Confirmation Of Two New Galactic Bulge Globular Clusters: FSR 19 and FSR 25

Abstract

Globular clusters (GCs) in the Milky Way (MW) bulge are very difficult to study because: i) they suffer from the severe crowding and galactic extinction; which are characteristic of these inner Galactic regions ii) they are more prone to be affected by dynamical processes. Therefore, they are relatively faint and difficult to map. However, deep near-infrared photometry like that provided by the VISTA Variables in the Via Láctea Extended Survey (VVVX) is allowing us to map GCs in this crucial yet relatively uncharted region. Our results confirm with high confidence that both FSR 19 and FSR 25 are genuine MW bulge GCs. Each of the performed tests and resulting parameters provides clear evidence for the GC nature of these targets. We derive distances of 7.2$\pm$0.7 kpc and D=7.0$\pm$0.6 (corresponding to distance moduli of 14.29$\pm$0.08 and 14.23$\pm$0.07) for FSR 19 and FSR 25, respectively. Their ages and metallicities are 11 Gyr and [Fe/H]= -0.5 dex for both clusters, which were determined from Dartmouth and PARSEC isochrone fitting. The integrated luminosities are M${}_{Ks}$(FSR 19) = -7.72 mag and M${}_{Ks}$(FSR 25) = -7.31 mag which places them in the faint tail of the GC Luminosity Function. By adopting a King profile for their number distribution, we determine their core and tidal radii ($r_c$, $r_t$). For FSR 19, r${}_c$= 2.76$\pm$0.36 pc and r${}_t$=5.31$\pm$0.49 pc, while FSR 25 appears more extended with r${}_c$= 1.92$\pm$0.59 pc and r${}_t$=6.85$\pm$1.78 pc. Finally their mean GC PMs (from Gaia EDR3) are ${\mu }_{{\alpha }^{\ast }}$= -2.50 $\pm$0.76 mas $y{r}^{-1}$, ${\mu }_{\delta }$= -5.02 $\pm$0.47 mas $y{r}^{-1}$ and ${\mu }_{{\alpha }^{\ast }}$= -2.61 $\pm$ 1.27 mas $y{r}^{-1}$ , ${\mu }_{\delta }$= -5.23 $\pm$0.74 mas $y{r}^{-1}$ for FSR 19 and FSR 25, respectively. }

References in corpus (10)

• A systematic survey for infrared star clusters with |b|<20deg using 2MASS
• A Sequoia in the Garden: FSR 1758 - Dwarf Galaxy or Giant Globular Cluster?
• Extinction ratios in the inner Galaxy as revealed by the VVV survey
• Empirical photometric calibration of the Gaia Red Clump: colours, effective temperature and absolute magnitude
• Mapping the stellar age of the Milky Way bulge with the VVV. III. High resolution reddening map
• Analysis of the physical nature of 22 New VVV Survey Globular Cluster candidates in the Milky Way Bulge
• VVVX-Gaia Discovery of a Low Luminosity Globular Cluster in the Milky Way Disk
• Confirmation and physical characterization of the new bulge globular cluster Patchick 99 from the VVV and Gaia surveys
• VVV WIN 1733$-$3349: a low extinction window to probe the far side of the Milky Way bulge
• The RR Lyrae projected density distribution from the Galactic centre to the halo