Optical long slit velocities and a combined optical and H i  velocity field for the barred spiral galaxy 
NGC 1365

Lindblad, P. O.; Hjelm, M.; Högbom, J. A.; Jörsäter, S.; Lindblad, P. A. B.; Santos-Lleó, M.

doi:10.1051/aas:1996302

Cited by 52 publications

(27 citation statements)

References 7 publications

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“…The position angle of the bar does not coincide with the symmetry axis of the projection, so that the bar signatures are obvious. With an inclination of i = 42 • , and a distance of D = 20 Mpc, the observed velocity gradient across the bar dust lanes is determined to be at maximum 40 km s −1 , with a spatial resolution below 100 pc (Lindblad et al 1996). If deprojected, the maximum would be 60 km s −1 .…”

Section: Examples Of Bar Shocksmentioning

confidence: 92%

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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Section: Examples Of Bar Shocksmentioning

confidence: 92%

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

Melchior

Combes

2011

A&A

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“…But there is an even better reason to think that they are connected. Compelling support is provided by the observation of large velocity jumps across the dust lanes (Pence & Blackman 1984;Lindblad, Lindblad, & Athanassoula 1996;Regan, Sheth, & Vogel 1999;Weiner et al 2001b;and especially Regan, Vogel, & Teuben 1997).…”

Section: Figurementioning

confidence: 99%

“…In recent years, simulations have continued to concentrate on these inner regions of barred galaxies where dust lanes and star formation are most important (Friedli & Benz 1993Piner, Stone, & Teuben 1995;Lindblad, Lindblad, & Athanassoula 1996;Englmaier & Gerhard 1997;Salo et al 1999;Weiner, Sellwood, & Williams 2001a;Maciejewski et al 2002;Regan & Teuben 2003). Details differ, but these conclusions are robust: (1) Everbody agrees that gas flows toward the center.…”

Section: Figurementioning

confidence: 99%

Secular Evolution and the Formation of Pseudobulges in Disk Galaxies

Kormendy¹,

Kennicutt

2004

Annu. Rev. Astron. Astrophys.

1,738

107

2,359

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The Universe is in transition. At early times, galactic evolution was dominated by hierarchical clustering and merging, processes that are violent and rapid. In the far future, evolution will mostly be secular: the slow rearrangement of energy and mass that results from interactions involving collective phenomena such as bars, oval disks, spiral structure, and triaxial dark halos. Both processes are important now. This paper reviews internal secular evolution, concentrating on one important consequence, the buildup of dense central components in disk galaxies that look like classical, merger-built bulges but that were made slowly out of disk gas. We call these pseudobulges.We begin with an "existence proof" -a review of how bars rearrange disk gas into outer rings, inner rings, and stuff dumped onto the center. Simulation results correspond closely to the morphology of barred galaxies. In the simulations, gas transported to small radii reaches high densities that plausibly feed star formation. In the observations, many SB and oval galaxies have dense central concentrations of gas and star formation. Optical colors and spectra often imply young stellar populations. So the formation of pseudobulges is well supported by theory and observations. It is embedded in a broader evolution picture that accounts for much of the richness observed in galaxy structure.If secular processes built dense central components that masquerade as bulges, how can we distinguish them from merger-built bulges? Observations show that pseudobulges retain a memory of their disky origin. 2That is, they have one or more characteristics of disks: (1) flatter shapes than those of classical bulges, (2) correspondingly large ratios of ordered to random velocities indicative of disk dynamics, (3) small velocity dispersions σ with respect to the Faber-Jackson correlation between σ and bulge luminosity, (4) spiral structure or nuclear bars in the "bulge" part of the light profile, (5) nearly exponential brightness profiles, and (6) starbursts. These structures occur preferentially in barred and oval galaxies in which secular evolution should be most rapid. So the cleanest examples of pseudobulges are recognizable.Are their formation timescales plausible? We use measurements of central gas densities and star formation rates to show that pseudobulges of the observed densities form on reasonable timescales of a few billion years.Thus a large variety of observational and theoretical results contribute to a new picture of galaxy evolution that complements hierarchical clustering and merging. Secular evolution consists of more than the aging of stellar populations. Every galaxy is dynamically evolving.

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“…References to the projection parameters adopted: (a) Zurita et al (2002); (b) van Zee & Bryant (1999); (c) Lindblad et al (1997); (d) Pence et al (1990); (e) Hess et al (2009); ( f ) Ganda et al (2006); (g) Knapen et al (1993); (h) Kuno et al (2007); and (i) Becker et al (1988).…”

Section: Galaxymentioning

confidence: 99%

Star formation in grand-design, spiral galaxies

Grosbøl

Dottori

2012

A&A

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Aims. Spiral structure is a prominent feature in many disk galaxies and is often outlined by bright, young objects. We study the distribution of young stellar clusters in grand-design spiral galaxies and thereby determine whether strong spiral perturbations can influence star formation. Methods. Deep, near-infrared JHK-maps were observed for ten nearby, grand-design, spiral galaxies using HAWK-I at the Very Large Telescope. Complete, magnitude-limited candidate lists of star-forming complexes were obtained by searching within the K-band maps. The properties of the complexes were derived from (H − K) -(J − H) diagrams including the identification of the youngest complexes (i.e. < ∼ 7 Myr) and the estimation of their extinction. Results. Young stellar clusters with ages < ∼ 7 Myr have significant internal extinction in the range of A V = 3-7 m , while older ones typically have A V < 1 m . The cluster luminosity function (CLF) is well-fitted by a power law with an exponent of around -2 and displays no evidence of a high luminosity cut-off. The brightest cluster complexes in the disk reach luminosities of M K = -15. m 5 or estimated masses of 10 6 M . At radii with a strong, two-armed spiral pattern, the star formation rate in the arms is higher by a factor of 2-5 than in the inter-arm regions. The CLF in the arms is also shifted towards brighter M K by at least 0. m 4. We also detect clusters with colors compatible with Large Magellanic Cloud intermediate age clusters and Milky Way globular clusters. The (J − K) -M K diagram of several galaxies shows, for the brightest clusters, a clear separation between young clusters that are highly attenuated by dust and older ones with low extinction. Conclusions. The gap in the (J − K) -M K diagrams implies that there has been a rapid expulsion of dust at an age around 7 Myr, possibly triggered by supernovae. Strong spiral perturbations concentrate the formation of clusters in the arm regions and shifts their CLF towards brighter magnitudes.

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Optical long slit velocities and a combined optical and H i velocity field for the barred spiral galaxy NGC 1365

Cited by 52 publications

References 7 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

Secular Evolution and the Formation of Pseudobulges in Disk Galaxies

Star formation in grand-design, spiral galaxies

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