The Milky Way Tomography with SDSS. 1. Stellar Number Density Distribution

Journal Article · Sat Oct 01 00:00:00 EDT 2005 · Astrophys.J.

DOI:https://doi.org/10.1086/523619· OSTI ID:879053

Jurić, Mario ^[1]; Ivezić, Željko ^[2]; Brooks, Alyson ^[2]; Lupton, Robert H. ^[3]; Schlegel, David ^[3]; Finkbeiner, Douglas ^[3]; Padmanabhan, Nikhil ^[4]; Bond, Nicholas ^[3]; Sesar, Branimir ^[2]; Rockosi, Constance M. ^[2]; Knapp, Gillian R. ^[3]; Gunn, James E. ^[3]; Sumi, Takahiro ^[5]; Schneider, Donald P. ^[6]; Barentine, J. C. ^[7]; Brewington, Howard J. ^[7]; Brinkmann, J. ^[7]; Fukugita, Masataka ^[8]; Harvanek, Michael ^[7]; Kleinman, S. J. ^[7] ; Krzesinski, Jurek ^[9]; Long, Dan ^[7]; H.Neilsen, Jr. Eric ^[10]; Nitta, Atsuko ^[7]; Snedden, Stephanie A. ^[7]; York, Donald G. ^[11]

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1. Princeton U., Astrophys. Sci. Dept.; Princeton, Inst. Advanced Study
2. Washington U., Seattle, Astron. Dept.
3. Princeton U., Astrophys. Sci. Dept.
4. Princeton U.
5. Princeton U., Astrophys. Sci. Dept.; Nagoya U., Solar-Terrestrial Environ. Lab.
6. Penn State U., Astron. Astrophys.
7. Apache Point Observ.
8. Tokyo U., ICRR
9. Apache Point Observ.; Pedagogical U., Cracow
10. Fermilab
11. Chicago U., EFI

Abridged: We estimate the distances to ~48 million stars detected by the Sloan Digital Sky Survey and map their 3D number density distribution in 100 < D < 20 kpc range over 6,500 deg^2 of sky. The data show strong evidence for a Galaxy consisting of an oblate halo, a disk component, and a number of localized overdensities with exponential disk parameters (bias-corrected for an assumed 35% binary fraction) H_1 = 300 pc, L_1 = 2600 pc, H_2 = 900 pc, L_2 = 3600 pc, and local density normalization of 12%. We find the halo to be oblate, with best-fit axis ratio c/a = 0.64, r^{-2.8} profile, and the local halo-to-thin disk normalization of 0.5%. We estimate the errors of derived model parameters to be no larger than ~20% (disk scales) and ~10% (thick disk normalization). While generally consistent with the above model, the density distribution shows a number of statistically significant localized deviations. We detect two overdensities in the thick disk region at (R, Z) ~ (6.5, 1.5)kpc and (R, Z) ~ (9.5, 0.8) kpc, and a remarkable density enhancement in the halo covering >1000deg^2 of sky towards the constellation of Virgo, at distances of ~6-20 kpc. Compared to a region symmetric with respect to the l=0 line, the Virgo overdensity is responsible for a factor of 2 number density excess and may be a nearby tidal stream or a low-surface brightness dwarf galaxy merging with the Milky Way. After removal of the resolved overdensities, the remaining data are consistent with a smooth density distribution; we detect no evidence of further unresolved clumpy substructure at scales ranging from ~50pc in the disk, to ~1 - 2 kpc in the halo.

• Research Organization: Princeton U., Astrophys. Sci. Dept.; Washington U., Seattle, Astron. Dept.; Penn State U., Astron. Astrophys.; Tokyo U., ICRR; Princeton, Inst. Advanced Study; Apache Point Observ.; Princeton U.; Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States); Pedagogical U., Cracow; Chicago U., EFI; Nagoya U., Solar-Terrestrial Environ. Lab.
• Sponsoring Organization: US Department of Energy
• DOE Contract Number: AC02-07CH11359
• OSTI ID: 879053
• Report Number(s): FERMILAB-PUB-05-591-CD; oai:inspirehep.net:695347; arXiv:astro-ph/0510520
• Journal Information: Astrophys.J., Journal Name: Astrophys.J. Vol. 673
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
Astrophysics
BRIGHTNESS
COLOR
DISTRIBUTION
MILKY WAY
SCALE HEIGHT
SKY
STARS
TOMOGRAPHY