REDDENING AND EXTINCTION TOWARD THE GALACTIC BULGE FROM OGLE-III: THE INNER MILKY WAY'S RV ∼ 2.5 EXTINCTION CURVE

By D. Nataf, A. Gould, P. Fouqué, O. Gonzalez, Jennifer A. Johnson, J. Skowron, A. Udalski, M. Szyma'nski, M. Kubiak, G. Pietrzy'nski and 4 more. 2012

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We combine VI photometry from OGLE-III with VISTA Variables in The Via Lactea survey and Two Micron All Sky Survey measurements of E(J − Ks) to resolve the longstanding problem of the non-standard optical extinction toward the Galactic bulge. We show that the extinction is well fit by the relation AI = 0.7465 × E(V − I) + 1.3700 × E(J − Ks), or, equivalently, AI = 1.217 × E(V − I)(1 + 1.126 × (E(J − Ks)/E(V − I) − 0.3433)). The optical and near-IR reddening law toward the inner Galaxy approximately follows an RV ≈ 2.5 extinction curve with a dispersion , consistent with extragalactic investigations of the hosts of Type Ia SNe. Differential reddening is shown to be significant on scales as small as our mean field size of 6′. The intrinsic luminosity parameters of the Galactic bulge red clump (RC) are derived to be . Our measurements of the RC brightness, brightness dispersion, and number counts allow us to estimate several Galactic bulge structural parameters. We estimate a distance to the Galactic center of 8.20 kpc. We measure an upper bound on the tilt α ≈ 40° between the bulge's major axis and the Sun–Galactic center line of sight, though our brightness peaks are consistent with predictions of an N-body model oriented at α ≈ 25°. The number of RC stars suggests a total stellar mass for the Galactic bulge of ∼2.3 × 1010 M☉ if one assumes a canonical Salpeter initial mass function (IMF), or ∼1.6 × 1010 M☉ if one assumes a bottom-light Zoccali IMF.

Subfields: Astronomy and Astrophysics, Instrumentation

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Citations in the corpus

The Galaxy in Context: Structural, Kinematic, and Integrated Properties (2016, background): “For Ca+13, no error was given; we estimated one from the metallicity dependence of the red clump giant calibration by Nataf et al. (2013).”
ON THE SOURCE OF THE DUST EXTINCTION IN TYPE Ia SUPERNOVAE AND THE DISCOVERY OF ANOMALOUSLY STRONG Na i ABSORPTION (2013, background): “Similarly low values of RV have been observed in a few other high Galactic latitude clouds (Larson & Whittet 2005) and toward the Galactic bulge (Udalski 2003; Nataf et al. 2013).”
Predictions of the WFIRST Microlensing Survey. I. Bound Planet Detection Rates (2018, background): “This was confirmed by comparing the red clump star counts of Nataf et al. (2013) as a function of (`, b) to the total stellar mass of the BGM1106 bulge.”
Mapping the three-dimensional density of the galactic bulge with VVV red clump stars (2013, methodology): “In the I-band, the RGBB is 0.74 mag fainter than the RC, and the number of stars in the RGBB is ∼ 20% of RC stars (Nataf et al. 2013).”
OBSERVING THE NEXT GALACTIC SUPERNOVA (2013, background): “Dust in lower extinction directions towards the bulge show evidence for an RV significantly below RV = 3.1 (Nataf et al. 2013), but if extinction is low, the particular value of RV is unimportant.”
The structure of the Milky Way's bar outside the bulge (2015, methodology): “To the magnitude distribution in each field we attempt to fit a Gaussian representing the red clump together with a exponential background (Stanek 1995; Nataf et al. 2013): N(µ) = NRC σRC √ 2π exp [ −1 2 ( µ−µRC σRC )2] +AexpB(µ−µRC) .”
Target Selection for the SDSS-IV APOGEE-2 Survey (2017, background): “They span a very small range of absolute magnitude and color (e.g., Girardi & Salaris 2001), thus making them invaluable as standard candles (and standard crayons) to meausure stellar distances and foreground dust reddening (e.g., Stanek et al. 1997; Benjamin et al. 2005; Nataf et al. 2013).”
Synthetic stellar photometry – I. General considerations and new transformations for broad-band systems (2014, background): “If RV = 2.5, which seems to be representative of selected directions towards the bulge (Nataf et al. 2013), the aforementioned numbers would change to 3.188 c© 0000 RAS, MNRAS 000, 000–000 and 3.164 (metal-poor subgiant), 3.123 and 3.108 (solar metallicity giant), and 3.211 and 3.187 (solar…”