Mapping the Asymmetric Thick Disk: The Hercules Thick Disk Cloud

Abstract

The stellar asymmetry of faint thick disk/inner halo stars in the first quadrant first reported by Larsen & Humphreys (1996) and investigated further by Parker et al. (2003, 2004) has been recently confirmed by SDSS (Juric et al. 2008). Their interpretation of the excess in the star counts as a ringlike structure, however, is not supported by critical complimentary data in the fourth quadrant not covered by SDSS. We present stellar density maps from the Minnesota Automated Plate Scanner (MAPS) Catalog of the POSS I showing that the overdensity does not extend into the fourth quadrant. The overdensity is most probably not a ring. It could be due to interaction with the disk bar, evidence for a triaxial thick disk, or a merger remnant/stream. We call this feature the Hercules Thick Disk Cloud.

11 pages, 5 figures, to be published in Astrophysical Journal Letters

References in corpus (6)

• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• The Milky Way Tomography with SDSS: I. Stellar Number Density Distribution
• Simulations of Galaxy Formation in a Lambda CDM Universe II: The Fine Structure of Simulated Galactic Disks
• The Hercules-Aquila Cloud
• The Asymmetric Thick Disk: A Star Count and Kinematic Analysis. II The Kinematics
• The structure of the Galactic halo: SDSS versus SuperCOSMOS

Cited by in corpus (11)

• Secular Evolution in Disk Galaxies
• Stellar Streams and Clouds in the Galactic Halo
• Galactic Archaeology. The dwarfs that survived and perished
• The 3D Velocity Structure of the Thick Disk from SPM4 and RAVE DR2
• Simulations of minor mergers. II. The phase-space structure of thick discs
• Evidence of a thick disk rotation-metallicity correlation
• Spectroscopic Follow-Up of the Hercules Aquila Cloud
• Mapping the Asymmetric Thick Disk: II Distance, Size and Mass of the Hercules Thick Disk Cloud
• Mapping the Asymmetric Thick Disk: III. The Kinematics and Interaction with the Galactic Bar
• Mapping the Asymmetric Thick Disk I. A Search for Triaxiality
• Local stellar kinematics from RAVE data- V. Kinematic investigation of the Galaxy with red clump stars