Interstellar extinction towards open clusters and Galactic structure

Joshi, Y. C.

doi:10.1111/j.1365-2966.2005.09391.x

Cited by 50 publications

(55 citation statements)

References 30 publications

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“…The age of VVV CL002 is uncertain, but the proposed lower limit of 6.5 Gyr, its subsolar metallicity, and its height above the Galactic plane, twice the scale height of young objects (Joshi 2005), argue in favor of an old cluster. On the other hand, Friel (1995) showed that old open clusters are completely absent in the inner ∼7 kpc from the Galactic center.…”

Section: Discussionmentioning

confidence: 99%

Three Galactic globular cluster candidates

Bidin

Mauro

Geisler

et al. 2011

A&A

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Context. The census of Galactic globular clusters (GCs) is still incomplete, and about ten new objects are supposed to await discovery, hidden behind the crowded and reddened regions of the Galactic bulge and disk. Aims. We investigated the nature of three new GC candidates, discovered in the frames collected by the Vista Variables in the Via Lactea (VVV) near-infrared survey. They will be called VVV CL002, VVV CL003, and VVV CL004. Methods. We studied the results of point-spread-function near-infrared photometry from VVV data for the three objects and their surrounding fields, the proper motion information available in the literature and, when possible, we derived the cluster parameters by means of calibrated indices measured on the color-magnitude diagrams. Results. The evidence shows that VVV CL002 is a newly discovered, small, moderately metal-rich ([Fe/H] ≈ −0.4) Galactic GC. It is located at a Galactocentric distance of 0.7 ± 0.9 kpc, and it could be one of the nearest GC to the Galactic center. Its characteristics are more similar to those of low-mass, Palomar-like GCs than to more classical, old, and massive bulge GCs. VVV CL003 is the first star cluster discovered in the Galactic disk on the opposite side of the center with respect to the Sun, at a Galactocentric distance of ∼5 kpc. Its high metallicity ([Fe/H] ≈ −0.1) and location point to an open cluster, but a GC cannot be excluded. VVV CL004, on the contrary, is most probably only a random clump of field stars, as indicated by both its low statistical significance and by the impossibility to distinguish its stars from the surrounding field population. Conclusions. We claim the detection of i) a new Galactic GC, deriving an estimate of its basic parameters; ii) a stellar aggregate, probably an open cluster, in the disk directly beyond the Galactic center; and iii) an overdensity of stars, most probably an asterism.

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Section: Discussionmentioning

confidence: 99%

Three Galactic globular cluster candidates

Bidin

Mauro

Geisler

et al. 2011

A&A

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“…These results further strengthen, as noted previously by Phelps et al (1994) and Chen et al (2003), that the sample of outer disc clusters has been subjected to significant selection effects; they are readily observed if they are away from the plane due to high interstellar extinction in optical wavelengths at low latitudes in the direction of Galactic anti-centre. Again they are likely to be the older, as the young OCs have yet to move out from their birthplaces in Galactic midplane and, thus, obscured by heavy extinction caused by about 90% of the absorbing material lying within -5< b <5 deg of the Galactic plane (Joshi 2005) which raises the level of difficulty in observing them in visible bands.…”

Section: Comparison With Chemodynamical Modelsmentioning

confidence: 99%

The evolution of the Milky Way: new insights from open clusters

Reddy¹,

Lambert²,

Giridhar³

2016

Mon. Not. R. Astron. Soc.

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We have collected high-dispersion echelle spectra of red giant members in the twelve open clusters (OCs) and derived stellar parameters and chemical abundances for 26 species by either line equivalent widths or synthetic spectrum analyses. We confirm the lack of an age−metallicity relation for OCs but argue that such a lack of trend for OCs arise from the limited coverage in metallicity compared to that of field stars which span a wide range in metallicity and age. We confirm that the radial metallicity gradient of OCs is steeper (flatter) for R gc < 12 kpc (>12 kpc). We demonstrate that the sample of clusters constituting a steep radial metallicity gradient of slope −0.052±0.011 dex kpc −1 at R gc < 12 kpc are younger than 1.5 Gyr and located close to the Galactic midplane (| z| < 0.5 kpc) with kinematics typical of the thin disc. Whereas the clusters describing a shallow slope of −0.015±0.007 dex kpc −1 at R gc > 12 kpc are relatively old, thick disc members with a striking spread in age and height above the midplane (0.5 < | z| < 2.5 kpc). Our investigation reveals that the OCs and field stars yield consistent radial metallicity gradients if the comparison is limited to samples drawn from the similar vertical heights. We argue via the computation of Galactic orbits that all the outer disc clusters were actually born inward of 12 kpc but the orbital eccentricity has taken them to present locations very far from their birthplaces.

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“…In general, for the remaining longitude range, absorption is higher and happens mostly between 1 and 2 kpc from the Sun. Joshi (2005) also determined that the dust plane is tilted by 0.6…”

Section: Interstellar Extinctionmentioning

confidence: 99%

“…Joshi (2005) studied the interstellar-absorption pattern within ∼ 4 − 5 kpc using catalogued reddening values towards 722 OCs. He found that absorption approximately follows a sinusoidal curve with Galactic longitude, with the highest values occurring at l ∼ 30-50…”

Section: Interstellar Extinctionmentioning

confidence: 99%

Observational properties of the open cluster system of the Milky Way and what they tell us about our Galaxy

Moitinho¹

2009

Proc. IAU

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Abstract. Almost 80 years have passed since Trumpler's analysis of the Galactic open cluster system laid one of the main foundations for understanding the nature and structure of the Milky Way. Since then, the open cluster system has been recognised as a key source of information for addressing a wide range of questions about the structure and evolution of our Galaxy. Over the last decade, surveys and individual observations from the ground and space have led to an explosion of astrometric, kinematic and multiwavelength photometric and spectroscopic open cluster data. In addition, a growing fraction of these data is often time-resolved. Together with increasing computing power and developments in classification techniques, the open cluster system reveals an increasingly clearer and more complete picture of our Galaxy. In this contribution, I review the observational properties of the Milky Way's open cluster system. I discuss what they can and cannot teach us now and in the near future about several topics such as the Galaxy's spiral structure and dynamics, chemical evolution, large-scale star formation, stellar populations and more.Keywords. catalogs, ISM: extinction, Galaxy: evolution, Galaxy: disk, open clusters and associations: general PreambleIn 1930, Robert Trumpler published his seminal paper in which he proves the existence of the interstellar medium (ISM). In that paper, Trumpler showed how distances to open clusters (OCs) derived from the apparent magnitudes of cluster stars of known spectral types are systematically greater than those derived from their apparent sizes, and how the effect increases with distance. He correctly attributed this phenomenon to the presence of an intervening medium. This was the first paper using OCs as tracers of Galactic structure.

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Interstellar extinction towards open clusters and Galactic structure

Cited by 50 publications

References 30 publications

Three Galactic globular cluster candidates

Three Galactic globular cluster candidates

The evolution of the Milky Way: new insights from open clusters

Observational properties of the open cluster system of the Milky Way and what they tell us about our Galaxy

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