What is getting in and/or out of nearby disk galaxies?
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What is getting in and/or out of
nearby disk galaxies?
Q. Daniel Wang
University of Massachusetts
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The galaxy evolution context
Toft et al. (2002); Muller & Bullock (2004)
The “overcooling” problem: Too much condensation to be consistent with observations
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ROSAT X-ray All-sky ¾-keV Diffuse Background Map
X-ray binary~50% of the background is thermal and local (z < 0.01)The rest is mostly from AGNs (McCammon et al. 2002)
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New Tool: Chandra
CCD:
•Resolution res. ~ 1”
•Spectral Res. E/E ~ 20
Grating:
•Spectral Res. ~ 500 km/s
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Absorption Sight Lines
X-ray binaryROSAT all-sky
survey in the ¾-keV band
X-ray binaryAGN
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LMXB X1820-303
Fe XVII K
• In GC NGC 6624– l, b = 2o.8, -8o
– Distance = 7.6 kpc 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 2006, Yao et al. 2006
LETG+HETG spectrum
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Absorption line diagnostics
Assuming CIE and solar abundances
I()=Ic() exp[-()]
()NHfafi(T)flu(,0,b)
b=(2kT/mi+2)1/2
Accounting for linesaturation and
multiple line detections
Yao & Wang 2005
OVI
OVIIIOVII
Ne IX
Ne VIII
Ne X
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X1820-303: Results• Hot gas accounts for ~ 6% of the total O column density• O abundance:
– 0.3 (0.2-0.6) solar in neutral atomic gas– 2.0 (0.8-3.6) solar in ionized gas
• Ne/O =1.4(0.9-2.1) solar (90% confidence)• Fe/Ne = 0.9(0.4-2.0) solar • Filling factor (relative to total ionized gas):
~0.95, if ph ~ pw
~0.8, if ph ~ 5pw as in the solar neighborhood• Mean temperature LogT(k) = 6.34 (6.29-6.41)• Velocity dispersion 255 (165–369) km/s
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Mrk 421 (Yao & Wang 2006)
OVI 1032 A
•Joint-fit with the absorption lines with the OVII and OVIII line emission data from McCammon et al. (2002)•n=n0e-z/hn; T=T0e-z/hT
n=n0(T/T0), =hT/hn, L=hn/sin b
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LMC X-3 as a distance marker
• BH X-ray binary, typically in a high/soft state
• Roche lobe accretion• 50 kpc away
• Vs = +310 km/s
• Away from the LMC main body
H image Wang et al. 2005
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LMC X-3: absorption linesOVII
Ne IX
The EWs are about the same as those seen in AGN spectra!
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Global distribution models
Combining all the sight lines together:
• Disk modelnH = 5.0x10-3 cm-3 exp[-|z|/1.1 kpc]
Total NH~1.6 x1019 cm-2
• Sphere modelnH = 6.1x10-2 cm-3 exp[-R/2.7 kpc]
~3 x 10-3 cm-3 at the Sun
Total NH~6.1 x1019 cm-2
MH~7.5(2.5-16)x108 Msun
X-ray absorption is primarily around the Galactic disk and the bulge within a few kpc! Yao & Wang (2005)
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Global hot gas properties• Non-isothermal:
– mean T ~ 106.3 K toward the inner region– ~ 106.1 K at solar neighborhood
• Consistent with solar abundance ratios• Velocity dispersion from ~200 km/s to 80 km/s• A thick Galactic disk with a scale height 1-2 kpc, ~ the values of OVI absorbers and free electrons • No significant X-ray absorption beyond the LMC (~< 1019 cm-2, assuming the solar abundance)
But a large-scale gaseous halo required for– The confinement of HVCs– Ram-pressure stripping– Interfaces at intermediate T
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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 energy
Wang et al. 2004
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NGC 2841 (Sb)
Red: optical
Blue: 0.3-1.5 keV diffuse emission
• D=15 Mpc• Low SF rate
• Lx ~ 7 x 1039 ergs/s
Wang 2006
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NGC 4565 (Sb)
William McLaughlin (ARGO Cooperative Observatory)
Red – optical
Green – 0.3-1.5 keV band
Blue – 1.5-7 keV band
Wang (2006)
Very low specific SFR
No sign for any outflows from the disk in radio and optical
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NGC 4594 (Sa)
Red: near-IR
Green: 0.3-1.5 keV
Blue: 1.5-7 keV
H ring
Li et al. 2006
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NGC 4594Point source
Inner bulge
Outer bulge
disk
•Average T ~ 6 x 106 K
•Strong Fe–L complex
•Lx ~ 4 x 1039 erg/s, or ~ 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 from evolving stars ~ 1.3 Msun/yr
•Each Type Ia SN 0.7 Msun Fe
NGC 4631
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XMM/Newton observation of NGC 2613
(Sb, D=26 Mpc, Vc=304 km/s)
0.5-2 keV band; Li et al. (2006)
Similar results from NGC 5746 (Vc=250 km/s, Petersen et al. 2005)
Toft et al.
Stellar light
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Extraplanar hot gas seen in nearby galaxies
• 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
• No evidence for large-scale X-ray-emitting galactic halos
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Observations vs. simulations
• Little evidence for X-ray emission or absorption from IGM accretion.
No “overcooling” problem?
• Missing stellar energy feedback, at least in early-type spirals. Where does the energy go?
Toft et al. (2003)
NGC 4565NGC 4594
NGC 2613
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Galactic bulge simulation• Parallel, adaptive mesh
refinement FLASH code• Finest refinement in one
octant down to 6 pc• Stellar mass injection and
SNe, following stellar light • SN rate ~ 4x10-4 /yr• Mass injection rate ~0.1
Msun/yr)
10x10x10 kpc3 box
density distribution
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Galactic bulge simulation• Parallel, adaptive mesh
refinement FLASH code• Finest refinement in one
octant down to 6 pc• Stellar mass injection and
SNe, following stellar light • SN rate ~ 4x10-4 /yr• Mass injection rate ~0.03
Msun/yr)
3x3x3 kpc3 box
density distribution
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Galactic bulge simulation:• Ejecta dominate the high-
T emission• Not well-mixed with the
ambient medium• Probably cool too fast to
be mixed with the medium
SN ejecta
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Comparison with the 1-D solution
• The average radial density and temperature distributions are similar to the 1-D model.
• Large dispersion, particularly in the hot Fe distribution– enhanced emission at
both low and high temperatures
Log(T(K))
Low Res.
High
Res.
1-D
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Where is the energy?
• Radiative cooling is not important in the bulge region, consistent with the observation
• Energy not dissipated locally
• Most of the energy is in the bulk motion and in waves
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The fate of the energy
• Maybe eventually damped by cooling gas in the galactic hot halo.
• Galactic wind not necessary, depending the galaxy mass and IGM environment.
• Interaction with the infalling IGM a possible solution to the over-cooling problem.
kpc
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Conclusions and Speculations
• Diffuse X-ray-emitting gas is strongly concentrated toward galactic disks and bulges. No evidence for large-scale halos on scales > ~ 20 kpc.
• Heating is most likely due to SNe. But the bulk of the SN energy is not detected and is probably propagated into the halo, balancing the cooling.
• Thermal and metallicity inhomogneities in the IGM naturally lead to its selective coolingHigh velocity clouds OVI absorbers, etc. Low metallicity and high T the radiatively inefficient
hot halo.