Discovery of Star Formation in the Extreme Outer Galaxy Possibly Induced by a High-velocity Cloud Impact

Abstract

We report the discovery of star formation activity in perhaps the most distant molecular cloud in the extreme outer galaxy. We performed deep near infrared imaging with the Subaru 8.2 m telescope, and found two young embedded clusters at two CO peaks of Digel Cloud 1 at the kinematic distance of D = 16 kpc (Galactocentric radius RG = 22 kpc). We identified 18 and 45 cluster members in the two peaks, and the estimated stellar density are ~ 5 and ~ 3 pc^-2, respectively. The observed K-band luminosity function suggests that the age of the clusters is less than 1 Myr and also the distance to the clusters is consistent with the kinematic distance. On the sky, Cloud 1 is located very close to the H I peak of high-velocity cloud (HVC) Complex H, and there are some H I intermediate velocity structures between the Complex H and the Galactic disk, which could indicate an interaction between them. We suggest possibility that Complex H impacting on the Galactic disk has triggered star formation in Cloud 1 as well as the formation of Cloud 1 molecular cloud.

arXiv comment9 pages, 8 figures, and 2 tables. Accepted for publication in Astrophysical Journal

References in corpus (29)

• The Wide-field Infrared Survey Explorer (WISE): Mission Description and Initial On-orbit Performance
• The Leiden/Argentine/Bonn (LAB) Survey of Galactic HI: Final data release of the combined LDS and IAR surveys with improved stray-radiation corrections
• Embedded Clusters in Molecular Clouds
• Disk Frequencies and Lifetimes in Young Clusters
• The Neutral Atomic Phases of the ISM in the Galaxy
• Spitzer Space Telescope study of disks in the young $\sigma$ Orionis cluster
• The Mauna Kea Observatories Near-Infrared Filter Set. II. Specifications for a New JHKL'M' Filter Set for Infrared Astronomy
• High Velocity Clouds: Building Blocks of the Local Group
• The maximum stellar mass, star-cluster formation and composite stellar populations
• JHK Observations of Faint Standard Stars in the Mauna Kea Near-Infrared Photometric System
• Observational Constraints on the Ages of Molecular Clouds and the Star-Formation Timescale: Ambipolar-Diffusion--Controlled or Turbulence-Induced Star Formation?
• On-The-Fly Observing System of the Nobeyama 45-m and ASTE 10-m Telescopes
• Giant Molecular Clouds in the Local Group Galaxy M33
• The Lifetime of Protoplanetary Disks in a Low-Metallicity Environment
• A Full-sky, High-resolution Atlas of Galactic 12 micron Dust Emission with WISE
• Modeling the Near-Infrared Luminosity Functions of Young Stellar Clusters
• Short Lifetime of Protoplanetary Disks in Low-metallicity Environments
• An Interaction of a Magellanic Leading Arm High Velocity Cloud with the Milky Way Disk
• Triggered Star Formation
• High Velocity Cloud Complex H: A Satellite of the Milky Way in a Retrograde Orbit?
• Star Formation in the Most Distant Molecular Cloud in the Extreme Outer Galaxy: A Laboratory of Star Formation in an Early Epoch of the Galaxy's Formation
• Star Formation in the Extreme Outer Galaxy: Digel Cloud 2 Clusters
• Triggered Star Formation on the Border of the Orion-Eridanus Superbubble
• Discovery of Young Stellar Objects at the Edge of the Optical Disk of Our Galaxy
• GSH 138-01-94, an old supernova remnant in the far outer Galaxy
• Deep Near-Infrared Imaging af an Embedded Cluster in the Extreme Outer Galaxy: Census of Supernovae Triggered Star Formation
• The Cosmological Significance of High-Velocity Cloud Complex H
• On the Formation of Perseus OB1 at High Galactic Latitudes
• Absolute Proper Motion of IRAS 00259+5625 with VERA : Indication of Superbubble Expansion Motion

Cited by in corpus (17)

• Isolating signatures of major cloud-cloud collisions using position-velocity diagrams
• Star Clusters in Evolving Galaxies
• Molecular clouds in the extreme outer Galaxy between $l=34.75^{\circ }$ to $45.25^{\circ }$
• Low-metallicity Young Clusters in the Outer Galaxy. II. Sh 2-208
• Collisions between Dark Matter Confined High Velocity Clouds and Magnetized Galactic Disks: The Smith Cloud
• Low-metallicity Young Clusters in the Outer Galaxy I. Sh 2-207
• Physical effects on compact high-velocity clouds in the circumgalactic medium
• High-Mass Star Formation in the Outer Scutum-Centaurus Arm
• An Unbiased CO Survey Toward the Northern Region of the Small Magellanic Cloud with the Atacama Compact Array. II. CO Cloud Catalog
• Star formation activity beyond the outer Arm I: WISE-selected candidate star-forming regions
• Overview Results of JWST Observations of Star-Forming Clusters in the Extreme Outer Galaxy
• A New Search for Star Forming Regions in the Southern Outer Galaxy
• A search for High Mass Stars Forming in Isolation using CORNISH & ATLASGAL
• Star formation in the circumgalactic high-velocity cloud Complex H
• Cosmic Rays and Non-thermal Emission Induced by Accretion of Cool Gas onto the Galactic Disk
• Molecular Clouds at the Edge of the Galaxy I. Variation of CO J=2-1/1-0 Line Ratio
• Molecular Clouds at the Edge of the Galaxy II. Physical properties and scaling relations