Thalos12
commented
3 years ago From the message on Slack (June 24):
I have not found a lot of options, but I will summarize them briefly here.
- Hottier et al. (2020) - based on 2MASS + Gaia DR2, covers the plane for |b|<0.24°; angular resolution 0.12° in 1st and 4th quadrant, 0.43° in 2nd and 3rd; max distance varies from 4 kpc (towards the centre) to ~7 kpc (anticentre)
- Schultheis et al. (2014) - based on VVV (-10°<l<10°, -10°<b<5°); angular resolution 6'x6', distance resolution 0.5 kpc; max distance ~10 kpc
- Chen et al. (2013) - VVV + GLIMPSE-II matched with 2MASS; covers -10°<l<10° and |b|<=1° or |b|<=2°; angular resolution 15'x15', distance resolution 1 kpc; reliable distance approx 4<d<8 kpc
Also, there are some maps not centered on the GC.
- Sale et al. (2014): based on IPHAS and covers 30<=l<=215 degrees and |b|<=5 degrees; angular resolution 10' and distance resolution 100pc; reliable distance from ~5 kpc to ~10 kpc.
- Chen et al. (2014): extinction map within 140<l<240 and -60<b<40 degrees; angular resolution 3-9', distance resolution 150 pc; max distance 4 kpc.
- Chen et al. (2019): based on Gaia DR2, covers the whole plane with |b|<=10°; angular resolution 6' and distance resolution 0.2 kpc; maximum distance generally 4 kpc, for some regions up to 6 kpc. [added on June 25]
After the discussion at the hack day on June 24, the map which most likely could be used as a replacement for Marshall et al. (2006) is the Schultheis et al. (2014). The one from Chen et al. (2013) could have been interesting, but has lower coverage and lower angular and distance resolution.
As a whole-plane map, Hottier et al. (2020) could interesting, but its latitude range is too small; at the moment we will not implement it (too many maps to patch together.), but in the future we might include it if after assessing its relevance to our map.
For the rest of the plane, we might implement Sale et al. (2014) since it covers the anticentre.
New method to combine the maps?
We discussed the possibility to change the way we patch the maps together. In facto, for example, the map from Schultheis would not need to be combined with Green's one, because it can reach very far.
We could proceed as follows:
- Use Schultheis where available (bulge), no patching with Green
- Chen for the plane, bulge excluded, patching after 4-6kpc with Green
- Use Green (actually, Bovy's combined 19 map) for the remaining sky
- Drimmel, or something else, for the hole in Green's map (as used on Bovy's combined19 map)
- Planck's map as limit for large distances; maybe exclude the region covered by Schultheis?
We were discussing keeping the number of maps used at a minimum, and here I am listing 5 of them. However, this could solve most of the use cases, provided that the whole map does not show too many inconsistencies where maps meet.
Open questions:
- Where Green, Schultheis and Chen are not present, we use the Drimmel et al. (2003) map. Can we use something else?
- How does Lallement et al fit in this new scheme? Do we use it for small distances? Might be a replacement for Drimmel if interpolated to Planck for distances larger than maximum?
[Edited after discovering Chen et al. (2019) extinction map]
(If we decide there's time to do this usefully before the April 15th deadline!)
There are a few alternative 3D reddening maps available in the inner plane, which might provide useful improvements since Marshall et al. (2006). VVV in particular should be a good source. Example: Schultheis et al. (2014 Vizier).
Schultheis et al. 2014 gives A_Ks and A_Hs (plus associated uncertainties!) with 0.5kpc distance resolution in the inner Southern bulge, which may be useful. Or, there may be even better 3D maps with wider sky coverage.