Globular Clusters in the Vilnius Photometric System

1988 ◽  
pp. 515-516
Author(s):  
K. Zdanavičius
Keyword(s):  
Globular Clusters ◽  
Photometric System

Setting Up of the Strömvil System Standards and Standard Regions

2003 ◽  
Vol 12 (4) ◽  
Author(s):  
A. G. Davis Philip ◽  
R. P. Boyle ◽  
V. Straižys ◽  
A. Kazlauskas
Keyword(s):  
Globular Clusters ◽  
Advanced Technology ◽  
Photometric System ◽  
Ccd Photometry ◽  
Primary Standards

AbstractCCD photometry of standard areas of the seven-color Strömvil photometric system in some open and globular clusters is described. The primary standards are being measured with a two-channel photoelectric photometer on the 1.5 meter telescope on Mt. Lemmon. CCD photometry of standard areas is in progress with the Vatican Advanced Technology Telescope on Mt. Graham and with the CASLEO 2.1 m telescope in Argentina. Two additional Strömvil projects are described.

scholarly journals Globular Clusters in the Vilnius Photometric System

1988 ◽  
Vol 126 ◽  
pp. 515-516
Author(s):  
K. Zdanavičius
Keyword(s):  
Globular Clusters ◽  
Photometric System ◽  
Two Dimensional ◽  
Halo Stars ◽  
Dimensional Classification

The Vilnius photometric system was developed for photometric two-dimensional classification of stars and for the determination of interstellar reddening. The system consists of seven magnitudes U, P, X, Y, Z, V and S with mean wavelengths of 345, 375, 405, 466, 516, 544 and 655 nm and half-widths of the order 20 – 30 nm (Straižys 1977). Later on the system was successfully used for the determination of temperatures and the metallicities of halo stars (Bartkevičius and Sperauskas 1983).

scholarly journals Precision CCD Photometry of the Horizontal Branch

1995 ◽  
Vol 167 ◽  
pp. 361-362
Author(s):  
A. G. Davis Philip
Keyword(s):  
Globular Clusters ◽  
Photometric System ◽  
Horizontal Branch ◽  
Ccd Photometry ◽  
Horizontal Branch Stars ◽  
Color System

The Strömgren four-color system is well suited to the measure and analysis of horizontal-branch stars. The increased accuracy of the CCD photometric system and the ability to measure fainter stars in very crowded regions make the combination of the CCD system and four-color photometry an excellent one to study horizontal-branch stars in globular clusters.

scholarly journals The Integrated Photometry of Globular Clusters in the Vilnius Photometric System

1980 ◽  
Vol 85 ◽  
pp. 483-484
Author(s):  
K. Zdanavičius ◽  
V. Straižys
Keyword(s):  
Globular Clusters ◽  
Color Index ◽  
Photometric System ◽  
Intrinsic Values ◽  
Average Color ◽  
Color Excess ◽  
Free Parameters ◽  
Range Of Variation

Thirty-three globular clusters of our Galaxy were observed with the filters of the Vilnius photometric system UPXYZVS with 3450, 3740, 4050, 4660, 5160, 5440, 6550 å filters (Straižys 1977). For the classification of clusters in metallicities the reddening-free parameters QUYV QPYV and QXYV can be used. In Figure 1 these Q parameters, having a range of variation of the order of 0.4, are plotted against metallicity values from Kukarkin (1974). The parameter QPYZ has an even larger range of variation (of the order of 0.6). For determination of color excesses of clusters every color index can be used if its intrinsic values for a given metallicity defined by quantities Q are known (Figure 2). Average color excesses determined from the diagrams QUYV, (Y-V)o; QPYV, (Y-V)o and QXYV (Y-V)o and transformed to EB-V in Figure 3 are compared with color excesses from Kukarkin (1974). To summarize, the Vilnius system presents a number of metallicity sensitive, reddening-free parameters which can be used for [Fe/H] and color-excess determinations of globular clusters.

scholarly journals Structure and Evolution of Star Clusters in the Vicinity of the Magellanic Clouds

2021 ◽  
Author(s):  
◽  
Timothy Stuart Banks
Keyword(s):  
Globular Clusters ◽  
Star Clusters ◽  
Mass Range ◽  
Large Magellanic Cloud ◽  
Magellanic Clouds ◽  
Initial Mass Function ◽  
High Mass ◽  
Dynamic State ◽  
Nearby Galaxy ◽  
Photometric System

<p>This thesis describes the collection, reduction, and analysis of Charge Coupled Detector (CCD) images of star clusters. The objects studied are primarily in the Large Magellanic Cloud (LMC), a nearby galaxy. The study of these groupings can provide information such as the initial dynamic state of Globular Clusters, the heavy-clement enrichment rate of the LMC, the distribution of masses that stars form with, and the validity of given stellar evolution models. The majority of the observations were collected at Mount John University Observatory (NZ). Procedures for the collection and transfer of the data are described, along with an overview of the analysis facility and CCDs. Statistical moment-based ellipse fitting was applied to the observations, confirming that trends are evident in the position angles and ellipticities of the clusters, as had been reported in the literature. Artificial images of clusters with known parameters were generated and subjected to the same analysis techniques, revealing apparent trends caused by stochastic processes. Caution should therefore be exercised in the interpretation of observational trends in the structure of young LMC clusters. Isochrones were used to date the 19 clusters. The resulting ages are in good agreement with the literature, as are results from profile modeling. There is no evidence for tidal truncation of the young clusters. Observations were made of two LMC and two Galactic star clusters in a test of imaging clusters with the Vilnius photometric system and a CCD. The colour-magnitude diagrams, distances and interstellar reddenings of the clusters were derived and found to be in agreement with the literature. This is the first time that the standard Vilnius filter set has been used with a CCD. Use of the system for direct imaging of star clusters appears promising. Johnson BV CCD observations were made of the young LMC cluster NGC 2214 and a nearby field using the Anglo-Australian Telescope. It has been suggested in the literature that this elliptical cluster is actually two clusters in the process of merging. No evidence was found from profile fitting or the colour-magnitude diagrams to support this contention. Completeness factors were estimated for the CCD frames. These values were used in conjunction with luminosity functions to estimate the Initial Mass Function (IMF) for NGC 2214. A power-law M-(1+x) was assumed for the IMF (where M is stellar mass relative to that of the Sun Mo), with a good fit being found for x = 1.01 plus-minus 0.09. There is some indication that the low mass end (less than or equal to 3oMo) has a smaller gradient than the high mass end of the derived IMF. The value of x is in reasonable agreement with literature values for other Magellanic IMFs, and not substantially different from the poorly determined Galactic IMFs, suggesting the possibility of a 'universal' IMF over the Magellanic Clouds and our Galaxy in the mass range tilde 1 to tilde 10 Mo.</p>

scholarly journals Galactic calibration of the tip of the red giant branch

2019 ◽  
Vol 36 ◽  
Author(s):  
Jeremy Mould ◽  
Gisella Clementini ◽  
Gary Da Costa
Keyword(s):  
Globular Clusters ◽  
Photometric System ◽  
Low Mass Stars ◽  
Rr Lyrae Stars ◽  
Geometric Calibration ◽  
Rr Lyrae ◽  
Low Mass ◽  
Red Giant ◽  
Extragalactic Distance Scale ◽  
Lyrae Stars

AbstractIndications from Gaia data release 2 are that the tip of the red giant branch (a population II standard candle related to the helium flash in low mass stars) is close to –4 in absolute I magnitude in the Cousins photometric system. Our sample is high-latitude southern stars from the thick disk and inner halo, and our result is consistent with longstanding findings from globular clusters, whose distances were calibrated with RR Lyrae stars. As the Gaia mission proceeds, there is every reason to think an accurate Galactic geometric calibration of tip of the red giant branch will be a significant outcome for the extragalactic distance scale.

scholarly journals Globular Clusters in NGC 5128: The IMACS survey

2006 ◽  
Vol 2 (S235) ◽  
pp. 121-121
Author(s):  
M. Gómez ◽  
D. Geisler ◽  
W. E. Harris ◽  
G. L. H. Harris ◽  
K. A. Woodley
Keyword(s):  
Globular Clusters ◽  
Large Range ◽  
Structural Parameters ◽  
Large Fraction ◽  
Position Angle ◽  
Central Field ◽  
Photometric System ◽  
Different Types ◽  
First Results ◽  
High Resolution Images

AbstractTo extend our recent study of structural parameters of Globular Clusters (GCs) in the giant elliptical NGC 5128 (Gómez et al. 2006), we have obtained new high resolution images with the Magellan 6.5m at Las Campanas Observatory and the IMACS camera. Our images cover an area of 1.2 × 1.2 sq. degrees and have a seeing between 0.4 and 0.7'', thus making it possible to resolve a significant fraction of the GC population, which is now virtually entirely observed given the large spatial and magnitude range.Convolution techniques allow us to find and to study the cluster candidates using the stellar PSF and analytical profiles for their light distribution. We therefore are able to derive structural parameters like size (effective and core radii), ellipticity, position angle and concentration. This is combined with the extensive database in the Washington photometric system by Harris et al. (2004) to select clusters according to shape, extendedness and Washington magnitudes and colours, which has proven very useful in discriminating GCs from foreground stars and background galaxies and for deriving metallicities.Our first results for the central field (15'×15’) indicate that the GCs populate a large range of (MV, rh) parameter space, with typical sizes of Galactic GCs as well as much larger. Combined with our previous data, we find a continuum of clusters in this diagram, with no clear distinction between a variety of different ‘types’ often referred to, such as UCDs, Faint Fuzzies, etc.In addition, a large fraction of GCs show a significant ellipticity whereas a paucity of round clusters is observed. We also confirm with a large (~250) sample that metal-rich clusters are smaller than metal-poor ones, which is in keeping with the general trend found in other galaxies. (e.g. Jordán et al. 2005)

scholarly journals Results from Three Dimensional Spectral Classification of Population II Stars Using the DDO Photometric System

1973 ◽  
Vol 50 ◽  
pp. 176-182
Author(s):  
W. Osborn
Keyword(s):  
Globular Clusters ◽  
Three Dimensional ◽  
Photometric System ◽  
Horizontal Branch ◽  
Intermediate Band ◽  
Theoretical Predictions ◽  
The Mean ◽  
Red Giant ◽  
The Masses

The David Dunlap Observatory (DDO) intermediate-band photometric system described in the previous paper has been used to observe a number of red giant branch, horizontal branch, and asymptotic branch members in each of the five globular clusters M3, M5, M10, M13, and M92. A calibration of the DDO system is described by which it was possible to determine the effective temperatures, surface gravities, [Fe/H] values, and masses of the observed stars. The mean [Fe/H] values for the clusters were found to be −1.01 for M3, −0.68 for M5, −1.44 for M10, −1.69 for M13, and −1.96 for M92. Evidence was found that the masses of the horizontal branch and asymptotic branch stars are systematically smaller than those of red giant branch members. Two stars were discovered to have CN bands that are anomalously strong for Population II objects. The observational results have been compared with the theoretical predictions of two detailed Population II evolutionary tracks and in general the agreement is good.

scholarly journals Structure and Evolution of Star Clusters in the Vicinity of the Magellanic Clouds

2021 ◽  
Author(s):  
◽  
Timothy Stuart Banks
Keyword(s):  
Globular Clusters ◽  
Star Clusters ◽  
Mass Range ◽  
Large Magellanic Cloud ◽  
Magellanic Clouds ◽  
Initial Mass Function ◽  
High Mass ◽  
Dynamic State ◽  
Nearby Galaxy ◽  
Photometric System

<p>This thesis describes the collection, reduction, and analysis of Charge Coupled Detector (CCD) images of star clusters. The objects studied are primarily in the Large Magellanic Cloud (LMC), a nearby galaxy. The study of these groupings can provide information such as the initial dynamic state of Globular Clusters, the heavy-clement enrichment rate of the LMC, the distribution of masses that stars form with, and the validity of given stellar evolution models. The majority of the observations were collected at Mount John University Observatory (NZ). Procedures for the collection and transfer of the data are described, along with an overview of the analysis facility and CCDs. Statistical moment-based ellipse fitting was applied to the observations, confirming that trends are evident in the position angles and ellipticities of the clusters, as had been reported in the literature. Artificial images of clusters with known parameters were generated and subjected to the same analysis techniques, revealing apparent trends caused by stochastic processes. Caution should therefore be exercised in the interpretation of observational trends in the structure of young LMC clusters. Isochrones were used to date the 19 clusters. The resulting ages are in good agreement with the literature, as are results from profile modeling. There is no evidence for tidal truncation of the young clusters. Observations were made of two LMC and two Galactic star clusters in a test of imaging clusters with the Vilnius photometric system and a CCD. The colour-magnitude diagrams, distances and interstellar reddenings of the clusters were derived and found to be in agreement with the literature. This is the first time that the standard Vilnius filter set has been used with a CCD. Use of the system for direct imaging of star clusters appears promising. Johnson BV CCD observations were made of the young LMC cluster NGC 2214 and a nearby field using the Anglo-Australian Telescope. It has been suggested in the literature that this elliptical cluster is actually two clusters in the process of merging. No evidence was found from profile fitting or the colour-magnitude diagrams to support this contention. Completeness factors were estimated for the CCD frames. These values were used in conjunction with luminosity functions to estimate the Initial Mass Function (IMF) for NGC 2214. A power-law M-(1+x) was assumed for the IMF (where M is stellar mass relative to that of the Sun Mo), with a good fit being found for x = 1.01 plus-minus 0.09. There is some indication that the low mass end (less than or equal to 3oMo) has a smaller gradient than the high mass end of the derived IMF. The value of x is in reasonable agreement with literature values for other Magellanic IMFs, and not substantially different from the poorly determined Galactic IMFs, suggesting the possibility of a 'universal' IMF over the Magellanic Clouds and our Galaxy in the mass range tilde 1 to tilde 10 Mo.</p>

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