X-ray sources in early-type galaxies Tom Maccarone (University of Southampton)

General motivation for extragalactic studies More objects Cleaner star formation history Smoother potential

Earliest results Emission resolved & luminosity functions measured (Sarazin, Irwin & Bregman 2001) More detailed studies of lum. func. (Kim & Fabbiano 2004; Gilfanov 2004; Bildsten & Deloye 2004), applications to cosmic ray problem (e.g. Fender, Maccarone & van Kesteren 2005; Heinz & Grimm 2005) Why universal? Age/metallicity conspiracy? Will it fail at high z? Results here from NGC 4472 – Kundu, Maccarone & Zepf (2002)

Key globular cluster questions Which types of clusters have X-ray sources?  Mass  Age  Metallicity  Location  Morphology What correlations can be found between source and cluster properties?

First results Results from Kundu, Maccarone & Zepf 2002

A larger sample of galaxies See e.g. Maccarone, Kundu & Zepf 2003, Sarazin et al. 2003, Kundu et al. in prep

Cluster ages Compared NGC 3115 and 4365, which have measured ages Metallicity effects clear, age effects not Age probably less than factor of 5 or so effect between ~7 and ~12 Gyrs – marginally consistent with Davies & Hansen (1998) KMZP 2003 Field population ages may affect XRBs too – Kraft et al results on NGC 5012

Disturbed or undisturbed? NGC 4261 – GCs, X-ray sources only in NE of galaxy GCs also preferentially in NE,SW No evidence for recent merger, but unimodal cluster colors Giordano et al. (2005)

Is cluster size important? Hints of this exist (Kundu, Maccarone & Zepf 2002; Jordan et al. 2004) Currently results are inconclusive  Typical half-light radii are sub-pixel, sub- resolution Would need a large sample of more nearby GCs Important to do this correctly to see if there’s evidence of cluster evolution

Effects of cluster properties on X-ray sources Luminosity functions appear independent of any cluster properties Spectra correlated with metallicity (Irwin & Bregman 1999; MKZ 2003)

Theoretical idea 1:irradiation induced winds Metal poor stars cannot dissipate energy through lines (Iben et al. 1997) Blowing off wind speeds evolution, provides absorbing material Simultaneously explains differences in numbers and spectra (Maccarone, Kundu & Zepf 2004)

Theory idea 2: A simpler binary evolution idea? Metal poor stars – smaller convection zones, weaker magnetic braking, lower accretion rates Explains population synthesis more easily than IIWs (Ivanova 2005, submitted) Doesn’t immediate explain spectral difference, but perhaps less of a problem – maybe irradiation induced disk winds?

Are the field populations formed in clusters? See talks by Irwin, Kundu

Black holes Theory debates whether GCs eject black holes (Portegies Zwart & McMillan 2000) or form IMBHs (Miller & Hamilton 2002) or perhaps just retain some normal BHs (King, Kalogera & Rasio 2004) Already see sources above ergs/sec, but need variability to rule out multiple sources (KKR 2004)

Flaring sources: evidence for eccentric binaries? Rapid variability searches found several sources with bright flares Two showed repeating flares and were in globular clusters (Sivakoff, Sarazin & Jordan 2005) Systems are consistent with expectations for eccentric Roche lobe overflowers (e.g. Hut & Paczynski 1984), and are in roughly the numbers expected (Maccarone 2005, submitted)

Conclusions and prospectus Studies of early-type galaxies have proven fruitful Observationally – needs are better studies of age effects, better studies of effects of cluster radii, better monitoring, deeper LFs Evolution theory – effects of irradiation, eccentricity, pop synth for different SFHs, results in form useful to observers Accretion theory – better prescriptions from secular mdot to observational quantities (see e.g. Portegies Zwart, Dewi & Maccarone 2004 as a crude start) Dynamical theory – similar dynamical models at different metallicities (though see Ivanova 2005), include eccentricity