1. Populations of X-ray sources Populations of X-ray sources in star-forming galaxies in star-forming galaxies Roberto Soria (MSSL) K Wu, A Kong, M Pakull, R Kilgard, D Swartz

2. Contents  ”ultra-luminous sources”  different physical classes of X-ray sources what they are and how to test the models case studies: M83, NGC300, M74, NGC 4449 multiwavelength comparisons  luminosity and colour distributions and what they tells us about the host galaxy  introduction why studying X-ray sources in other galaxies

3. Why studying X-ray sources in galaxies  understand the properties of individual X-ray sources  do statistical studies of X-ray source populations spectra, lightcurves, state transitions,... spatial distribution luminosity & color distribution different classes of compact objects  use discrete X-ray sources and diffuse emission as a tool to understand galactic activity and evolution

4. STAR FORMATION Stellar evolution PNe, SNe II, Ib/c Compact remnants HMXB, LMXB Cold gas Hot gas (shocks) Diffuse soft X-rays X-rays from accretion External triggers Internal triggers?

5. luminosity (count rate) distribution spatial distribution, multi-band comparisons/identification colour distributions for different classes of sources Basic steps: Distinguish different physical types of X-ray binaries, SNR, SNe Determine: Use X-ray sources as probes of galaxy structure and evolution

6. Cumulative luminosity distribution of the discrete X-ray sources in a galaxy 10 40 10 38 10 36 N(>L) L “normal” spiral population Starburst/star-forming regions Ellipticals erg/s

7. Breaks in the luminosity distribution Luminosity functions in M83Luminosity functions in M81 Breaks/features in the luminosity function may depend on:  Eddington limit for the neutron stars distance indicator  ageing of the X-ray binary population (Wu 2001) galactic history indicator outside disk starburst nucleus

8. A look in detail: M83 (d ~ 4 Mpc)

11. 10 arcsec

12. Super-soft source Wind / XRB? X-ray binary galactic nucleus SNR?

13. ULX X-ray pulsar

14. Starburst nucleus Spiral arms High abund of Ne, Mg, Si,S Low Fe/O, Fe/C High C/O ISM may be enriched by: winds from WR stars, core-collapse SNe T ~ 0.6 keV T ~ 0.4 keV

15. Identification of the X-ray sources: multiwavelength comparisons Chandra/ACISHST/WFPC2

16. HST/WFPC2 greyscale, Chandra contours

17. H  greyscale (SSO), Chandra contours (0.3--8 keV)

18. V-band greyscale (VLT), 6 cm radio contours (VLA)

19. Colour-colour plot for bright M83 sources

20. Supersoft sources Soft sources (SNR +) X-ray binaries (BH, NS)

21. Candidate X-ray SNR are associated to brighter HII regions HHHH

22. H  greyscale (SSO), Chandra point sources

23. 6 cm radio greyscale (VLA), Chandra point sources

24. many SNR in M83, fewer in M81...

25. ...almost none in M31 Courtesy of S Trudolyubov et al, 2003 submitted

26. NGC 300 XMM OM image (UV filters)

27. NGC 300 XMM OM image (UV filters)

28. Optical SNRs Radio SNRs

33. Comparing samples of SNR radio  radio-identified SNR: dense HII regions core-collapse SNe (young population) optically  optically-identified SNR: low-density regions mostly Type Ia (old population) X-ray  X-ray SNR: both, but brighter when associated to radio SNR Radio + X-ray (+ optical) X-ray + optical 10 36 erg/s L Core-collapse Type Ia

34. (Young) core-collapse X-ray SNe thermal spectrum:  thermal spectrum: emission from hot, shocked gas non-thermal spectrum:  non-thermal spectrum: dominated by synchrotron radiation (power-law spectrum) SN in NGC 4449 SN 1978k in NGC 1313

35. SN2002ap in M74 seen by XMM Colour distribution for M74

36. Thermal X-ray emission from SNe  High mass loss rate, low velocity wind, low velocity ejecta (< 30,000 km/s) L > ~ 10 38 erg/s fr H S Hard X-rays first Soft X-rays later (weeks/months) Optically thick cool shell SN 1993J Type II

37. Thermal X-ray emission from SNe  Low mass loss rate, high velocity wind, low velocity ejecta (< 30,000 km/s) L ~ 10 37 erg/s fr (H) S Hard X-rays negligible Soft X-rays always visible Optically thin cool shell SN 2002ap Type Ib/c

38. Thermal X-ray emission from SNe  Relativistic ejecta? (> 100,000 km/s?) fr H,  S Hard X-rays,  rays (Hypernova?) Type Ib/c SN 1998bw

39. Thermal X-ray emission from SNe  Relativistic ejecta? (> 100,000 km/s?) f H,  Hard X-rays,  rays (Hypernova?) Type Ib/c SN 1998bw

40. “Ultra-luminous” sources 2 x 10 38 10 39 Neutron stars Black holes SNR 10 40 Black holes SNR ”ULX” Emitted luminosity > Eddington limit for M = 7 M sun

41. NGC 4449

42. X-7 X-1

43. X-7

44. 1 arcsec X-1

45. ~ 0.6 X-1: diskbb (T col ~ 0.6 keV) ~ 2.6) + pow (  ~ 2.6) ~ 2.1) X-7: pow (  ~ 2.1)

46. Where are they? Found in 20% of spiral galaxies 40% of ellipticals (7 in Fornax A, 6 in NGC 1553) most tidally-disrupted starburst (10 in Antennae) Very old populationsVery young populations Variability? All are persistent Most variable by a factor of a few (over hours/yrs) Long duty cycle? If so, how many quiescent sources? State transitions? Some similarities with Galactic BH (Roberts et al 2000)

47. X-ray spectrum? Most are fitted by diskbb with scattering ~~ 1 T T col = f T eff where f ~ 1.5 – 3; T col ~ 1 keV Others are fitted by a simple power-law T col = 1.1 keV, L x = 2.7 x 10 39 erg/s X-6 in M 81 (Swartz et al 2002) ~ 0.07 ~ Some are “super-soft”, T ~ 0.07 keV, L bol ~ 10 39 erg/s A few can be identified as SNR

48. Three possibilities for accreting ULX M > 10 M sun, L < L edd IMBH ~~ M ~ 10 M sun, L >~ L edd ~~ M <~ 10 M sun, L <~ L edd beamed Problem not settled yet, need better observations Super-E

49. Intermediate-mass BH: how to form them? 1...and how to observe them? Optical counterparts, lightcurves, accretion disk lines obtain mass function  primordial (see eg Rees) feeding -- from a molecular cloud? (Grindlay) -- by capturing a companion?  in globular clusters from SN explosion of very massive stars? (from merging of many smaller BH?) NO. Ineffective because of slingshot effect  in super star clusters ( = young globular clusters?) from merging of many stars  star of 500 M sun  sinks to the cluster centre  SN  IMBH? (eg, Ebisuzaki et al 2001)

50. “Super-Eddington” sources (not really) 2 L edd = (4  cG) M /  = 1.3 10 38 (M/M sun ) (0.40/  F rad (L=L edd ) = F grav Thomson scattering opacity Effective opacity for clumpy medium < for homogeneous medium Shaviv 1998 Witt & Gordon 1996 Isichenko 1992 (“percolation theory”) Accretion disks around BH (Begelman 2002) Classical novae (Shaviv 2001) Wolf-Rayet, supergiant stars,  Car (Shaviv 2000) Dust scattering in clumpy ISM (WG96) Super-soft sources? AGN? Starburst galaxies? Where to observe this? Look out for winds

51. Non-isotropic emission: how to beam it? 3...and how to verify if it is beamed? Optical (narrow-band) observations of X-ray ionized nebulae around ULX can tell us whether X-ray source is beamed (Pakull & Mirioni 2002) Thermal-timescale mass transfer phase? high mass transfer rate beaming? Analogy with Galactic microquasars/microblazars (King et al 2001) (Fabrika et al 2000)

52. New pieces of the ULX puzzle Colours/spectra, time variability, spatial distribution consistent with normal X-ray binaries 1

53. New pieces of the ULX puzzle Most ULXs are in interacting/merging galaxies (Swartz et al 2003) 2 Many ULXs are in low-metallicity environments (see Pakull’s work) 3 Tidal interactions  higher star formation Weaker stellar wind  higher mass of the BH remnant 4 ULXs in star-forming galaxies are young objects Optical counterparts are O stars, OB associations

54. M81 group (many ULXs)

55. NGC 4449 (2 ULXs)

56. Most likely explanation for ULXs? a 30-50 M sun BH accreting from an O star via Roche-lobe overflow Work in progress by Podsiadlowski, Heger, Langer, etc ~ L x <~ L edd L x =  M c 2

57. Most likely explanation for ULXs? a 30-50 M sun BH accreting from an O star via Roche-lobe overflow (LMXB)  NS or BH accreting from a low-mass star via Roche-lobe overflow (LMXB) (HMXB)  NS or BH accreting from a high-mass star via stellar wind (HMXB) (ULX + LMC X-4)  NS or BH accreting from a high-mass star via Roche-lobe overflow (ULX + LMC X-4) Three classes of X-ray binaries?

58. Statistical studies of X-ray populations (XRB, SNR, SSS, ULX) Star-formation in nearby galaxies Studies of individual sources Groups of galaxies X-ray studies of high-redshift galaxies