Spiral structure of the third galactic quadrant and the solution to the Canis Major debate

Moitinho, A.; Vazquez, R. A.; Carraro, G.; Baume, G.; Giorgi, E. E.; Lyra, Wladimir

doi:10.1111/j.1745-3933.2006.00163.x

Cited by 98 publications

(175 citation statements)

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“…The presence of "blue plume" stars in this part of the sky has been used to argue further for the presence of a dwarf galaxy nucleus in CMa Martínez-Delgado et al 2005;Dinescu et al 2005;Butler et al 2007). However, these young stars have also been more A&A 509, A102 (2010) prosaically attributed to the presence of previously unknown features of spiral arm structure (Carraro et al 2005;Moitinho et al 2006).…”

Section: Introductionmentioning

confidence: 99%

The metallicity of the open cluster Tombaugh 2

Villanova

Randich²,

Geisler

et al. 2010

A&A

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Context. Open clusters are excellent tracers of the structure, kinematics, and chemical evolution of the disk and a wealth of information can be derived from the spectra of their constituent stars. Aims. We investigate the nature of the chemical composition of the outer disk open cluster Tombaugh 2. This has been suggested to be a member of the GASS/Mon substructure, and a recent study by Frinchaboy et al. (2008) suggested that this was a unique open cluster in possessing an intrinsic metal abundance dispersion. We aim to investigate such claims. Methods. High resolution VLT+GIRAFFE spectra in the optical are obtained and analyzed for a number of stars in the Tombaugh 2 field, together with independent UBVI C photometry. Radial velocities and position in the color−magnitude diagram are used to assess cluster membership. The spectra, together with input atmospheric parameters and model atmospheres, are used to determine detailed chemical abundances for a variety of elements in 13 members with good spectra. Results. We find the mean metallicity to be [Fe/H] = −0.31 ± 0.02 with no evidence for an intrinsic abundance dispersion, in contrary to the recent results of Frinchaboy et al. (2008, MNRAS, 391, 39). We find Ca and Ba to be slightly enhanced, while Ni and Sc are solar. The r-process element Eu was found to be enhanced, giving an average [Eu/Ba] = +0.17. The Li abundance decreases with T eff on the upper giant branch and maintains a low level for red clump stars. The mean metallicity we derive agrees well with that expected from the radial abundance gradient in the disk for a cluster at its Galactocentric distance. Conclusions. Tombaugh 2 is found to have abundances as expected from its Galactocentric distance and no evidence for any intrinsic metallicity dispersion. The surprising result found by Frinchaboy et al. (2008), which is the presence of two distinct abundance groups within the cluster, implying either a completely unique open cluster with an intrinsic metallicity spread or a very unlikely superposition of a cold stellar stream and a very distant open cluster, is not supported by our new result.

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Section: Introductionmentioning

confidence: 99%

The metallicity of the open cluster Tombaugh 2

Villanova

Randich²,

Geisler

et al. 2010

A&A

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“…Specifically, a new vision of the (stellar) spiral structure and warp has emerged in which it is seen that the Norma-Cygnus (or Outer) arm is defined over the whole 3GQ and that the Local (Orion) arm is not a small spur, but a large structure that reaches the warped outer disc (Carraro et al 2005;Moitinho et al 2006b;Vázquez et al 2008). An unexpected repercussion of this scenario has been to The original photometry is only available in electronic form at CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/511/A38 on leave from Dipartimento di Astronomia, Università di Padova, Vicolo Osservatorio 2, 35122 Padova, Italy cast considerable doubt on the existence of the highly publicised Canis Major dwarf galaxy (Martin et al 2004).…”

Section: Introductionmentioning

confidence: 99%

Open clusters in the Third Galactic Quadrant III. Alleged binary clusters

Vazquez

Moitinho

Carraro³

et al. 2010

A&A

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Aims. We aim to determine accurate distances and ages of eight open clusters in order to: (1) assess their possible binarity (2) provide probes to trace the structure of the Third Galactic Quadrant. Methods. Cluster reddenings, distances, ages and metallicities are derived from ZAMS and isochrone fits in UBVRI photometric diagrams. Field contamination is reduced by restricting analysis to stars within the cluster limits derived from star counts. Further membership control is done by requiring that stars have consistent positions in several diagrams and by using published spectral types. Results. The derived distances, ages and metallicities have shown that none of the analysed clusters compose binary/double systems. Of the four candidate pairs, only NGC 2383/NGC 2384 are close to each other, but have different metallicities and ages. Ruprecht 72 and Ruprecht 158 are not clusters but fluctuations of the field stellar density. Haffner 18 is found to be the superposition of two stellar groups at different distances: Haffner 18(1) at 4.5 kpc and Haffner 18(2) between 9.5 and 11.4 kpc from the Sun. The derived distances and ages have been used to situate the clusters in the Galactic context. In particular, young stellar groups trace spiral structure at large Galactocentric radii. At least two clusters formed during the last few 10 8 yr in an interstellar medium with less than solar abundances. Conclusions. In contrast with the LMC, double clusters are apparently rare, or even non existent, in the undisturbed environment of the Third Galactic Quadrant. This leaves open the question of whether binary clusters form more easily toward denser and more violent regions of the Milky Way such as the inner Galaxy.

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“…Although results for NGC 2302 have been included in a number of large scale studies of open-cluster surveys aimed at a variety of purposes (see, e.g., Santos-Silva & Gregorio-Hetem 2012; Kharchenko et al 2009a,b;de La Fuente Marcos et al 2009;Moitinho et al 2006;Janes & Adler 1982), the only previous dedicated observations of NGC 2302 are those of Moffat & Vogt (1975), who obtained photoelectric U BVβ photometry of 16 stars in the cluster field. To the best of our knowledge, this is the first deep and comprehensive study of NGC 2302.…”

Section: Overviewmentioning

confidence: 99%

“…These are Blue Plume stars (Carraro et al 2005;Moitinho et al 2006), in this case located at approximately (m − M) = 10.96 (d = 7.50 kpc), tracing the outer arm.…”

Section: Photometric Diagramsmentioning

confidence: 99%

“…This small arm is often referred to as the Local (Orion) arm (hereafter LOA). This paradigm is illustrated well by the maps of A&A 580, A4 (2015) Even though as early as 1979 Moffat et al had suggested that the LOA enters the 3GQ, based on a study of early-type stars and HII regions, and that radio observations had supported this suggestion for long (Burton 1985, from HI;May et al 1988;and Murphy & May 1991, both from CO), only in the past few years has it been recognized as a well-confined elongated structure in the 3GQ, thanks to the optical/radio studies of Carraro et al (2005), Moitinho et al (2006), and Vázquez et al (2008;hereafter Vaz08). These later works, which are based on the optical multiband U BVRI photometry of young open clusters and field stars, complemented with a radio survey of molecular clouds observed in CO, have shed new light on the structure of the MW in the 3GQ.…”

Section: Introductionmentioning

confidence: 99%

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Insights into the properties of the Local (Orion) spiral arm. NGC 2302: First results and description of the program

Costa

Moitinho

Radiszc

et al. 2015

A&A

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Context. The spiral structure of the Milky Way (MW) is highly uncertain and is the subject of much discussion nowadays. Even the spiral structure close to the Sun and the real nature of the so-called Local or Orion arm are poorly known. Aims. We present the first result from a program that determines the properties of the Local (Orion) spiral arm (LOA), together with a full description of the program. In this context we have made a comprehensive study of the young LOA open cluster NGC 2302, which includes a U BVRI photometric analysis and determination of its kinematic properties -proper motion (PM) and radial velocity (RV) -and of its orbital parameters. Methods. Making a geometric registration of our ad-hoc first-and second-epoch CCD frames (12-year timeframe), we determined the mean PM of NGC 2302 relative to the local field of disk stars, and, through a comparison with the UCAC4 catalog, we transformed this relative PM into an absolute one. Using medium-resolution spectroscopy of 26 stars in the field of NGC 2302, we derived its mean RV. We determined the cluster's structure, center, and radius by means of a density analysis of star counts. Photometric diagrams for several color combinations were built using our data, which allowed us to identify the stellar populations present in the field of NGC 2302 and to carry out our photometric membership analysis. Isochrone fits to the photometric diagrams allowed us to determine the fundamental parameters of NGC 2302, including reddening, distance, and age. The kinematic data and derived distance allowed us to determine the space motion of NGC 2302. This was done by adopting a time-independent, axisymmetric, and fully analytic gravitational potential for the MW. Results. We obtained an absolute PM for NGC 2302 of (µ α cos δ, µ δ ) = (−2.09, −2.11) mas yr −1 , with standard errors of 0.410 and 0.400 mas yr −1 . The mean RV of NGC 2302 turned out to be 31.2 km s −1 with a standard error of 0.7 km s −1 . The density analysis revealed a remarkably spherical concentration of stars centered at α 2000 = 06:51:51.820, δ 2000 = −07:05:10.68 with a radius of 2.5 . Although densely contaminated by field stars, all our photometric diagrams show a recognizable cluster sequence of bright stars (V ≤ 18). The color-color diagrams show the existence of more than one population, each affected by distinct reddening with the cluster sequence at E(B − V) = 0.23. Isochrone fits displaced for this reddening and for a distance modulus of (m − M) 0 = 10.69 (distance, d = 1.40 kpc) indicate an age of log(t) = 7.90-8.00 with a slight tendency toward the younger age. Inspection of the shape of the orbit of NGC 2302 and the resulting orbital parameters indicate that it is a typical population I object.

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Spiral structure of the third galactic quadrant and the solution to the Canis Major debate

Cited by 98 publications

References 21 publications

The metallicity of the open cluster Tombaugh 2

The metallicity of the open cluster Tombaugh 2

Open clusters in the Third Galactic Quadrant III. Alleged binary clusters

Insights into the properties of the Local (Orion) spiral arm. NGC 2302: First results and description of the program

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