scholarly journals A Spiral-Like Disk of Ionized Gas in IC 1459: Signature of a Merging Collision?

1990 ◽  
Vol 124 ◽  
pp. 215-219
Author(s):  
Paul Goudfrooij ◽  
H.U. Nørgaard-Nielsen ◽  
H.E. Jørgensen ◽  
L. Hansen ◽  
T. de Jong
Keyword(s):  
Spiral Structure ◽  
Elliptical Galaxy ◽  
Broad Band ◽  
Major Axis ◽  
Colour Index ◽  
Line Flux ◽  
Ionized Gas ◽  
The Galaxy ◽  
Merger Event ◽  
Stellar Body

AbstractWe report the discovery of a large (15 kpc diameter) Hα+[NII] emission-line disk in the elliptical galaxy IC 1459, showing weak spiral structure. The line flux peaks strongly at the nucleus and is more concentrated than the stellar continuum. The major axis of the disk of ionized gas coincides with that of the stellar body of the galaxy. The mass of the ionized gas is estimated to be ~ 1 105 M⊙, less than 1% of the total mass of gas present in IC 1459. The total gas mass of 4 107 M⊙ has been estimated from the dust mass derived from a broad-band colour index image and the IRAS data. We speculate that the presence of dust and gas in IC 1459 is a signature of a merger event.

scholarly journals Probing the Halo of Centaurus A: A Merger Dynamical Model for the PN Population

1996 ◽  
Vol 171 ◽  
pp. 411-411
Author(s):  
A. Mathieu ◽  
H. Dejonghe ◽  
X. Hui
Keyword(s):  
Elliptical Galaxy ◽  
Major Axis ◽  
Minor Axis ◽  
Programming Technique ◽  
Data Set ◽  
The Galaxy ◽  
Axis Rotation ◽  
Spherical Potential ◽  
Kinematical Data ◽  
Centaurus A

We use planetary nebulae observations (Hui et al. 1995) to build dynamical models of the dust-lane elliptical galaxy NGC 5128 (Centaurus A). The PN photometric and kinematical data extend out to 20 kpc (∼ 4re) along the major axis and 10 kpc along the minor axis. Our models are built using a Quadratic Programming technique (Dejonghe 1989). The method produces fits to the data set, which consists of the photometry field (E2, well fitted by a r1/4-law) together with the major- and minor- axis rotation curves and velocity dispersion profiles. Assuming the merger hypothesis for Cen A, we describe its kinematics in a spherical potential by two sub-systems, one rotating about the intrinsic short axis and the other about the intrinsic long axis of the galaxy.

scholarly journals The halo of M 105 and its group environment as traced by planetary nebula populations

2020 ◽  
Vol 642 ◽  
pp. A46
Author(s):  
J. Hartke ◽  
M. Arnaboldi ◽  
O. Gerhard ◽  
L. Coccato ◽  
C. Pulsoni ◽  
...  
Keyword(s):  
Lower Limit ◽  
Density Profile ◽  
Surface Brightness ◽  
Broad Band ◽  
Major Axis ◽  
Asymptotic Giant Branch ◽  
Number Density ◽  
Detection Techniques ◽  
The Galaxy ◽  
Low Mass

Context. M 105 (NGC 3379) is an early-type galaxy in the Leo I group. The Leo I group is the nearest group that contains all main galaxy types and can thus be used as a benchmark to study the properties of the intra-group light (IGL) in low-mass groups. Aims. We present a photometric survey of planetary nebulae (PNe) in the extended halo of the galaxy to characterise its PN populations and investigate the presence of an extended PN population associated with the intra-group light. Methods. We use PNe as discrete stellar tracers of the diffuse light around M 105. These PNe were identified on the basis of their bright [O III]5007 Å emission and the absence of a broad-band continuum using automated detection techniques. We compare the PN number density profile with the galaxy surface-brightness profile decomposed into metallicity components using published photometry of the Hubble Space Telescope in two halo fields. Results. We identify 226 PNe candidates within a limiting magnitude of m5007, lim = 28.1 from our Subaru-SuprimeCam imaging, covering 67.6 kpc (23 effective radii) along the major axis of M 105 and the halos of NGC 3384 and NGC 3398. We find an excess of PNe at large radii compared to the stellar surface brightness profile from broad-band surveys. This excess is related to a variation in the luminosity-specific PN number α with radius. The α-parameter value of the extended halo is more than seven times higher than that of the inner halo. We also measure an increase in the slope of the PN luminosity function at fainter magnitudes with radius. Conclusions. We infer that the radial variation of the PN population properties is due to a diffuse population of metal-poor stars ([M/H] < −1.0) following an exponential profile, in addition to the M 105 halo. The spatial coincidence between the number density profile of these metal-poor stars and the increase in the α-parameter value with radius establishes the missing link between metallicity and the post-asymptotic giant branch phases of stellar evolution. We estimate that the total bolometric luminosity associated with the exponential IGL population is 2.04 × 109 L⊙ as a lower limit. The lower limit on the IGL fraction is thus 3.8%. This work sets the stage for kinematic studies of the IGL in low-mass groups.

scholarly journals The Dark Massive Halo in the Elliptical Galaxy NGC 5266

1995 ◽  
Vol 164 ◽  
pp. 446-446
Author(s):  
A. Pizzella ◽  
R. Morganti ◽  
M.E. Sadler ◽  
F. Bertola
Keyword(s):  
Spiral Galaxies ◽  
Elliptical Galaxy ◽  
Neutral Hydrogen ◽  
Major Axis ◽  
Minor Axis ◽  
Representative Point ◽  
Dust Lane ◽  
The Galaxy ◽  
Central Regions ◽  
Parallel Behaviour

Recent observations with the Australia Telescope reveal that the elliptical galaxy NGC 5266 has a disk like structure of neutral hydrogen extending as far as almost 10 Re which approximatively lies along the galaxy's major axis, at 65° apart from the inner minor–axis dust lane (Varnas et al 1987). From the present data is not clear whether the HI structure and the dust lane are two distinct disks or a single warped structure. The regularity of the velocity field of the HI structure allow us to use it as a probe of the potential of NGC 5266. The velocity curve along the major axis is flat till the last measured point (rmax ~ 10′) at Vrot = 200km/s. Assuming that the gas in moving in circular orbits, we can derive the mass of the galaxy inside to this radius. The mass–to–light ratio M/LB rises from about 3 in the central regions to 12 at 9 Re (D = 57.6 Mpc), thus indicating that NGC 5266 is embedded in a dark massive halo. Moreover the representative point (cumulative M/LB within the last measured point) of NGC 5266 in the diagram log(M/LB) – log(Re) falls well within the region characteristic of spiral galaxies (Figure 2, Bertola et al. 1993), as do ellipticals previously studied in HI, thus reinforcing the suggestion (Bertola et al. 1993) of a parallel behaviour of the dark matter in elliptical and spiral galaxies.

scholarly journals A Survey of the Interstellar Medium in Elliptical Galaxies: the Ionized Gas

1996 ◽  
Vol 171 ◽  
pp. 348-348
Author(s):  
N. Caon ◽  
F. Macchetto ◽  
M. Pastoriza
Keyword(s):  
Large Fraction ◽  
Broad Band ◽  
Elliptical Galaxies ◽  
Ionized Gas ◽  
X Ray ◽  
Lenticular Galaxies ◽  
The Galaxy ◽  
Extensive Program ◽  
Galaxy Center ◽  
S0 Galaxies

We have carried out an extensive program of observations of the ionized gas in 74 luminous elliptical and lenticular galaxies, selected to include a variety of properties in radio and X-ray emission, and in kinematical behavior. For each galaxy we have obtained broad-band R and V images and narrow-band images, centered at the Hα and [NII] emission lines, to derive the luminosity and distribution of the ionized gas. We found that a large fraction (≃ 70%) of E and S0 galaxies in our sample contain ionized gas. The gas morphology and size varies from small disks (mean diameter 1 – 4 kpc) to large filamentary structures (extending up to 10 kpc from the galaxy center). Comparison with previous measurements shows reasonable agreement for a few galaxies, but considerable scatter for a large fraction, possibly due to differences in the limiting flux thresholds.

scholarly journals Multiphase ISM in low luminosity radio galaxies: A case study of NGC 708

2015 ◽  
Vol 11 (S315) ◽  
Author(s):  
Sheetal K Sahu ◽  
S K Pandey ◽  
L Chaware ◽  
M B Pandge
Keyword(s):  
Surface Brightness ◽  
Elliptical Galaxy ◽  
Broad Band ◽  
Radio Galaxies ◽  
X Ray ◽  
The Galaxy ◽  
Multi Wavelength ◽  
Hα Emission ◽  
Cool Gas

AbstractWe present a multi-wavelength study of a nearby radio loud elliptical galaxy NGC 708, selected from the Bologna B2 sample of radio galaxies. We obtained optical broad band and narrow images from IGO 2m telescope (Pune, India). We supplement the multi-wavelength coverage of the observation by using X-ray data from Chandra, infrared data from 2MASS, Spitzer and WISE and optical image from DSS and HST. In order to investigate properties of interstellar medium, we have generated unsharp-masked, color, residual, quotient, dust extinction, Hα emission maps. From the derived maps it is evident that cool gas, dust, warm ionized Hα and hot X-ray gas are spatially associated with each other. We investigate the inner and outer photometric and kinematic properties of the galaxy using surface brightness profiles. From X-ray 2d beta model, unsharp masking, surface brightness profiles techniques, it is evident that pair of X-ray cavities are present in this system and which are ~5.6 Kpc away from the central X-ray source.

scholarly journals The 3-dimensional structure of NGC 891 and M51

2011 ◽  
Vol 7 (S284) ◽  
pp. 104-106
Author(s):  
Andrew Schechtman-Rook ◽  
Matthew A. Bershady ◽  
Kenneth Wood ◽  
Thomas P. Robitaille
Keyword(s):  
Monte Carlo ◽  
Spiral Structure ◽  
Scattered Light ◽  
Three Dimensional ◽  
Major Axis ◽  
Dimensional Structure ◽  
3 Dimensional ◽  
The Galaxy ◽  
Color Gradient ◽  
3D Monte Carlo

AbstractWe investigate the three-dimensional structure of the nearby edge-on spiral galaxy NGC 891 using 3D Monte Carlo radiative transfer models, with realistic spiral structure and fractally clumped dust. Using the spiral and clumpiness parameters found from recently completed scattered light models we produce lower resolution SED models which reproduce the spatially-integrated UV-to-FIR SED of NGC 891. Our models contain a color gradient across the major axis of the galaxy - similar to what is seen in images of the NGC 891. With minor adjustment our SED models are able to match the SED of M51, a similar galaxy at a near face-on inclination.

scholarly journals A Complete Sample of Globular Clusters in NGC 5128

1988 ◽  
Vol 126 ◽  
pp. 545-546
Author(s):  
Ray Sharples
Keyword(s):  
Power Law ◽  
Density Profile ◽  
Globular Clusters ◽  
Elliptical Galaxy ◽  
Major Axis ◽  
Cluster System ◽  
Radial Velocities ◽  
Complete Sample ◽  
The Core ◽  
The Galaxy

We present the results of an unbiased survey to search for globular clusters around the nearby elliptical galaxy NGC 5128. A total of 44 clusters has been identified on the basis of radial velocities alone. The cluster system appears to be flattened towards the major axis of the galaxy but does not show any dynamically significant rotation. There is a deficit of clusters in the core when compared with the power law density profile seen at large radii.

scholarly journals ALMA observations of AGN fuelling

2018 ◽  
Vol 614 ◽  
pp. A42 ◽  
Author(s):  
F. M. Maccagni ◽  
R. Morganti ◽  
T. A. Oosterloo ◽  
J. B. R. Oonk ◽  
B. H. C. Emonts
Keyword(s):  
Black Hole ◽  
Active Galactic Nucleus ◽  
Near Infrared ◽  
Major Axis ◽  
Massive Black Hole ◽  
Systemic Velocity ◽  
The Galaxy ◽  
Circumnuclear Disk ◽  
Stellar Body ◽  
Co Gas

We present ALMA observations of the 12CO (2–1) line of the newly born (tradio ~ 102 years) active galactic nucleus (AGN), PKS B1718–649. These observations reveal that the carbon monoxide in the innermost 15 kpc of the galaxy is distributed in a complex warped disk. In the outer parts of this disk, the CO gas follows the rotation of the dust lane and of the stellar body of the galaxy hosting the radio source. In the innermost kiloparsec, the gas abruptly changes orientation and forms a circumnuclear disk (r ≲ 700 pc) with its major axis perpendicular to that of the outer disk. Against the compact radio emission of PKS B1718–649 (r ~ 2 pc), we detect an absorption line at red-shifted velocities with respect to the systemic velocity (Δv = +365 ± 22 km s−1). This absorbing CO gas could trace molecular clouds falling onto the central super-massive black hole. A comparison with the near-infrared H2 1-0 S(1) observations shows that the clouds must be close to the black hole (r ≲ 75 pc). The physical conditions of these clouds are different from the gas at larger radii, and are in good agreement with the predictions for the conditions of the gas when cold chaotic accretion triggers an active galactic nucleus. These observations on the centre of PKS B1718–649 provide one of the best indications that a population of cold clouds is falling towards a radio AGN, likely fuelling its activity.

scholarly journals Surface Brightness Fluctuations and the Stellar Population in Elliptical Galaxies

1995 ◽  
Vol 164 ◽  
pp. 436-436
Author(s):  
Marianne Sodemann ◽  
Bjarne Thomsen
Keyword(s):  
Globular Clusters ◽  
Surface Brightness ◽  
Stellar Population ◽  
Elliptical Galaxy ◽  
Broad Band ◽  
Apparent Magnitude ◽  
New Information ◽  
Surface Brightness Fluctuations ◽  
The Galaxy ◽  
Fluctuation Noise

The Surface Brightness Fluctuation (SBF) method introduced by Tonry & Schneider (1988) is known as a distance indicator. However, we focus on another aspect. Our aim is to obtain new information on the stellar population that constitutes an elliptical galaxy by comparing radial gradients in SBF magnitudes with traditional broad-band colours. We have obtained I–band images of NGC 3379 with the NTT/SUSI, 0″.8–1″.2 FWHM, Sodemann & Thomsen (1994). An analysis similar to that of Tonry & Schneider (1988) is applied. However, the smoothed galaxy is obtained from (Thomsen & Baum, 1989). For NGC 3379 we find a SBF signal of 3.39 ± 0.02 ADU, see Figure 1, corresponding to an object with apparent magnitude Ī = 28m.62 ± 0m.03. If the image is subdivided into 4 annular regions, we find the gradient in I in Figure 2. As both fluctuation ‘noise’ and photon noise raise towards the centre of the galaxy, it is difficult to correct for globular clusters in a position independent way. Dealing with gradients of the SBF signal, the task is even more delicate. The weakening of Ī towards the galaxy centre is foreseen by the stellar population models of Worthey (1994).

Density waves in disk galaxies

1967 ◽  
Vol 31 ◽  
pp. 313-317 ◽  
Author(s):  
C. C. Lin ◽  
F. H. Shu
Keyword(s):  
Mathematical Analysis ◽  
Spiral Structure ◽  
Stellar System ◽  
Collective Modes ◽  
Disk Galaxies ◽  
Spiral Pattern ◽  
Density Waves ◽  
The Galaxy ◽  
Detailed Mathematical Analysis

Density waves in the nature of those proposed by B. Lindblad are described by detailed mathematical analysis of collective modes in a disk-like stellar system. The treatment is centered around a hypothesis of quasi-stationary spiral structure. We examine (a) the mechanism for the maintenance of this spiral pattern, and (b) its consequences on the observable features of the galaxy.

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