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Mission Overview

The MUSE Ultra Deep Field (MUDF)


Primary Investigators: Marc Rafelski, Michele Fumagalli

HLSP AuthorsMitchell Revalski, Marc Rafelski, Norbert Pirzkal, Elisabeta Lusso

Released: 2023-02-08

Updated: 2024-04-05

Primary Reference(s): Revalski et al. 2024, Revalski et al. 2023, Lusso et al. 2023

DOI: 10.17909/81fp-2g44

Citations: See ADS Statistics

Read Me

Source Data:



MUDF Instrument and Filter Coverage

Figure 1: The region of the sky (3.'6 x 3.'6) containing the MUSE Ultra Deep Field, with instrument and filter coverage overlaid. The full field is covered by HST WFC3 F140W direct imaging, with a wide-shallow region (dashed red) and a narrow-deep region (solid red), with the data shown using a linear flux scaling. Additional HST WFC3 observations with the F125W (orange) and F336W (purple) filters are indicated by solid regions, as well as co-spatial archival WFPC2 observations with the F702W (dashed green) and F450W (dashed blue) filters. The depth of the MUSE observations are indicated by magenta contours that start at 90 hours and decrease by powers of three, with the center-most regions reaching a full depth of 120 hours. The locations of the two z~3.22 quasars are indicated by gold stars, which are found within the 30 hour MUSE contour (solid magenta).

MUDF Spectroscopic Targets

Figure 2: The same field of view as Figure 1, showing sources with spectroscopic coverage in WFC3 (1,499 sources) and MUSE (991 sources). The maximum spatial extent of the WFC3 and MUSE spectral regions are shown by the thick orange and magenta regions, respectively. Objects with spectra are shown with apertures equal to six times their Kron radii, and are colored in the following order: sources in orange have only a WFC3 spectrum (550 sources), magenta have only a MUSE spectrum (42 sources), blue have both WFC3 and MUSE spectra (949 sources), and red have a spectroscopic redshift (419 sources). The WFC3 grism disperses the field such that some sources with spectra are located just outside the direct imaging FOV, as seen by sources near the top of the figure, and bright objects without redshifts are primarily foreground stars in our Galaxy. These data provide spectroscopic coverage in at least one instrument for 1,541 sources, yielding 419 confirmed spectroscopic redshifts.

MUDF Sky Compass

Figure 3: A color-composite mosaic of the MUDF utilizing imaging from all five HST filters. The deep central regions highlight numerous distant galaxies as well as foreground stars in our galaxy. Some of these stars show proper motion offsets between the WFC3 observations and the archival WFPC2 data that were acquired twenty years earlier to study galaxy clusters. The upper left portion of the image only has F140W and F336W coverage and hence is primarily red in color. Image Processing: Joseph DePasquale (STScI).


MUDF Grism Spectral Traces

Figure 4: The same as Figure 3 with the addition of the HST WFC3 G141 grism spectral traces for one position angle superimposed on the color-composite mosaic. The spectral traces are color-coded in the dispersion direction from blue (~10,000 A) to red (~17,000 A). The long smooth traces primarily highlight the continuum emission of bright galaxies and stars, with localized knots of bright emission revealing strong emission lines from ionized gas. Image Processing: Joseph DePasquale (STScI).


XMM-Newton mosaic in the 0.5-7 keV band of the MUDF field
XMM-Newton Mosaic

Figure 5: An XMM-Newton 0.5 - 7 keV band mosaic of the pn, MOS1, and MOS2 detectors, with detected sources shown in white circles. The area marked with the white solid line represents the HST F140W coverage, while the white dashed line marks the MUSE region with at least 4 hours of exposure. The orange circles represent the locations of the three quasars J2142-4420 (A), J2142-4419 (B), and LBQS 2138-4427 (C). The image is spatially binned and smoothed through a Gaussian function and scaled between 3 and 50 X-ray counts to balance the contrast between faint and bright sources in the field.


The MUSE Ultra Deep Field (MUDF) program is a multi-wavelength imaging and spectroscopic survey targeting a unique extragalactic field with two quasars at z = 3.2 that are separated by only 500 kpc. By combining emission line studies with high resolution spectroscopy of the two quasars, the project is designed to connect the physical properties of galaxies observed in emission with their surrounding gas viewed in absorption along the sightlines to the background quasars. These multiple sightlines provide a stereoscopic view that yields constraints on the size and geometry of the absorbing gas in the interstellar and circumgalactic medium over 10 billion years of cosmic time.

The team provides Hubble Space Telescope (HST) data products for this field, anchored by 90 orbits of Wide Field Camera 3 (WFC3) near-infrared imaging and grism spectroscopy (HST Program 15637) that represents the deepest HST grism survey ever conducted for a single field. The release contains custom-calibrated science data that includes WFC3 F140W, F125W, and F336W imaging, WFC3 G141 grism spectroscopy, and reprocessed Wide Field and Planetary Camera 2 (WFPC2) F702W and F450W imaging. The team supplies source catalogs with photometric and morphological measurements for 3,375 unique sources, including 1,536 objects with both imaging and spectroscopic coverage. The team provides robust spectroscopic redshifts for 419 sources between z = 0 – 6, which will enable a variety of studies focusing on galaxy formation and evolution in different environments.

These High Level Science Products contain science images with plate scales of 0.06 arcsec pixel-1 that are aligned with north up to the GAIA Early Data Release 3 (EDR3) astrometric coordinate system. The provided Point Spread Function (PSF) models have identical plate scales and have their integrated flux normalized to unity, which corresponds to the zero-point magnitude in each filter. The catalogs are provided in ASCII format, along with a quick view PDF that contains a summary figure of the imaging, photometry, and spectroscopy for each object with HST spectral coverage.


Update April 05, 2024: The team provides an emission line catalog with spectroscopic redshifts for 419 sources in the field, with measurements of up to 32 emission lines from the rest-frame ultraviolet to near-infrared. The spectral fitting techniques and contents of the spectroscopic catalog are presented in Revalski et al. 2024. Finally, the team has revised the headers of the 1D and 2D HST grism spectra to include additional information about the observations.

Update August 29, 2023: The team provides calibrated XMM-Newton EPIC (European Photon Imaging Camera) data products for this field, processed with the standard pipeline. An example reduction thread for the pn CCD can be found here. The images for the pn, MOS1 and MOS2 CCDs cover the energy band 0.2-12 keV (EPIC band 8), and the 150 ks of observations have been filtered for periods of high particle background. The team also provides an ascii file summarizing the properties of the seven X-ray detected sources within the HST footprint of the MUDF.

Data Products

Images and Models

Image and model files have the following naming convention:



  • <observatory> = Observatory, either "hst" or "xmm-newton"
  • <ins> = Instrument used, either "wfc3", "wfpc2", "mos1", "mos2", or "pn".
  • <filter> = Filter used, either "f125w", "f140w", "f336w", "f450w", "f702w" or "epic8".
  • <datatype> = Product extension, see table below for possible values.

Image file types:


Science drizzle images with pixel scales of 0.06 arcseconds per pixel and in units of counts per second.


Drizzle weight maps that were produced using the inverse variance map (IVM) option in AstroDrizzle.


Drizzle error maps (1/\(\sqrt{\mathrm{IVM}}\)) that have been corrected for correlated pixel noise.


Science drizzle images multiplied by -1.0 so they may be used to determine source detection thresholds.


Area-normalized PSF models that are 69 x 69 pixels in size with scales of 0.06 arcseconds per pixel.


Area-normalized convolution kernels used to PSF-match each filter to the F140W mosaic resolution.


Science drizzle images convolved to the spatial resolution of the F140W mosaic and used for photometry.


Merged deep+shallow segmentation map with IDs matching those in the merged photometric catalog.

_image.fits XMM-Newton image file



Catalog files are named according to the following convention:



  • <observatory> = Observatory, one of "hst" or "xmm-newton".
  • <ins> = Instrument used, either "wfc3" or "wfpc2".
  • <filter> = Filter used, either "f125w", "f140w", "f336w", "f450" or "f702w".
  • <catalogtype> = Product extension, see table below for possible values.

Catalog file types:


Statmorph catalog table for each filter.


Multi-filter Source Extractor catalog for photometric data.

_spectroscopic-catalog.txt Spectroscopic redshift and emission line flux catalog.
_catalog.txt Properties of the seven X-ray detected sources within the HST footprint of the MUDF.



1D spectra files are named according to the following convention:



  • <object> = Zero-padded five-digit object number. 

2D spectra files are named according to the following convention:



  • <object> = Zero-padded five-digit object number. 
  • <ang> = Position angle in degrees. The "neg" prefix indicates that the angle is negative.


Summary graphics that display the direct imaging, photometry, and HST grism spectra for each object are named according to the following convention:



  • <object> = Zero-padded five-digit object number. In the case of "_summary.pdf", this is a combined summary PDF for all objects.

Statmorph graphics summarizing the morphologies, including the orientation, elongation, and CAS statistics for each object, are named according to the following convention:



  • <filter> = Filter used, either "f125w", "f140w", "f336w", "f450" or "f702w".

Data Access

Imaging and Spectral Products

HST Imaging, model, and catalog files can be downloaded directly using the links from the table below. The multi-filter Source Extractor catalogs ("Photometric Catalog" and "Spectroscopic Catalog") are linked at the bottom of the table. Each image file has size ~0.25 GB.

Filter Inst. Image Files Model Files Catalog Files
F125W WFC3 drz-sci | drz-wht | drz-rms | drz-neg | drz-con  psf-mod | con-ker morphology-catalog
F140W WFC3 drz-sci | drz-wht | drz-rms | drz-neg |  seg-map



F336W WFC3 drz-sci drz-wht | drz-rms | drz-neg | drz-con 

psf-mod | con-ker


F450W WFPC2 drz-sci | drz-wht | drz-rms | drz-neg | drz-con 

psf-mod | con-ker


F702W WFPC2 drz-sci | drz-wht | drz-rms | drz-neg | drz-con 

psf-mod | con-ker


Photometric Source Catalog |  Spectroscopic Catalog 

XMM-Newton Products

XMM-Newton image and catalog files can be directly downloaded from the table below. See the MUDF README linked at the top of the page for details on the catalog contents. All files have sizes <0.3GB. 

XMM-Newton Products: Direct Download
MOS 1 Image | MOS 2 Image | pn Image | Catalog 


Bulk Download Scripts

cURL scripts for bulk downloading spectra and graphics files can be downloaded from the table below. A direct link to the merged summary PDF is linked at the bottom of the table.

File Type cURL Scripts

Estimated Download Size

Spectra 1D | 2D 0.4 GB | 2.5 GB
Graphics  summary | statmorph 0.6 GB | 0.9 GB

Merged summary pdf (direct link)


30.5 MB


MAST Portal and Astroquery

The MUDF data products are also available in the MAST Portal (web-based, cross-mission search interface) and Astroquery (Python package to search for and download files from Python scripts you write). In the MAST Portal, set the Provenance Name filter to "MUDF" in an Advanced Search to find these data. In Astroquery, the following example code demonstrates how to search for and download these products:

from astroquery.mast import Observations
# Search for all MUDF products
all_obs = Observations.query_criteria(provenance_name="mudf")
data_products = Observations.get_product_list(all_obs)
# Download data
  • A web-based interface for cross-mission searches of data at MAST or the Virtual Observatory.
  • Search for and retrieve MUDF data products programmatically.


Please remember to cite the appropriate paper(s) below and the DOI if you use these data in a published work. 

Note: These HLSP data products are licensed for use under CC BY 4.0.