A 3D Map of Dust from Pan-STARRS 1 Photometry
Gregory Green, Edward Schlafly & Douglas Finkbeiner
UK National Astronomy Meeting
Llandudno, 7 July 2015
Why construct a 3D map of dust?
2D maps already exist
Schlegel, Finkbeiner & Davis (1998)
Limitations of (emission-based) 2D dust maps
- Inadequate for objects in plane of Galaxy, and close-by objects
- Systematics in modeling of dust emission, and conversion to extinction
Some possible uses of 3D dust maps
- Extinction/reddening corrections in plane of Galaxy
- Distances to objects of known reddening
- Inference of Galactic structure: streams, spiral arms, disk scale heights, etc.
- Different types of systematics than dust emission-based maps
What our map looks like...
Looking towards the Galactic anticenter
50 pc orbit about the Sun
Traveling through the Milky Way
Integrated Reddening:
Three Quarters of the Sky
Integrated Reddening:
Galactic anticenter
Integrated Reddening:
$50^{\circ} \leq \ell \leq 100^{\circ}$
Integrated Reddening:
Aquila South
How is the map constructed?
- We have some idea of the what stars should look like
- Stars are reddened by foreground dust
- Each star therefore acts as a tracer of the dust column out to some point in space
- By inferring reddening to hundreds of millions of stars across the sky, we can build up a 3D dust map
Pixelization
Assume all stars in one pixel trace the same reddening column
Model Parameters
| $\hphantom{\mu_{k} ,\,} \Delta E_{j} ,$ | $\ \ j = 1, \ldots , n_{\mathrm{bins}}$ |
| $\mu_{k} ,\,$ $\delta_{k} ,\,$ $\Theta_{k} ,$ | $\ \ k = 1, \ldots , n_{\mathrm{stars}}$ |
$$
\left.
\vphantom{
\begin{align}
\Delta E_{j} \\
\Theta_{k} \\
\Theta_{k}
\end{align}
}
\right\} \Rightarrow \vec{m}_{k}
$$
The Data
- Multi-band photometry of ~800 million stars
- Pan-STARRS 1 grizy photometry
- 2MASS JHKs photometry
Source Density across the Sky
Source Density across the Sky
Source Density across the Sky
Sources per Band
Bands per Source
Comparison with 2D Maps
3D Map Projected to 2D
Residuals with Schlegel, Finkbeiner & Davis (1998)
Residuals with Planck $\tau_{353 \mathrm{GHz}}$ Dust Map
Aquila South
Schlegel, Finkbeiner & Davis (1998)
Aquila South
3D Dust Map at 8 kpc
Aquila South
Residuals
Aquila South
Residuals (stretched)
