Galactic Clusters and HII Regions

Becker, W.; Fenkart, R.

doi:10.1007/978-94-010-3275-9_35

Cited by 93 publications

(98 citation statements)

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“…The main m = 2 pattern terminates close to 60 , outside which a weaker, tighter pattern exists. NGC 1232: it has been argued that this galaxy has a morphology similar to that of our Milky Way (Becker & Fenkart 1970 The positions of all non-stellar sources with photometric errors <0. m 3 are shown in Fig. A.3, where compact complexes (0.3 < cs < 0.95) are plotted as red points and diffuse ones (cs < 0.3) as blue triangles.…”

Section: Appendix A: Morphology Of Galaxies and Distribution Of Clustmentioning

confidence: 91%

Star formation in grand-design, spiral galaxies

Grosbøl

Dottori

2012

A&A

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Aims. Spiral structure is a prominent feature in many disk galaxies and is often outlined by bright, young objects. We study the distribution of young stellar clusters in grand-design spiral galaxies and thereby determine whether strong spiral perturbations can influence star formation. Methods. Deep, near-infrared JHK-maps were observed for ten nearby, grand-design, spiral galaxies using HAWK-I at the Very Large Telescope. Complete, magnitude-limited candidate lists of star-forming complexes were obtained by searching within the K-band maps. The properties of the complexes were derived from (H − K) -(J − H) diagrams including the identification of the youngest complexes (i.e. < ∼ 7 Myr) and the estimation of their extinction. Results. Young stellar clusters with ages < ∼ 7 Myr have significant internal extinction in the range of A V = 3-7 m , while older ones typically have A V < 1 m . The cluster luminosity function (CLF) is well-fitted by a power law with an exponent of around -2 and displays no evidence of a high luminosity cut-off. The brightest cluster complexes in the disk reach luminosities of M K = -15. m 5 or estimated masses of 10 6 M . At radii with a strong, two-armed spiral pattern, the star formation rate in the arms is higher by a factor of 2-5 than in the inter-arm regions. The CLF in the arms is also shifted towards brighter M K by at least 0. m 4. We also detect clusters with colors compatible with Large Magellanic Cloud intermediate age clusters and Milky Way globular clusters. The (J − K) -M K diagram of several galaxies shows, for the brightest clusters, a clear separation between young clusters that are highly attenuated by dust and older ones with low extinction. Conclusions. The gap in the (J − K) -M K diagrams implies that there has been a rapid expulsion of dust at an age around 7 Myr, possibly triggered by supernovae. Strong spiral perturbations concentrate the formation of clusters in the arm regions and shifts their CLF towards brighter magnitudes.

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Section: Appendix A: Morphology Of Galaxies and Distribution Of Clustmentioning

confidence: 91%

Star formation in grand-design, spiral galaxies

Grosbøl

Dottori

2012

A&A

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“…We find good agreement with the value derived by Cuffey (1973) who used UBV magnitudes to derive that the reddening in front of the cluster amounts to E(B − V) = 0.4, while the distance is 3.6 kpc. Among the first distance values published for NGC 1893, Becker & Fenkart (1971) found d = 3700 pc and A V = 1.68, corresponding to E(B − V) = 0.54, by using simultaneously two color-magnitude diagrams. Moffat (1972) derived a distance of 3980 pc and a reddening E(B − V) = 0.55 using photographic UBV photometry and the ZAMS fitting to the unreddened CMD.…”

Section: Comparison With Previously Published Cluster Parametersmentioning

confidence: 93%

Star formation in the outer Galaxy: membership and fundamental parameters of the young open cluster NGC 1893

Prisinzano

Sanz-Forcada

Micela

et al. 2011

A&A

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Context. Different environmental conditions can play a crucial role in determining final products of the star formation process and in this context, less favorable activities of star formation are expected in the external regions of our Galaxy. Aims. We studied the properties of the young open cluster NGC 1893 located about 12 Kpc from the galactic center, to investigate how different physical conditions can affect the process of star formation. Methods. By adopting a multiwavelength approach, we compiled a catalog extending from X-rays to NIR data to derive the cluster membership. In addition, optical and NIR photometric properties are used to evaluate the cluster parameters. Results. We find 415 diskless candidate members plus 1061 young stellar objects with a circumstellar disk or class II candidate members, 125 of which are also H α emitters. Considering the diskless candidate members, we find that the cluster distance is 3.6±0.2 kpc and the mean interstellar reddening is E(B-V)=0.6±0.1 with evidence of differential reddening in the whole surveyed region. Conclusions. NGC 1893 contains a conspicuous population of pre-main sequence stars together with the well studied main sequence cluster population; we found a disk fraction of about 70% similar to that found in clusters of similar age in the solar neighbour and then, despite expected unfavorable conditions for star formation, we conclude that very rich young clusters can form also in the outer regions of our Galaxy.

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“…8). Feast (1963) 0 .48 ± 0.01 11.86 ± 0.14 2360 · · · Kennedy (1966) 0.46 11.9 Becker & Fenkart (1971) 0.31 Perry et al (1976) 0 .40 ± 0.01 11.8 ± 0.2 · · · 7 Shobbrook (1984) 0 . 3 8 1 1 .4 ± 0.1 Sanner et al (2001) 0 .36 ± 0.02 11.6 ± 0.2 2100 ± 200 10 ± 5 McSwain & Gies (2005) 0.38 11.80 2290 7 This work 0.30 12.10 ± 0.39 2630 ± 475 11…”

Section: (B8 V)mentioning

confidence: 99%

Open clusters

Aidelman

Cidale

Zorec

et al. 2012

A&A

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Context. Spectroscopic investigations of galactic open clusters are scarce and limited to a reduced sample of cluster members. Aims. We intend to perform a complete study of the physical parameters of two galactic clusters as well as of their individual members. Methods. To carry out this study, we used the BCD (Barbier-Chalonge-Divan) spectrophotometric system, which is based on the study of the Balmer discontinuity and is independent of interstellar and circumstellar extinction. Additional physical properties were derived from the line profiles (FWHM) and stellar evolution models. We analyzed low-resolution spectra around the Balmer discontinuity for normal B-type and Be stars in two open clusters: NGC 3766 and NGC 4755. We determined the stellar fundamental parameters, such as effective temperatures, surface gravities, spectral types, luminosity classes, absolute and bolometric magnitudes, and color gradient excesses. The stellar rotation velocity was also determined. Complementary information, mainly stellar mass, age, and radius of the star population were calculated using stellar evolution models. In some cases, the stellar fundamental parameters were derived for the first time. The obtained results allowed us also to determine the reddening, age, and distance to the clusters. Results. The cluster parameters obtained through the BCD method agree very well with those derived from classical methods based on photometric data. The BCD system also provides physical properties of the star members. This study enables us to test the good behavior of M bol (λ 1 , D)-calibrations and detect systematic discrepancies between log g estimates from model atmospheres and those derived from stellar evolution models. To improve our knowledge on the formation and evolution of the clusters, more statistical studies on the initial mass luminosity and angular momentum distributions should be addressed. Therefore, the BCD spectrophotometric system could be a powerful tool for studying far galactic and extragalactic clusters with the generation of large telescopes and the multi-object technique.

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Galactic Clusters and HII Regions

Cited by 93 publications

References 0 publications

Star formation in grand-design, spiral galaxies

Star formation in grand-design, spiral galaxies

Star formation in the outer Galaxy: membership and fundamental parameters of the young open cluster NGC 1893

Open clusters

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