Commit c3d58aff authored by Giuseppe Greco's avatar Giuseppe Greco

Update querying and filtering section

parent 5caa070e
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......@@ -107,51 +107,71 @@ which is useful for distinguishing multiple MOCs for different credible levels.
.. figure:: /_static/aladin_fig2.png
:alt: Properties window
.. Querying and Filtering a Galaxy Catalog
---------------------------------------
Singer et al. [#Singer16b]_ discuss a fast algorithm for obtaining a
three-dimensional probability estimates of sky location and luminosity distance
from observations of binary compact object mergers with Advanced LIGO and
Virgo. Combining the reconstructed gravitational wave volumes with positions
and redshifts of possible host galaxies provides a filtered list of sky
location targets to search for the electromagnetic counterpart of the
gravitational wave signal. At present it is not implemented in Aladin a catalog
query by the GW three-dimensional posterior probability distribution. What we
can currently achieve is to query the entire galaxy catalog and, afterwards, to
filter the selection. Here a cut-distance filter is applied taking into account
the marginal distance posterior distribution integrated over the whole sky.
These tasks are efficiently performed in the Aladin Desktop using the data
collections tree and the filter methods as follows.
:menuselection:`Aladin data collections tree --> Select --> click on the
catalog item --> in the popup window check --> by region & MOC`
.. figure:: /_static/aladin_fig3.png
:alt: Aladin data collection tree
Now we can filter the galaxy catalog. From the main menu press
:menuselection:`Catalog --> Create a filter--> Properties --> Advanced mode -->
Or enter your filter definition`
An example about the Aladin filter using as galaxy selection the marginal
distance posterior distribution integrated over the whole sky is reported
below: ``${Dist} > DISTMEAN-DISTSTD && ${Dist} < DISTMEAN+DISTSTD {draw}``. The
posterior mean distance (Mpc) and the posterior standard deviation of distance
(Mpc) are reported in the fits file header with the keywords ``DISTMEAN`` and
``DISTSTD``. Click on ``Apply`` and then ``Export`` to create a new plane
consisting only of sources selected by the filter.
.. figure:: /_static/aladin_filter.png
:alt: Aladin filter
Finally, make thumbnails of the selected galaxies. From the main menu press
:menuselection:`Tool --> Thumbnail view generator` download and select in the
Aladin stack any image background to obtain the corresponding galaxy images.
.. figure:: /_static/aladin_fig4.png
:alt: Thumbnail view generator
Querying and Filtering a Galaxy Catalog
---------------------------------------
Singer et al. [#Singer16b]_ discuss a fast algorithm for obtaining a
three-dimensional probability estimates of sky location and luminosity distance
from binary compact object mergers. Combining the reconstructed gravitational
wave volumes with positions and redshifts of possible host galaxies provides
a filtered list of targets. Aladin does not implemented yet a query by the GW
three-dimensional posterior probability distribution. Currently, the entire
catalog is loaded in a credible region and, afterwards, a cut-distance filter
is applied.
Here we query the galaxies collected in the `GLADE catalog`_ inside the 90%
credible region of GW170817. Next, they will be filtered according with the
marginal distance posterior distribution integrated over the whole sky.
All data sets published in the Virtual Observatory (over 20,000 data sets) are
directly accessible with the left-panel of the main Aladin window.
Such element of the GUI is named :guilabel:`data collections tree`.
The bottom of the :guilabel:`data collections tree` contains a
box (:guilabel:`select`) and the dropdown menu (:guilabel:`from`) to facilitate
archive searches.
In our context that means to type *GLADE* in the box and
choose *-- all collections --* in the dropdown menu. Press :command:`ENTER`
to access to the catalog releases. By click on the corresponding item,
a new contextual window is opened. Taking into account our purpose to query a galaxy
catalog from a specific credible region, we check the box :guilabel:`by region & MOC`.
Press the button :guilabel:`LOAD` to complete the task.
.. figure:: /_static/aladin_fig3.png
:alt: Aladin data collection tree
Now we filter the galaxy list. The posterior mean distance and the posterior
standard deviation of distance are reported in the FITS file header with the
keywords ``DISTMEAN`` and ``DISTSTD``, respectively. In the case under
examination ``DISTMEAN = 38.0 Mpc`` and ``DISTSTD = 7.5 Mpc`` .
Following the `Aladin filter syntax`_, a cut-filter at 1-sigma distance can be
written as ``${Dist} > 30.5 && ${Dist} < 45.5 {draw}``. ``Dist`` is the column
in the GLADE catalog corresponding to the distance in Mpc.
Once the filter is defined, it can be applied as follows.
:menuselection:`Catalog --> Create a filter`.
The :guilabel:`Properties` dialog box contains two tabs; select the
:guilabel:`Advanced mode` tab and copy the filter statement in the main box.
Click on :guilabel:`Apply` and then on :guilabel:`Export` to create a new level
in the Aladin stack consisting only of sources selected by the filter.
.. figure:: /_static/aladin_filter.png
:alt: Aladin filter
Thumbnail View Generator
------------------------
Finally, we make a mosaic of the filtered galaxies.
:menuselection:`Tool --> Thumbnail view generator`.
Here the thumbnails are color composition images of the Digitized Sky Surveys
(`DSS`_).
.. figure:: /_static/aladin_fig4.png
:alt: Thumbnail view generator
You can load additional surveys from the `HiPS list aggregator`_.
As an example, for loading the Two Micron All Sky Survey (`2MASS`_), you just
need to copy and paste in the Aladin :guilabel:`Command` box the **Base URL**
(http://alasky.u-strasbg.fr/2MASS/Color) reported in the `2MASS preview page`_.
.. |apjl| replace:: *Astrophys. J. Lett.*
.. |A&A| replace:: *Astronomy & Astrophysics*
......@@ -161,9 +181,9 @@ which is useful for distinguishing multiple MOCs for different credible levels.
Fernique, P., Allen, et al. 2015, |A&A|, 578, A114.
:doi:`10.1051/0004-6361/201526075`
.. .. [#Singer16b]
Singer, L. P., Chen, H.-Y., Holz, D. E., et al. 2016, |apjl|, 829, L15.
:doi:`10.3847/2041-8205/829/1/L15`
.. [#Singer16b]
Singer, L. P., Chen, H.-Y., Holz, D. E., et al. 2016, |apjl|, 829, L15.
:doi:`10.3847/2041-8205/829/1/L15`
.. _`Aladin Desktop`: https://aladin.u-strasbg.fr/AladinDesktop/
.. _`VizieR`: http://vizier.u-strasbg.fr/index.gml
......@@ -172,4 +192,10 @@ which is useful for distinguishing multiple MOCs for different credible levels.
.. _`script launcher`: https://aladin.u-strasbg.fr/java/Aladin
.. _`GraceDB`: https://gracedb.ligo.org/
.. _`LALinference sky map of GW170817`: https://dcc.ligo.org/public/0157/P1800381/006/GW170817_skymap.fits.gz
.. _`HiPS list aggregator`: https://aladin.unistra.fr/hips/list
\ No newline at end of file
.. _`GLADE catalog`: http://aquarius.elte.hu/glade/index.html
.. _`Aladin filter syntax`: http://cdsweb.u-strasbg.fr/boch/doc/filters.htx
.. _`2MASS preview page` : http://alasky.u-strasbg.fr/2MASS/Color/
.. _`HiPS list aggregator`: https://aladin.unistra.fr/hips/list
.. _`DSS`: http://archive.stsci.edu/dss/index.html
.. _`2MASS`: http://www.ipac.caltech.edu/2mass/
.. _`preview page`: http://alasky.u-strasbg.fr/2MASS/Color/
\ No newline at end of file
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