Cool carbon stars in the halo: A new survey based on 2MASS

Mauron, N.; Azzopardi, M.; Gigoyan, K. S.; Kendall, T. R.

doi:10.1051/0004-6361:20034264

Cited by 44 publications

(80 citation statements)

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“…Zero point adjustment Mauron et al (2004) have observed a ∼±10 km s −1 dispersion in the velocity residuals of several APM stars they used as velocity templates. Such zero point uncertainty suggest that the Totten & Irwin (1998) velocity determination of C stars may have errors larger than the quoted values.…”

Section: Velocity Determinationmentioning

confidence: 99%

“…Weinberg & Nikolaev (2001) have shown that N-type C stars can be used, under certain colour restrictions, as reliable standard candles showing a small dispersion in M K . More recently Mauron et al (2004) followed a similar method to determine the distances for several halo C stars. This approach is preferable to the P−L relation which requires the C star to be a Mira of known period.…”

Section: Introductionmentioning

confidence: 99%

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C stars as kinematic probes of the Milky Way disk from 9 to 15 kpc

Demers¹,

Battinelli²

2007

A&A

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Context. The availability, from 2MASS, of a large homogeneous sample of Galactic C stars and the recognition that their absolute magnitude can be accurately determined offer the possibility to use them as kinematical probes to investigate motions in the thin or thick disks. Aims. Determine the radial velocities for 70 C stars, a few degrees from the Galactic plane and distributed in longitudes from 60 • to 220 • . Methods. Spectra, with a resolution of 4300, were obtained with the DAO 1.8 m telescope during 6 beautiful nights in October 2006. Results. The rotation velocities of C stars with 60 • < < 150 • suggest a flat rotation curve to 15 kpc. A number of stars have velocities that do not fit the thin disk rotation. Some of them, toward = 200 • are most probably members of the Canis Major overdensity. Conclusions. Effort should be made to extend the rotation curve to more that 20 kpc.Key words. stars: carbon -stars: kinematics -Galaxy: disk -Galaxy: kinematics and dynamics IntroductionThe importance of galactic potentials in shaping the chemodynamical evolution of stellar populations is well known. Unfortunately, the surface mass distribution of the Milky Way is still poorly constrained, even while our knowledge of Galactic stellar abundance distributions grows ever more detailed. One reason for this shortcoming is the difficulty of determining the Galactic rotation curve in the outer disk.Recently, Carignan et al. (2006) which they might have been born but still relatively young, with smaller random velocities than older tracers (e.g. planetary nebulae). They are believed to be members of the thin disk population (e.g. Feast et al. 2006).In the late 80's, Aaronson and collaborators recognized that C stars could be useful bright kinematical probes (Aaronson et al. 1989(Aaronson et al. , 1990. They collected hundreds of radial velocities of disk (b ≈ 0 • ) C stars, with JHK photometry. The fact that these C stars were extremely unevenly distributed in galactic latitude made the interpretation of their results unreliable (Schechter et al. 1988). A study of the kinematics of the C stars toward the anticenter was published by Metzger & Schechter (1994). Beside the untimely death of Aaronson we believe there are two main reasons why these data never yielded significant insights in the kinematics of the outer disk: 1) the selection of C stars from objective-prism spectra leads to highly inhomogeneous samples containing faint bluish C stars mixed with brighter genuine N-type C stars (see Demers et al. 2002) thus artificially increasing the observed K absolute magnitude spread; 2) the estimate of distances and colors for stars with b ≈ 0 • requires a quite accurate knowledge of the extinction across the disk.More recently, Nakashima et al. (2000) obtained the rotation curve of the outer disk using the radial velocity of a few C-and O-rich SiO maser emission Miras located very close to the Galactic plane. Absolute I magnitudes were deduced from the Mira's P − L relation. Not knowing individual reddening, the a...

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Section: Velocity Determinationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

C stars as kinematic probes of the Milky Way disk from 9 to 15 kpc

Demers¹,

Battinelli²

2007

A&A

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“…There are no such objects with K > 11 because AGB stars as faint as this in K (and consequently very distant in the halo) are very rare, and are only found with specific methods (see, e.g. Mauron et al 2004Mauron et al , 2005. We suggest that HES objects with J − K < 1 are red giant branch objects, or for a small fraction, dwarfs (see below).…”

Section: Discussionmentioning

confidence: 87%

“…This is obviously due to its blue−visible spectral range. For example, HES missed 11 C stars listed in Mauron et al (2004Mauron et al ( , 2005, although these objects satisfy R < 16, b < −30 • and δ < +2 • . The reason is that their B − R colour is too large and the signal at blue wavelengths is too faint.…”

Section: Mass Photometrymentioning

confidence: 99%

“…Appendices and Table 1 are only available in electronic form at http://www.aanda.org Mauron et al (2004Mauron et al ( , 2005 where candidate C stars were selected by their photometric colours in the 2MASS point-source catalogue (Skrutskie et al 2006) and with |b| > 20 • . Together, these works identified ∼130 cool AGB C stars located in the halo and with distances up to 130 kpc.…”

Section: Introductionmentioning

confidence: 99%

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The properties of carbon stars found in the Byurakan and the Hamburg/ESO surveys

Mauron¹,

Gigoyan

Kendall

2006

A&A

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Aims. We analyse two samples of high latitude carbon stars found in two objective-prism surveys: the First Byurakan survey (FBS) and the Hamburg/ESO survey (HES). We determine the composition of these samples in cool AGB stars, warmer giants and dwarf carbon stars. Methods. We list 44 new carbon stars found in the FBS and use near-infrared photometric catalogues (DENIS, 2MASS) to investigate the observational and statistical properties of the surveys. The SuperCOSMOS and USNO-B1.0 catalogues are used to study proper motions and to identify dwarfs. Results. The colour-magnitude and colour-colour diagrams, either with visual magnitudes or with infrared data, show that the HES selects faint and relatively warm carbon stars, whereas FBS is less deep, but gives cooler objects. By comparing DENIS and 2MASS photometry, we find that HES objects with J − K ≤ 1 are mostly non-variable giants while clear variability is often seen for J − K ≥ 1, indicating AGB stars. By using SuperCOSMOS proper motions, 9 HES objects are found to have a proper motion µ greater than 30 mas yr −1 (3σ detection). Five of these objects are detected at the ≥5σ level. These 9 HES objects are dwarf carbon stars, including two that could belong to the halo population. The 9 carbon dwarfs are remarkably bright and deserve further study.

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