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A New Photometric Model of the Galactic Bar using Red Clump Giants
Astrophysics of Galaxies · Submitted 26 Mar 2013
abstract compiled · 2026-09-23 · no language-model review
The authors' main claim We use the Markov Chain Monte Carlo (MCMC) method to explore the parameter space and find that the best-fit model is the $E_3$ model, with the distance to the GC is 8.13 kpc, the ratio of semi-major and semi-minor bar axis scale lengths in the Galactic plane $x_{0},y_{0}$, and vertical bar scale length $z_0$, is $x_0:y_0:z_0 \approx 1.00:0.43:0.40$ (close to being prolate).
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The abstract, sentence by sentence
We present a study of the luminosity density distribution of the Galactic bar using number counts of red clump giants (RCGs) from the OGLE-III survey. The data were recently published by Nataf et al. (2013) for 9019 fields towards the bulge and have $2.94\times 10^6$ RC stars over a viewing area of $90.25 \,\textrm{deg}^2$. The data include the number counts, mean distance modulus ($\mu$), dispersion in $\mu$ and full error matrix, from which we fit the data with several tri-axial parametric models. We use the Markov Chain Monte Carlo (MCMC) method to explore the parameter space and find that the best-fit model is the $E_3$ model, with the distance to the GC is 8.13 kpc, the ratio of semi-major and semi-minor bar axis scale lengths in the Galactic plane $x_{0},y_{0}$, and vertical bar scale length $z_0$, is $x_0:y_0:z_0 \approx 1.00:0.43:0.40$ (close to being prolate). The scale length of the stellar density profile along the bar's major axis is $\sim$ 0.67 kpc and has an angle of $29.4^\circ$, slightly larger than the value obtained from a similar study based on OGLE-II data. The number of estimated RC stars within the field of view is $2.78 \times 10^6$, which is systematically lower than the observed value. We subtract the smooth parametric model from the observed counts and find that the residuals are consistent with the presence of an X-shaped structure in the Galactic centre, the excess to the estimated mass content is $\sim 5.8%$. We estimate the total mass of the bar is $\sim 1.8 \times 10^{10} M_\odot$. Our results can be used as a key ingredient to construct new density models of the Milky Way and will have implications on the predictions of the optical depth to gravitational microlensing and the patterns of hydrodynamical gas flow in the Milky Way.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | We present a study of the luminosity density distribution of the Galactic bar using number counts of red clump giants (RCGs) from the OGLE-III survey. | contribution 1.00 | 0.89 | 0.05 | asserted 0.94 |
| s1 | The data were recently published by Nataf et al. (2013) for 9019 fields towards the bulge and have $2.94\times 10^6$ RC stars over a viewing area of $90.25 \,\textrm{deg}^2$. | method 0.64 | 0.05 | 0.02 | asserted 1.00 |
| s2 | The data include the number counts, mean distance modulus ($\mu$), dispersion in $\mu$ and full error matrix, from which we fit the data with several tri-axial parametric models. | method 0.98 | 0.51 | 0.02 | asserted 1.00 |
| s3 | We use the Markov Chain Monte Carlo (MCMC) method to explore the parameter space and find that the best-fit model is the $E_3$ model, with the distance to the GC is 8.13 kpc, the ratio of semi-major and semi-minor bar axis scale lengths in the Galactic plane $x_{0},y_{0}$, and vertical bar scale length $z_0$, is $x_0:y_0:z_0 \approx 1.00:0.43:0.40$ (close to being prolate). | result 0.97 | 0.97 | 0.63 | asserted 1.00 |
| s4 | The scale length of the stellar density profile along the bar's major axis is $\sim$ 0.67 kpc and has an angle of $29.4^\circ$, slightly larger than the value obtained from a similar study based on OGLE-II data. | result 1.00 | 0.92 | 0.09 | asserted 1.00 |
| s5 | The number of estimated RC stars within the field of view is $2.78 \times 10^6$, which is systematically lower than the observed value. | result 0.66 | 0.90 | 0.04 | asserted 1.00 |
| s6 | We subtract the smooth parametric model from the observed counts and find that the residuals are consistent with the presence of an X-shaped structure in the Galactic centre, the excess to the estimated mass content is $\sim 5.8%$. | result 0.99 | 0.97 | 0.13 | hedged possibility 0.91 |
| s7 | We estimate the total mass of the bar is $\sim 1.8 \times 10^{10} M_\odot$. | result 1.00 | 0.95 | 0.18 | asserted 0.99 |
| s8 | Our results can be used as a key ingredient to construct new density models of the Milky Way and will have implications on the predictions of the optical depth to gravitational microlensing and the patterns of hydrodynamical gas flow in the Milky Way. | interpretation 0.92 | 0.35 | 0.15 | hedged possibility 0.84 |
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The paper
Original abstract
We present a study of the luminosity density distribution of the Galactic bar using number counts of red clump giants (RCGs) from the OGLE-III survey. The data were recently published by Nataf et al. (2013) for 9019 fields towards the bulge and have $2.94\times 10^6$ RC stars over a viewing area of $90.25 \,\textrm{deg}^2$. The data include the number counts, mean distance modulus ($\mu$), dispersion in $\mu$ and full error matrix, from which we fit the data with several tri-axial parametric models. We use the Markov Chain Monte Carlo (MCMC) method to explore the parameter space and find that the best-fit model is the $E_3$ model, with the distance to the GC is 8.13 kpc, the ratio of semi-major and semi-minor bar axis scale lengths in the Galactic plane $x_{0},y_{0}$, and vertical bar scale length $z_0$, is $x_0:y_0:z_0 \approx 1.00:0.43:0.40$ (close to being prolate). The scale length of the stellar density profile along the bar's major axis is $\sim$ 0.67 kpc and has an angle of $29.4^\circ$, slightly larger than the value obtained from a similar study based on OGLE-II data. The number of estimated RC stars within the field of view is $2.78 \times 10^6$, which is systematically lower than the observed value. We subtract the smooth parametric model from the observed counts and find that the residuals are consistent with the presence of an X-shaped structure in the Galactic centre, the excess to the estimated mass content is $\sim 5.8%$. We estimate the total mass of the bar is $\sim 1.8 \times 10^{10} M_\odot$. Our results can be used as a key ingredient to construct new density models of the Milky Way and will have implications on the predictions of the optical depth to gravitational microlensing and the patterns of hydrodynamical gas flow in the Milky Way.
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References
How the literature uses it
11 arXiv papers cite this in 36 sentences
Papers citing it · 20 sentences without a confident label
Uses its method or tool 2 papers
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The [ref] bulge model does not include kinematics, so we adopt the component's kinematic model from the [ref] , which applies a Gaussian distribution with a mean velocity and velocity dispersion that vary with Galactic position.
An Updated SynthPop Model for Microlensing Simulations I: Model Description & Evaluation · Stellar Densities & Kinematics · 0.90
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In Chapter [ref] a model of the same form as the Cao et al. [ref] boxy bulge (Eq. [ref]) is used as a component of the parametric model fitted to the spatial distribution of particles at the end of $N$-body simulations.
The Galactic Millisecond Pulsar Population: Implications for the Galactic Center Excess · The Galactic Bulge · 0.87
Uses its data or values 3 papers
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lccccr $R_0$ (in kpc) Measurements 0pt Year Vallée Vallée: Vallée: Independent Reference updateda independenta from 2011a 2011 - - - 7.94 $±$ 0.65 [ref] 2011 - - - 8.07 $±$ 0.35 [ref] 2012 7.7 $±$ 0.4 7.70 $±$ 0.40 - - [ref] 2012 8.0 $±$ 0.8 8.00 $±$ 0.45 8.00 $±$ 0.45 8.00 $±$ 0.45 [ref] 2012 8.0 $±$ 0.4 8.05 $±$ 0.45 - - [ref] 2012 8.3 $±$ 0.4 8.27 $±$ 0.29 8.27 $±$ 0.29 8.27 $±$ 0.29 [ref] 2013 7.6 $±$ 0.6 7.50 $±$ 0.60 7.50 $±$ 0.60 7.50 $±$ 0.60 [ref] 2013 - - - 7.25 $±$ 0.32 [ref] 2013 7.6 $±$ 0.3 7.64 $±$ 0.32 7.64 $±$ 0.32 7.64 $±$ 0.32 [ref] 2013 - - - 7.66 $±$ 0.36 [ref] 2013 - - - 7.73 $±$ 0.36 [ref] 2013 - - - 7.91 $±$ 0.41 [ref] 2013 8.0 $±$ 0.8 7.98 $±$ 0.79 7.98 $±$ 0.79 7.98 $±$ 0.79 [ref] 2013 8.0 $±$ 0.7 8.03 $±$ 0.70 8.03 $±$ 0.70 8.03 $±$ 0.70 [ref] 2013 8.2 $±$ 0.8 8.25 $±$ 0.79 - - [ref] 2013 8.2 $±$ 0.2 8.13 $±$ 0.10b 8.13 $±$ 0.10b 8.13 $±$ 0.10b [ref] 2013 8.3 $±
Median Statistics Estimate of the Distance to the Galactic Center · DATA COMPILATION · 1.00
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The stellar mass of the Galactic bulge of about $10^10 M_⊙$ [ref] is dominated by old stellar populations (> 5 Gyr).
Mind the gap: The discrepancy between simulation and reality drives interpretations of the Galactic Center Excess · Understanding the GeV gamma-ray emission from the GC – a brief review · 0.96
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[ref] are shown in Table [ref].
The effect of kick velocities on the spatial distribution of millisecond pulsars and implications for the Galactic center excess · Results · 0.85
Compares with it 4 papers
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This density is approximately consistent with the axisymmetric average at the same radius of the E3 bulge mode by [ref] and that of the Besançon model.
A Vertical Resonance Heating Model for X- or Peanut-Shaped Galactic Bulges · Summary and Discussion · 0.98
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While there are still quantitative differences, with the best-fit offsets of Ref. [ref] being smaller than those we find in the gamma rays, it is very likely that these are mostly due to gamma-ray correlations with star formation sites along the disk or in the far Galactic East region of the nuclear bulge.
Strong Evidence that the Galactic Bulge is Shining in Gamma Rays · Translation · 0.99
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However, comparing to Cao et al. [ref] , none of our simulations had quite the right bulge parameters.
The Galactic Millisecond Pulsar Population: Implications for the Galactic Center Excess · Discussion and Conclusions · 0.97
Cites it as background 1 paper
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The distribution of RC giants in the bulge is known to be barred [ref] .
VVV Survey Near-Infrared Photometry of Known Bulge RR Lyrae stars: the Distance to the Galactic Center and Absence of a Barred Distribution of the Metal-Poor Population · The spatial distribution of RR Lyrae stars · 0.92
What it cites · 1 sentence without a confident label
Cites as background 1 paper
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Thus barred galaxies offer exciting opportunities to understand gas and dynamical processes in spiral galaxies (see e.g. [ref] for reviews).
Bars and secular evolution in disk galaxies: Theoretical input · Introduction · 0.98
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