Galactic X-ray Surveys and Galactic X-ray Source Populations Bob - PowerPoint PPT Presentation

Galactic X-ray Surveys and Galactic X-ray Source Populations Bob Warwick University of Leicester X-ray Astronomy Group

PART I - Galactic X-ray Surveys A Brief Overview

X-RAY ALL-SKY SURVEYS circa late-1970 ’ s THE FOURTH UHURU CATALOG OF X-RAY SOURCES Forman et al (1978) 339 sources THE ARIEL V (3A) CATALOGUE OF X-RAY SOURCES: Warwick et al (1981) McHardy et al (1981) 250 sources Galactic Coordinates “Classical” hard X-ray 2-10 keV band

HEAO 1 A1 All-Sky Survey Aug 1977-Jan 1979 2-10 keV V711 Tau SS Cyg 842 sources Wood et al. (1984)

XMM Slew-Survey – Source “ Pseudo ” All-Sky coverage of XMM Catalogue Slew-Survey (0.3-12 keV) XMMSL1- Delta6 ~65% sky coverage total of ~20000 sources 2160 in 2-10 keV band Saxton, Read et al

INTEGRAL/IBIS All-sky Survey 17-60 keV Krivonos et. al., 2007 plus up-dates Krivonos et al. 2012 – the low latitude sample

The 70 month Swift-BAT All-sky X-ray Survey 14-195 keV Galactic Source Statistics: High Mass X-ray Binary (HMXB) - 85 Low Mass X-ray Binary (LMXB) - 84 Other binary - 17 Star - 14 Supernova Remnant (SNR) - 6 Cataclysmic variables (CV) - 55 Pulsars - 20 1171 sources Baumgartner et al. 2013

ROSAT All-Sky Survey in the soft X-ray (0.1-2.4 keV) band ROSAT BSC - 18,811 sources- Voges et al. 1999

X-ray emission across the HR diagram RS CVn Binaries Stellar Winds Active Coronae Gudel 2004

The "next-generation" all-sky survey eROSITA LMXB HMXB Spectrum-Roentgen-Gamma Satellite Prospective Launch date: 2017 Doroshenko et al. 2014

Galactic X-ray Surveys via Multiple Pointings ASCA Galactic Plane Survey within | l | < 45 o 0.7-7 keV ASCA Galactic Plane Survey (-45<l<45); Sugizaki et al. (2001) 163 sources with Fx > 10 -13 erg/s/cm 2

Studying the Galactic Plane with XMM-Newton XGPS Survey I = 19-22 o ; Hands et al 2004; 424 sources; Fx > 2 x 10 -14 erg/s/cm 2 XMM-Newton SSC programme included a ground-based follow-up programme focused on a bright subset of the XGPS sources - Motch et al. (2010)

Combination of three surveys ASCA – Sugizaki et al 2001 XMM – Hands et al 2004 Chandra – Ebisawa et al 2005 2 x 100 ks l = 19 o -22 o l = 28.5 o

Observed 2-10 keV Source Counts in the Galactic Plane Chandra XMM ASCA extragalactic (abs. corrected)

Point sources detected by Chandra in the Galactic Centre > 30,000 sources per sq. deg Muno et al. 2004

The ChamPlane Survey of the Galactic Bulge Region J,H,K Glimpse 3.6 X-ray micron Grindlay et al 2005; Koenig et al 2008; Hong et al 2009; van den Berg et al. 2009; van den Berg et al. 2012

Chandra Survey of the Norma Spiral Arm 20 ks pointings covering 2 o x 0.8 o Fornasini et al. 2014 1415 sources

Serendipitous Source Catalogues Swift  1SXPS 1905 deg 2 151,524 sources Evans P. et al. 201 4 XMM  3XMM-DR5 877 deg 2 396910 sources Rosen et al. 2015 Chandra  CSC-V1.1 106,528 sources Evans I. et al. 2010

PART II - Galactic X-ray Source Populations 1 1 focusing on the 2-10 keV band and intermediate-to-low Lx sources

The Diversity of Source Types High luminosity (Lx ~ 10 35-39 erg/s) X-ray binaries powered by accretion onto either a NS or BH • HMXB (Supergiant XRBs, SFTs, Be-star XRBs etc..) • LMXB (Atoll, Z; Bursters, Dippers, ADC etc..)

The Diversity of Source Types Intermediate-to-low (Lx ~ 10 27-35 erg/s) luminosity sources: • XRBs (qLMXB, γ Cas, Symbiotics) • CVs (Dwarf Novae, IPs, Polars, Symbiotics) • SNRs + PWN + PULSARS (radio, msec, AXPs, SGRs) • HOT STARS (WR, O Supergiants, Col. Wind Binaries) • COOL STARS (F-M, Active binaries - BY Dra, RS CVn) • Pre-MS (Protostars, T-Tauri )

What we would like to know about each defined sub-class: • Detailed X-ray properties – spectra & timing • Nature of the Optical/IR counterparts  • Distances  intrinsic properties such as L X • "Completely" identified samples combined with a spatial distribution model  • X-ray Luminosity Function(XLF) [ dN/dL X = No. of sources per unit L X per pc 3 ]

Observational Hurdles Within the Galaxy: There is the wide angular scale and the high extinction and high stellar density in the Galactic Plane. These hamper the definition of "complete" samples, the identification of the counterparts in the optical/IR and the determination of the source distance. For external galaxies: The distance is known but only the most luminous X-ray sources are resolved 1 and the optical/IR follow-up is limited to high-mass stellar counterparts. 1 For Chandra the threshold Lx outside of the Local Group is typically > 10 36-37 erg/s.

The XLF of Galactic LMXB & HMXB – follow the "Universal" form HMXB Trace star formation T evol ~ 1-10 Myr LMXB Trace stellar mass T evol ~ 1-10 Gyr Gilfanov 2004

2-10 keV XLFs of the Intermediate/Old Binary Source Populations in the Galaxy LMXB + CVs + Active Stellar Binaries (ABs) Number of sources in the Galaxy per log Lx bin Contribution to total 2-10 keV luminosity of the Galaxy ~3% Sazonov et al., 2006 Revnivtsev et al., 2006 2-10 keV

The Galactic Ridge X-ray Emission (GRXE) HEAO-1 circa ~1982 EXOSAT circa ~1985 RXTE - contours circa ~2006

X-ray Spectrum of the GRXE ASCA GIS 6.7 keV iron line kT ~ 0.8 keV kT ~ 8 keV Cosmic X-ray Background Cool component kT ~0.8 keV Kaneda et al. 1997 Above 4 keV: • Hard thermal continuum (kT ~ 5 keV) • He-like and H- like Fe Kα lines (6.67/6.96 keV)

Origin of the GRXE Emission of Very hot diffuse unresolved sources plasma Cool component kT ~0.8 keV Unbound  Needs What Galactic source 10 43 erg s -1 to replenish? population(s)?

Resolving the Galactic Ridge X-ray Emission in a 1 Msec Chandra Observation Revnivtsev et al., 2009 Sources – Integrated Spectrum [Hong 2012; Morihana et al. 2013] ~ 80,000 sources per deg 2 Resolved Fraction of GRXE Revnivtsev et al., 2009

Exploring the X-ray Source Population in the Galactic Plane at Faint Fluxes (in the 2-10 keV band)  We assume that coronally active single stars and active binaries (ASBs) and cataclysmic variables (CVs) dominate.  Use a new hard-band selected sample taken from the high-latitude (|b| > 10 o ) XMM Slew Survey [Warwick 2014]  Transpose the results to the Galactic Plane assuming a 150 pc z-scale height and R disc =2.2 kpc for both populations

The XSS hard-band selected sample ★★★ The 46 ASBs  coronally- 46 ASBs active stars and binary coronally-active 16 CVs systems stars and binaries are preferentially observed in the 2-10 16 CVs  magnetic & non-magnetic keV band during cataclysmic variables flare states . ★★★ Spectral Assumptions: Count/s  X-ray flux  X-ray luminosity ASBs: kT = 3.5 x 10 7 K (3 keV) apec plasma with Z=0.4 Z  CVs: kT = 10 keV thermal bremsstrahlung + Fe lines

Derived X-ray Luminosity Functions Lx / pc 3 / M  46 ASBs Local space density Local volume of ASBs: emissivity of ASBs: 16 CVs = 3.4 ± 0.5 x 10 -3 pc -3 = 1.08 ± 0.16 x 10 28 erg/s (2-10 keV) / M  Local space density Local volume of CVs: emissivity of CVs: = 3.4 ± 0.7 x 10 -5 pc -3 = 2.5 ± 0.6 x 10 27 erg/s (2-10 keV) / M  [Referenced to a local mass density of 0.04 M  / pc 3 Warwick 2014

"Template" 2-10 keV X-ray Luminosity Functions Lx / pc 3 / M  ASBs CVs XRBs  Sazanov et al (2006) XLF [Referenced to a local mass Warwick 2014 density of 0.04 M  / pc 3

Predicted 2-10 keV Source Counts in the Galactic Plane (at l = 28.5 o ) ASBs CVs XRBs  extragalactic sources coronally-active stars and binaries dominate at faint levels TOTAL Warwick 2014

Observed 2-10 keV Source Counts [normalized to (S X /10 -14 ) -1.5 ] ASCA XMM Chandra ~1600 per deg 2 (corrected) ~600 per deg 2 (raw) Warwick 2014

Observed Versus Predicted Source Counts [normalized to (S X /10 -14 ) -1.5 ] ASBs CVs XRBs   extragalactic sources TOTAL Warwick 2014

Matching the measured intensity of the GRXE in the 2-10 keV band (= 4.8 x 10 -11 erg/s/cm 2 /deg 2 - Ebisawa et al 2008) ASBs CVs XRBs Total Active Stars  78 +/- 12 % CVs  16 +/- 4 % Total  94 +/- 13% Warwick 2014

Matching the X-ray spectrum of the GRXE Suzaku l=28.46 o b=-0.2 o Ebisawa et al. 2008 Fe-K Line Equivalent Widths 6.4-keV line  80 +/- 20 eV 6.67-keV line  350 +/- 40 eV 6.96-keV line  70 +/- 30 eV

Matching the measured equivalent widths of the 6.4 keV/6.7/6.9-keV Fe-K lines 20% contribution from CVs • [EW 6.4 ~ 75 eV; EW 6.7 ~ 150 eV; EW 6.9 ~ 100 eV] 60%+ contribution from ASBs 1 • [EW 6.4 ~ 0 eV; EW 6.7 ~ 400 eV; EW 6.9 ~ 70 eV] 10%+ contribution from scattered • radiation in the ISM [Molaro et al. 2014] [EW 6.4 ~ 1000 eV; EW 6.7 ~ 0 eV; EW 6.9 ~ 0 eV] 1 Assumes kT ~3-5 keV and Z  ~ 0.4 for the coronal flares 39

Part III - The challenge of identifying IR/optical counterparts in the Galactic Plane