Collected by Carine Babusiaux
To be able to do this tutorial, you need basic knowledge on GACS, astroquery.gaia, and GaiaXPy :
astroquery.gaia documentation page: https://astroquery.readthedocs.io/en/latest/gaia/gaia.html
GACS demo and tutorials: https://www.cosmos.esa.int/web/gaia-users/archive/help. In particular:
GaiaXPy tutorials: https://gaia-dpci.github.io/GaiaXPy-website/
If not already done, install astroquery and GaiaXPy.
!pip install astroquery
!pip install gaiaxpy
Use astroquery.gaia to have the list of all the tables available within GACS using Gaia.load_tables
It is not necessary for the following, but you can login to your GACS user space.
Once you are loggued in, if you already have some tables of your own, you should now be able to see them using the same commands used above. You can also upload a file to your user space and for example run a positional cross-match with the Gaia tables. Note that you need to ensure that you do not have user tables with the same names as the ones you will be using here, else you would need to delete your old tables. Once loggued in, you will see also your tables and the ones shared with you with the Gaia.load_tables command.
Look if the binary star GJ473 is resolved by Gaia. It's Simbad position need to be propagated to the Gaia epoch using EPOCH_PROP_POS, see https://www.cosmos.esa.int/web/gaia-users/archive/writing-queries/#epoch_prop. You can adapt for this the "Basic Search" GUI query of]( the Gaia Archive (SEARCH/Basic).
Perform an asynchronous query (asynchronous rather than synchronous queries should be performed when retrieving more than 2000 rows). Asynchronous queries save results at server side and depends on the user files quota. These queries can be accessed at any time. For anonymous users, results are kept for three days. Queries retrieved results can be stored locally in memory (by default) or in a file.
Get the parameters ‘alphafe_gspspec’ and ‘mh_gspspec’ for the first 1000 sources within the GSPSpec “High quality sample” as defined in Annex B of Gaia Collaboration, Recio-Blanco A. et al. 2023 and at high galactic latitude. Do you see the thin and thick disk signature on the alphafe_gspspec versus mh_gspspec plot?
With such an asynchronous query, your job is stored on your user account, so don't forget to remove it once you are done.
Within the DR3 table nss_two_body_orbit, the field nss_solution_type gives the type of two body orbit solved for. Find the number of sources of each nss_solution_type.
The XP sampled and RVS products consist in a table that is serialised following the IVOA Spectrum Data Model (see for details the DataLink Products serialisation tutorial. As a result, a number of parameters (including the source_id) associated to these files is stored in the table metadata.
Find the RVS Spectra data for this Cepheid among all the downloaded datalink, extract it's metadata and export the table contnet to an Astropy Table object and print it's first 5 lines.
Download the RVS spectra for the three following sources: Gaia DR3 25276196070213760 (a solar-type star), Gaia DR3 2267193732388859776 (a hot star) and Gaia DR3 5611353606626845184 (a very cool star). Plot the three spectra and compare.
Retreive the XP spectra of two white dwarfs: Gaia DR3 3489719481290397696 (DA) and Gaia DR3 691116660913783936 (DB) and plot them together. Look in particular at the difference at the Balmer line positions.
For this, use GaiaXPy to directly download the datalink XP_CONTINUOUS and calibrate it towards a sampled spectra with the default sampling (XP_SAMPLED equivalent) using the calibrate method.
Look at the effect of changing the sampling of the XP spectra through the calibrate method on the star Gaia DR3 2342674179138734080 for which you will compare the default sampled spectra and the spectra with a log scale sampling. Use GaiaXpy plot_spectra to see the 1 sigma area.
If you do not want GaiaXPy to load the XP_CONTINUOUS spectra twice for this exercice, download the XP_CONTINUOUS yourself and give it as input to the GaiaXPy calibrate method.
Find all the Photometric Systems implemented within GaiaXPy for synthetic photometry generation.
Produce synthetic photometry from the first 5 stars with XP Spectra available within Gaia DR3 in the Stromgren and SDSS pass bands.
astroquery.gaia documentation page: https://astroquery.readthedocs.io/en/latest/gaia/gaia.html
GACS demo and tutorials: https://www.cosmos.esa.int/web/gaia-users/archive/help. In particular:
GaiaXPY tutorials: https://gaia-dpci.github.io/GaiaXPy-website/tutorials/