Fig. 1: Member galaxies plus main tidal features in SQ and the sky coverage of the FAST observations of the SQ field.
From: A 0.6 Mpc H i structure associated with Stephan’s Quintet
The background image is the inverted greyscale map of the deep Canada–France–Hawaii Telescope (CFHT) MegaCam r-band image12. The NGC name, radial velocity and the Hubble type are provided for each member galaxy in SQ. The core members include NGC 7317, NGC 7318a and NGC 7319, which are located near the group centre and have similar radial velocities (6,680 ± 85 km s−1). NGC 7320c is an ‘old intruder’, which may be responsible for the formation of the inner and outer tails6,19. NGC 7318b is a ‘new intruder’, which is currently colliding into the intragroup medium of SQ and triggering a large scale shock5. NGC 7320 is a foreground galaxy. The small blue circles mark the positions of individual beams in the H i mapping observations by the FAST 19-beam receiver. The observations were carried out at 16 slightly separated pointings in a 4 × 4 rectangular grid. The small red circles mark the central positions of the FAST 19-beam receiver in these pointings, and the characters P1, P2, …, P16 inside the circles identify the different pointings. The large magenta circles (D = 2.9′, that is, the half-power beam size) show the coverage of the 19 beams in the first pointing (see Methods for more details).
