individual Stars ◽  
Elemental Abundances ◽  
The Future ◽  
The Galaxy ◽  
History Of ◽  
High Resolution Spectrometer ◽  
Resolution Spectrometer

AbstractHERMES is a new, multi-object high resolution spectrometer for the 3.9m Anglo Australian Telescope, using the existing 2dF positioner. The primary goal of the HERMES survey is to unravel the history of the Galaxy from detailed elemental abundances for about 1.2 million individual stars. The HERMES chemical tagging survey concentrates on the 5000 to 8000 Å window at a resolving power of 30,000 in order to identify dissolved star formation aggregates and ascertain the importance of mergers throughout the history of the Galaxy.

scholarly journals Molecular Line Observations of Infrared Dark Clouds: Seeking the Precursors to Intermediate and Massive Star Formation

2006 ◽  
Vol 166 (2) ◽  
pp. 567-584 ◽  
Author(s):  
S. E. Ragan ◽  
E. A. Bergin ◽  
R. Plume ◽  
D. L. Gibson ◽  
D. J. Wilner ◽  
...  
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
Massive Star Formation ◽  
Molecular Line ◽  
Dark Clouds ◽  
Infrared Dark Clouds

scholarly journals How to Model the Chemical Evolution of Galaxies

1993 ◽  
Vol 155 ◽  
pp. 557-566
Author(s):  
Joachim Köppen
Keyword(s):  
Star Formation ◽  
Chemical Evolution ◽  
Time Scale ◽  
Life Time ◽  
Magellanic Clouds ◽  
Formation Time ◽  
List Type ◽  
The Galaxy ◽  
H Ii Region ◽  
Magellanic Stream

For a first interpretation of the comparison of observational data, the crude “Simple Model” of chemical evolution is quite useful. Since it has well been described in the literature (e.g. Pagel and Patchett 1975, Tinsley 1980), let us here just review the assumptions and whether they are satisfied: 1.The galaxy is a closed system, with no exchange of matter with its surroundings: For the solar neighbourhood this probably is not true (the infamous Gdwarf-“problem”, Pagel 1989b). For the Magellanic Clouds this is most certainly wrong, because of the presence of the Inter-Cloud Region and the Magellanic Stream, and evidence for interaction with each other and the Galaxy as well (cf. e.g. Westerlund 1990).2.It initially consists entirely of gas (without loss of generality of primordial composition): This is good approximation also for models with gas infall, as long as the infall occurs with a time scale shorter than the star formation time scale.3.The metal production of the average stellar generation (the yield y) is constant with time: Initially, it is reasonable to make this assumption. For tables of the oxygen yield see Koppen and Arimoto (1991).4.The metal rich gas ejected by the stars is completely mixed with the ambient gas. To neglect the finite stellar life times (“instantaneous recycling approximation”) is appropriate for elements synthesized in stars whose life time is much shorter than the star formation time scale, such as oxygen, neon, sulphur, and argon.5.The gas is well mixed at all times: We don't know. The dispersion of H II region abundances may give an indication. In the Magellanic Clouds Dufour (1984) finds quite a low value (±0.08 dex for oyxgen).

scholarly journals High Resolution X-ray Observations of 3C 58

2004 ◽  
Vol 218 ◽  
pp. 185-188
Author(s):  
Patrick Slane
Keyword(s):  
High Resolution ◽  
Massive Star ◽  
Thermal Emission ◽  
Rotation Axis ◽  
Crab Nebula ◽  
X Ray ◽  
The Galaxy ◽  
Pulsar Wind ◽  
Star Surface ◽  
The Crab Nebula

As the presumed remnant of SN 1181, 3C 58 houses one of the youngest known neutron stars in the Galaxy. The properties of this young pulsar and its associated pulsar wind nebula (PWN) differ considerably from those of the Crab Nebula, and may well offer a more typical example of the endpoint of massive star collapse. High resolution X-ray studies reveal structures in the inner nebula that may be associated with the pulsar wind termination shock, a jet that may be aligned with the rotation axis, and other regions of enhanced emission. Spectral variations in the PWN are consistent with the expected evolution of the postshock flow, and complex loops of emission are seen in the nebula interior. Limits on the neutron star surface temperature fall below standard cooling models, indicating that some more rapid neutrino cooling process is required. The outer regions of 3C 58 show thermal emission with enhanced levels of neon, indicative of shocked ejecta bounding the PWN.

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 Origin of the galaxy morphology

2003 ◽  
Vol 208 ◽  
pp. 431-432
Author(s):  
N. Nakasato
Keyword(s):  
Dark Matter ◽  
Star Formation ◽  
High Resolution ◽  
Cold Dark Matter ◽  
Star Formation History ◽  
The Galaxy ◽  
Particle Hydrodynamics ◽  
History Of ◽  
Analytic Models ◽  
Galaxy Morphology

In the current most plausible Cold Dark Matter (CDM) cosmology, larger halos increase their mass by the progressive mergers of smaller clumps. Due to these progressive merger events, galaxies have formed and evolved. Such merger events could trigger star bursts depending on mass of a merging object. In other words, star formation history reflects the strength of the interaction between a galaxy and merging objects. Also, a several merger events strongly affect the development of the morphology of galaxies as assumed in semi-analytic models. In the most advanced semi-analytic models, N-body simulations of dark matter particles are used to obtain the merging history of halos. By combining the description of radiative cooling, hydrodynamics and star formation with the obtained merging history, such models successfully have explained the various qualitative predictions. Here, we show the results of similar approach but using a fullly numerical model. In contrast to the semi-analytic models, we use our high resolution Smoothed Particle Hydrodynamics (SPH) models. With our SPH code, we try to tackle the problem of the galaxy morphology. We have done a several handful high-resolution SPH simulations and analyzed the merging history of such models. Accordingly, we can see the relation between the obtained morphology and the merging history or other physical properties of the model.

scholarly journals Interactions and star formation

2015 ◽  
Vol 11 (S315) ◽  
pp. 236-239
Author(s):  
Johan H. Knapen ◽  
Mauricio Cisternas ◽  
Miguel Querejeta
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Morphological Type ◽  
Stellar Mass ◽  
Interacting Galaxies ◽  
The Galaxy ◽  
Nearby Galaxies ◽  
Ir Emission

AbstractWe investigate the influence of interactions on the star formation by studying a sample of almost 1500 of the nearest galaxies, all within a distance of ~45 Mpc. We define the massive star formation rate (SFR), as measured from far-IR emission, and the specific star formation rate (SSFR), which is the former quantity normalized by the stellar mass of the galaxy, and explore their distribution with morphological type and with stellar mass. We then calculate the relative enhancement of these quantities for each galaxy by normalizing them by the median SFR and SSFR values of individual control populations of similar non-interacting galaxies. We find that both SFR and SSFR are enhanced in interacting galaxies, and more so as the degree of interaction is higher. The increase is, however, moderate, reaching a maximum of a factor of 1.9 for the highest degree of interaction (mergers). The SFR and SSFR are enhanced statistically in the population, but in most individual interacting galaxies they are not enhanced at all. We discuss how those galaxies with the largest SFR and/or SSFR enhancement can be defined as starbursts. We argue that this study, based on a representative sample of nearby galaxies, should be used to place constraints on studies based on samples of galaxies at larger distances.

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