The Evolved Stellar Content of NGC 147, NGC 185, and NGC 205*

Davidge, T. J.

doi:10.1086/491706

Cited by 48 publications

(85 citation statements)

References 112 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In recent years, several authors have used near-IR photometry to select cool N-type C stars (Weinberg & Nikolaev 2001;Demers et al 2002;Cioni & Habing 2003;Kang et al 2006), essentially leading to (J − K) 0 > 1.4 (Davidge 2005) and (H − K) 0 > 0.45 (Hughes & Wood 1990) criteria. A critical analysis of these methods is given by Battinelli & Demers (2007).…”

Section: Star Candidate Selectionmentioning

confidence: 99%

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

Demers¹,

Battinelli²

2007

A&A

View full text Add to dashboard Cite

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...

show abstract

Section: Star Candidate Selectionmentioning

confidence: 99%

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

Demers¹,

Battinelli²

2007

A&A

View full text Add to dashboard Cite

show abstract

“…Therefore, tidal interactions with M 31 could have triggered the latest episodes of SF. Indeed, evidence of past dynamical interactions of NGC 205 with its bright companion has been accumulating over the years (McConnachie et al 2004;Geha et al 2006;De Rijcke et al 2006) and residual gas (Welch et al 1998) and dust (Marleau et al 2006) have also been detected in NGC 205 (see also Davidge 2005).…”

Section: Introductionmentioning

confidence: 98%

The young stellar population at the center of NGC 205

Monaco

Saviane

Perina

et al. 2009

A&A

View full text Add to dashboard Cite

Context. NGC 205 is a peculiar dwarf elliptical galaxy hosting in its center a population of young blue stars. Their origin is still matter of debate, the central fresh star formation activity possibly being related to dynamical interactions between NGC 205 and M 31. Aims. The star formation history in the central 30 (∼120 pc) around the NGC 205 central nucleus is investigated in order to obtain clues to the origin of the young stellar population. Methods. Deep HST/ACS CCD photometry is compared with theoretical isochrones and luminosity functions to characterize the stellar content of the region under study and compute the recent SF rate. Results. Our photometry reveals a previously undetected blue plume of young stars clearly distinguishable down to I 26. Our analysis suggests that 1.9 × 10 5 M were produced between approximately 62 Myr and 335 Myr ago in the NGC 205 inner regions, with a latest minor episode occurring ∼25 Myr ago. This implies a star formation rate of ∼7 × 10 −4 M /yr over this period. Conclusions. The excellent fit of the observed luminosity function of young main sequence stars obtained with a model having a constant star formation rate argues against a tidally triggered star formation activity over the last ∼300 Myr. Rather, a constant SF may be consistent with NGC 205 being on its first interaction with M 31.

show abstract

“…Mould et al 1983;Davidge 1994Davidge , 2005Lee et al 1993;Grebel 2000;McConnachie 2005;Butler & Martínez-Delgado 2005;Dolphin 2005). NGC 147 is composed of old (90%) and intermediate-age stellar populations (Mould et al 1983;Davidge 2005). The percentage of intermediate-age stellar populations is higher and the metallicities and metallicity spreads are greater in the other dEs.…”

Section: Introductionmentioning

confidence: 99%

Globular cluster content and evolutionary history of NGC 147

Шарина

Davoust

2009

A&A

View full text Add to dashboard Cite

Context. Globular clusters are representative of the oldest stellar populations. It is thus essential to have a complete census of these systems in dwarf galaxies, from which more massive galaxies are progressively formed in the hierarchical scenario. Aims. We present the results of spectroscopic observations of eight globular cluster candidates in NGC 147, a satellite dwarf elliptical galaxy of M 31. Our goal is to make a complete inventory of the globular cluster system of this galaxy, determine the properties of their stellar populations, and compare these properties with those of systems of globular clusters in other dwarf galaxies. Methods. The candidates were identified on Canada-France-Hawaii telescope photographic plates. Medium resolution spectra were obtained with the SCORPIO spectrograph at the prime focus of the 6 m telescope of the Russian Academy of Sciences. They were analyzed using predictions of stellar population synthesis models. Results. We were able to confirm the nature of all eight candidates, three of which (GC5, GC7, and GC10) are indeed globular clusters, and to estimate evolutionary parameters for the two brightest ones and for Hodge II. The bright clusters GC5 and GC7 appear to have metallicities ([Z/H] ∼ −1.5 ÷ −1.8) that are lower than the oldest stars in the galaxy. The fainter GC Hodge II has a metallicity [Z/H] = −1.1, similar to that of the oldest stars in the galaxy. The clusters GC5 and GC7 have low alpha-element abundance ratios. The mean age of the globular clusters in NGC 147 is 9 ± 1 Gyr. We also measured the radial velocities of Hodge II and IV, and derived a mass of NGC 147 in good agreement with the value from the literature. The frequency, S n = 6.4, and mass fraction, T = 14 of globular clusters in NGC 147 appear to be higher than those for NGC 185 and 205. Conclusions. Our results indicate that the bright clusters GC5, GC7, and Hodge III formed in the main star-forming period ∼8−10 Gyr ago, while the fainter clusters Hodge I and II formed together with the second generation of field stars.

show abstract

The Evolved Stellar Content of NGC 147, NGC 185, and NGC 205*

Cited by 48 publications

References 112 publications

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

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

The young stellar population at the center of NGC 205

Globular cluster content and evolutionary history of NGC 147

Contact Info

Product

Resources

About