1 - Usage

By using GALExtin, you can either obtain the interstellar extinction/reddening towards any given position in our Galaxy providing the coordinates and distance (input always in kpc) or an integrated extinction/reddening towards a line of sight. In the latter case, you should only provide the coordinates, at least for estimates of Burstein & Heiles, Schlegel, among others; these mentioned are most used for extragalactic studies.

The coordinates accepted by GALEXtin are both Equatorial (J2000) and Galactic in degrees. User should select the right representation in the query, the default is galactic coordinates. Further, you can either provide the Galactic coordinates (l,b) or Equatorial (RA,DEC) of a single object (direction) or a list of coordinates (+ distance) in an ASCII file separated by spaces as presented below. For technical reasons at the moment, only lists with less than 1,000 “directions” and for one model/map per run are accepted.

- (l,b,distance) OR (RA,DEC,distance)

20.120 5.123 2.000

30.850 0.528 2.533

40.055 -1.254 0.125

In the case of 3D maps/models. Be careful to provide distances for all coordinates. If you have not to distance for a given pair of coordinates, delete this line.

Input distances are always in kpc.

As mentioned above, some maps provide the integrated extinction/reddening up to a given distance. So, the input distance does not affect the GALExtin input.

In 3D extinction/reddening estimates, GALExtin also provides the input distance and the nearest output distance. Check whether this is appropriate for your purpose.

2 - Models/maps available at GALExtin

- Amôres & Lépine (2005): Models A1 (Axisymmetric) for both with and no-fine tunning option (See Section 4.1) and S (Spiral). Coverage: All-sky. Based on gas distribution in our Galaxy.

- Amôres & Lépine (2007): Model A2. It improves Model A1 for intermediate and high Galactic latitudes.

- Burstein & Heiles (1978,1982): Based on HI galaxy counts. Coverage: most of b, for |b| > 10º.

- Schlegel et al. (1998) maps: Based on DIRBE/COBE maps. Coverage: all-sky. It does not provide good results for low Galactic latitudes.

- Drimmel, Cabrera-Lavers, López-Corredoira (2003) Model. Based on DIRBE/COBE and dust distribution provided by Drimmel & Spergel (2001). Coverage: All-sky.

- Marshall et al. (2006) maps. Based on 2MASS star counts and Besançon Galaxy Model. Coverage: Inner Galaxy (|l| < 100º) and low latitudes (|b| < 10º).

- Chen et al. (2013) map. Based on VVV/2MASS star counts and Besançon Galaxy Model. Coverage: Galactic bulge.

- Schultheis et al. (2014) map. Mapping the Milky Way bulge at high resolution: the 3D dust extinction, CO, and X factor maps. Coverage: Galactic bulge.

- The Planck Dust Model for All-Sky: Available E(B-V) and Tau_353. Based on Planck observations Coverage: All-Sky.

- Sale et al. (2014): Based on IPHAS data. Coverage: entire northern 30° < l < 230° (for |b| < 5°).

- Chen et al. (2014): Based on LAMOST data. Coverage: 140° < l < 240° for -60° < b < 40°.

- Schlafly et al. (2014): Based on Pan STARSS1. Coverage: Sky north of declination -30° for distance < 4.5 kpc.

- Bayestar15, Bayestar17, Bayestar19 (Green et al. 2015, 2018, 2019) : Based on Pan-STARSS1, 2MASS, Gaia. Coverage: All-Sky.

- Lenz et al. (2017): Base on HI column densities. Coverage: 39% of the sky.

- HI4PI Collaboration (2017): Based on HI column density. Coverage: All-Sky.

- Gontcharov (2017): 3D stellar reddening map from 2MASS photometry: An improved version. Coverage: All-sky.

- Chen et al. (2019): Based on 2MASS, Gaia and Wise data. Coverage: 7,000 sqr deg.

- Soto al. (2019): Based on 2MASS, WISE and VVV data. Coverage: 295° < l < 350° (for |b| < 2°).

- Surot et al. (2020): Mapping the stellar age of the Milky Way bulge with the VVV. III. High-resolution reddening map. Coverage: Galactic bulge (|l| < 10° for -10° <= b <= 5°).

- Gontcharov & Mosenkov (2021): Gaia DR2 giants in the Galactic dust - II. Application of the reddening maps and models Coverage: All-Sky.

- Guo et al. (2021): Three-dimensional Distribution of the Interstellar Dust in the Milky Way. Coverage: 14,000 sqr deg (SMSS).

- Zhang & Kainulainen (2022): Dust extinction map of the Galactic plane based on the VVV survey data. Coverage: VVV survey region.

3- What is the coordinate format?

Coordinates should be provided (only numbers with ‘.’ separator) in degrees either for Galactic or Equatorial coordinates. The values for Galactic longitude should range from 0 to 360, instead of +180 to -180 degrees. Distances are in units of kpc.

For a list with coordinates and distances. Be careful to provide distances for all coordinates. If you have not to distance for a given pair of coordinates, delete this line.

4- How the data file input should be formatted?

Two or three columns (in the case of 3D models) separated by tab or space. The two first columns are Galactic longitude, latitude or RA, DEC and distance (in kpc) as shown above.

5- What are the coordinate systems that GALExtin accepts?

GALExtin works basically with Galactic coordinates. But, if you prefer to use Equatorial coordinates, GALExtin converts them into Galactic coordinates. In this case, you should select the input coordinate in the main form.

6- Validation

For the sanity check of values obtained by GALExtin using several maps/models and those obtained outside GALExtin, please see page.

7 – Acknowledgements

At the moment, GALExtin provides extinction for the models/maps below, but we plan to increase this list, also to increase the number of available capabilities. If you use our service for your publication, we kindly request you to cite the paper below as well as the reference to the model/map used as provided in the output file of your request.

Amôres et al. 2021, MNRAS, 508, 1788-1797

8 – Known Issues

For the moment, the execution of GALExtin for Bayestar maps it is taking around two minutes what is due to charge the large maps in the memory. Thus, to better use the resources we recommend to charge one unique list with the coordinates and distances. We have planned to improve our hardware but unfortunately it’s on hold due to pandemic.



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