Table Description:
This table is available for ADQL queries and through the TAP endpoint.
Resource Description:
For a list of all services and tables belonging to this table's resource, see Information on resource 'Reddening and Extinction maps of the Magellanic Clouds'
This table has an associated publication. If you use data from it, it may be appropriate to reference 2011AJ....141..158H (ADS BibTeX entry for the publication) either in addition to or instead of the service reference.
To cite the table as such, we suggest the following BibTeX entry:
@MISC{vo:mcextinct_exts, year=2009, title={Reddening and Extinction maps of the Magellanic Clouds}, author={Haschke, R. and Grebel, E.K. and Duffau, S.}, url={https://dc.zah.uni-heidelberg.de/tableinfo/mcextinct.exts}, howpublished={{VO} resource provided by the {GAVO} Data Center}, doi = {10.21938/AvlnaD4AvIeK9nIscpF.YA} }
If you use this data, please cite Haschke, R., Grebel, E., Duffau, S., 2011: "New Optical Reddening Maps of the Large and Small Magellanic Clouds", AJ 141, 158, 2011AJ....141..158H
The photometric data of the red clump is provided by the OGLE collaboration.
Part of this research was supported by SFB 881 "The Milky Way System".
The Optical Gravitational Microlensing Experiment (OGLE III) has monitored both Magellanic Clouds in the V and I band. Using the public stellar photometry database of OGLE III in order to derive spatially resolved reddening maps, we subdivide the OGLE III observations of the Large Magellanic Cloud (LMC) in 3174 subfields. The size of the fields varies from 4.5 x 4.5 square arcmin to 36 x 36 square arcmin in order to ensure that each field contains at least 300 stars and no more than 4800 stars. I.e., in dense regions our reddening resolution is higher.
In each of these subfields the mean (V-I) colour of the red clump is determined. A theoretical colour of (V-I):sub:0 = 0.92 mag is adopted for the LMC and subtracted from the measured value. The difference is defined as reddening E(V-I). To provide you directly useable data we calculated the reddening for different filters by adopting Schlegels list of conversion factors (Table 6 in Schlegel et al. 1998, AJ, 500, 525). To use this table the extinction has to be recalculated from E(B-V) to E(V-I). For this purpose we adopted E(V-I) = 1.38 × E(B-V) (Tammann et al. 2003, A&A, 404, 423).
For the Small Magellanic Cloud (SMC) the same procedure is used. The OGLE III data are subdivided into 693 contiguous subfields. The reddening of each subfield is determined adopting a theoretical colour of (V-I)0 = 0.89 mag.
The following table (containing values taken from 1998ApJ...500..525S) shows the laws adopted to compute extinction values in the various bands:
Filter | name | λeff | A/A(V) | A/E(B-V) | A/E(V-I) |
---|---|---|---|---|---|
Landolt | U | 3372 | 1.66 | 5.43 | 3.94 |
Landolt | B | 4404 | 1.32 | 4.32 | 3.13 |
Landolt | V | 5428 | 1.02 | 3.32 | 2.4 |
Landolt | R | 6509 | 0.82 | 2.67 | 1.94 |
Landolt | I | 8090 | 0.59 | 1.94 | 1.41 |
Gunn | g | 5244 | 1.07 | 3.48 | 2.52 |
Gunn | r | 6707 | 0.79 | 2.59 | 1.88 |
Gunn | i | 7985 | 0.61 | 1.99 | 1.44 |
Gunn | z | 9055 | 0.47 | 1.54 | 1.12 |
Stromgren | u | 3502 | 1.6 | 5.23 | 3.79 |
Stromgren | b | 4676 | 1.24 | 4.05 | 2.93 |
Stromgren | v | 4127 | 1.39 | 4.55 | 3.3 |
Stromgren | beta | 4861 | 1.18 | 3.86 | 2.8 |
Stromgren | y | 5479 | 1 | 3.28 | 2.37 |
Sloan | u' | 3546 | 1.58 | 5.16 | 3.74 |
Sloan | g' | 4925 | 1.16 | 3.79 | 2.75 |
Sloan | r' | 6335 | 0.84 | 2.75 | 1.99 |
Sloan | i' | 7799 | 0.64 | 2.09 | 1.51 |
Sloan | z' | 9294 | 0.45 | 1.48 | 1.07 |
If you want to add extinctions to your own tables, use TAP. Our TAP server has the ivo-id ivo://org.gavo.dc/__system__/tap/run. You will need a TAP client to do this. Recent versions of TOPCAT, for example, allow you use TAP. To add a column with the reddening, load the table into TOPCAT and note its id (that's the number in front of the colon in the Table List in TOPCAT's main window; if you've just started TOPCAT, that's 1).
Then, select TAP from the TOPCAT's VO menu, at the bottom ("TAP URL") enter http://dc.g-vo.org/tap and click "Enter Query".
In the resulting dialog, enter:
SELECT ev_i, mine.* FROM mcextinct.exts AS exts JOIN tap_upload.t1 AS mine ON (1=CONTAINS(POINT('ICRS', mine.raj2000, mine.dej2000),exts.bbox))
If your table has id 15, say, change tap_upload.t1 to tap_upload.t15. You will also need to fix the column names for RA and Dec (written as raj2000 and dej2000 here).
To compute extinctions in specific bands, use the factors given in the A/E(V-I) column in the table above above. To, e.g., add the extinctions in Sloan u' and Sloan z', say:
SELECT ev_i*3.74 as A_sloan_u, ev_i*1.07 as A_sloan_z, mine.* FROM mcextinct.exts AS exts JOIN tap_upload.t1 AS mine ON (1=CONTAINS(POINT('ICRS', mine.raj2000, mine.dej2000),exts.bbox))
For batch processing, similar operations can be done with STILTS or GAVO's tapsh. For the latter, you could use a shell script like the following to add an ev_i column to the file named in the first command line argument argument (note the backup); again, you'll need to fix the column names for RA and Dec:
#!/bin/sh cp $1 $1.bak tapsh <<EOF server ivo://org.gavo.dc/__system__/tap/run SELECT ev_i, mine.* FROM mcextinct.exts AS exts JOIN tap_upload.mytable AS mine ON (1=CONTAINS(POINT('ICRS', mine.raj2000, mine.dej2000),exts.bbox)) upload "$1" as mytable run save "$1" EOF
Sorted by DB column index. [Sort alphabetically]
Name | Table Head | Description | Unit | UCD |
---|---|---|---|---|
bbox | Bounding Box | Bounding box for the extinction data | N/A | pos.outline;obs.field |
centerAlpha | RA | Area center RA ICRS | deg | pos.eq.ra;meta.main |
centerDelta | Dec | Area center Declination ICRS | deg | pos.eq.dec;meta.main |
ev_i | E(V-I) | Reddening (color difference between observation and theory, V-I) | mag | phot.color.excess;em.opt.V;em.opt.I |
sig_ev_i | σ(E(V-I)) | Differential reddening calculated as FWHM of the red clump star distribution | mag | stat.stdev;phot.color.excess |
Columns that are parts of indices are marked like this.
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