scholarly journals THE ADF AND THE t2 FORMALISM IN H II REGIONS BASED ON THE UPPER MASS LIMIT OF THE IMF FOR THE MW

2020 ◽  
Vol 56 (2) ◽  
pp. 235-244
Author(s):  
L. Carigi ◽  
A. Peimbert ◽  
M. Peimbert ◽  
G. Delgado-Inglada
Keyword(s):  
Milky Way ◽  
Spiral Galaxies ◽  
Star Formation Rate ◽  
Direct Method ◽  
Formation Rate ◽  
Mass Function ◽  
Initial Mass Function ◽  
H Ii Regions ◽  
Mass Limit ◽  
Better Than

We study in depth the abundance discrepancy problem in H II regions, this time from a different perspective than the usual one: by studying the effect of the upper mass limit (Mup) of the initial mass function (IMF) on the O, C, and He predicted by chemical evolution models for the Milky Way. We use abundances determined with the direct method (DM) and with the temperature independent method (TIM). We compare the predicted abundances at the present time with observations of Orion, M17, and M8 to determine the Mup value of the galactic IMF. From the DM abundances, the models predict an Mup = 25 − 45 M⨀, while from the TIM, CEMs derive an Mup = 70 − 110 M⨀. Spiral galaxies with the stellar mass and star formation rate of the MW are predicted to have an Mup ≈ 100 M⨀. These results support that abundances derived from the TIM are better than those derived from the DM.

scholarly journals Star Formation of Star Clusters in the SMC and their Adjoining Fields

1986 ◽  
Vol 116 ◽  
pp. 101-102
Author(s):  
M. Kontizas ◽  
E. Kontizas
Keyword(s):  
Star Formation ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Star Clusters ◽  
Mass Function ◽  
Spectroscopic Studies ◽  
Initial Mass Function ◽  
The West ◽  
West Side ◽  
Halo Population

Photometric and recent spectroscopic studies of the SMC have shown that the differences observed in the SMC clusters and those of our Galaxy could be attibuted to differences in metallicity, star formation rate and/or the Initial Mass Function (IMF) (Humphries, 1983). The studied clusters NGC152 and KRON3 are located at the west side of the bar of the SMC and their adjoining fields represent the halo population of this galaxy.

scholarly journals Galactic structure from infrared studies

1979 ◽  
Vol 84 ◽  
pp. 105-111 ◽  
Author(s):  
J. L. Puget ◽  
G. Serra ◽  
C. Ryter
Keyword(s):  
Galactic Center ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Far Infrared ◽  
Mass Function ◽  
Infrared Emission ◽  
Initial Mass Function ◽  
Young Stars ◽  
Infrared Studies ◽  
Red Giant

Star densities on a galactic scale are traced by far infrared emission of dust heated by young stars and by the 2.4 μm radiation of stars in the red giant phase. Coherent results are obtained, pointing to a very strong star formation rate during the last ∼200 My in a ring 5 kpc from the galactic center. A steepening of the initial mass function compared to that observed in the solar vicinity is also suggested.

scholarly journals Modes of star formation from Herschel

2012 ◽  
Vol 8 (S292) ◽  
pp. 87-90
Author(s):  
L. Testi ◽  
E. Bressert ◽  
S. Longmore
Keyword(s):  
Star Formation ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Mass Function ◽  
Initial Mass Function ◽  
Dense Gas ◽  
Nearby Star ◽  
Star Forming ◽  
Star Forming Regions ◽  
Massive Cluster

AbstractWe summarize some of the results obtained from Herschel surveys of nearby star forming regions and the Galactic plane. We show that in the nearby star forming regions the starless core spatial surface density distribution is very similar to that of the young stellar objects. This, taken together with the similarity between the core mass function and the initial mass function for stars and the relationship between the amount of dense gas and star formation rate, suggest that the cloud fragmentation process defines the global outcome of star formation. This “simple” view of star formation may not hold on all scales. In particular dynamical interactions are expected to become important at the conditions required to form young massive clusters. We describe the successes of a simple criterion to identify young massive cluster precursors in our Galaxy based on (sub-)millimeter wide area surveys. We further show that in the location of our Galaxy where the best candidate for a precursor of a young massive cluster is found, the “simple” scaling relationship between dense gas and star formation rate appear to break down. We suggest that in regions where the conditions approach those of the central molecular zone of our Galaxy it may be necessary to revise the scaling laws for star formation.

A CCD Hα Survey of Nearby Southern Spiral Galaxies

1991 ◽  
Vol 9 (1) ◽  
pp. 89-90
Author(s):  
Stuart D. Ryder ◽  
Michael A. Dopita
Keyword(s):  
Star Formation ◽  
Observational Data ◽  
Spiral Galaxies ◽  
Star Formation Rate ◽  
Formation Rate ◽  
High Mass ◽  
H Ii Regions ◽  
Mass Star ◽  
Reliable Measure ◽  
Initial Results

AbstractSome initial results of a flux-calibrated CCD Hα imaging program of bright, nearby southern spiral galaxies are presented. Very few southern hemisphere spiral galaxies have ever been completely imaged in Hα, let alone with a CCD. This survey (which mainly uses the MSSSO 1.0-m reflector with an f/3.5 focal reducer) will, when combined with spectrophotometry of the H II regions thus revealed, allow us to trace the chemical evolution of each galaxy. Furthermore, since the absolute Hα flux is a reliable measure of the high-mass star formation rate in a galaxy, such observational data will permit us to test the predictions of the various star formation theories.

scholarly journals Global survey of star clusters in the Milky Way

2018 ◽  
Vol 614 ◽  
pp. A22 ◽  
Author(s):  
A. E. Piskunov ◽  
A. Just ◽  
N. V. Kharchenko ◽  
P. Berczik ◽  
R.-D. Scholz ◽  
...  
Keyword(s):  
Milky Way ◽  
Cluster Formation ◽  
Formation Rate ◽  
Age Distribution ◽  
Star Clusters ◽  
Mass Function ◽  
Spatial Variations ◽  
Initial Mass Function ◽  
Initial Mass ◽  
Formation History

Context. The all-sky Milky Way Star Clusters (MWSC) survey provides uniform and precise ages, along with other relevant parameters, for a wide variety of clusters in the extended solar neighbourhood. Aims. In this study we aim to construct the cluster age distribution, investigate its spatial variations, and discuss constraints on cluster formation scenarios of the Galactic disk during the last 5 Gyrs. Methods. Due to the spatial extent of the MWSC, we have considered spatial variations of the age distribution along galactocentric radius RG, and along Z-axis. For the analysis of the age distribution we used 2242 clusters, which all lie within roughly 2.5 kpc of the Sun. To connect the observed age distribution to the cluster formation history we built an analytical model based on simple assumptions on the cluster initial mass function and on the cluster mass-lifetime relation, fit it to the observations, and determined the parameters of the cluster formation law. Results. Comparison with the literature shows that earlier results strongly underestimated the number of evolved clusters with ages t ≳ 100 Myr. Recent studies based on all-sky catalogues agree better with our data, but still lack the oldest clusters with ages t ≳ 1 Gyr. We do not observe a strong variation in the age distribution along RG, though we find an enhanced fraction of older clusters (t > 1 Gyr) in the inner disk. In contrast, the distribution strongly varies along Z. The high altitude distribution practically does not contain clusters with t < 1 Gyr. With simple assumptions on the cluster formation history, the cluster initial mass function and the cluster lifetime we can reproduce the observations. The cluster formation rate and the cluster lifetime are strongly degenerate, which does not allow us to disentangle different formation scenarios. In all cases the cluster formation rate is strongly declining with time, and the cluster initial mass function is very shallow at the high mass end.

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