GlObular clusTer Homogeneous Abundances Measurements (GOTHAM) survey

51 globular clusters from the survey (Dias et al. 2016a, A&A, 590, 9 )

Homogeneous scales of globular cluster metallicities are very important to constrain chemical evolution models of the halo and bulge of the Milky Way, if they are combined with ages. Measuring [α/Fe], it is also possible to trace the star formation history of the host galaxy. In particular, in the last few years it was found that some massive clusters present a dispersion in [Fe/H] due to multiple stellar populations. Thus we are performing a survey of 51 (~1/3 of the total) globular clusters of the Milky Way (bulge+halo) which are distant and/or highly reddened. Mid-resolution spectra for about 20 red giant stars were observed in each cluster in the visible and near infrared regions. We provide an homogeneous scale of [Fe/H], [α/Fe] plus radial velocities and membership selection for follow-up with high-resolution spectroscopy. We also provide a list of clusters which possibly host multiple populations such as M22 and NGC5824, revealed by our project. With these results we are able to constrain age-metallicity relation for the Milky Way, [α/Fe] vs. [Fe/H] star formation history, etc. This procedure can also be applied to extragalactic systems where it is possible to spatially resolve stars.

References:


- Dias et al. 2016c, Msngr, 165, 19
- Dias et al. 2016a, A&A, 590, 9
- Dias et al. 2015, A&A, 573, 13
- Saviane et al. 2012, A&A, 540, 27
- Saviane et al. 2012, Msngr, 149, 23
- Da Costa et al. 2009, ApJ, 705, 1481





VIsible photometric survey on Soar star Clusters from tApii Coxi HuguA
(VISCACHA) survey

SMC star clusters distribution (Dias et al. 2016b, A&A, 591, 11)

It is known that there were tidal interactions between the Milky Way and the Magellanic Clouds which formed the Magellanic Bridge and the Magellanic Stream. The stellar counterpart of these gas structures can be studied by means of star clusters, in particular those with ages between ~3 and 10 Gyr, corresponding to an age gap in the LMC cluster population. The Small Cloud have clusters with all ages, that could be witnessess of these iteractions ~2.5 Gyr and ~6.5 Gyr ago. We have observed integrated spectra and photometry (color-magnitude diagrams) of intermediate-age star clusters to better describe the SMC stellar populations. We are looking for age and metallicity gradients in some regions of the SMC, which can indicate tidal interactions that occurred in the past between SMC, LMC, and Milky Way.

"Tapi'i Hugua" and "Coxi Hugua" are the tupi-guarani version of Small and Large Magellanic Clouds, respectively. The translation means "Tapir's water supply (or lake)" and "Musk hog's water supply (or lake)".

References:


- Dias et al. 2016b, A&A, 591, 11
- Bica et al. 2015, MNRAS, 453, 3190
- Dias et al. 2014, A&A, 561, 106
- Balbinot et al. 2010, MNRAS, 404, 1625
- Dias et al. 2010, A&A, 520, 85





VISTA Variables in the Via Lactea (VVV) survey

96 new Milky Way open clusters from VVV Survey (Borissova+11)

This survey covers the bulge and part of the disc of the Milky Way, observing images in the Z,Y,J,H,Ks bands plus a variability campaign in the Ks band. We are interested in to identify variable stars (RR Lyrae) in globular clusters in order to determine their distances with more accuracy, especially those located in crowded and/or highly reddened regions such as bulge clusters. The survey already resulted in a detailed extinction map of the covered regions, therefore a good determination of the clusters distance is crucial to avoid degeneracy during the determination of other parameters such as age and metallicity.

References:


- Minniti et al. 2017, ApJ, 838, 14
- Saito et al. 2012b, A&A, 544, 147
- Saito et al. 2012a, A&A, 537, 107
- Borissova et al. 2011, A&A, 532, 131