A high relative precision colour-magnitude diagram of M67

Sandquist, Eric L.

doi:10.1111/j.1365-2966.2004.07174.x

Cited by 96 publications

(164 citation statements)

References 55 publications

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“…In the upper diagram of Fig. 5, we have plotted the index CaT measured by Cenarro et al (2001) against M V , using the distance moduli listed by Sandquist (2004) and by Harris (1996). This diagram shows that the red clump stars (or red HB stars) in M 67 and M 71 do not deviate systematically from the sequence of RGB stars.…”

Section: Estimate Of Metallicity From the Infrared Caii Linesmentioning

confidence: 99%

“…However, a few of these stars in the open cluster M 67 and the globular cluster M 71 were included in the catalogue of CaII line strengths measured by Cenarro et al (2001). According to Sandquist (2004) and references therein, M 67 is 4 Gyr old and has approximately solar composition. M71 is much older, ∼10 Gyr, and more metal poor, [Fe/H] ∼ -0.7 (e.g., Salaris & Weiss 2002).…”

Section: Estimate Of Metallicity From the Infrared Caii Linesmentioning

confidence: 99%

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Whiting 1: the youngest globular cluster associated with the Sagittarius dwarf spheroidal galaxy

Carraro¹,

Zinn²,

Bidin³

2007

A&A

120

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Context. Recently, Carraro (2005) drew attention to the remarkable star cluster Whiting 1 by showing that it lies about 40 kpc from the Sun and is therefore unquestionably a member of the Galactic halo (b = −60.6 deg). Its Color Magnitude Diagram (CMD) indicated that Whiting 1 is very young (∼5 Gyr) for a globular cluster. It is very likely that Whiting 1 originated in a dwarf galaxy that has since been disrupted by the Milky Way. Aims. The main goals of this investigation were to constrain better the age, metallicity, and distance of Whiting 1 and to assess whether it belongs to a stellar stream from the Sagittarius dwarf spheroidal galaxy (Sgr dSph). Methods. Deep CCD photometry in the BVI pass-bands obtained with the VLT is used to improve the quality of the CMD and to determine the cluster's luminosity function and surface density profile. High-resolution spectrograms obtained with Magellan are used to measure the cluster's radial velocity and to place limits on its possible metallicity. The measurements of distance and radial velocity are used to test the cluster's membership in the stellar streams from the Sgr dSph. Results. From our CMD of Whiting 1, we derive new estimates for the cluster's age (6.5 +1.0 −0.5 Gyr), metallicity (Z = 0.004 ± 0.001, [Fe/H] = -0.65), and distance (29.4 +1.8 −2.0 kpc). From echelle spectrograms of three stars, we obtain -130.6 ± 1.8 km s −1 for the cluster's radial velocity and show from measurements of two infra-red CaII lines that the [Fe/H] of the cluster probably lies in the range -1.1 to -0.4. Both the luminosity function and the surface density profile suggest that the cluster has undergone tidal stripping by the Milky Way. We demonstrate that the position of Whiting 1 on the sky, its distance from the Sun, and its radial velocity are identical to within the errors of both the theoretical predictions of the trailing stream of stars from the Sgr dSph galaxy and the previous observations of the M giant stars that delineate the streams. Conclusions. With the addition of Whiting 1, there is now strong evidence that 6 globular clusters formed within the Sgr dSph. Whiting 1 is particularly interesting because it is the youngest and among the most metal rich. The relatively young age of Whiting 1 demonstrates that this dwarf galaxy was able to form star clusters for a period of at least 6 Gyr, and the age and metallicity of Whiting 1 are consistent with the age-metallicity relationship in the main body of the Sgr dSph. The presence now of Whiting 1 in the Galactic halo provides additional support for the view that the young halo clusters originated in dwarf galaxies that have been accreted by the Milky Way.

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Section: Estimate Of Metallicity From the Infrared Caii Linesmentioning

confidence: 99%

Section: Estimate Of Metallicity From the Infrared Caii Linesmentioning

confidence: 99%

Whiting 1: the youngest globular cluster associated with the Sagittarius dwarf spheroidal galaxy

Carraro¹,

Zinn²,

Bidin³

2007

A&A

120

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“…Besides having a well-developed red-giant branch, it is a good target because its composition is almost solar (Tautvaišienė et al 2000;Randich et al 2006;Pace et al 2008) and the age somewhat comparable, at 2.6 Gy (WEBDA 2009). It has been well studied in various aspects Sandquist 2004), including as part of a census of binaries (Latham et al 1992). Finally, we had already observed a homogeneous group of stars in M 67 (Melo et al 2001; hereafter Paper I), verifying the modest rotational velocities, and could use these data as a starting point.…”

Section: Radial Velocities In Open Clustersmentioning

confidence: 99%

Gravitational redshifts in main-sequence and giant stars

Pasquini

Melo

Chavero

et al. 2011

A&A

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Context. Precise analyses of stellar radial velocities is able to reveal intrinsic causes of the wavelength shifts of spectral lines (other than Doppler shifts due to radial motion), such as gravitational redshifts and convective blueshifts. Aims. Gravitational redshifts in solar-type main-sequence stars are expected to be some 500 m s −1 greater than those in giants. We search for this difference in redshifts among groups of open-cluster stars that share the same average space motion and thus have the same average Doppler shift. Methods. We observed 144 main-sequence stars and cool giants in the M 67 open cluster using the ESO FEROS spectrograph and obtained radial velocities by means of cross-correlation with a spectral template. Binaries and doubtful members were not analyzed, and average spectra were created for different classes of stars. Results. The M 67 dwarf and giant radial-velocity distributions are each well represented by Gaussian functions, which share the same apparent average radial velocity to within 100 m s −1 . In addition, dwarfs in M 67 appear to be dynamically hotter (σ = 0.90 km s −1 ) than giants (σ = 0.68 km s −1 ). Conclusions. We fail to detect any difference in the gravitational redshifts of giants and MS stars. This is probably because of the differential wavelength shifts produced by the different hydrodynamics of dwarf and giant atmospheres. Radial-velocity differences measured between unblended lines in averaged spectra vary with line-strength: stronger lines are more blueshifted in dwarfs than in giants, apparently removing any effect of the gravitational redshift. Synthetic high-resolution spectra are computed from three dimensional (3D) hydrodynamic model atmospheres for both giants and dwarfs, and synthetic wavelength shifts obtained. In agreement with observations, 3D models predict substantially smaller wavelength-shift differences than expected from gravitational redshifts only. The procedures developed could be used to test 3D models for different classes of stars, but will ultimately require high-fidelity spectra for measurements of wavelength shifts in individual spectral lines.

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“…(b) Star names from van Zeipel & Lindgren (1921); coordinates from Kiss et al (2001); B and V magnitudes from Kalirai et al (2001); I C magnitudes from Nilakshi & Sagar (2002); K S magnitudes from 2MASS (c) Star names from Cannon & Lloyd (1970); coordinates from Stetson (2000) and Lasker et al (1990); B and V magnitudes from Anthony- Twarog et al (1990); I C and R magnitudes from Stetson (2000); K S magnitudes from 2MASS. (d) Star names from Fagerholm (1906); coordinates from Fan et al (1996); B, V and I C magnitudes from Sandquist (2004); B magnitude for star 286 and R magnitudes from Janes & Smith (1984); K S magnitudes from 2MASS. (e) Star names and V and I c magnitudes from Gim et al (1998a); J1950 coordinates from Kustner (1923), precessed to J2000; B magnitudes from Mochejska & Kaluzny (1999); K S magnitudes from 2MASS.…”

Section: Introductionmentioning

confidence: 99%

Chemical abundance analysis of the open clusters Cr 110, NGC 2099 (M 37), NGC 2420, NGC 7789, and M 67 (NGC 2682)

Pancino

Carrera

Rossetti

et al. 2010

A&A

194

206

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Context. The present number of Galactic Open Clusters that have high resolution abundance determinations, not only of [Fe/H], but also of other key elements, is largely insufficient to enable a clear modeling of the Galactic Disk chemical evolution. Aims. To increase the number of Galactic Open Clusters with high quality measurements. Methods. We obtained high resolution (R∼30 000), high quality (S/N∼50-100 per pixel), echelle spectra with the fiber spectrograph FOCES, at Calar Alto, Spain, for three red clump stars in each of five Open Clusters. We used the classical Equivalent Width analysis method to obtain accurate abundances of sixteen elements: Al,

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A high relative precision colour-magnitude diagram of M67

Cited by 96 publications

References 55 publications

Whiting 1: the youngest globular cluster associated with the Sagittarius dwarf spheroidal galaxy

Whiting 1: the youngest globular cluster associated with the Sagittarius dwarf spheroidal galaxy

Gravitational redshifts in main-sequence and giant stars

Chemical abundance analysis of the open clusters Cr 110, NGC 2099 (M 37), NGC 2420, NGC 7789, and M 67 (NGC 2682)

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