Front X-ray Studies of Galaxies and Galaxy Systems Jesper Rasmussen Ph.D. Defence Astronomical Observatory, Univ. of Copenhagen 17th March 2004

Outline Background: X-rays from galaxy systems XMM-Newton observations of two galaxy groups X-ray haloes of simulated disk galaxies Chandra observations of a dwarf starburst galaxy Summary

Collaborators, papers Papers (1) Groups: Rasmussen & Ponman (2004), MNRAS, in press (2+3) Disk galaxies: Rasmussen, Sommer-Larsen, Toft, Pedersen (2004), MNRAS, 349, Toft et al., 2002, MNRAS, 335, 799 (4) XMM simulations: Rasmussen, Pedersen, Götz (2004), astro-ph/ (5) Dwarf starburst: Rasmussen, Stevens, Ponman (2004), in preparation Main collaborators : Kristian Pedersen, Sune Toft ( AO, Copenhagen ) Jesper Sommer-Larsen, Martin Götz ( TAC, Copenhagen ) Trevor Ponman ( Univ. of Birmingham, UK )

X-rays from galaxy systems  Formation of structure : Gas infall in dark matter halo, compression and (shock) heating of gas. Evolution of structure : Processes affecting hot gas properties (galaxy winds, nuclear outflows, cooling, …) Galaxies : Violent processes in the interstellar medium, interactions with environment… Cosmology : Detection of distant systems; gas (baryon) content  constraints on Ω m X-ray emission : Thermal emission from hot (~ 10 7 K ) gas.

Outline XMM-Newton observations of two galaxy groups X-ray haloes of simulated disk galaxies Chandra observations of a dwarf starburst galaxy

X-rays from two galaxy groups Two groups, at z = 0.18 and z = 0.256, selected from ROSAT pointed observations. XMM-Newton 22 ks exposure (single pointing) Goal : Study large-radius properties of groups for the first time. Smoothed keV image (all 3 XMM/EPIC cameras).  15 arcmin  1 2

Groups: X-ray + optical WARPS, I-band WARPS, R-band Dig. Sky Survey 12

Groups: Results Fitting of thermal plasma models to spectra: Surface brightness fit using  -model: β = 0.49 r c = 75 kpc (h = 0.75) Extent = 570 kpc kT = 1.7 +/- 0.1 keV Z = 0.3 +/- 0.1 Z sun β = 0.62 r c =170 kpc Extent = 650 kpc kT = 2.4 +/- 0.4 keV Z = 0.3 +/- 0.2 Z sun T   -1 12

Groups: Implications Entropy, S = T/N e 2/3 1. M = (5.1+/- 0.5) x M sun, r det /r 200 = M = (1.0+/- 0.2) x M Sun, r det /r 200 = 0.66 {  ~0.14 & ~0.17 (h=0.75) Gas mass fraction 1 2

Groups: Summary X-rays detected to ~ 0.7 r 200 in two X-ray bright groups. Gas mass fraction rises with radius, global value similar to clusters  Groups could contain many more baryons than is often supposed (could help solve the ”missing baryon” problem) Entropy distribution : (1) confirms: groups are not ”downscaled clusters” (2) rules out simple formation scenarios that assume pre-heating and smooth accretion of gas.

Outline XMM-Newton observations of two galaxy groups X-ray haloes of simulated disk galaxies Chandra observations of a dwarf starburst galaxy

Disk galaxy halos Idea: Use cosmological simulations to compute X-ray properties of hot halos of disk galaxies. (1) z = 0 (Toft et al. 2002)  agreement with observations. (2) Here predict evolution with redshift for MW-like galaxies. Cosmological simulations: Sommer-Larsen et al (2003). Include star formation, feedback, radiative cooling, UV radiation.

Disk galaxy halos: L x vs z Accretion rate of cold (T < 3 x 10 4 K) gas onto disk : Simulations  L X

Disk galaxy halos: High-z constraints Hornschemeier et al. 2002: ________ CDF-N spectroscopic sample CDF-N photometric sample Chandra Deep Field North: 1 Ms (covers Hubble Deep Field-N)

Halos: Detection prospects > 10 halos per deg 2 (to z = 0.3 in 1 Ms)  Surface brightness vs vertical disk distance | z | XEUS 10% of MW-like galaxies to z=0.3

Halos: Summary Halo L x increases 5-10 times from z = 0 to z = 1. Reflects the evolution of accretion rate of cold gas onto the galactic disk. Evolution in agreement with deep X-ray data. Detection of halos of Milky Way-like galaxies at cosmological distances must await the next generation of X-ray instrumentation.

Outline XMM-Newton observations of two galaxy groups X-ray haloes of simulated disk galaxies Chandra observations of a dwarf starburst galaxy

NGC1800: An embedded starburst NGC1800 : Dwarf starburst galaxy, D ~ 7 Mpc. Galaxy group : 6 members, σ = 260 km/s. Chandra /ACIS 45 ks exposure NGC1800, B -band, 6 x 6 arcmin D 25 (25 mag/arcsec 2 ) Goal : Study interactions between galactic wind and ambient gas – is wind confined?

NGC1800 observations - or ”how X-ray data can also appear” keV raw image

NGC1800 – diffuse X-rays kT = /-0.03 keV (1σ) Z = /-0.04 Z sun (1σ) Extent ≈ 2 kpc L x = 1.3 +/- 0.3 x erg/s keV, adaptively smoothed X-ray/optical overlay Results from thermal model fit: D 25 D spec ~ 2kpc

NGC1800 group But ”no” detection (~100 counts/CCD)  L X < erg/s L X - σ relation ( ROSAT ) + σ - T relation  Expectation: kT ~ 0.7 keV L X ~ 1.5 x erg/s ~ 1500 counts/CCD

NGC1800: Wind blow-out? VLA HI map (Hunter et al. 1994) N H : 0.5  11 x cm -2 Blow-out criterion : > 1 (Mac Low & McCray 1988 – blast wave dynamics in stratified atmosphere) 1' ≈ 2 kpc

NGC1800: Wind  IGM Freely expanding wind : n e  r - α, α = 2 ( Chevalier & Clegg 1985 )  Galactic starburst wind confined by the IntraGroup Medium (IGM)? (P IGM < P wind ) Conical geometry : S  r  α  1.2. But M82 & NGC253 : α  0.9 & 1.3 …so no clear evidence of wind confinement.

X-rays from dwarf starbursts X-ray activity vs ”mass”X-ray activity vs star formation activity Gas temperature vs ”mass”

NGC1800: Summary NGC1800: Most distant dwarf starburst with detection of diffuse X-ray emission. X-ray gas can probably leave the galaxy - but no clear evidence for wind-IGM interaction (and no detection of hot gas in the group). X-ray emission from dwarf starbursts governed by starburst activity rather than mass of host galaxy.

Summary: Results Groups X-rays detected to ~ 0.7 r 200. Gas mass fraction rises with radius, global value similar to clusters. Entropy distribution rules out certain formation scenarios. Disk galaxy halos Halo L x increases 5-10 times from z = 0 to z = 1. Evolution in agreement with deep X-ray data. Dwarf starburst Most distant dwarf with diffuse X-rays. No clear evidence for wind-IGM interaction. X-rays from dwarf starbursts governed by starburst activity. XMM sim’s Versatile tool for a variety of applications. Small clusters detectable to z > 1 in 10 ks.

Halos: Detection prospects Circular velocity V c : ”generalized” Schechter function: + > 10 halos per deg 2 (to z = 0.3 in 1 Ms)  Surface brightness vs vertical disk distance | z | XEUS 10% of MW-like galaxies to z=0.3

Summary: Comparison of sources Bolometric L X, Ω m = 1, Ω Λ = 0, h = 0.5

Outline XMM-Newton observations of two galaxy groups X-ray haloes of simulated disk galaxies Chandra observations of a dwarf starburst galaxy Simulating XMM-Newton observations

XMM simulations: Setup Source field setup : Clusters from Press-Schechter and N-body sim’s, point sources, backgrounds. Method : Input to SciSim (ray-tracing software), construct data sets from output. Motivation : Distant clusters in XMM ”blank-sky” pointings? (but many other possible applications)

XMM simulations: Example (test) 20 ks exposure of T ~ 5 keV cluster at z = 0.6

XMM simulations: Blank-sky Input source field, 30 x 30 arcmin0.5-2 keV output image (all EPIC) Wavelet detections, > 6σ