recent chandra observations of the galactic center
DESCRIPTION
Recent Chandra Observations of The Galactic Center. Observations: Large-scale mapping 360 ks (Wang, Gotthelf, & Lang 2002) new 600 ks (Muno et al.) Pointed 100 ks each for Sgr B (Koyama et al.) and Sgr C 50 ks for the Radio Arc (Yusef-Zadeh et al. 2002) - PowerPoint PPT PresentationTRANSCRIPT
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Recent Chandra Observations ofThe Galactic Center
Observations:• Large-scale mapping
– 360 ks (Wang, Gotthelf, & Lang 2002)– new 600 ks (Muno et al.)
• Pointed – 100 ks each for Sgr B (Koyama et al.) and Sgr C– 50 ks for the Radio Arc (Yusef-Zadeh et al. 2002)– 100 ks for Arches cluster (Wang et al. 2006) – ~ 1 Ms for Sgr A (Baganoff et al. )
Qingde Daniel Wang
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X-ray Sources
Wang et al. (2002); Muno et al. (2006)
2o
0.8o
Spatial resolution varies from subarcsecond on axis to a few
arcseconds off-axis
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Discrete X-ray sources: Summary of results
• Discrete sources – ~ 1400 from the large-scale survey– ~ 2400 in the Sgr A* region alone.– LogN-LogS relation is flatter in massive SF regions
• Nature of the sources– Bright ones (Lx > 1036 erg/s): X-ray binaries– Intermediate ones (1036 > Lx > 1033): transient
LMXBs, colliding wind binaries, and young pulsars– Faint ones (1033 > Lx ): active low-mass stars (CVs)
Consistent with existing radio and near-IR IDs or lack of them. Some sources have very hard intrinsic spectra (power law photon index < 1)
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Diffuse X-ray emission: spectrum
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SXV Line
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Fe 6.7-keV line
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Fe 6.4-keV Line
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Diffuse X-ray emission: Summary of results
• Diffuse X-ray Emission– Accounting for ~90% of the emission.– Showing strong He-like and H-like K lines
from Si, S, Ar, Ca, and Fe gas at T ~ 1 – 10 keV.
– Global, but not detailed, correction between 6.4-keV Fe K line and cool dense clouds: reflection of past Sgr A* bursts, low-energy comic rays, and possible NEI plasma.
– Probably largely due to coronally active binaries and CVs (Revnivtsev et al. 2005).
– More quantitative modeling is needed!
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Massive star forming region: Composite Chandra map
Arches
Quintuplet GC
Chandra Intensity:
•1-4 keV
•4-6 keV
•4-9 keV
Wang, Hui, & Lang (2006)
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Massive star forming region:from radio to X-ray
20 cm (Yusef-Zadeh et al. 84)
MSX 24 m (Price et al. 01)
Chandra 1-9 keV (Wang et al. 06)
Arches
Quintuplet GC
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Arches Cluster: brightest X-ray sources in the core
NICMOS image (Figer et al. 99)ACIS-I 1-9 keV
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Arches Cluster: bright X-ray sources in the core
• Remarkably similar thermal spectra
• Metal abundance = 1.8 (1.6-2.6) solar
• L(0.3-8 keV)=(0.5-11) x1033 erg/s
• Late-type WN components
• Likely to be extreme massive colliding wind binaries.
Combined ACIS-I spectrum
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Arches Cluster: diffuse X-ray emission
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Arches Cluster: 6.7-keV line plume
•Elongated and Size ~ 30”
Matches the region with an extinction deficit of Av~10 (Stolte et al. 02)
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Arches Cluster: the 6.4-keV line emission and a CS cloud
• Not due to florescence: no spatial correlation with the CS cloud.
• net too small to be due to a NEI plasma.
• Likely due to low-energy cosmic-ray electrons interacting with the cloud (vr > 120 km/s).
Fe KX-ray or electron
CS data: from OVRO+IRAM
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Arches Cluster:Diffuse X-ray emission
• In the core (r < 0.6 pc)– 6.7-keV line– Steep intensity decline– Probably due to the cluster
wind
• In the outer region – 6.4-keV line– Flat intensity profile– Probably due to the low-
energy cosmic-ray electrons --- a result of the collision of the cluster wind with the CS cloud
Radial intensity profile
cluster wind (Rockefeller et al. 05)
NICMOS
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Arches cluster: Constraints on the IMF
•YSOs (0.3-3 Msun) accounts for 75% of the Orion nebula Lx.
•Each YSO has Lx ~ 1.2 x1030 erg/s per star (2-8 keV).
•The observed total diffuse X-ray Lx ~ 2 x1034 erg/s (r < 2.5 pc) an upper limit of 2x104 YSOs.
•Miller & Scalo IMF overpredicts YSOs by > 10
•Power law with Γ~ -0.86 is consistent with the upper limit.
MF for r < 0.4 pc (Stolte et al. 05)
Miller & Scalo IMF
PL MF
X-ray limit
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Quintuplet cluster: X-ray sources
•Dimmer and diverse in spectral propertie
•Some maybe embedded in dusty winds Wang et al. (2006)
Law & Yusef-Zadeh (2004)
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Quintuplet cluster: Diffuse X-ray emission
• Very weak (Lx ~ 2 x1033 erg/s)
• Cluster wind contribution is small
• Follows approximately the stellar distribution
• Probably mostly due to ~2x103 YSOs.
cluster wind (Rockefeller et al. 2005)
NICMOS
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Galactic Center: inner pc region
VLT SINFONI near-IR
(Eisenharer et al. 05)
ACIS-I 1-9 keV
(Wang, Lu, Gotthelf 06; see also Baganoff et al. 03)
Sgr A*IRS 13
PWN?
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Comparison with other extended X-ray-emitting features
Sgr A*
IRS 13
PWN
Diffuse
The spectra of Sgr A*, IRS 13, and diffuse X-ray emission all show the Fe K line at ~6.6 keV NEI emission from gas heated recently (net~103 cm-3 yr).
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A PWN within 1 ly of Sgr A*?
Red: radio (3.6 cm, Roberts & Goss 93)Green: near-IR (Eisenhauer et al. 05)Blue: X-ray (4-9 keV)
Sgr A*
IRS 13
PWN?
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Evidence for the PWN
Pulsar wind nebula• Nonthermal point-like
source (putative pulsar)• Comet-like shape: ram-
pressure confinement• Spectral steepening with
off-source distance• Inverse-Compton scattering
of the ambient radiation, a natural explanation of the TeV emission from the GC.
Shock into SN ejecta
Does the pulsar origin in the GC cluster?What effect on the GC environment?
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Conclusions• About 4000 X-ray sources are detected within
0.8x2 deg2 GC region.• IDs have been difficult, but will be easier with
improved source position accuracy (<1”). • Some of the X-ray sources are likely to be young
pulsars and extreme colliding wind massive binaries.
• Bulk of faint sources are due to low-mass old stars.
• X-ray-inferred Fe abundance is ~ 2 x solar.• Limits on # of YSOs indicate top-heavy IMFs of
young clusters.• Collisions between young clusters and molecular
clouds may be important in star formation.
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M31
NASA/UMass/Z.Li & Q.D.Wang
28’x28’ FoV
Red: 0.5-1 keVGreen: 1-2 keV Blue: 2-4 keV)
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M31 Bulge
Red: 0.5-1 keVGreen: 1-2 keV Blue: 2-4 keV)
Red: Mid-IR (Spitzer)Green: 0.5-2 keV)Blue: 2-4 keV
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M31 Nuclear Region
X-ray images: (NASA/SAO/CXC/M.Garcia et al.)Optical Contours: (NASA/GSFC/T.Brown et al.)
10 ly
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