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

By Mario Juric, Željko Ivezic´, A. Brooks, Robert Lupton, David Schlegel, Douglas P. Finkbeiner, Nikhil Padmanabhan, Nicholas A. Bond, B. Sesar, C. Rockosi and 16 more. 2005

1,015 citations recorded by the source corpus.

Using the photometric parallax method we estimate the distances to ~48 million stars detected by the Sloan Digital Sky Survey (SDSS) and map their three-dimensional number density distribution in the Galaxy. The currently available data sample the distance range from 100 pc to 20 kpc and cover 6500 deg2 of sky, mostly at high Galactic latitudes (|b| > 25). These stellar number density maps allow an investigation of the Galactic structure with no a priori assumptions about the functional form of its components. The data show strong evidence for a Galaxy consisting of an oblate halo, a disk component, and a number of localized overdensities. The number density distribution of stars as traced by M dwarfs in the solar neighborhood (D < 2 kpc) is well fit by two exponential disks (the thin and thick disk) with scale heights and lengths, bias corrected for an assumed 35% binary fraction, of H1 = 300 pc and L1 = 2600 pc, and H2 = 900 pc and L2 = 3600 pc, and local thick-to-thin disk density normalization ρthick(R☉)/ρthin(R☉) = 12% . We use the stars near main-sequence turnoff to measure the shape of the Galactic halo. We find a strong preference for oblate halo models, with best-fit axis ratio c/a = 0.64, ρH ∝ r−2.8 power-law profile, and the local halo-to-thin disk normalization of 0.5%. Based on a series of Monte Carlo simulations, we estimate the errors of derived model parameters not to be larger than ~20% for the disk scales and ~10% for the density normalization, with largest contributions to error coming from the uncertainty in calibration of the photometric parallax relation and poorly constrained binary fraction. While generally consistent with the above model, the measured density distribution shows a number of statistically significant localized deviations. In addition to known features, such as the Monoceros stream, we detect two overdensities in the thick disk region at cylindrical galactocentric radii and heights (R,Z) ∼ (6.5,1.5) kpc and (R,Z) ∼ (9.5,0.8) kpc and a remarkable density enhancement in the halo covering over 1000 deg2 of sky toward the constellation of Virgo, at distances of ~6-20 kpc. Compared to counts in a region symmetric with respect to the l = 0° line and with the same Galactic latitude, 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. The u − g color distribution of stars associated with it implies metallicity lower than that of thick disk stars and consistent with the halo metallicity distribution. 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 ~50 pc in the disk to ~1-2 kpc in the halo.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/eeadf131c83dfc0ac434ab563b0c5f9588d66674

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

In Instrumentation

Citations in the corpus

Constraining the Milky Way assembly history with Galactic Archaeology (2016, neutral): “…be provided by the publisher results for the Milky Way when similar morphologically (or structural) definition for the thick disc is used (e.g., Jurić et al. 2008; Ojha 2001; Robin et al. 1996), it is in contradiction with the more centrally concentrated older or [α/Fe]-enhanced stellar…”
The 511 keV emission from positron annihilation in the Galaxy (2010, methodology): “Furthermore, the Sun is not located exactly on the plane, but at a distance from it z⊙ ∼25 pc, as evaluated from the recent analysis of the Sloan Digital Sky Survey (SDSS) data (Jurić et al., 2008).”
SEGUE: A SPECTROSCOPIC SURVEY OF 240,000 STARS WITH g = 14–20 (2009, background): “The five streams are Sagittarius (Yanny et al. 2000), Monoceros (Newberg et al. 2002), Orphan (Belokurov et al. 2007b), Virgo (Vivas et al. 2001; Juric et al. 2008) and GD-1 (Grillmair & Dionatos 2006).”
THE SLOAN DIGITAL SKY SURVEY COADD: 275 deg2 OF DEEP SLOAN DIGITAL SKY SURVEY IMAGING ON STRIPE 82 (2011, methodology): “In Figure 10 the galactic model parameters are those found by Jurić et al. (2008) using their SDSS star count tomographic mapping technique.”
Confirming chemical clocks: asteroseismic age dissection of the Milky Way disc(s) (2017, background): “The Milky Way disc has been geometrically separated into a thin and a thick components that dominate at different heights, and were identified using stellar counts more than 30 yr ago (Gilmore & Reid 1983; Jurić et al. 2008).”
ERRATUM: “THE LUMINOSITY AND MASS FUNCTIONS OF LOW-MASS STARS IN THE GALACTIC DISK. II. THE FIELD” (2010, AJ, 139, 2679) (2010, methodology): “In particular, the differences between our investigation and the Jurić et al. (2008) study highlight the sensitivity of these parameters to the assumed CMR and density profiles, as they included a halo in their study and we did not.”
MEASURING REDDENING WITH SLOAN DIGITAL SKY SURVEY STELLAR SPECTRA AND RECALIBRATING SFD (2010, methodology): “For the dwarf stars in the survey, we use the Jurić et al. (2008) “bright” photometric parallax relation to get approximate distances to stars from their colors.”
Numerical simulation of a possible origin of the positive radial metallicity gradient of the thick disk (2013, background): “Current estimates put the value around 10:1 in favor of the thin disk (Jurić et al. 2008).”
The Milky Way stellar halo out to 40 kpc: squashed, broken but smooth (2011, methodology): “A number of studies have attempted to model the smooth halo component by avoiding these known substructures (e.g. Jurić et al. 2008).”
MAPPING THE STELLAR STRUCTURE OF THE MILKY WAY THICK DISK AND HALO USING SEGUE PHOTOMETRY (2009, methodology): “It is again important to note the difference between this approach and using stars of a particular spectral type to make 3D maps of the Milky Way (as in e.g. Jurić et al. 2008).”
Chemical evolution with radial mixing (2008, methodology): “…Binney (1998) but with the thin- and thick-disc scaleheights taken to be 0.3 and 0.9 kpc, the total stellar surface density set to 35.5 M pc−2 with 3/4 of the stellar mass in the thin disc and the gas surface density set to 13.2 M pc−2 in conformity with Flynn et al. (2006) and Juric et al. (2008).”
THE SPATIAL STRUCTURE OF MONO-ABUNDANCE SUB-POPULATIONS OF THE MILKY WAY DISK (2011, methodology): “10 percent, and thus do not greatly smooth the underlying Galactic density, whose scales are much larger than this (for an illustration of this see Jurić et al. 2008, where much larger distance uncertainties of around 20 percent were shown to influence the inferred scale heights by less than 5…”
A LARGE CATALOG OF ACCURATE DISTANCES TO MOLECULAR CLOUDS FROM PS1 PHOTOMETRY (2014, background): “It additionally folds in prior expectations about the distribution of stars in space (Jurić et al. 2008), metallicity (Ivezić et al. 2008), and luminosity (Bressan et al. 2012).”