SIMBAD references

2007ApJ...670..400C - Astrophys. J., 670, 400-422 (2007/November-3)

Stromgren photometry of Galactic globular clusters. I. New calibrations of the metallicity index.

CALAMIDA A., BONO G., STETSON P.B., FREYHAMMER L.M., CASSISI S., GRUNDAHL F., PIETRINFERNI A., HILKER M., PRIMAS F., RICHTLER T., ROMANIELLO M., BUONANNO R., CAPUTO F., CASTELLANI M., CORSI C.E., FERRARO I., IANNICOLA G. and PULONE L.

Abstract (from CDS):

We present a new calibration of the Strömgren metallicity index m1 using red giant (RG) stars in four globular clusters (GCs: M92, M13, NGC 1851, 47 Tuc) with metallicity ranging from -2.2 to -0.7, marginally affected by reddening [E(B-V)≤0.04] and with accurate (u,v,b,y) photometry. The main difference between the new metallicity-index-color (MIC) relations and similar relations available in the literature is that we have adopted the u-y and v-y colors instead of b-y. These colors present a stronger sensitivity to effective temperature, and the MIC relations show a linear slope. The difference between photometric estimates and spectroscopic measurements for RGs in M71, NGC 288, NGC 362, NGC 6397, and NGC 6752 is 0.04±0.03 dex (σ=0.11 dex). We also apply the new MIC relations to 85 field RGs with metallicity ranging from -2.4 to -0.5 and accurate reddening estimates. We find that the difference between photometric estimates and spectroscopic measurements is -0.14±0.01 dex (σ=0.17 dex). We also provide two sets of MIC relations based on evolutionary models that have been transformed into the observational plane by adopting either semiempirical or theoretical color-temperature relations. We apply the semiempirical relations to the nine GCs and find that the difference between photometric and spectroscopic metallicities is 0.04±0.03 dex (σ=0.10 dex). A similar agreement is found for the sample of field RGs, with a difference of -0.09±0.03 dex (with σ=0.19 dex). The difference between metallicity estimates based on theoretical relations and spectroscopic measurements is -0.11±0.03 dex (σ=0.14 dex) for the nine GCs and -0.24±0.03 dex (σ=0.15 dex) for the field RGs. Current evidence indicates that new MIC relations provide metallicities with an intrinsic accuracy better than 0.2 dex.

Abstract Copyright:

Journal keyword(s): Galaxy: Globular Clusters: General - Galaxy: Globular Clusters: Individual: Messier Number: M13 - Galaxy: Globular Clusters: Individual: Messier Number: M71 - Galaxy: Globular Clusters: Individual: Messier Number: M92 - Galaxy: Globular Clusters: Individual: NGC Number: NGC 288 - Galaxy: Globular Clusters: Individual: NGC Number: NGC 362 - Galaxy: Globular Clusters: Individual: NGC Number: NGC 1851 - Galaxy: Globular Clusters: Individual: NGC Number: NGC 6397 - Galaxy: Globular Clusters: Individual: NGC Number: NGC 6752 - Galaxy: Globular Clusters: Individual: Name: 47 Tucanae - Stars: Abundances - Stars: Evolution

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2019.10.18-19:47:40

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