README_old.md

Astro Scripts

Various astronomy scripts

1. Download DECalS Image Script: decal_image_download.py

   Downloading optical image from DeCALS servers (https://www.legacysurvey.org/decamls/)

   python decal_image_download.py <index> <ra> <dec> <name> <redshift> <fraction_size>

   • <redshift>: set value to 0 when you do not know the redshift
   • <fraction_size>: 1 = 2048px, 2 = 2048/2, 4 = 2048/4; (Increase to zoom in and reduce the file size)

   Example:
   Download jpeg: python decal_image_download.py 1 57.8554 -15.4054 test 0.2 4

   Download FITS file: python decal_image_download.py 1 57.8554 -15.4054 test 0.2 4 --fits

   1.1 Fixed the order of FITS images in order to open with ds9

   Requirements: Need to install aplpy for this code to work.

   python decal_image_download_fits_fixed.py <outfilename_from_first_step.fits>

2. Download SDSS Catalog Data: download_SDSS_catalog_withSciServer.ipynb

   • This code can only be run on SciServer https://apps.sciserver.org/compute/, and cannot be run on your own machine.
   • To get access to the SciServer, You will have to create an account at https://apps.sciserver.org/login-portal/.
   • Please follow the installation steps in the Example-Notebooks to be able to run your own codes https://github.com/sciserver/Example-Notebooks#installation.
   • Once you create a persistent folder in /Storage/<username>/persistent/, upload this code to that folder. The script should work in this environment. Additional Information:
     • One of the main components of the code is using SQL to query the data we want. Here is a quick tutorial on how to use SQL: https://www.w3schools.com/sql/.
     • Description of each column in each SDSS Table can be found here https://skyserver.sdss.org/dr14/en/help/docs/tabledesc.aspx.

3. Download LS DR10 Photometry Script: ls_dr10_catalog_download.py

   • This script queries LS DR10 Tractor catalog via NOIRLab TAP service and extracts multi-band photometry (optical + WISE) within a sky region. Documentation: https://datalab.noirlab.edu/tap

   python ls_dr10_catalog_download.py --ra <ra> --dec <dec> --name <name> --radius <radius>

   Arguments

   • : Right Ascension of target center (in degrees)
   • : Declination of target center (in degrees)
   • : Label for output file name
   • : Search radius in degrees (default = 0.0166667 ≈ 1 arcmin)

   Output

   • CSV file containing:
     • Astrometry (RA, Dec)
     • Optical + WISE fluxes (dereddened)
     • Flux inverse variance
     • Galactic transmission factors
     • Morphology and quality flags

   Query sources around a cluster center: python ls_dr10_catalog_download.py --ra 150.11632 --dec 2.20583 --name clusterA --radius 0.02

   SED Photometry (LS DR10)

   For each band (g, r, i, z, w1, w2, …):

   • Use dereddened flux for SED
     • dered_flux = flux / mw_transmission
   • Flux error
     • sigma_flux = 1 / sqrt(flux_ivar)
     • sigma_dered_flux = sigma_flux / mw_transmission
   • Magnitude
     • mag = 22.5 - 2.5 * log10(dered_flux)
   • Magnitude error
     • mag_err = (2.5 / ln(10)) / (flux * sqrt(flux_ivar))