Table 4.
Comparison between the observed MW (Murchikova et al. 2019) and the expected ionised gas disc of M31, based on their relative black hole masses M• and distances D.
| Galaxy | D | M• | RS | RB | RB | ΔV | Mgas | S |
S |
|---|---|---|---|---|---|---|---|---|---|
| kpc | 106 M⊙ | pc | pc | ″ | km/s | M⊙ | mJy | mJy | |
| (1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | |
| MW | 8 | 4 | 4 10−7 | 0.12 | 1 | 2200 | 10−4.5 | 3 | 3 |
| M31 | 780 | 140 | 1.4 10−5 | 4.2 | 0.3 | 2200 | 0.04 | 0.38 | < 0.22 (3σ) |
| M31/MW Ratio | 97 | 35 | 35 | 35 | 0.3 | 1 | 1225 | 0.13 | 0.07 |
Notes. RS and RB are the Schwarzschild and Bondi radii (in Cols. 3 to 5), scaled with the black hole masses M• (Col. 2). The same value of the line width ΔV (in Col. 6) as observed for the MW is expected for M31. The mass of the ionised gas disc (Mgas, in Col. 7) is expected to be proportional to RB2, and it scales with M•2. Therefore, the H30α flux in M31 is expected to be eight times lower than toward the MW. Column 8 provides the fluxes expected from a simple scaling ratio with respect to the MW detections, while Col. 9 lists the actual measurement for the MW (Murchikova et al. 2019) and the effective upper limit achieved in this paper. The last line summarises the ratio of all the quantities expected (or known) for M31 with respect to the MW. Quantities in italics correspond to predicted values.
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