Here we provide code to help access and visualise the galaxy images contained in the BlueTides Mock Image Catalogue.
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bluetides_mock_catalogue_functions.py: helper code to read, access and select galaxies within the catalogue, and plot their images
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add_noise.py: helper code to add noise to the images from the catalogue based on exposure time, and plot the result
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jwst_nircam_depths.csv: Aperture flux limits for a range of JWST NIRCam filters, for exposures from 0.55 to 10ks, spaced by 0.05ks. Taken from Figure 1 of JDocs. Recommended for full use of the noise generation code add_noise.py.
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plot_selected_galaxies.ipynb: example notebook walking through how to use the functions in bluetides_mock_catalogue_functions.py. Recreates Figures 2 and 3 from the Mock Catalogue Release paper.
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plot_selected_galaxies.ipynb: example notebook walking through how to use the functions in add_noise.py to add noise to the mock images.
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test_plot_galaxies.py: pytest file for testing that bluetides_mock_catalogue_functions.py works as intended.
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test_add_noise.py: pytest file for testing that add_noise.py works as intended.
Using this code will require files from the BlueTides Mock Image Catalogue, the catalogue csv file 'hlsp_bluetides_multi_multi_all_multi_v1_sim.csv', which contains the galaxy properties, as well as your desired fits files (e.g. various redshifts and telescope/filters) depending on your science goals. The specific fits files required to run the example notebooks are listed in the notebooks. Links for data access are given below.
Full details of the BlueTides Mock Image Catalogue files and structure are provided below.
The BlueTides Mock Image Catalogue is publicly available as a High Level Science Product (HLSP) via the Mikulski Archive for Space Telescopes (MAST) archive at doi:10.17909/er09-4527. Note that the current version v1 of the catalogue is the version used in Marshall et al. (2022).
When using this data, please cite both the release paper (https://arxiv.org/abs/2206.08941) and the MAST DOI linking to the catalogue (https://doi.org/10.17909/er09-4527).
HLSP Contributor: Madeline Marshall, NRC Herzberg Astronomy & Astrophysics
(Madeline.Marshall at nrc-cnrc.gc.ca)
HLSP Authors: Katelyn Watts, Stephen Wilkins, Tiziana Di Matteo, Jussi K. Kuusisto, William J. Roper, Aswin P. Vijayan,
Yueying Ni, Yu Feng, Rupert A.C. Croft
HLSP Date: 2022-08-01
Version: 1
This catalogue contains mock images of ~100,000 galaxies from the BlueTides hydrodynamical simulation at z=7,8,9,10,11 and 12. This includes mock images of these galaxies with the James Webb, Hubble, Roman, and Euclid Space Telescopes, as well as Subaru and VISTA.
This v1.0 release of the BlueTides Mock Image Catalogue contains:
- 540 fits image files, containing images of all of the galaxies for each of the redshift, telescope, and PSF-option combinations
- 1 csv table containing assorted physical and observed properties of each BlueTides galaxy in the catalogue
- This "README" file
The primary catalogue files have names of the form:
hlsp_bluetides_TELESCOPE_INSTRUMENT_zREDSHIFT_FILTER_vVERSION_sim-[PSF,NOPSF].fits
as discussed in detail below. The file format is FITS with multiple image extensions.
A table showing the available telescope configurations, alongside key image properties, is shown below.
| Telescope | Instrument | Filters | Pixel Scale ('') | Image FOV (pkpc) |
|---|---|---|---|---|
| JWST | NIRCam (SW) | F090W, F115W, F150W, F200W | 0.0155 | 6 |
| NIRCam (LW) | F277W, F356W, F410M, F444W | 0.0315 | 6 | |
| MIRI | F560W, F770W | 0.055 | 6 | |
| HST | WFC3 | F105W, F125W, F140W, F160W | 0.065 | 6 |
| Roman | WFI | F087, F106, F129, F146, F158, F184 | 0.055 | 6 |
| Euclid | NISP | Y, J, H | 0.15 | 10 |
| VISTA | VIRCam | Z, Y, J, H, Ks | 0.17 | 10 |
| Subaru | HSC | z, y | 0.085 | 10 |
These observations are created with the SynthObs package for producing synthetic observations. The image creation is described in detail in Marshall et al. (2022). Briefly, each star particle in a galaxy in BlueTides is assigned a spectral energy distribution (SED) using BPASS (version 2.2.1; Stanway & Eldridge 2018) and CLOUDY (Ferland et al. 2017). To create the images the SED from each star particle in the FOV is convolved with the instrument filter transmission curve. The images of the galaxies are made in the 'face-on' direction, defined by the angular momentum of the galaxy particles. The light from each star particle is smoothed adaptively based on the distance to its nearest neighbours.
We consider the FOV of 6x6 kpc around each galaxy, except for Euclid, Subaru, and VISTA, which have much wider PSFs and so require a larger FOV (10x10 kpc) to contain the galaxy emission. The images are binned onto a pixel scale of 0.5 times the native pixel scale. This assumes that given sufficient dithering in the observations, the final image can sub-sample the original pixels by a factor of 2. The resulting image is convolved with the PSF of the instrument. The PSFs are obtained via TinyTim for HST, and WebbPSF for JWST and Roman. Euclid NISP is assumed to have a Gaussian PSF with FWHM of 0.175'' in the Y-band, 0.24'' in J, and 0.28'' in H. Ground-based Subaru and VISTA are assumed to have Gaussian PSFs with FWHM of 0.6'' and 0.66'' respectively, corresponding to the typical site seeing. These images are marked as sim-psf in the collection. We also provide images that have not been convolved with a model PSF, marked as sim-nopsf.
The catalogue images are made without noise, which can be added in post-processing. Code to add noise is available via GitHub.
Each fits file contains all of the galaxies at the specified redshift for the defined telescope/instrument/filter combination.
| Redshift | Number of Galaxies |
|---|---|
| z=7 | 71,052* |
| z=8 | 22,144 |
| z=9 | 5,606 |
| z=10 | 1,279 |
| z=11 | 244 |
| z=12 | 31 |
*Note that to reduce the large file sizes for the z=7 snapshot, we split the z=7 catalogue into 4 separate files, containing 17764, 17763, 17763 and 17762 galaxies. These files are marked as z7-file1, z7-file2, z7-file3 and z7-file4 in the collection.
The filenames show the telescope, instrument, filter, and redshift:
hlsp_bluetides_TELESCOPE_INSTRUMENT_TARGET_FILTER_vVERSION_sim-[PSF,NOPSF].fits
where TARGET = zREDSHIFT if z>7, and TARGET = z7-fileN for N in 1,2,3,4 for z=7.
Example: PSF convolution:
hlsp_bluetides_jwst_nircam_z7-file1_f150w_v1_sim-psf.fits
hlsp_bluetides_jwst_nircam_z8_f150w_v1_sim-psf.fits
No PSF convolution:
hlsp_bluetides_jwst_nircam_z7-file1_f150w_v1_sim-nopsf.fits
hlsp_bluetides_jwst_nircam_z8_f150w_v1_sim-nopsf.fits
These images contain a header file, and then a separate image extension for each galaxy.
- Provides key information about the simulated images in this file
- Contains a dummy array of 1s, with the same shape as the galaxy images.
Example header file:
SIMPLE = T / file does conform to FITS standard
BITPIX = -64 / number of bits per data pixel
NAXIS = 2 / number of data axes
NAXIS1 = 46 / length of data axis 1
NAXIS2 = 46 / length of data axis 2
EXTEND = T / FITS dataset may contain extensions
COMMENT FITS (Flexible Image Transport System) format is defined in 'Astronomy
COMMENT and Astrophysics', volume 376, page 359; bibcode: 2001A&A...376..359H
HIERARCH TELESCOPE = 'JWST ' * The simulated telescope
HIERARCH INSTRUMENT = 'NIRCAM ' * The simulated INSTRUMENT
HIERARCH FILTER = 'F410M ' * The simulated FILTER
HIERARCH FIELDOFVIEW_PKPC = 6 * The width and height of the image in pkpc
HIERARCH FIELDOFVIEW_ARCSEC = 1.50107 * The width and height of the image in arcsec (assuming BlueTides cosmology)
HIERARCH RESOLUTION_PKPC = 0.12591028 * The pixel scale of the image in pkpc
HIERARCH RESOLUTION_ARCSEC = 0.0315 * The pixel scale of the image in arcsec
HIERARCH SUPERSAMPLINGRATE = 2 * The sub-sampling rate of the native pixel scale
HIERARCH REDSHIFT = 7 * The redshift of the snapshot
DOI = '10.17909/er09-4527' * Digital Object Identifier for the HLSP data collection
HLSPID = 'BlueTides' * The identifier (acronym) for this HLSP collection
HLSPNAME= 'BlueTides Mock Image Catalogue' * Title for HLSP project, long form
SIMULATD= T * This is simulated data
HLSPLEAD= 'Madeline Marshall' * Full name of HLSP project lead
HLSPVER = 1 * Version identifier for this HLSP product
LICENSE = 'CC BY 4.0' * License for use of these data
LICENURL= 'https://creativecommons.org/licenses/by/4.0/' * Data license URL
HLSPTARG= 'z7-file1' * zREDSHIFT if z>7, and z7-fileN for N=1, 2, 3, or 4 if z=7.
OBSERVAT= 'hst ' * Simulated observatory for the mock images
TELESCOP= 'hst ' * Simulated telescope for the mock images
INSTRUME= 'wfc3 ' * Simulated instrument for the mock images
FILTER = 'f160w ' * Name of filter used for the mock images
PRODTYPE= 'sim-psf '
* Type of data. sim = simulated data. psf = convolved with model PSF. nopsf = not convolved with a PSF.
BUNIT = 'nJy ' * Brightness unit for array values
END
- Each extension contains an image of a galaxy in BlueTides at that redshift
- The flux is in units of nJy
- The header gives identifiable and useful information about the galaxy
Example image header for the 9th fits extension (the 8th image extension):
XTENSION= 'IMAGE ' / IMAGE extension
BITPIX = -64 / number of bits per data pixel
NAXIS = 2 / number of data axes
NAXIS1 = 46 / length of data axis 1
NAXIS2 = 46 / length of data axis 2
PCOUNT = 0 / required keyword; must = 0
GCOUNT = 1 / required keyword; must = 1
HIERARCH GALAXYINDEX = 7 * The 8th galaxy (indexes from 0)
HIERARCH MASS_SOLARMASSES = '1.177723e+09' * The solar mass measured from BlueTides, in solar masses
HIERARCH FLUX_NJY = '41.73964' * The total flux in this image, in nJy
END
Alongside the fits files containing the galaxy images, we provide a table of galaxy properties for use when accessing galaxies within the catalogue, 'hlsp_bluetides_multi_multi_all_multi_v1_sim.csv'. This one table contains all of the relevant properties for the galaxies at each redshift, and in each telescope/instrument/filter combination.
The table columns are:
redshift * The redshift snapshot that the galaxy is in
fileNumber * If z=7, gives the file number (1,2,3,4) in which the galaxy is located. If z>7, this is set to 0 as this is redundant.
extensionNumber * The fits file extension which corresponds to this galaxy in the relevant fits file. For z>7, this is 1 greater than the index, as the first fits extension is the header. This is particularly important for z=7 where the galaxies are split into 4 files.
stellarMass * Galaxy stellar mass in solar masses
BHmass * Central black hole mass in solar masses
BHluminosity * Intrinsic AGN luminosity, calculated from the black hole accretion rate, in erg/s
haloMass * Friends-of-friends halo mass in solar masses
lum_FUV * FUV (1500 Angstrom) luminosity in erg/s/Hz
flux_jwst.nircam.f090w * Total flux in the image, for the specified telescope.instrument.filter (all lower-case), in nJy
radius_jwst.nircam.f090w * Effective half-light radius of the galaxy as measured from the image, for the specified telescope.instrument.filter (all lower-case), in pkpc
... * [all available telescope.instrument.filter combinations]
flux_spitzer.irac.ch1 * Total flux in a 10x10 kpc FOV image with Spitzer IRCA Channel 1, in nJy (these images are not provided in the catalogue as all galaxies are unresolved)
flux_spitzer.irac.ch2 * Total flux in a 10x10 kpc FOV image with Spitzer IRCA Channel 2, in nJy (these images are not provided in the catalogue as all galaxies are unresolved)
For details on the calculation of these properties, see the Mock Catalogue Release paper Marshall et al. (2022) as well as Marshall et al. 2022 particularly for the galaxy size calculation.
Example code using this table to select galaxies from the catalogue fits files is available via GitHub.