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