Dust Maps

Pixel Lookup

The following applies only to users at Berkeley or Princeton. At other institutions, you must download your own copy of the maps.

IDL interface:

You will need to include the dust procedures in your IDL path. At Berkeley you would add the following to your .cshrc or .idlenv file:

setenv DUST_DIR /deep0/ftp/pub/dust
setenv IDL_PATH ${IDL_PATH}:+/deep0/ftp/pub/dust/CodeIDL

At Princeton, you would add the following:

setenv DUST_DIR /u/schlegel/dustpub
setenv IDL_PATH ${IDL_PATH}:+/u/schlegel/dustpub/CodeIDL

Simple examples follow. For the full range of options available, please read README.IDL. Also available are routines to convert to Galactic coordinates.

Examples:

Read the reddening value E(B-V) at Galactic (l,b)=(121,-21.5), interpolating from the nearest 4 pixels, and return result in VALUE.

IDL> value = dust_getval(121, -21.5, /interp)
IDL> print, value
0.2926

In this example, the returned value is E(B-V) = 0.2926 mag.

You may wish to know if there are any mask bits set for this position. The mask will be translated to English if you write it to a file:

IDL> value = dust_getval(121, -21.5, map='mask', outfile='out.dat')
IDL> $cat out.dat
121.000 -21.500 2hcons OK OK OK OK big_obj OK

This will report "2hcons", signifying that IRAS only scanned this position twice (out of a possible 3 HCONs). Also, the "big_obj" flag is reported as set, signifying that this position falls near the LMC, SMC or M31 (the latter in this case).

Check the Burstein-Heiles reddening prediction for this same position:
IDL> print, dust_getval(121, -21.5, map='BH')
0.0960500

C (command-line) interface:

Set the following environments at Berkeley:

setenv DUST_DIR /deep0/ftp/pub/dust
setenv PATH ${PATH}:${DUST_DIR}/bin

At Princeton, set the following:

setenv DUST_DIR /u/schlegel/dustpub
setenv PATH ${PATH}:${DUST_DIR}/bin

Simple examples follow. For the full range of options available, please read README.C.

Examples:

Read the reddening value E(B-V) at Galactic (l,b)=(121,-21.5), interpolating from the nearest 4 pixels.

% dust_getval 121 -21.5 interp=y
121.000 -21.500 0.2926

In this example, the returned value should be 0.2926.

You may wish to know if there are any mask bits set for this position:

% dust_getval 121 -21.5 map=mask
121.000 -21.500 2hcons OK OK OK OK big_obj OK

This will report "2hcons", signifying that IRAS only scanned this position twice (out of a possible 3 HCONs). Also, the "big_obj" flag is reported as set, signifying that this position falls near the LMC, SMC or M31 (the latter in this case).

You can also access the Burstein-Heiles reddening maps:

% extone
Enter galactic (l,b):
121 -21.5
0.0960500017

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Web page designers:

David Schlegel, schlegel@astro.princeton.edu
Douglas Finkbeiner, dfink@astro.berkeley.edu
Adam Krigel, adamk@astro.berkeley.edu