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

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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


Dark and luminous matter

Dark and luminous matter


Dark matter and anomalous gas in the spiral galaxy ngc 4559

Direct estimate of the mass distribution (in spiral galaxies)

dynamical mass

Luminosity profile of spiral galaxies are approximately

Surface density

distribution?

luminous mass


Dark matter and anomalous gas in the spiral galaxy ngc 4559

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

standard Bessel functions

V2

max= 0.8  G 0 h at R/h  2.2


Dark matter and anomalous gas in the spiral galaxy ngc 4559

M/L = 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


Dark matter and anomalous gas in the spiral galaxy ngc 4559

Optical

image

Radio

continuum

Velocity

field

HI total

map

1. HI observations of NGC 4559


Dark matter and anomalous gas in the spiral galaxy ngc 4559

2. Rotation curve and mass model

Tilted ring model , see Begeman (1987)


Dark matter and anomalous gas in the spiral galaxy ngc 4559

the surface density distribution

cannot explain

the observed rotation curve

DARK MATTER IS REQUIRED

2. Rotation curve and mass model


Dark matter and anomalous gas in the spiral galaxy ngc 4559

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

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

2. Rotation curve and mass model


Dark matter and anomalous gas in the spiral galaxy ngc 4559

  • The luminous component cannot explain the observed rotation curve


Vertical structure and kinematics of the hi disk

Vertical structure and kinematics of the HI disk


Dark matter and anomalous gas in the spiral galaxy ngc 4559

NGC 6946

optical image

total HI map

Boomsma et al. (2002)

Vertical kinematics


Dark matter and anomalous gas in the spiral galaxy ngc 4559

optical image +

total HI map

NGC 891

Swaters et al. (1997)

Vertical structure


Dark matter and anomalous gas in the spiral galaxy ngc 4559

Vertical structure and kinematics

HI total map

NGC 2403

NGC 4559

Fraternali (2001)

This work


Dark matter and anomalous gas in the spiral galaxy ngc 4559

NGC 2403

Fraternali (2001)

1. Cold disk and anomalous gas


Dark matter and anomalous gas in the spiral galaxy ngc 4559

1. Cold disk and anomalous gas

Why study NGC 4559?


Dark matter and anomalous gas in the spiral galaxy ngc 4559

HI total map

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


Dark matter and anomalous gas in the spiral galaxy ngc 4559

Rotation curve of the

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


Dark matter and anomalous gas in the spiral galaxy ngc 4559

One-component structure

corotation

no corotation

2. Models

Two-component structure


Dark matter and anomalous gas in the spiral galaxy ngc 4559

  • The anomalous gas cannot be explained by inclination and/or pure thickness effects along the line of sight

  • It is associated with a thick HI layer with a mean rotation velocity lower than that of the disk

  • It is more evident on the S-E side


Dark matter and anomalous gas in the spiral galaxy ngc 4559

1. Galactic 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


Dark matter and anomalous gas in the spiral galaxy ngc 4559

Future work

  • 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


Dark matter and anomalous gas in the spiral galaxy ngc 4559

One component structure


Dark matter and anomalous gas in the spiral galaxy ngc 4559

Two component structure

(corotation)


Dark matter and anomalous gas in the spiral galaxy ngc 4559

Two component structure

(no corotation)


Dark matter and anomalous gas in the spiral galaxy ngc 4559

Modified Newtonian Dynamics

The gravitational field g

replaces the standard Newtonian field gn following

(g/a0) = gn

a0 = 10-8 cm/s2


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