What do we know about the HISM?

Sun

For a review, see D. Cox (2005, ARAA)

ROSAT X-ray All-sky Survey

Red – 1/4 keV band

Green – 3/4 keV band

Blue – 1.5 keV band

~50% of the ¾-keV background is thermal and local (z < 0.01); rest is mostly from AGNs

McCammon et al. 2002

What we do not know:

• Overall spatial distribution• Filling factor• Physical and chemical states• Kinematics

• Heating, transporting, and cooling• Effects on galaxy formation and

evolution

New Tool: Chandra

CCD

•resolution res. ~ 1”

•Spectral Res. E/E ~ 20

Grating

•Spectral Res. ~ 500 km/s

The Global Hot ISM: New Perspectives

Absorption spectroscopy:

• Add the depth • Measure the column

density, thus the mass• Direct line diagnostics• Independent of cool gas

absorption

External views:• Global properties• Relationship between

various components• Dependence on galaxy

properties and environment

Modeling of the SN-dominated hot ISM

• 1-D galactic bulge wind

• 3-D simulations

Detection of X-ray absorption lines:

Mrk 421; Nicastro et al. 2005

Mkn 421 3C 273

LETG/ACIS

LETG/HRC

Wang & Yao 2005

Where is the

absorbing gas

located?

LMC X-3 as a distance marker

• BH X-ray binary, typically in a high/soft state

• Roche lobe accretion• 50 kpc away• +310 km/s• Away from the LMC main body

H image

Obs. Of LMC X-3

•Chandra LETG: 100 ks.

•FUSE: 100 ks

•RXTE: 100 ks

Wang et al. 2005

LMC X-3: absorption lines

The EWs are about the same as those seen in AGN spectra!

OVII

Ne IX

Absorption line diagnostics

Assuming CIE and solar abundances

OVI

OVIIIOVII

Ne IX

Ne VIII

Ne IX

I()=Ic() exp[-()]

()NHfafi(T)flu(,0,b)

b=(2kT/mi+2)1/2

accounting for linesaturation and

multiple line detections

Yao & Wang 2005

Results from extragalactic sources

Source Log[T(K)] Log[NH(cm-2)]

PKS 2125-304 6.3(6.2-6.4) 19.8(19.5-20.3)

3C 273 6.3(6.1-6.4) 19.9(19.7-20.1)

MRK 421 6.2(6.1-6.3) 19.2(19.1-19.3)

LMC X-3 6.1(5.9-6.3) 19.6(19.4-19.8)

No evidence for significant X-ray absorption beyond the LMC!!!

LMXB 4U 1820-303:A Galactic distance marker

• In GC NGC 6624– Distance = 7.6; l, b = 2o.8, -8o

tracing the global ISM– 1 kpc away from the Galactic plane

NHI

• Two radio pulsars in the GC DM Ne

• Chandra observations:– 15 ks LETG (Futamoto et al. 2004)– 21 ks HETG

Yao & Wang 2005

LETG+HETG spectrum

4U 1820-303: Results• Hot gas accounts for ~ 6% of the total O column

density• O abundance:

– 2.0 (0.8-3.6) solar in ionized gas– 0.3 (0.2-0.6) solar in neutral atomic gas.

• Ne/O =1.4(0.9-2.1) solar • Filling factor (relative to total ionized gas):

~0.95, if ph ~ pw

~0.8, if ph ~ 5pw as in the solar neighborhood

• LogT(k) = 6.34 (6.29-6.41)• Velocity dispersion 255 (165–369) km/s

Temperature Dist.

d NH(T) = T

dlogT

More Sources Global HISM distribution

• LMXBs with |b| > 2o

• S/N > 7 per bin at ~0.6 keV• Excluding sources with identified

intrinsic emission/absorption features

• Ten LMXBs with 17 observations (6 with the LETG)

Yao & Wang 2005

Absorption Sight Lines

No detection X-ray binaryAGN

ROSAT all-sky survey in the ¾-keV

band

Global distribution models

Disk model

•nH = 5.0(-1.8,+2.6)x10-3 cm-3 exp[-|z|/1.1(-0.5,+0.7)

kpc]

•Total NH~1.6 x1019 cm-2

Sphere model

•nH = 6.1(-3.0,+3.6)x10-2 cm-3 exp[-R/2.7(-0.4,+0.8)

kpc] ~3 x 10-3 cm-3 at the Sun

•Total NH~6.1 x1019 cm-2

•MH~7.5(2.5-16)x108 MsunX-ray absorption is primarily around the Galactic disk within a few kpc!

Summary: Galactic hot ISM

• No significant X-ray absorption beyond the LMC (~< 1019 cm-2, assuming the solar abundance)

• A thick Galactic disk with a scale height 1-2 kpc, ~ the values of OVI absorbers and free electrons

• O abundance ~ solar or higher• Mean T ~ 106.3+-0.2 K, ~ 106.1 K at solar neighborhood• Large nonthermal v dispersion, especially at the GC• High volume filling factor (> 0.8) within |z| < 1 kpc

External Perspective: NGC 3556 (Sc)

Red – optical

Green – 0.3-1.5 keV band

Blue – 1.5-7 keV band

•Active star forming

•Hot gas scale height ~ 2 kpc

•Lx ~ 1% of SN mech. Energy input

Wang et al. 2004

NGC 4565 (Sb)

William McLaughlin (ARGO Cooperative Observatory)

Red – optical

Green – 0.3-1.5 keV band

Blue – 1.5-7 keV band

Wang (2004)

Very low specific SFR

No sign for any outflows from the disk in radio and optical

NGC 2841 (Sb)

Red: optical

Blue: 0.3-1.5 keV diffuse emission

NGC 4594 (Sa)

Red: optical

Green: 0.3-1.5 keV

Blue: 1.5-7 keV

H ring

NGC 4594:X-ray

spectraPoint source

Inner bulge

Outer bulge

disk

•Average T ~ 6 x 106 K

•Strong Fe –L complex

•Lx ~ 4 x 1039 erg/s

NGC 4631

Missing stellar feedback in early-type disk galaxies

• For NGC 4594, hot gas radiative cooling rate ~ 2% of the energy input from Type Ia SNe alone

• Not much cool gas to hide or convert the SN energy

• Mass and metals are also missing!– Mass input rate of evolved stars

~ 1.3 Msun/yr– Each Type Ia SN 0.7 Msun Fe

Galaxy formation simulations vs. observations

Toft et al. (2003)

NGC 4565

NGC 4594

NGC 4594

NGC 4565

Summary: Nearby galaxies• Good News

– At least two components of diffuse hot gas:• Disk – driven by massive star formation• Bulge – heated primarily by Type-Ia SNe

– Characteristic extent and temperature similar to the Galactic values

• Bad news– Missing stellar feedback, at least in early-type spirals. – Little evidence for X-ray emission or absorption from

IGM accretion --- maybe good news for solving the over-cooling problem.

Are these problems related?

Bulge wind model• Spherical, steady, and adiabatic • NFW Dark matter halo + stellar bulge• Energy and mass input follows the

stellar light distribution• CIE plasma emission• Implemented in XSPEC for both

projected spectral and radial surface brightness analyses

Li & Wang 2005

Data vs model

Consistent with the expected total mass loss and SN rates as well as the Fe abundance of ~ 4 x solar!

The best-fit model density and temperature profiles of the bulge

wind

3-D hydro simulations• Goals

– To characterize the density, temperature, and metal abundance structures, the heating and cooling processes, and the kinematics of the HISM

– To calibrate the 1-D model• Hydro simulations with metal particle tracers

– Parallel, adaptive mesh refinement FLASH code– Whole galactic bulge simulation with the finest

refinement in one octant down to 6 pc– Stellar mass injection and SNe, following stellar

light– Realistic gravitational potential of the bulge and

the dark matter halo

Galactic bulge simulation: density

• 3x3x3 kpc3 box• SN rate ~ 4x10-4 /yr• Mass injection rate

~0.03 Msun/yr• Logarithmic scale • Statistical steady

state• ~ adiabatic

Tang et al. 2005

Galactic bulge simulation: Fe• Fe-rich ejecta

dominate the high-T emission

• Not well-mixed with the ambient medium

• May cool too fast to be mixed with the global hot ISM

Non-uniformity effects

Log(T(K))

Low Res.

High

Res.

1-D

1-D

Conclusions and implications

• Large inhomogeneity is expected– particularly in the hot Fe distribution– enhanced emission at both low and high

temperatures (compared to the 1-D solution)

• SNe generate waves in the HISM– Energy not dissipated locally or in swept-up

shells– Maybe eventually damped by cool gas or in

the galactic hot halo– Galactic wind not necessary– Possible solution to the over-cooling

problem of galaxy formation

Acknowledgement

• Absorption line studies– Y. Yao, T. Tripp, T.-T. Fang, …

• X-ray imaging of nearby galaxies– T. Chevas, J. Irwin, Z. Li…

• 1-D and 3-D model and simulations– Z. Li, S. Tang, M. Mac Low

Comparison with X-ray emission

Disk dist.

Uniform dist.Observed

Consistency check: timescales

T/(dT/dt)

Radiative cooling

O recom.

Fe recom.

Dependence on the energy/mass input rate

Chandra Grating Instrument Properties

FWHM ~ 5x102 km/s

Sample of normal disk galaxies

GalaxyName

HubbleType

D(Mpc)

Incl. ang.(deg)

Exp. Time (ks)

N4244 Sd/LSB 3.6 85 60

N4631 Sd 7.5 85 60

N3556 Sc 14.1 80 60

N4565 Sb 13.4 87 60

N4594 Sa 8.9 84 19

All with low Galactic foreground absorption (NH < 3 x 1020 cm-2)