arXiv subjects

E. M. Corsini

Publications and source records attributed to E. M. Corsini.

166 records · Page 10Linked to original sources

arXiv1998

The Circumnuclear Ring of Ionized Gas in NGC3593

We present the results of narrow-band Halpha+NII imaging of the early-type spiral NGC3593 in combination with a study of the flux radial profiles of the NII (lambda: 654.80, 658.34 nm), Halpha, and SII (lambda: 671.65, 673.08 nm) emission lines along its major axis. The galaxy is known to contain two counterrotating stellar discs of different size and luminosity. We find that the Halpha emission mainly derives from a small central region of 57 arcsec x 25 arcsec. It consists of a filamentary pattern with a central ring. This has a diameter of about 17 arcsec (~ 0.6/h kpc) and it contributes about half of the total Halpha flux. The ring is interpreted as the result of the interaction between the acquired retrograde gas which later formed the smaller counterrotating stellar disc and the pre-existing prograde gas of the galaxy.

astro-ph↗

arXiv1998

Counterrotation in Galaxies

The phenomenon of counterrotation is observed when two galaxy components have their angular momenta projected antiparallel onto the sky. It follows that if the two components rotate around the same axis, the counterrotation is intrinsic. On the contrary the counterrotation is only apparent if the rotation axes are misaligned and the line-of-sight lies in between the two vectors or their antivectors. In the case of intrinsic counterrotation the two components can be superimposed or radially separated. As far as the two components are concerned, stars are observed to counterrotate with respect to other stars or gas. The counterrotation of gas versus gas has been also detected. Up to now, the number of galaxies exhibiting these phenomena are $\sim60$, the morphological type of which ranges from ellipticals to S0's and to spirals. When a second event occurs in a galaxy, such as the acquisition of material from outside, it is likely that the resulting angular momentum of the acquired material is decoupled from the angular momentum of the preexisting galaxy. Counterrotation is therefore a general signature of material acquired from outside the main confines of the galaxy. Good examples of such cases are ellipticals with a dust lane or gaseous disk along the minor axis and polar ring galaxies, where the angular momenta are perpendicular. It should be noted that recently attempts have been made to explain special cases of stars versus stars counterrotation in disk galaxies as due to a self induced phenomenon in non-axisymmetric potentials. We discuss the phenomenon according to the morphological type and to the kind of counterrotation.

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arXiv1998

Mixed Early and Late-Type Properties in the Bar of NGC 6221: Evidence for Evolution along the Hubble Sequence?

Rotation curves and velocity dispersion profiles are presented for both the stellar and gaseous components along five different position angles (P.A.=5, 50, 95, 125 and 155 degrees) of the nearby barred spiral NGC 6221. The observed kinematics extends out to about 80" from the nucleus. Narrow and broad-band imaging is also presented. The radial profiles of the fluxes ratio [NII]/Halpha reveal the presence of a ring-like structure of ionized gas, with a radius of about 9" and a deprojected circular velocity of about 280 km/s. The analysis of the dynamics of the bar indicates this ring is related to the presence of an inner Lindblad resonance (ILR) at 1.3 kpc. NGC6221 is found to exhibit intermediate properties between those of the early-type barred galaxies: the presence of a gaseous ring at an ILR, the bar edge located between the ILR's and the corotation radius beyond the steep rising portion of the rotation curve, the dust-lane pattern, and those of the late-type galaxies: an almost exponential surface brightness profile, the presence of Halpha regions along all the bar, the spiral-arm pattern. It is consistent with scenarios of bar-induced evolution from later to earlier-type galaxies.

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arXiv1997

Figure-of-eight velocity curves: UGC10205

We measured the velocity curve and the velocity dispersion profile of the ionized gas along the major axis of the edge-on galaxy UGC~10205. The observed kinematics extends up to about 40 arcsec from the nucleus. In the inner 13 arcsec of this early-type spiral three kinematically distinct gaseous components are present. We disentangle a fast-rotating and a slow-rotating component. They give to the UGC10205 velocity curve a ``figure-of-eight'' appearance. A third velocity component is also detected on the southeast side of the galaxy. Possibly it is produced by gas in non-circular motions.

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