scholarly journals Infrared modeling of the starburst clone NGC 3603

1999 ◽  
Vol 193 ◽  
pp. 478-479
Author(s):  
Daniel Devost ◽  
Claus Leitherer
Keyword(s):  
Stellar Population ◽  
Main Sequence ◽  
Star Cluster ◽  
Radial Profiles ◽  
Magnitude Diagram

We present results of an HST archive study of the star cluster NGC 3603. The color-magnitude diagram (CMD) and the radial profiles have been derived using HST-nicmos F110W and F171M images. As expected, the CMD shows that the cluster is very young (< 3 Myr) and that a significant portion of the stellar population (M < 4M⊙) is on the pre-main sequence phase. From the radial profiles, we derive a similar half-light radius for both wavebands of 0.17 pc.

scholarly journals Globular cluster candidates in the Galactic bulge: Gaia and VVV view of the latest discoveries

2019 ◽  
Vol 628 ◽  
pp. A45 ◽  
Author(s):  
F. Gran ◽  
M. Zoccali ◽  
R. Contreras Ramos ◽  
E. Valenti ◽  
A. Rojas-Arriagada ◽  
...  
Keyword(s):  
Main Sequence ◽  
Star Clusters ◽  
Forthcoming Paper ◽  
Variable Stars ◽  
Star Cluster ◽  
Proper Motions ◽  
Magnitude Diagram ◽  
Spatial Coordinates ◽  
Red Giant ◽  
Moving Groups

Context. Thanks to the recent wide-area photometric surveys, the number of star cluster candidates have risen exponentially in the last few years. Most detections, however, are based only on the presence of an overdensity of stars in a given region or an overdensity of variable stars, regardless of their distance. As candidates, their detection has not been dynamically confirmed. Therefore, it is currently unknown how many and which of the published candidates are true clusters and which are chance alignments. Aims. We present a method to detect and confirm star clusters based on the spatial distribution, coherence in motion, and appearance on the color-magnitude diagram. We explain and apply this approach to one new star cluster and several candidate star clusters published in the literature. Methods. The presented method is based on data from the second data release of Gaia complemented with data from the VISTA Variables in the Vía Láctea survey for the innermost bulge regions. This method consists of a nearest neighbors algorithm applied simultaneously over spatial coordinates, star color, and proper motions to detect groups of stars that are close in the sky, move coherently, and define narrow sequences in the color-magnitude diagram, such as a young main sequence or a red giant branch. Results. When tested in the bulge area (−10 <  ℓ (deg) <  +10; −10 <  b (deg) <  +10) the method successfully recovered several known young and old star clusters. We report in this work the detection of one new, likely old star cluster, while deferring the others to a forthcoming paper. Additionally, the code has been applied to the position of 93 candidate star clusters published in the literature. As a result, only two of these clusters are confirmed as coherently moving groups of stars at their nominal positions.

scholarly journals Observational hints of a real age spread in the young LMC star cluster NGC 1971

2017 ◽  
Vol 470 (1) ◽  
pp. L77-L81 ◽  
Author(s):  
Andrés E. Piatti ◽  
Andrew Cole
Keyword(s):  
Main Sequence ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Star Cluster ◽  
Stellar Rotation ◽  
Cloud Cluster ◽  
Magnitude Diagram ◽  
Observational Errors ◽  
Age Range

Abstract We report that the serendipitous young Large Magellanic Cloud cluster NGC 1971 exhibits an extended main-sequence turn-off (eMSTO) possibly originated mostly by a real age spread. We used CT1 Washington photometry to produce a colour–magnitude diagram (CMD) with the fiducial cluster features. From its eMSTO, we estimated an age spread of ∼170 Myr (observed age range 100–280 Myr), once observational errors, stellar binarity, overall metallicity variations and stellar rotation effects were subtracted in quadrature from the observed age width.

scholarly journals The LMC Globular Cluster Hodge 11 (=SL 868)

1984 ◽  
Vol 108 ◽  
pp. 43-44
Author(s):  
L. L. Stryker ◽  
J. M. Nemec ◽  
J. E. Hesser ◽  
R.D. McClure
Keyword(s):  
Globular Clusters ◽  
Main Sequence ◽  
Star Cluster ◽  
Open Clusters ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Magnitude Diagram ◽  
The Galaxy ◽  
Lyrae Stars ◽  
Termination Point

The age of the star cluster H11 has been controversial for a number of years. The color-magnitude diagram (CMD) of Walker (1979) to V=21.5 was interpreted as an “…evolved main-sequence, whose termination point corresponds to an age of about 0.6 Gyr, but with a giant branch which is displaced blueward by about Δ (B-V)o=0.4 from the positions of the giant branches of open clusters of similar age in our Galaxy.” On the other hand, the integrated colors are similar to those of metal-poor globular clusters in the Galaxy (Freeman and Gascoigne 1977, and references therein), and “…incompatible with an age of say 0.3 Gyr.” Searle, Wilkinson and Bagnuolo (1980) classify it as Group VII, the oldest group. The system has no RR Lyrae stars (Graham and Nemec 1984).

scholarly journals Fast-rotating giant stars behind the Coma Berenices star cluster

2020 ◽  
Vol 497 (3) ◽  
pp. 2562-2568
Author(s):  
Estefanía Casal ◽  
Matilde Fernández ◽  
Emilio J Alfaro ◽  
Víctor Casanova ◽  
Ángel Tobaruela
Keyword(s):  
Main Sequence ◽  
Star Cluster ◽  
Stellar Clusters ◽  
Main Sequence Stars ◽  
Cluster Membership ◽  
Giant Stars ◽  
Data Release ◽  
Magnitude Diagram ◽  
M Stars ◽  
Fast Rotating

ABSTRACT In the frame of a study of the empirical isochrones of young stellar clusters, we have carried out BVIc Johnson–Cousins photometry of a sample of K and M stars of the Coma Berenices star cluster. All these stars have known rotational periods. Our main goal is to get a valuable reference on the colour–magnitude diagram, Mv versus B − V, for stars with ages within 400–800 Myr. For this purpose, we obtained BVIc photometry with an average upper limit for the precision of about 0.025 mag and used parallaxes from the Gaia Data Release 2. We found that one-third of our sample is located well above the cluster main sequence and these stars are confirmed as background giants by their radial velocities in the Gaia Data Release 2. This misclassification shows that giants with short-surface rotational periods can mimic main-sequence stars if they are located at the appropriate distance. We recommend caution when using rotational periods in order to determine cluster membership. Besides, the gyrochronology technique should be used only when the luminosity class of the stars is well known. Finally, our cleared sample supports an age of ∼600 Myr for Coma Berenices, rather than an age of ∼800 Myr.

scholarly journals The Absolute Magnitude and Stellar Population of a Ba II Star

1973 ◽  
Vol 54 ◽  
pp. 225-228
Author(s):  
R. D. McClure
Keyword(s):  
Stellar Population ◽  
Main Sequence ◽  
Open Cluster ◽  
Absolute Magnitude ◽  
Distance Modulus ◽  
Magnitude Diagram ◽  
The Absolute

A star showing extreme features characteristic of the Ba II stars has been found in the old open cluster NGC 2420. A new colour-magnitude diagram has been constructed for the cluster, and a distance modulus of 11m.7 is obtained by fitting the unevolved main sequence to the zero-age main sequence. The location of the Ba II star is consistent with its being a disc population star of absolute magnitude Mv = −0m.3, mass 1.4 M⊙ and age 2.4 × 109 yr.

scholarly journals Visual–IR Color Gradients in Elliptical Galaxies

1987 ◽  
Vol 127 ◽  
pp. 443-444
Author(s):  
R. F. Peletier ◽  
E. A. Valentijn ◽  
R. F. Jameson
Keyword(s):  
Population Model ◽  
Stellar Population ◽  
Main Sequence ◽  
Elliptical Galaxies ◽  
Strong Constraint ◽  
Average Temperature ◽  
Simultaneous Measurements ◽  
Continuity Of Solutions ◽  
Different Populations ◽  
Color Gradients

Dissipational formation theories (e.g. Larson 1974) predict a metallicity change with distance from the center in elliptical galaxies. Several authors have reported small color gradients in visual colors like B–V and B–R. The interpretation of these data is not easy, due to uncertainties caused by the short wavelength–baseline, and by the presence of a hot stellar population suggested by IUE–data (e.g. Burstein et al. 1986). Simultaneous measurements of visual and visual-infrared colors provide the means to determine both the average temperature of the giant branch and the turnoff–temperature of the main sequence. This allows to model fractional contributions of different populations, including age– and metallicity–effects. The required continuity of solutions at different radii provides a strong constraint in selecting a more unique overall population model, and relieves the ambiguous interpretation of single measurements.

scholarly journals Fossil group origins

2018 ◽  
Vol 618 ◽  
pp. A172 ◽  
Author(s):  
E. M. Corsini ◽  
L. Morelli ◽  
S. Zarattini ◽  
J. A. L. Aguerri ◽  
L. Costantin ◽  
...  
Keyword(s):  
Stellar Population ◽  
Line Strength ◽  
Abundance Ratio ◽  
Element Abundance ◽  
Population Parameters ◽  
Stellar Kinematics ◽  
Massive Galaxies ◽  
Radial Profiles ◽  
Major Merger ◽  
Satellite Galaxies

Context. Fossil groups (FGs) are galaxy aggregates with an extended and luminous X-ray halo, which are dominated by a very massive early-type galaxy and lack of L∗ objects. FGs are indeed characterized by a large magnitude gap between their central and surrounding galaxies. This is explained by either speculating that FGs are failed groups that formed without bright satellite galaxies and did not suffer any major merger, or by suggesting that FGs are very old systems that had enough time to exhaust their bright satellite galaxies through multiple major mergers. Aims. Since major mergers leave signatures in the stellar populations of the resulting galaxy, we study the stellar population parameters of the brightest central galaxies (BCGs) of FGs as a benchmark against which the formation and evolution scenarios of FGs can be compared. Methods. We present long-slit spectroscopic observations along the major, minor, and diagonal axes of NGC 6482 and NGC 7556, which are the BCGs of two nearby FGs. The measurements include spatially resolved stellar kinematics and radial profiles of line-strength indices, which we converted into stellar population parameters using single stellar-population models. Results. NGC 6482 and NGC 7556 are very massive (M∗ ≃ 1011.5 M⊙) and large (D25 ≃ 50 kpc) galaxies. They host a centrally concentrated stellar population, which is significantly younger and more metal rich than the rest of the galaxy. The age gradients of both galaxies are somewhat larger than those of the other FG BCGs studied so far, whereas their metallicity gradients are similarly negative and shallow. Moreover, they have negligible gradients of α-element abundance ratio. Conclusions. The measured metallicity gradients are less steep than those predicted for massive galaxies that formed monolithically and evolved without experiencing any major merger. We conclude that the observed FGs formed through major mergers rather than being failed groups that lacked bright satellite galaxies from the beginning.

scholarly journals Main-sequence broadening, Be stars, and stellar rotation inhand χ Persei

1994 ◽  
Vol 162 ◽  
pp. 151-152
Author(s):  
J. Denoyelle ◽  
C. Aerts ◽  
C. Waelkens
Keyword(s):  
Main Sequence ◽  
Large Fraction ◽  
Variable Stars ◽  
Theoretical Studies ◽  
Be Stars ◽  
Stellar Rotation ◽  
B Stars ◽  
Fundamental Parameters ◽  
Magnitude Diagram ◽  
Double Cluster

The double cluster h andxPersei is one of the richest clusters containing early-B stars, and therefore is important for observational and theoretical studies on the fundamental parameters of massive stars. The colour-magnitude diagram of the double cluster shows an important scatter (see Figure 1). It has long been known thathandxPersei are extremely rich in Be stars (Slettebak 1968). Our previous contention (Waelkens et al. 1990) that the large-amplitude variable stars we discovered are also Be stars, could be confirmed for a few objects. Rotation velocities for stars inhandxPersei are usually high, which is not surprising in view of the large fraction of Be stars.

A Deep Luminosity Function for 47 Tucanae

1985 ◽  
Vol 113 ◽  
pp. 81-83
Author(s):  
William E. Harris ◽  
James E. Hesser
Keyword(s):  
Luminosity Function ◽  
Main Sequence ◽  
Ccd Photometry ◽  
Magnitude Diagram

CCD photometry in B and V reaching B(lim) ≃ 25 has been employed to obtain the luminosity function and color-magnitude diagram for the main sequence of 47 Tuc. For 5<Mv<10 we find that its LF is essentially flat (Δlog n/Δm~0). The CMD is successfully matched by isochrones with [Fe/H] = −0.5 and t ≃ 15 × 109y.

Sign in / Sign up

Export Citation Format

Share Document