Interaction in the NGC 3079 group

Nebiha Shafi University of Witwatersrand and

HartRAO

Supervisors: Prof. Roy Booth (HartRAO)

Dr. Raffaella

Morganti Dr. Tom Oosterloo

(ASTRON)

Bursary and Fellowship Conference 2009

Outline

Introduction to the primary source

Observation & Data reduction

Results

Interaction in the NGC 3079 group

Summary & Future work

N. Shafi Bursary and Fellowship Conference 2009

The primary Source

HST image

NGC 3079Type: SB(s)cRA: 10 01 57.8 DEC: +55 40 47Inclination: ~ 84o

Velocity: ~ 1116 km s-1

Distance: ~ 16 Mpc

Host to a nuclear starburst and an AGN.Classified as Seyfert2.Displays 2 extended radio lobes.Rapid ionized gas outflow up to 1000 km s-1.

N. Shafi Bursary and Fellowship Conference 2009

Observation & Data reduction

Telescope: WSRT

Bandwidth: 20 MHz

Frequency : 1.42 GHz

Integration time: 5 x 12 hrs

Velocity resolution: 16 km s-1

Data reduction: MIRIAD

Standard reduction

Non-Standard reduction

“Peeling”

Observations:

N. Shafi Bursary and Fellowship Conference 2009

Beam size: 47″.5 x 44″.7

Rms noise: 0.18 mJy beam-1

The data cube

α and δ(J2000)

Name (NED) Vsys (km s−1 )

10 01 57.80 +55 40 47.01

NGC 3079 1116

10 00 48.19 +55 36 56.49

NGC 3073 1171

10 01 16.81+55 42 58.35

MCG-9-17-19 1289

10 03 32.48 +55 31 19.12

J100331.69+553121.1 1365

10 01 52.11 +55 54 34.72

J100150.85+554734.7 1164 N

10 03 13.75 +55 36 46.02

J100444.00+551943.2 1245 N

09 59 42.89 +55 53 15.84

J095940.91+555317.8 1245 N

10 02 30.01 +55 37 56.09

J100311.18+553557.6 1033 N

N – new redshift information

N. Shafi Bursary and Fellowship Conference 2009

MCG 9-17-9

NGC 3073

Total HI contours overlaid on DSS2 image

Interaction in the NGC 3079 group:

The NGC 3079 Group

Ram pressure

The ram pressure required to strip off gas from a galaxy as it moves in the intergalactic medium (IGM) :

ρv2 ≥ 2πGΣ∗ ΣHI (Gunn & Gott 1972)

Force due to IGM Gravitational restoring force

Interaction Scenarios

Where ρ - the density of the IGM G - gravitational constant v - the velocity dispersion of the group Σ∗ and ΣHI are the stellar and gas surface mass densities

N. Shafi Bursary and Fellowship Conference 2009

Interaction Scenarios

Disruption happens at radius r > rJ (r - size of the companion)

Where rJ - radius in which material remain bound to one galaxym- mass of the companionM - mass of the primary galaxyRsep - the separation between the two galaxies

(Binney & Tremaine 1987) rJ = Rsep ( m /3M )1/3

Tidal interaction The strength of the tidal force on a galaxy can be inferred from the tidal radius (Jacobi limit):

N. Shafi Bursary and Fellowship Conference 2009

MCG 9-17-9: Tidal or Ram pressure stripped?

contours in steps of 3σ

Total HI overlaid on DSS2 red image

contours of 0.2, 1, 5,10, 20, 50 100 x 1019 cm-2

HI brid

ge

A third tail?

MCG 9-17-9

N. Shafi Bursary and Fellowship Conference 2009

Problems with tidal scenario

1 . At the projected distance of 30 kpc between the two galaxies, NGC 3079 and MCG 9-17-9 the tidal radius is:

rJ 8 kpc∼

And the size of MGC 9-17-9 is:

r 5 kpc ∼

2. The lack of any disturbance sign in the optical disk of the galaxy

N. Shafi Bursary and Fellowship Conference 2009

1018 cm -2

6x1020 cm -2

IS MCG 9-17-9 being ram pressure stripped?

Assuming ΣHI/Σ ∗ = constant, the minimum ram pressure required to strip off gas from MCG 9-17-9 (for NH at half-maximum) is:

ρv2 ≥ 6.9x10 -12 dyn cm-2

1. Ram pressure due to the super-wind from NGC 3079:

N. Shafi Bursary and Fellowship Conference 2009

Ram pressure due to the super-wind or the hot X-ray

halo of NGC 3079?

Lx 6 × 10∼ 39 erg/s and extends 13-17 kpc(Cecil et al. 2002).

Assuming T= 3.5 × 106 K gives an electron density of :

ne = 7 × 10− 4 cm−3

This yields a ram pressure:

ρv2 =2.4 × 10− 11 dyn cm−2

N. Shafi Bursary and Fellowship Conference 2009

2. Ram pressure due to the hot X-ray halo of NGC 3079:

(Breitschwerdt et al. 2002)

The case of NGC 3073: What is the origin of the ‘Cometary’ appearance? Tidal or ram pressure?

N. Shafi Bursary and Fellowship Conference 2009

Problems with tidal scenario

1 . At the projected distance of 50 kpc between the two galaxies, NGC 3079 and NGC 3073 the tidal radius is:

rJ 10 kpc∼

And the size of NGC 3073is:

r 7.5 kpc ∼

2. The lack of any disturbance sign in the optical disk of the galaxy.

N. Shafi Bursary and Fellowship Conference 2009

2.5x1020 cm -2

1018 cm -2

Ram pressure due to the super-wind or X-ray halo of NGC 3079?

The minimum ram pressure required to strip off gas from NGC 3073 (for NH half-maximum) is:

ρv2 ≥ 9x10 -14 dyn cm-2

1. Ram pressure due to the hot X-ray halo of NGC 3079:

N. Shafi Bursary and Fellowship Conference 2009

2. Ram pressure due to the super-wind of NGC 3079:

Considering density decline as a function of distance gives a ram pressure of:

ρv2 ~ 3.6 × 10− 8 dyn cm−2

Adopting the lower limit for the electron density and the velocity of the super-wind from Cecil et al. (2001):

ne = 1.35 × 102 cm−3 , and V ~1000 km s−1

N. Shafi Dec 2009N. Shafi Bursary and Fellowship Conference 2009

Five new galaxies associated with NGC 3079 group were revealed.Two of the companion galaxies, MCG 9-17-9 and NGC 3073 seem to be ram pressure stripped due to the hot X-ray halo and super-wind of NGC 3079 respectively.

Investigate the effect of the interaction on the individual companion galaxies.Study the role of the companions in the nuclear activity of NGC 3079.

N. Shafi Bursary and Fellowship Conference 2009

Thank you!

Results

N. Shafi Dec 2009

HI emissionMuch extended HI emission than previous observations. Five new companion galaxies were revealed.Asymmetric HI disk. Extraplanar HI.Interaction with three companions.Interaction with three companions.

HI AbsorptionBroad and strong central absorption with a hint of blue shifted absorption detected.

Broad and strong central absorption with a hint of blueshifted component

τpeak

= 0.18

blue-shifted?

> 600 km s-1

Vsys

Hi absorption

Model

Thin disk Thick disk slow rotating halo

TiRiFiC (Jozsa et al. 2007)

Free parameters: SBR VROT PA INCLConstant parameters: Z0 XPOS YPOS VSYS DISP

N. Shafi Oct 2009

Data

Thin disk

Thick disk

The results of the models

N. Shafi Oct 2009

NGC 3079

Oos

terlo

o e

t al

. 2

007

NGC 891

Standard reduction

The result of the standard reduction

← Need different calibration for different direction -- “peeling”

Non-Standard reduction

N. Shafi Oct 2009

After “Peeling”