Discovery of an Ultra-Faint Stellar System near the Magellanic Clouds with the DECam Local Volume Exploration (DELVE) Survey

Abstract

We report the discovery of a new ultra-faint stellar system found near the Magellanic Clouds in the DECam Local Volume Exploration (DELVE) Survey. This new system, DELVE J0155$-$6815 (DELVE 2), is located at a heliocentric distance of $D_{\odot }=71\pm 4\text{ kpc}$, which places it at a 3D physical separation of 12 kpc from the center of Small Magellanic Cloud (SMC) and 28 kpc from the center of the Large Magellanic Cloud (LMC). DELVE 2 is identified as a resolved overdensity of old ($\tau >13.3\text{ Gyr}$) and metal-poor ($[Fe/H]=-2.0_{-0.5}^{+0.2}$ dex) stars with a projected half-light radius of $r_{1/2}=21_{-3}^{+4}\text{ pc}$ and an absolute magnitude of $M_V=-2.1_{-0.5}^{+0.4}\text{ mag}$. The size and luminosity of DELVE 2 are consistent with both the population of recently discovered ultra-faint globular clusters and the smallest ultra-faint dwarf galaxies. However, its age and metallicity would place it among the oldest and most metal-poor globular clusters in the Magellanic system. DELVE 2 is detected in Gaia DR2 with a clear proper motion signal, with multiple blue horizontal branch stars near the centroid of the system with proper motions consistent with the systemic mean. We measure the system proper motion to be $({\mu }_{\alpha }\cos \delta ,{\mu }_{\delta })=(1.02_{-0.25}^{+0.24},-0.85_{-0.19}^{+0.18})$ mas yr${}^{-1}$. We compare the spatial position and proper motion of DELVE 2 with simulations of the accreted satellite population of the LMC and find that it is very likely to be associated with the LMC.

17 pages, 5 figures, submitted to AAS journals

References in corpus (30)

• The NumPy array: a structure for efficient numerical computation
• galpy: A Python Library for Galactic Dynamics
• Cats and Dogs, Hair and A Hero: A Quintet of New Milky Way Companions
• An eclipsing binary distance to the Large Magellanic Cloud accurate to 2 per cent
• Beasts of the Southern Wild: Discovery of nine Ultra Faint satellites in the vicinity of the Magellanic Clouds
• The Origin of the Magellanic Stream and Its Leading Arm
• The Blanco Cosmology Survey: Data Acquisition, Processing, Calibration, Quality Diagnostics and Data Release
• Clustering of Local Group distances: publication bias or correlated measurements? I. The Large Magellanic Cloud
• Milky Way Satellite Census. II. Galaxy--Halo Connection Constraints Including the Impact of the Large Magellanic Cloud
• Small Dwarf Galaxies Within Larger Dwarfs: Why Some Are Luminous While Most Go Dark
• The Orbital Histories of Magellanic Satellites Using Gaia DR2 Proper Motions
• Milky Way Satellite Census. I. The Observational Selection Function for Milky Way Satellites in DES Y3 and Pan-STARRS DR1
• Hydra II: a faint and compact Milky Way dwarf galaxy found in the Survey of the Magellanic Stellar History
• A New Faint Milky Way Satellite Discovered in the Pan-STARRS1 3 pi Survey
• Clustering of Local Group distances: publication bias or correlated measurements? III. The Small Magellanic Cloud
• Forward Global Photometric Calibration of the Dark Energy Survey
• A new distant Milky Way globular cluster in the Pan-STARRS1 3π survey
• ATLAS lifts the Cup: Discovery of a New Milky Way satellite in Crater
• An Ultra-Faint Galaxy Candidate Discovered in Early Data from the Magellanic Satellites Survey
• Two Ultra-Faint Milky Way Stellar Systems Discovered in Early Data from the DECam Local Volume Exploration Survey
• Multiple populations in the old and massive Small Magellanic Cloud globular cluster NGC121
• A New Milky Way Satellite Discovered In The Subaru/Hyper Suprime-Cam Survey
• A Hero's Little Horse: Discovery of a Dissolving Star Cluster in Pegasus
• On the nature of ultra-faint dwarf galaxy candidates I: DES1, Eridanus III and Tucana V
• Search for RR Lyrae stars in DES ultra-faint systems: Grus I, Kim 2, Phoenix II, and Grus II
• Dark and luminous satellites of LMC-mass galaxies in the FIRE simulations
• The Large Magellanic Cloud stellar content with SMASH: I. Assessing the stability of the Magellanic spiral arms
• A SkyMapper view of the Large Magellanic Cloud: The dynamics of stellar populations
• Explaining the mass-to-light ratios of globular clusters
• A search for star clusters in the outskirts of the Large Magellanic Cloud: indication of clusters in the age gap

Cited by in corpus (27)

• Gaia early DR3 systemic motions of Local Group dwarf galaxies and orbital properties with a massive Large Magellanic Cloud
• The DECam Local Volume Exploration Survey: Overview and First Data Release
• Measuring the Milky Way mass distribution in the presence of the LMC
• The DECam Local Volume Exploration Survey Data Release 2
• Resolved Dwarf Galaxy Searches within ~5 Mpc with the Vera Rubin Observatory and Subaru Hyper Suprime-Cam
• Six More Ultra-Faint Milky Way Companions Discovered in the DECam Local Volume Exploration Survey
• Pegasus IV: Discovery and Spectroscopic Confirmation of an Ultra-Faint Dwarf Galaxy in the Constellation Pegasus
• Hubble Space Telescope Observations of NGC 253 Dwarf Satellites: Discovery of Three Ultra-faint Dwarf Galaxies
• Metallicity Distribution Functions of 13 Ultra-Faint Dwarf Galaxy Candidates from Hubble Space Telescope Narrowband Imaging
• Pegasus V -- a newly discovered ultra-faint dwarf galaxy on the outskirts of Andromeda
• Discovery of a new Local Group Dwarf Galaxy Candidate in UNIONS: Boötes V
• DELVE-ing into the Jet: a thin stellar stream on a retrograde orbit at 30 kpc
• A Pride of Satellites in the Constellation Leo? Discovery of the Leo VI Milky Way Satellite Galaxy with DELVE Early Data Release 3
• Searching for Dwarf Galaxies in $Gaia$ DR2 Phase-Space Data Using Wavelet Transforms
• First evidence of a stripped star cluster from the Small Magellanic Cloud
• Estimate of the Mass and Radial Profile of the Orphan-Chenab Stream's Dwarf Galaxy Progenitor Using MilkyWay@home
• The emergence of globular clusters and globular-cluster-like dwarfs
• DELVE-DEEP Survey: The Faint Satellite System of NGC 55
• The YMCA (Yes, Magellanic Clouds Again) survey: probing the outer regions of the Magellanic system with VST
• Line-of-sight mass estimator and the masses of the Milky Way and Andromeda Galaxy
• Ultra-Faint Milky Way Satellites Discovered in Carina, Phoenix, and Telescopium with DELVE Data Release 3
• DELVE Milky Way Satellite Galaxy Census I: Satellite Population and Survey Selection Function in DES, DELVE, and Pan-STARRS
• Quantifying the Detectability of Milky Way Satellites with Image Simulations: a Case Study with KiDS
• Euclid: Early Release Observations -- The star cluster systems of the Local Group dwarf galaxies IC 10 and NGC 6822
• Eridanus IV: an Ultra-Faint Dwarf Galaxy Candidate Discovered in the DECam Local Volume Exploration Survey
• Forward-modelling the Luminosity, Distance, and Size distributions of the Milky Way Satellites
• Magellan/IMACS spectroscopy of Grus I: A low metallicity ultra-faint dwarf galaxy