Age Constraints for an M31 Globular Cluster from SEDs Fit

Ma, Jun; Yang, Yanbin; Burstein, David; Zhang, Fan; Wu, Zhenyu; Zhou, Xu; Wu, Jianghua; Jiang, Zhaoji; Chen, Jiansheng

doi:10.1086/511850

Cited by 26 publications

(61 citation statements)

References 39 publications

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“…Those relying on photometry (e.g. Fan et al 2006) are more susceptible to the age-metallicity degeneracy in the sense that young metal-rich populations are photometrically indistinguishable from older metal-poor populations (but see, e.g., Ma et al 2007). The different spectroscopic methods, however, are inspired by the Lick/IDS system of absorption line indices (e.g.…”

Section: Introductionmentioning

confidence: 99%

Full spectral fitting of Milky Way and M 31 globular clusters: ages and metallicities

Cezario

Coelho

Alves-Brito

et al. 2012

A&A

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Context. The formation and evolution of disk galaxies are long standing questions in astronomy. Understanding the properties of globular cluster systems can lead to important insights on the evolution of its host galaxy. Aims. We aim to obtain the stellar population parameters -age and metallicity -of a sample of M 31 and Galactic globular clusters. Studying their globular cluster systems is an important step towards understanding their formation and evolution in a complete way. Methods. Our analysis employs a modern pixel-to-pixel spectral fitting technique to fit observed integrated spectra to updated stellar population models. By comparing observations to models we obtain the ages and metallicities of their stellar populations. We apply this technique to a sample of 38 globular clusters in M 31 and to 41 Galactic globular clusters, used as a control sample. Results. Our sample of M 31 globular clusters spans ages from 150 Myr to the age of the Universe. Metallicities [Fe/H] range from -2.2 dex to the solar value. The age-metallicity relation obtained can be described as having two components: an old population with a flat age-[Fe/H] relation, possibly associated with the halo and/or bulge, and a second one with a roughly linear relation between age and metallicity, higher metallicities corresponding to younger ages, possibly associated with the M 31 disk. While we recover the very well known Galactic GC metallicity bimodality, our own analysis of M 31's metallicity distribution function (MDF) suggests that both GC systems cover basically the same [Fe/H] range yet M 31's MDF is not clearly bimodal. These results suggest that both galaxies experienced different star formation and accretion histories.

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Section: Introductionmentioning

confidence: 99%

Full spectral fitting of Milky Way and M 31 globular clusters: ages and metallicities

Cezario

Coelho

Alves-Brito

et al. 2012

A&A

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“…Another widely used method to age-date extragalactic star clusters relies on multi-band photometry: the age can be derived from the spectral energy distributions (SED) measured in broad-band photometric systems, by comparing them with simple stellar population (SSP 3 ) synthesis models (e.g. Jiang et al 2003;Fan et al 2006Fan et al , 2008Fan et al , 2010Ma et al 2007Ma et al , 2009. Clearly, photometrybased technique are prone to errors owing to the uncertainty in the interstellar extinction, while spectral indices are virtually free from this effect.…”

Section: Introductionmentioning

confidence: 99%

HST/ACS color-magnitude diagrams of candidate intermediate-age M 31 globular clusters

Perina¹,

Galleti²,

Pecci³

et al. 2011

A&A

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We present deep (V 28.0) BV photometry obtained with the wide field channel of the Advanced Camera for Surveys on board HST for four M 31 globular clusters that were identified as candidate intermediate-age (age ∼ 1−9 Gyr) by various authors, based on their integrated spectra and/or broad/intermediate-band colors. Two of them (B292 and B350) display an obvious blue horizontal branch, indicating that they are as old as the oldest Galactic globulars. On the other hand, for the other two (B058 and B337), which display red horizontal branches, it was not possible either to confirm or disconfirm the age estimate from integrated spectra. The analysis of the distribution in the spectral indices Mg2 and Hβ of the M 31 and Milky Way clusters whose horizontal branch can be classified as red or blue based on existing CMDs, strongly suggests that classical age diagnostics from integrated spectra may be significantly influenced by the HB morphology of the clusters and can lead to erroneous age-classifications. We also provide the CMD for another two clusters that fall into the field of the main targets, B336, an old and metal-poor globular with a significant population of RR Lyrae variables, and the newly discovered B531, a cluster with a very red red giant branch.

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“…For those photometric errors which can not be found in the literature works, we adopted a mean photometric errors depending on the brightness of the sources. The model errors adopted were 0.05 mag, which is the typical photometric error for the Bruzual & Charlot (2003) and galev SSP models (e.g., Fan et al 2006;Ma et al 2007Ma et al , 2009Wang et al 2010;Fan & de Grijs 2014).…”

Section: The Models and χ 2 Min -Fitting Methodsmentioning

confidence: 99%

The effects of the WISE/GALEX photometry for the SED-fitting with M31 star clusters and candidates

Zhang¹,

Wang²

2017

Astrophys Space Sci

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Spectral energy distribution (SED) fitting of stellar population synthesis models is an important and popular way to constrain the physical parameters -e.g., the ages, metallicities, masses for stellar population analysis. The previous works suggest that both blue-bands and red-bands photometry works for the SEDfitting. Either blue-domained or red-domained SED-fitting usually lead to the unreliable or biased results. Meanwhile, it seems that extending the wavelength coverage could be helpful. Since the Galaxy Evolution Explorer (GALEX) and Wide-field Infrared Survey Explorer (WISE) provide the FUV/NUV and midinfrared W 1/W 2 band data, we extend the SED-fitting to a wider wavelength coverage. In our work, we analyzed the effect of adding the FUV/NUV and W 1/W 2 band to the optical and near-infrared UBV RIJHK bands for the fitting with the Bruzual & Charlot 2003 (BC03) models and galev models. It is found that the FUV/NUV bands data affect the fitting results of both ages and metallicities much more significantly than that of the WISE W 1/W 2 band with the BC03 models. While for the galev models, the effect of the WISE W 1/W 2 band for the metallicity fitting seems comparable to that of GALEX FUV/NUV bands, but for age the effect of the W 1/W 2 band seems less crucial than that of the FUV/NUV bands. Thus we conclude that the GALEX FUV/NUV bands are more crucial for the SED-fitting of ages and metallicities, than the other bands, and the high-quality UV data (with high photometry precision) are required.

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Age Constraints for an M31 Globular Cluster from SEDs Fit

Cited by 26 publications

References 39 publications

Full spectral fitting of Milky Way and M 31 globular clusters: ages and metallicities

Full spectral fitting of Milky Way and M 31 globular clusters: ages and metallicities

HST/ACS color-magnitude diagrams of candidate intermediate-age M 31 globular clusters

The effects of the WISE/GALEX photometry for the SED-fitting with M31 star clusters and candidates

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