Dark matter and anomalous gas in the spiral galaxy ngc 4559
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Dark matter and anomalous gas in the spiral galaxy NGC 4559. Claudia Veronica Barbieri. Relatore interno: G. Bertin Relatore esterno: R. Sancisi Correlatori: F. Fraternali T. Oosterloo. Outline. Dark and luminous matter. HI observations of NGC 4559

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Dark matter and anomalous gas in the spiral galaxy ngc 4559
Dark matter and anomalous gasin the spiral galaxyNGC 4559

Claudia Veronica Barbieri

Relatore interno: G. Bertin

Relatore esterno: R. Sancisi

Correlatori: F. Fraternali

T. Oosterloo


Outline
Outline

Dark and luminous matter

  • HI observations of NGC 4559

  • Rotation curve and mass model

Vertical structure and kinematics of the HI disk

  • Cold disk and anomalous gas

  • Models

Conclusions and future work



Direct estimate of the mass distribution (in spiral galaxies)

dynamical mass

Luminosity profile of spiral galaxies are approximately

Surface density

distribution?

luminous mass


where r = R/h and the I e K denote galaxies)

standard Bessel functions

V2

max= 0.8  G 0 h at R/h  2.2


M/L = galaxies) 3.8 M/L

van Albada et al. (1985)

THE LACK OF THE KEPLERIAN DECLINE IS

THE MAIN DIRECT EVIDENCE FOR

THE EXISTENCE OF DARK MATTER HALOS


Optical galaxies)

image

Radio

continuum

Velocity

field

HI total

map

1. HI observations of NGC 4559


2. Rotation curve and mass model galaxies)

Tilted ring model , see Begeman (1987)


the surface density distribution galaxies)

cannot explain

the observed rotation curve

DARK MATTER IS REQUIRED

2. Rotation curve and mass model


V ≈ constant (flat), so the enclosed mass M(R) galaxies)R

where 0 is the central density and Rc is the core radius

2. Rotation curve and mass model




NGC 6946 curve

optical image

total HI map

Boomsma et al. (2002)

Vertical kinematics


optical image + curve

total HI map

NGC 891

Swaters et al. (1997)

Vertical structure


Vertical structure and kinematics curve

HI total map

NGC 2403

NGC 4559

Fraternali (2001)

This work


NGC 2403 curve

Fraternali (2001)

1. Cold disk and anomalous gas


1. Cold disk and anomalous gas curve

Why study NGC 4559?


HI total map curve

of the anomalous gas

HI total map

of the cold disk

Velocity field

of the anomalous gas

Velocity field

of the cold disk

1. Cold disk and anomalous gas


Rotation curve of the curve

cold disk

(1)

 20 km/s

 60 km/s

Rotation curve of the anomalous gas

(2)

M1 = 6.7  109 M

R1 = 24.5 kpc

M2 = 5.9  108 M

R2 = 21.5 kpc

1. Cold disk and anomalous gas


One-component structure curve

corotation

no corotation

2. Models

Two-component structure



1. pure thickness effects along the line of sightGalactic fountain

A ionized gas, ejected by SN explosions and stellar winds, rieses above the disk, cools and falls back to the plane.

(Bregman J.N., 1980)

What is the origin of the anomalous gas?

2. Infall of extragalactic, probably primordial, gas


Future work pure thickness effects along the line of sight

  • Observing NGC 4559 at other wavelengths

  • Does a connection exist between the HI anomalous gas, the ionized gas (H), and the diffuse thermal emission (X-rays) as expected in the galactic fountain model?

  • Studying the small scale structure of this galaxy

  • Could the HI holes and the superbubbles (as observed in NGC 6946) be connected with the origin of the halo anomalous gas observed in NGC 4559?

  • Studying other spiral galaxies

  • Is the anomalous gas a common feature in spiral galaxies?

  • Does a relation exist between the presence of the anomalous

  • gas and the star formation activity?


The end
The end pure thickness effects along the line of sight


One component structure pure thickness effects along the line of sight


Two component structure pure thickness effects along the line of sight

(corotation)


Two component structure pure thickness effects along the line of sight

(no corotation)


Modified Newtonian Dynamics pure thickness effects along the line of sight

The gravitational field g

replaces the standard Newtonian field gn following

(g/a0) = gn

a0 = 10-8 cm/s2


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