1 - Usage

By using GALExtin, you can either obtain the interstellar extinction (Av) towards any given position in our Galaxy providing the coordinates and distance or an integrated extinction 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

If you do not provide the distance, GALExtin will assume extinction at infinity.

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.

- 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: 140º < 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.

- 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°).

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.

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 proceeding below as well as the reference to the model/map used as provided in the output file of your request.

Amôres, E. B., Moitinho, A., Arsenijevic, V., Sodré, L., 2012, Proceedings of Symposium 5 of JENAM 2010, pp 93-95. DOI: 10.1007/978-3-642-22113-2_12

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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