1. The Stellar Populations of NGC5128 ESO Vitacura – Nov 2005 Dante Minniti

Field 3 (jet) Magellan 1 (Rejkuba et al. A&A 2003a,b) ESO Vitacura – Nov 2005 Dante Minniti

Very young stars found in the NGC5128 halo, mostly along the jet (Graham 1998, Mould et al. 2000, Rejkuba et al. 2002). A disrupted dwarf or jet induced SF? cf. Alignment effect at high-z (e.g. van Breugel et al. 2003). HI gas cloud reservoir (Schiminovich et al. 1994, Oosterloo & Morganti 2005). ESO Vitacura – Nov 2005 Dante Minniti

the NGC5128 jet, with age logT~7.0 yr Follow up Magellan photometry confirms the presence of blue MS stars along the NGC5128 jet, with age logT~7.0 yr Rejkuba et al. 2003 ESO Vitacura – Nov 2005 Dante Minniti

Resolved Populations in NGC5128 ESO Vitacura – Nov 2005 Dante Minniti

Shell Halo Found a small population of young stars. RGB Tip Found a small population of young stars. The wide RGB indicates a significant metallicity spread (Rejkuba et al. 2002 A&A). ESO Vitacura – Nov 2005 Dante Minniti

Stellar populations HST ACS CMDs (Rejkuba et al 2005) The NGC5128 halo has: Old populations dominate No blue HB Wide metallicity spread <[Fe/H]> ~ -1 ESO Vitacura – Nov 2005 Dante Minniti

2. Variable Stars in NGC5128 ESO Vitacura – Nov 2005 Dante Minniti

Variable Stars in NGC5128 20-24 epochs with VLT+ISAAC reaching K=23 (1200 d, from 99 to 02). Discovery of 1758 luminous periodic variable stars in the NGC5128 halo. ESO Vitacura – Nov 2005 Dante Minniti

Variable Stars in NGC5128 Good periods spanning 60 to 600 days, mostly LPVs – Miras (Rejkuba et al. A&A 2003a,b). ESO Vitacura – Nov 2005 Dante Minniti

Variable Stars in NGC5128 Period distribution Difference F1-F2? Metal-rich MW globular cluster Miras: 140<P<310 days. LMC-SMC Miras: 100<P<550 days. P-distribution similar to the MW bulge in general, but 10% with P>500 days – intermediate-age AGB. ESO Vitacura – Nov 2005 Dante Minniti

Variable Stars in NGC5128 First observed Mira P-L relation beyond the Local Group. Measured the distance using the RGB Tip, and the Mira P-L relation from Feast 1998: Ko = -3.46 logP + 28.96, and assuming m-MLMC = 18.50 DN5128 = 3.9 Mpc (Rejkuba 2003). ESO Vitacura – Nov 2005 Dante Minniti

3. The Star Cluster System of Cen A ESO Vitacura – Nov 2005 Dante Minniti

Population of globular clusters There are only 155 globular clusters known in the Milky Way. Large numbers of globular clusters are found in giant elliptical galaxies. For example, the gE galaxy NGC5128 has 1700 GC in total (Kissler-Patig 1997). This GC system is 10x that of the Milky Way. The study of large GC systems is important:  for theories of galaxy formation and of globular cluster formation,  for measuring the distance, and  for the dynamics and estimates of the dark matter content. ESO Vitacura – Nov 2005 Dante Minniti

Discovery of new NGC5128 globular clusters. UV photometry shows a bimodal color distribution. For the 1st time in an E galaxy construct a deep globular cluster LF down to MV = -5 (Rejkuba 2001 A&A). ESO Vitacura – Nov 2005 Dante Minniti

Selection of GCs The globular clusters are resolved with ~1” seeing, allowing their discrimination from foreground MW stars. ESO Vitacura – Nov 2005 Dante Minniti

Comparative globular cluster luminosity functions Rejkuba 2003 Similar luminosity distributions with the systems of GCs of the MW and M31: unimodal, same peak at Mv~-7.5, maybe larger magnitude dispersion. ESO Vitacura – Nov 2005 Dante Minniti

NGC5128 globular cluster colors The globular cluster colors are bimodal  two different populations: metal-rich and metal-poor globular clusters in NGC5128 (Rejkuba 2001, Peng et al. 2004) ESO Vitacura – Nov 2005 Dante Minniti

Kinematics of the NGC5128 globular cluster system Comparison with the PN kinematics The GC and PN kinematics are similar The NGC5128 halo is slowly rotating The velocity dispersion is large Difference between metal-poor and metal-rich GCs Peng et al. 2003, 2004 ESO Vitacura – Nov 2005 Dante Minniti

Population of star clusters Plus a lot of young and intermediate age clusters in the dust ring! ESO Vitacura – Nov 2005 Dante Minniti

4. Globular Cluster Planetary Nebulae in NGC5128 ESO Vitacura – Nov 2005 Dante Minniti

Globular Cluster Planetary Nebulae GCPN are extremely rare (Jacoby et al. 1997). There are only 4 GCPN known in the Milky Way, but stellar evolution predicts a total of 16 GCPN in 150 GC. Large numbers of GCPN should be found in other gE galaxies, which have much larger GC systems. For example, the NGC5128 has 1700 GC in total (Kissler-Patig 1997), so there should be 50 – 200 GCPN in total in NGC5128. Where are they ? ESO Vitacura – Nov 2005 Dante Minniti

ESO Vitacura – Nov 2005 Dante Minniti

Magellan I B&C slit G292 G619 ESO Vitacura – Nov 2005 Dante Minniti

NGC5128 - G619 ESO Vitacura – Nov 2005 Dante Minniti

Substracting the spectrum of the comparison cluster gives a typical planetary nebula spectrum (D. Minniti & M. Rejkuba, ApJ 2002) [OIII] lines have F5007/F4959 ~ 3 F5007 = 6e-16 erg/sec/cm2/A M5007 = 24.3 V[OIII] = 702 km/s The spatial and velocity match rule out a background object G619 spectrum – G292 spectrum ESO Vitacura – Nov 2005 Dante Minniti

Follow-up spectroscopy with the ESO VLT in service mode acquired in June 2002. ESO Vitacura – Nov 2005 Dante Minniti

A 3rd GCPN candidate is discovered in the VLT data ESO Vitacura – Nov 2005 Dante Minniti

1st GCPN ESO Vitacura – Nov 2005 Dante Minniti

3rd GCPN RV reveals that this is just a chance superposition with a MW dwarf star. ESO Vitacura – Nov 2005 Dante Minniti

Extragalactic Globular Cluster PNe Why are they important? Dark matter in Elliptical galaxy halos (Richtler et al. 2002) GC and PNe abundances (Walsh et al. 1999) PNe lifetimes (Pottasch 1984, Renzini 1999) ESO Vitacura – Nov 2005 Dante Minniti

The first extragalactic GCPN (D. Minniti & M. Rejkuba, ApJ 2002) ESO Vitacura – Nov 2005 Dante Minniti

5.Identification of X-Ray Point Sources in Cen A ESO Vitacura – Nov 2005 Dante Minniti

X-Ray Point Sources in NGC5128 Kraft et al. (ApJ 2002) detected 246 point sources with LX [0.4-5 keV] > 2x1036 erg/sec in NGC5128. Most should be X-ray binaries and SN remnants. The sources with LX [0.4-5 keV] > 5x1037 erg/sec are much more numerous than in our MW and M31. For NS one needs an accretion rate of 10-8 Mo/yr. The most luminous could be multiple sources (7-8 expected), or BHs, or ?? Most sources are variable. ESO Vitacura – Nov 2005 Dante Minniti

CHANDRA images, 2 ACIS pointings Jet towards one side Point sources Diffuse emission CHANDRA images, 2 ACIS pointings (Kraft et al, ApJ 2002) ESO Vitacura – Nov 2005 Dante Minniti

Globular Cluster X-Ray Sources: The MW X-ray sources in GCs are extremely rare (Verbunt+ 1995, A&A). “Bright” sources are defined with LX > 1035.5 erg/sec. There are only 14 GC X-ray sources known in the 150 GCs of the Milky Way, and only 1 with LX > 1037 erg/sec. In M31 there are 30 GC X-ray sources (Di Stefano+ 2002, ApJ). ESO Vitacura – Nov 2005 Dante Minniti

Globular Cluster X-Ray Sources: Other Galaxies High luminosity X-ray point sources in distant galaxies are supposed to be X-Ray binaries or SN remnants. Large numbers of GC X-ray sources should be found in gE galaxies, which have more populated GC systems. For example, NGC5128 has 1700 GC in total, so there should be 150 bright GC X-ray sources in NGC5128. Only 9 were known (Kraft et al. 2002, ApJ). We find 30, including 23 newly discovered globular clusters (Minniti, Rejkuba & Funes 2003, ApJ). ESO Vitacura – Nov 2005 Dante Minniti

1` = 1 kpc 7x7 kpc ESO Vitacura – Nov 2005 Dante Minniti

1` = 1 kpc 7x7 kpc ESO Vitacura – Nov 2005 Dante Minniti

1` = 1 kpc 7x7 kpc ESO Vitacura – Nov 2005 Dante Minniti

1` = 1 kpc 7x7 kpc ESO Vitacura – Nov 2005 Dante Minniti

Identification of X-Ray Sources RESULTS Kraft+ Us Area NXPS NOPT NGC NStars Ha 1500 sq.arcmin 246 17 9 8 --- 50 sq.arcmin 97 52 30 10 Vast improvement in the optical ID of X-ray point sources in NGC 5128. Several of the sources are associated with GCs. These GC X-ray sources should be very bright LMXRBs (LX>1037 erg/sec). ESO Vitacura – Nov 2005 Dante Minniti

Colors and magnitudes of GCs with X-ray sources  X-Ray point sources appear preferentially in red (metal-rich) globular clusters.  X-Ray point sources appear preferentially in bright (massive) globular clusters. Minniti et al. 2003 ESO Vitacura – Nov 2005 Dante Minniti

30 X-Ray point sources in NGC5128 globular clusters Why are they important? Census of the X-ray point source population Identification of new GCs Accelerated dynamical evolution of GCs in gEs Trend of Lx with galaxy luminosity ESO Vitacura – Nov 2005 Dante Minniti

LMXRBs in NGC5128 GCs (Minniti, Rejkuba & Funes 2003, ApJ). ESO Vitacura – Nov 2005 Dante Minniti

6. Searching for Binary Star Clusters in Cen A ESO Vitacura – Nov 2005 Dante Minniti

wCen Some bright globular clusters in the Milky Way and M31 have composite populations. For example, color-magnitude diagram studies find a range of metallicities-ages in the largest globular cluster of the MW, wCen. Three theories: Nucleus of a stripped dwarf galaxy. Self enrichment. Merger of two clusters. ESO Vitacura – Nov 2005 Dante Minniti

CTIO 4m Ha images ESO Vitacura – Nov 2005 Dante Minniti

A Binary GC in NGC5128 ? The giant HII region Sersic 13 has LHa = 39.6 erg/s. The spectra of the young clusters exhibit broad WR features like R136 in 30 Dor in the LMC. The projected separation is DS = 42 pc. Compare with Rroche = 26 pc and Rtidal = 70-120 pc. The velocity difference is DV = 49+/-21 km/s. If bound, one expects Vorb = 10 km/s. If they are a physical pair, they will merge in a short timescale comparable with Porb = 107 yr. The optical magnitudes and spectra give M = 1-10x105 Mo. (Minniti et al. 2004, ApJ, Villegas et al. 2005, A&A) ESO Vitacura – Nov 2005 Dante Minniti

The Large Magellanic Cloud R136 in 30 Doradus “The Tarantula Nebula” ESO Vitacura – Nov 2005 Dante Minniti

A Binary GC in NGC5128 ? The ionizing source of the giant HII region Sersic 13 appears to be a pair of massive clusters. The luminosities and spectra of these young clusters are similar to R136 in 30 Dor. The velocity difference is small enough to suggest a physical binary. If they are bound, they will merge in a short timescale. The progenitor of an wCen like globular cluster ? (Minniti et al. 2004, ApJ, Villegas et al. 2005, A&A) ESO Vitacura – Nov 2005 Dante Minniti

NGC 5128 - Centaurus A 1. Stellar populations 2. Variable Stars 3. Star Clusters 4. New GC PNe 5. X-Ray Sources 6. Binary Clusters 7. Supermassive BH 8. Inner structure ESO Vitacura – Nov 2005 Dante Minniti