The Milky Way’s Circular Velocity Curve to 60 kpc and an Estimate of the Dark Matter Halo Mass from the Kinematics of ~2400 SDSS Blue Horizontal-Branch Stars

By Xiang-Xiang Xue, Hans-Walter Rix, Gang Zhao, P. Fiorentin, T. Naab, Matthias Steinmetz, F. C. V. D. Bosch, Timothy C. Beers, Y. S. Lee, Eric F. Bell and 7 more. 2008

605 citations recorded by the source corpus.

We derive new constraints on the mass of the Milky Way’s dark matter halo, based on 2401 rigorously selected blue horizontal-branch halo stars from SDSS DR6. This sample enables construction of the full line-of-sight velocity distribution at different galactocentric radii. To interpret these distributions, we compare them to matched mock observations drawn from two different cosmological galaxy formation simulations designed to resemble the Milky Way. This procedure results in an estimate of the Milky Way’s circular velocity curve to ~60 kpc, which is found to be slightly falling from the adopted value of 220 km s−1 at the Sun’s location, and implies M(< 60 kpc) = (4.0 ± 0.7) × 1011 M☉. The radial dependence of Vcir(r) , derived in statistically independent bins, is found to be consistent with the expectations from an NFW dark matter halo with the established stellar mass components at its center. If we assume that an NFW halo profile of characteristic concentration holds, we can use the observations to estimate the virial mass of the Milky Way’s dark matter halo, Mvir = 1.0+ 0.3−0.2 × 1012 M☉, which is lower than many previous estimates. We have checked that the particulars of the cosmological simulations are unlikely to introduce systematics larger than the statistical uncertainties. This estimate implies that nearly 40% of the baryons within the virial radius of the Milky Way’s dark matter halo reside in the stellar components of our Galaxy. A value for Mvir of only ~1 × 1012 M☉ also (re)opens the question of whether all of the Milky Way’s satellite galaxies are on bound orbits.

Subfields: Astronomy and Astrophysics, Atomic and Molecular Physics, and Optics

View Paper: https://www.semanticscholar.org/paper/e9eaf6dc4e491522c7ab073bbc2c247878b0b2cc

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 Atomic and Molecular Physics, and Optics

Citations in the corpus

The milky way total mass profile as inferred from Gaia DR2 (2019, methodology): “…have focused on determining the total mass of the Galactic DM halo using a variety of methods, such as the dynamics of the stellar halo (e.g. Xue et al. 2008; Deason et al. 2012; Kafle et al. 2012), globular clusters (e.g. Eadie & Harris 2016; Posti & Helmi 2019; Watkins et al. 2019) and…”
THE BARYON CONTENT OF COSMIC STRUCTURES (2009, methodology): “This appears consistent with the Milky Way (Flynn et al. 2006; Xue et al. 2008; McGaugh 2008) if fV = 1.1, which we adopt for specificity.”
Using the Milky Way satellites to study interactions between cold dark matter and radiation (2014, background): “…by calculations that attempt to reconstruct the MW mass distribution based on the measured kinematics of the observed satellites and stars (Xue et al. 2008; Boylan-Kolchin et al. 2013; Piffl et al. 2014), we consider DM haloes to be MW-like if their mass is in the range (0.8− 2.7)× 1012M .”
The mass distribution and gravitational potential of the Milky Way (2016, methodology): “Deason et al.(2012) and Xue et al. (2008) used samples of blue horizontal branch stars to determine the mass contained within 50 and 60 kpc (respectively).”
THE CASE FOR THE DUAL HALO OF THE MILKY WAY (2011, methodology): “Their sample overlaps substantially with that used by Xue et al. (2008) to obtain estimates of the mass and constraints on the mass profile of the Milky Way, which was based on SDSS DR6 (Adelman-McCarthy et al. 2008).”
Theoretical Challenges in Galaxy Formation (2016, background): “Typically mass estimates are in the range of 1−2×1012M (Bland-Hawthorn & Gerhard 2016; Bovy et al. 2012; Li & White 2008; Watkins, Evans & An 2010; Xue et al. 2008).”
SIMULATIONS OF THE MAGELLANIC STREAM IN A FIRST INFALL SCENARIO (2010, background): “It is, however, unlikely that the rotation curve of the MW remains flat out to such distances (e.g., Xue et al. 2008).”
A-type stars in the Canada–France Imaging Survey – II. Tracing the height of the disc at large distances with Blue Stragglers (2018, background): “As mentioned by Xue et al. (2008), a fraction of photometrically identified BSs can be, in fact, young main-sequence stars.”
The Milky Way’s stellar disk (2013, methodology): “…of the measured flux to an inferred intrinsic luminosity or absolute magnitude, have a well-established track record in the Galaxy, when using so-called standard candles, such as BHB stars (Sirko et al. 2004; Xue et al. 2008) or ‘red clump stars’ in near-IR surveys (e.g., Alves et al. 2002).”
The Milky Way stellar halo out to 40 kpc: squashed, broken but smooth (2011, methodology): “It has been shown (e.g. Clewley et al. 2002; Sirko et al. 2004; Xue et al. 2008) that BHB and BS stars can be separated cleanly on the basis of their Balmer line profiles.”
The Aquila comparison project: the effects of feedback and numerical methods on simulations of galaxy formation (2011, methodology): “The selected halo, Aq-C, has a present-day mass similar to the Milky Way (∼1.6 × 1012 M ; e.g. Dehnen, McLaughlin & Sachania 2006; Smith et al. 2007; Li & White 2008; Xue et al. 2008; Watkins, Evans & An 2010) and has a relatively quiet formation history.”
KINEMATICAL AND CHEMICAL VERTICAL STRUCTURE OF THE GALACTIC THICK DISK. II. A LACK OF DARK MATTER IN THE SOLAR NEIGHBORHOOD, (2012, background): “Indeed, recent observations find only a tiny negative gradient (Xue et al. 2008; Fuchs et al. 2009, ∂V /∂R = −0.85 and −0.006 ± 0.016 km s−1 kpc−1, respectively).”
THINK OUTSIDE THE COLOR BOX: PROBABILISTIC TARGET SELECTION AND THE SDSS-XDQSO QUASAR TARGETING CATALOG (2010, background): “For example, some contaminants for the BOSS quasar target selection are BHB stars, which are very useful for studies of Galactic structure (e.g., Xue et al. 2008), and hypervelocity stars.”
The kinematic connection between galaxies and dark matter haloes (2010, methodology): “Other measurements of the virial mass of the MW using kinematics of halo stars also infer relatively high values: Vopt/V200 = 1.48 +0.25 −0.26 (90% C.I.) (Smith et al. 2007); Vopt/V200 = 1.67 +0.31 −0.24 (2σ) (Xue et al. 2008).”
The dark matter density at the Sun’s location (2010, background): “It appears to decline with radius, with quite an uncertain slope (Battaglia 2005; Xue et al. 2008; Brown et al. 2010) d log V(r)/d log r = −0.20+0.05−0.15 ( R < r < 60 kpc ) .”
Accretion-driven turbulence as universal process: galaxies, molecular clouds, and protostellar disks (2009, methodology): “3 we apply our method to galactic scales and propose that the turbulent velocity dispersion measured in the disk of the Milky Way and other galaxies is caused by accretion streams that originate in or pass through the halo.”
`Skinny Milky Way please', says Sagittarius (2014, methodology): “Attempts to gauge the total mass of the Milky Way have been made using a variety of stellar kinematic tracer populations (see e.g. Smith et al. 2007; Xue et al. 2008; Bovy et al. 2012).”