Detection of CO in the inner part of the bulge of M31

Melchior, A. L.; Viallefond, F.; Guèlin, M.; Neininger, N.

doi:10.1046/j.1365-8711.2000.03326.x

Cited by 28 publications

(82 citation statements)

References 23 publications

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“…At 115 GHz Melchior et al (2000). As discussed in this paper, the extinction with the central 2 arcsec is not well-defined on this map.…”

Section: Observationsmentioning

confidence: 67%

“…For M 31E where the extinction is weak, we have a tentative detection at 4σ. The extinction was computed assuming a fraction of foreground light of x = 0 (see Melchior et al 2000), which is probably correct for the north-western part, where we observed, because an inclination of 45 deg is usually assumed for the nuclear spiral (Ciardullo et al 1988). We also computed the near-UV and far-UV extinction maps from archive GALEX data with the same method and found the same structures.…”

Section: Characteristics Of the Co Emission And Gas-dust Connectionmentioning

confidence: 87%

“…Most of the observations was made in the symmetrical wobbler switching mode, in which the secondary mirror nutates up to a maximum limit of ±240 arcsec in azimuth. The beam throw was determined as a function of the hour angle in a way that the OFF positions lay in extinction-free regions, as described in Melchior et al (2000). It nevertheless occurred in two positions (M 31D and M 31G) that some signal was detected in the wobbler throw positions.…”

Section: Observationsmentioning

confidence: 99%

“…It is usually described as a quiescent galaxy with little star formation SFR ∼ 0.4 M yr −1 (e.g., Barmby et al 2006;Tabatabaei & Berkhuijsen 2010;Azimlu et al 2011) and with an ultraweak nuclear activity (del Burgo et al 2000). However, ionised gas is detected in the central field (e.g., Rubin & Ford 1971;Ciardullo et al 1988;Boulesteix et al 1987;Bogdán & Gilfanov 2008;Liu et al 2010), usually interpreted in term of shocks, and Melchior et al (2000) has detected only a small amount of molecular gas (1.5 × 10 4 M ) within 1.3 (305 pc in projection). There is no obvious on-going star formation in this central region (e.g., Olsen et al 2006;Li et al 2009;Azimlu et al 2011) and the ionised gas (approximately 1500 M according to Jacoby et al 1985) can be accounted for by mass lost from evolving stars.…”

Section: Introductionmentioning

confidence: 99%

“…CO(2−1)) at the 1σ level Table 3. A B extinction derived from the map based on the Ciardullo et al (1988) data as obtained in Melchior et al (2000).…”

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confidence: 99%

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Molecular gas in the inner 0.7 kpc-radius ring of M 31

Melchior

Combes

2011

A&A

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The study of the gas kinematic in the central 1.5 kpc × 1.5 kpc region of M 31 has revealed several surprises. The starting point of this investigation was the detection at the IRAM-30 m telescope of molecular gas with very large line splittings up to 260 km s −1 within the beam (∼40 pc). In this region, which is known for its low gas content, we also detect an ionised gas outflow in the circumnuclear region (within 75 pc from the centre) extending to the whole area in X-ray. Relying on atomic, ionised, and molecular gas, we account for most observables with a scenario that assumes that a few hundreds Myr ago, M 31 underwent a frontal collision with M 32, which triggered some star-formation activity in the centre, and this collision explains the special configuration of M 31 with two rings observed at 0.7 kpc and 10 kpc. The inner disc (whose rotation is detected in HI and ionised gas ([NII])) has thus been tilted (inclination: 43 deg, PA: 70 deg) with respect to the main disc (inclination: 77 deg, PA: 35 deg). One of the CO velocity components is compatible with this inner disc, while the second one comes from a tilted ring-like material with 40 deg inclination and PA = −35 deg. The relic star formation estimated by previous works to have occurred more than 100 Myr ago could have been triggered by the collision and could be linked to the outflow detected in the ionised gas. Last, we demonstrate that the amplitude of the line splittings detected in CO centred on the systemic velocity with a relatively high spatial resolution (40 pc) cannot be accounted for by a possible weak bar that is roughly aligned along the minor axis. Although M 31 has a triaxial bulge, there are no bar indicators in the gas component (photometry, no strong skewness of the isovelocities, etc.).

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“…At 115 GHz Melchior et al (2000). As discussed in this paper, the extinction with the central 2 arcsec is not well-defined on this map.…”

Section: Observationsmentioning

confidence: 67%

Section: Characteristics Of the Co Emission And Gas-dust Connectionmentioning

confidence: 87%

Section: Observationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…CO(2−1)) at the 1σ level Table 3. A B extinction derived from the map based on the Ciardullo et al (1988) data as obtained in Melchior et al (2000).…”

mentioning

confidence: 99%

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Molecular gas in the inner 0.7 kpc-radius ring of M 31

Melchior

Combes

2011

A&A

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Lopsided spiral galaxies

2009

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The light distribution in the disks of many galaxies is non-axisymmetric or 'lopsided' with a spatial extent much larger along one half of a galaxy than the other, as in M101. Recent near-IR observations show that lopsidedness is common. The stellar disks in nearly 30 % of galaxies have significant lopsidedness of > 10% measured as the Fourier amplitude of the m=1 component normalized to the average value. This asymmetry is traced particularly well by the atomic hydrogen gas distribution lying in the outer parts. The lopsidedness also occurs in the nuclear regions, where the nucleus is offset with respect to the outer isophotes. The galaxies in a group environment show higher lopsidedness. The origin of lopsidedness could be due to the disk response to a tidally distorted halo, or via gas accretion. An m=1 perturbation in a disk leads to a shift in the center of mass in the disk, and this then acts as an indirect force on the original center of the disk. The disk is inherently supportive of an m=1 mode, which is a particular feature only of lopsided modes, and which makes their dynamical study interesting and challenging.The lopsidedness has a large impact on the dynamics of the galaxy, its evolution, the star formation in it, and on the growth of the central black hole and on the nuclear fueling, merging of binary black holes etc. The disk lopsidedness can be used as a diagnostic to study the halo asymmetry. This is an emerging area in galactic structure and dynamics. In this review, the observations to measure the lopsided distribution, as well as the theoretical progress made so far to understand its origin and properties, and the related open problems will be discussed.

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M 31's Molecular Arms at All Scales to Below 10 pc

Neininger

Nieten

Guèlin

et al. 2001

Symp. - Int. Astron. Union

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Abstract. I present a unique data set for the study of molecular gas in galaxies: a complete, high-resolution survey of the CO in M 31 and additional local studies. The fully sampled survey has an angular resolution of 23" FWHM and the interferometric data attain the pc-scale with subarcsecond resolution. For the first time it is now possible to study large and small scales in conjunction. Thus we are able to derive the global structure and study the links down to the individual cloud complexes and star formation regions.

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Detection of CO in the inner part of the bulge of M31

Cited by 28 publications

References 23 publications

Molecular gas in the inner 0.7 kpc-radius ring of M 31

Molecular gas in the inner 0.7 kpc-radius ring of M 31

Lopsided spiral galaxies

M 31's Molecular Arms at All Scales to Below 10 pc

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