Spectral Energy Distributions and Age Estimates of 104 M31 Globular Clusters

Wang, Song; Zhang, Fan; Ma, Jun; Grijs, Richard de; Zhou, Xu

doi:10.1088/0004-6256/139/4/1438

Cited by 40 publications

(89 citation statements)

References 64 publications

(148 reference statements)

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“…It seems that many GC candidates in M31 are located out of the evolutionary tracks. The majority of M31 GCs fall between these four fading lines, consistent with previous results (Wang et al 2010). The horizontal dashed line represents V − K s = 3, assuming the reddening value E(B − V) = 0.13.…”

Section: Luminosity Functionsupporting

confidence: 92%

New 2mass Near-Infrared Photometry for Globular Clusters in M31

Wang

et al. 2014

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We present 2MASS JHK s photometry for 913 star clusters and candidates in the field of M31, which are selected from the latest Revised Bologna Catalog of M31 globular clusters (GCs) and candidates. The photometric measurements in this paper supplement this catalog, and provide a most comprehensive and homogeneous photometric catalog for M31 GCs in the JHK s bandpasses. In general, our photometry is consistent with previous measurements. The globular cluster luminosity function (GCLF) peaks for the confirmed GCs derived by fitting a t 5 distribution using maximum likelihood method are: J 0 = 15.348 +0.206 −0.208 , H 0 = 14.703 +0.176 −0.180 , and K s0 = 14.534 +0.142 −0.146 , all of which agree well with previous studies. The GCLFs are different between metalrich (MR) and metal-poor (MP), inner and outer subpopulations, as that MP clusters are fainter than their MR counterparts, and the inner clusters are brighter than the outer ones, which confirm previous results. The NIR colors of the GC candidates are on average redder than those of the confirmed GCs, which lead to an obscure bimodal distribution of the color indices. The relation of (V − K s ) 0 and metallicity shows a notable departure from linearity, with a shallower slope towards the redder end. The color-magnitude diagram (CMD) and colorcolor diagram show that many GC candidates are located out of the evolutionary tracks, suggesting that some of them may be false M31 GC candidates. The CMD also shows that the initial mass function of M31 GCs covers a large range, and the majority of the clusters have initial masses between 10 3 and 10 6 M ⊙ .

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Section: Luminosity Functionsupporting

confidence: 92%

New 2mass Near-Infrared Photometry for Globular Clusters in M31

Wang

et al. 2014

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“…The main source of the discrepancy is that many of the clusters identified by the cited papers as being young are in fact old and metal-poor. Of the 77 clusters in common with Wang et al (2010), 50 clusters stated to be younger than 5 Gyr are older than 10 Gyr based on our analysis. Returning to our own age determinations, we note again that from the EZ_Ages analysis, some clusters marked as old in Paper I were realized to be younger than 2 Gyr after publication of that paper.…”

Section: Discussion Of Agesmentioning

confidence: 73%

Star Clusters in M31. Ii. Old Cluster Metallicities and Ages From Hectospec Data

Caldwell

Schiavon

Morrison

et al. 2011

The Astronomical Journal

168

400

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We present new high signal-to-noise spectroscopic data on the M31 globular cluster (GC) system, obtained with the Hectospec multifiber spectrograph on the 6.5 m MMT. More than 300 clusters have been observed at a resolution of 5 Å and with a median S/N of 75 per Å, providing velocities with a median uncertainty of 6 km s −1 . The primary focus of this paper is the determination of mean cluster metallicities, ages, and reddenings. Metallicities were estimated using a calibration of Lick indices with [Fe/H] provided by Galactic GCs. These match well the metallicities of 24 M31 clusters determined from Hubble Space Telescope color-magnitude diagrams, the differences having an rms of 0.2 dex. The metallicity distribution is not generally bimodal, in strong distinction with the bimodal Galactic globular distribution. Rather, the M31 distribution shows a broad peak, centered at [Fe/H] = −1, possibly with minor peaks at [Fe/H] = −1.4, −0.7, and −0.2, suggesting that the cluster systems of M31 and the Milky Way had different formation histories. Ages for clusters with [Fe/H] > −1 were determined using the automatic stellar population analysis program EZ_Ages. We find no evidence for massive clusters in M31 with intermediate ages, those between 2 and 6 Gyr. Moreover, we find that the mean ages of the old GCs are remarkably constant over about a decade in metallicity (−0.95 [Fe/H] 0.0).

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“…2 The blue line shows the cosmic age in the R h = ct using the best-fit value from SNe Ia and the Hubble parameter, the red lines are for the 1σ deviation. The red circles are the nine extremely old GCs and this also gives the error of their age B050 measured by [24,25] are higher than those of [48]. The values are significantly different.…”

Section: Constraining the R H = Ct Universe With Sne Ia And H (Z) Datamentioning

confidence: 94%

“…The R h = ct universe can fit the SNe Ia data well [29], explain the growth of highz quasars [30], and account for the apparent absence in the CMB angular correlation [31]. As we discussed above, many 14.54 ± 0.55 [25] cosmological models cannot pass the age test. But whether the R h = ct universe suffers from the cosmic age problem is still unknown.…”

Section: Introductionmentioning

confidence: 93%

“…In this paper, we will use the old quasar APM 08279+5255 at redshift z = 3.91 and the nine extremely old Global Clusters [24,25] to investigate the cosmic age problem in the R h = ct universe. The data of these nine extremely old GCs listed in Table 1 are acquired from the Beijing-ArizonaTaiwan-Connecticut system with up-to-date theoretical synthesis models.…”

Section: Introductionmentioning

confidence: 99%

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Reconciling the cosmic age problem in the $$R_\mathrm{h}=ct$$ R h = c t universe

Wang

2014

Eur. Phys. J. C

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Many dark energy models fail to pass the cosmic age test. In this paper, we investigate the cosmic age problem associated with nine extremely old Global Clusters (GCs) and the old quasar APM 08279+5255 in the R h = ct universe. The age data of these oldest GCs in M31 are acquired from the Beijing-Arizona-Taiwan-Connecticut system with up-to-date theoretical synthesis models. They have not been used to test the cosmic age problem in the R h = ct universe in previous literature. By evaluating the age of the R h = ct universe with the observational constraints from the type Ia supernovae and the Hubble parameter, we find that the R h = ct universe can accommodate five GCs and the quasar APM 08279+5255 at redshift z = 3.91. But for other models, such as CDM, the interacting dark energy model, the generalized Chaplygin gas model, and holographic dark energy model, cannot accommodate all GCs and the quasar APM 08279+5255. It is worthwhile to note that the age estimates of some GCs are controversial. So, unlike other cosmological models, the R h = ct universe can marginally solve the cosmic age problem, especially at high redshift.

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Spectral Energy Distributions and Age Estimates of 104 M31 Globular Clusters

Cited by 40 publications

References 64 publications

New 2mass Near-Infrared Photometry for Globular Clusters in M31

New 2mass Near-Infrared Photometry for Globular Clusters in M31

Star Clusters in M31. Ii. Old Cluster Metallicities and Ages From Hectospec Data

Reconciling the cosmic age problem in the $$R_\mathrm{h}=ct$$ R h = c t universe

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