RainbowLasso

RainbowLasso compiles reliable ultraviolet to infrared for modelling stars, galaxies and Active Galactic Nuclei from public all-sky astronomical surveys.

How it works

Understanding the stellar population in galaxies requires constraining a model with reliable multi-wavelength (ultraviolet to infrared) flux measurements. Since galaxies are extended, to model the same object at all wavelength, the same aperture needs to be extracted. This is called matched aperture. For point sources (stars or distant quasars), measuring the flux weighted by the survey point-spread-function provides the best constraints.

Depending on whether the source is extended or point-like, information from the Legacy Survey multi-wavelength source fitting from optical to mid-infrared, either PSF-like photometry or a total flux based on an extraction aperture is used. Only sources within the Legacy Survey area are handled.

RainbowLasso fetches and calculates fluxes from these surveys:

GALEX (far-UV and near-UV),
optical (griz bands from Legacy Survey),
near-infrared (JKH from VISTA hemisphere survey and UKIDSS)
infrared (WISE W1,W2,W3,W4, deblended by Legacy Survey)

RainbowLasso takes a input FITS catalog with coordinates (id, RA, DEC) and automatically fetches the necessary photometry from publicly available sources (noirlab, vizier). Additional input catalog columns are copied to the output and are not uploaded anywhere. The output files are usable with LePhare, Cigale (TODO) and GRAHSP.

Features

Milky Way attenuation by dust is corrected for each band up until the near-infrared. The E(B-V) is taken from here and for other wavelengths as listed to the COSMOS2015 Laigle+ paper.
Reliable flux errors are computed. If needed, they are conservatively estimated from magnitude errors.
Unreliable flux estimates are discarded, indicated by flags on blending and image fitting problems
Discards blended or problematic photometry in GALEX (artifact and extraction flag, magnitude error)
Discards blended or problematic photometry in LS&WISE (fracin, fracflux)
Provides upper limits for blended WISE cases * conservative 3 sigma upper limits are computed for WISE3&4 based on the total flux of all nearby sources (fracflux) and the error bars.
Missing information (lacking information) is indicated (e.g. -99 entries).
Automated
For a clean sample, you can sub-select sources flagged "isolated"

Prerequisites

You need to have the programs installed:

stilts
make

and the following python libraries:

requests_cache, astropy, numpy, pandas, tqdm
astro-datalab (see noirlab)

which you could get with something like:

pip install requests_cache astropy numpy pandas tqdm astro-datalab

Usage

Prepare an input fits file with columns 'id', 'RA' and 'DEC'. Additional columns are fine.

If for example the input file is dr16QWX_selection.fits, then run:

make dr16QWX_selection_all_lite.fits

Files can also be outside the RainbowLasso directory.

In that case you can run from the RainbowLasso directory:

$ make path/to/data/dr16QWX_selection_all_lite.fits

Or you can run from the data directory:

$ make -C path/to/RainbowLasso/ dr16QWX_selection_all_lite.fits

The Makefile contains the steps performed to fetch the various multiwavelength surveys.

Quality control

Create a visualisation of the errors and fluxes:

make dr16QWX_selection_lite.fits_errors.pdf dr16QWX_selection_lite.fits_fluxes.pdf

Examples are uploaded to this repository.

How to read the diagnostic plot:

each page is a filter.
fluxes.pdf compares the flux (mJy) from one band to the next. If the spectrum is relatively flat, and bands are close together, they should follow the 1:1 line.
errors.pdf compares the flux error to the significance of the value (value / error ratio).
The previous filter is shown in gray. Within one telescope and filter system, the error properties should be comparable.

TODO

☐ discard blended or problematic photometry in VHS
☐ discard blended or problematic photometry in UKIDSS
☐ provide upper limits for VHS, UKIDSS (need coverage information for that)
☐ improve efficiency of noirlab fetching of aperture fluxes. They were not able yet to suggest a better working solution.

To add more surveys, contributions are welcome.

Scope: The current scope are large-area surveys (ten to ten-thousands of square degrees), which provide state-of-the-art photometry to an already-existing selection of sources. Cross-matching (see NWAY) or image analyses are outside the scope of this project.

Contributors

Suraj D Shankar
Mara Salvato
Johannes Buchner
Isabelle Gauger

Citing

Cite the accompaning paper.
You can also include the repository URL as a footnote.
Cite the relevant data products. See the accompaning paper for a list of references.

Licence

AGPL-3 (see LICENCE file).

Logo

The logo is based on work by Ivan Abirawa, Those Icons and Freepik.

JohannesBuchner / RainbowLasso