Exhaustion of the gas next to the supermassive black hole of M31

Melchior, A. L.; Combes, F.

doi:10.1051/0004-6361/201730910

Cited by 6 publications

(10 citation statements)

References 51 publications

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“…McKee 1989); (2) largescale dynamics (e.g. galactic tides and shear due to differential galactic rotation; Dib et al 2012;Meidt et al 2015;Melchior & Combes 2017); (3) interstellar gas pressure (e.g. Heyer et al 2009;Hughes et al 2013;Meidt 2016); and (4) the large-scale atomic gas distribution and H i column density (e.g.…”

Section: Introductionmentioning

confidence: 99%

WISDOM Project – IX. Giant molecular clouds in the lenticular galaxy NGC 4429: effects of shear and tidal forces on clouds

Liu

Bureau

Blitz

et al. 2021

Monthly Notices of the Royal Astronomical Society

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We present high spatial resolution (≈12 pc) Atacama Large Millimeter/sub-millimeter Array 12CO(J = 3 − 2) observations of the nearby lenticular galaxy NGC4429. We identify 217 giant molecular clouds within the 450 pc radius molecular gas disc. The clouds generally have smaller sizes and masses but higher surface densities and observed linewidths than those of Milky Way disc clouds. An unusually steep size – line width relation ($\sigma \propto R_{\rm c}^{0.8}$) and large cloud internal velocity gradients (0.05 – 0.91 km s−1 pc−1) and observed Virial parameters (〈αobs, vir〉 ≈ 4.0) are found, that appear due to internal rotation driven by the background galactic gravitational potential. Removing this rotation, an internal Virial equilibrium appears to be established between the self-gravitational (Usg) and turbulent kinetic (Eturb) energies of each cloud, i.e. $\langle \alpha _{\rm sg,vir}\equiv \frac{2E_{\rm turb}}{\vert U_{\rm sg}\vert }\rangle \approx 1.3$. However, to properly account for both self and external gravity (shear and tidal forces), we formulate a modified Virial theorem and define an effective Virial parameter $\alpha _{\rm eff,vir}\equiv \alpha _{\rm sg,vir}+\frac{E_{\rm ext}}{\vert U_{\rm sg}\vert }$ (and associated effective velocity dispersion). The NGC4429 clouds then appear to be in a critical state in which the self-gravitational energy and the contribution of external gravity to the cloud’s energy budget (Eext) are approximately equal, i.e. $\frac{E_{\rm ext}}{\vert U_{\rm sg}\vert }\approx 1$. As such, 〈αeff, vir〉 ≈ 2.2 and most clouds are not virialised but remain marginally gravitationally bound. We show this is consistent with the clouds having sizes similar to their tidal radii and being generally radially elongated. External gravity is thus as important as self-gravity to regulate the clouds of NGC4429.

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Section: Introductionmentioning

confidence: 99%

WISDOM Project – IX. Giant molecular clouds in the lenticular galaxy NGC 4429: effects of shear and tidal forces on clouds

Liu

Bureau

Blitz

et al. 2021

Monthly Notices of the Royal Astronomical Society

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“…There is an apparent deficiency of molecular gas (e.g. Melchior & Combes 2017;Li et al 2019), which might be understood as the AGN outburst having cleaned up preexisting gas in this region. The dynamical timescale to rebuild the cold gas should be comparable to or longer than 1 Myr.…”

Section: Agn Relic Scenariomentioning

confidence: 99%

XMM-Newton RGS Spectroscopy of the M31 Bulge. I. Evidence for a Past AGN Half a Million Years Ago

Zhang

Wang²,

Foster

et al. 2019

ApJ

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Existing analysis based on spectra from the Reflection Grating Spectrometer (RGS) onboard XMM-Newton already shows that the G-ratio of the O vii Heα triplet in the inner bulge of M31 is too high to be consistent with a pure optically thin thermal plasma in collisional ionization equilibrium (CIE). Different processes that may affect properties of diffuse hot plasma were proposed, such as resonance scattering (RS) and charge exchange (CX) with cold gas. To determine which physical process(es) may be responsible for this inconsistency, we present a systematic spectroscopic analysis based on 0.8 Ms XMM-Newton/RGS data, together with complementary Chandra/ACIS-S images. The combination of these data enables us to reveal multiple non-CIE spectroscopic diagnostics, including but not limited to the large G-ratios of Heα triplets (O vii, N vi, and Ne ix) and the high Lyman series line ratios (O viii Lyβ/Lyα and Lyγ/Lyα, and N vii Lyβ/Lyα), which are not expected for a CIE plasma, and the high iron line ratios (Fe xviii 14.2Å/Fe xvii 17Å and Fe xvii 15Å/17Å), which suggest much higher temperatures than other line ratios, as well as their spatial variations. Neither CX nor RS explains all these spectroscopic diagnostics satisfactorily. Alternatively, we find that an active galactic nucleus (AGN) relic scenario provides a plausible explanation for virtually all the signatures. We estimate that an AGN was present at the center of M31 about half a million years ago and that the initial ionization parameter ξ of the relic plasma is in the range of 3-4.

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“…We present here an analysis of an IRAM-PdB interferometer mosaic of 4 fields covering the centre of Andromeda and a field of view of about 2 arcmin off-centred to the South-East. As described in Melchior & Combes (2017), the initial motivation of these observations was to search for molecular gas next to the black hole, and the region corresponding to the sphere of influence of M31's black hole, i.e. R S OI ∼ 14 pc, has been explored.…”

Section: Observations and Data Reductionmentioning

confidence: 99%

M 31 circum-nuclear region: A molecular survey with the IRAM interferometer

Dassa-Terrier

Melchior

Combes

2019

A&A

Self Cite

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We analyse molecular observations performed at IRAM interferometer in CO(1-0) of the circum-nuclear region (within 250 pc) of Andromeda, with 2.9" = 11 pc resolution. We detect 12 molecular clumps in this region, corresponding to a total molecular mass of (8.4 ± 0.4) × 10 4 M . They follow the Larson's mass-size relation, but lie well above the velocity-size relation. We discuss that these clumps are probably not virialised, but transient agglomerations of smaller entities that might be virialised. Three of these clumps have been detected in CO(2-1) in a previous work, and we find temperature line ratio below 0.5. With a RADEX analysis, we show that this gas is in non local thermal equilibrium with a low excitation temperature (T ex = 5 − 9 K). We find a surface beam filling factor of order 5 % and a gas density in the range 60 − 650 cm −3 , well below the critical density. With a gas-to-stellar mass fraction of 4 × 10 −4 and dust-to-gas ratio of 0.01, this quiescent region has exhausted his gas budget. Its spectral energy distribution is compatible with passive templates assembled from elliptical galaxies. While weak dust emission is present in the region, we show that no star formation is present and support the previous results that the dust is heated by the old and intermediate stellar population. We study that this region lies formally in the low-density part of the Kennicutt-Schmidt law, in a regime where the SFR estimators are not completely reliable. We confirm the quiescence of the inner part of this galaxy known to lie on the green valley.

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Exhaustion of the gas next to the supermassive black hole of M31

Cited by 6 publications

References 51 publications

WISDOM Project – IX. Giant molecular clouds in the lenticular galaxy NGC 4429: effects of shear and tidal forces on clouds

WISDOM Project – IX. Giant molecular clouds in the lenticular galaxy NGC 4429: effects of shear and tidal forces on clouds

XMM-Newton RGS Spectroscopy of the M31 Bulge. I. Evidence for a Past AGN Half a Million Years Ago

M 31 circum-nuclear region: A molecular survey with the IRAM interferometer

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