The dark matter distribution in dwarf galaxies: a contribution to the cusp-core discussion

September 15, 2009 R.-J. Dettmar: Dark matter in dwarfs 1/25

Nearby Dwarf Galaxies @ Nearby Dwarf Galaxies @ СПЕЦ. АСТРОФИЗИЧЕСКАЯ ОБСЕРВАТОРИЯ РАН

The dark matter distribution in dwarf galaxies: a contribution to the cusp-core discussion

Ralf-Jürgen DettmarRuhr-University Bochum



Collaborators:

Janine van Eymeren (AIRUB, UManchester)

Clemens Trachternach (AIRUB)

Dominik Bomans (AIRUB)

Baerbel Koribalski (ATNF/CSIRO, AUS)



disk-halo connection with outflows or winds?



gaseous galactic halos of diffuse ionized gas (DIG) are easily observable in H

NGC4700 (Rossa&Dettmar 2001)


Nearby Dwarf Galaxies @ Nearby Dwarf Galaxies @ СПЕЦ. АСТРОФИЗИЧЕСКАЯ ОБСЕРВАТОРИЯ РАНNGC4700 HST/ACS (Rossa, Dahlem, Dettmar, van der Marel)

HST/ACS

Rossa et al.

(in prep)



NGC2366

(DAH/Lowell)

NGC4861

SDSS



Calar Alto 2.2m



Compare H_alpha velocity field with HI

H_alpha data obtained with Marseille Fabry-Perot at OHP

VLA Data were archival (new array combination, N2366)

or taken as part of THINGS (N4861, Walter et al. 2008)











NFW Profile

isothermal



Harmonic analysis of HI velocity fields

N

mmmsyslos mrsmrcrvr

1sin)(cos)()()(

1)()( 211 mforrsrA

typically N=3 is sufficient

1)()()( 22 mforrsrcrA mmm



NGC3198

from THINGS



Analysis of the THINGS sample (Trachternach et al. 2008)



Some general properties of the sample



Observational parameters



example: NGC4861



2)/1()(

ss

initialNFW

rrrrr

)]1()1[ln(

)1/()()1ln()( 200 cccx

cxcxcxvrvrot

srrcrrx // 200200

2200200 log032.0log064.091.1log vvc

de Blok 2003



mass modeling



“cusp” “core”



Slope of the dark matter profile

Data from

de Blok (2001)

De Blok & Bosma (2002)

Swaters et al. (2003)

our data black squares



Conclusions

The ionized gas does not reach escape velocity in the giant HII regions of N2366 and N4861

In our sample of dwarfs non-circular motions contribute an amplitude < 6km/s or even <3 km/s in the inner 3kpc

The rotation curves are generally better described by isothermal

DM halos than by NFW profiles

Documents

The dark matter distribution in dwarf galaxies: a contribution to the cusp-core discussion