As described here, the eROSITA-DE team has divided the first eROSITA All-Sky Survey (eRASS1) observations into 4700 sky tiles for practical purposes. Each sky tile has a size of 3.6x3.6 square degrees, overlapping by approximately 20 arcmin. In this page, a description of the released data and source products that comprise the eROSITA-DE Data Release 1 (DR1) is provided. A detailed description of these data and source products can be found in the appendix C of Brunner, H., et al. (2022).
On this page
The released calibrated event lists of each sky tile contain X-ray photons from all eROSITA telescope modules:
flag=0xE000F000, i.e., good events from the nominal field of view, excluding bad pixels (click here for further information about flags);The event files contain up to 65 extensions:
Primary: contains the main HEADER of the file (see here for a description of the HEADER keywords);EVENTS: may contain data from all seven eROSITA cameras (see here for a possible explanation for one or more missing cameras);CORRATTn with n=1,…,7: contain the pointing direction and roll angle of each camera;DEADCORn with n=1,…,7: contain the dead exposure time fraction of each camera;BADPIXn with n=1,…,7: contain the characteristics of bad pixels in each camera;HKnm with m=1, 2, 3, 5, and n=1,…,7: contain a selection of housekeeping (HK) parameters for each camera;GTIn with n=1,…,7: contain a list of Good Time Intervals (GTI) for each camera;FLAREGTIn with n=1,…,7: contain a list of flare GTIs for each camera.This page describes in detail the extensions present in the eROSITA-DE DR1 event lists.
The images contain data from all eROSITA cameras active during the corresponding survey scan. The images have a size of 3.6x3.6 square degrees (3240x3240 pixels). Each pixel has a size of 4x4 arcsec.
The images have been produced with the eSASS task evtool, applying the option gti=GTI.
The image files are provided in seven different energy bands:
(see here to learn about the DR1 file naming scheme).
The image files contain up to 65 extensions:
Primary: contains the main HEADER of the file and the image in a given energy band (see here for a description of the HEADER keywords);EVENTS: contain data from all active eROSITA cameras in the corresponding energy band;CORRATTn with n=1,…,7: contain the pointing direction and roll angle of each camera;DEADCORn with n=1,…,7: contain the dead exposure time fraction of each camera;BADPIXn with n=1,…,7: contain the characteristics of bad pixels in each camera;HKnm with m=1, 2, 3, 5, and n=1,…,7: contain a selection of housekeeping (HK) parameters for each camera;GTIn with n=1,…,7: contain a list of Good Time Intervals (GTI) for each camera;FLAREGTIn with n=1,…,7: contain a list of flare GTIs for each camera.This page describes in detail the extensions present in the eROSITA-DE DR1 images.
For each count image a corresponding exposure map with matching image and pixel sizes is provided. The exposure is expressed in units of seconds, corrected for telescope vignetting and weighted according to the relative contributions of each of the seven eROSITA telescope modules. As both the telescope vignetting and to a lesser extent the effective areas of each telescope module are energy dependend, a spectral power law model with index -1.7 is assumed.
The exposure maps have been produced with the eSASS task expmap.
The DR1 exposure maps contain 8 extensions:
Primary: contains the main HEADER of the file and the exposure map in a given energy band (see here for a description of the HEADER keywords);GTIn with n=1,…,7: contain a list of Good Time Intervals (GTI) for each camera.This page describes in detail the extensions present in the eROSITA-DE DR1 exposure maps.
The background maps contain the sky and detector background obtained by adaptive filtering of the source-free regions of the corresponding count images. The background is provided in units of counts/image pixel.
The background maps have been produced with the eSASS task erbackmap. The units of the background map are counts/(image pixel).
Contrary to the images and exposure maps, the background maps are released only for four energy bands:
The DR1 background maps contain only 1 extension:
Primary: contains the main HEADER of the file and the background map in a given energy band (see here for a description of the HEADER keywords).The sensitivity maps have been produced with the eSASS task ersensmap. They give the minimum flux required for the detection of a point source with a detection likelihood of at least 5 (likemin>5). The units of the sensitivty maps are erg s-1 cm-2, where the conversion from counts to fluxes is performed by assuming a power law spectral index of 2.0 and an absorbing column density of 3x1020 cm2.
Sensitivity maps are released for two types of input source catalogues:
The DR1 sensitivity maps contain only 1 extension:
Primary: contains the main HEADER of the file and the sensitivity map for a given source list (see here for a description of the HEADER keywords).These tables contain the cumulative survey area as a function of limiting flux. They have been produced with the eSASS task ersensmap for all sources with minimum likelihood greater than 5 (likemin>5) in a given source catalog.
Sensitivity maps are released for two types of input source catalogues:
The DR1 Sensitivity maps based on aperture photometry contain 3 extensions:
Primary: contains the main HEADER of the file (see here for a description of the HEADER keywords).SKY_AREA: table giving the cumulative sky area (in units of deg-2) in which sources above a limiting flux (in units of erg s-1 cm-2) are detected. This page describes in detail the extensions present in the eROSITA-DE DR1 data products.
The sensitivity maps have a size of 3.6x3.6 square degrees (3240x3240 pixels). Each pixel has a size of 4x4 arcsec.
These aperture photometry's sensitivity maps have been produced with the eSASS task apetool. They include aperture-averaged exposure maps, aperture integrated background maps, and area curves (survey area sensitive to a given count rate).
The aperture photometry's sensitivity maps are released for four different energy bands:
The DR1 sensitivity maps based on aperture photometry contain 4 extensions:
Primary: contains the main HEADER of the file and the sensitivity map [counts], i.e. the minimum number of counts as a function of detector position (see here for a description of the HEADER keywords).NoName: the expected background within the extraction aperture [counts], i.e. the integral of the ermldet source map within the extraction aperture.NoName: the average exposure time (mean of the exposure map [s])
ACURVE: count rate [log counts/sec] as a function of field of view area [deg²].This page describes in detail the extensions present in the eROSITA-DE DR1 data products.
The source products are released for all detected sources in the 1B (1 band) catalogue with DET_LIKE_0 > 20. These products include source and background spectra, their respective ARFs and RMFs, a source light curve, and source and background event lists. A *.tar.xz file contains all these products per source. Moreover, the source products are offered per individual, active telescope module (TM) and merged TM combination (see here to learn about the DR1 file naming scheme). If all TMs were active during the scan of a given source, then one should expect to find 64 products per source (the source products of the combined TMs do not contain source and background event lists).
The source products have been produced with the eSASS task srctool, applying the option gti=FLAREGTI. This GTI selection is different from the other DR1 data products.
The source spectrum is extracted around the source position, using the option srcreg=AUTO in srctool.
The DR1 source spectrum contains 3 extensions:
Primary: contains the main HEADER of the file (see here for a description of the HEADER keywords).SPECTRUM: contains the source spectrum. SRCGTIn with n=0,…,9: time intervals when the extraction area was in the field of view. The background spectrum is extracted around the source position, using the option backreg=AUTO in srctool.
The DR1 background spectrum contains 3 extensions:
Primary: contains the main HEADER of the file (see here for a description of the HEADER keywords).SPECTRUM: contains the background spectrum. SRCGTIn with n=0,…,9: time intervals when the extraction area was in the field of view. The light curve of the source is binned with regularly spaced bins of 10 seconds. The lightcurves are measured in the energy bands 0.2-0.6, 0.6-2.3 and 2.3-5.0 keV (eROSITA bands 021, 022 and 023), written together in the table columns.
The DR1 light curves contain 3 extensions:
Primary: contains the main HEADER of the file (see here for a description of the HEADER keywords).RATE: light curve table giving the counts and related information in each time bin. SRCGTIn with n=0,…,9: time intervals when the extraction area was in the field of view. The source event list contains a subset of the input events, namely those falling in the source region. They miss critical information from the input event files (e.g., bad pixels and attitude) and therefore cannot be used for further analysis in evtool or srctool. They are intended for checking the output of srctool or for display. These files are currently not produced for the merged TMs (0, 8 and 9).
The DR1 source event lists contain 3 extensions:
Primary: contains the main HEADER of the file (see here for a description of the HEADER keywords).EVENTS: contain data from a given eROSITA camera, or a combination of them.SRCGTIn with n=1,…,7: time intervals when the extraction area was in the field of view. The background event list contain a subset of the input events, namely those falling in the background region.
The DR1 source event lists contain 3 extensions:
Primary: contains the main HEADER of the file (see here for a description of the HEADER keywords).EVENTS: contain data from a given eROSITA camera, or a combination of them.SRCGTIn with n=1,…,7: time intervals when the extraction area was in the field of view. The Redistribution Matrix File (RMF) contains the effective redistribution matrix for the source. It is meant to be used alongside the spectrum files for spectral analysis. The format of these files follows the OGIP recommendations for redistribution matrix FITS files described here.
The DR1 RMFs contain 3 extensions:
Primary: contains the main HEADER of the file (see here for a description of the HEADER keywords).MATRIX: contains data from a given eROSITA camera, or a combination of them.EBOUNDS: minimum and maximum energy in keV of each channel. The Ancillary Response File (ARF) contains the effective area curves for the source, to be used alongside the spectrum files for spectral analysis.
The DR1 ARFs contain 2 extensions:
Primary: contains the main HEADER of the file (see here for a description of the HEADER keywords).SPECRESP: effective area in cm2 and related information for each spectral channel.