We use deep near-IR photometry of the VISTA Variables in the Via Lactea (VVV) Survey and deep DECam Plane Survey (DECaPS) optical photometry to confirm the physical reality of the candidate globular cluster (GC) Minni 22, which is located in the Galactic bulge. This object, which was detected as a high density region in our maps of bulge red giants, is now confirmed as a real GC based on the optical and near-IR color-magnitude diagrams. We also recover three known fundamental mode (ab type) RR Lyrae stars within 2 arcmin of the cluster center. The presence of RR Lyrae stars also seems to confirm Minni 22 as a bonafide old and metal-poor GC. We estimate a cluster reddening E(J-Ks)=0.6mag and determine its heliocentric distance D=7.4+/-0.3kpc. The optical and near-IR color-magnitude diagrams reveal well-defined red giant branches in all cases, including a red giant branch bump at Ks=13.30+/-0.05mag. The comparison with theoretical isochrones yields a mean metallicity of [Fe/H]=-1.3+/-0.3dex, and age of t~11.2Gyr. This is a good example of a new low-luminosity (M_V_=-6.2mag) GC found in the central bulge of the Milky Way. After discussing the different ways to confirm the existence of bulge GC candidates, we find that one of the best methods is to use the CMDs from the combination of the DECaPS+VVV photometries.
VVV DR5 - VISTA Variables in the Via Lactea survey
Date:
24 Jan 2022 11:52:51
Publisher:
WFAU, Institute for Astronomy, University of Edinburgh
Description:
The VVV survey will perform wide FOV multi-epoch observations of the Galaxy's bulge and part of the disk, providing the astronomical public community with a high resolution 3-D (or 4-D if you include the time dimension) map of the bulge.
VVV DR5 - VISTA Variables in the Via Lactea survey
Date:
24 Jan 2022 11:48:18
Publisher:
WFAU, Institute for Astronomy, University of Edinburgh
Description:
The VVV survey will perform wide FOV multi-epoch observations of the Galaxy's bulge and part of the disk, providing the astronomical public community with a high resolution 3-D (or 4-D if you include the time dimension) map of the bulge.
VVV DR4 - VISTA Variables in the Via Lactea survey
Date:
04 Dec 2019 13:43:08
Publisher:
WFAU, Institute for Astronomy, University of Edinburgh
Description:
The VVV survey will perform wide FOV multi-epoch observations of the Galaxy's bulge and part of the disk, providing the astronomical public community with a high resolution 3-D (or 4-D if you include the time dimension) map of the bulge.
VVV DR1 - VISTA Variables in the Via Lactea survey
Short Name:
VVV DR1
Date:
04 Dec 2019 13:42:47
Publisher:
WFAU, Institute for Astronomy, University of Edinburgh
Description:
The VVV survey will perform wide FOV multi-epoch observations of the Galaxy's bulge and part of the disk, providing the astronomical public community with a high resolution 3-D (or 4-D if you include the time dimension) map of the bulge.
VVV DR4 - VISTA Variables in the Via Lactea survey
Date:
20 Mar 2019 15:41:34
Publisher:
WFAU, Institute for Astronomy, University of Edinburgh
Description:
The VVV survey will perform wide FOV multi-epoch observations of the Galaxy's bulge and part of the disk, providing the astronomical public community with a high resolution 3-D (or 4-D if you include the time dimension) map of the bulge.
VVV DR2 - VISTA Variables in the Via Lactea survey
Date:
05 Mar 2014 15:10:06
Publisher:
WFAU, Institute for Astronomy, University of Edinburgh
Description:
The VVV survey will perform wide FOV multi-epoch observations of the Galaxy's bulge and part of the disk, providing the astronomical public community with a high resolution 3-D (or 4-D if you include the time dimension) map of the bulge.
VVV DR1 - VISTA Variables in the Via Lactea survey
Date:
17 Jul 2012 15:12:06
Publisher:
WFAU, Institute for Astronomy, University of Edinburgh
Description:
The VVV survey will perform wide FOV multi-epoch observations of the Galaxy's bulge and part of the disk, providing the astronomical public community with a high resolution 3-D (or 4-D if you include the time dimension) map of the bulge.
A detailed study of the Galactic bulge stellar population necessarily requires an accurate representation of the interstellar extinction, particularly toward the Galactic plane and center, where severe and differential reddening is expected to vary on sub-arcmin scales. Although recent infrared surveys have addressed this problem by providing extinction maps across the whole Galactic bulge area, dereddened color-magnitude diagrams near the plane and center appear systematically undercorrected, prompting the need for higher resolution. These undercorrections affect any stellar study sensitive to color (e.g., star formation history analyses via color-magnitude diagram fitting), either making them inaccurate or limiting them to small and relatively stable extinction windows where this value is low and better constrained. This study is aimed at providing a high-resolution (2-arcmin to 10-arcsec) color excess map for the VVV bulge area in J-Ks color. We used the MW-BULGE-PSFPHOT catalogs, sampling 300deg^2^ across the Galactic bulge (|l|<10{deg} and -10{deg}<b<5{deg}) to isolate a sample of red clump and red giant branch stars, for which we calculated the average J-Ks color in a fine spatial grid in (l, b) space. We obtained an E(J-Ks) map spanning the VVV bulge area of roughly 300deg^2^, with the equivalent of a resolution between 1-arcmin for bulge outskirts (l<-6{deg}) to below 20-arcsec within the central |l|<1{deg}, and below 10-arcsec for the innermost area (|l|<1{deg} and |b|<3{deg}). The results are publicly available at http://basti-iac.oa-teramo.inaf.it/vvvexmap/
The extragalactic vision we have through the Milky Way is very unclear. There is significant extinction of the optical emission from objects located in the region called the Zone of Avoidance (ZOA). NIR wavelengths are less affected by extinction, and therefore the infrared surveys in this zone are a potential source of astronomical discoveries. Nevertheless, these observations need to be compared with cosmological simulations in order to carry out high-accuracy studies. Our aim is to identify extragalactic sources in the ZOA, using infrared images of the VVV survey. We consider mock galaxy catalogues in order to interpret observational results. We studied a region of 1.636 square degrees corresponding to the VVV tile b204. Using SExtractor, we analysed photometric data generating a catalogue of extended sources in this area. In order to confirm these sources as galaxy candidates we visually inspected RGB images looking for typical galaxy features. Using 2MASX and GCMW catalogued sources we tested completeness and contamination of our catalogue and define suitable colour cuts to select galaxies. We also compared the observational results with those obtained from two semi-analytical models on Dark Matter simulations. One galaxy catalogue was constructed with the SAG semi-analytic model of galaxy formation, and the other one was constructed with the L-Galaxies semi-analytic model. By adopting CLASS_STAR<0.5, r1/2>0.7 arcsec and specific colour cuts (J-Ks>0.97, J-H>0 and H-Ks>0) we generated an automatic catalogue of extended sources. After visual inspection we identified 624 sources with 10<Ks<17 as galaxy candidates.The contamination of the automatic catalogue is 28% when considering visually confirmed galaxies as reliable objects. The estimated completeness is 87% up to magnitude Ks=13.5. We analysed the spatial distribution of galaxy candidates, finding a high concentration of galaxies in a small region of 15 arcmin radius. This region has three times higher density than similar areas in the tile. We compared the number of galaxies in this small area with the mean density values obtained from a suitable sample of galaxies from semi-analytic models finding that our results are consistent with an overdensity region. Using VVV near-infrared data and mock catalogues we detect new extragalactic sources that have not been identified by other catalogues. We demonstrate the potentiality of the VVV survey in finding and studying a large number of galaxy candidates and extragalactic structures obscured by the Milky Way.
