These angular masks were created by the ALHAMBRA-survey Team. The corresponding ALHAMBRA data release (v1.0, Nov 2013) is described in Molino et al. (2014), and can be accessed at https://cloud.iaa.csic.es/alhambra/.
DOWNLOAD the mask file.
The masks describe the angular selection function of the ALHAMBRA survey. They are described in Sect. 3.1 of Arnalte-Mur et al. (2014), see that reference for details. They are mostly based on the detection image (synthetic F814W band). In brief, we have masked out the following areas:
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Areas with low exposure time
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Regions around bright stars (in the Tycho-2 catalogue)
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Regions around saturated objects, and obvious defects in the image
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Regions with bad photometric quality in >=3 ALHAMBRA bands
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Small overlap between frames
These masks take a conservative approach, with the aim of studying large-scale structure, they may not be optimal for other applications. Use your best judgement, and contact us if in doubt.
How to use the masks:
The masks were created using the Mangle software, Swanson et al. (2008), and are written in its polygon format. You will need to install this software in order to use them. Please, refer to Mangle's webpage to for help on using that software.
Each of the files correspond to a single ALHAMBRA frame (each ALHAMBRA field is composed of 4 or 8 frames, see Appendix A in Molino et al. 2014 for details). The names follow the same convention as in the data release.
Any overlap between frames has ben eliminated, so you can directly combine the masks from several frames (e.g. to create a complete field's mask) using the Mangle tools.
Catalogue selection:
If you want to use the public ALHAMBRA data and these masks, the first step should be to select only the objects in the catalogues that fall inside the angular mask. You can use the included Python script alhambra_mask_selection.py to achieve this.
Requisites
To run the script, you will need to have Python, NumPy and Mangle installed. The environment variable MANGLEBINDIR should point to Mangle's bin directory.
Running the script
We assume you have the data catalogues (as downloaded from https://cloud.iaa.csic.es/alhambra/) in a directory named 'inputcats', and the mask files in a directory named 'masks'. Then you can run the script as
python alhambra_mask_selection.py [FrameName]
where [FrameName] is the name of the ALHAMBRA frame in which you want to select the catalogue. For example, running
python alhambra_mask_selection.py F02P01C02
will create a new file alhambra.F02P01C02_masksel.cat containing only the objects in the catalogue that fall inside the angular mask (it will produce also a log file).
A few options regarding the names of input/output files, etc. can be changed directly at the beginning of the code.
Terms of use
You are free to use these angular masks for any purpose, under the condition that you cite both Molino et al. 2014 (where ALHAMBRA data is described) and Arnalte-Mur et al. 2014 (where the definition of these masks is described).
Contact
If you have any problem or question regarding these masks, please contact Pablo Arnalte-Mur pablo.arnalte-mur@durham.ac.uk
References:
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