Molecular Hydrogen in the outer filaments surrounding NGC 1275

Molecular Hydrogen in the outer filaments surrounding

NGC 1275

Nina Hatch

CS Crawford, RM Johnstone,

AC Fabian

IOA, Cambridge

Central Cluster Galaxy Emission-line nebulae• Emission line nebulae are found

surrounding ~27% of CCG

• Bright and extended structureCowie et al

1983

Conselice et al 2001

• Only find emission line nebulae if cluster

has a short radiative cooling time and

bright centrally peaked x-ray emission

Perseus: 200ks Chandra

Fabian et al 03

Unsharped mask of X-ray image of Perseus cluster

Fabian et al, 2003

NGC1275/Perseus cluster in Hα

Conselice et al 2001

Edge et al, 2002

Similar line ratios found in outer filaments as in the nucleus – indicating similar ionising mechanism

Velocity shear across lower filaments ~ 175km/s

Velocity shift relative to nucleus

Ionisation MechanismsExcitation source of optical filaments still uncertain

-short cooling time → gas continually ionised

- Soft X-ray/Hα indicate filaments radiate predominantly in optical → soft x-rays do not ionise

Possible mechanisms

• UV photoionisation from nearby stars

-likely to be dominant mechanism in Eastern knot

• shocks

• conduction from hot ICM Will analyse line ratios using CLOUDY

Summary

• Detection of molecular hydrogen ~ 25kpc from CCG, deeply embedded within hot ICM

• Velocity shift between outer filaments and central nebula and within filaments

• Spectra indicate different ionisation mechanisms acting on filaments