Synthetic photometry of globular clusters: Uncertainties on synthetic colors
arXiv:1805.11997 · doi:10.1051/0004-6361/201833083
Abstract
Synthetic photometry is a great tool for studying globular clusters, especially for understanding the nature of their multiple populations. Our goal is to quantify the errors on synthetic photometry that are caused by uncertainties on stellar and observational/calibration parameters. These errors can be taken into account when building synthetic color-magnitude diagrams (CMDs) that are to be compared to observed CMDs. We have computed atmosphere models and synthetic spectra for two stars, Pollux and Procyon, that have stellar parameters typical of turn-off and bottom red giant branch stars in globular clusters. We then varied the effective temperature, surface gravity, microturbulence, the carbon, nitrogen, and oxygen abundances, and [Fe/H]. We quantified the effect on synthetic photometry in the following filters: Johnson UBVRI and HST F275W, F336W, F410M, F438W, F555W, F606W, and F814W. We estimated the effects of extinction, atmospheric correction, and of the Vega reference spectrum on the resulting photometry. We tested the ability of our models to reproduce the observed spectral energy distribution and observed photometry of the two stars. We show that variations are generally stronger in blue filters. Dispersions on synthetic colors due to uncertainties on stellar parameters vary between less than 0.01 and to 0.04 magnitude, depending on the choice of filters. Uncertainties on the zero points, the extinction law, or the atmospheric correction affect the resulting colors at a level of a few 0.01 magnitudes in a systematic way. The models reproduce the flux-calibrated spectral energy distribution of both stars well. Comparison between synthetic and observed UBVRI photometry shows a variable degree of (dis)agreement. The observed differences likely indicate that different calibration processes are performed to obtain respectively observed and synthetic photometry.
arXiv comment10 pages, 9 figures. Accepted in Astronomy and Astrophysics
References in corpus (52)
- Na-O Anticorrelation and HB. VII. The chemical composition of first and second-generation stars in 15 globular clusters from GIRAFFE spectra
- Fast rotating massive stars and the origin of the abundance patterns in galactic globular clusters
- A Triple Main Sequence in the Globular Cluster NGC 2808
- Intrinsic iron spread and a new metallicity scale for Globular Clusters
- Omega Centauri: The Population Puzzle Goes Deeper
- The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. I. Overview of the Project and Detection of Multiple Stellar Populations
- The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. IX. The Atlas of Multiple Stellar Populations
- A database of high and medium-resolution stellar spectra
- Predictions for self-pollution in globular cluster stars
- NLTE line formation of Fe in late-type stars II: 1D spectroscopic stellar parameters
- Gaia FGK Benchmark Stars: Effective temperatures and surface gravities
- Super-Massive Stars as a Source of Abundance Anomalies of Proton-Capture Elements in Globular Clusters
- Yields of AGB and SAGB models with chemistry of low- and high-metallicity Globular Clusters
- Multiple stellar populations in 47 Tucanae
- Detailed abundances of a large sample of giant stars in M 54 and in the Sagittarius nucleus
- Concurrent formation of supermassive stars and globular clusters: implications for early self-enrichment
- Photometric signatures of multiple stellar populations in Galactic globular clusters
- Transforming observational data and theoretical isochrones into the ACS/WFC Vega-mag system
- A WFC3/HST view of the three stellar populations in the Globular Cluster NGC6752
- Na-O Anticorrelation And HB I. The Na-O anticorrelation in NGC 2808
- Abundances of C, N, O in slightly evolved stars in the globular clusters NGC 6397, NGC 6752 and 47 Tuc
- Gaia FGK benchmark stars: abundances of alpha and iron-peak elements
- Abundances in giant stars of the globular cluster NGC 6752
- Sodium-oxygen anticorrelation and neutron capture elements in Omega Centauri stellar populations
- Helium enhanced stars and multiple populations along the horizontal branch of NGC2808: direct spectroscopic measurements
- Light nuclei in galactic globular clusters : constraints on the self-enrichment scenario from nucleosynthesis
- Nitrogen abundances in giant stars of the globular cluster NGC 6752
- Stellar parameters and chemical abundances of 223 evolved stars with and without planets
- Five groups of red giants with distinct chemical composition in the globular cluster NGC 2808
- Multiple stellar populations in the Galactic globular cluster NGC 6752
- The Magnetic Fields at the Surface of Active Single G-K Giants
- The Helium content of Globular Clusters: light element abundance correlations and HB morphology. I. NGC6752
- The Presence of Two Distinct Red Giant Branches in the Globular Cluster NGC 1851
- Na-O Anticorrelation and HB. II. The Na-O anticorrelation in the globular cluster NGC 6752
- Na-O Anticorrelation and Horizontal Branches. V. The Na-O anticorrelation in NGC 6441 from Giraffe spectra
- CNO abundances in the globular clusters NGC 1851 and NGC 6752
- Chemical tagging of three distinct populations of red giants in the globular cluster NGC 6752
- Unveiling systematic biases in 1D LTE excitation-ionisation balance of Fe for FGK stars. A novel approach to determination of stellar parameters
- Abundances in the Local Region I: G and K Giants
- Mg isotope ratios in giant stars of the globular clusters M 13 and M 71
- Revisiting nucleosynthesis in globular clusters: the case of NGC 2808 and the role of He and K
- A grid of NLTE corrections for magnesium and calcium in late-type giant and supergiant stars: application to Gaia
- Stellar Models of Multiple Populations in Globular Clusters. I. The Main Sequence of NGC 6752
- Evolution of long-lived globular cluster stars III. Effect of the initial helium spread on the position of stars in a synthetic Hertzsprung-Russell diagram
- The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. VIII. Preliminary Public Catalog Release
- The fraction of first and second generation stars in globular clusters. I The case of NGC 6752
- The Potassium abundance in the globular clusters NGC104, NGC6752 and NGC6809
- Why the globular cluster NGC 6752 contains no sodium-rich second-generation AGB star
- Lost and found: evidence of Second Generation stars along the Asymptotic Giant Branch of the globular cluster NGC 6752
- Atmospheric composition of weak G band stars: CNO and Li abundances
- On the determination of the He abundance distribution in globular clusters from the width of the main sequence
- First evidence of multiple populations along the AGB from Strömgren photometry