Press-Kit for eROSITA First Light

October 22, 2019

First Light images by the eROSITA X-ray telescope.
You are free to use the images for your eROSITA reporting, please give the appropriate copyright with each image.

This image shows our neighbouring galaxy, the Large Magellanic Cloud, observed in series of exposures with all seven eROSITA telescope modules taken from 18 to 19 October 2019. The diffuse emission originates from the hot gas between the stars with temperatures typically a few million degrees. The more compact nebulous structures in the image are mainly supernova remnants, i.e. stellar atmospheres expelled in huge explosions at the end of a massive star’s lifetime. The most prominent one, SN1987A, is seen as the bright source close to the centre. A host of other sources in the LMC itself include accreting binary stars or stellar clusters with very massive young stars (up to 100 solar masses and more). There are also a number of point sources, either foreground stars from our home Galaxy or distant Active Galactic Nuclei.

The same image of the LMC but with a number of prominent sources identified. Some objects, such as the Tarantula nebula are identified by name. Some foreground stars have a known distance (in pc), as do some background AGN (in redshift). The “angel” at the bottom left corner of the image is produced by the first X-ray source ever detected in the LMC; this source is slightly off-camera, but due to its extreme brightness some light is scattered onto the detectors through the eROSITA mirrors producing both the bright feature in the corner and the arches that seem to be propagating from there.

These two eROSITA images show the two interacting galaxy clusters A3391, to the top of the image, and the double-peaked cluster A3395, to the bottom, highlighting eROSITA’s superb view of the distant Universe. They were observed in a series of exposures with all seven eROSITA telescope modules taken from 17 to 18 October 2019. The individual images were subjected to different analysis techniques, and then coloured in different schemes to highlight the different structures. In the left-hand image, the red, green and blue colours refer to the three different energy bands of eROSITA. One clearly sees the two clusters as nebulous structures, which shine brightly in X-rays due to the presence of extremely hot gas (tens of millions of degrees) in the space between galaxies. The image on the right highlights the “bridge” or “filament” between the two clusters, confirming the suspicion that these two huge structures do interact dynamically. The eROSITA observations also show hundreds of point-like sources, signposting either distant supermassive black holes or hot stars in the Milky Way.

Comparison of the eROSITA First Light image (top left) of the two interacting galaxy clusters A3391 and A3395 with other images of the same system: by the ESA X-ray telescope XMM-Newton (top right), the ROSAT X-ray camera (bottom left), and by the Planck satellite (bottom right), which was observing at much lower energy (sub-millimetre wavelengths).

eROSITA image of the interacting galaxy clusters in RGB colours.
eROSITA image of the interacting galaxy clusters, highlighting the "bridge" between the two clusters.

The supernova remnant N132D in the Large Magellanic Cloud is at a distance of about 160000 light-years, the corresponding supernova explosion happened about 3000 years ago. The eROSITA observations not only demonstrate the extremely high dynamical range (the surface brightness of N132D is 5000 times higher than its surroundings) and excellent spatial (top right) but also spectral resolution (bottom right). In the eROSITA spectrum, i.e. the „X-ray rainbow“ lines from several heavy elements can be idenfied: oxygen (O), iron (Fe), neon (Ne), magnesium (Mg), and silicon (Si)

The eROSITA observation of the isolated neutron star pulsar B0656+14 happened October 14 and 15 for a total of 28 hours with all seven telescope modules. In the combined image (left) low-energy photons are displayed in red and high-energy photons in blue. The pulsar sticks out clearly in brightness and in color, where the red color indicates a so-called soft spectrum. The accompanying spectrum on the right, shows a dip at an energy of about 0.5 keV, which has been hinted at in previous observations but is detected clearly for the first time with eROSITA due to its excellent sensitivity and spectral resolution. This unexplained feature will give astronomers new insights into the physics of neutron stars.

One of the most famous Active Galactic Nuclei (AGN), the ultrasoft Narrow-Line Seyfert 1 Galaxy 1H0707-495, has been detected with eROSITA as one of its first observations on 13 October 2019 for about 60.000 seconds. Situated near the bottom of this image, this galaxy is a highly variable AGN with a complex, steep X-ray spectrum. The two light-curves on the right show simultaneous observations with eROSITA (top) and XMM-Newton (bottom). Please notice the different scaling of the two plots; due to its larger accumulating area and its L2 location, eROSITA has a higher count rate and a more stable background (thin line at the bottom). The simultaneous eROSITA and XMM-Newton observations demonstrate the excellent calibration of eROSITA.

This plot shows the X-ray spectrum of the supernova SN 1987A. The black curve is based on data observed with all seven eROSITA telescope modules, the red curve is based on data from XMM-Newton. The eROSITA spectrum clearly demonstrates the overall higher efficiency and better spectral resolution especially at low energies.

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