Post on 31-Dec-2015
description
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