scholarly journals The HI-rich Elliptical Galaxy NGC 5266: An Old Merger Remnant?

1997 ◽  
Vol 14 (1) ◽  
pp. 89-91 ◽  
Author(s):  
R. Morganti ◽  
E. M. Sadler ◽  
T. A. Oosterloo ◽  
A. Pizzella ◽  
F. Bertola
Keyword(s):  
Dark Matter ◽  
Spiral Galaxies ◽  
Elliptical Galaxy ◽  
Neutral Hydrogen ◽  
Dark Matter Halo ◽  
Dust Lane ◽  
Neutral Gas

AbstractWe present HI images for the dust-lane elliptical galaxy NGC 5266. This galaxy contains more than 1010M☉ of HI and our data show that the neutral hydrogen extends to ∼8 arcmin each side of the nucleus, or eight times the optical half-light radius Re. Surprisingly, the outer HI gas extends almost orthogonally to the optical dust lane. The overall HI kinematics can be successfully modelled by assuming that the gas hes in two orthogonal planes—in the plane of the dust lane in the central parts and perpendicular to this in the outer regions. The large amount of neutral gas observed and the HI morphology suggest that this object may have formed from the merger of two gas rich spiral galaxies. If so, it probably represents a relatively old merger remnant since most of the HI appears settled. The mass-to-light ratio has also been derived, with evidence for a dark matter halo around this galaxy.

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 ChandraEvidence of a Flattened, Triaxial Dark Matter Halo in the Elliptical Galaxy NGC 720

2002 ◽  
Vol 577 (1) ◽  
pp. 183-196 ◽  
Author(s):  
David A. Buote ◽  
Tesla E. Jeltema ◽  
Claude R. Canizares ◽  
Gordon P. Garmire
Keyword(s):  
Dark Matter ◽  
Elliptical Galaxy ◽  
Dark Matter Halo

scholarly journals Beyond ΛCDM with H i intensity mapping: robustness of cosmological constraints in the presence of astrophysics

2020 ◽  
Vol 496 (4) ◽  
pp. 4115-4126 ◽  
Author(s):  
Stefano Camera ◽  
Hamsa Padmanabhan
Keyword(s):  
Dark Matter ◽  
Modified Gravity ◽  
Cosmological Parameters ◽  
Neutral Hydrogen ◽  
Temperature Fluctuations ◽  
Dark Matter Halo ◽  
Cosmological Constraints ◽  
Intensity Mapping ◽  
Standard Cosmological Model ◽  
First Time

ABSTRACT Mapping the unresolved intensity of the 21-cm emission of neutral hydrogen (H i) is now regarded as one the most promising tools for cosmological investigation in the coming decades. Here, we investigate, for the first time, extensions of the standard cosmological model, such as modified gravity and primordial non-Gaussianity, taking self-consistently into account. The present constraints on the astrophysics of H i clustering in the treatment of the brightness temperature fluctuations. To understand the boundaries within which results thus obtained can be considered reliable, we examine the robustness of cosmological parameter estimation performed via studies of 21-cm intensity mapping, against our knowledge of the astrophysical processes leading to H i clustering. Modelling of astrophysical effects affects cosmological observables through the relation linking the overall H i mass in a bound object, to the mass of the underlying dark matter halo that hosts it. We quantify the biases in estimates of standard cosmological parameters and those describing modified gravity and primordial non-Gaussianity that are obtained if one misconceives the slope of the relation between H i mass and halo mass, or the lower virial velocity cut-off for a dark matter halo to be able to host H i. Remarkably, we find that astrophysical uncertainties will not affect searches for primordial non-Gaussianity – one of the strongest science cases for H i intensity mapping – despite the signal being deeply linked to the H i bias.

HI in the Dusty Elliptical Galaxy NGC 5266

1995 ◽  
Vol 12 (2) ◽  
pp. 143-145 ◽  
Author(s):  
R. Morganti ◽  
A. Pizzella ◽  
E. M. Sadler ◽  
F. Bertola
Keyword(s):  
Mass Distribution ◽  
Elliptical Galaxy ◽  
Neutral Hydrogen ◽  
Major Axis ◽  
Minor Axis ◽  
Dust Lane ◽  
Central Regions ◽  
Intrinsic Shape ◽  
Geometry And Kinematics ◽  
Compact Array

AbstractRecent observations with the Australia Telescope Compact Array show that the elliptical galaxy NGC 5266 has a disk of neutral hydrogen extending to almost 10Re. This HI disk lies along the galaxy’s major axis, at right angles to the inner minor-axis dust lane. The geometry and kinematics of the gas will allow us to determine both the intrinsic shape of the stellar galaxy and the mass distribution. The mass-to-light ratio M/LB rises from about 2 in the central regions to ~12 at 9Re (H0 = 50km s−1 Mpc−1).

scholarly journals Unveiling the Influence of Dark Matter in Axially Symmetric Galaxies

2013 ◽  
Vol 30 ◽  
Author(s):  
Nicolaos D. Caranicolas ◽  
Euaggelos E. Zotos
Keyword(s):  
Dark Matter ◽  
Elliptical Galaxy ◽  
Equations Of Motion ◽  
Dark Matter Halo ◽  
Meridional Plane ◽  
Axially Symmetric ◽  
Indicator Method ◽  
Galactic Model ◽  
Fast Lyapunov Indicator ◽  
Regular And Chaotic Motion

AbstractWe investigate the regular or chaotic nature of orbits of stars moving in the meridional plane (R,z) of an axially symmetric galactic model with a dense, massive spherical nucleus and a dark matter halo component. In particular, we study the influence of the fractional portion of the dark matter, by computing in each case the percentage of chaotic orbits, as well as the percentages of orbits of the main regular resonant families. In an attempt to distinguish between regular and chaotic motion, we use the fast Lyapunov indicator method to extensive samples of orbits obtained by integrating numerically the equations of motion as well as the variational equations. Furthermore, a technique which is based mainly on the field of spectral dynamics that utilises the Fourier transform of the time series of each coordinate is used for identifying the various families of regular orbits and also to recognise the secondary resonances that bifurcate from them. Two cases are studied in our work: (i) the case where we have a disk galaxy model and (ii) the case where our model represents an elliptical galaxy. A comparison with early related work is also made.

scholarly journals Neutral Hydrogen in HCG 95

2000 ◽  
Vol 174 ◽  
pp. 154-157 ◽  
Author(s):  
W. K. Huchtmeier ◽  
Lourdes Verdes-Montenegro ◽  
Min Yun ◽  
A. del Olmo ◽  
J. Perea
Keyword(s):  
Spiral Galaxies ◽  
Dwarf Galaxies ◽  
Elliptical Galaxy ◽  
Neutral Hydrogen ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Large Array ◽  
Foreground Object ◽  
Very Large Array ◽  
Group Center

AbstractWe have observed Hɪ emission and radio continuum emission from the compact group of galaxies HCG 95 with the Very Large Array (VLA)1. Two continuum sources coincide in with galaxies in this group: HCG 95 B (3.9 mJy) and HCG95C (6 mJy). Hɪ emission and absorption was detected in galaxy HCG 95 C. In addition we detected two so far unknown dwarf galaxies by their Hɪ emission within 3.5 arcmin of the group center. We did not detect galaxy b (with ç = 8000 kms−1 it is obviously a foreground object) and galaxy d — an edge-on Sc galaxy. This group definitely is Hɪ deficient compared with the average Hɪ content expected for spiral galaxies of the same luminosity and type. The first-ranked elliptical galaxy HCG 95 A might be responsible for the observed Hɪ deficiency in this group.

scholarly journals Mass of Spiral Galaxies by Means of a Maximum Disc Model

2018 ◽  
Vol 23 (2) ◽  
pp. 191-218
Author(s):  
Jerson Ivan Reina-Medrano ◽  
Framsol López-Suspes ◽  
Guillermo A González
Keyword(s):  
Dark Matter ◽  
Total Mass ◽  
Spiral Galaxies ◽  
Great Majority ◽  
The Other ◽  
Dark Matter Halo ◽  
Global Behavior ◽  
Rotation Curves ◽  
Disc Model ◽  
Major Cluster

Maximum disc mass models for a set of spiral galaxies from the Ursa Major Cluster are presented. We construct the models using the Hunther method and the particular solutions are chosen in such away that the circular velocities are adjusted very accurately to the observed rotation curves of some specific spiral galaxies. Under the maximum disc hypothesis, we consider that the rotation curves of the analyzed galaxies can be modeled with only the contribution of the disc. This implies that it is not necessary to consider the contribution of the dark matter halo in the inner part of the spiral. In this way, the models reproduce the global behavior of the rotation curves in the great majority of galaxies. Producing good adjustments to calculate the total mass of these galaxies, and yielding values of the order of 1010M0. Based on the verticalstability criterion presented by Viera & Ramos-Caro(2016), we find that all the galaxies analyzed present a vertically stable behavior.On the other hand, from the analysis of the epicyclic frequency we find that al lthe models exhibit mainly a radial stable behaviour except at the edge of the disc.

scholarly journals MeerKAT-16 H i observation of the dIrr galaxy WLM

2020 ◽  
Vol 497 (4) ◽  
pp. 4795-4813
Author(s):  
Roger Ianjamasimanana ◽  
Brenda Namumba ◽  
Athanaseus J T Ramaila ◽  
Anna S Saburova ◽  
Gyula I G Józsa ◽  
...  
Keyword(s):  
Dark Matter ◽  
Mass Distribution ◽  
Neutral Hydrogen ◽  
Major Axis ◽  
Dark Matter Halo ◽  
Chi Square ◽  
Best Fitting ◽  
The One ◽  
A Minor ◽  
Harmonic Distortions

ABSTRACT We present observations and models of the kinematics and the distribution of the neutral hydrogen (H i) in the isolated dwarf irregular galaxy, Wolf-Lundmark-Melotte (WLM). We observed WLM with the Green Bank Telescope (GBT) and as part of the MeerKAT Early Science Programme, where 16 dishes were available. The H i disc of WLM extends out to a major axis diameter of 30 arcmin (8.5 kpc), and a minor axis diameter of 20 arcmin (5.6 kpc) as measured by the GBT. We use the MeerKAT data to model WLM using the tirific software suite, allowing us to fit different tilted-ring models and select the one that best matches the observation. Our final best-fitting model is a flat disc with a vertical thickness, a constant inclination and dispersion, and a radially varying surface brightness with harmonic distortions. To simulate bar-like motions, we include second-order harmonic distortions in velocity in the tangential and vertical directions. We present a model with only circular motions included and a model with non-circular motions. The latter describes the data better. Overall, the models reproduce the global distribution and the kinematics of the gas, except for some faint emission at the 2σ level. We model the mass distribution of WLM with pseudo-isothermal (ISO) and Navarro–Frenk–White (NFW) dark matter halo models. The NFW and the ISO models fit the derived rotation curves within the formal errors, but with the ISO model giving better reduced chi-square values. The mass distribution in WLM is dominated by dark matter at all radii.

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