Photometric Major Axis Research Articles

Bar Imprints on the Inner Gas Kinematics of M33

We present measurements of the stellar and gaseous velocities in the central 5' of the Local Group spiral M33. The data were obtained with the ARC 3.5 m telescope. Blue and red spectra with resolutions from 2 to 4 Å covering the principal gaseous emission and stellar absorption lines were obtained along the major and minor axes and six other position angles. The observed radial velocities of the ionized gas along the photometric major axis of M33 remain flat at 22 km s-1 all the way into the center, while the stellar velocities show a gradual rise from 0 to 22 km s -1 over that same region. The central star cluster is at or very close to the dynamical center, with a velocity that is in accordance with M33's systemic velocity to within our uncertainties. Velocities on the minor axis are nonzero out to about 1' from the center in both the stars and gas. Together with the major-axis velocities, they point at significant deviations from circular rotation. The most likely explanation for the bulk of the velocity patterns are streaming motions along a weak inner bar with a position angle close to that of the minor axis, as suggested by previously published IR photometric images. The presence of bar imprints in M33 implies that all major Local Group galaxies are barred. The noncircular motions over the inner 200 pc make it difficult to constrain the shape of M33's inner dark matter halo profile. If the noncircular motions we find in this nearby Sc galaxy are present in other more distant late-type galaxies, they might be difficult to recognize.

Gemini near-infrared integral field spectroscopy of the narrow-line region of ESO 428-G14: kinematics, excitation and the role of the radio jet

We present two-dimensional (2D) gas kinematics and excitation of the inner 300 pc of the Seyfert galaxy ES0428-G14 at a sampling of 14 pc 2 , from near-infrared spectroscopic observations at R ≈ 6000 obtained with the Integral Field Unit (IFU) of the Gemini Near-Infrared Spectrograph. From measurements of fluxes and profiles of the emission lines [Fe II]λ 1.257 μm, Paβ, H 2 λ 2.121 μm and Bry, we construct 2D maps of line intensities and ratios, radial velocities and velocity dispersions. Emission line 'tomography' is provided by velocity slices obtained across the line profiles, a unique capability of IFUs, which allows the mapping of not only the peak velocities but including also the wings. We compare these maps with a previously published high spatial resolution radio map and find a tight relation between the radio structure and the emission-line flux distributions and kinematics, revealing that the radio jet plays a fundamental role not only in shaping the narrow-line region but also in the imprint of its kinematics. Blueshifts of up to 400 km s -1 and velocity dispersions of up to 150 km s -1 are observed in association with the radio jet at a position angle (PA) = 129°, which is also the PA of the photometric major axis of the galaxy. We conclude that the radio jet is launched at a small angle relative to the galactic plane, with the north-western side slightly oriented towards us. This angle is small enough for the radio jet to shock and compress the gas in the plane of the galaxy, and for the nuclear continuum to ionize and heat it. The distinct kinematics and flux distributions observed for the different emission lines suggest different origins for their emission. The [Fe ΙΙ] shows the largest blueshifts and velocity dispersions and its flux distribution is concentrated along the jet, while the H 2 shows the lowest velocity dispersions and has additional flux contribution from regions beyond the jet. Both X-rays emitted by the active galactic nucleus and shocks produced by the radio jet can excite the H 2 and [Fe II] emission lines. We use the 2D velocity dispersion maps to estimate upper limits to the contribution of the radio jet to the excitation of [Fe n] and H 2 which may reach 90 per cent for [Fe II] and 80 per cent for H 2 in the jet region. The [Fe II]/Paβ emission-line ratios and the association of the [Fe ΙΙ] flux distribution and kinematics with the radio structure support a stronger contribution of the radio jet to the [Fe ΙΙ] excitation than that of H 2 . In the regions beyond the jet, the observations favour X-ray excitation.

Multifrequency Study of the Blue Compact Dwarf Haro 2

We present VLA HI imaging of the blue compact dwarf (BCD) galaxy Haro 2 and a map of its CO(1-0) distribution obtained with the OVRO millimeter array. In addition we obtained NIR JH images with the 2.1m telescope of Mexico's National Optical Observatory (OAN) and derived surface brightness profiles. Combining all these results we find an intriguing picture: the HI reveals that the kinematical major axis lies perpendicular to the photometric major axis. Our observations support the suggestion that this configuration is due to recent capture of an important quantity of gas of external origin.

Hiand CO in Blue Compact Dwarf Galaxies: Haro 2 and Haro 4

We present Very Large Array H I imaging of two blue compact dwarf galaxies, Haro 2 and Haro 4, and of the spiral galaxy Haro 26, which is projected some 22' southwest of Haro 4. We also show a map of the CO(1–0) distribution of Haro 2 obtained with the Owens Valley Radio Observatory Millimeter Array, as well as derive an upper limit for CO(2–1) emission from Haro 4 obtained with the Caltech Submillimeter Observatory. The H I data of Haro 2 reveal that the kinematical major axis lies perpendicular to the photometric major axis, indicating that the atomic hydrogen rotates about the major axis of the galaxy. This confirms earlier indications based on CCD photometry that Haro 2 is a dust-lane dE rather than a dIrr. We propose that the present neutral and molecular ISM configuration is due to recent gas accretion or a merger. The H I distribution and dynamics of Haro 4 and the neighboring spiral Haro 26 suggest that they are currently undergoing a tidal interaction, reinforcing the notion that interactions play an important role in triggering the star formation witnessed in blue compact galaxies.

Multi-wavelength study of a new sample of blue compact dwarf galaxies

We present the multi-pupil integral field spectroscopy of 18 Blue Compact Dwarf Galaxies performed at the 6 m telescope of the SAO (Russia). We produce an atlas of the H, (OIII), (SII) emission-line intensity distributions, the excitation parameter ((OIII)/H ratio), the continuum maps in blue and red and the velocity fields as derived from the 2D spectra. We provide detailed individual descriptions of the objects with a table of their spectroscopic properties. From the atlas and the velocity maps, we have classified the sample according to the following scheme: - Nine objects show spatially coincident distributions with respect to their emission lines, excitation parameter and the contin- uum. In this case, these galaxies are repeating star-formation sequences at the same spatial location. Mrk 1416 also belongs to this class of BCDG but has a secondary site of star formation. - Eight objects in which the distributions in emission lines brightness, excitation parameter and in continuum strength dier from each other at various degrees. These objects are galaxies with several sites of star formation of various ages and spatial locations. They can be ideal templates for testing the models of star formation. - From the 2-D (SII) emission-line distribution we find a superbubble structure in one object and possibly in 2 others. - Ten objects show an overall quite regular radial velocity gradient. On the other hand, in 8 objects, the kinematical major axis of this regular velocity field does not align with the photometric major axis, suggesting dynamical disturbances, gas/star decoupling and/or instabilities. - Six objects have irregular velocity fields, implying that the rotation of a gaseous disk is not their dominant dynamical signature. - SBS 1723+565B is not a dwarf galaxy but a giant irregular galaxy or an interacting system experiencing a high star formation rate.

Globular Clusters and Planetary Nebula Kinematics in NGC 5128 (Cen A)

We have conducted a wide-field optical survey of NGC 5128 (Cen A), the nearest large elliptical galaxy (3.5 Mpc). From UBVRI imaging and spectroscopic follow-up, we have identified and obtained kinematics for 125 new globular clusters out to a projected radius of 40 kpc. We also extend our survey of field star kinematics in NGC 5128, and now possess a total of 736 radial velocities for planetary nebulae out to a projected radius of 80 kpc.•The PNe sample along the photometric major axis shows significant rotational support out to 80 kpc.•The blue globular clusters seem to possess little or no angular momentum.•The kinematics of the red globular cluster sample show some evidence for rotation around an axis common to that of the field stars.

Observations of the Extended Distribution of Ionized Hydrogen in the Plane of M31

We have used the Wisconsin H-Alpha Mapper to observe the spatially extended distribution of ionized hydrogen in M31 beyond the stellar disk. We obtained five sets of observations, centered near the photometric major axis of M31, that extend from the center of the galaxy to just off the edge of the southwestern H I disk. Beyond the bright stellar disk, but within the H I disk, weak Hα is detected with an intensity IHα = 0.05 R. Since M31 is inclined 77° with respect to the line of sight, this implies that the ambient intergalactic ionizing flux on each side of M31 is Φ0 ≤ 1.6 × 104 photons cm-2 s-1. Just beyond the outer boundary of the H I disk, we find no significant detection of Hα and place an upper limit IHα ≤ 0.019 R.

Structure and Kinematics of NGC 615 and Its Nuclear Star Formation History

The results of a complex photometric and spectral investigation of the regular Sb galaxy NGC 615 are presented. The observations were made with the 6 m, 1 m, and 0.6 m telescopes of the Special Astrophysical Observatory RAS (Nizhnij Arkhyz, Russia) and the 1.5 m ESO telescope (La Silla, Chile). The analysis of the radial brightness profiles reveals the existence of at least two decoupled exponential components; the parameters of the outer component are typical for the global disks of Sb galaxies, and the inner component seen in the radius range 9''–30'' (1.0–3.5 kpc) is distinguished by compactness and high surface brightness. A combination of two-dimensional velocity fields for stars and ionized gas in the central part of the galaxy and of the long-slit velocity profiles along the major axis up to the optical border of NGC 615 provides some interesting findings. In the very center, R < 3'' (0.3 kpc), stars and gas rotate together, and the dynamical and photometric major axes are turned with respect to the global line of nodes; we conclude that inclined circumnuclear disk is detected. In the bulge, R = 3''–6'' (0.35–0.75 kpc), the stellar velocity dispersion is more than 100 km s-1, the stars rotate twice as slowly as the ionized gas, and a counterrotating gaseous component is observed. In the inner exponential component the stars rotate together with the ionized gas, and the stellar velocity dispersion drops to about 50 km s-1. As the photometric major axis of this component is turned with respect to the line of nodes, we call it an oval inner disk. The mean age of the stellar populations in the nucleus and in the inner disk beyond its H II regions is 5 Gyr, while the bulge is much older. Both the chemically decoupled nucleus of NGC 615 and the inner disk probably formed the bulk of their more luminous stars in a secondary burst of star formation, perhaps provoked by the close passage of another galaxy some gigayears ago.

Triaxial dynamical models of elliptical galaxies using Stackel potentials

A new development for components of collisionless stellar systems in a triaxial Stackel potential is presented. The non-rotating Abel components introduced by Dejonghe & Laurent are generalized. Two families of components with internal net rotation about the long or short axis of the ellipsoidal figure are described. The simple Abel character of the non-rotating components is no longer conserved when rotation is included. The rotating components can be used to build realistic three-integral dynamical models of elliptical galaxies with rotation. A triaxial dynamical model is proposed for the E2 galaxy Centaurus A. A good fit to the photometry and to planetary nebulae kinematical data (rotation and velocity dispersion on the photometric major and minor axes) is obtained. The total mass for our model of Cen A amounts to ∼ 41 × 1010 M⊙, half of which is dark mass.

Minor axis rotation and the intrinsic shape of the shell elliptical NGC 3923

We present kinematic observations of NGC 3923, one of the best-known examples of an elliptical galaxy with shells. Although NGC 3923 has no rotation on its major axis, it has minor axis rotation with an amplitude of some 20 km s−1 out to 25 arcsec radius. This is possibily the result of a kinematically decoupled core, but we present arguments against this hypothesis, and if the core were formed by a merger, this must have been a different merger from that which gave rise to the shells. The minor axis rotation suggests that NGC 3923 is prolate or triaxial, at least in the inner region. A prolate geometry for the whole galaxy would favour the merger model over the interaction model for the shell formation mechanism. There is other evidence, however, that the shape of the underlying galaxy changes with radius, in which case it is possible that the minor axis rotation could be confined to the galaxy core. The kinematics could reflect a triaxial mass distribution, in which the long and short axes are aligned with the photometric major and minor axes, and the axial ratios change such that the galaxy is near-prolate in the inner regions and near-oblate at larger radii. Measuring the rotation curve to about double this radius along the minor axis, as well as offset from the nucleus along the major axis at the radius of the innermost shells, would enable the true extent of the minor axis rotation to be determined.

The Planetary Nebula System and Dynamics of NGC 5128. III. Kinematics and Halo Mass Distributions

view Abstract Citations (195) References (59) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Planetary Nebula System and Dynamics of NGC 5128. III. Kinematics and Halo Mass Distributions Hui, Xiaohui ; Ford, Holland C. ; Freeman, Kenneth C. ; Dopita, Michael A. Abstract We present a study of the halo dynamics and mass distributions of the nearby giant elliptical galaxy NGC 5128 using planetary nebulae (PNs) as test particles. Radial velocities of 433 PNs were obtained with multifiber spectrographs on both the Anglo-Australian Telescope (AAT) and the Cerro Tololo Inter-American Observatory (CTIO) 4 m telescope. The velocities were measured from the [O III] λ5007 emission line with a typical 1 σ error of ±4 km s-1 and ±30 km s-1 for the AAT and the CTIO data, respectively. These PNs cover the entire galaxy to a radius of 10 kpc and extend along the photometric major axis out to 20 kpc. The PN velocity field shows the distinctive characteristics of a triaxial potential: the galaxy's rotation axis is offset from its photometric minor axis by 39°±10°. the rotation axis and the line of maximum rotation are likely not orthogonal. We also find that the ordered motions of the stars become more important with increasing radius compared to their random motions. The rotation reaches approximately 100 km s-1 and 50 km s-1 along the photometric major and minor axes, giving a local V/σ ratio of about 1.0 and 0.5, respectively. The aximuthal variation of the velocity dispersion appears to be modulated by rotation, i.e., it reaches a maximum where the largest rotation is observed and drops to a minimum at zero rotation. The amplitude of this modulation is about 20km s-1, compared to a mean dispersion velocity of 110 km s-1. The kinematics of the globular clusters depend on the metallicity Taking [Fe/H] = -1.0 as the dividing point, the metal-poor clusters do not show any significant rotation. However, the metal-rich clusters show both major and minor axis rotation, and the amplitudes of the rotation are similar to that of the PNs. The stellar velocity dispersion measured from absorption-line spectra together with an Hα rotation curve of the dust lane suggest that the stellar orbits are isotropic and the mass-to-light ratio (M/LB) is 3.9 in the central region of the galaxy. By applying the isotropic Jeans equation to the observed PN major axis rotation and velocity dispersion, we show that the M/LB increases with radius, suggesting the presence of dark matter in the halo. Within a 25 kpc radius, the total mass of the galaxy is 3.1 × 1011 Msun and M/LB = 10. The rotation velocity of the recently detected H I ring at a radius of 15 kpc confirms our mass model. The misalignment of the rotation axis relative to the photometric minor axis, combined with the knowledge of the dust lane orientation, allows us to uniquely determine the observer's viewing direction. The true shape of the galaxy is nearly spherical yet sufficiently triaxial to impose a distinctive gravitational signature on the kinematics. Publication: The Astrophysical Journal Pub Date: August 1995 DOI: 10.1086/176082 Bibcode: 1995ApJ...449..592H Keywords: GALAXIES: ABUNDANCES; GALAXIES: INDIVIDUAL NGC NUMBER: NGC 5128; GALAXIES: KINEMATICS AND DYNAMICS; GALAXIES: STAR CLUSTERS full text sources ADS | data products SIMBAD (435) NED (1) CDS (1) Related Materials (2) Part 1: 1993ApJ...414..463H Part 2: 1993ApJS...88..423H

The planetary nebula system and dynamics of NGC 5128. I - Planetary nebulae as standard candles

view Abstract Citations (165) References (41) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Planetary Nebula System and Dynamics of NGC 5128. I. Planetary Nebulae as Standard Candles Hui, Xiaohui ; Ford, Holland C. ; Ciardullo, Robin ; Jacoby, George H. Abstract We present the result of a planetary nebula (PN) survey of the nearby giant elliptical galaxy NGC 5128 performed with CCD cameras at the prime focus of the CTIO 4 m telescope. By comparing CCD images centered on the characteristic emission line [O III] λ5007 and on the adjacent continuum, we identify a total of 785 PNs in areas extending 20 kpc along the photometric major axis and covering the whole galaxy to 10 kpc. From these data, we form a complete sample of 224 PNs extending to a dereddened limiting magnitude of m_5007_ = 24.8, which extends 1.5 mag down the PN luminosity function (PNLF). Adopting a foreground extinction of E(B- V) = 0.1, we derive a distance to the galaxy of 3.5 +/- 0.2 Mpc, in excellent agreement with the surface brightness fluctuation method. No population effect on the bright cutoff of PNLF is observed in the isophotal radius range of 2-16 kpc, but the luminosity specific PN density (α_2.5_) seems to increase with radius inside of 7 kpc, in agreement with the α_2.5_-color relation observed for other galaxies. Publication: The Astrophysical Journal Pub Date: September 1993 DOI: 10.1086/173093 Bibcode: 1993ApJ...414..463H Keywords: Astrometry; Elliptical Galaxies; Galactic Halos; Galactic Structure; Luminosity; Planetary Nebulae; Astronomical Photometry; Chemical Evolution; Emission Spectra; Galactic Evolution; Magnitude; Mass Distribution; Oxygen Spectra; Astrophysics; COSMOLOGY: DISTANCE SCALE; GALAXIES: INDIVIDUAL NGC NUMBER: NGC 5128; ISM: PLANETARY NEBULAE: GENERAL full text sources ADS | data products SIMBAD (15) NED (1) CDS (1) Related Materials (2) Part 2: 1993ApJS...88..423H Part 3: 1995ApJ...449..592H

A radio and optical study of the interacting system NGC 5090-5091

view Abstract Citations (17) References (29) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Radio and Optical Study of the Interacting System NGC 5090--5091 Smith, R. M. ; Bicknell, G. V. Abstract The results of a radio and optical study of the interacting elliptical-spiral system NGC 5090-5091 are presented. The radio data consist of synthesis maps of 50-arcsec resolution constructed from data obtained from the Fleurs and Molonglo synthesis telescopes. The main conclusions to be drawn from the data are as follows. The rotation axis of NGC 5090 is most closely aligned with the photometric major axis. The radio axis is inclined at about 70 deg to the rotation axis and is perpendicular to the line joining the two nuclei. The morphology of NGC 5091 is consistent with tidal disruption by NGC 5090 in an initially unbound retrograde encounter. The interaction between NGC 5090 and NGC 5091 may be responsible, via an inner Lindblad resonance, for enhanced fueling of the nuclear source in NGC 5090, and this may produce jets propagating perpendicular to the orbital plane of NGC 5091. Publication: The Astrophysical Journal Pub Date: September 1986 DOI: 10.1086/164476 Bibcode: 1986ApJ...308...36S Keywords: Astronomical Photometry; Galactic Rotation; Radio Astronomy; Radio Galaxies; Elliptical Galaxies; Galactic Structure; Radio Jets (Astronomy); Resolution; Spiral Galaxies; Astrophysics; GALAXIES: INDIVIDUAL NGC NUMBER: NGC 5090; GALAXIES: INDIVIDUAL NGC NUMBER: NGC 5091; GALAXIES: INTERNAL MOTIONS; GALAXIES: PHOTOMETRY; RADIO SOURCES: GALAXIES full text sources ADS | data products SIMBAD (3) NED (2)