NGC 1275 and Perseus Galaxy Cluster (Abell 426) in Hα and continuum light

NGC 1275 is a galaxy that lies near the center of the Perseus Galaxy Cluster (also known as Abell 426) in the constellation Perseus. The galaxy contains a network of ionized filaments ejected from a central supermassive black hole. The Perseus Cluster contains more than one thousand galaxies at an estimated distance of 240 million light-years.

NGC 1275 and Perseus Galaxy Cluster (Abell 426) in H-alpha and continuum light
(requires JavaScript, Hα: on)
Click on the image to load it at full resolution in a JavaScript viewer. Use the button to switch the color mapping.

In both images, NIR (near infrared) is mapped to red, orange is mapped to green, and cyan is mapped to blue. In the version with Hα, that emission is shown in red.

The red structure in the Hα image is the gas ejected by the central supermassive black hole of NGC 1275. By toggling between the images (click the button), it can be seen that these filaments correlate with blue structures. This could be a sign of star formation in the collapsed gas.

the galaxies in the image appear relatively reddish compared to the foreground stars. This is mainly caused by dust in the Milky Way in that direction, which scatters shorter wavelengths more then longer ones. Annotations of the galaxies can be enabled in the JavaScript viewer by pressing the key 3 or via the menu.

NGC 1275 and Perseus Galaxy Cluster (Abell 426) in continuum light
Click on the image to load a full resolution version using a JavaScript viewer.

This wide-field view of the Perseus cluster is only available as a continuum image, because Hα data were only captured for the central region. As above, NIR (near-infrared) is mapped to red, orange is mapped to green, and cyan is mapped to blue. Galaxies can be annotated in the Javascript viewer by pressing key 3 or via the menu.

Image data

Due to the redshift, Hα light could not be captured with a normal Hα filter. Instead, a longer-wavelength [SII] filter was used and tilted to blue-shift the passband to approximately 668.5 nm (Lynds, 1970). (The transmission wavelength of an interference filter depends on the incident angle.)

FOV: (In the JavaScript viewer)
Hα version: 0.62° × 0.45°
Continuum only: 1.31° × 0.87°
Date: 2022-2024
Location: Pulsnitz, Germany
Instrument: 400mm Newton at f=1520mm
Camera Sensor:
Hα: Panasonic MN34230
Continuum: Sony IMX455
Orientation: North is up (approximately)
Scale: 0.8 arcsec/pixel
Total exposure times:
Hα: 30.3 h
Near infrared (SDSS I'): 4.1 h
Red (SDSS R' + 400-650 nm band-pass): 5.1 h
Blue (SDSS B'): 4.2 h

Image processing

All image processing steps are deterministic and none of the algorithms use machine learning (often referred to as “AI”), which tends to generate plausible looking fake details. The software used can be downloaded here.

The image processing steps were:

  1. Bias correction, dark current subtraction, flatfield correction, noise estimation
  2. Alignment and brightness calibration using stars from reference image
  3. Stacking with outlier rejection, background estimation and optimal weighting based on noise estimation
  4. Denoising and deconvolution
  5. Dynamic range compression using non-linear high-pass filter
  6. Color composition and tonal curve correction

References

 
R. Lynds. Improved Photographs of the NGC 1275 Phenomenon. Astrophysical Journal Letters, 159:L151–L154, March 1970. [ DOI ]

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