Isochrone fitting of Galactic globular clusters -- V. NGC6397 and NGC6809 (M55)
Fuente:
arXiv
Salvato in:
| Autori principali: | , , , , , , , , , , |
|---|---|
| Natura: | Preprint |
| Pubblicazione: |
2024
|
| Soggetti: | |
| Accesso online: | |
| Tags: |
Aggiungi Tag
Nessun Tag, puoi essere il primo ad aggiungerne!!
|
| _version_ | 1866914672552181760 |
|---|---|
| author | Gontcharov, George A. Bonatto, Charles J. Ryutina, Olga S. Savchenko, Sergey S. Mosenkov, Aleksandr V. Il'in, Vladimir B. Khovritchev, Maxim Yu. Marchuk, Alexander A. Poliakov, Denis M. Smirnov, Anton A. Seguine, Jonah |
| author_facet | Gontcharov, George A. Bonatto, Charles J. Ryutina, Olga S. Savchenko, Sergey S. Mosenkov, Aleksandr V. Il'in, Vladimir B. Khovritchev, Maxim Yu. Marchuk, Alexander A. Poliakov, Denis M. Smirnov, Anton A. Seguine, Jonah |
| contents | We fit various colour-magnitude diagrams (CMDs) of the Galactic globular clusters NGC\,6397 and NGC\,6809 (M55) by isochrones from the Dartmouth Stellar Evolution Database (DSED) and Bag of Stellar Tracks and Isochrones (BaSTI) for $α$-enhanced [$α$/Fe]$=+0.4$. For the CMDs, we use data sets from {\it HST}, {\it Gaia}, VISTA, and other sources utilizing 32 and 23 photometric filters for NGC\,6397 and NGC\,6809, respectively, from the ultraviolet to mid-infrared. We obtain the following characteristics for NGC\,6397 and NGC\,6809, respectively: metallicities [Fe/H]$=-1.84\pm0.02\pm0.1$ and $-1.78\pm0.02\pm0.1$ (statistic and systematic uncertainties); distances $2.45\pm0.02\pm0.06$ and $5.24\pm0.02\pm0.18$ kpc; ages $12.9\pm0.1\pm0.8$ and $13.0\pm0.1\pm0.8$ Gyr; reddenings $E(B-V)=0.178\pm0.006\pm0.01$ and $0.118\pm0.004\pm0.01$ mag; extinctions $A_\mathrm{V}=0.59\pm0.01\pm0.02$ and $0.37\pm0.01\pm0.04$ mag; extinction-to-reddening ratio $R_\mathrm{V}=3.32^{+0.32}_{-0.28}$ and $3.16^{+0.66}_{-0.56}$. Our estimates agree with most estimates from the literature. BaSTI gives systematically higher [Fe/H] and lower reddenings than DSED. Despite nearly the same metallicity, age, and helium enrichment, these clusters show a considerable horizontal branch (HB) morphology difference, which must therefore be described by another parameter. This parameter must predominantly explain why the least massive HB stars (0.58-0.63 solar masses) are only found within NGC 6809. Probably they have been lost by the core-collapse cluster NGC\,6397 during its dynamical evolution and mass segregation. In contrast, NGC\,6809 has a very low central concentration and, hence, did not undergo this process. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2402_06524 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Isochrone fitting of Galactic globular clusters -- V. NGC6397 and NGC6809 (M55) Gontcharov, George A. Bonatto, Charles J. Ryutina, Olga S. Savchenko, Sergey S. Mosenkov, Aleksandr V. Il'in, Vladimir B. Khovritchev, Maxim Yu. Marchuk, Alexander A. Poliakov, Denis M. Smirnov, Anton A. Seguine, Jonah Astrophysics of Galaxies Solar and Stellar Astrophysics We fit various colour-magnitude diagrams (CMDs) of the Galactic globular clusters NGC\,6397 and NGC\,6809 (M55) by isochrones from the Dartmouth Stellar Evolution Database (DSED) and Bag of Stellar Tracks and Isochrones (BaSTI) for $α$-enhanced [$α$/Fe]$=+0.4$. For the CMDs, we use data sets from {\it HST}, {\it Gaia}, VISTA, and other sources utilizing 32 and 23 photometric filters for NGC\,6397 and NGC\,6809, respectively, from the ultraviolet to mid-infrared. We obtain the following characteristics for NGC\,6397 and NGC\,6809, respectively: metallicities [Fe/H]$=-1.84\pm0.02\pm0.1$ and $-1.78\pm0.02\pm0.1$ (statistic and systematic uncertainties); distances $2.45\pm0.02\pm0.06$ and $5.24\pm0.02\pm0.18$ kpc; ages $12.9\pm0.1\pm0.8$ and $13.0\pm0.1\pm0.8$ Gyr; reddenings $E(B-V)=0.178\pm0.006\pm0.01$ and $0.118\pm0.004\pm0.01$ mag; extinctions $A_\mathrm{V}=0.59\pm0.01\pm0.02$ and $0.37\pm0.01\pm0.04$ mag; extinction-to-reddening ratio $R_\mathrm{V}=3.32^{+0.32}_{-0.28}$ and $3.16^{+0.66}_{-0.56}$. Our estimates agree with most estimates from the literature. BaSTI gives systematically higher [Fe/H] and lower reddenings than DSED. Despite nearly the same metallicity, age, and helium enrichment, these clusters show a considerable horizontal branch (HB) morphology difference, which must therefore be described by another parameter. This parameter must predominantly explain why the least massive HB stars (0.58-0.63 solar masses) are only found within NGC 6809. Probably they have been lost by the core-collapse cluster NGC\,6397 during its dynamical evolution and mass segregation. In contrast, NGC\,6809 has a very low central concentration and, hence, did not undergo this process. |
| title | Isochrone fitting of Galactic globular clusters -- V. NGC6397 and NGC6809 (M55) |
| topic | Astrophysics of Galaxies Solar and Stellar Astrophysics |
| url | https://arxiv.org/abs/2402.06524 |