Nucleus of M31: Upper limits to the molecular and ionised gas content

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Table 1.

Different line observations (3σ upper limits).

Inst.	Beam	t_int	ν_obs	Line	${S Δ V \|}_{up}^{3 σ}$ ${S\Delta V\|}^{3\sigma}_{\mathrm{up}}$

	“×”,deg		GHz	CO	Jy km/s
N ^(a)	2.93,2.05,−2.9	6 ⁽⁺⁾	115.387	(1–0)	1.32
N ^(b)	0.60,0.42,−164.	8.13	230.769	(2–1)	0.33
N ^(b)	0.66,0.46,+136.	8.13	232.133	H30α	0.99
A ^(c)	0.15,0.09,2.3	1.32	346.142	(3–2)	0.15

Notes. We provide the characteristics of the beam and the integration time t_int for each observational set-up for the instruments NOEMA (N) and ALMA (A). The integrated line ${S Δ V |}_{up}^{3 σ}$ ${S\Delta V|}^{3\sigma}_{\mathrm{up}}$ was computed assuming a ΔV_max = 1000 km/s window centred on the systemic velocity for the lines with upper-limit estimates of 99.7% CL. The upper limits on HCO+(4–3) at 356.734 GHz are the same as were estimated for CO(3–2).

⁽⁺⁾

This was a mosaic of four fields, each integrated for 6 hours (Melchior & Combes 2017). Observation epochs:

^(a)

between 3 September and 24 December 2012;

^(b)

8–14 February 2020;

^(c)

July 2021.

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