1 / 30

RGS observations of cool gas in cluster cores

RGS observations of cool gas in cluster cores. Jeremy Sanders Institute of Astronomy University of Cambridge. Sanders et al, 2008, MNRAS, 385, 1186 Sanders et al, in prep. A.C. Fabian, J. Peterson, S.W. Allen, R.G. Morris, J. Graham, R.M. Johnstone. Cooling in cluster cores.

ofira
Download Presentation

RGS observations of cool gas in cluster cores

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. RGS observations of cool gas in cluster cores Jeremy Sanders Institute of Astronomy University of Cambridge Sanders et al, 2008, MNRAS, 385, 1186 Sanders et al, in prep A.C. Fabian, J. Peterson, S.W. Allen, R.G. Morris, J. Graham, R.M. Johnstone

  2. Cooling in cluster cores • Many cluster cores have steeply peaked X-ray surface brightness profiles, i.e. short mean radiative cooling times. • Suppose there is a luminosity L emitted from within a cooling region rcool • To offset radiation lost through cooling, if the cluster is in steady state and there is no heating, there should be a mass deposition rate of • Measured values from SB profiles gave values of 10-1000s solar masses per year – a “cooling flow” luminosity of region is: - radiation of thermal energy - PdV work done on gas entering rcool

  3. Lack of cool X-ray emitting gas de Plaa et al Spectra imply less than 10% of cooling rates expected from luminosity profiles Only significant gas down to 1/2 to 1/3 of outer temperature AGN heating? Fe XVII lines (indicating temperature ~ 0.7 keV) missing 2A 0335+096 see also Peterson et al 01, 03, Kaastra et al 01, 03, Tamura et al 01,...

  4. The Centaurus cluster Inner core of the Centaurus cluster 200 ks Chandra observation RGB image Sanders & Fabian (2002, 2006) Fabian, Sanders et al (2005) 10 kpc

  5. Centaurus temperature map Chandra 200ks observation • 200 ks Chandra observation • Projected temperature in Centaurus varies from • 3.7 keV in outskirts • to 0.7 keV in the cool plume Crawford et al 2005 Temperature (keV)

  6. Centaurus cross dispersion image With the RGS spectrometer we get a spectrum of the cluster as a function of one spatial dimension. wavelength 150 ks total XMM exposure 1D image

  7. Inner 160 arcsec width (30 kpc) Central inner 60 arcsec (13 kpc) 60-160 arcsec (13-30 kpc)

  8. Ionisation equilibrium By measuring the distribution of ionisation states of metals we can find the gas temperature, or distribution of gas temperature Values taken from Mazzotta et al 1998

  9. Inner 60 arcsec width (16 kpc) strong missing

  10. Line ratios — constraints on kT Ratio of flux of emission lines and compared to CHIANTI model Implies average temperature of gas 3.5 to 5.2 × 106 K

  11. Spectral fitting limits on gas kT Multi temperature model (components fixed in temperature but varying in emission measure) Cooling flow model (mass deposition in absence of heating) • Factor of 10 in temperature • > factor of 10 in mass deposition

  12. Spectral fitting limits on gas kT tcool ~ 107 yr! Multi temperature model (components fixed in temperature but varying in emission measure) Cooling flow model (mass deposition in absence of heating) • Factor of 10 in temperature • > factor of 10 in mass deposition

  13. New RGS spectra 138ks 156ks

  14. HCG 62 Fe XVII HCG 62 is a compact group of galaxies Prominent radio bubbles with ~1057 erg energy content Temperature varies in spatially resolved studies from 1.5 to 0.7 keV (Morita et al 2006) High abundance arc (Gu et al 2007) 156 ks O VIII

  15. HCG 62: temperature distribution 8 component VAPEC model Shows clear break in temperature distribution at 0.6 keV Emission measure drops by more than an order of magnitude Lower temperature consistent with CCD results from Chandra/XMM (Morita et al 2006)

  16. HCG 62: mass deposition rate 8 component VMCFLOW cooling flow model in steps of temperature In the absence of cooling, there is a very sharp drop in mass deposition rate at 0.6 keV, by at least an order of magnitude tcool ~ 3×108 yr

  17. Conclusions • Varied behaviour of cool cores observed by RGS • Wide range in temperature in Centaurus (factor 10) • Narrow range in HCG 62 (factor 2) • Both show strong variation in emission measure with temperature • Implies there is always close feedback • It is important to study a wide range of clusters with deep observations with XMM • We have a deep Abell 1835 observation soon • Star formation in this object ~ mass deposition rate (100 Solar masses/year)

  18. Sound waves in Centaurus Sanders & Fabian (submitted) Fourier high-pass-filtered image

  19. Centaurus SB profiles and residuals λ ~ 9 kpc

  20. Power calculation • Use deprojection factor to convert from ripple amplitude to intrinsic pressure ampl. • Assuming spherical waves, this implies 9×1042 erg s-1 sound wave power at r=30 kpc, where tcool=3.3 Gyr • 9 kpc wavelength implies 107 yr period (similar to Perseus) • Luminosity emitted within 30 kpc is 1.3×1043 erg s-1 • Using period and energy of radio bubbles, implies power of 2×1043 erg s-1

  21. HCG 62: extra absorption 8 component VMCFLOW cooling flow model in steps of temperature Extra column density of 5×1020 cm-2 added into model for three lowest temperature components

  22. HCG 62: ignoring OVII 8 component VMCFLOW cooling flow model in steps of temperature Only fitting spectrum from 7 to 20 A

  23. Very coolest gas • Very coolest X-ray gas at 0.35 keV has a mean radiative cooling time of only ~107 yr

  24. Line profiles

  25. Emission measure maps Best fitting smoothing sizes from RGS line widths

  26. Centaurus temperature and metals 25 kpc

  27. Centaurus in different elements Sanders & Fabian (2006)

  28. Supernova fractions Sanders & Fabian (2006) • Significant amount from Type II supernovae (~30%) • Therefore large amount of star formation in the Centaurus cluster • Either massive initial burst • Continuous ~5 M/yr • Likely to have been undisturbed for ~ 8 Gyr • Close heating/cooling balance

More Related