How to Use the Galactic Dust Extinction Service
Required fields:
Choose either to enter a single location ("cut out") or upload a table of locations. Then set the image size, and finally set the "statistics area".
- Single location: Enter an object name or
coordinate.
- Upload table: Enter the path and name of the table (which must conform to the
IPAC Table Format).
- Enter the image size of the cutout region (min = 2 deg, max = 37.5 degrees).
Results:
- Single location mode
The results page includes three images: E(B-V) reddening, 100 um intensity, and dust temperature. The image size is specified by the input value, and region statistics based on the target location and a small 5 arcmin radius area encircling it.
The images are displayed as gif images, with a link "Download cutout" to the actual FITS image. The previews include an equatorial coordinate grid, statistics area (green circle) and target location (red cross). Click on "Larger view" to view a zoomed-up version. Click on the image to change the target location to the cursor location. You may also directly view the FITS image using OASIS.
The target location statistics include:
- reference pixel = single pixel value of the target location
Max = maximum pixel value within statistics area
Min = minimum pixel value within statistics area
Mean = mean +- RMS of the pixel distribution within statistics area
For the derived extinction, a separate ASCII table gives the extinction in several bandpasses, ranging from the ultra-violet (0.3 um) to the mid-infrared (Spitzer IRAC bands, 3.6 um to 8.0 um). The filter bandpass, effective wavelength, ratio of extinction to visual extinction, ratio of extinction to reddening, and the extinction per bandpass are specified. The extinction per optical bandpass is based on the extinction laws of Cardelli et al. 1989 and O'Donnell 1994, and the extinction per mid-infrared bandpass is based on the extinction law derived by Lutz et al. 1996. Click on "Extinction in Different Bandpasses". - Table Upload mode
This mode allows the user to specify multiple locations on the sky. Here is an example table. The results page tabulates the basic results for the reddening, 100 um intensity and dust temperature of the input coordinates: location coordinates, image size, target pixel value, mean and standard deviation of the pixel distribution, and the min and max of the pixel distribution.
By clicking on the "image cutout" button, the FITS images for the location may be obtained (see "Cutout mode" above). The results page is also written as an ASCII table; click on "Download table", which includes additional information (e.g., min/max of the location area coordinates). Here is an example of the reddening table in the results page for table upload.
Notes about the service
- See the Cautionary notes.
Science Background
- See the Galactic Dust Extinction Service.
Links
-
Science Background
-
DIRBE/IRAS Dust Maps,
the Schlegel et al. web site. The downloadable data is stored in
regular FITS, but using a polar projection only (type: GLON-ZEA, GLAT-ZEA)
-
CMB Foreground Images -- LAMBDA data products, including allsky
H-alpha maps, HI maps, Galactic Reddening (Schlegel et al dust maps)
-
Schlegel dust maps (HealPIX FITS) and more served from LAMBDA. Note that
the data served here is in HEALPIX format.
-
94GHz Model Dust Map,
Using a combination of COBE and IRAS data, Finkbeiner, Davis &
Schlegel (1999) derived models for thermal dust emission at microwave
and submillimeter frequencies (see
Microwave Dust Emission). This map is based on their best-fit two-component Model#8. See more on this extrapolation method
here and at LAMBDA.
-
NED Dust Extinction Utility
-
Arce & Goodman (1999)
(Caution: this link might crash Internet Explorer)
(ApJ, 512, L135),
who compared the Schlegel et al. results with independent extinction measurments; their results
suggest systematic discrepancy in the Schlegel maps for some regions of the sky (see cautionary notes).
- Atlas of Galactic Neutral Hydrogen by Hartmann & Burton (1997). Interstellar extinction may be derived from the column density of atomic hydrogen; the Dwingloo Survey has ~0.5 degree spatial resolution.
References
- Cardelli, J.A., Clayton, G.C., & Mathis, J. 1989, ApJ, 345, 245.
- Lutz, D., Feuchtgruber, H., Genzel, R., et al.: Astron. Astrophys. 315, L269-L272 (1996)
- O'Donnell, J.E. 1994, ApJ, 422, 1580.
- Schlegel, D.J., Finkbeiner, D.P. Davis, M. 1998, ApJ, 500, 525.
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