Discovery of Two New Globular Clusters in the Milky Way

Abstract

The spatial distribution of known globular clusters (GCs) in the Milky Way shows that the current census of GCs is incomplete in the direction of the Galactic plane. We present the discovery of two new GCs located close to the Galactic plane in the sky. These two GCs, RLGC 1 and RLGC 2, were discovered serendipitously during our new cluster survey (Ryu & Lee 2018) based on near-Infrared and mid-Infrared survey data. The two GCs show a grouping of resolved stars in their $K$ band images and a presence of faint diffuse light in their outer regions in the WISE $W1$ band images. They also show prominent red giant branches (RGBs) in their $K$ vs. $(J-K)$ color-magnitude diagrams (CMDs). We determine structural parameters of the two GCs using King profile fitting on their $K$ band radial number density profiles. The determined values are consistent with those of known GCs. Finally, we determine the distances, metallicities, and reddenings of the two GCs using the isochrone fitting on their CMDs. For the fitting, we assume that the ages of the two GCs are 12.6 Gyr and the brightest RGB stars of each cluster correspond to the tip of the RGB. Distances and metallicities of the two GCs are estimated to be $d=28.8\pm 4.3$ kpc and $\text{[Fe/H]}=-2.2\pm 0.2$ for RLGC 1 and $d=15.8\pm 2.4$ kpc and $\text{[Fe/H]}=-2.1\pm 0.3$ for RLGC 2. These results show that the two GCs are located at the far-half region of the Milky Way and they may belong to the halo of the Milky Way.

arXiv comment8 pages, 3 figures, accepted to ApJL

References in corpus (34)

• The Wide-field Infrared Survey Explorer (WISE): Mission Description and Initial On-orbit Performance
• PARSEC: stellar tracks and isochrones with the PAdova and TRieste Stellar Evolution Code
• The UKIRT Infrared Deep Sky Survey (UKIDSS)
• Stellar population models of Lick indices with variable element abundance ratios
• Eight New Milky Way Companions Discovered in First-Year Dark Energy Survey Data
• The UKIDSS Galactic Plane Survey
• The Ages of 55 Globular Clusters as Determined Using an Improved delta V_TO^HB Method Along with Color-Magnitude Diagram Constraints, and Their Implications for Broader Issues
• The UKIRT Wide Field Camera ZYJHK Photometric System: Calibration from 2MASS
• A New Milky Way Companion: Unusual Globular Cluster or Extreme Dwarf Satellite?
• Sagittarius II, Draco II and Laevens 3: three new Milky Way satellites discovered in the Pan-STARRS 1 3pi Survey
• Big fish, small fish: Two New Ultra-Faint Satellites of the Milky Way
• A new distant Milky Way globular cluster in the Pan-STARRS1 3π survey
• A Deeper Look at the New Milky Way Satellites: Sagittarius II, Reticulum II, Phoenix II, and Tucana III
• Discovery of a Faint Outer Halo Milky Way Star Cluster in the Southern Sky
• Discovery of VVV CL001. A Low-Mass Globular Cluster Next to UKS~1 in the Direction of the Galactic Bulge
• Three Galactic globular cluster candidates
• Gaia 1 and 2. A pair of new Galactic star clusters
• New galactic star clusters discovered in the VVV survey. Candidates projected on the inner disk and bulge
• A new Milky Way halo star cluster in the Southern Galactic Sky
• A Hero's Little Horse: Discovery of a Dissolving Star Cluster in Pegasus
• Digging deeper into the Southern skies: a compact Milky-Way companion discovered in first-year Dark Energy Survey data
• The Discovery of an Ultra-Faint Star Cluster in the Constellation of Ursa Minor
• FSR 1716: A new Milky Way Globular Cluster confirmed using VVV RR Lyrae stars
• A Hubble Space Telescope Study of the Enigmatic Milky Way Halo Globular Cluster Crater
• RR Lyrae-based calibration of the Globular Cluster Luminosity Function
• Kim 3: an Ultra-faint Star Cluster in the Constellation of Centaurus
• FSR1767 - a new globular cluster in the Galaxy
• Integrated Light 2MASS IR Photometry of Galactic Globular Clusters
• On the physical nature of globular cluster candidates in the Milky Way bulge
• A WISE Survey of New Star Clusters in the Central Plane Region of the Milky Way
• FSR584 - a new globular cluster in the Galaxy?
• NTT follow-up observations of star cluster candidates from the FSR catalogue
• FSR0190 - Another old distant galactic cluster
• Pfleiderer2: identification of a new globular cluster in the Galaxy

Cited by in corpus (25)

• Gaia EDR3 view on Galactic globular clusters
• Accurate distances to Galactic globular clusters through a combination of Gaia EDR3, HST and literature data
• What is a globular cluster? An observational perspective
• A Sequoia in the Garden: FSR 1758 - Dwarf Galaxy or Giant Globular Cluster?
• A Multi-Band Catalog of 10978 Star Clusters, Associations and Candidates in the Milky Way
• Purveyors of fine halos: Re-assessing globular cluster contributions to the Milky Way halo build-up with SDSS-IV
• Analysis of the physical nature of 22 New VVV Survey Globular Cluster candidates in the Milky Way Bulge
• Dynamically Tagged Groups of Metal-Poor Stars from the Best \& Brightest Survey
• Globular cluster candidates in the Galactic bulge: Gaia and VVV view of the latest discoveries
• Three candidate globular clusters discovered in the Galactic bulge
• Detailed chemical composition and orbit of the new globular cluster FSR1758: Implications for the accretion of the Sequoia dwarf galaxy onto the Milky Way
• The R-Process Alliance: Chemo-Dynamically Tagged Groups II. An Extended Sample of Halo $r$-Process-Enhanced Stars
• Dynamically Tagged Groups of Metal-Poor Stars II. The Radial Velocity Experiment Data Release 6
• A census of new globular clusters in the Galactic bulge
• Formation imprints in the kinematics of the Milky Way globular cluster system
• CAPOS: the bulge Cluster APOgee Survey II. The Intriguing "Sequoia" Globular Cluster FSR 1758
• Unveiling the nature of 12 new low-luminosity Galactic Globular Cluster Candidates
• The globular cluster system of the Auriga simulations
• Survey for Distant Stellar Aggregates in Galactic Disk: Detecting Two Thousand Star Clusters and Candidates, along with the Dwarf Galaxy IC10
• Halo intruders in the Galactic bulge revealed by HST and Gaia: the globular clusters Terzan 10 and Djorgovski 1
• New Candidate Planetary Nebulae in Galactic Globular Clusters from the VVV Survey
• An Intriguing Globular Cluster in the Galactic Bulge from the VVV Survey
• The Likelihood of Undiscovered Globular Clusters in the Outskirts of the Milky Way
• Three New Galactic Globular Cluster Candidates: FSR1700, Teutsch67, and CWNU4193
• Globular clusters as indicators of Galactic evolution