Color and Metallicity Distributions of M81 Globular Clusters

Ma, Jun; Zhou, Xu; Chen, Jiansheng; Wu, Zhenyu; Yang, Yanbin; Jiang, Zhaoji; Wu, Jianghua

doi:10.1086/428276

Cited by 11 publications

(26 citation statements)

References 22 publications

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“…It has an intermediate age and a metallicity [Z/H]= ‐ 0.8 ± 0.3, but the S/N in the spectrum is quite low and the errors of evolutionary parameters determination are large. KDG63‐3‐1168 appear to be younger and richer in metals compared to the many old clusters found in M81 (Georgiev, Tikhonov & Karachentsev 1991b; Georgiev et al 1991c; Schroder et al 2002; Chandar, Whitmore & Lee 2004; Ma et al 2005, 2006, 2007). Note that the mean metallicity of the GC is consistent with the mean metallicity of red giant stars in DDO71 ([Fe/H]=−1.17; Sharina et al 2008).…”

Section: Resultsmentioning

confidence: 89%

SAO RAS 6-m telescope spectroscopic observations of globular clusters in nearby galaxies

Шарина

Chandar

Puzia

et al. 2010

Monthly Notices of the Royal Astronomical Society

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We present the results of medium‐resolution spectroscopy of 28 globular clusters (GCs) in six nearby galaxies of different luminosities and morphological types, situated in M33 (15 objects), M31 (three), IC10 (four), UGCA86 (four), Holmberg IX (one) and DDO71 (one) obtained at the Special Astrophysical Observatory 6‐m telescope. Measurements of Lick absorption line indices and comparison with Simple Stellar Population models enabled us to obtain their spectroscopic ages, metallicities and α‐element to Fe abundance ratios. We found that all old‐ and intermediate‐age GCs in our sample have low metallicities [Z/H]≲ ‐0. 8 dex. Metal‐rich clusters are young and are preferentially found in galaxies more massive than ∼ 109 M⊙. The least massive dwarfs of our sample, DDO71 and Holmberg IX, host one massive intermediate‐age and one massive young metal‐poor GC, respectively. [α/Fe] abundance ratios tend to be enhanced but closer to solar values for dwarf galaxies compared to GCs in more massive galaxies. We analyse the age–metallicity relation for GCs in our sample and others from the literature, and find that (1) there is a general trend for GCs in low surface brightness dwarf galaxies to be more metal‐poor at a given age than GCs in more massive galaxies; (2) the GC metallicity spread is wider for more massive galaxies and (3) intermediate‐age GCs in early‐type dwarf galaxies are more metal‐rich at any given age than those in irregular galaxies of similar luminosity.

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Section: Resultsmentioning

confidence: 89%

SAO RAS 6-m telescope spectroscopic observations of globular clusters in nearby galaxies

Шарина

Chandar

Puzia

et al. 2010

Monthly Notices of the Royal Astronomical Society

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“…Several tools are available to understand the chemical evolution of the M 81 disk: star clusters (Ma et al 2005;Nantais et al 2011), young supergiant stars (Davidge 2006), X-ray sources (Sell et al 2011), and color−magnitude diagrams fitting the HST-resolved stellar population (Kudritzki et al 2012). Nonetheless, emission-line targets such as HII regions and PNe have advantages over their stellar counterparts since PN and HII region spectra are analyzed in similar ways, making the comparison of the two sets of probes more direct than when comparing sources of different natures.…”

Section: Introductionmentioning

confidence: 99%

The radial metallicity gradient and the history of elemental enrichment in M 81 through emission-line probes

Stanghellini

Magrini

Casasola

et al. 2014

A&A

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Aims. We present a new set of weak-line abundances of HII regions in M 81, which are based on Gemini Multi-Object Spectrograph (GMOS) observations. The aim is to derive plasma and abundance analysis for a sizable set of emission-line targets to study the galactic chemical contents in the framework of galactic metallicity gradients. Methods. We used the weak-line abundance approach by deriving electron density and temperatures for several HII regions in M 81. Our gradient analysis is based on oxygen abundances. Results. Together with a set of HII region abundances determined similarly by us with Multi-Mirror Telescope (MMT) spectra, the new data yield a radial oxygen gradient of −0.088 ± 0.013 dex kpc −1 , which is steeper than the metallicity gradient obtained for planetary nebulae (−0.044 ± 0.007 dex kpc −1 ). This result could be interpreted as gradient evolution with time: Models of galactic evolution with inside-out disk formation associated to pre-enriched gas infall would produce such a difference in gradients, although stellar migration effects would also induce a difference in the metallicity gradients between the old and young populations. Conclusions. By comparing the M 81 metallicity gradients with those of other spiral galaxies, which were all consistently derived from weak-line analysis, we can infer that a similar gradient difference is common among spirals. The metallicity gradient slopes for HII regions and PNe seem to be steeper in M 81 than in other galactic disks, which is probably because M 81 belongs to a galaxy group. We also found that M 81 has experienced an average oxygen enrichment of 0.14 ± 0.08 dex in the spatial domain defined by the observations. Our data are compatible with a break in the radial oxygen gradient slope around R 25 as inferred by other authors both in M 81 and in other galaxies.

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“…The bimodal test results in the two group: the metal-poor with a mean value of −1.47 and the metal-rich with a mean value of −0.62 (see also Barmby et al, 2000;Perrett et al, 2002;Fan et al, 2008). Ma et al (2005) presented a metallicity distribution of 94 M81 GCs being bimodal, with metallicity peaks at −1.45 and −0.53.…”

Section: Jun Mamentioning

confidence: 95%

“…Based on the estimated intrinsic colors, Chandar et al (2004) found that the M81 GC system has an extended metallicity distribution, which argues the presence of both metal-rich and metal-poor GCs. Ma et al (2005Ma et al ( , 2006Ma et al ( , 2007 presented detailed studies on M81 GCs based on the spectral and multicolor observations such as: the distributions of intrinsic B and V colors and metallicities of 95 GCs; the spectral energy distributions of 42 GCs in 13 intermediate-band filters from 4000 to 10,000 Å, using the CCD images of M81 observed as part of the Beijing-Arizona-Taiwan-Connecticut (BATC) multicolor survey of the sky; the spatial and metal abundance properties of 95 GCs. Nantais et al (2010b) presented a catalog of extended objects in and around M81 based on an HST ACS I-band mosaic, and found 233 good GC candidates.…”

Section: Jun Mamentioning

confidence: 99%

“…Altogether, there are 107 GCs in the Nantais & Huchra (2010) sample of M81 GCs for performing metallicity analysis. Ma et al (2005) studied the distributions of metallicities of 95 M81 GCs which are from , Chandar et al (2001) and Schroder et al (2002). By cross-checking the sample GCs of between Ma et al (2005) and Nantais & Huchra (2010), there are 51 GCs in common.…”

Section: A Sample Of Gcsmentioning

confidence: 99%

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Metal abundance and kinematical properties of the M81 globular cluster system

Ma¹,

Wu²,

Zhang³

et al. 2013

Res. Astron. Astrophys.

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In this paper, we presented metal abundance properties of 144 M81 globular clusters. These globulars consist of the largest globular cluster sample in M81 till now. Our main results are: the distribution of metallicities are bimodal, with metallicity peaks at [Fe/H] ≈ −1.51 and −0.58, and the metal-poor globular clusters tend to be less spatially concentrated than the metal-rich ones; the metal-rich globular clusters in M81 do not demonstrate a centrally concentrated spatial distribution as the metal-rich ones in M31 do; like our Galaxy and M31, the globular clusters in M81 have a small radial metallicity gradient. These results are consistent with those obtained based on a small sample of M81 globular clusters. In addition, this paper showed that there is evidence that a strong rotation of the M81 globular cluster system around the minor axis exists, and that rotation is present in the metal-rich globular cluster subsample, while the metal-poor globular cluster subsample shows no evidence for rotation. The most significant difference between the rotation of the metal-rich and metal-poor globular clusters occurs at intermediate projected galactocentric radii. The results of this paper confirm the conclusion of Schroder et al. that M81's metal-rich globular clusters at intermediate projected radii were associated with a thick disk of M81.

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Color and Metallicity Distributions of M81 Globular Clusters

Cited by 11 publications

References 22 publications

SAO RAS 6-m telescope spectroscopic observations of globular clusters in nearby galaxies

SAO RAS 6-m telescope spectroscopic observations of globular clusters in nearby galaxies

The radial metallicity gradient and the history of elemental enrichment in M 81 through emission-line probes

Metal abundance and kinematical properties of the M81 globular cluster system

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