CO Images of the Central Regions of 20 Nearby Spiral Galaxies

Sakamoto, Kazushi; Okumura, Sachiko K.; Ishizuki, S.; Scoville, N. Z.

doi:10.1086/313265

Cited by 185 publications

(242 citation statements)

References 101 publications

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“…The characteristic Jeans-unstable scale of D1 kpc and mass of D107 (see°2.2) appear to M _ be in good agreement with observed H I superclouds (Elmegreen & Elmegreen 1983 ;Elmegreen 1987b ;Knapen et al 1993) or GMAs (Rand 1993 ;Sakamoto 1996 ;Thornley & Mundy 1997a, 1997bSakamoto et al 1999). Gravitational instabilities may also operate on a smaller scale within a preexisting spiral arm (Balbus & Cowie 1985 ;Balbus 1988 ;Elmegreen 1994).…”

Section: Observational Motivation and Previous T Heorysupporting

confidence: 77%

“…Star-forming GMCs are strongly associated with spiral arms (e.g., Stark 1979 ;Solomon, Sanders, & Rivolo 1985 ;Kenney 1997) and often tend to appear in clusters, forming giant molecular associations (GMAs) (e.g., Cohen et al 1985 ;Grabelsky et al 1987 ;Vogel, Kulkarni, & Scoville 1988 ;Rand & Kulkarni 1990 ;Rand 1993 ;Sakamoto et al 1999). GMAs are present even in Ñocculent galaxies where spiral arms are relatively weak (Sakamoto 1996 ;Thornley & Mundy 1997a, 1997b.…”

Section: Observational Motivation and Previous T Heorymentioning

confidence: 99%

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Amplification, Saturation, andQThresholds for Runaway: Growth of Self‐Gravitating Structures in Models of Magnetized Galactic Gas Disks

Kim

Ostriker

2001

ApJ

130

152

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We investigate the susceptibility of gaseous, magnetized galactic disks to the formation of selfgravitating condensations using two-dimensional, local models. We focus on two issues : (1) determining the threshold condition for gravitational runaway, taking into account nonlinear e †ects ; and (2) distinguishing the magneto-Jeans instability (MJI) that arises under inner galaxy rotation curves from the modiÐed swing ampliÐcation (MSA) that arises under outer galaxy rotation curves. For axisymmetric density Ñuctuations, instability is known to require a Toomre parameter Q \ 1. For nonaxisymmetric Ñuctuations, any nonzero shear q 4 [d ln )/d ln R winds up wave fronts such that in linear theory ampliÐcation saturates. Any Q threshold for nonaxisymmetric gravitational runaway must originate from nonlinear e †ects. We use numerical magnetohydrodynamic simulations to demonstrate the anticipated threshold phenomenon, to analyze the nonlinear processes involved, and to evaluate the critical value Q c for stabilization. We Ðnd for a wide variety of conditions, with the largest values corre-Q c D 1.2È1.4 sponding to nonzero but subthermal mean magnetic Ðelds. Our Ðndings for are similar to those Q c inferred from thresholds for active star formation in the outer regions of spiral galaxies. MJI is distinct from MSA in that opposition to Coriolis forces by magnetic tension, rather than cooperation of epicyclic motion with kinematic shear, enables nonaxisymmetric density perturbations to grow. We suggest that under low-shear inner disk conditions, will be larger than that in outer disks by a factor Q c D(v A /qc s )1@2, where and are the respective and sound speeds. v A c s Alfven

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Section: Observational Motivation and Previous T Heorysupporting

confidence: 77%

Section: Observational Motivation and Previous T Heorymentioning

confidence: 99%

Amplification, Saturation, andQThresholds for Runaway: Growth of Self‐Gravitating Structures in Models of Magnetized Galactic Gas Disks

Kim

Ostriker

2001

ApJ

130

152

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“…The abscissa is the mean surface density of molecular gas averaged over the optical disk of each galaxy (i.e., R < R 25 ) and the ordinate is the mean surface density of molecular gas in the central kiloparsec (i.e., R < 0.5 kpc). The inner averaging area matches the often-seen central gas concentrations and nuclear rings in spiral galaxies (Sakamoto et al 1999a, Camerón et al 2010. The ratio of the central-to-global surface densities, f con ≡ Σ mol (R < 0.5kpc)/Σ mol (R < R 25 ), is an index of gas central concentration in each galaxy.…”

Section: Bar-driven Gas Transport: Statisticssupporting

confidence: 70%

Kinematics and dynamics of molecular gas in galactic centers

Sakamoto

2013

Proc. IAU

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Abstract. The central molecular zone (CMZ) in the central half kpc of the Milky Way is a massive concentration of molecular gas in the center of a barred spiral galaxy. Current and past activities in the Galactic center include the formation of massive stars/clusters, AGN feeding, and feedback. At the same time, observations of molecular gas in external galaxies show that many disk galaxies have similar condensations of molecular gas in their central kpc or so. They also have CMZs, or nuclear molecular rings or concentrations in more common terms among extragalactic observers. The formation of the CMZs are often, but not always, related to stellar bars. The centers of nearby galaxies can provide valuable information on the general properties of galactic centers and CMZs through comparative studies of multiple galactic centers of different characteristics from various viewing angles. Linear resolutions achieved toward nearby extragalactic CMZs with modern radio interferometers are now comparable to those achieved toward the Galactic CMZ with small single-dish telescopes. I review and present work on the formation mechanism and properties of the CMZs in external galaxies with some comparisons with the CMZ of our Galaxy.

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“…2 shows that Σco(R) is depressed at small radii relative to an exponential radial distribution, as was also pointed out by Regan et al (2001) and Helfer et al (2003). Exponential distributions are traditionally used for fitting the radial profiles of CO surface brightness observed in nearby galaxies, and thus for inferring important physical parameters such as the scale length of the molecular disc and, when relevant, its central surface density (e.g., Young & Scoville 1982;Young et al 1995;Sakamoto et al 1999;Regan et al 2001;Helfer et al 2003;Leroy et al 2008Leroy et al , 2009). Fig.…”

Section: Molecular Gasmentioning

confidence: 57%

What powers the starburst activity of NGC 1068? Star-driven gravitational instabilities caught in the act

Romeo

Fathi

2016

Mon. Not. R. Astron. Soc.

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We explore the role that gravitational instability plays in NGC 1068, a nearby Seyfert galaxy that exhibits unusually vigorous starburst activity. For this purpose, we use the Romeo-Falstad disc instability diagnostics and data from BIMA SONG, SDSS and SAURON. Our analysis illustrates that NGC 1068 is a gravitationally unstable 'monster'. Its starburst disc is subject to unusually powerful instabilities. Several processes, including AGN/stellar feedback, try to quench such instabilities from inside out by depressing the surface density of molecular gas across the central kpc, but they do not succeed. Gravitational instability 'wins' because it is driven by the stars via their much higher surface density. In this process, stars and molecular gas are strongly coupled, and it is such a coupling that ultimately triggers local gravitational collapse/fragmentation in the molecular gas.

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CO Images of the Central Regions of 20 Nearby Spiral Galaxies

Cited by 185 publications

References 101 publications

Amplification, Saturation, andQThresholds for Runaway: Growth of Self‐Gravitating Structures in Models of Magnetized Galactic Gas Disks

Amplification, Saturation, andQThresholds for Runaway: Growth of Self‐Gravitating Structures in Models of Magnetized Galactic Gas Disks

Kinematics and dynamics of molecular gas in galactic centers

What powers the starburst activity of NGC 1068? Star-driven gravitational instabilities caught in the act

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