Astronomy and Astrophysics – Astrophysics – Galaxy Astrophysics
Scientific paper
2011-01-21
Astronomy and Astrophysics
Astrophysics
Galaxy Astrophysics
52 pages, 13 figures
Scientific paper
The Hercules Thick Disk Cloud (Larsen et al. 2008) was initially discovered as an excess in the number of faint blue stars between quadrants 1 and 4 of the Galaxy. The origin of the Cloud could be an interaction with the disk bar, a triaxial thick disk or a merger remnant or stream. To better map the spatial extent of the Cloud along the line of sight, we have obtained multi-color UBVR photometry for 1.2 million stars in 63 fields approximately 1 square degree each. Our analysis of the fields beyond the apparent boundaries of the excess have already ruled out a triaxial thick disk as a likely explanation (Larsen, Humphreys and Cabanela 2010) In this paper we present our results for the star counts over all of our fields, determine the spatial extent of the over density across and along the line of sight, and estimate the size and mass of the Cloud. Using photometric parallaxes, the stars responsible for the excess are between 1 and 6 kiloparsecs from the Sun, 0.5 -- 4 kpc above the Galactic plane, and extends approximately 3-4 kiloparsecs across our line of sight. It is thus a major substructure in the Galaxy. The distribution of the excess along our sight lines corresponds with the density contours of the bar in the Disk, and its most distant stars are directly over the bar. We also see through the Cloud to its far side. Over the entire 500 square degrees of sky containing the Cloud, we estimate more than 5.6 million stars and 1.9 million solar masses of material. If the over density is associated with the bar, it would exceed 1.4 billion stars and more than than 50 million solar masses. Finally, we argue that the Hercules-Aquila Cloud (Belokurov et al. 2007) is actually the Hercules Thick Disk Cloud.
Cabanela Juan E.
Humphreys Roberta M.
Larsen Jeffrey A.
No associations
LandOfFree
Mapping the Asymmetric Thick Disk: II Distance, Size and Mass of the Hercules Thick Disk Cloud does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Mapping the Asymmetric Thick Disk: II Distance, Size and Mass of the Hercules Thick Disk Cloud, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Mapping the Asymmetric Thick Disk: II Distance, Size and Mass of the Hercules Thick Disk Cloud will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-19606