Table 2
Detected shell candidates in NGC 3923.
| Label | Major-axis radius [′′] | Prominence | Data | Detection method | Figures | Note |
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|
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| S1 | +1170 | 2 | MC | 1 | A.1 | largest |
| S2 | −952 | 4 | MC | 1 | A.1, A.2 | MP, 907–1012′′, highly uncertain, possibly merged star halos |
| S3 | −846 | 1 | MC | 1 | A.1, A.2, A.8 | narrow, connected with the “progenitor” |
| S4 | −630 | 3 | MC | 1 | A.1, A.2, A.8 | MP, 640–590′′, irregular, diffuse, near the end of the “stream” |
| S5 | +490 | 3 | MC | 1 | A.1, A.3, A.8 | MP, possibly other tidal feature, small azimuthal extent, opposite S8, connected with the “hook”, shells at lower radii have surface brightness increased at the azimuth of this shell |
| S6 | −430 | 4 | MC | 3 | A.2, A.3 | MP, very diffuse and faint, highly uncertain |
| S7 | +363 | 1 | MC | 1 | A.1, A.3, A.8 | |
| S8 | −338 | 3 | MC | 3 | A.2, A.3, A.8 | MP, not on axis, only in the eastern half, opposite S5, shells at lower radii are brighter on the azimuth of S8 |
| S9 | +331 | 3 | MC | 3 | A.3 | copies the edge of S7 but lower azimuthal extent |
| S10 | −280 | 1 | MC | 1 | A.3, A.8 | |
| S11 | +260 | 3 | MC | 3 | A.3 | MP, very diffuse, a smooth step in surface brightness, possibly other tidal feature |
| S12 | −237 | 4 | MC | 3 | A.3 | MP, sharp-edged, small azimuthal extent, possibly other tidal feature |
| S13 | +203 | 1 | MC | 1 | A.3, A.8 | |
| S14 | −150 | 1 | MC | 1 | A.3 | |
| S15 | +146 | 2 | MC | 1 | A.3, A.4 | |
| S16 | +130 | 1 | MC, HST | 1 | A.4 | |
| S17 | −120 | 3 | MC, HST | 1 | A.4 | MP |
| S18 | −103 | 1 | MC, HST | 1 | A.4 | |
| S19 | +99.5 | 3 | MC, HST | 3 | A.4 | |
| S20 | −92.0 | 4 | HST | 3 | A.4 | MP, very faint and diffuse, smooth step in surface brightness, possibly other tidal feature |
| S21 | +90.6 | 3 | MC, HST | 3 | A.4 | MP |
| S22 | −78.4 | 2 | MC, HST | 1 | A.4, A.5 | sharpness varies with azimuth |
| S23 | +72.8 | 2 | MC, HST | 1 | A.4, A.5, A.6 | |
| S24 | −71.4 | 3 | MC, HST | 3 | A.4, A.5 | MP, not on axis, only in the western half, diffuse, possibly other tidal feature |
| S25 | −68.6 | 1 | MC, HST | 1 | A.4, A.5 | |
| S26 | +64.8 | 3 | MC, HST | 3 | A.4, A.5 | |
| S27 | +60.0 | 2 | MC, HST | 1 | A.4, A.5 | |
| S28 | −60.0 | 3 | MC, HST | 3 | A.4, A.5 | MP, diffuse, possibly other tidal feature |
| S29 | −55.9 | 1 | MC, HST | 1 | A.5, A.6 | |
| S30 | +51.0 | 1 | MC, HST | 1 | A.5 | very prominent |
| S31 | −49.0 | 3 | MC, HST | 3 | A.5 | MP, diffuse, possibly other tidal feature |
| S32 | +45.4 | 3 | HST | 3 | A.5 | MP, diffuse, probably the shell at 41.5′′ in Sikkema et al. (2007) |
| S33 | −44.7 | 1 | MC, HST | 1 | A.5, A.6, A.7 | very prominent |
| S34 | +38.0 | 3 | MC, HST | 3 | A.5 | MP, very faint on axis, well defined on the western half |
| S35 | −37.5 | 3 | MC, HST | 3 | A.5, A.7 | diffuse |
| S36 | +34.8 | 1 | MC, HST | 1 | A.5, A.6, A.7 | |
| S37 | −30.8 | 3 | HST | 2 | A.6, A.7 | bright smooth step in surface brightness, possibly other tidal feature, probably the shell at −28.7′′ in Sikkema et al. (2007) |
| S38 | +29.5 | 1 | MC, HST | 1 | A.5, A.6, A.7 | |
| S39 | −24.2 | 4 | MC, HST | 3 | A.6, A.7 | MP, highly questionable, faint, small azimuthal extent, possibly edge of a faint dust cloud |
| S40 | +19.8 | 1 | MC, HST | 2 | A.6, A.7 | very prominent after model subraction, abrupt cutoff in azimuth |
| S41 | −18.1 | 1 | MC, HST | 1 | A.6, A.7 | abrupt cutoff in azimuth |
| S42 | −10.8 | 3 | MC, HST | 3 | A.7 | MP, very faint |
Notes. Label – Shell designation. Radius – Shell radius in arcseconds. Shells lying on the north-eastern side of the galaxy have the positive sign; the shells on the south-western side of the galaxy have the negative sign. Prominence – 1 = Prominent and sharp-edged; 2 = Prominent and diffuse-edged; 3 = Faint but probably existent; 4 = Questionable. Data – The image where the shell was detected: our observation with MegaCam (MC) or the archival HST image (Sikkema et al. 2006). Detection method – A method allowing a good detection of the shell: 1 = No processing; 2 = Model subtraction; 3 = Minimum masking (Sect. 2.3, Appendix B). Figures – The figures showing the shell. Notes – MP = Missed by the previous observations.
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