Category Archives: Uncategorized

[paper] CCD Photometry of the Globular Cluster ESO 452-SC11

Cornish, Alexis S. M.; Phelps, Randy L.; Briley, Michael M.; Friel, Eileen D.

“CCD Photometry of the Globular Cluster ESO 452-SC11”

The globular cluster ESO 452-SC11 has been observed using Johnson V and Cousins I filters, and point-spread function photometry has been performed. The resulting color-magnitude diagrams were compared to theoretical isochrones to derive the cluster’s age, overall chemical composition, and distance modulus. These isochrone models include those published by Girardi et al. and Bergbusch & VandenBerg, with BVRI color-Teff relations as described by VandenBerg & Clem, and Demarque et al. (known as the Yale isochrones). From the Yale isochrones, it is estimated that the cluster has an age of 9-11 Gyr, a metallicity -1.4 dex

The Astronomical Journal, Volume 131, Issue 5, pp. 2543-2550

ADS Link

[paper] Globular cluster system and Milky Way properties revisited

E. Bica – C. Bonatto – B. Barbuy – S. Ortolani

Globular cluster system and Milky Way properties revisited

“Aims. Updated data of the 153 Galactic globular clusters are used to readdress fundamental parameters of the Milky Way, such as the distance of the Sun to the Galactic centre, the bulge and halo structural parameters, and cluster destruction rates.
Methods. We build a reduced sample that has been decontaminated of all the clusters younger than 10 Gyr and of those with retrograde orbits and/or evidence of relation to dwarf galaxies….”

Astronomy and Astrophysics, Volume 450, Issue 1, April IV 2006, pp.105-115

ADS link to the paper

[paper] Probable member stars of the gravitational theory-testing globular clusters AM 1, Pal 3 and Pal 14

Hilker, M.
Probable member stars of the gravitational theory-testing globular clusters AM 1, Pal 3 and Pal 14

Astronomy and Astrophysics, Volume 448, Issue 1, March II 2006, pp.171-180

“Some of the Galactic outer halo globular clusters are excellent tools to probe gravitational theories in the regime of weak accelerations. The measurement of the line-of-sight velocity dispersion among stars in these clusters will differentiate between the validity of Newtonian dynamics (low velocity dispersion) and the possiblity of modified Newtonian dynamics (MOND) or dark matter dominated globular clusters (high velocity dispersion). In this paper, the properties of probable member stars of the three best-case gravitational theory-testing clusters AM 1, Pal 3 and Pal 14 are presented….”

ADS link

[Press release] A River of Stars Streaming Across the Northern Sky

Astronomers Discover a River of Stars Streaming Across the Northern Sky

PASADENA, Calif.–Astronomers have discovered a narrow stream of stars extending at least 45 degrees across the northern sky. The stream is about 76,000 light-years distant from Earth and forms a giant arc over the disk of the Milky Way galaxy…The stream emanates from a cluster of about 50,000 stars known as NGC 5466.

[preprint] Abundance anomalies in NGC 2808

NGC 2808 :: Preprint

Abundance anomalies in NGC 2808

Authors: G. Pace, A. Recio-Blanco, G. Piotto, Y. Momany
Comments: 11 pages, 7 figures, accepted by A&A

“We present metallicity measurements of 25 stars in the blue horizontal branch of the Galactic globular cluster NGC 2808. Our measurements are based on moderate-resolution spectra taken with the multi-object fiber facility FLAMES-UVES, mounted on Kueyen at the Very Large Telescope. We confirm that stars hotter than a threshold temperature have super-solar abundance, while the cooler ones respect the nominal metallicity of the cluster, i.e. [Fe/H] ~ -1.1….”


[preprint] Detection of a 45 Degree Tidal Stream Associated with the GC NGC 5466

NGC 5466 :: preprint

C. J. Grillmair, R. Johnson

“Detection of a 45 Degree Tidal Stream Associated with the Globular Cluster NGC 5466”

We report on the detection in Sloan Digital Sky Survey data of a 45 degree tidal stream of stars, extending from Bootes to Ursa Major, which we associate with the halo globular cluster NGC 5466. Using an optimal contrast, matched filter technique, we find a long, almost linear stellar stream with an average width of 1.4 degrees. The stream is an order of magnitude more tenuous than the stream associated with Palomar 5. The stream’s orientation on the sky is consistent to a greater or lesser extent with existing proper motion measurements for the cluster.


[Press release] How to Steal a Million Stars?

[ESO press release]

How to Steal a Million Stars?
VLT Study Reveals Troubled Past of Globular Cluster Messier 12

Based on observations with ESO’s Very Large Telescope, a team of Italian astronomers reports that the stellar cluster Messier 12 must have lost to our Milky Way galaxy close to one million low-mass stars.

ESO PR Photo 04a/06
ESO PR Photo 04a/06

The Central Part of Messier 12

In the solar neighbourhood and in most stellar clusters, the least massive stars are the most common, and by far“, said Guido De Marchi (ESA), lead author of the study. “Our observations with ESO’s VLT show this is not the case for Messier 12.

The team, which also includes Luigi Pulone and Francesco Paresce (INAF, Italy), measured the brightness and colours of more than 16,000 stars within the globular cluster Messier 12 with the FORS1 multi-mode instrument attached to one of the Unit Telescopes of ESO’s VLT at Cerro Paranal (Chile). The astronomers could study stars that are 40 million times fainter than what the unaided eye can see (magnitude 25).